Types of wear and damage to the body

The main causes of wear and damage to bodies

Body wear and damage can be caused by various reasons. Depending on the cause of the malfunction, they are divided into operational, structural, technological and arising from improper storage and care of the body.

During operation, the elements and assemblies of the body experience dynamic stress from bending in the vertical plane and twisting, loads from their own weight, the mass of cargo and passengers. The wear of the body and its components is also facilitated by significant stresses that arise as a result of body vibrations not only when it moves over irregularities and possible jolts and impacts when hitting these irregularities, but also due to engine operation and errors in balancing the rotating components of the vehicle chassis (in particular cardan shafts), as well as as a result of displacement of the center of gravity in the longitudinal and transverse directions.

Loads can be absorbed by the body completely if the vehicle does not have a chassis frame, or partially when the body is installed on the frame.

Studies have shown that variable voltages act on body elements during vehicle operation. These stresses cause fatigue accumulation and lead to fatigue failure. Fatigue failures begin in the area of ​​stress accumulation.

There are two main groups of damages and malfunctions in the bodies of cars arriving for overhaul:

damage resulting from the growth of changes in the condition of the body. These include natural wear and tear that occurs during normal technical operation of the vehicle due to constant or periodic exposure to the body of such factors as corrosion, friction, decay of wooden parts, elastic and plastic deformation, etc.;

malfunctions, the appearance of which is associated with human action and are the result of design flaws, factory imperfections, violations of body care standards and rules of technical operation (including emergency), poor-quality body repair.

In addition to normal physical wear and tear, when operating a car in difficult conditions or as a result of violation of maintenance and prevention standards, accelerated wear and tear can occur, as well as destruction of individual parts of the body.

Typical types of wear and damage to the body during vehicle operation are metal corrosion that occurs on the surface of the body under the influence of chemical or electromechanical influences; violation of the density of riveted and welded joints, cracks and breaks; deformation (dents, distortions, deflections, warpage, bulges).

Corrosion is the main type of wear on the metal body of the body. In metal body parts, the most common type of electrochemical corrosion occurs, in which the metal interacts with an electrolyte solution adsorbed from the air, and which appears as a result of both direct ingress of moisture on the unprotected metal surfaces of the body, and as a result of the formation of condensate in its inter-sheathing space ( between the inner and outer panels of doors, sides, roof, etc.). Corrosion develops especially strongly in places that are difficult to inspect and clean in small gaps, as well as in flanges and bends of edges, where moisture that periodically gets into them can persist for a long time.

So, in the wheel arches, dirt, salt and moisture can collect, stimulating the development of corrosion; the underbody is not sufficiently resistant to corrosion factors. The corrosion rate is greatly influenced by the composition of the atmosphere, its contamination with various impurities (emissions from industrial enterprises, such as sulfur dioxide formed as a result of fuel combustion; ammonium chloride that enters the atmosphere due to the evaporation of seas and oceans; particulate matter in the form of dust), and also the ambient temperature, etc. Solid particles contained in the atmosphere or falling on the surface of the body from the roadbed also cause abrasive wear of the metal surface of the body. As the temperature rises, the corrosion rate increases (especially in the presence of aggressive impurities and moisture content in the atmosphere).

Winter road surfaces with salt to remove snow and ice, as well as vehicle operation on the seashore, lead to increased vehicle corrosion.

Corrosion damage in the body also occurs as a result of contact of steel parts with parts made of some other materials (duralumin, rubbers containing sulfur compounds, plastic based on phenolic resins, and others, as well as as a result of metal contact with parts made of very wet lumber containing a noticeable amount of organic acids (formic, etc.).

Thus, studies have shown that upon contact of steel with poly-isobutylene, the rate of metal corrosion per day is 20 mg / m2, and upon contact of the same steel with silicone rubber - 321 mg / m2 per day. This type of corrosion is observed in the places where various rubber seals are installed, in the places where chrome-plated decorative parts (headlight rims, etc.) adjoin the body.

The appearance of corrosion on the surface of body parts is also caused by contact friction, which occurs with the simultaneous action of a corrosive environment and friction, with the vibrational movement of two metal surfaces relative to each other in a corrosive environment. This type of corrosion is susceptible to doors around the perimeter, fenders in the places where they are attached to the body with bolts and other metal parts of the body.

When painting cars, the surfaces of the body, carefully prepared for painting, can be contaminated with wet hands and polluted air. This, with insufficient quality coating, also leads to body corrosion.

The process of corrosion of bodies occurs either uniformly over a large area (surface corrosion), or erosion goes into the thickness of the metal, forming deep local destruction - shells, spots at individual points of the metal surface (pitting corrosion).

Continuous corrosion is less dangerous than local, which leads to the destruction of metal parts of the body, their loss of strength, to a sharp decrease in the corrosion fatigue limit and to corrosion brittleness characteristic of the body lining.

Depending on the operating conditions conducive to corrosion, body parts and assemblies can be subdivided into those having open surfaces facing the roadbed (bottom of the floor, fenders, wheel arches, door sills, bottom of the radiator lining), into having surfaces that are located in within the volume of the body (frame, trunk, top of the floor), and on surfaces that form a closed isolated volume (hidden parts of the frame, bottom of the outer door cladding, etc.).

Cracks in the body occur on impact due to a violation of the metal processing technology of the body (shock multiple processing of steel in a cold state), poor assembly quality during the manufacture or repair of the body (significant mechanical forces when joining parts), as a result of the use of low quality steel, the influence of metal fatigue and corrosion followed by mechanical stress, assembly defects of assemblies and parts, as well as insufficiently strong assembly structure. Cracks can form in any part or part of a metal enclosure, but most often in areas subject to vibration.

Rice. 26. Damage found in the back of the car GAZ-24 "Volga":
1 - cracks on the mudguard; 2 - violation of the welded joint of the strut or splash guard with the frame side member; 3 - cracks in the spacer; 4 - cracks on the front panel and front wheel mudguards; 5 cracks in the pillars of the windshield; 6 - deep dents on the pillar panel of the wind window; 7 - skew of the wind window opening; 8 - separation of the front seat bracket; 9 - cracks on the body base casing; 10 - violation of welded joints of body parts; 11 - curvature of the gutter; 12 - dents on the outer panels, covered with parts from the inside, irregularities left after straightening or straightening; 13 - local corrosion in the lower part of the rear window; 14 - separation of the tail racks at the attachment points or cracks on the racks; 15 and 16 - local corrosion of the trunk lid stream; 17 - separation of the trunk lock bracket; 18 - local corrosion in the rear of the base of the body; 19 - dents on the lower panel of the tailgate at the points of attachment of the rear lights; 20 - local corrosion in the lower part of the mudguard; 21 - corrosion deposits and other minor mechanical damage; 22 - local corrosion of the wheel arch; 23 - curvature of the rear wing mudguard; 24 - violation of the welded seam in the joint of the mudguard with the arch; 25, 32 - cracks in the base at the seat attachment points; 26 - Local corrosion on the rear door pillar and on the base of the body. exciting rear spar booster; 27 - cracks on the base of the body at the points of attachment of the brackets of the rear springs and others; 28 — Dents on the pillar panel and bent B-pillar; 29 - separation of the holders of the plates of the retainer and the hinge of the door of the body; 30 - local corrosion in the lower part of the middle pillar of the sidewall; 31 - local corrosion and cracks in the side members of the body base; 33 - distortions of doorways of bodies; 34 - continuous corrosion of the base sills; 35 - dents on the side members of the body base (breaks are possible); 36 - breakdown of the thread on the plates of the retainer and door hinges; 37 - separation of the door lock cover; 38 - dents (possibly with gaps) on the body side panel; 39 - local corrosion in the lower part of the front pillar; 40 - violation of the anti-corrosion coating; 41 - separation of guy-carriers; 42 - the curvature of the cross member No. 1; 43 - cracks on the bulkhead at the strut attachment points; 44 - separation of the bumper front attachment bracket; 45 - cracks on the radiator shield; 46 - local corrosion on the brace of the amplifier; 47 - cracks in the spar attachment points; 48 - loosening of the riveted connection of the bracket; 49 - the development of holes for the spring shackle pin and the front bracket for attaching the rear spring; 50 - separation of the body base spar amplifier; 51 - wear of the shock absorber mounting hole; 52 - cracks in the attachment points of the fuel tank brackets; 53 — Dents with sharp corners or tears on the bottom panel; 54 - continuous corrosion on the lower rear panel; 55 - cracks in the attachment points of the shock absorbers; 56 - cracks in the propeller shaft casing

Destruction of welded joints in nodes, parts of which are connected by spot welding, as well as in solid welded seams of the body, can occur due to poor-quality welding or exposure to corrosion and external forces: body vibration under dynamic loads, uneven distribution of loads during loading and unloading of bodies.

Frictional wear occurs in fittings, hinge pins and holes, upholstery, riveted and bolted holes.

Dents and bulges in the panels, as well as deflections and distortions in the body appear as a result of permanent deformation upon impact or poorly performed work (assembly, repair, etc.).

The concentration of stresses in the joints of individual elements of the body in openings for doors, windows, as well as at the joints of elements of high and low rigidity can cause the destruction of parts if they are not reinforced.

In the structures of the bodies, the necessary rigid connections are usually provided, the reinforcement of individual sections with additional parts, and the extrusion of stiffeners. However, in the process of long-term operation of the body and in the process of its repair, individual weak links in the body body may come to light, which require reinforcement or changes in the design of the units in order to avoid the appearance of secondary breakdowns.

So, when the roof stiffness of the JIA3-695 bus was increased and, as a result, the twist angle decreased, the frames began to break. The breakdowns stopped after the return to the previous roof structure. Thus, structural defects arise as a result of imperfections in the body structure and empennage. Such defects include: insufficiently rigid fastening of parts to each other and to the body frame; incorrectly selected material; insufficient tightness in the joints, which are not allowed to penetrate moisture (window frame of the door, in the joints between the rim of the headlight and the wings, etc.); the presence of "pockets" ot-flanges, allowing the accumulation of moisture and dirt; Insufficiently rigid edges of parts (for example, wings).

Technological defects arise as a result of a violation of the accepted technology for the manufacture or repair of the body. Among the most common technological defects of bodies are poor-quality welding, violation of the quality of the original material, poor-quality performance of certain operations in the manufacture and repair of parts (correcting irregularities in body panels, assembly after repair, etc.).

Below, for example, is a list of damages found in the body of a GAZ-24 "Volga" car (Fig. 26).

Depending on the nature of the damage and how often it occurs, a decision is made on the advisability of pre-manufacturing a repair part (DR) and methods of its manufacture.

General structure of the technological process of body repair

Bodies arriving for overhaul must meet the requirements of the technical conditions for acceptance for overhaul approved by the parent organization.

Car body repair is based on a clear delineation of work on disassembly, repair and assembly of the body and its units in specialized departments, installation on the body, as well as control and adjustment of units in action.

The main document defining the relationship of production operations, their duration, terms of readiness and supply of units and parts, as well as the duration of the entire technological cycle of body repair, should be a network schedule. On the basis of it, a route technology for the movement of parts and assemblies is being developed. These important technical documents guide the development of an in-plant operating plan. According to the routing technology, operational schedules for the repair of parts and assemblies are drawn up in specialized areas: tin, reinforcement, wallpaper, etc. It is possible to ensure a clear organization of work in the areas of repair and assembly of the body only if the specialized areas carry out tasks on time. In this regard, it is necessary to create conditions for a high organization of labor in specialized areas.

The technological process of the overhaul of the body is determined by its design features. In fig. 27 shows a general diagram of the main stages of the body overhaul process, covering individual completed operations. As follows from this diagram, the repair begins with an inspection of the body when accepting it for repair in order to identify the feasibility of repair, check the completeness and detect damage visible without disassembly. Based on the results of the external inspection, the representative of the plant and the customer draw up a bilateral certificate of acceptance of the body for repair, indicating its technical condition and completeness. The act also notes emergency damage, reflects the required additional work that is not provided for by the repair rules. After washing, the body is subjected to preliminary defectoscopy, the purpose of which is to find out the condition and feasibility of repairing units and parts that must be removed from the body (glass, interior upholstery, etc.), so as not to clutter up the production facilities with obviously unusable parts.

Rice. 27. General scheme of the technological process of body repair

After preliminary troubleshooting, a general disassembly of the body is performed. During general disassembly, all units, units and parts installed on the body of the body are disconnected and removed. Only the body shell remains unassembled. When washing the body outside, before disassembling it, the surfaces covered by the inner panels, the floor of the body (in buses), units and parts installed on the body are not washed. Therefore, after the general disassembly and removal of the inner panels and the floor of the bus body, the inner surface and the base of the body are thoroughly washed.

The disassembled and cleaned body, as well as the plumage, is sent to the area for removing old paint; units and assemblies to be repaired in other workshops of the plant or at other enterprises are sent to the unit storage warehouse awaiting repair; fittings, upholstery and other units and body parts requiring repair - to the corresponding specialized departments of the body shop. Unsuitable parts are sent to the scrap warehouse, and the good ones are sent to the warehouse of suitable parts, and from there to the collection.

Repaired and new parts are also delivered to the assembly area, which are installed on the body to replace the rejected parts during disassembly.

After removing the old paint, the body is subjected to careful control, in which the nature of the damage received during its operation and the parts that have exhausted their service life are revealed, and a decision is made on the need and possibility of repair or replacement of one or another body part. The results of the inspection of parts are entered into the defect list. The systematic processing of these lists allows you to obtain data on the coefficients of suitability, repair and replacement of parts during the overhaul of bodies at a given auto repair enterprise. Having these factors makes it easier to draw up realistic recovery plans, parts and logistics. Then the body goes to the repair site. At the first post of this section, the bodies of some structures are subjected to further disassembly, which is necessary to carry out repair operations.

So, metal cladding and damaged wooden parts are removed from bodies of the van type with wooden frames; damaged trusses connected by rivets or bolts, panels, facings, etc. are removed from the bus bodies of the supporting structure.

After the repair, the body is pre-assembled; at the same time, doors are hung on the body, panels, plumage and other parts to be painted along with the body are installed. Then the body is painted and finally assembled.

Schemes of technological processes for repairing bodies of cars, buses and truck cabs differ from each other by the presence of various equipment and mechanisms on them, as well as damages characteristic of each body structure and methods of their elimination.

Body preparation for repair

The preparation of the body for repair is carried out in accordance with the adopted scheme of the technological process of its repair and, as a rule, includes, after external washing and cleaning of the body, disassembling and removing paint and varnish coatings, identifying damage and determining the scope of repair work.

As can be seen from the above diagram of the main stages of body repair, disassembly during its overhaul is carried out in two sequential steps: removing from the body all assemblies and parts installed on its body from the inner and outer sides; disassembly of the case for repair after removing the paintwork and identifying all damage in the case.

The sequence and amount of disassembly depends on the types of bodies, since they have a different number of assemblies and parts, differently installed and reinforced.

The general disassembly of the supporting structure bodies is closely related to the disassembly of the car (bus) as a whole. Some components and parts of the body must be removed before disconnecting the electrical equipment and assemblies of the chassis of the car (bus), and some can be removed only after removing the assemblies. All these features are taken into account when drawing up a technological process for disassembling a car (bus).

The car arriving for repair is transported by means of a tractor and a traction chain from the repair site to the external washing area. The first post of this section provides for the possibility of heating the car in winter. Then the inner upholstery and fuel tanks are removed from the car body and the body is washed. This post is usually equipped with a lift, with the help of which the body is raised to flush its bottom and the units attached to it. After an external wash, the vehicle is transported by means of a traction chain to the disassembly area, where it is installed on a load-carrying conveyor of periodic action. On this conveyor, doors, hood, trunk lid, radiator lining, electrical equipment, buffer, glazing, fittings and other components and parts are removed from the body. To remove the undercarriage units from the body, the car is installed on a rotator (with a small production program, the entire disassembly process is carried out on a rotator).

At some ARZs, the external car wash is carried out after removing the wheels, side doors, fuel tank, interior upholstery, electrical equipment and wiring, trunk lid and muffler from the car.

The seat cushions and backrests removed from the body, as well as seat skeletons, are delivered by trackless transport to the corresponding repair areas; The plumage and bodies suitable for repair are transferred by means of an overhead conveyor of periodic action to the unit for removing old paint, and the fittings (locks, windows, etc.) are placed in baskets and sent to the fitting and reinforcement section.

Buses LiAZ, LAZ and Ikarus, after external washing, are moved by a traction chain to the disassembly posts. At the first post, the bus is lifted with two-plunger hydraulic lifters, installed on L-shaped racks, which provide the ability to work from below, and chassis assemblies, pipelines and other components and parts located under the floor of the body are removed. Then the body is installed on technological trolleys and moved along the rail track by means of a traction chain to the next disassembly stations. Units and parts removed from the body to be repaired at the enterprise (seat skeletons, seat cushions and backs, glass with frames, body floor, etc.) are subjected to preliminary control, and then sent to the appropriate departments for their repair. After complete disassembly, the bodies are moved to a chamber to remove old paint and thoroughly rinse the inner surface of the body, and then to their repair posts.

When organizing disassembly at specially designated positions, it is possible to: eliminate clutter and reduce contamination in body repair areas at repair positions; equip workplaces with special tools and mechanized devices for removing heavy units and assemblies, as well as equip them, if necessary, with ventilation devices; rationally organize the dismantling process by specialized teams; increase the use of good parts.

Disassembly is carried out mainly using various plumbing universal tools, as well as mechanized wrenches and pneumatic tools. If necessary, gas cutting is used. Therefore, the installation of a disassembled body should provide the maximum scope of work, the possibility of using power tools and equipment, and the minimum time required for auxiliary operations.

In places where dismantling operations are performed, lifting devices (jacks, crane beams, telphers), mechanized mobile carts, as well as pipelines for supplying oxygen and gas during gas cutting operations are provided.

The disassembly process is selected depending on the accepted organization of repairs and local conditions.

With a significant volume of production of bodies from repair, which are repaired on a conveyor, disassembly can also be carried out by the flow-conveyor method.

Parts of detachable body connections are removed with a universal or specialized tool. Details of permanent joints (welded, riveted) should be carefully disconnected in order not to damage them.

The body body for the repair of its parts is disassembled to the extent necessary to ensure the high-quality performance of all repair operations. The all-metal welded body is not disassembled. Defective panels (or parts of panels) are cut out and replaced with new repair parts. Riveted bus bodies can be disassembled into their component parts. To ensure high-quality disassembly of the body and eliminate the possibility of damage to its parts, the disassembly procedure is established by the technological process.

Technological processes for body repair are usually developed in accordance with technical specifications, which contain requirements for the condition of the main components and body parts, acceptable methods for their restoration and the necessary data to control them after repair.

Since it is not known in advance which part in the body body assembly (panel, base girder, etc.) will require repair or replacement, standard flow charts are drawn up for disassembly and repair of all body body parts, the possibility of damage to which is revealed by analyzing a large number of similar bodies received in overhaul, according to the lists of defects, which are drawn up during the troubleshooting of the body.

The preliminary disassembly of the body is usually performed at the car (bus) disassembly stations, and the disassembly of the body, associated with the removal and repair of damaged parts of its body, is performed at the appropriate repair sites. In this case, the body is installed in a position convenient for repair and measures are taken to protect it from its own weight load, which can cause deformation and distortion of its geometric parameters. Violation of the hermetic dimensions of the body can also occur when removing some of its units and parts on which other body units rest (when replacing sidewall panels and B-pillars on the body of a car, removing the outer lining of the sides of the body of some buses), if appropriate precautions are not taken ... Therefore, before removing the supporting units of the frame, fixing devices (special spacers, conductors) are installed in the body openings, which hold the units that have lost their support in their normal position.

An example of a method for fixing the upper part of the tailgate is shown in Fig. 28.

Rice. 28. Method of fixing the upper panels of the rear part of the body when removing the lower destroyed parts

The device rests with one side against the right sidewall and the floor of the body, and with its opposite upper part is attached with two technological bolts to the corner panel of the body, thus fixing the correct position of the upper rear panels in width. The height position of these panels is fixed by a stretching device. At the end of the repair, the holes for the technological bolts are welded, and the weld beads are cleaned.

Methods for removing paint and varnish coatings and cleaning the surface of the body from corrosion products

Old paint can be removed mechanically using a sandblasting (shot blasting) apparatus or a mechanized hand tool, or chemically - by treatment with special washes or alkaline solutions.

Mechanical removal of paintwork simultaneously removes rust and scale that may have remained on the body panels or empennage of the car after welding during current repairs. Mechanical cleaning is advisable to carry out after degreasing. Failure to comply with these recommendations leads to a decrease in the efficiency of the process and the quality of cleaning and to premature wear of the processing material.

During shot blasting, the surface becomes rough, which ensures good adhesion of the paint film to the metal. The most common abrasive used for blasting metal surfaces is metal sand. In recent years, the search for new materials, cheaper and more technologically advanced, has begun abroad. Of the tested, natural mineral materials are considered promising (crushed rocks, natural corundum, zirconium eluvial sand with rounded grains), as well as artificial materials (electrocorundum, silicon carbide, etc.).

The main trends in the field of mechanical cleaning are process automation and combination with chemical action. For the finishing of large surfaces, abrasive belts and rotary brush-type devices, working according to a given program, began to be used. Polyester materials containing small (- 0.5 μm) particles of carborundum, aluminum, chromium oxide, etc. have been successfully tested as abrasives.

Studies have shown the influence of technological factors of shot blasting (initial state of the treated surface, grain size and shape, hardness of abrasive material, duration of treatment) and microgeometry of the treated surface on the properties and strength of its adhesion to protective coatings. Maximum roughness is necessary to ensure good adhesion of sprayed metal and non-metal coatings with a large layer thickness, especially powder. However, to obtain coatings with high protective properties and reduce the consumption of materials, the roughness value should not be more than 30-40 microns, and the thickness of the applied layer should exceed the maximum profile depth. Some authors suggest a two-stage treatment: coarse sand for cleaning and fine sand for leveling the profile.

The relief is significantly influenced not only by the initial shape of the grains, but also by the shape of their fragments, as well as the ability of the latter to maintain sharp edges.

It is recommended to use DChK-type metal shot produced by factories of our industry with a grain size of 0.2-0.3 mm as an abrasive substance when cleaning the body. The use of pellets with spherical surfaces and loose edges should be avoided, since the edges of such pellets break off and remain on the metal when hitting the metal, which deteriorates the appearance and quality of the coating applied to the body. To clean the body panels and empennage, made of sheet steel up to 1 mm thick, from old paint and obtain the necessary roughness, the optimal angle of inclination of the shot jet to the treated surface should be 45 °, and the air pressure should be 2-3 kgf / cm2.

As a result of studies carried out at the Volzhsky Automobile Plant with the participation of the Magnitogorsk Mining and Metallurgical Institute and NIIATM of the resistance of the coating of steel sheet with various roughness parameters, it was found that the properties of the coating are influenced by such indicators as anisotropy, roughness inhomogeneity and the degree of filling the rough layer with metal. At the same time, it was found that a dense fine-crystalline structure of the phosphate layer, determined by a high crystallization rate, is formed only on a loose rough layer (KP = 0.35-0.45) at any Ra and n0 *. In addition, it was found that the uniformity of roughness and the absence of anisotropy have a beneficial effect on the physicochemical properties of a complex paint and varnish coating. Defects of the "shagreen" type were observed only at a large roughness of 2.2 µm. With a decrease in the inhomogeneity of the distribution of parameters and anisotropy of roughness, the inhomogeneity in thickness decreased, the gloss and appearance of the complex coating improved. Thus, the structure of the rough layer of the metal surface significantly affects the physicochemical and mechanical properties of the complex paint and varnish coating. The roughness of the surface of the body panels to be painted can be limited to 4-5 cleanliness classes 2 = 20h-40 microns.

Sand can be supplied with a sandblasting (shot blasting) apparatus, but it is best to use for this purpose a mobile dustless apparatus of the AD-1 type developed and produced by the domestic industry (Fig. 29) and a hand-held shot-blasting gun (Fig. 30).

These devices provide for automatic regeneration of abrasive shot and its supply to the shot blasting machine. Therefore, the advantage of such devices is the ability to reuse the abrasive, the absence of dust and does not require the construction of special ventilation devices. Metal shot is thrown onto the surface to be cleaned with compressed air through a nozzle. After hitting the surface, the shot, together with the formed cleaning products, is sucked by an injection device into the vacuum channel surrounding the nozzle, separated and used again.

Rice. 29. Shot-blasting dust-free apparatus AD-1

Rice. 30. Manual shot blasting dust-free gun

Rice. 31. Shotblasting chamber for cleaning the inner surfaces of the car body

Shot-blasting can also be performed in a special chamber similar to that used at the Novorossiysk Carriage Repair Plant. The chamber is a closed metal hangar (Fig. 31), inside of which shot-blasting machines are installed on sites along the longitudinal walls. The devices are equipped with hoses that are manually led to the cleaned surfaces.

The spent shot is poured into bunkers, from where it is taken by elevators, rises and after separation enters the upper bins. From these hoppers, the shot is loaded into blast machines for reuse. The removal of shot from the floor of the horizontal elements of the body frame is carried out through the hose of a mobile suction unit mounted inside the chamber.

The separation of the shot, that is, the removal of its crushed particles and cleaning products, is carried out using a fan, which is connected to the elevators by a central exhaust channel and side nozzles.

Contaminated air is discharged from the chamber by two fans through pipelines through ventilation openings in the windows. All three exhaust air ducts are equipped with cyclones. The inflow of heated fresh air is provided by a ventilation unit.

Various installations are used to remove corrosion products manually by mechanical means. Of these installations, of interest is the needle cutter, which is a micro-cutter with several thousand cutting edges. A needle cutter is made of straight sections of high-strength wire with a certain packing density. The filling factor of the space on the working surface is 40-85%. Each villi, pinched at one end by a welded seam and clamped with a certain force between similar villi, is a kind of semi-rigid incisor. Such a tool can cut a layer of rust, scale, metal 0.01 - 1 mm thick, rotating in any direction at different angles to the axis of rotation. One of the features of the needle cutter is the ability to create a predetermined roughness on the metal surface. This improves adhesion to the protected surface. The advantages of cleaning with this tool also include the absence of dust and the noiselessness of the process. The service life of the needle cutter is 200-300 hours of continuous operation (and of ordinary steel brushes 10-12 hours).

Rice. 32. Electromechanical brush:
1 - electric motor; 2 - reducer; 3 metal brush; 4 - flexible shaft; 5 - starter: 6 axis device; 7 - trolley

Of the manual mechanized tools for cleaning surfaces, grinding machines MSh-1, I-144 and devices with a pneumatic drive, grinders LLIP-2, LUP-6, an angle pneumatic machine and an electromechanical brush are also used (Fig. 32). Steel brushes or abrasive wheels are mounted on these devices, with the help of which cleaning is carried out. The electric motor is attached to the bogie 7 by means of an axial device 6 that allows the electric motor to rotate about a vertical axis. The mass of the device is about 16 kg.

For mechanization of surface cleaning and removal of paint and varnish coatings, disk brushes are also widely used (for working heads for pneumatic drills) (Fig. 33).

In the case of using a hand-held power tool or a shot blasting machine that does not suck off dust, it is necessary to provide adequate ventilation of the room to remove the resulting dust. The study found that mechanical surface preparation with manual metal brushes will not provide adequate surface cleanliness, is inefficient and uneconomical. With this cleaning method, numerous scratches and notches appear on the treated surface. The best quality and most economical surface preparation is provided by sandblasting (using metal sand).

Rice. 33. Disk brush for working heads for pneumatic drills:
1 - roller; 2 - flange; 3 - ring for fastening the pile; 4 - pile made from strands of steel cable; 5 - clamping screw

For chemical removal of coatings and synthetic enamels, various washes are used.

The Leningrad branch of the GPI Lakokraspokrytie has developed thixotropic washes SPS-1 and SPS-2, the advantage of which over other washes produced by the domestic industry is their reduced toxicity. The SPS-1 wash is non-flammable, and the SPS-2 is flammable, but it has less toxicity than the SPS-1 wash due to the presence of low-toxic solvents in its composition. The flushing effect of the washes SPS-1 and SPS-2 is better in comparison with the washes currently produced by the domestic industry, as well as with the non-flammable emulsion remover SEU-1, developed by the Research Institute of Paint Coating Technology (NIITLP), designed to remove old paint by immersion of products. Washes can be applied with spatulas or airless sprays. The industrial production of these washes is supposed to be organized at the Riga paint and varnish plant.

PKB Soyuzbytkhima (Vilnius) has developed a car wash for old paint, the advantages of which over the washes produced by the domestic industry are higher efficiency, versatility and manufacturability. The wash is non-combustible and is produced according to TU 6-15-732-72 by the Alytus chemical plant p / o "Litbytkhim" and the Shostka plant of chemical reagents.

ZIL has developed an alkaline composition for quick removal of synthetic enamel paint and varnish coatings from metal surfaces of conveyor suspensions. This composition does not contain toxic and volatile compounds and allows you to mechanize the process - to use the method of immersing products in a bath. Sodium gluconate and ethylene glycol (GOST 19710-74) are used as etching accelerators.

Experience has shown that a solution consisting of 20% sodium hydroxide and 0.5% sodium gluconate (the rest is water), at a temperature of 95-98 ° C, removes a paintwork with a thickness of 60-75 microns in 5 minutes, and with a thickness of 120-150 μm - in 15 minutes. If 8% ethylene glycol is added to this solution, the coatings of the specified thickness are removed in 3 and 5 minutes, respectively. The softened paint is completely removed by rinsing the surface with a jet of hot (50-60 ° C) water.

After removing the old paint with a remover, corrosion remains on the surface of the body and an abrasive tool or chemical treatment methods (etching) are used to remove it.

To remove light corrosion deposits, it is enough to treat the surface with the composition "Dioxidin" (a mixture of an aqueous solution of phosphoric acid, isopril alcohol with the addition of surfactants) or composition No. 1120. However, it is not always possible to completely remove corrosion products from the painted surfaces, especially in hard-to-reach places. In these cases, it is recommended to use the EVA-0112 corrosion converter soil, produced by the Zagorsk paint and varnish plant according to TU 6-10-1234-72. Corroded surfaces with a layer thickness of up to 100 microns are treated with this soil, which significantly reduces the labor intensity of work, improves the quality of the coating.

Before applying the primer, a thick (loose) layer of rust (over 100 microns) is removed mechanically. Primer EVA-0112 is prepared immediately before use by mixing the base and the hardener, which is 85% orthophosphoric acid in a ratio of 3 parts of orthophosphoric acid per 100 parts of the base.

According to GOSNITI and NIITtraktoroselkhozmash, 3-6 parts by weight of orthophosphoric acid are added to 1 liter of soil with initial viscosity (depending on the amount of corrosion products on the surface of the parts). After manufacturing, the primer is diluted with water (condensate) to a working viscosity of 26-27 s according to VZ-4. The primer is applied by spraying with a layer thickness of 25-30 microns. Drying time of the coating at 18-23 ° C is 24 hours, and at 50-60 ° C - 20 minutes. The consumption of the primer is about 300 g / m2 (on the metal surface covered with the EVA-0112 primer, you can apply the primer GF-020, GF-019 or FL-OZk, as well as pentaphthalic enamels).

To mechanize the process of removing old paint from cabins and plumage of GAZ-bZA and ZIL-130 trucks, the Giproavtotrans Institute has developed a unit that consists of four sections sequentially arranged one after another: removing old paint, washing with hot water, passivation and a device for blowing hot air. Between the above-mentioned compartments, there are drainage sections, through which the working fluid flows back into the compartment baths. Each of the compartments is a welded structure sheathed with sheets, the space between which is filled with heat-insulating material. In the upper part of the compartments, an overhead conveyor path is fixed, on which the products are subjected to blasting.

The working fluid is heated by means of coils through which steam passes. The unit provides for the possibility of pumping water from the hot water washing compartment to the old paint compartment, as well as from the cold water washing compartment to the neutralization compartment for its reuse. To adjust the concentration of working fluids and maintain a certain level in the compartments, there are appropriate automation equipment.

To prevent the ingress of harmful vapors into the production premises, the unit has an automatic ventilation system, the exhaust diffusers of which are located in front of the wash shower in the old paint removal compartment and after the wash shower in the cold water wash compartment. Between the wash showers of the compartments, there are double-sided drainage zones, which exclude the possibility of mixing the working fluids.

At the end of the process of removing the old paint, the products are dried with hot air supplied from both sides of the product. To fully automate this process of removing old paint from the cab and plumage, a double-chain batch conveyor is provided in the designs of units installed at some ARZs (Voronezh, Lvov). The cabins and empennage are fed to the installation on a trolley with a lifting table and are suspended on suspensions from the supporting part of the double-chain conveyor. Then the conveyor moves the suspended load horizontally, and vertically downward above the bathtub, immersing it in an alkali solution. After submersion of the cab, the conveyor turns off, and at the end of the cycle of work, the conveyor turns on again. Cabins (plumage, body) rise from the bath vertically upward and move to the next bath, etc. The entire process of removing old paint in this installation is automated and takes 30 minutes.

Cleaning the bodies of dump trucks from rocks adhered to them is carried out by mechanical means of action (pneumatic chisels and other devices) or by a hydraulic method using a water jet installation similar to a high-pressure installation for external washing of heavy-duty vehicles developed by the Design Bureau of Glavenergo-Stroymekhanizatsiya. This installation is stationary, straight-through, semi-automatic. The washing device is a rocking monitor with a remote control and a swing angle in the horizontal plane + 45 ° and vertical plane + 30 ° and with a vertical movement from the floor level from 0.8 to 2.4 m. The diameter of the monitor opening is 20 mm. The washing liquid is supplied by a centrifugal pump with a capacity of 80-150 m3 / h. The power of the pump electric motor is 55 kW. The return of the re-water is carried out by a sand pump with a productivity of 54 m3 / h. Water purification is carried out by pressurized and open upper hydrocyclones, the volume of which is 40 m3. The cleaning agent is hot water (70-85 °), the consumption of which is 4 m3 / day. The detergent is heated with steam, the temperature of which is 120-130 ° C. Steam consumption 125 kg / h. The total power of the installation is 75 kW.

Body inspection

Body inspection is an important part of the repair process. After removing the old paint, the body is subjected to careful control in order to reject unusable parts, select suitable ones, and determine the type and amount of repair work. Flaw detection of the body and its components is carried out in accordance with the technical conditions for its repair, developed for each type of vehicle. The quality of the repair largely depends on the accepted method of fault detection and the thoroughness of its implementation.

Flaw detection of the body and its parts is organized in the areas of general disassembly of the body and in the areas of its repair. To detect defects in the body of the body, as well as to control newly manufactured parts: welded seams, non-destructive testing methods are used.

The technical condition of the body at auto repair plants is usually checked by external inspection of the surface of the parts with the naked eye or using the simplest magnifying glasses of multiple magnification. Usually, for this purpose, four- or nine-fold binocular loupes are used. This method allows you to detect surface cracks, corrosion corrosion, deformations, etc. Measurement with special measuring tools, fixtures and templates allows you to detect the deviation of the geometric dimensions of parts from the original (distortions, deflections, etc.).

To detect cracks and determine the tightness of fit of articulated parts, the method of tapping parts is also used, which is based on determining the tone of sound when parts are tapped with a hammer. Cracks and loose connections (rivets, bolts, spot welding, etc.) can be identified by changing the tone of the sound. The effectiveness of this method depends on the experience of the performer.

However, an external examination can only establish large, visible damage, for example, dents, broken shapes, areas of surface corrosion, cracks, etc. In some places of the load-bearing body elements as a result of the accumulation of fatigue and significant hardening of the metal due to work hardening that appeared during repeated repairs of panels , hairline cracks appear, which can be detected by special methods.

Methods based on the molecular properties of a liquid are called capillary methods (methods of penetrating liquids), based on the capillary penetration of indicator liquids into the cavity of surface defects and registration of the indicator pattern. The most widespread are the small kerosene color and luminescent methods. Kerosene, having good wettability and surface tension, easily penetrates into leaks.

The essence of this method is that the inspected place is moistened with kerosene and wiped dry or dried with a stream of air. Then this place is covered with an aqueous solution of chalk. At sub-zero temperatures, a non-freezing solvent (0.5 l of ethyl alcohol per 1 l of water) is added to the solution. Due to the absorption of kerosene by the chalk, a grease trail appears on the chalk surface, which is used to judge the size of the crack.

With color control, the inspected area is thoroughly cleaned and degreased with gasoline, and then covered with a solution of penetrating red paint. After holding for 5-10 minutes, the solution is removed from the surface with water or with a solvent (depending on the used defectoscopic materials).

After cleaning the surface of the part, a layer of white developing mixture is applied to it by spraying or with a soft brush. After 15-20 minutes, characteristic bright stripes or spots appear on a white background at the locations of defects. Cracks appear as thin lines, the brightness of which depends on the depth of the cracks. Pores appear in the form of points of various sizes, and intergranular corrosion - in the form of a fine mesh. Very small defects can be observed through a magnifying glass or binocular microscope. At the end of the control, the developing mixture is removed from the surface by wiping the part with a cloth soaked in solvent. The part is dried.

Defectoscopic materials are used in a complete set. The set includes: cleaning composition, indicator (penetrating) paint "D" -M, showing "D" -V. They can be found in ordinary dishes, as well as in aerosol bottles.

Penetrating compositions can be made from lighting kerosene - 70-80 g, gasoline B-70 - 20-30 g, aniline dye or Sudan IV - 1-3 g, and developing from (in percent by weight) white nitroenamel NTs-25 - 70 g, RDV thinner - 20 g, zinc thick-grated white - 10 g.

The paint method can reveal cracks with a width of 0.005 mm and a depth of up to 0.4 mm. When the part is heated to 50-80 ° C, smaller cracks can be detected.

Since car bodies are usually made of thin sheet steel, in order to avoid choosing the wrong repair method (whether to leave the corroded area after removing the corrosion products from its surface and then apply an anti-corrosion coating, or replace the damaged area with a new one) when inspecting the body, the depth of corrosion destruction. For this purpose, it is best to use non-destructive methods of flaw detection, for example, using a gamma thickness gauge (Fig. 34). This device is used to measure the thickness of the steel sheet of the body lining when the object to be measured is accessible only from one side. There are no special requirements for surface cleanliness when measuring with the device.

Rice. 34. Gamma thickness gauge:
1 - measuring unit; 2 - pistol-sensor; 3 - power supply

The operation of the device is based on measuring the intensity of gamma rays (the source of which is cobalt-60), scattered when passing in the opposite direction in the thickness of the metal. The detector in the device is a counter with a crystal of sodium iodide. The pulses from the detector go to the amplifier and then to a single-channel amplitude pulse analyzer, to the output of which an integrating circuit is connected. The readings are read off on the device, the scale of which is graduated in millimeters.

The device allows you to measure sheets with a thickness of 0 to 16 mm. The time required for one measurement does not exceed 30 s. The device is powered from a 220 V AC network.

To determine the depth of corrosion destruction, you can also use some magnetic gauges of the thickness of non-magnetic coatings on ferromagnetic bases (devices MIP-10, VIP-2, etc.).

TO Category: - Car bodies

Car body consists of a base, roof and frame, including struts, spars, cross members, beams and reinforcements to which welded and hinged front parts are attached - plumage. Moreover, all welded body parts (mud flaps, arches, floors, panels, etc.) can be attributed directly to the supporting or reinforcing elements of the body frame.

As a result of an accident, the body may be damaged, traces may appear on its surface deformations, scratches, scuffs and other damage.

Deformation - changing the shape and size of the body(parts, structures) as a result of external influences without changing its mass. The simplest types are stretching, compression, bending, torsion. Deformation is subdivided into superficial (smooth) and deep. As a result superficial deformations are formed dents, bulges. As a result deep deformations are formed folds,

extractions, fractures of the stiffeners, destruction of the integrity of the material or connection with the formation of cracks, ruptures, separation of fragments,

The types of deformations and repairs of car bodies are defined in some detail in the VAZ regulations.

Scratch - it is a trace on the surface that does not disturb the shape of the surface.

Bully- damage leading to the violation of the surface material.

The bodies of modern passenger cars are a complex spatial system designed for high dynamic and static loads. As a load-bearing body, the body perceives loads through the elements of the load-bearing frame, as well as internal and external panels.

Under normal operating conditions, car bodies will reliably serve for 10-12 years or more.

It must be borne in mind that in case of road accidents and when driving at high speeds on broken roads, permanent deformation occurs in the body.

The most damaging body damage occurs when frontal collisions, in case of collisions with the front part of the body at an angle of 40 - 45 ° or from the side. If such collisions occur between two vehicles moving towards each other, then their speeds upon collision add up. In such collisions, to the greatest extent collapses front part car body. Acting at the same time high dynamic loads in longitudinal, transverse and vertical directions transferred to all adjacent frame parts body and especially its power elements and can cause their deformation even from the opposite side.

Let's consider several examples of emergency body deformation.

The blow has been dealt in the front part of the body in the area of ​​the left front fender, side member and left headlight(Fig. I). With this direction of impact, it is most likely that damage will affect following bodywork details:

radiator frame panels, bulkhead, fenders, hood, mudguards, front side members, windshield frame and roof. In the figures, this can be seen from the lines indicated by the dotted line.

The blow was inflicted on the car into the front part of the body at an angle about 40 - 45 ° (Fig. 2.). With this direction of impact, it is most likely that get damaged following bodywork details:

front fenders, hood, radiator frame panel, bulkhead, mudguard, front spars.

It is possible to restore the base points of the front part of the body using straightening methods. At the same time, it is also necessary to restore the dimensions along the openings of the front doors and the coordinates of the front and central pillars, since the power loads were transmitted through the front doors to the front and central pillars of the body, they acted with compressive forces on the threshold and the upper part of the body sidewall.

Fig. 2. Damage to the body when hitting the front at an angle of 40-45 °.

The impact was made from the side to the front part of the car body in the area of ​​the interface of the front panel with the front part of the side member and the left wing (Fig. 3). With this direction of impact, it is most likely that damage will affect following bodywork details:

front fenders, radiator frame, bulkhead, mudguards, side members, hood. Tensile forces violated the opening of the left front door, compressive forces caused deformation in the opening of the right door and in the sidewall of the left front door. At the same time, the front and center struts also received significant power overloads and have deviations from their original location.

Fig. 3. Damage to the body in a side impact in the area of ​​interface between the front panel and the side member.

Impact - from the side to the front pillar of the car body on the left side(Fig. 4). With this direction of impact, it is most likely that get damaged following bodywork details: .

left A-pillar, windshield frame, roof, floor and front side members, radiator frame, bulkhead, hood, fenders, mud flaps and front side members. In this case, the front of the car body "left" to the left; the sill and the upper part of the right sidewall took tensile loads, the B-pillars and C-pillars. - compressive loads; mudguard right "torn" from the front pillar. ...

Technical conditions 017207-255-00232934-2006 "Bodies of LADA cars, technical requirements for acceptance for repair, repair and release from repair by enterprises of the service and sales network of JSC" AvtoVAZ "", Togliatti 2006, provide the following types of repair damaged (deformed) bodies (TU clause 2.6.1.):

elimination of distortions body;

repair individual parts (straightening, welding);

replacement individual body parts or their damaged parts;

coloration and anti-corrosion treatment ".

Body skew - this is violation beyond acceptable limits geometric parameters openings (windows, doors, hood, trunk lid), and the locations of the base attachment points

"Elimination of distortions body (TU clause 2.6.3) is the restoration of the geometric parameters of the openings of windows, doors, hood, trunk lid, side members, interior frame and base points on the base of the body for attaching the power unit, transmission and suspensions. "

The geometric parameters of the bodies are given in the TU (Appendix B). The presence of distortions is established by measuring the corresponding openings or the location of the base attachment points power unit, suspensions (bridges) and transmission units on the base of the monocoque body frame.

3.3. Elimination of distortions openings and bodywork must be carried out before straightening and repair front panels.

3.4. Allowed produce elimination of distortions bodies both with front panels (fenders, sidewalls, front and rear panels, roofs), and with disconnected front panels.

3.6. Depending on the degree of deformation of the body, the following classification of distortions is established:

skewed opening;

uncomplicated body distortion;

body skew of medium complexity;

complex body distortion;

body distortion of particular complexity.

3.7. Depending on the degree of damage or corrosive destruction of the body part, the following are foreseen types of repair with removed units and parts that impede the carrying out of straightening, welding and painting works:

renovation.0- elimination of damage on the front surfaces of the body without damaging the paint;

repair 1- elimination of damage in readily available places (up to 20% of the surface of the part);

repair 2 - elimination of damage with welding or repair 1 on the surface of a part deformed up to 50%;

repair 3 - elimination of damage with opening and welding, partial restoration * details up to 30%;

repair 4 - elimination of damage with partial restoration * details on the surface over 30%;

Partial replacement - replacement of a damaged body part with a repair insert ** (from the range of spare parts or made from the latter); ...

Replacement- replacement of the damaged body part with a part from spare parts ***.

Large block repair- replacement of the damaged part of the body with blocks of parts from rejected bodies with marking, cutting, fitting, drawing, straightening, welding of the latter. "

* Partial restoration of a part- this is the elimination of damage by drawing or straightening, with shrinkage of the metal; cutting out areas that cannot be repaired; production of repair inserts from rejected body parts or sheet metal with giving it the shape of a restored part. "

** Partial replacement most often it is performed when narrow and long parts are damaged (cross members, spars, sidewalls), when it is economically more expedient to replace not the entire part, but only its damaged part.

*** Replacing a part the body is produced in the event of its unrepairability or economic inexpediency of its repair.

Body repair is often associated with the need to perform reinforcement works on disassembly, assembly, removal, installation nodes, details. The list of reinforcement works is given in the technology of maintenance and repair of the corresponding AMTS.

Reinforcement works most often include:

disassembly, assembly:

Front, rear and rear doors;

Removal and installation;

The hood and its mechanisms;

Battery;

Trunk lids and their mechanisms;

Windscreen, rear and side windows;

Rear lights;

Front and rear bumpers;

Antennas, speakers, radio, radio, turntable;

Heater;

Dashboards;

Roof upholstery;

Safety belts;

Sidenev;

Block headlights.

Labor intensity of work on repair (replacement) of body parts and elimination of body distortions, as a rule, do not take into account labor intensity of work on removal and installation of assemblies and parts that impede repair work.

In the laboriousness of replacing body parts taken into account the following works: detachment and removal of the old part, elimination of metal residues, loose and formation rust (corrosion), straightening of mating edges, adjustment and welding of a new part, cleaning of welding points and seams, leveling of surfaces with fillers and grinding of defective places. ("Labor intensity of works on maintenance and repair of VAZ cars" General provisions of clause 9. Togliatti 2005)

Drawing up an inspection report

As a result of examination by a specialist identified and recorded in the relevant sections of the inspection report, all the information necessary for the assessment about the object of assessment, its damage, defects, repair technology, as well as his opinion on the cause of the detected damage.

1. IN IDENTIFICATION the section is entered:

REAL, and not indicated in the submitted documents, numbers a motor vehicle and its components (registration number, VIN identification number, body number, frame number, engine number, etc.);

odometer mileage;

For automatic telephone exchanges that are on warranty service, or which are repaired and serviced by an authorized dealer or a branded workshop, a special confirmation record must be made;

equipment a motor vehicle, the presence of additional, freelance, tuning equipment;

2. To section "INSTALLED DURING INSPECTION" the following information is entered, the correction of which is unacceptable:

was it produced replacement knots, assemblies and expensive components;

has been vehicle body repair earlier and what is its volume, nature and quality;

Availability on a motor vehicle of operational defects, first of all, the presence of metal corrosion (surface, deep or through).

Availability on a motor vehicle of emergency damage (deformations, scratches, scuffs, etc.), their type, nature, degree of complexity, size and location.

Damage can be classified by time of occurrence:

Related to this emergency;

Received from previous accidents.

The specialist conducting the inspection must draw probabilistic conclusions about the belonging of the detected damage to this incident and make an appropriate entry in the Inspection Report of the following nature:

“With a high degree of probability, it can be assumed that the damage to the car found during the inspection may be the result of an accident recorded in the attached Traffic Police Certificate. Damages, about which it can be assumed that they are NOT a consequence of this accident, are marked in the "CONCLUSIONS" section with two asterisks ** "

Defects can be classified as follows:

Obtained as a result of the correct operation and storage of AMTS;

Received as a result of improper operation and storage of automatic telephone exchange;

The result of poor-quality repair work.

Since the description of damages, defects does not always give a complete picture of them .. it is advisable to accompany information about damages, defects with appropriate photographs, video filming, sketches, sketches, diagrams, etc.

To this section UNWANTED include conclusions and suggestions about the possibility, methods, ways of restoring AMTS (replacement or repair of parts, the amount of labor intensity of the repair, its technology, etc.).

Damage, with a high degree of probability, related to the "incident under consideration, it is advisable to include in the inspection report indicating their presence or absence in the traffic police certificate. It is also necessary to indicate damage, with a high degree of probability, not related to this incident.

The presence of severe corrosion of the metal, or other defects in the operation of the vehicle, which largely affect the technology, the cost of repairs, should be noted in the inspection report.

After filling out the section in the "Inspection Certificate" "INSTALLED DURING INSPECTION" this section is signed by the specialist performing the inspection, and after familiarization, by the interested parties present at the inspection. All signatories should be able to state their dissenting opinion and remarks in the Inspection Certificate.

When drawing up the Inspection Certificate and other documents, you must use terminology, adopted in the normative, technical, technological documentation: in the manual for the repair technology, the manual for maintenance and repair, in the catalogs of spare parts and other technical literature.

Each damaged part should have a separate section line and, if possible, a photograph.

Inspection should be carried out systematically, consistently. One of the options for the inspection sequence can be a scheme based on the principle of transition from one inspected group of parts to another only after the description of all damaged parts included in the group of the same name is completed. The sequence of alternating groups is chosen by a specialist, and the order of subgroups is preferably in accordance with the increase in their ordinal number. The proposed inspection procedure avoids missing damaged parts during inspection and is very convenient when calculating a repair estimate, especially if it is performed using a computer.

For example, first we inspect the parts of the 28th group (frame, protective elements of the body), then 84 groups (plumage), etc.

3. For recommendations on the repair of a vehicle in the Inspection Report there is a section "CONCLUSIONS". This section is filled in by a specialist without discussion and agreement with other participants in the inspection, after analyzing the technical feasibility and economic feasibility of carrying out the proposed work.

During the initial examination of AMTS, it is not always possible to identify all damage and defects. In such cases, all assumptions for hidden damage, defects should be recorded in the Inspection Certificate and the document issued to the interested organization (person), but they should not be reflected in the cost of repairs until they are finally established during subsequent inspections

AMTS. The calculation of the cost of repair may include the necessary control and diagnostic operations.

By agreement with the customer Inspection certificate may not be compiled. In this case, all the necessary data is entered into the report.

Table 4.3.1.

Similar information.

The transport and traceological examination of traces of damage studies the patterns of displaying information about the event of a traffic accident and its participants in the traces, methods of detecting traces of vehicles and traces on vehicles, as well as techniques for extracting, fixing and researching the information displayed in them.

At NEU "SudExpert" LLC, trace examination examinations are carried out in order to establish the circumstances that determine the process of interaction of vehicles upon contact. In this case, the following main tasks are solved:

• determination of the angle of relative position of vehicles at the moment of collision
• determining the point of initial contact on the vehicle
• establishing the direction of the collision line (direction of impact impulse or relative speed of approach)
• determination of the collision angle (the angle between the directions of the velocity vectors of cars before the collision)
• refutation or confirmation of contact-track interaction of vehicles

In the process of a trace interaction, both objects participating in it often undergo changes and become carriers of traces. Therefore, the objects of trace formation are subdivided into perceiving and generating in relation to each trace. The mechanical force that determines the mutual movement and interaction of objects participating in trace formation is called trace-forming (deforming).

The direct contact of the generating and perceiving objects in the process of their interaction, leading to the appearance of a trace, is called a trace contact. The contacting areas of the surfaces are called contacting. Distinguish between track contact at one point and contact of a set of points located along a line or along a plane.

What are the types of vehicle damage?

Visible footprint - a trace that can be directly perceived by sight. All superficial and depressed traces are visible;
Dent - Damage of various shapes and sizes, characterized by indentation of the trace-receiving surface, which appears as a result of permanent deformation;
Deformation - change in the shape or size of a physical body or its parts under the influence of external forces;
Bully - traces of sliding with an elevation of pieces and part of the trace-sensing surface;
Layering — the result of transferring the material of one object to the trace-perceiving surface of another;
Exfoliation — separation of particles, pieces, layers of matter from the surface of the vehicle;
Breakdown — through damage to the tire resulting from the introduction of a foreign object into it, with a size of more than 10 mm;
Puncture — through damage to the tire, resulting from the introduction of a foreign object into it, up to 10 mm in size;
The gap - damage of irregular shape with uneven edges;
Scratch — shallow superficial damage, the length of which is greater than its width.

Vehicles leave footprints by applying pressure or friction to the sensing object. When the trace-forming force is directed normal to the trace-receiving surface, the pressure is noticeably dominant. When the track-forming force has a tangential direction, friction dominates. When vehicles and other objects come into contact in the process of a road traffic accident due to impacts of different strength and direction, traces (tracks) appear, which are divided into: primary and secondary, volumetric and superficial, static (dents, holes) and dynamic (scratches, cuts ). Combined marks are dents that turn into slip marks (they are more common), or vice versa, slip marks ending in a dent. In the process of trace formation, so-called "paired traces" arise, for example, a layering trace on one of the vehicles corresponds to a paired delamination trace on the other.

Primary traces- traces that have arisen in the process of primary, initial contact of vehicles with each other or vehicles with various obstacles. Secondary traces are traces that appeared in the process of further displacement and deformation of objects that entered into a trace interaction.

Volumetric and superficial traces are formed due to the physical effect of the forming object on the perceiving one. In the volumetric trace, the features of the generating object, in particular, protruding and recessed relief details, receive a three-dimensional display. In the surface trace there is only a planar, two-dimensional display of one of the surfaces of the vehicle or its protruding parts.

Static traces are formed in the process of trace contact, when the same points of the forming object affect the same points of the perceiver. Point mapping is observed under the condition that at the moment of trace formation, the forming object moved mainly along the normal relative to the plane of the trace.

Dynamic traces are formed when each of the points on the surface of the vehicle sequentially acts on a number of points on the receiving object. The points of the generating object receive the so-called transformed linear mapping. In this case, each point of the generating object corresponds to a line in the trace. This occurs when the generating object is tangentially displaced relative to the perceiving one.

What damage can be a source of information about an accident?

Damage as a source of information about a road traffic accident can be divided into three groups:

First group - damage resulting from the mutual introduction of two or more vehicles at the initial moment of interaction. These are contact deformations, a change in the original shape of individual vehicle parts. Deformations usually occupy a significant area and are noticeable during external examination without the use of technical means. The most common deformity is a dent. Dents are formed in the places of application of forces and, as a rule, are directed towards the inside of the part (element).

Second group - these are gaps, cuts, breakdowns, scratches. They are characterized by through destruction of the surface and the concentration of the trace-forming force on an insignificant area.

Third group damage - prints, i.e. surface displays on the trace-perceiving area of ​​the surface of one vehicle of protruding parts of another vehicle. Imprints are exfoliation or layering of a substance that can be reciprocal: the flaking of paint or another substance from one object leads to a stratification of the same substance on another.

Damages of the first and second groups are always volumetric, injuries of the third group are superficial.

It is customary to distinguish also secondary deformations, which are characterized by the absence of signs of direct contact of parts and parts of vehicles and are a consequence of contact deformations. Parts change their shape under the influence of the moment of forces arising in the case of contact deformations according to the laws of mechanics and resistance of materials.

Such deformations are located at a distance from the place of direct contact. Damage to the side member (side members) of a passenger car can lead to skewing of the entire body, i.e. the formation of secondary deformations, the appearance of which depends on the intensity, direction, place of application and magnitude of force in the course of a road traffic accident. Secondary deformities are often mistaken for contact deformities. To avoid this, when inspecting vehicles, first of all, traces of contact deformations should be identified, and only then can secondary deformations be correctly recognized and identified.

The most complex damage to a vehicle is distortions, characterized by a significant change in the geometric parameters of the body frame, cab, platform and stroller, door openings, hood, trunk lid, windscreen and rear glass, side members, etc.

The position of vehicles at the moment of impact during a transport and traceological examination, as a rule, is determined in the course of an investigative experiment on deformations resulting from a collision. To do this, the damaged vehicles are placed as close to each other as possible, while trying to combine the areas that were in contact upon impact. If this cannot be done, then the vehicles are positioned in such a way that the boundaries of the deformed sections are located at equal distances from each other. Since such an experiment is rather difficult to carry out, the position of vehicles at the moment of impact is most often determined graphically by drawing the vehicles on a scale, and by drawing damaged zones on them, the angle of collision between the conditional longitudinal axes of the vehicles is determined. This method gives a particularly good result in the examination of oncoming collisions, when the contacting areas of vehicles in the process of impact do not have relative displacement.

The deformed parts of the vehicles with which they came into contact make it possible to roughly judge the relative position and mechanism of interaction of vehicles.

When a pedestrian hits a pedestrian, the typical damage to the vehicle is the deformed parts that were hit - dents on the hood, fenders, damage to the front pillars and windshield with layers of blood, hair, fragments of the victim's clothing. Traces of layering of fibers of clothing fabric on the side parts of vehicles will make it possible to establish the fact of contact interaction of vehicles with a pedestrian during a tangential impact.

When overturning vehicles, typical damages are deformations of the roof, body pillars, cab, hood, fenders, doors. Traces of friction on the road surface (cuts, tracks, paint peeling) also indicate the fact of overturning.

How is traceological examination carried out?

• external inspection of the vehicle involved in the accident
• photographing the general view of the vehicle and its damage
• fixing malfunctions resulting from a road traffic accident (cracks, breaks, breaks, deformations, etc.)
• disassembly of units and assemblies, their troubleshooting to identify hidden damage (if possible, these works)
• determination of the causes of the detected damage in terms of their compliance with the given road traffic accident

What to look for when inspecting a vehicle?

When inspecting a vehicle that participated in an accident, the main characteristics of damage to body elements and empennage of the vehicle are recorded:

• location, area, linear dimensions, volume and shape (allow you to highlight the zones of localization of deformations)
• the type of damage formation and the direction of application (allow you to highlight the surfaces of trace perception and trace formation, determine the nature and direction of movement of the vehicle, establish the relative position of vehicles)
• the primary or secondary nature of the formation (allow to separate the traces of repair effects from the newly formed traces, to establish the stages of contact, in general to make a technical reconstruction of the process of introducing vehicles and the formation of damage)

The collision mechanism of vehicles is characterized by classification features, which are divided by traceology into groups according to the following indicators:

• direction of movement: longitudinal and cross; the nature of mutual rapprochement: into oncoming, passing and transverse
• the relative position of the longitudinal axes: parallel, perpendicular and oblique
• the nature of the interaction upon impact: blocking, sliding and tangential
• direction of impact in relation to the center of gravity: central and eccentric

More detailed free consultation on transport and traceological expertise can be obtained by calling NEU "SudExpert" LLC

Sale of broken cars is a serious business, but for some it is a piece of bread with red caviar. Because it is profitable to trade them. Emergency vehicles are bought cheaply, repaired and pampered in such a way that the phrase "new condition" does not hurt the eye. The price tag is set accordingly.

Inexperienced buyers often fall for a pretty candy wrapper, add excitement and a classic trick: "I wanted to sell for 450, I'll give you for 420 ..." And here the desire to buy a nice car outweighs common sense.

But there is an honest option next to it, but its body is chipped, the paint has faded, and the price is higher ... But inside there is healthy iron, but how do you know about it?

Usually, restored cars are sold through car markets by professional resellers, but an ordinary private seller can also slip a battered one, and even an official dealer. It is actually not difficult to distinguish an emergency copy, and it is worth learning this, at least in order to bargain well. In addition, not every broken car is a reason to refuse a purchase, and you need to be able to distinguish between serious "automotive body" from cosmetic repairs.

Suspiciously good paintwork condition

WITH market auto dealer Andrey we come to a black Lada-2110, and from a distance of 10 meters he concludes: “Don't look at this one. The whole "face" is painted. "

Even with careful use, chips appear on the car body: they usually concentrate on the front bumper, radiator grille and hood. In "vaziks" the thickness and strength of the paintwork are small, so that the hood "pockmarked" from chips is a normal phenomenon. The specimen in question with a declared mileage of 75 thousand kilometers has a hood and bumpers amazingly black and, most likely, recently repainted.

Pay attention to the thresholds - they are usually covered with a net of small scratches from the shoes. If on the one hand they are not, this is a reason to take a closer look at the thresholds: perhaps they were painted.

Uneven body clearances

Semi-handicraft repairs often show the "curvature" of the body, which is especially noticeable at the interface between the panels. “It is not so much the absolute value of the gap that is important as its uniformity along the length and the difference with the gap on the symmetrical side of the car,” says body shop foreman Vadim Bestemyanov. “Russian cars usually have more curves from the factory, but if it fits into a finger somewhere, and just below the parts are almost overlapped, this is a broken copy.”

Look at the photo: The walking gap between the edge of the bonnet and the radiator grille of a Ford Focus is unhealthy. Our suspicions were later confirmed.

A broken body can give out an indistinct closing of doors, so experienced buyers must check their functioning: are there any jamming, squeaks, or fuzzy operation of locks?

And in the photo below - a Chevrolet hatchback, in which we find inconspicuous cracks on the rear lamp housing. A closer inspection reveals that these are traces from the fifth door, which, when closed, beats against the plastic mounts of the brake light, damaging them. The reason was established a minute later: the back of the car was being repaired.

Even door handles can give out "automotive body". “Small parts like door handles do not change during budget body repairs, so their unexpectedly poor condition should lead to thoughts of problems with the car, as is the case with this Ford Focus,” says Vasily.

Hands at the seams

At the plant, car bodies are welded from individual parts, mainly by spot welding, after which the joints are sealed with a special sealant. The method of applying the sealant is different: at the Nissan plant near St. Petersburg, it is done by workers using special pistols, in the Hyundai Solaris and Rio workshops - by robots. Subsequently, the sealant is fired and the body is painted.

Factory sealant looks neat, is well painted over and is often almost invisible. In body repairs, it is applied more knotty, often smeared, and the consistency is sometimes similar to dried paint.

Vasily Martyanov draws attention to the rough seam around the bracket of the Chevrolet's fifth door, the very one that caught our attention with the split brake light housing. “It is immediately clear that the sealant here is non-factory, and on both sides, which means, most likely, there was a blow to the rear - because the trunk lid now does not close as it should,” he concludes.

Sometimes the sealant is placed neatly enough, and if in doubt, Vasily advises to look at the seams of a new or guaranteed not broken car of the same model.

Weld seams are more difficult. During the repair, two welding methods are used: spot and seam welding (including in inert gases). Spot welding is also used at the factory, so it would seem that the fact of repair should be invisible. However, Vadim, the coachbuilder, insists that this is not the case. “Look,” he runs his finger along the lower part of the thresholds of a car hanging on a lift. - On the one hand, there are factory spots from welding, but here are traces of the workshop's work. The points are not so even, traces of burns are visible, which means that the threshold was welded again. "

It is not always possible to use spot welding during repairs. At the factory, the parts are connected in a certain sequence, and in the workshop it is not always possible to crawl with welding tongs to each joint or get the desired overlap. Then they use welding with a continuous or intermittent seam, which is easy to distinguish by eye.

If in some place you did not find traces of spot welding, although they are on the other side of the car, most likely the car has undergone major repairs.

“But there are little tricks,” Vadim shares. - Craftsmen often seal the weld spot with putty, and then make marks with the back of a pencil with an eraser that look very much like spot welding marks. Then the site is primed, painted over and looks like a factory version. "

Measurement of paintwork thickness

A more accurate way is to determine the thickness of the paintwork using a special device, which is often called a "thickness gauge" in workshops. Vasily shows us the work of the Automation Dr Nix device using the example of a Cadillac. He applies the sensor to the fender of the car, and the thickness of the coating is displayed on the screen in micrometers. “310 ... 175 ... 110 ... - says Vasily and concludes: - Such a range of thicknesses suggests that the wing was painted. A factory paint coat is usually thinner and much more uniform than a repair paint. If putty was used, then the sensor readings will be even higher. Moreover, cars from different manufacturers have their own standards for the thickness of the paintwork: for Japanese and Russian, they are thinner, for American - usually thicker. "

Almost all body shops and dealerships have such a device, so if in doubt, drive the car to a specialist. Surely in your city there are visiting teams of experts who can evaluate a car right on the market or in a place convenient for you.

To take or not to take?

A damaged car, let alone a painted one, is not a reason to refuse a purchase. Firstly, the fact of repair in itself does not mean that vital organs are affected: there may have been a minor accident. A painted bumper with no other signs of repair is most likely the result of unsuccessful parking or an attempt by the owner to fix the chips. Minor operating injuries are almost inevitable.

Secondly, even if the impact damaged the load-bearing elements of the car, displaced the suspension attachment points or deformed the load-bearing structure, after a quality repair, the car may well still serve. The main thing here is not to overpay for it too much, but bitness itself is not a sentence.

Worse, if the repair was done poorly: an abundance of putty, poor paint, especially cracks in the paintwork, lack of fasteners - signs of a tyap-blooper-repair.

It is very bad if it was not possible to restore the geometry of the body: then you can rake a whole heap of problems from poor closing doors to the impossibility of setting the recommended values ​​of the wheel alignment angles. And this is already unsafe.

“It is very difficult to determine the change in the geometry of the body by eye, but there are indirect signs,” says Vasily. - I recommend paying attention to the uniformity of tire wear: if they are worn in different ways or their individual parts wore out faster, most likely, the camber-toe angle is knocked down, and this may be a sign of a critical violation of the body geometry. If the car comes with a second set of wheels, for example, winter ones, check it too. A car with unevenly worn wheels should be checked twice as carefully, and before buying, be sure to check whether the camber and toe angles are set in principle. If not, you shouldn't take the car ”.

There are cars with which it is better not to mess with: say, welded from the halves of two emergency vehicles. Such "centaurs" in the next accident are often torn in half with fatal consequences. Naturally, such a car can look good: fresh paint, a new interior, a lively engine ... but only for the look of a layman, to whom such “designers” are addressed.

Another way to insure yourself is to buy a car at the Trade In showroom from an authorized dealer: such cars are diagnosed before being accepted, so that their background is known to the future buyer in advance. Usually, Trade In dealerships do not take broken copies for sale at all.

What you shouldn't get hung up on

Small dents without damage to the paintwork usually do not threaten anything, except for the loss of aesthetics, and in some services they are straightened out using the Paintless Dent Repair method (for example, marks from "enemy" doors on the sidewalls of a car).

Chipped bumpers and scratches also do not affect functionality. In cramped European cities, flat bumpers are normal. A crooked bumper or torn off aerodynamic aprons underneath often indicate an unsuccessful off-road sortie, but if the rest of the elements are intact, this is not critical.

A grid of micro-scratches on the surface of the body appears in the first months of operation after washing - this is an almost inevitable evil.

Local touch-up of elements, most likely, is not a problem, and if in doubt, check the area with a “thickness gauge”: is there a thick layer of putty under the paint? In any case, this is a reason to knock down the price a little (if the buyer did not declare the damage in advance).

Body repair technology

Let us briefly tell you how exactly the machines with serious damage are restored.

First, the injured part is disassembled, the "dead" parts are discarded, and the body parts are thoroughly troubleshooting. Sometimes it is more profitable to pull the spar, sometimes to change it to a new one.

In serious centers, systems are used to measure the geometry of the body. They are different: laser, template, mechanical, but the point is the same - to determine the displacement of key points of the body and the direction in which it needs to be pulled.

An article about local repair of a car body - preparation, procedure, subtleties of work. At the end of the article - a video about car body repair.

The content of the article:

Regular operation of the car sooner or later leads to the repair of its constituent parts, including the body. This article will focus on local body repair.

When does the body require local repair

There are many reasons that lead to the repair of a particular part of the body. These can be mechanical damage to the paintwork by road debris, the consequences of minor accidents, chemical damage due to improper use of reagents and, finally, the manifestation of ordinary corrosion.

Of course, as a result of these damages, the car does not lose its technical characteristics, and therefore there is no reason to hand it over to scrap. Only the external aesthetics of the car suffers, and this problem is quite simple to solve. And if you repair everything with your own hands, then the economic benefits will be obvious.

Preparation for local repair

Before local body repair, you need to wash the car well, and then diagnose for defects. This is necessary in order to know for sure which parts of the body need to be repaired, as well as what tools and equipment will be required for this.

The first step is to investigate the nature of the damage. For example:

• dents resulting from an accident, as well as from impacts of stones from under the wheels;
• violation of the integrity of the paintwork: chips, cracks, scratches, etc.;
• corrosion.

If this damage is mechanical and at the same time it is associated with a rupture of metal surfaces, or if it is a typical corrosion, which has “eaten through” the metal through and through, then it would be reasonable to replace the damaged part with a new one. The same can be said about those damaged areas in which the stiffeners suffered. But if the part cannot be replaced (the model is outdated), it can, in principle, be restored, but it will be much more difficult to do this than to replace it.

In addition, it is necessary to find those places that require correction of geometric deformation, as well as note all minor damage that can be easily removed with a putty. As a result of such a defect analysis, you will know which body parts will require subsequent repair.

Replacing a damaged body part

The most effective way to repair a damaged body part is to replace it. But if you nevertheless decided to repair the part, then in this case it will have to be dismantled. So let's start with dismantling.

Most of the body parts can be bolted or self-tapping, so it is not difficult to remove them, and without the use of welding. By the way, if the repaired part is installed already painted, it will be much better and easier.

However, there are parts that are assembled using spot welding. To dismantle them, use a special chisel and hammer. With these tools, a weld point is cut between the parts at the attachment point.

After the part has been removed, all joints must be cleaned of corrosion, and, if necessary, rehabilitated, possibly by welding, and then straightened. Anti-corrosion treatment after that clearly does not hurt.

It is better to install the repaired part using special mastic, as a result of which the elements will connect to each other much more tightly and tightly. In this case, additional waterproofing will appear. It is advisable to do this with any method of connection, but if you use welding, you must keep the welding points clean.

Straightening of body surfaces

Methods for correcting geometric dents are quite dependent on the type of damage, so each case is considered individually. Let's distinguish two main types of deformations:

• crushing;
• the so-called "poppers".

Crumpling changes the geometric shapes and sizes of body parts, so this kind of damage requires stretching, and this process is quite laborious. The pulling principle resembles the recovery of wrinkled paper. To do this work, you need the appropriate knowledge, skills and abilities, as well as special tools: a reverse hammer, all kinds of stretching, etc.

Puttying

No local body repair can do without putty. The fact is that, having repaired the damaged body parts, in any case, you will have to go to the final cosmetics.

The first step is to close the deepest irregularities, the depth of which exceeds 1 mm. To do this, use a coarse filler. At the same time, do not forget that among the parts that make up the body there are parts that are subject to vibration and can deform from this.

When processing such parts, use a putty containing an aluminum filler. Fiberglass putty can be used for the rest of the parts.

Roughing stage

To begin with, the places where you plan to apply the putty will have to be matted. This can be done with a medium-grit emery cloth for better adhesion to the surface.

After you finish matting, the surface to be treated must be thoroughly cleaned and degreased.

The next stage is directly puttying. And this process should take no more than 20 minutes. In any case, most putties have this setting time. Therefore, in order to be in time, proceed as follows:

1. Dilute the filler according to the manufacturer's instructions. After that, mix the solution thoroughly enough so that the composition excludes air bubbles, has a measured color and the same consistency.
2. Start applying the solution to the surface with a spatula. At the same time, be extremely careful not to overestimate the required layer thickness. Therefore, it is better to apply thin layers in several steps to achieve the desired level. And if the surplus does appear, they must be removed immediately.
3. Allow the putty to harden.

Note: of course, it is impossible to immediately apply the putty so that later this surface does not require mechanical processing. Therefore, it will be very good if you come to a result that is as close to ideal as possible.

As already mentioned, mechanical processing of the putty surface cannot be avoided in any case. Therefore, wait until the composition has completely solidified, and then proceed to processing.

To do this, stock up on emery cloth and a wooden block. For a start, you can use a medium-grained skin, and try to pick up a block that is not very large, but fairly even.

The method of such processing is quite simple: wrap the block in "sandpaper" and begin to process the surface to be repaired with it. It is due to the even bar that you can identify where it is necessary to remove excess putty, and where it needs to be added.

You can use an orbital sander besides the sandpaper-wrapped bar, but it takes care and a lot of experience to use it. And if there is no such experience, then it is better to grind by hand, as described above - you will make fewer mistakes.

Despite the fact that this procedure is quite simple, rare specialists manage to do everything the first time. Therefore, after the first treatment, check the result and, if necessary, repeat it all over again. Your ultimate goal is to keep the surface level and free of pits, bumps, or seams.

Finishing stage of filling

So, you have done the "blackest" work, the repaired surface already has a favorable appearance, and now there is little left to do - to eliminate small defects. The problem is that sometimes it is even impossible to notice them with the naked eye, but after repair they will definitely show themselves.

And here you will need another, fine-grained putty, which is also called finishing. You apply it in the thinnest layer to those places that require it: scuffs, scratches, an excessive layer of coarse-grain putty.

The condition is the same as with the use of a coarse-grained putty - you need to have time to apply the composition before its initial hardening. After that, there is a stage of mechanical finishing, and fine-grained sandpaper is already used here, which is popularly called zero.

This work should also be done manually if there is no experience in using special tools. The necessary result of this procedure is the complete absence of irregularities, both visible and invisible, and tangibly tangible.

In this final action, sometimes it is possible to apply the putty in several layers, but in most cases one is enough.

Once you have done all this, the repair can be considered complete. All that remains is to paint the repaired areas and your car will look like new.