Vehicle repair damage detection

    With the rapid development of the automobile industry and the sharp growth of domestic car ownership, automobile collision accidents also show a rapidly rising trend. According to professional statistics, sheet metal maintenance in automobile maintenance accounts for about 27% of the total maintenance workload. In automobile maintenance enterprises, only less than 10% of the enterprises can repair large accident vehicles, and the rest can only be engaged in the maintenance of small accident vehicles. With the development of this trend, the auto sheet metal repair business is gradually optimistic, all kinds of auto repair stations, repair shops, and even beauty shops have increased investment in sheet metal repair business.
    After the vehicle was damaged by the impact, the sheet metal repair work began. From the damage analysis of the accident car after entering the factory to the diagnostic measurement of the sheet metal worker, from the tensile correction on the "operating table" to the local repair under the welder pick hammer, from the installation of sheet metal parts to the commissioning of the vehicle, in various processes, Professional and technical personnel should use a wide variety of different forms of equipment tools such as girder correction instrument, electronic measuring system, sheet metal repair machine, welding machine and a variety of grinding and cutting tools, using a variety of detection and maintenance technology to ensure that the vehicle in terms of geometric size and performance to restore the level of the original car. This topic will take the special repair process of the accident vehicle as the main line, analyze and discuss item by item, so that you can deeply understand the automobile sheet metal maintenance process and the application of modern automobile maintenance equipment in the accident vehicle maintenance.

1. Injury diagnosis
    Damage diagnosis is the first important step of sheet metal maintenance, according to the basic steps of automobile damage diagnosis, it is necessary to do each diagnosis and detection work in the following links.
1. Understand automotive body materials, structure and frame welding processes
In order to choose a proper sheet metal repair method, it is necessary to understand the body manufacturing materials and the frame welding process. The difference between modern automobile and traditional automobiles in body manufacturing materials and frame welding technology leads to changes in maintenance methods. For example, the traditional frame type body is mainly made of low-carbon steel or medium-carbon steel, in welding and cutting, should use the pneumatic body saw, if the use of traditional oxygen-acetylene cutting will cause greater damage to the body. Modern monolithic body frames are usually made of ultra-high strength steel (UHSS) or high strength steel (HSS) high strength low alloy steel (HSLA) or alloy materials (such as aluminum alloy) and must be welded using inert gas shielded welding or electronic spot welding machines in structural parts repair. In addition, the changes in the thickness of the steel plate and the different alloy compositions of the body material will also be the same in the selection of welding methods and relevant technical parameters, which requires familiarity with the body material for reasonable maintenance. After the collision damage to the car, it must be corrected by the method of all-round stretching, and the method of heating should not be used as far as possible to prevent the internal structure of the metal from changing, resulting in a reduction in strength, so that the car can not effectively protect the passengers when it crashes again.
    In terms of the frame welding process, modern body repair generally adopts fusion welding, pressure welding, and bonding, and the welding rod arc welding and oxygen-acetylene gas welding, which dominated body repair in the past, should be carefully used in modern body repair. Electrode arc welding is now only used for frame body and low carbon steel body repair; Oxy-acetylene gas welding, pressure resistance welding, and bonding are only used in some special processes. A special welding process is needed for the new aluminum body repair welding. Different welding processes should be adopted for body girders of different structures. To adopt the best welding method that will not reduce the original strength and durability of the body, it is necessary to be familiar with the welding process used in various parts of the original car.

2. Detect the basic condition of damage
    In the process of damage detection, it is necessary to visually detect the location of the collision, determine the collision direction and the magnitude of the collision force, and check the possible damage. For vehicles damaged in an accident, the speed of the car at the time of the accident and the part, direction, and Angle of the crash or rollover should be asked to understand the form, position, and Angle of the impact of the car, to determine the part of the collision damage and the area that may be affected by the collision intuitively. It can also be combined with test and measuring instruments to conduct a comprehensive inspection of the car, confirm whether the body floor is deformed, whether the body is damaged and twisted as a whole, check and confirm whether the door is open freely, etc., to determine the extent of damage and repair methods of the car.

3. Identify all damaged areas
    The impact of the vehicle is not only the appearance of the damage, but the vehicle is directly seen after the impact of the damage, and even the insurance assessment is often only to assess the damage. The current car body design mostly adopts the rigid and flexible design principle, the use of absorption decomposition theory to buffer the impact force, to ensure the maximum degree of safety of passengers, so when the vehicle is affected by the impact of not only the deformation of the impact site damage, the entire body of many parts such as girder, suspension, and engine may also produce deformation. Sometimes, some vehicles are hit in the front, and the rear is found to be deformed. In this case, if you simply repair the affected part in sheet metal maintenance, it will certainly bring hidden dangers to the driving of the vehicle. Therefore, after the vehicle is damaged, it is necessary to observe the damaged condition of the vehicle body, figure out how the body is stressed during the collision, how the force is transmitted along the body, and conduct an in-depth analysis of the damaged parts and components in relevant areas for scientific diagnosis to determine all the damaged parts. The inspection process requires checking all damage to the relevant parts along the collision route system until there are no traces of damage, as well as damage to the surrounding area.

Identify all damaged areas

4. The damaged area is measured with the equipment tool
    SPANESI TOUCH electronic measurement system
(1) Dismantling
    The measurement work needs to be combined with the disassembly work, otherwise, the full extent of the damage cannot be accurately identified. To facilitate the maintenance operation and thorough inspection of the damage to the body, and avoid unnecessary damage to the disassembled parts during the maintenance operation, the relevant parts should be disassembled. The principle of disassembly is to avoid the damage and destruction of the parts as far as possible, the disassembly method of the connecting parts in addition to the wrench, can also be used according to the actual situation, electric drill, saw, chisel and gas cutting tools.
(2) The importance of measurement
    Accurate measurement is one of the necessary procedures for successful collision repair. In the case of monolithic bodies, measurement is even more important for successful damage repair because most steering systems and suspensions are mounted on the body, and some suspensions are designed according to assembly requirements. Automobile kingpin rear Angle and wheel camber Angle are a fixed (non-adjustable) value, so that the body damage will seriously affect the suspension structure. Rack and pinion steering is usually mounted on a steel frame to form a fixed connection to the steering arm, while the engine, transmission, and differential are also mounted directly on the body members or the brackets (steel plates or monolithic steel beams) supported by the body members. The deformation of all these components can deform the steering machine or suspension, or misplace the mechanical components, resulting in steering operation failure, vibration and noise in the drive train, excessive wear of connection rod ends, tires, rack and pinion, common joints, or other steering devices. Therefore, to ensure the correct steering and handling performance of the car, the matching tolerance of the key machining dimensions must be controlled within the allowable range.
(3) Measurement method
    Post-dissection measurement is a necessary prerequisite for "diagnosis" and "operation". Detailed damage can be estimated by measuring the dimensions of the car body relative to specific points on the body, which has become a widely used method. The values in the body dimensions drawing are based on the diagonal measurement method. Measuring points and measuring tolerances are determined by inspection of the damaged area. In general, the damage caused by a front-end crash that causes the door to sag slightly does not extend beyond the center of the car, so there is not much need to measure the rear. In the position where the collision is more severe, a large number of measurements must be made to ensure the proper adjustment sequence. However, a large number of measurement records can also cause unnecessary confusion. In the whole repair process, whether it is a traditional frame body vehicle or an integral body vehicle, measurement is very important. All major machining control points on the injured area must be reviewed against the manufacturer's instructions, otherwise, it is impossible to repair the car satisfactorily. To do this, sheet metal technicians must pay attention to:

① accurate measurement.

② Multiple measurements.

③ Reverify all measurement results.
To measure damaged vehicles, we should pay attention to the use of advanced measurement systems to improve work efficiency. In the process of deformation detection of the accident car, only experienced professional technicians can accurately analyze the degree of vehicle damage according to the size of the accident and the location of the impact, and then professional sheet metal technicians use modern precision measuring equipment to comprehensively and strictly detect the vehicle, and the test results should be compared with the chassis body data diagram provided by the manufacturer. So a reasonable repair plan can be determined. Pre-repair damage detection of damaged vehicles using the SPANESI TOUCH electronic measurement system
Test sheet for the damaged vehicle before repair
(4) The function of measuring body data
Even if the professional technician has rich experience in the repair of the accident car if he can not grasp the accurate data before and after the deformation of the vehicle, it is difficult to accurately formulate the repair plan, so the professional detection of the accident car and get accurate data can make the professional technician have a target. In terms of body girder positioning parameters, the data parameters of various models are the basis for the entire repair work. Measurement, positioning, stretching, and detection are carried out based on the data parameters of the original car. Without body girder positioning parameters, the repair work cannot be done well. When the body is designed and manufactured, the body reference control point is used as the positioning benchmark for assembly welding and processing, and it is also the benchmark for measurement in repair work. The deviation of these reference points will directly affect the performance of the car. For example, the deviation of the front suspension support point directly affects the front wheel positioning Angle and the vehicle wheelbase size. At the same time, for some special sizes, we can consult the body data.

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