Identification of threats during the bodywork and paint repair process

. Body repairs are often based not so much on procedures as on the experience of the people who perform these repairs. The problem is that heat repairs change the internal structure of the vehicle's skin. When obtaining homologation, manufacturers must prove the specific strength of the materials during crash tests. During a bodywork repair, these parameters may change, and after the repair, there is no obligation to check the strength parameters of a specific element or system. By interfering with the structure, we cannot be sure that we still maintain an appropriate level of security. Therefore, during further tests, together with a team from the Bydgoszcz University of Technology, we plan to check the strength parameters of the vehicle's skin after repair. And what impact on the structure of the material is the duration of individual stages of sheet metal work, the intensity of the current and the temperature to which the material is heated in order to optimize the parameters and increase the level of safety of users.


Introduction
Certainly, it would be difficult to find a driver who has never dented the body of their car.Even if the incident does not have serious consequences, it leaves a small indentation, which may be accompanied by scratches or cracks in the paintwork.In such a situation, the only solution is to use professional body repair services [3].
Body damage is an integral part of a driver's life.All it takes is a moment of inattention, limited visibility, lack of sufficient space, insufficient lighting, or simply an unfortunate coincidence for a collision or accident to occur.Parking damage is also often the case, i.e. hitting another car, pole or wall.Even harsh weather conditions, such as hail, can cause damage to the bodywork.During strong winds, there is a risk that a branch will fall on our car.There is only one result: a damaged bodywork.A dent is not only associated with an unsightly appearance, but can also cause problems in the future, e.g. when selling a car.Damage to the bodywork significantly reduces the value of the car, so it's a good idea to take care of the dent right away [9].
Another important aspect that is often overlooked is the fact that damaged parts of the car's body are subject to mechanical treatments during repair, which change their properties and thus change the level of safety, because during a collision, the elements that were repaired may not reach the strength parameters that the vehicle originally had.

Methods of bodywork and paint repairs
Classic body repair is very effective, but quite complicated.The damaged workpiece is straightened by tapping.It is also often necessary to heat the sheet metal to give it the right plasticity.Repairs usually involve disassembling the damaged component.It is important to remember that bodywork and painting are closely linked.Repairing a damaged element is associated with the need to replenish the paint defects [1,2].It can be the entire part of the bodywork or at least parts of it.Painting requires proper surface preparation, which is why the repair takes quite a long time.After coating with varnish, you also need to take care of anti-corrosion protection on the inside of the area that has been repaired.Therefore, it is important to be patient during bodywork and paint repairs.The whole process can take up to 3-4 days.A good solution may be the so-called panel repair.It is performed with the use of the socalled sheet metal spotter.It avoids damaging the structural joints of the car body, as there is no need to cut out factory components.In the panel method, there is no overheating of the sheet metal, so there is no need to rebuild the internal corrosion protection.It significantly shortens the car's stay in the body shop and reduces painting costs.Picture 1 shows an example of a Blahar repair.
Table 1 contains a list of procedures that must be performed during body work [developed on the basis of experience and 11].

Prevent corrosion and paint float problems caused by untreated weld seams
No matter how professionally the welding work is done, each welding seam will have microholes, allowing moisture to penetrate.No hygroscopic filler, such as standard polyester, will seal the surface, but will allow this moisture to seep into the paint film.In the long term, this leads to corrosion and paint floating [4][5][6].
In order to eliminate undesirable effects, an epoxy metal filler should be used, which replaces the traditional tin soldering process.In the case of welding deformations resulting from the use of modern low-temperature welding methods and dent repairs of high-strength steel, galvanized steel and aluminum substrates.The repair process is shown in Table 2 [developed on the basis of experience and 11].
Please wait 10 minutes before using the infrared heater and dry for 10-20 minutes at a panel temperature of 70°C

Research area
Body repairs are often based not so much on procedures as on the experience of the people who perform these repairs.The problem is that heat repairs change the internal structure of the vehicle's skin.When obtaining homologation, manufacturers must prove the specific strength of the materials during crash tests.During a bodywork repair, these parameters may change, and after the repair, there is no obligation to check the strength parameters of a specific element or system [7].
By interfering with the structure, we cannot be sure that we still maintain an appropriate level of security.Therefore, during further tests, together with a team from the Bydgoszcz University of Technology, we plan to check the strength parameters of the vehicle's skin after repair.And what impact on the structure of the material is the duration of individual stages of sheet metal work, the intensity of the current and the temperature to which the material is heated in order to optimize the parameters and increase the level of safety of users.

Conclusions
Body repairs are not cheap, mainly due to the extensive experience and knowledge required in carrying them out, as well as the requirement to have specialized tools.
As for the damage, it is sometimes possible to remove it without disturbing the paintwork, but this is only the case in the case of minor damage.Usually, however, the repaired element has to be repainted, which further increases the cost of carrying out the repair.
To make car bodies, a sheet of small thickness is used, which varies depending on the specific car model.It is obtained from a metal lump using the smelter rolling method.Currently, various grades of steel sheets and aluminum alloys are used to make body parts such as fenders, doors, bonnets, trunk lids or roofs.Both steel and aluminum alloys have a specific tensile and compressive strength.They are characterized by high elasticity and plasticity, but in the case of aluminum alloys, the elasticity is lower.
Due to the above-mentioned properties of the materials from which the body parts are made, they can be straightened, patted and levelled instead of being replaced with new elements.
Keep in mind that when a particular element is badly damaged, it will be better to look for a used element with the same body color code instead of repairing the damaged one.
Instead of repairing the body panels, a much better solution is to buy a used car part in any color and paint it in the color of your car.In this way, we will avoid applying a large amount of putty, which, if carried out incorrectly, may contribute to rapid corrosion of the repaired element [10] Both when the damage is not too great and when it is the result of a more serious collision or accident, the repair should be entrusted to a body and paint shop, because there is no one type of material from which body parts are made, and every car produced today is made of materials dedicated only to a given vehicle model [8].
Outsourcing the repair to a good body and paint shop is the best way out of the situation, because the employees of such a workshop must have the appropriate qualifications and knowledge needed to carry out the repair properly.In addition, they can use professional tools designed for this type of repair.A properly performed bodywork and paint repair is a perfectly reproduced line of the vehicle, very good fitting of the elements, without visible differences in the width of the gaps between adjacent body parts.

Fig. 2 .
Fig. 2. The process of applying a layer of material.

Table 1 . Bodywork repair procedure. Procedure Step-by-step instructions Necessary tools and consumables
•• The curing of fast curing epoxy metal filler can be accelerated by using IR drying after the initial gel period.

Table 2 .
Car Body Repair Process -Welding Seam Processing