Twitter You Tube Facebook Autobodynews Linked In

Monday, 25 July 2011 16:49

Are Your Repair Methods Ten Years Out of Date?

Written by Toby Chess

The other day I received a report form Aaron Schulenberg, the Executive Director of the Society of Collision Repair Specialists, about a study done in Germany on collision repairs. Crash-test results and analysis of the impact of a non-professional repair on the performance of the side structure of a car (VW Passat) by KTI GmbH& Co. of  Lohfelden, Germany.

The study took a late model VW Passat, with ultra high strength steel reinforcements in the rocker and “B” pillar, conducted a side impact at about 30mph, detailed all the damage, and rebuilt the vehicle using used parts, MIG welds, and an older Squeeze Type Resistance Welder.  They did not use any OEM current replacement data, but they utilized common accepted repair methods used in the collision industry. They referred to those in the article as “10-year old repair methods.” 
What was written in the introduction of the study is what I and others have been preaching for years.

“The new materials mean that body shops must continuously ensure that they are conversant with the requirements for new tools, procedures and information about the repair processes. New welding machines need to be used, training is required, and OEM information has to be accessed to make sure that the correct repair methods will be applied. Without this knowledge it is likely that an inadequate repair will be the result, potentially placing the car and its occupants at much higher risk in a later crash.”

“In parallel to the introduction of new materials, single component parts of earlier vehicles have been replaced by highly integrated, multi-material components on more recently designed cars. The production of a modern Body-in-White is characterized by complex manufacturing processes and bonding techniques. Taken together, the technical progress made by the OEM’s has resulted in corresponding new challenges for the repair shops. Repair shops must ensure they have well trained staff and are equipped with appropriate tools to cope with the techniques needed for professional repairs on today’s cars when they are damaged in an accident. If such techniques and knowledge are not available, a nonprofessional repair may lead to a significant reduction in the safety and quality of these cars.”

“Unprofessional repairs" may result from of all or any of the following:

● Incorrect method and/or sequence of repair
● Poor assembly of correct/incorrect spare parts, components and sub-systems
● Fitment of low-quality spare parts, components and sub-systems
● Incorrect assembly and connection of electrical/electronic systems and sub-systems
● Absence of correct, special or custom tools
● Repair of damaged parts when actual replacement is necessary.”

Let’s take a look at the study. I going to give you a condensed version for this article, but you may read the entire study at the SCRS website ( or at (see my column section).

The following scenario, including two high-speed crash tests was carried out, and then analyzed:
1. The car was damaged by a side impact similar to an intrusion by the front of another car into the passenger side of the test vehicle, according to the side-impact tests of Euro NCAP.
2. A repair was carried out as if done in a car body shop or garage with no information about the correct way to repair this particular car and without the correct tools or welding machines. The repair conforms to a typical standard carried out about 10 years (two car generations) ago. This would be considered as a non-professional repair by today’s standards.
3. After the repair, this vehicle was involved in a follow-up crash simulation in the same configuration i.e., a side impact on the repaired passenger side, at the same speed.

The picture below shows the set up of the side impact test.

“After the side impact the car was severely damaged on the passenger side, as intended. The sill and the floor/undercarriage behind it were particularly distorted. Additionally, the doors and the B-pillar were considerably damaged. There was no damage to the screen pillar or windscreen glass. The pyrotechnic protection/restraint systems (Front and rear passenger side airbags, front passenger belt pre-tensioner and passenger side curtain airbag) were correctly deployed. Overall the car body structure deformed and behaved as expected. As well as the visual analysis, electronic measurement of the car body was carried out. This showed the maximum intrusion to be 161 mm.”

The vehicle was repaired after the test and these were the procedures followed:”

The damaged car was repaired with an older spot welding machine with fixed pressure and 6.4 kA maximum current.

Note: It is recommended that an Inverter type welding machine is used with 10 kA maximum current and a variable pressure (maximum 10 bar) to join the high strength steel safely. The deformed inner sill, made from ultra high strength steel, was re-shaped and partially replaced on a bench then re-fitted using a MAG welding process.

Note: The “Professional” repair would include complete renewal of the B-Pillar and other deformed structures with components made from high strength steel. A partial repair of such steels is not acceptable, as the structure and therefore the strength of the material will be severely degraded while welding and reforming.”

“After the vehicle was repaired, the vehicle was crashed again and all the  noted areas in the first crash were compared with the second crash.

It was immediately evident that there was a substantial difference, with far more comprehensive deformation of the car body after the second impact. The B-pillar had noticeably higher intrusion into the passenger compartment in comparison with the first crash, especially at the lower part at the connection with the sill. Note: Later measurements of the car body confirmed there was 60mm more intrusion after the second test, compared to the first crash. Other differences were noticeable at the cant rail/roof and the transmission tunnel which both displayed severe deformation not seen in the first crash. It seems that the load paths were quite different in the second crash. It was also noted that the top right corner of the windscreen was damaged in the second crash, further indication of changed load paths. These comparisons made it evident that a change of load paths and therefore of the energy dissipation was due to the unprofessional repair. The pyrotechnic protection/restraint systems (Front and rear passenger side airbags and the front passenger belt pre-tensioner) were correctly deployed but the passenger side curtain airbag failed to operate.”

To make clear the differences between the two tests, we compared photographs, sequences of high speed crash-movies and electronic measurement of the car body. With the help of the time analysis in the high-speed crash-movies we can for instance compare the time of highest intrusion. The analysis clearly shows higher intrusion at the same moment in time in the second crash test.

Note that the side curtain deployed in the first crash test, but failed in the second one. I have video showing  the effectiveness of side curtains on vehicle occupant safety. In the first 2009 Prius, the side curtain was deployed and measurements of the crash dummies were taken. The result  was minor injury to the front and rear passengers. In the second scenario, the side curtains was disabled and another side crash test was conducted at 35 mph. The result was horrific. The driver’s head was struck by the crashing barrier, which would result in a death. The rear dummy sustained major injuries to the neck, shoulder and left arm. This is the reason that by the year 2013, all vehicles sold in the US will have side curtain air bags.

Note the great amount of damage to the rocker and B-pillar in the second crash test. This is very evident by the next set of pictures showing the damage to  the passenger seat in the second crash test.

“After removing all the seats and necessary trim, the deformation of the transmission tunnel after the second test was clear to see. The cross-member which supported the front seat had pushed into the transmission tunnel, distorting it severely. In comparison, there were no measurable changes at the transmission tunnel during the first attempt.”

As I stated in the beginning of the article, the complete test results can be found at the web sites. I strongly urge you (repair owners and managers) to print out the OEM’s recommended repair procedures and give them to your techs and estimators.  The liability is too high not to follow OEM procedures. Think about the safety of your customers and what it may mean in a second collision.

Read 4837 times