Does your damage analysis measure up?

In recent years, the car manufacturers have dramatically changed both the materials and methods they use to build cars. Although drastic, unless you actually cut the car apart or attempt to straighten structural parts, these changes are not obvious. Unfortunately, many estimators are not up to speed on these changes and are missing significant damage during initial inspection. The technicians are finding this hidden damage much later in the repair process, causing extended cycle times and embarrassing complications with customers or insurance companies. If shops are to keep cycle times to a minimum, they will need to re-evaluate how they look for damage during initial inspection, tear-down and estimate blueprinting.  Measuring may need to be performed during initial damage analysis, perhaps in an estimating bay. This may sound drastic, but the consequences of finding additional damage at the end of the repair process are disastrous. To understand how these design changes can cause major problems during the repair, we need to discuss what these changes are.

The big difference in vehicle construction is in the way the unitized frame rails are made. In the past, rail ends (about the first 18 inches) were made with visible convolutions or a crush zone that was designed to collapse and absorb as much collision energy as possible. After the end of the rail absorbed all the energy that it could, the rail would continue to collapse farther and farther back. During damage analysis, buckles could be seen rearward of the initial crush zone. In that case, the whole rail was a uniform thickness, the same strength of steel and the damage was clearly visible. This was, for the most part, effective, but the designers believed that with engineering advancements, they could make the vehicle structure safer, easier to manufacture and lighter. Several new manufacturing processes were created to accomplish these improvements and are being combined to make the new generation frame rail. Explaining these design changes will make it evident that changes in the repair processes will also be necessary.

The manufacturers are now joining different thicknesses of steel together with

laser welding. This allows them to use a thinner gauge steel at the end of the rail to absorb crash energy and save weight. By laser welding the sections together, the weight from overlapping panels is reduced, manufacturing is more efficient and the corrosion trapping seams are eliminated. Typically the rail is thicker and stronger steel from the point of the suspension mounting areas, continuing back to the end, under the floor panel. This protects the passengers because after the maximum amount of crash energy is absorbed by the front of the rail, the stronger section of the rail is intended to transfer the remaining collision energy around or under the passenger compartment.

This design change creates new problems during both damage analysis and the repair process. Some advanced high strength steels that are now being used are extremely strong with tensile strengths well beyond 150,000 PSI, but the manufacturing process may also make them heat sensitive, creating new repair limitations. Because the steel is heat sensitive, the manufacturers are very particular about where the rails should be sectioned or if they can be sectioned at all. Many vehicle makers do not recommend any sectioning or heating of their frame rails because it may alter their engineering design. If sectioning is recommended, the location, joint type and method is very specific. This is to avoid cutting through laser welds or reinforcements, overheating steels, or changing crush characteristics. In most cases we have no way to visibly identify where the vehicle maker intended the rail to crush and absorb energy or remain rigid and transfer energy. This is why “general sectioning guidelines” are seldom relevant.

Collision damage in the past would cause visible buckles in the frame rail, rearward of the front crush zone, usually in the kick-up area. Because the frame rails are being made stronger and more rigid rearward of the initial crush end, damage travels deeper into the vehicle structure where it can’t be seen. Now, areas like the cowl or floor are likely to collapse, making the damage impossible to identify without measuring. The rigidity of the rail may also cause the structure to deform in unexpected ways. As a result, technicians may need to enhance traditional pulling procedures. Many times simply pulling the damage out in the opposite direction in which it was created, does not correct the structure. More complex pulling plans and multiple-point pulls will be more common. For example, a single pull on a shortened rear frame rail may not simultaneously bring out the buckles in the quarter panel, as it has done in the past. This can make damage analysis difficult and extend cycle times if damage is missed. Just being aware of this problem helps, but more extensive teardown and three-dimensional measuring should be common practice. If proper measuring is not performed, secondary damage may not be identified until parts are assembled or a wheel alignment is attempted. At this point, it is difficult to go back and make structural repairs and the customer has probably been promised a completion date. It’s difficult to explain to the customer that you, as a collision expert, incorrectly diagnosed the structural damage and need to correct it at the end of the repair process. It’s even more difficult to explain to the insurance company that a nearly completed repair may now have crossed the total loss threshold. The vehicle may also be refinished at this point and there will be potential for damage to the fresh paint and corrosion protection.

When inspecting damage, keep in mind the engineering principle the vehicle manufacturers are following when building cars; absorption in the softer front portion of the rail and transfer in the rigid rearward portion. Remember; just because there are no visible buckles in the rearward portion of the rails doesn’t mean there is no secondary damage. It may mean that the secondary damage has been transferred further into the vehicle structure where it is impossible to identify without accurate measuring. Be on guard because what appears to be minor damage could be more severe upon further inspection.

The way vehicles are built has changed, so take the time to measure and inspect thoroughly, it will spare you headaches later in the repair process. Do not rely on visible damage indicators alone, and always assume that there is secondary damage until you prove otherwise. The proof is in the measuring.