The reinforcement of this B-pillar from a Buick Enclave is made from DP 980, which is UHSS but it is spot-welded to an HSLA
reinforcement.
Determining whether to repair or replace a damaged part is a decision made daily in collision repair facilities and estimating
bays.
Because of the number of variables that exist between damaged vehicles, it is difficult to establish firm "black or white"
rules that would not be excessively restrictive. That is why it is actually better to become familiar with all of the issues
involved with structural parts to make the best decisions on a case-by-case basis.
This damaged part has the potential to be made from several different kinds of HSS as well as mild steel and other materials.
A growing number of vehicles use a variety of materials in their structures. The criteria for determining whether a part should
be repaired or replaced can vary greatly depending on the material in the part and the part structure. The focus of this article
will be on steel parts and steel structures.
Material matters
Kinked parts, like this, have a sharp bend with a small radius, usually more than 90 degrees over a short distance (about
3mm).
I-CAR has always recommended following OEM recommendations when doing collision repairs, but when it comes to the decision
on whether a part can be straightened or whether it should be replaced, many vehicle makers tend to leave that decision up
to the collision industry. Making this decision carries a great deal of responsibility due to safety implications and liability
exposure. A collision-damaged vehicle must be repaired to the original level of safety the vehicle was designed for.
To better understand how to make the best repair decision, we need to know exactly why new materials and designs are being
used. The challenges to the automotive manufacturing industry today are significant. Consumers expect an increasing array
of convenience, infotainment and safety systems, along with improved performance and increased fuel economy without giving
up vehicle size. They also want safety. Car buyers look for "Five-Star" crash protection.
The reinforcement for the B-pillar of a Buick Enclave is made from DP 980, an UHSS but is spot-welded to an HSLA reinforcement.
Replacing the HSLA part does not involve welding directly onto the UHSS, thereby maintaining the integrity of the UHSS reinforcement.
Incorporating all of these features adds a lot of weight to a vehicle. Overall vehicle weight is trending heavier rather than
lighter. To keep vehicles from getting too heavy, automakers offset added weight from vehicle systems by reducing the weight
of the body structure. Hence, automakers actually engage in weight mitigation, or weight control, rather than weight reduction.
The new steels used today are not actually lighter. They are much stronger. Some of the ultra high-strength steel (UHSS) being
used today can be four times the strength of the mild steels that were used in the past. This allows stamped parts to be made
thinner, which reduces the weight of the part.
Note, however, that in some areas of the vehicle, parts are not being made thinner. They actually may be made thicker, even
with the use of high-strength steel (HSS) and UHSS. This may be done to improve rigidity and increase side-impact and rollover
protection. That's where some of the weight is added back into the structure.
I am the Project Manager for the UK's Leading Trade Association for Body Repair. I read your article with interest, and can confirm much of what you say, I have been researching this in behalf of our members since October 2001. The UK has had mas produced cars using UHSS, AHSS & VHSS since September 2001. We advise our members on the correct repair methods and training for the new materials, including UHSS Awareness and GMA (MIG Brazing) Training. If you wish I can send you my recently updated overview document for your attention and interest. Gerry Braddock AAE, Hon. FIMI, I.Eng, MSOE, MIRTE Project Manager
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Posted Jun 30 2009 04:01AM
