Location Considerations
An additional consideration when determining if general sectioning guidelines should be applied is the location of the part and its design intent. The front and rear of the vehicle are designed to absorb collision energy. Before choosing to section a lower front rail without the support of a vehicle maker recommendation, first consider what effect sectioning will have in that area. Consider what type of steel is used in the area where the proposed sectioning would be. Also consider which type of joint will be used and if an insert will increase the strength of the part in that area.

Pillars and rocker panels are designed to transfer collision energy around the passenger compartment in frontal collisions and to limit passenger compartment intrusion during a side-impact collision. The pillars and roof rail are also designed to withstand substantial weight in the event of a rollover.

With the upcoming FMVSS roof crush requirements and the desire for “five star” side-impact ratings, the vehicle makers are using a significant percentage of HSS and UHSS in the pillars and rocker panels. While a pillar or rocker panel may offer a smooth and continuous area, there is most likely a combination of reinforcements and AHSS in those areas. Additionally, many vehicle makers offer sectioning procedures for outer uniside panels. However, some vehicle makers may not allow side aperture reinforcements to be sectioned because of the steel they are made from and may recommend replacement at a factory seam. All of these factors combined limit the use of general sectioning guidelines in those areas.

Depending on the type of vehicle, rear rails may be one area that may still qualify for sectioning when applying general sectioning guidelines in cases when no vehicle maker recommendations exist for or against doing so. Additionally, complete rear rail replacement can be an extremely intrusive repair option. Applying general sectioning guidelines to a rear rail when no vehicle maker procedures exist would be a subjective business decision.

Cutting Access Windows
Several vehicle makers have developed sectioning procedures for reinforcements that include cutting and removing a portion of an outer body panel, sometimes called a “window” to allow access to an inner reinforcement for sectioning. However, some technicians have adopted the practice of cutting access “windows” in enclosed structural assemblies to access the backside of damaged panels to allow for more effective straightening of damaged structural parts.

Questions repeatedly arise about whether cutting “windows” is an acceptable collision repair practice. Cutting windows into a part to allow access for straightening may actually be more intrusive than sectioning to partially replace a structural part. This is because partial part replacement using sectioning typically only creates one sectioning joint that is closed with a continuous GMA (MIG) weld.

A “window” can have as many as four cut sides creating two sets of parallel seams that must be welded shut with continuous GMA (MIG) welds, creating open butt joint seams that need to be finished to be cosmetically acceptable. This creates large heat-effect zones in the part and adjacent areas, and if the part is made from heat-sensitive steel, the part can be negatively affected from the welding heat.

Conclusion

The materials and construction design technologies that are being used on today’s vehicles are making it increasingly difficult, if not impossible, to apply general sectioning guidelines. In addition to the criteria that have been used for over twenty years, the collision repair industry professional is also now tasked with considering the design intent and determining the steel makeup of the part. All of this makes the decision to apply general sectioning guidelines more subjective than ever.

Fortunately, the number of vehicle makers offering partial replacement recommendations has increased significantly over the past few years. I-CAR will continue to work closely with the vehicle makers and encourage the continuation of this trend.

I-CAR is also committed to continually report on the availability of partial replacement procedures. We will update the partial replacement matrix on a regular basis, report on new technology through the I-CAR Advantage Online, and develop and deliver applicable training to address new vehicle technology.

This Advantage Online article first appeared in the I-CAR e-newsletter, which is published and distributed free of charge. I-CAR, the Inter-Industry Conference on Auto Collision Repair, is a not-for-profit international training organization that researches and develops quality technical education programs related to collision repair. To learn more about I-CAR, and to subscribe to the free e-newsletter, visit http://www.i-car.com or contact I-CAR Supervisor of  Marketing Communications Brandon Eckenrode at This e-mail address is being protected from spam bots, you need JavaScript enabled to view it