Design tips, techniques for stamping BIW

How do you design a sheet metal part to deliver good body structures performance?

If you are looking for a single and magical response, sorry; it doesn’t exist. But some design best practices often help to achieve the expected body structures performance and prevent potential problems.

  1. How to Manage Stress and Strain?
    No matter the vehicle architecture, body structure designers and engineers always encounter two “bad guys”: stress and strain. Whether you are an experienced or novice automotive designer, you are probably seeking ways to deal with stress and strain.

Some attribute problems can be managed by using different material grades and thicknesses. The shape also plays an important role in achieving a performance target and should be also part of solution—even more when you are working to deliver durability and safety performance.

Following are key design best practices to help you mitigate potential performance problems, avoiding stress risers and concentrators around your design: 

  • Always use the largest radius possible, including the bending radii. Don’t forget the mating surfaces surrounding your parts. Don’t use sharp corners in any square hole, notch, or slot. They will create performance flaws. In addition, the toolmakers will hunt you down before rejecting your design.
  • All design section transitions should be smooth, tangent, and gradual. Avoid abrupt section changes if you don’t want to end up with cracks.
  • Do your best not to design multiple stress riser features in the same surface plane. Admittedly, sometimes you have no other options because of other systems’ interfaces.
  • Add beads and darts only when they are required for stiffness or springback control. The bad guys (stress and strain) are hiding behind these little features to crack your part.
  • Joint and spot weld distribution are also quite important to balance the tensile loads around the parts and systems. Always consider improving the joints to spread the stress around the parts.
  • Bear in mind that you may always have some correlation gaps when going from virtual to real phases. In other words, even if a problem isn’t found during virtual analysis, that doesn’t mean one won’t appear during physical validations. That’s why you need work in all ways to mitigate potential problems in your design.

It’s always best to avoid stress concentration points for all parts and joints in your design—from the first sketch. This will help save money and time.

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