Can you explain the failure behaviors that occur in sheet metal forming?

There are two major failures in sheet metal forming processes, i.e. localized necking and wrinkling.

Localized necking results from too much stretching, and it can be found by comparing the principal in-plane strain components with FLDs, if it is above FLD, then the material fail.

Wrinkling is the result of compressive stress. Because sheet metal usually is very think and it is easy to have wrinkling even with small compressive stress.

Sometimes, even though the strain is safe compared with FLD, however, when then the deformation is close to equi-biaxial stretching, the thickness of the sheet might become excessively thin which is not good for the whole structure of the deformed part. Accordingly, excessive thinning of the sheet should also be avoided.

It is possible to check these failure modes in LSPOST.