Residual stress problems in windshield bending can be hard to solve. Sometimes measurement devices are not available, or device capabilities limit the investigation.

When I’m working on trouble shooting projects, selection of alternative testing methods is vital. With residual stress problems these are abrasion and scribe (scratch) tests. These tests indicate for example excessive surface tensile stress condition which causes glass breakages. Do you have these tests in your “toolbox”?

Required countermeasures depend on processing conditions, commonly “the recipe” is multiple adjustments to both bending process and mold tooling.

By the above testing, the tested windshiled would crack/breaks if excessive/over the threshold tensile stresses are present in the surface of the glass at the point(s) where the surface is damaged. In this case the near edge regions of the glass. Tensile stress “pulls the crack to open” potentially causing failure, whereas compression “prevents” failure.