Effect of Tensile Properties on Dent Resistance of Sheet Steels

The dent resistance of AKDQ, bake-hardenable, and IF Re-phosphorized sheet steels in both the as-received and biaxially prestrained conditions were evaluated. A laboratory dent test system for evaluating flat 76.2 mm diameter samples was designed and adapted to a standard universal test frame. Dent testing consisted of measuring the loads and displacements associated with the incremental quasistatic penetration and withdrawal of an indenter into the center of a circular sheet sample mechanically restrained at its perimeter. Dent resistance was characterized by a critical amount of residual displacement. Both experimental measurements and theoretical predictions demonstrate an increase in dent resistance with prestrain up to a maximum followed by a decrease due to thinning. Correlations between dent resistance, tensile properties, and the strain within the dented region indicate that the dent performance depends on the low strain, strain hardening behavior of the material.