Controlling the Damage Evolution in Roll Forming of a V-Section by Elastomer Rollers

Elastomer rollers are added to the conventional roll forming process to produce V-sections with reduced damage and increased product performance. This performance of high strength steel profiles during service-life is affected by ductile damage, which can be defined as the nucleation, growth and coalescence of voids on a microscopic level. Damage evolution during forming can be controlled by the stress state. In this work, the stress state during roll forming of a DP800 sheet to a V-section is altered by compressive stress superposition using elastomer rollers. Those are placed between steel rollers creating contact in the otherwise contact-free main forming zone at the outer fiber. The influence on the stress state during forming is investigated numerically, as it depends on the properties of the elastomer. For validation, parts are manufactured in an experimental setup of a five-stage roll forming process with and without elastomer rollers. To determine the influence on damage evolution, the void area fractions in the outer fiber of the bent parts are examined by SEM images. The effect of changing the damage evolution on the product performance of the V-sections is shown by stiffness tests and the analysis of the remaining formability after roll forming.