Study on the Dent Resistance of Warm Forming HSS Parts with Free-Form Surface

Abstract

Recently, due to the harsh demands for automobile lightweight and safety, more and more attention is focused on the warm forming process of various high strength steel sheet. In the present work, aiming to the formed parts safety problems caused by elevating temperature, take B340/590DP steel as the research object, the dent resistance of the warm-forming parts with free-form surface is studied. Firstly, combing the warm tensile tests under various conditions with the secondary room temperature tensile tests, a secondary yield constitutive model is established for the researched material by the regression analysis method, which reveals the influences of temperature, strain rate and pre-deformation on the secondary yield behaviors. Secondly, based on the plastic deformation theory and the free-form curves and surfaces theory, a dent resistance evaluation system is proposed for the warm-forming high-strength steel parts with free-form surface. Finally, design a dent resistance model experiment, validate the dent resistance of the warm-forming B340/590DP steel specimens, and determine the relevant coefficient value in the proposed dent resistance evaluation system by means of the obtained experiment data. The research results can be used directly to select the reasonable warm-forming process conditions, control and improve the warm-forming parts quality and performances.