| Abstract: | QP980 is an ultra high strength steel. First, uniaxial and biaxial tension tests have been done in different loading paths. Then QP980 basic mechanical properties have been obtained. And the stress and strain graph has been drawn. Second, according to the equal principle of the unit volume plastics work and yield stress, QP980 plastic work contour map has been drawn. Third, through comparing Mises, Hill'48, Hosford and Barlat89 yield criterion theoretical curves with the experimental plastic work contour map, the result shows that the Hill'48 yield criterion is in good conformity with the QP980 material. Fourth, Hill'48 yield criterion is optimized by introducing an equivalent plastic strain parameter. The result shows that average error of optimized Hill'48 theoretical yield trajectory is reduced by 8.4%. Last, finite element model about variable cross-section roll forming is established, then applying the optimized Hill'48 parameter yield criterion to the ABAQUS for finite element simulation. The simulation result shows that the forming quality is good, and in agreement with the actual forming parts. Therefore, the optimized Hill'48 yield criterion can be used to precisely describe QP980 ultra high strength steel. |
