Abstract：The loading paths used for sheet metal forming affect its elastic-plastic flow behavior. Quenching & partitioning (Q&P) 980 steel was used here as the research object. Two-step tensile tests using different angles relative to the rolling direction were conducted at room temperature to obtain the stress-strain curves for various stress states. The equal volume plasticity work principle was used to determine the experimental yield loci of different equivalent plastic strain (0%, 1%, 4%, 6%). The results show that the initial flow stress is significantly reduced by changing the strain path, especially in the 45° and 90° directions, the flow stress after the transient period various by a fixed amount, and the anisotropy is quite large for larger strains. The test yield loci line is convex and some of the yield loci are asymmetric. As the deformation increases, the yield loci expand outward. Simple loading and cyclic loading were compared to analyze the elasto-plastic behavior and develop unloading string mathematical models. The elastic modulus decreases quickly with increasing strain, then decreases slowly and then becomes constant. For a given plastic strain, the change in the elastic modulus during cyclic loading is greater than when simply loaded.
韩飞, 操召兵. 复杂应变路径下Q&P980超高强钢的非弹性回复行为[J]. 清华大学学报（自然科学版）, 2018, 58(10): 921-928.
HAN Fei, CAO Zhaobing. Inelastic recovery of Q&P980 ultra high strength steel with a complicated deformation path. Journal of Tsinghua University(Science and Technology), 2018, 58(10): 921-928.
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