摘要：板材成形过程中复杂加载路径的改变会影响其弹塑性流动行为。以超高强钢淬火—配分（quenching&partitioning，Q&P）980钢为研究对象，在室温下沿着轧制方向的不同角度进行2步拉伸实验，得到不同应力状态下的应力—应变曲线，并根据单位体积塑性功相等原则，确定了板材不同等效塑性应变（0%、1%、4%、6%）下的实验屈服轨迹。结果表明：在应变路径变化上，初始流动应力显著降低，特别在45°和90°方向上，瞬时时段之后的流动应力存在持续的偏移，较大应变条件下各向异性比较明显。实验屈服轨迹呈外凸性，部分屈服轨迹不对称，随变形程度的增加，屈服轨迹向外扩大。通过对比简单加载和循环加载，分析其弹塑性行为，并建立各自的卸载弦数学模型，指出弹性模量随应变的增加而降低，降低到一定程度后趋于平缓。在相同塑性应变下，循环加载时弹性模量的变化值比简单加载时要大。

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.