复杂应变路么对板料屈服强化、成形极限影响规律的研究

To establish the true description of the influence of anisotropy and work hardening, realize expediently the experimental method of variable loading paths, study systematically the effect of different loading paths on yield behavior and forming limit of metal sheets, and estimate the accuracy and applicability for theoretic yield criterion and forming limit, are all along emphases and difficulty problems in the fields of mechanics, materials science and sheet metal forming..Through the research on this item, the hardware and software systems of biaxial tensile test of cruciform specimen are built, the synchronous control of load and displacement in the same axial jaws and the process control of the non-proportion and double linear loading are realized, and the cruciform biaxial tensile test method for realizing expediently the complex loading paths is put forward. The cruciform specimen with narrow slot in arm region is put forward for yield behavior analysis, the stress-strain curves in center region are determined under different loading paths, the yield loci under different deformation phase are obtained based on the plastic work principle, the anisotropic yield behavior is studied, and the applicability for theoretic yield criterion is estimated. The cruciform specimen with chamfer in arm and center region is put forward for tensile instability analysis, the limit strains under the complex strain paths are realized in center region. The cruciform specimen with improvement at circle corner is put forward for pre-strain loading analysis, the different pre-deformations of sheet metal are realized under different strain paths, the forming limit is determined under double linear strain paths.The above achievements provide the test means for the study of plastic yield behavior, forming limit and the effect law under complex loading paths. Also, these achievements provide the basis for the establishment of reasonable plastic law and forming limit, the accurate analysis of plastic forming process of sheet metal, and the development of theory of plasticity..

设计满足应力与变形程度要求的十字形试件，实现复杂加载路径控制，建立十字双向拉抻试验法。确定无卸载非比例加载、双线性加载等不同应变路径下板料初始与后继屈服轨迹、成形极限图，确定复杂应变路径对各向异性板料屈服强化行为、成形极限的影响规律，建立准确的解析模型及实用判据，为精确解析板料成形过程，丰富与发展板料塑性理论奠定基础。