板料成形极限应变与极限应力的转换关系

Transformation Relation between Limit Strain and Limit Stress in Sheet Metal Forming

因极限应变构成的FLD受应变路径的影响很大 ,在研究复杂应变路径的成形极限问题时带来极大不便。而以极限应力构成的成形极限应力图FLSD由于不依赖加载应变路径 ,已成为目前研究的热点。本文在分析板料极限应变与极限应力的基础上 ,得出了相互转换的公式 ,针对分散性失稳、凹槽失稳和平面应变漂移失稳等准则 ,进行了不同加载应变路径FLD转换FLSD。结果表明 ,对于同一失稳准则 ,在不同加载应变路径下FLSD几乎为同一条曲线 ,FLSD作为复杂加载路径板料成形极限判据更加方便。

Strain-based FLD is strongly affected by the strain path and has brought much inconvenience to the study of forming limit under complex strain paths. While FLSD, which is stress-based and independent of strain path, has become the hotspot in this field. Transformation formulas are given on the base of analysis of limit strain and limit stress. Transformation between FLD and FLSD under different strain paths were obtained according to diffuse instability theory, groove instability theory and plane strain floating instability theory. The result shows that the FLSD under different strain paths are almost the same curve according to the same instability theory and its more convenient to use FLSD as the criterion of forming limit.