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为了合理描述单向拉伸试验曲线,给出了一种修正的Swift型流动应力—应变关系。基于两种流动应力—应变关系,采用Yld2000-2d屈服准则计算5754O铝合金板的成形极限应变图(FLD-strain)。通过对比理论和实验结果,发现基于修正的Swift型的应力—应变关系所计算的FLD-strain能够合理地描述实验结果。虽然常用的Voce型应力—应变关系能够精确地描述均匀变形阶段的变形行为,但基于该应力—应变关系计算的FLD-strain明显低于实验结果。结果表明,板料的强化率越高则相应的成形极限也越高。为了描述板料在非均匀变形阶段的变形行为和成形极限,建议了一种用于确定合理的流动应力—应变关系的方法。
In order to reasonably describe the uniaxial tensile test curve, a modified Swift-type flow stress-strain relationship is given. Based on the relationship between two kinds of flow stress-strain, the forming limit strain (FLD-strain) of 5754O aluminum alloy plate was calculated by Yld2000-2d yield criterion. By comparing the theoretical and experimental results, it is found that the FLD-strain calculated based on the modified Swift stress-strain relationship can reasonably describe the experimental results. Although the commonly used Voce stress-strain relationship can accurately describe the deformation behavior at the uniform deformation stage, the FLD-strain calculated based on this stress-strain relationship is significantly lower than the experimental results. The results show that the higher the sheet reinforcement rate, the higher the corresponding forming limit. In order to describe the deformation behavior and forming limit of the sheet during the non-uniform deformation stage, a method for determining the reasonable flow stress-strain relationship is proposed.