真应力-应变的定义及其力学特征

Definition and Mechanical Characteristics of True Stress-Strain

材料的真应力和真应变与常用的工程应力 应变有明显的差异 ,作者从真应力和真应变的定义出发 ,论述了塑性材料在轴向拉伸条件下变形过程的力学行为 ,阐明了应变硬化、最大均匀真塑性应变、应变硬化指数的相互关系。真应力 应变曲线直观地反映了材料拉伸变形时的应变硬化行为 ,其数学表达式为Hollomon公式。由拉伸实验得到的logσ logε曲线的斜率即为应变硬化指数 ,其数值与材料拉伸变形时的最大均匀应变相等 。

A significant difference between the true stress & strain and the engineering stress & strain has been observed. Based upon the definitions of true stress and true strain, the mechanical behavior of plastic materials during the process of axial tension deformation is discussed. The strain hardening phenomenon, the maximum uniform true strain, the strain hardening coefficient and their interrelationship is analyzed. The true stress-strain curve obtained from tension tests indicates directly the strain-hardening characteristic during the tensile deformation, which may be expressed mathematically with the Hollomon formula. The value of strain-hardening coefficient can be determined from the slope of log σ- log ε curve, which is numerically equal to the maximum uniform true strain. So the strain-hardening coefficient can be used to evaluate the extend of uniform plastic deformation.