ISO 10113:2006及 GB/T 5027-2007规定,对于不均匀塑性应变材料,采用线性拟合回归方法测试塑性应变比,并设定必须通过原点的边界条件。分别采用单点法、过原点线性回归法(设定截距为0)及常规线性回归法(不设定任何边界条件)3种测试方法计算分析了均匀塑性应变材料和不均匀塑性应变材料的r值,并进行比较,探讨了线性回归法设定边界条件的合理性。结果表明:对于均匀塑性应变材料,单点法、过原点线性回归法和常规线性回归法均可准确地分析其r值;对于不均匀塑性应变材料,只能采用常规线性回归法分析其r值,而不能采用单点法和过原点线性回归法分析其r值。

Based on ISO 10113:2006and GB/T 5027-2007,analyzing the plastic strain ratio r-value of non-homogeneous plastic strain materials should use linear regression method,and the regression line fitted must bethrough the origin as the boundary condition.In this paper the r-values of homogeneous plastic strain material andnon-homogeneous plastic strain material were calculated by three different methods including single strain pairsmethod,linear regression method with the regression line through the origin(set intercept being 0)and conventionallinear regression method(dont set any boundary condition),and comparisons of these three methods were done.Atthe same time,the rationality of setting boundary condition for linear regression method was discussed.The resultsshow single strain pairs method,linear regression method with the regression line through the origin andconventional linear regression method all could be used to analyze the r-value accurately for homogeneous plasticstrain materials,but for non-homogeneous plastic strain materials,the r-value could only be analyzed by usingconventional linear regression method,and the single strain pairs method and linear regression method with theregression line through the origin could not be used.