AZ31镁合金拉伸应变硬化指数的测试

Tensile strain hardening index testing of AZ31 magnesium alloy sheet

针对镁合金板材在拉伸时呈现微型锯齿屈服效应曲线时应如何计算拉伸应变硬化指数n值的问题,采用差分平均法、两点分析法、解析拟合法以及国标线性回归法对AZ31镁合金板材拉伸曲线进行计算,以国标线性回归法所得结果 nline为参考基准,将另外三种方法得出的ndiff、ntwo-point、npoly同nline进行比较。结果表明:用差分平均法、两点分析法和解析拟合法计算的n值非常吻合。解析拟合法得到的结果同线性回归法的结果相符程度最高,误差仅为0.27%,差分平均法次之,为-0.53%,两点法计算误差在1%左右。验证了金属材料拉伸呈现微型锯齿屈服效应曲线时,其n值仍然可用这四种方法计算。当金属材料拉伸均匀塑性变形阶段曲线变化较平稳时,建议优先采用解析拟合法,此时用该方法计算n值既方便又可信度高。

During tensile testing of magnesium alloy sheet, the yeld effect curve appears micro-serrate line. In order to calculate the hardening index n value, the difference average test, two-point analysis test, analytic poly test and international linear regression test have been used for calculating the tensile curve of AZ31 magnesium alloy sheet. Taking the result nline calculated by international linear regression test as a evaluation standard, compared with naiff, ntwo.point and npoly. The results show that the difference average test naiff, the two-point a- nalysis test ntwo-point and the analytic poly test npoly are coincide with each other; but the ana- lytic poly test value and international linear regression test value are coincided the best, its error is 0.27 % only, the different average test error takes the 2nd place, is - 0.53 %, and fi- nally the two-point analysis test error is 1%. All the calculations prove that the n value can be calculated by these four methods while micro-serrate curve of yield effect appears during other metal material tensile testing. However, the analytic poly test is the best choice while the curve line goes smoothly during uniform ductile tensile deformation of metal materials sta- ble, because this calculated n value is high credible and the calculation is more convenient.