双孔微剪切测定铝合金焊接接头的局部本构特性

Determination of Local Constitutive Properties of Welded Joints in Aluminium Alloy Using Double Holes Microshear Test

铝合金焊接接头存在着力学性能不均匀性,准确测定出不同区域的局部力学性能,对评定整体接头性能和改善焊接工艺是十分必要的。研究了一种双孔微剪切测定局部材料本构性能的新方法。在被测材料的小区域两侧开两小孔,剪切刀具从其中一孔对被测区域的材料加载直到破坏,记录加载过程中的载荷位移曲线。建立这种方法的有限元模型,根据实验的载荷位移曲线,利用反向有限元计算方法得到局部材料的真应力应变曲线。从而测定了铝合金焊接接头热影响区的塑性变形的本构特性分布。测定结果表明,在热影响区的完全固溶区,材料的屈服应力较小,而加工硬化指数较高;在过时效区屈服应力和加工硬化指数都比较低。

Welded joints in aluminum alloy exhibit heterogeneity of mechanical properties.Local properties determination within the different constituents is necessary to improve the material processing,and to numerically evaluate the component performance such as crash simulation.The present work is concerned with a new approach for determining local material constitutive properties of welded joints in aluminum alloy.In this method,drill the double holes in the two sides of the point to be determined in welded joints,load material bridge by an indentor until it is broken,record the response between applied load and indentor displacement.We can call this method as double holes microshear test.According to the load-displacement curve obtained experimentally from the double holes microshear test,the true stress-strain curve of local material was calculated by means of the inverse methodology of finite element computation.The distribution of true stress-strain curves within heat-affected zone was consequently determined for aluminium alloy welded joints.The determination results show that,in the dissolution zones the yield stresses are lower but the work hardening exponent is higher,and in over aging zones both the yield stresses and the work hardening exponent are lower.