应力波载荷作用下材料断裂韧性JId测试研究

摘要

An experimental method for measuring dynamic elastic-plastic fracture toughness is established. The Charpy impact specimen is loaded by an improved Hopkinson pressure bar. The incident and reflected stress waves, which are recorded by strain gage glued onto the pressure bar, are used to calculate the loads and deflection of specimen according to the one-dimensional stress wave theory. The method can be applied in extremely low and high temperature conditions. The material's dynamic stress-strain behaviors are taken into account in calculating the dynamic elastic-plastic fracture toughness. So the JId value can well reflect the dynamic fracture properties of metals under stress wave loading.%本文建立了一个测定动态弹塑性断裂韧性JId的方法。该方法利用改进的Hopkinson压杆加载Charpy冲击试样，利用压杆上应变片记录的入射应力波和反射应力波，由一维应力波理论得到试样所受的载荷和加载点位移。在建立的裂纹尖端张开位移COD和裂纹扩展量Δa的关系中，令Δa=0，可得到裂纹起裂时的临界（COD）c从而确定裂纹的动态起裂点。与其它方法相比，本文的方法不需要昂贵的仪器来测试动态断裂参数；不需将应变片贴在试样上确定起裂时间，所以该方法可在较高或较低的温度下使用；在动态弹塑性断裂韧性JId的计算中，考虑了材料的动态应力—应变行为，使测得的JId值能更好地反映材料在应力波载荷作用下的动态断裂性能。