研究金属材料高温动态拉伸性能新方法

采用自行设计带有小型加温装置的改进的分离式Hopkinson拉杆装置测试了金属材料在高温条件下的动态拉伸性能,并用修正的Johnson-Cook模型作为材料的本构关系,提出了一种拟合金属材料在弹性及塑性阶段应变率及温度相关的损伤模型,并拟合出参数.结果表明:改进装置能够精确控制加温速率及温度,减小杆端软化的影响,测试结果相对误差小于1.5%;金属材料304不锈钢的屈服应力及断裂应变具有明显的正应变率效应的温度软化效应,但材料弹性模量具有负应变率效应和负温度效应;在293—625K之间计算结果和试验结果吻合较好,表明可用这种方法测试及估算材料高温动态力学性能,并用于工程分析.

New Method for Investigating the Dynamic Tensile Properties of Metallic Materials at High Temperature

The dynamic tensile properties of metallic materials were measured by the improved split Hopkinson bar with small heating device at different temperatures and strain rates.With the help of modified Johnson-Cook constitutive relationship,a damage model describing the strain rate and temperature in elastic and plastic stage was developed.The experimental results showed that by using the improved experiment device,the heating rate and temperature could be controlled accurately,the softening effect of bar end could be reduced,and the maximum relative error was below 1.5%;the yield stress and fracture strain of 304 stainless steel had a kind of positive strain rate effect and temperature softening effect,while the elastic modulus had negative strain rate effect and temperature effect.The agreement of the final computation results with the experimental data at 293—625K indicated this method could be used to measure and estimate the dynamic properties of metallic materials and effectively at engineering analyses.