铜基粉末冶金多孔材料在高应变率下的力学性能及本构关系

MACHENICS PROPERTIES AND CONSTITUTIVE EQUATION OF CU-MATRIX POWDER METALLURGY (PM) POROUS MATERIAL AT HIGH STRAIN RATES

通过实验得出铜基粉末冶金摩擦材料在高应变率下的应力应变曲线 ,建立该材料的本构模型。在分离式Hopkinson压杆 (SHPB)上进行了该材料在 10 2 s～ 10 3 s应变率范围内的冲击试验 ,弹速范围为 4m s～ 15m s ,在透射杆上采用半导体应变计技术 ;在MTS实验机上做了该材料在 10 - 4 s～ 10 - 3 s应变率范围内的准静态实验 ,分别在应变为0 0 0 5、0 0 1、0 0 2、0 0 3 5时卸载再加载 ,以验证该材料的粘弹塑性特征。通过分析动态和静态实验曲线 ,发现该材料在应变率 3 0 0 s和准静态时有应变硬化效应 ,但在 5 0 0 s以上却反映出应变软化效应 ,得出该材料为含损伤非线性粘弹塑性材料 ,故提出用适应于脆性材料的粘弹塑性模型和粘塑性项的组合本构模型来拟合该材料应变弱化段的本构方程。所得结果可推广应用于类似烧结合金的材料。

Based on the dynamics stress-strain curves of Cu-matrix powder metallurgy(Cu-PM) at high strain rate, a numerical constitutive equation is proposed. The dynamic compression tests are made at strain rate 10 2/s～10 3/s by Split Hopkinson Pressure Bar(SHPB), with bullet speed of 4*!m/s～15*!m/s. During the dynamic compression test, the measurement technology of semiconductor gage is suggested on the transmitted bar. The quasi-static test are made at strain rate 10 -4/s～10 -3/s by MTS machine. Unload and reload are conducted at strain 0.005, 0.01, 0.02, 0.035; show the material properties of visco-elastic plastics. By analysis the state and dynamics curves, the harden effect is shown under 300/s and quasi-static load, but the negative strain-rate effect is observed at high strain rate (more than 500/s). The damage weakening mechanism resulted from a rate-dependent evolution of cracks are discussed, it is impossible to take place the adiabatic shearing at high strain-rate for Cu-PM,proving that Cu-PM is a visco-elastic-plastic material with damage. A visco-elastic-plastic model for fitting the load curve at high strain rate is proposed. It fills up the blank of the dynamic data for PM material and supplies the credibility experiment data for the engineering application.