【摘要】 指出Johnson-Cook(J-C)、Zerilli-Armstrong(Z-A)、Bodner-Parton(B-P)本构方程在一定条件下的适用性,表明对于低压、高应变率实验,单一曲线假定似乎可以采用。通过等效应力、等效应变,可以将不同应力状态下的流动应力函数采用统一的方程描述。然而,这些本构方程的确立,并不包括平面冲击波实验。对适合于平面冲击波实验的Steinberg-Cochran-Guinan(SCG)本构方程,讨论了其方程中所包含的高压与高应变率耦合效应。指出,以剪切模量度量的流动应力具有应变率相关性。基于温度效应的新发现以及直接测量平面冲击波流动应力的新进展,分别用J-C本构及SCG本构方程估算了钨材料在高压、高应变率加载下的流动应力。结果表明,采用J-C本构估算的流动应力仅在压力为10 GPa以下才能与实验数据相近,当压力高于10 GPa时,流动应力只能采用SCG本构估算。也指出了高压、高应变率本构方程与低压、高应变率本构方程所对应的不同物理背景。更多还原

【Abstract】 It is indicated that the constitutive equations at high strain rates proposed by Johnson-Cook(J-C),Zerilli-Armstrong (Z-A) and Bodner-Parton (B-P) collapse the data of flow stress in compression,tension,torsion,and shear into simple curve with the scalar quatities ’effective’ stress and ’effective’ strain,however,the collapsed data of flow stress did not include the data in the planar shock wave tests.The SCG constitutive equation proposed by Steinberg et al for the planar shock wave tests is discussed,which describes the coupled high pressure and high strain rate effects on the plastic deformation of materials.Basing on the recent experiments at elevated temperatures and high strain rates and the shear strength measurements during shock loading,the flow stress for tungsten at high pressure and high strain rates is estimated with J-C and SCG constitutive equations,respectively.It is concluded that the J-C,Z-A and B-P constitutive equations may not be appropriate to describe the plastic behavior of materials at high pressure and high strain rates,comparing with SCG constitutive equation. It is emphasized that the physical background of the constitutive equation at high pressure and high strain rates is different from that at low pressure and high strain rates.更多还原