Finite Element Simulation Of ASB In Fine-grained Tungsten Alloy Under Impact Loading

Split Hopkinson Pressure Bar Test(SHPB) is used to study the dynamicc mechanical property of conventional coarse-grained tungsten heavy alloy(WHAs)93W-4.9Ni-2.1Fe and two fine-grained93W-4.9Ni-2.1F-0.03Y with different grain size at the a wide range of strain rates(102～103s-1) and temperatures(298K～623K). Finite element simulations are carried out for the defotmation and instability of cylinder tungsten heavy alloy(WHAs) specimens subjectied to impact loading. A two-dimensional axis-symmetric adiabatic model is introduced in the simulations and a modified Johnson-Cook(JC) model was proposed to describe the dynamic behaviors of the studied WHAs. The initiation and propagation of adiabatic shear band (ASB) were investigated, including the grain size and yttrium contained effects on the sensibility to ASB.According to experimental datas, a modified Johnson-Cook constitutive equations were fitted out and the fitting is better than the original Johnson-Cook model,with maximum relative error-3.4%Comparing the constitutive parameters of three fine-grained tungsten heavy alloys, fine-grained tungsten alloy is considered to be possible to form adiabatic shear band(ASB).The results of simulation at1100s-1show that the stress reaches the maximum value and stress collapse occurs, subsequently the stress decreases to over80%of the peak value, ASB was observed, and no crack was observed. When the strain rate is above2340s-1, crack was observed in the ASB, and with the propagation of stress wave, matrial came to failure. The ASB forming in the fine-grained WHAs and93W-4.9Ni-2.1Fe shows little difference at high temperature.Comparing the constitutive parameters of three fine-grained tungsten heavy alloys, fine-grained tungsten alloy is considered to be possible to form adiabatic shear band(ASB).