The crystal plasticity constitutive model is developed to investigate the role of solid-solid phase transformation on the deformation mechanism of the HMX single crystal,with accounting for nonlinear elasticity,crystalline plasticity and temperaturecontrolled phase transition (β→δ phase transition).The phase transition of HMX at various heating rates was simulated using a finite element software ABAQUS and a subprogram VUMAT.It shows that the phase transition is reversible,while the paths forβ→δand δ→β transitions are different from each other.Residual strain and stress occur when the crystal converts back into theβ phase.In addition,cracks are generated during theβ→δ phase transition,and maintain after the δ→β phase transition.Moreover,the temperature homogenization can facilitate the phase transition,and the propagation of the phase transition and the heating proceed in a same direction.Furthermore,theβ→δ phase transition can lead to crystal expansion.Because the thermal expansion coefficient of the δ phase is larger than that of theβ phase,the crystal volume is expanded more quickly after theβ→δ phase transition,causing a rapid increase in internal stress and slipping.Due to the anisotropic thermal expansion of the HMX single crystal,cracks occur most readily along the third principal axis after the phase transition,resulting in ready formation of hot spots.Therefore,the β→δ phase transition makes the HMX crystal more sensitive to cook-off.%为研究奥克托今(HMX)单晶的固态相变对变形的影响,在考虑非线弹性和位错理论的晶体塑性本构基础上,发展了考虑温度相关相变的晶体塑性本构(β→δ相变).利用有限元计算程序ABAQUS和子程序的软件代码VUMAT,模拟了相变在烤燃下的演变过程.结果表明,相变是可逆的,但是路径却不同.当晶体从δ相变为β相时,样品中有残余应力和应变产生.此外,当发生β→δ相变时,会有裂纹产生,并且裂纹不会消失.温度均匀化有利于发生相变,且相变的传播与温度的传播一致.β→δ相变会导致体积的膨胀,且由于δ相的热膨胀系数比β相大,相变后体积膨胀会更快,因此会导致内应力的快速增大,从而启动滑移系.由于HMX单晶的各向异性热膨胀,相变后晶体在第三主方向上更容易生成裂纹,从而容易形成热点,因此β→δ相变会导致HMX晶体在烤燃下更加敏感.
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