Numerical Simulation of Adiabatic Shear Behavior of TC4 Titanium Alloy
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摘要: 基于Johnson-Cook本构模型和损伤模型，采用Lsdyna软件建立了分离式霍普金森压杆系统的二维模型，对TC4钛合金帽状试样的绝热剪切过程进行了数值模拟，研究了局域化变形区域的应力、塑性应变和温度，并与试验结果进行对比；探讨了TC4钛合金的绝热剪切机理。结果表明：模拟得到13 m·s-1冲击速度下，TC4钛合金帽状试样发生明显的局域化变形，且局域化变形区域的最大应力为1 530 MPa，断裂极限塑性应变为0.205，最高温度为344.3 K；局域化变形区域中等效塑性应变较高的区域与温度较高的区域均呈扭转的漩涡状分布特征，且二者的位置相同，该区域形成了绝热剪切带。模拟得到帽状试样的真应力-真应变曲线以及绝热剪切带形成的位置与试验结果均吻合，验证了模拟结果的准确性。TC4钛合金绝热剪切带组织为明显的等轴晶组织，绝热剪切带组织与α基体组织间存在明显的分界线。Abstract: Based on John-Cook constitutive model and damage model, the two-dimensional model of split Hopkinson pressure bar system was established by Lsdyna software. The adiabatic shear process of TC4 titanium alloy hat-shaped sample was simulated. Stresses, plastic strains and temperatures of the localized deformation area were studied and compared with test results. The adiabatic shear mechanism of TC4 titanium alloy was discussed. The results show that at the impact velocity of 13 m·s-1, localized deformation phenomenon was obviously observed in the TC4 titanium alloy hat-shaped sample; the maximum stress in the localized deformation area was 1 530 MPa obtained by simulation and the fracture limit plastic strain was 0.205, and the maximum temperature was 344.3 K. The region with relatively high equivalent plastic strain and the region with relatively high temperature in the localized deformation area had vortex distribution feature, and the location of the two regions was the same; the adiabatic shear band was formed in this region. The simulated true stress-true strain curve of the hat-shaped sample and the formation location of the adiabatic shear band were both in good agreement with the test results, which verified the accuracy of the simulation. The adiabatic shear band structure of TC4 titanium alloy was obvious isometric crystal structure, and there was a clear dividing line between adiabatic shear band structure and α matrix structure.
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Keywords:
- TC4 titanium alloy /
- hat-shaped sample /
- numerical simulation /
- adiabatic shear
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