考虑韧性损伤的Ti6554电塑性本构模型建立及应用

Establishment and application of electroplastic constitutive model of Ti6554 considering ductile damage

建立了修正Johnson-Cook电塑性本构模型,使用FORTRAN语言开发了用户硬化子程序UHARD,并耦合指数形式的韧性损伤断裂准则,使用ABAQUS有限元软件进行了数值模拟。为验证本构模型与有限元模型的合理性,设计了脉冲电流辅助单向拉伸实验,通过控制脉冲电源的频率、占空比以及试验机的拉伸速度,分别在12、13和15 A·mm^(-2)电流密度下对Ti6554试样进行拉伸,直至断裂。结果表明,模拟与实验的载荷-位移、温度-时间曲线吻合情况良好,试样在15 A·mm^(-2)电流密度下的流动应力较小,温度攀升较缓,颈缩区域更广,颈缩现象提前发生,材料刚度退化最慢,最后通过扫描电子显微镜观察了3种电流密度下试样的断口形貌,发现试样均为韧性断裂。

The modified Johnson-Cook electroplastic constitutive model was established,user hardening subroutine UHARD was developed using FORTRAN language,the exponential ductile damage fracture criterion was coupled,and the numerical simulation was carried out using ABAQUS finite element software.To verify the rationality of the constitutive model and the finite element model,pulsed current assisted uniaxial tensile experiments were designed.By controlling the frequency and duty ratio of the pulse power supply and the tensile speed of the testing machine,the Ti6554 samples were tensioned until fractured at the current density of 12,13 and 15 A·mm^(-2),respectively.The results show that the load-displacement and temperature-time curves of the simulation and experiments are in good agreement.With the current density of 15 A·mm^(-2),the flow stress of the sample is small,the temperature rises slowly,the necking area is wider,the necking phenomenon occurs in advance,and the stiffness degradation of the material is the slowest.Finally,scanning electron microscope(SEM)was used to observe the fracture morphologies of the samples with three kinds of current densities,and it is found that the samples are ductile fracture.