TA4纯钛带材各向异性屈服行为表征与研究

Characterization and Study on Anisotropic Yield Behavior of TA4 Pure Titanium Strip

目的 基于复杂加载状态试验和先进屈服准则,实现考虑塑性演化的TA4纯钛在复杂加载状态下塑性各向异性行为的精确表征。方法 通过0°、45°、90°方向的单拉试验和复杂加载比例的十字形试件双向拉伸试验,获得TA4纯钛的基本力学性能参数和拉伸屈服轨迹,采用不同的屈服准则对试验屈服轨迹进行预测,并通过变r值的屈服准则预测其屈服轨迹的塑性演变规律。结果 在小变形范围内,Yld2000-2d屈服准则对TA4屈服轨迹的预测精度最高;塑性变形过程中,呈线性增大趋势的r值与TA4纯钛的屈服轨迹演变现象直接相关。结论 试验与理论屈服轨迹的对比表明,Yld2000-2d屈服准则可以实现TA4纯钛初始屈服行为的精确表征。TA4纯钛带材的r值随塑性变形呈线性增大趋势,考虑塑性演化的Barlat89屈服准则预测的TA4屈服轨迹外凸性更显著。在TA4纯钛带材冲压成形过程的有限元分析、模具设计和工艺优化中,仅考虑初始屈服轨迹时,可采用Yld2000-2d屈服准则;当各向异性特征存在较强的塑性演化相关性时,可采用形式相对简单的Barlat89屈服准则。

The work aims to accurately characterize the plastic anisotropic behavior of TA4 pure titanium considering plastic evolution under complex loading state based on complex loading state test and advanced yield criteria. The basic mechanical properties and yield loci of TA4 pure titanium were obtained through uniaxial tension at 0°, 45° and 90° directions and biaxial tension of cruciform specimen with complex loading ratios, and different yield criteria were used to predict the yield loci, and the evolution of yield loci was predicted by the yield criterion with variable r value. In the small deformation range, Yld2000-2d yield criterion had the highest prediction accuracy for TA4 yield loci. In the plastic deformation process, the linear increasing trend of r value was directly related to the evolution of the yield loci of TA4 pure titanium. The comparison between experimental and theoretical yield loci shows that Yld2000-2d yield criterion can accurately characterize the initial yield behavior of TA4 pure titanium. The r value of TA4 pure titanium strip increases linearly with plastic deformation, and the outer convexity of TA4 yield loci predicted by Barlat89 yield criterion considering plastic evolution is more significant. In the finite element analysis,die design and process optimization of TA4 pure titanium strip stamping process, Yld2000-2d yield criterion can be used when only the initial yield loci is considered. Barlat89 yield criterion with relatively simple form can be used when anisotropic characteristics have strong plastic evolutionary correlation.