工业纯钛中低温蠕变的等时应力应变曲线

Isochronous Stress-strain Curves of CP-Ti at Low and Intermediate Temperatures

根据工业纯钛TA2在服役温度范围内(室温、353 K、423 K)的拉伸实验和蠕变实验获得了工业纯钛的拉伸应力应变曲线和蠕变曲线。由中低温蠕变实验数据发现工业纯钛在服役温度范围内会产生显著的蠕变现象,蠕变特征会随温度发生变化。随后,分别建立了工业纯钛在各温度下的弹塑性拉伸本构方程和蠕变本构方程。综合拉伸和蠕变本构方程建立了工业纯钛在服役温度范围内的等时应力应变曲线。等时应力应变曲线显著低于拉伸曲线,并且存在寿命相关性,随着寿命要求的提高等时应力应变曲线不断下降。值得注意的是在不同的温度下等时应力应变曲线随寿命要求的变化规律存在显著差别。根据等时应力应变曲线、结构允许的极限应变和结构设计寿命,本研究提出了工业纯钛与时间相关的许用应力曲线。

The tensile stress-strain curves and creep curves of commercially pure titanium TA2 in the service temperature range（room temperature, 353 K, 423 K） were obtained by tensile testing and creep testing. Based on the creep testing results, a significant creep phenomenon was observed in the service temperature range, and the creep feature was changed with temperature. Then, the tensile constitutive equation and the creep constitutive equation were constructed for TA2. Combining the tensile and the creep constitutive equations, the isochronous stress-strain curves were generated. Results show that the isochronous stress-strain curves of TA2 are much lower than the tensile stress-strain curves, and the isochronous stress-strain curves are decreased with longer design life. Moreover, the variation feature of isochronous stress-strain curves with design life is changed with temperature. Based on the isochronous stress-strain curves, allowable limit strain and design life, the time dependent allowable stress of CP-Ti was proposed.