TC25钛合金室温高周疲劳累积损伤与疲劳寿命分析

Analysis on High Cycle Fatigue Accumulation Damage and Fatigue Life of TC25 Titanium Alloy at Room Temperature

在恒定最大应力700 MPa条件下,对TC25钛合金进行不同应力比下的室温高周疲劳实验,测试TC25钛合金的高周疲劳寿命,考察疲劳寿命与应力比之间的关系.每间隔一定疲劳周次测试试样的电阻,采用电阻变化率表征疲劳损伤,并应用Chaboche损伤模型来推导疲劳损伤演化方程,结果显示理论计算结果与实验数据吻合,表明Chaboche损伤模型能够精确预测轴向循环加载条件下TC25钛合金的高周疲劳累积损伤,且在恒定最大应力条件下,TC25钛合金的疲劳寿命随应力比的增大而增大.测试应力比r为0.1时不同应变强化量下TC25钛合金的疲劳寿命,基于微观结构分析,考察应变强化对疲劳寿命的影响,结果表明增大应变强化量能有效提高疲劳寿命.

The high cycle fatigue tests for TC25titanium alloy specimens under different stress ratios are carried out at a given maximum stress level of700MPa at room temperature.The high cycle fatigue life of TC25titanium alloy is measured,and the relation between fatigue life and stress ratio is investigated.Every certain cycles,the fatigue test is reterrupted,and the current resistance values at various fatigue cycles are measured.The ratio of resistance change is selected to characterize the fatigue damage,and the Chaboche damage model is adopted to derive the fatigue damage evolution equation.The results indicate that the theoretical calculated values agree well with the test data,which suggests that the Chaboche damage model can precisely predict the accumulated damage in TC25titanium alloy during the high cycle fatigue at uniaxial cycle loading.Under the fixed maximum stress level,the high cycle fatigue life of TC25titanium alloy increases with increasing stress ratio.Finally,the high cycle fatigue lifetimes for TC25titanium alloy specimens at various strain hardening rates are measured at a given stress ratio of0.1,the effect of strain hardening on fatigue life is investigated based on a microstructure analysis.The result shows that increasing the strain hardening rate can effectively improve the high cycle fatigue life of TC25titanium alloy.