TC-11钛合金高低周复合疲劳及损伤累积研究

RESEARCH ON HIGH-LOW CYCLE COMPLEX FATIGUE AND ACCUMULATIVE DAMAGE FOR Ti-ALLOY TC11

本文系统地研究了 TC- 11钛合金在室温和高温下高、低周复合疲劳行为 ,其中包括高低周循环应力比 m、试验温度、缺口试样的预应力超载对复合疲劳寿命 Nf L的影响。结果表明 :复合疲劳寿命随 m值的增加而明显降低 ,尤其是 m=35时 ,其 Nf L降低十多倍 ,并在 m- lg Nf L曲线上 ,当 m=10时出现一个拐点。在相同的 m值和低周应力为 90 0 MPa时 ,当温度从室温升高到 150℃时 ,其 Nf L 下降约 1/ 3,当温度继续升高到 30 0℃时 ,其 Nf L 接近零。此外 ,还提出了复合疲劳的损伤累积模型 ,1/ Nf L =1/ N L +n/ Nh。

The high low cycle complex fatigue behaviours of Ti alloy TC11 were researched systematically at room and elevated temperatures.At the same time,the effects of complex stress ratio m ,test temperature and prestress overload for SEN specimen on complex fatigue life N fL were taken into consideration.The work comes to the conclusion that:The complex fatigue life decreases obviously with m increased,especially when m =35%,the N fl decreases more than 10 times,and there occurs a knee on the m —log N fL curve near m =10%.The complex fatigue of the alloy TC11 is very sensitive to test temperature under the same m ratio and LCF stress,as test temperature rises from room temperature to 150℃,the complex fatigue life N fL drops by 66% under m =10% and σ max =945MPa.If the temperature comes up continuously to 300℃,its fatigue life approaches to zero.In addition,a model of the accumulative damage for complex cyclic fatigue is formulated as follows: 1/N fL =1/N L+n/N h .