TC-11钛合金高低周复合疲劳及损伤累积研究

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N_fL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N_fL降低十多倍,并在m-lgN_fL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900MPa时,当温度从室温升高到150℃时,其N_fL下降约1/3,当温度继续升高到300℃时,其N_fL接近零。此外,还提出了复合疲劳的损伤累积模型,1/N_fL=1/NL+n/N_h。 

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

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_f .