TC4钛合金超高周次轴向振动疲劳试验

应用基于压电超声疲劳试验技术开发的20kHz轴向振动疲劳试验系统,完成了室温下TC4钛合金超高周疲劳试验,获得了TC4合金在107～109周次范围内的轴向振动疲劳寿命曲线(S-N曲线);运用C.Paris推导公式预测了TC4合金材料的寿命,得到各应力水平下破坏率为50％、95％、99％的安全寿命.结果表明:在疲劳循环大于107周次时,试件仍会发生疲劳断裂,疲劳强度随循环次数的增加而下降,并不存在明显的疲劳极限.TC4合金的S-N曲线在107～109周次的范围内呈连续下降型.在轴向振动超高周疲劳试验中,试件的裂纹扩展寿命只占其在50％破坏率下疲劳安全寿命的一小部分,其疲劳寿命主要由试件的裂纹萌生寿命决定.

Ultra-high Cycle Axial Vibration Fatigue Experiment of Titanium Alloy TC4

Ultra-high cycle fatigue experiment of TC4 titanium alloy at room temperature was carried out by using 20kHz axial vibration fatigue system,which is developed based on piezoelectric ultrasonic fatigue test technology.Axial vibration fatigue life curve (S-N curve) of TC4 titanium alloy was obtained in a range of 107 to 109 cycles.The life of TC4 alloy material was predicted by using C.Paris formula,and at different stress levels,the safe life,which means survival rate is 50％,95％ and 99％ respectively,was obtained.Results indicate that when fatigue cycle is higher than 107,specimens still present fatigue fracture mode,and fatigue strength decreases with the increase of cycle times,and there is not obvious fatigue limit.S-N curve of TC4 alloy continuously declines in a range of 107 to 109 cycles.In ultra-high cycle axial vibration fatigue experiment,the crack growth life of specimen only accounts for a small part of its fatigue life under 50％ survival rate condition,the fatigue life of specimen is determined by crack initiation life of specimen.