拉-拉疲劳载荷下钛合金湿喷丸的残余应力松弛及再次喷丸工艺EI北大核心CSCD

采用湿法喷丸强化工艺(wet shot-peening)对TC4钛合金表面进行处理,研究高、低周的拉-拉疲劳过程中合金残余应力松弛规律,探讨再次喷丸工艺(re-shot-peening,RSP)对疲劳寿命的影响。结果表明:在拉应力载荷状态下,残余压应力依然发生松弛现象。疲劳载荷水平对喷丸TC4钛合金残余压应力场(CRSF)的松弛速率、松弛程度和松弛范围具有重要影响。高周疲劳(HCF)过程中残余应力松弛主要发生在近表层0~30μm,松弛速率较慢。低周疲劳(LCF)过程中残余应力松弛发生在0~80μm,范围更大,速率更快。RSP周期对于TC4钛合金的疲劳寿命也具有较大影响。在25%和50%初始喷丸疲劳寿命进行RSP处理会显著提高疲劳寿命,而在75%初始喷丸疲劳寿命处进行RSP处理对于疲劳寿命基本没有影响。此外,RSP的强化效果与疲劳载荷水平相关,对于高周疲劳寿命提高明显。

Residual stress relaxation and re-shot-peening process of wet shot-peened titanium alloy during tensile fatigue load

The surface of TC4 titanium alloy was treated by wet shot-peening(SP).The residual stress relaxation during high and low cycle tensile fatigue was studied,and the effect of re-shot-peening(RSP)on fatigue life was discussed.The results show that relaxation of compressive residual stress still occurs under tensile stress.The fatigue load level has an important influence on the relaxation rate,degree and range of compressive residual stress field(CRSF)of shot peened TC4 titanium alloy.Residual stress relaxation during high cycle fatigue(HCF)mainly occurs in the near surface layer of 0-30μm,and the relaxation rate is slow,while residual stress relaxation in low cycle fatigue(LCF)mainly occurs in the range of 0-80μm,which is deeper and faster.RSP also has a great influence on the fatigue life of TC4 titanium alloy.It can significantly improve fatigue life at 25%and 50%of initial SP fatigue life,but has little effect on fatigue life at 75%of initial SP fatigue life.In addition,the strengthening effect of RSP is related to the level of fatigue load,which improves the HCF life obviously.