激光冲击强化提高主动连杆振动疲劳性能

针对某型发动机放气活门主动连杆转接R处的疲劳断裂问题,进行了主动连杆激光冲击强化工艺研究;完成了原型件和激光冲击强化、喷丸及加大R3种处理工艺后主动连杆振动疲劳对比试验.结果表明,在317MPa的应力水平下,激光冲击强化、喷丸和加大R后主动连杆疲劳寿命分别为原型件的5.24倍、3.89倍及1.36倍;与其它2种工艺相比,激光冲击强化具有强化效果好、工艺稳定性高、易于实现等优点,是截至目前减少主动连杆疲劳断裂故障的最佳处理工艺.主动连杆激光冲击强化后表面粗糙度较小,产生深度约1.4mm的高数值残余压应力层,表层晶粒细化至纳米晶并伴随高密度位错.三者共同作用可以有效缓解转接R处的应力集中,抑制疲劳裂纹在转接R处的萌生和扩展,是主动连杆振动疲劳寿命提高的主要原因.

LSP to improve vibration fatigue performance of deflation valve lever

In order to solve the fatigue failure of the valve lever fixed in certain aeroengine,the technology of laser shock processing(LSP) on the valve lever was studied.Then,the valve levers of prototype and valve levers processed by LSP,shot peening(SP) and enlarge R were applied to vibration fatigue test.The results show that at the vibrating stress level of 317MPa,compared with the prototype,LSP,SP and enlarge R could increase the fatigue life by 424%,289% and 36% distinguishably.The effectivity,stability and operability of LSP make it the best way to decrease fatigue failure of the valve lever at the present time.The LSP strengthening effect on valve lever is attributed to the low roughness,the high numerical compressive residual stress field about 1.4mm in depth and the grain refinement to nanocrystal accompanied with high density dislocation.The three factors above are the main reasons what LSP could prolong the fatigue life of valve lever,because that they work together could efficiently release the stress concentration at R area as well as restrain the initiation and propagation of fatigue crack.