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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R 3种处理工艺后主动连杆振动疲劳对比试验.结果表明,在317 MPa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1.4 mm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.
Aiming at the problem of fatigue fracture of the active connecting rod R of deflated valve of a certain type of engine, the research on laser shock strengthening technology of active connecting rod was carried out. After prototype and laser shock strengthening, shot peening and R 3 treatment The results show that under the stress level of 317 MPa, the fatigue life of laser shock-strengthening, shot peening and active connecting rod after R increase are 5.24 times, 3.89 times and 1.36 times that of prototype respectively, Compared with the two kinds of processes, the laser shock strengthening has the advantages of good strengthening effect, high process stability and easy realization, and is the best treatment process to reduce the fatigue fracture fault of the active connecting rod so far. The surface roughness Is smaller, resulting in a high numerical residual compressive stress layer with a depth of about 1.4 mm, the surface grain refinement to nanocrystals with high density dislocation.The three together can effectively reduce the stress concentration at the transfer R, and the fatigue crack inhibition Transfer R at the initiation and expansion of active connecting rod vibration fatigue life is the main reason.