论文部分内容阅读
针对飞机后机身框TC21损伤容限钛合金带孔零件在服役过程中易过早产生疲劳裂纹的问题,采用开缝衬套冷挤压强化工艺进行了不同挤压量下的孔强化实验,并对挤压强化后的试样进行疲劳试验研究,得到了挤压量对TC21钛合金疲劳增益的影响规律。通过有限元仿真的方法研究了挤后孔边残余应力分布规律,从宏观和微观两方面观察和分析了不同挤压量下的疲劳断口形貌,探讨了冷挤压对孔边疲劳裂纹的萌生和扩展的影响,揭示了疲劳增益机理。研究结果表明,冷挤压强化后的孔边存在明显的切向压缩残余应力,改变了孔边裂纹萌生位置,延长了交变载荷作用下的疲劳裂纹扩展寿命,疲劳寿命随着挤压量的增大而明显提高,挤后试样疲劳寿命均提高50%以上。
Aiming at the problem that the fatigue cracked titanium alloy hole parts of aircraft fuselage frame TC21 are prone to fatigue cracks prematurely during service, the hole strengthening experiments under different extrusion amount are carried out by the open extrusion billet cold extrusion strengthening process, The fatigue test of extruded and tempered samples was carried out. The influence of extrusion amount on the fatigue life of TC21 titanium alloy was obtained. Through the finite element simulation method, the distribution rule of the residual stress in the hole after squeezing is studied. The appearance of fatigue fracture under different extrusion amount is observed and analyzed from macro and micro aspects. And the impact of expansion, revealing the mechanism of fatigue gain. The results show that there is a significant tangential compressive residual stress at the hole edge after cold extrusion strengthening, which changes the initiation of crack at the edge of the hole and prolongs the fatigue crack propagation life under alternating load. The fatigue life increases with the extrusion amount Increase and significantly improve the fatigue life of the extruded samples are increased by 50% or more.