钛合金超声滚压表面完整性分析及微动疲劳预测

Surface integrity analysis and fretting fatigue prediction on titanium alloy by ultrasonic rolling

为改善Ti6Al4V钛合金加工表面形性和抗微动疲劳性能,采用超声滚压技术对其表面进行强化处理,并结合试验与数值分析研究了超声表面滚压强化后的表面完整性及其微动疲劳裂纹的萌生与扩展。试验研究表明:超声表面滚压处理使Ti6Al4V钛合金表面粗糙度明显降低、组织细化且沿深度方向呈梯度分布,并在钛合金表层引入了-573 MPa的残余压应力和表层硬度为447 HK、深度为120μm的加工硬化层。根据超声表面滚压的加工表面形性,建立了Ti6Al4V钛合金微动疲劳有限元模型,结合最大相对滑动幅度、耗散能和等效损伤应力模型预测裂纹萌生位置,采用最大能量释放率准则预测裂纹萌生方向,最后基于ABAQUS和FRANC3D联合仿真实现了微动疲劳裂纹扩展预测。

In order to improve the surface performance and fretting fatigue resistance of Ti6Al4V titanium alloy,the ultrasonic rolling technology was used for its surface strengthening treatment,and the surface integrity and fretting fatigue crack initiation and propagation after ultrasonic surface rolling strengthening were studied by combining experiments and numerbycal analysis.Experimental research shows that ultrasonic surface rolling process can significantly reduce the surface roughness of Ti6Al4V titanium alloy,refine the microstructure with a gradient distribution along the depth direction,and introduce the compressive residual stress of-573 MPa and the work hardened layer with surface hardness of 447 HK and depth of 120μm in the surface layer of the titanium alloy.Based on the surface integrity induced by ultrasonic surface rolling process,a finite element model of fretting fatigue for Ti6Al4V titanium alloy was established,and the crack initiation position is predicted by combining the maximum relative sliding amplitude,dissipated energy and equivalent damage stress model.The crack initiation direction is predicted by the maximum energy release rate criterion.Finally,based on joint simulation of ABAQUS and FRANC3D,the prediction on the fretting fatigue crack propagation is realized.