电弧增材制造钛合金界面处残余应力及其影响研究

采用电弧增材制造方法制备了含增材/基材界面钛合金板,采用轮廓法测量了其残余应力分布。建立了模拟紧凑拉伸(C(T))试样加工和裂纹扩展过程中残余应力发展的有限元模型,缺口状态C(T)试样内残余应力分布与轮廓法测试结果吻合良好。采用该模型讨论了试样内残余应力随裂纹扩展的变化规律及对裂纹扩展的影响。试验和数值分析结果表明:2种类型试样缺口状态的残余应力分布有很大差别,A类试样(缺口位于基材)残余压应力区域靠近缺口根部,C类试样(缺口位于增材)残余压应力区域远离缺口根部;A类试样内残余应力随裂纹扩展迅速释放,残余应力引起的应力强度因子较小;C类试样内残余应力随裂纹扩展变化较小,残余应力引起的应力强度因子较高,降低了疲劳裂纹扩展寿命。

Residual Stress and its Influence at the Interface of Wire + Arc Additive Manufactured Titanium Alloy

A Ti-6Al-4V wall was fabricated by WAAM on the basis of substrate alloy. Residual stress in the WAAM-substrate wall was measured by using contour method. There were considerable residual stresses in the WAAM-substrate wall. A finite element model was developed to simulate stress release in the cutting processing of the compact tension (C(T)) specimen from the wall. The calculated residual stress retained in the C(T) specimen was in good agreement with the measurement result obtained by contour method. Residual stress evolution and its effects on the crack propagation behavior at the WAAM/substrate interface were estimated by the developed finite element model. Following observations are revealed by experimental and numerical analysis. Residual stress distributions are quite different in the Type A and C specimen. For Type A specimen (notch located in the substrate), the compression residual stress area is closed to the notch, whereas for the Type C specimen (notch located in the WAAM alloy), the compression residual stress area is far away from the notch. Residual stresses has a little effect on the fatigue crack growth life of Type A specimen since most of them are released after the crack quickly entered and went through the compression area. However, residual stresses decrease a little with the crack growth at a long period for Type C specimen, which results a considerable stress intensity factor and shortens the fatigue crack growth life.