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提出一种微观尺度的有限元模型,模拟了焊接接头的变形和短裂纹的萌生寿命。该模型考虑了焊接接头晶粒取向的不同和焊缝不同区域力学性能的差异。塑性应变能被作为疲劳损伤参量,结合疲劳寿命的能量准则来预测疲劳裂纹的萌生寿命。通过分析钛合金电子束焊的实验数据对该模型进行了验证。结果表明,在恒幅载荷作用下,焊接接头裂纹萌生于焊缝区多个晶界交汇或者较大且轮廓有畸变的晶粒内;微裂纹主要以Ⅰ型裂纹扩展;该微观有限元模型结合疲劳寿命预测的能量法在微观尺度上能够较好地完成焊缝疲劳性能的表征和疲劳寿命的估算。
A micro-scale finite element model is proposed to simulate the deformation of welded joints and the initiation life of short cracks. The model considers the difference in grain orientation of the welded joint and the mechanical properties in different regions of the weld. The plastic strain energy can be used as fatigue damage parameter to predict the fatigue life of fatigue crack by combining the energy criterion of fatigue life. The model was verified by analyzing the experimental data of titanium alloy electron beam welding. The results show that under the action of constant amplitude load, the crack initiation in the welded joint occurs in the grain boundaries where many grain boundaries intersect with each other or have large and distorted contours in the weld zone. The microcracks mainly expand with type Ⅰ crack. The microscopic finite element model The fatigue life prediction energy method can well characterize the fatigue performance of the weld and estimate the fatigue life at the microscopic scale.