基于铁基形状记忆合金的钢桥U肋对接焊缝疲劳裂纹加固数值分析

Numerical Analysis of Fatigue Crack for Strengthening of Weld Joints of U-Rib of Steel Bridge Based on Fe-SMA

摘要: 为研究铁基形状记忆合金(Fe-SMA)贴片加固对含气孔缺陷钢桥U肋对接焊缝疲劳裂纹的抑制效果，本文采用ABAQUS有限元软件建立了考虑粘结层损伤的三维数值分析模型。基于内聚力理论模拟粘结界面力学行为，采用扩展有限元法(XFEM)模拟裂纹扩展过程，通过等效温度载荷法施加Fe-SMA激活预应力。系统分析了气孔缺陷对应力分布及裂纹前缘应力强度因子幅值的影响规律，验证了Fe-SMA加固的有效性。结果表明：气孔缺陷处产生显著应力集中，裂纹周边应力较无缺陷试件增大33.64%，裂纹前缘应力强度因子升高56.89%；粘贴Fe-SMA加固后，裂缝尖端应力降低53.55%，I型应力强度因子幅值降幅达81.77%，有效抑制了疲劳裂纹扩展；U肋对接焊缝疲劳裂纹扩展主要由I型开裂主导，Fe-SMA加固显著改善了I型开裂模式且未引入新的疲劳损伤模式；粘结层厚度的不均匀性不改变应力传递方向，但会导致应力分布的不对称性。本研究为Fe-SMA加固技术在钢桥疲劳裂纹修复中的工程应用提供了数值分析依据。

Abstract: To investigate the effectiveness of iron-based shape memory alloy (Fe-SMA) patch reinforcement in suppressing fatigue cracks in butt welds of U-ribs on steel bridges with porosity defects, a three-dimensional numerical analysis model that accounts for damage in the bond layer was established using ABAQUS finite element software. The mechanical behavior at the bonded interface was simulated based on cohesive force theory, the crack propagation process was modeled using the Extended Finite Element Method (XFEM), and Fe-SMA activation prestress was applied via the equivalent temperature load method. The influence of porosity defects on stress distribution and the amplitude of the stress intensity factor at the crack tip was systematically analyzed, verifying the effectiveness of Fe-SMA reinforcement. The results indicate that significant stress concentration occurs at the porosity defects, with the stress around the crack increasing by 33.64% compared to defect-free specimens, and the stress intensity factor at the crack tip rising by 56.89%. After reinforcement with Fe-SMA, the stress at the crack tip decreased by 53.55%, and the amplitude of the Type I stress intensity factor decreased by 81.77%, effectively suppressing fatigue crack propagation; fatigue crack propagation in U-rib butt welds is primarily dominated by Type I cracking. Fe-SMA reinforcement significantly improved the Type I cracking mode without introducing new fatigue damage modes; unevenness in the adhesive layer thickness does not alter the direction of stress transfer but leads to asymmetry in stress distribution. This study provides a numerical analysis basis for the engineering application of Fe-SMA reinforcement technology in the repair of fatigue cracks in steel bridges.