基于FAD的铝合金车体焊接缺陷安全性评价方法研究

目的确保高速列车运行安全,采用先进的方法和理论对焊接缺陷进行评定显得非常重要。方法采用断裂力学和有限元相结合的方法,建立车体全比例有限元模型。采用热弹塑性法对焊接残余应力进行有限元数值仿真。基于标准BS 7910提供的焊接缺陷评价方法,对焊接缺陷进行安全性评定。结果对车体带焊缝的有限元模型,依据BS EN12663标准施加车体所承受的载荷,获取焊缝关注点的应力转化所得到一次应力。根据关注点信息建立所在焊缝处的接头模型进行热弹塑性仿真模拟,从而获取该关注点残余应力数值及分布转化所得到二次应力。将焊接缺陷进行裂纹当量化,从而计算得到载荷比与应力强度因子比值,结合许用FAD曲线,对高速列车铝合金车体上焊缝关注点进行安全性评价。结论该方法对车体这种大型复杂焊接结构的安全性进行评价是可行的,并对焊接缺陷是否合于使用提出质量控制的建议。

Methods for Safety Assessment of Welding Defects for Aluminum Alloy Body Based on FAD

Objective To ensure safety of high-speed trains, it is very important to evaluate welding defects with advanced method and theory. Methods Based on combination of fracture mechanics and finite element method, a full scale finite element model of body was established. Finite element numerical simulation of welding residual stress was carried out with the therm-elastic method. The safety of welding defects was evaluated based on the assessment of welding defects provided by standard BS7910. Result For the finite element model of the body including the weld seam, the load was applied to the body according to standard BS EN12663. The primary stress was obtained by transforming stress of the weld points of interest. Ac-cording to the information of the point of interest, the finite element model of the welded joint was established. And the simulation was carried out based on the therm-elastic method to obtain the residual stress of the point of interest which is further transformed into the secondary stress. Finally, the welding defects were quantitatively in combination with the above-mentioned primary stress and secondary stress, the ratio of the load ratio to the stress intensity factor was further calculated. Combined with the FAD curve, safety of the focus points on the aluminum alloy body of the high-speed train was evaluated. Conclusion This method is feasible for evaluating the safety of a large and complex welded structure like the train body. Suggestions on quality control for the use of welding defects are proposed.