钢桥焊接细节残余应力分析及疲劳性能评估
发布时间：2018-08-04 11:25
【摘要】：伴随着我国桥梁建设的发展,钢结构桥梁的比重在不断的增大,出现了大量的焊接细节。我国焊接疲劳设计起步相对较晚,没有完善的焊接细节的疲劳设计标准。若对结构焊接细节设计不当,会出现钢桥焊接细节的疲劳裂纹,甚至造成严重的事故。 焊接是一个涉及物理、化学、力学的复杂过程,焊接加热冷却之后结构内部会存在复杂的残余应力。焊接节点传力过程中的应力集中,焊接节点焊接过程引起的初始缺陷及使结构呈现受拉状态的焊接残余应力是导致焊接节点疲劳性能显著降低的直接原因。反复荷载作用下,为准确描述焊接节点实际应力场状态,需要首先对焊接残余应力进行数值模拟,再叠加不同荷载幅引起的结构工作应力幅。焊接残余应力的准确模拟对焊接节点疲劳性能研究具有重要意义。 本文利用ANSYS程序对对接、T字形、U肋与顶板三种典型焊接细节的焊接残余应力进行了数值模拟,并对焊接接头危险点位进行了疲劳性能的分析,论文工作有以下几方面： 1根据高温条件下Q345的物理和力学参数,确定焊接热源模型、焊接过程的参数,实现了焊缝热源的移动加载,得出了三种接头准确的焊接过程温度场。编写了不同焊接接头焊接过程数值模拟的APDL命令。 2通过温度场和应力场的间接耦合调用三种接头温度场的计算结果,计算出残余应力的分布。对于U肋与顶板接头,等效残余应力随顶板厚度的增加而增加,起弧和灭弧的局部,残余应力略高于屈服强度。 3根据欧洲规范中三种接头名义应力加载计算出三种接头的实际应力,并选取应力集中较为严重的部位作为危险点。通过该点计算所得的残余应力与实际应力的叠加,采用Goodman关系结合Q345的材料S-N曲线绘制危险点的新S-N曲线。将计算结果与欧洲规范的焊接接头S-N曲线对比,分析了曲线差异的原因并提出了两个应力修正系数。
[Abstract]:With the development of bridge construction in China, the proportion of steel bridge is increasing, and a lot of welding details appear. Welding fatigue design in China started relatively late, and there is no perfect fatigue design standard for welding details. If the welding details of the structure are not properly designed, the fatigue cracks of the welding details of the steel bridge will appear, and even cause serious accidents. Welding is a complex process involving physics, chemistry and mechanics. The stress concentration in the process of welding joint transmission, the initial defects caused by welding process and the welding residual stress which make the structure appear tensile state are the direct reasons for the obvious reduction of fatigue properties of welded joints. In order to accurately describe the actual stress field of welded joints under repeated loads, it is necessary to simulate the welding residual stress first, and then to superimpose the working stress amplitude of the structure caused by different load amplitudes. The accurate simulation of welding residual stress is of great significance to the fatigue performance of welded joints. In this paper, the welding residual stress of three typical welding details of butt joint T-shaped U-rib and roof is simulated by ANSYS program, and the fatigue performance of welded joint at dangerous point is analyzed. According to the physical and mechanical parameters of Q345 at high temperature, the model of welding heat source and the parameters of welding process are determined, and the moving loading of weld heat source is realized. The accurate welding temperature field of three kinds of joints is obtained. APDL commands for numerical simulation of welding process of different welded joints are compiled. 2 the distribution of residual stress is calculated by indirect coupling of temperature field and stress field. For U-rib and roof joints, the equivalent residual stress increases with the thickness of the roof. The residual stress is slightly higher than the yield strength. 3 the actual stresses of the three joints are calculated according to the nominal stress loading of the three joints in the European Code, and the places where the stress concentration is more serious are selected as the dangerous points. Through the superposition of residual stress and actual stress calculated at this point, a new S-N curve of dangerous point is drawn by combining the Goodman relation with the material S-N curve of Q345. By comparing the calculated results with the S-N curves of welded joints in European specifications, the reasons for the difference of the curves are analyzed and two stress correction coefficients are proposed.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U441;U448.36
本文编号：2163836
[Abstract]:With the development of bridge construction in China, the proportion of steel bridge is increasing, and a lot of welding details appear. Welding fatigue design in China started relatively late, and there is no perfect fatigue design standard for welding details. If the welding details of the structure are not properly designed, the fatigue cracks of the welding details of the steel bridge will appear, and even cause serious accidents. Welding is a complex process involving physics, chemistry and mechanics. The stress concentration in the process of welding joint transmission, the initial defects caused by welding process and the welding residual stress which make the structure appear tensile state are the direct reasons for the obvious reduction of fatigue properties of welded joints. In order to accurately describe the actual stress field of welded joints under repeated loads, it is necessary to simulate the welding residual stress first, and then to superimpose the working stress amplitude of the structure caused by different load amplitudes. The accurate simulation of welding residual stress is of great significance to the fatigue performance of welded joints. In this paper, the welding residual stress of three typical welding details of butt joint T-shaped U-rib and roof is simulated by ANSYS program, and the fatigue performance of welded joint at dangerous point is analyzed. According to the physical and mechanical parameters of Q345 at high temperature, the model of welding heat source and the parameters of welding process are determined, and the moving loading of weld heat source is realized. The accurate welding temperature field of three kinds of joints is obtained. APDL commands for numerical simulation of welding process of different welded joints are compiled. 2 the distribution of residual stress is calculated by indirect coupling of temperature field and stress field. For U-rib and roof joints, the equivalent residual stress increases with the thickness of the roof. The residual stress is slightly higher than the yield strength. 3 the actual stresses of the three joints are calculated according to the nominal stress loading of the three joints in the European Code, and the places where the stress concentration is more serious are selected as the dangerous points. Through the superposition of residual stress and actual stress calculated at this point, a new S-N curve of dangerous point is drawn by combining the Goodman relation with the material S-N curve of Q345. By comparing the calculated results with the S-N curves of welded joints in European specifications, the reasons for the difference of the curves are analyzed and two stress correction coefficients are proposed.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U441;U448.36
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