基于等效临界距离法的焊接钢结构疲劳强度预测

发布时间：2018-01-09 05:13

本文关键词：基于等效临界距离法的焊接钢结构疲劳强度预测　出处：《长沙理工大学》2013年硕士论文　论文类型：学位论文

【摘要】：疲劳破坏是导致结构失效的一种主要方式,所以对结构的疲劳失效进行研究有着重要的意义。由于焊接过程中不均匀瞬态热输入，焊后不可避免的在结构内部产生残余应力，而残余应力的存在使焊接钢结构的疲劳强度降低。本文在考虑残余应力影响的基础上对焊接钢结构的疲劳性能进行了研究，运用临界距离理论探讨了焊接钢结构疲劳强度与S-N曲线的理论预测方法。本文研究的主要内容有：利用有限元分析技术，考虑材料的热物理性能和力学性能随温度的变化，使用APDL语言功能编写程序动态模拟焊接过程中金属的熔敷；针对焊接热应力场的材料非线性瞬态问题，选用弹塑性力学的增量理论进行计算，运用“生死单元技术”，动态模拟焊接过程中焊料的填入和凝固，建立了焊接温度场和残余应力场的有限元理论计算模型。分别对对接板接头、错位板接头和T型板接头的焊接温度场和残余应力场进行了数值计算分析，得到了几类典型焊接钢结构的焊接温度场和残余应力场。采用断裂力学理论，，探讨了含贯通裂纹的无限大板在均匀拉伸荷载作用下裂纹尖端附近的应力场，在研究Taylor等人提出的临界距离法（含点法、线法、面法、体积法）的基础上，建立了临界距离的圆柱法和椭圆柱法。并研究焊接残余应力对疲劳强度的影响，建立了焊接钢结构疲劳强度预测的等效临界距离理论（包括等效临界距离的点法、线法、面积法、半椭圆面积法、圆柱法和椭圆柱法）。这种理论考虑了结构几何形式、焊接接头类型、焊缝局部几何形状、应力集中、尺寸效应、残余应力等因素对结构疲劳性能的影响。利用所建立的等效临界距离方法对对接板接头、错位板接头和T型板接头的疲劳强度进行了理论预测，并与疲劳试验结果进行了比较，验证了本文所建立的理论方法的正确性。以等效临界距离理论预测的疲劳强度为基础，采用有效应力集中系数和S-N曲线理论预测模型，建立了基于等效临界距离理论的焊接钢结构有效应力集中系数和S-N曲线预测的方法。并将理论计算值与疲劳试验结果进行了比较，验证了理论方法的有效性。
[Abstract]:Fatigue failure is one of the main causes of structural failure, so it is of great significance to study the fatigue failure of structure, because of the uneven transient heat input in welding process. It is inevitable to produce residual stress inside the structure after welding. The fatigue strength of welded steel structure is reduced by the existence of residual stress. In this paper, the fatigue properties of welded steel structure are studied on the basis of considering the influence of residual stress. The theoretical prediction method of fatigue strength and S-N curve of welded steel structures is discussed by using the critical distance theory. The main contents of this paper are as follows: By using the finite element analysis technology, considering the variation of the thermal and mechanical properties of the material with temperature, the APDL language is used to compile a program to dynamically simulate the deposition of metals in the welding process. Aiming at the material nonlinear transient problem of welding thermal stress field, the incremental theory of elastic-plastic mechanics is used to calculate, and the "birth and death element technique" is used to dynamically simulate the filling and solidification of solder during welding process. The finite element theory model of welding temperature field and residual stress field is established. The welding temperature field and residual stress field of butt plate joint, staggered plate joint and T type plate joint are numerically calculated and analyzed respectively. The welding temperature field and residual stress field of several typical welded steel structures are obtained. Using the theory of fracture mechanics, the stress field near the crack tip of an infinite plate with a through-through crack under uniform tensile load is discussed. The critical distance method (including point method) proposed by Taylor et al. On the basis of linear method, surface method and volume method, the critical distance cylindrical method and elliptical column method are established, and the effect of welding residual stress on fatigue strength is studied. The equivalent critical distance theory for fatigue strength prediction of welded steel structures is established, including point method, line method, area method and semi-elliptical area method. This theory takes into account the geometry of the structure, the type of welded joint, the local geometric shape of the weld, the stress concentration and the size effect. Using the method of equivalent critical distance, the fatigue strength of butt plate joint, staggered plate joint and T-type plate joint is predicted theoretically. Compared with the fatigue test results, the correctness of the theoretical method established in this paper is verified. Based on the fatigue strength predicted by the equivalent critical distance theory, the effective stress concentration factor and the S-N curve theory are used to predict the fatigue strength. An effective stress concentration factor and S-N curve prediction method for welded steel structures based on the equivalent critical distance theory is established, and the calculated values are compared with the fatigue test results. The validity of the theoretical method is verified.
【学位授予单位】：长沙理工大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU391

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