【作者】 白庆华；

【导师】 马越进；

【作者基本信息】 河北农业大学 ， 农业机械化工程， 2012， 博士

【摘要】 焊接过程是一个快速、不均匀的热循环过程，焊缝附近的温度梯皮很大。焊接过程温度分布不平衡，接近焊接区域的材料膨胀率和收缩率不同，导致了复杂的三维残余应力状态，伴随产生暂时的或永久的焊接变形，并且不可避免地会在工件内产生复杂的焊接残余应力、裂纹、气孔等缺陷，影响焊接结构的质量和使用性能。随焊锤击是近些年发展起来的焊接新技术，具有设备简单、操作灵活、工作效率高的优点。焊件通过锤击处理可以有效降低和消除焊接残余应力，避免焊接裂纹的产生，提高焊缝的疲劳强度，调整焊接残余应力分布状态。在锤击系统中，振动锤的参数选择对焊接残余应力的消除也有很大的影响，必须要根据焊接过程中温度场的变化来确定振动锤形状、锤击的丌始时间、以及锤击力的强度、锤击频率等参数。这样就可以更好地控制锤击的效果，消除焊接应力。通过对各种焊接现象的计算机模拟，可以得到不同时刻焊接温度场和应力场的分布情况，就可以为随焊锤击工艺提供锤击位置、锤击时机等参考依掘。通过系统讨论焊接过程的有限元分析方法和理论，对焊接过程中的温度场和应力场的基本理论和数值模拟分析方法进行了研究，利用问接藕合法，首先模拟焊接过程中的温度场分布，然后将温度场模拟结果以载荷的形式添加到应力场的分析过程，即可以得到应力场的分布；然后将模拟温度场和应力场分布规律与传统结果进行比较，并通过实验进行验证。本文研究的主要内容有：首先对焊接过程进行合理的假设，建立了焊件的三维模型，适当的简化边界条件，合理的划分网格结构，确定了单元类型；建立了高斯函数分布的面热源模型，利用ANSYS软件的APDL语言编写程序，实现焊接热源的移动，采用生死单元方法，解决了焊接热源在平板多道焊缝焊接过程中的数学模拟问题；通过改变单元属性的方法，解决材料的熔化、凝固等相变问题；采用牛顿一拉普森迭代方法，解决了模拟过程中的不收敛问题；对焊接过程进行了实时动态模拟，得到了焊接温度场的温度分向图和应力场的残余应力分布图和相应的分布规律，与传统焊接理论相比较，为锤击时机的选择提供理论依据：最后采用小孔法对焊件的残余应力进行测量，通过实验对数值模拟过程进行验证，为锤击法消除焊接应力提供理论依据，以便确定最佳锤击参数。本文对平板多道焊缝的模拟为复杂焊接结构进行三维焊接温度场、应力场和随焊锤击过程的分析提供了理论依据和指导，促进了有限元分析方法在焊接分析以及工程中的应用。更多还原

【Abstract】 Welding is a rapid，non-uniformed heat process．there is the great temperature gradient near welding seams．With the different of temperature distribution．inflation and shrinkage in different materials．weding seams have a complex three—dimensional residual stress state，along with produce temporary or permanent welding deformation．and would inevitably produce complex in the welding residual stress．cracks．porosity,defects，influence the quality of welding structure and performanceWelding with trailing peening is the welding new technology,which developed inrecent years，have some advantages snch as equipment simple．flexible opel‘ation．high working efficiency and so on．Through trailing peening on the workpiece．it canefl?ctively reduce and elimate welding residual stress，avoid welding crack，improvefatigue strength of the welding seams．adjust welding residual stl_eSS distribntion Inthe s)，stem ot’welding with trailing peening．it is a significant inflence on l-elif ol’welding residual stress to choice parameters of vibratory hammer．According tovariation of temperature field during welding process．it can@tel mine someparameters such as the shape of vibratory hammer，the time of beginning to peening．the force and frequency of peening．So it call control effect of trailing peening andelimate welding stress．Through simulated welding process with computer．we canknow the distribution of welding temperature field and stress field at difercntial time．and offer reference for the position and beginning time during welding,aith trailingpeeningThrough the discussion of the welding process system finite element analysismethod and theory．the welding process the temperature field and stress field or thebasic theory and numerical simulation analysis method was studied．and use themethod ol、thcrmal—structure couple．first simulation in the process of weldingtemperature distribution，and then put temperature field simulation results to loadform tile analysis of the stress field added to the process that call get tile distributionof stress field：Then the simulation of tile temperature field and stress field distribution rule and compared to the traditional．and througll experiment verifiedThe research works of the paper are as following：fil‘stly，through reasonable assumpting of welding process．using the finitc element method and theory．it make a 3-D models of workpiece which wled multi—seams in fiat．simplify boundary,’conditions and loads．divide grid structure and confirm node and element type；fhe second，establish the gaussian flmction of the distribution of the surface heat source nlodel．make program with APDI．of ANSYS software，rcalize the nlove of heat source．use the dead—live method，slove the simulation problem of heat source inmulti—seams flat during the welding process．Thirdly，it can slove the phase transitionproblem of melting and solidification and slove the problem of the convergencedifficulty or the un—convergence with Newton—Raphson method，and then have areal-time dynatic simulation tO welding process，get the distribution graph and law oftemperature field in welding workpiece；then using the temperature result as load withcOuDle method，it can receive the distribution graph and law of stress field，comparewith the traditional theory of welding，provide the theory basis for the opportunity tobegin tO peen，and SO confirm the parameters about welding trailing peening；Lastly．itcan dO some experiments to measure the temperature field and stress field in theworkpiece during welding process，compare the measure result with simulated resultwhich received on the computer,then verify simulated result and offer more be~erparameters to peen the workpiece during welding process．It Drovides theoretical basis and guidance tO have a ansyis for 3-D temperature field and stress field in the simulation process of multi—seams welding flat，and Dromote the finite element analysis method in welding analysis and application in engineering更多还原