焊接顺序对中厚板对接焊残余应力的影响

针对同种材料,但几何结构不同的中厚板结构件之间的对接焊,运用有限元软件进行模拟,分析多层多道焊各层焊缝的焊接顺序对焊缝区域横、纵向残余应力的影响。采用内生热的加载方式模拟热源,采用生死单元法模拟多层多道焊缝的焊接过程。模拟结果表明,从几何尺寸小的一边向几何尺寸大的一边焊,沿焊缝底部和顶部中心线方向产生的横纵向残余应力峰值最小;底层的几道焊缝的焊接顺序对焊缝底部和顶部中心线方向所产生的横纵向残余应力的影响不大。     

SJ200型双湿式搅拌机底部框架结构件变形技术研究

为避免SJ200型双湿式搅拌机设计时底部框架采用框形结构可能出现的弱刚度问题,对底部框架进行了动静态性能分析.首先选用Pro/E三维软件对该结构进行了三维建模,然后将所建三维实体模型导入ALGOR有限元分析软件,利用ALGOR有限元分析软件对底部框架进行静态和模态分析,得到了该底部框架的应力分布、应变分布和固有频率等动静态性能参数,其最大应力值未超过材料的许用应力,最大应变也满足设计要求,固有频率偏离该搅拌机的工作频率.从整个设计结果来看该底部框架的设计较为合理,可应用于实际生产.     

SJ200型双湿式搅拌机底部框架结构件变形技术研究

为避免SJ200型双湿式搅拌机设计时底部框架采用框形结构可能出现的弱刚度问题,对底部框架进行了动静态性能分析。首先选用PrO／E三维软件对该结构进行了三维建模,然后将所建三维实体模型导入ALGOR有限元分析软件,利用ALGOR有限元分析软件对底部框架进行静态和模态分析,得到了该底部框架的应力分布、应变分布和固有频率等动静态性能参数,其最大应力值未超过材料的许用应力,最大应变也满足设计要求,固有频率偏离该搅拌机的工作频率。从整个设计结果来看该底部框架的设计较为合理,可应用于实际生产。     

焊接顺序对T形接头焊接残余应力场的影响

为了得到T形接头焊接顺序的优化方案,在确定合理的焊接热源形式以及建立有限元模型的基础上,利用单元死活技术从多道焊、分段焊与多层焊的角度对焊接顺序对T形接头焊接残余应力场的影响进行数值分析.对于多道焊来说,焊接残余拉应力出现在焊缝及其附近区域,且峰值出现在焊缝区域;相邻焊道之间采用首尾相接的方法得到的焊接残余拉应力峰值是最小的.对于分段焊来说,采用先焊两端后焊中间的方法不仅可以增加整个焊缝的焊接残余低应力区域;而且可以有效地降低先焊区域的焊接残余应力,降低效果与后焊焊段的焊接方向以及先焊焊段上的点到后焊焊段端部的距离有关.在多层焊的过程中,采用对称施焊的方法得到的焊接残余拉应力峰值是最小的.     

高压水射流喷丸降低焊接残余应力有限元分析

焊接不可避免产生残余应力,对结构完整性造成很大影响。提出利用高压水射流喷丸技术降低焊接残余应力,并利用有限元法进行计算模拟。分别开发了模拟焊接的移动双椭球热源子程序及模拟高压水射流喷丸的移动压力载荷子程序,得到了经高压水射流喷丸处理前后焊接残余应力分布的变化规律。计算结果表明,经高压水射流喷丸处理后,焊缝和热影响区存在的焊态残余应力得到降低,在焊缝区已经产生压缩应力。证明高压水射流喷丸具有降低焊接残余应力的效果。     

基于数值计算的切割焊接连续加工残余应力演变过程

热切割与焊接在船舶制造中以先后顺序连续作用于构件,形成复杂的工艺耦合残余应力场,给掌握船体结构残余应力分布带来困难.为此,以典型的平板结构切割成形后对接焊工艺过程为对象,基于热弹塑性有限元法,建立该过程的数值计算模型,分析切、焊耦合残余应力的分布规律与演变过程.结果表明,在切焊连续加工中,沿焊缝边缘存在超过材料屈服点的拉应力区,其宽度大于单独进行切割或焊接工艺时的情况;距焊缝较远位置的应力不仅受其温度升降影响,还要平衡热源周围的压应力,因此率先呈现出渐增的拉应力;初始切割残余应力对最终耦合残余应力的影响取决于温度变化梯度的大小.     

低成本钛合金激光-电弧复合焊接仿真分析

以10 mm的TC4LCA钛合金板为母材,建立TC4LCA板材有限元焊接接头模型,应用Marc软件对热源进行校核,校核结果吻合度较好,并对温度场和应力场进行模拟计算,结果表明焊缝底部位置存在较大残余应力,是焊接缺陷敏感区域;焊后试件中间位置横截面横向残余应力呈现上表面与下表面两端受压、中间受拉的状态,板厚方向残余应力数值较小。     

基于热循环曲线法的低合金高强钢对接接头焊接残余应力数值模拟

以Q345低合金高强钢对接接头为研究对象,建立热-冶金-力学耦合的三维有限元模型,在考虑相变情况下采用三维双椭球体热源模型对单道焊的焊接温度场进行数值模拟,再基于提取的热循环曲线(TCC)对该热源模型进行简化。分别采用三维双椭球体热源模型和基于TCC简化的热源模型对单道焊和多道焊对接接头的残余应力进行计算,并进行了试验验证。结果表明：根据温度场模拟得到的单焊道焊缝TCC与试验结果吻合良好,相对误差小于2.34%,验证了提取的TCC的准确性;采用三维双椭球体热源模型和基于TCC简化热源模型模拟得到的接头残余应力与试验结果吻合良好,其中单焊道接头纵向残余应力相对误差分别小于11.38%,4.34%,验证了2种模拟方法的准确性;与三维双椭球体热源模型相比,基于TCC简化热源模型的计算效率提高32%以上。     

不锈钢薄板对接焊仿真分析

在薄板焊接中,高温热源加载和移动后快速冷却,使得焊缝处存在焊接残余应力。为了预测焊接残余应力集中地方和大小,方便进行工艺设计,采用ANSYS WORKBENCH对不锈钢薄板对接焊焊缝进行数值分析,得出温度场和应力场分布。     

中厚板铝合金光纤激光+MIG复合热源焊残余应力的数值分析

基于热弹塑性理论性,建立铝合金激光+熔化极惰性气体保护焊(Metal inert gas,MIG)复合热源焊残余应力的三维数值分析模型。激光和电弧热输入分别采用双椭球体热源模型和热流密度峰值指数递增的锥体热源模型描述。利用所建模型,通过ANSYS有限元软件对12 mm厚铝合金复合焊对接接头残余应力进行模拟计算,研究其分布特征,并与MIG焊的计算结果进行比较。同时,将温度场与残余应力的计算结果与试验结果进行对比,验证模型的准确性。研究结果表明,在焊缝及近缝区,纵向拉应力及等效残余应力较大,两者应力峰值均低于材料的屈服强度。而相较于电弧作用区域,激光作用区域残余应力相对较高。焊趾处横向残余表现为拉应力,但应力峰值相对较低。与MIG多层多道焊相比,复合焊纵向应力和等效应力高应力区域明显较窄;焊件上表面复合焊应力峰值小于MIG焊,但下表面应力峰值则较MIG焊大。     

SUS310S不锈钢局部真空电子束焊接接头残余应力及变形研究

作为一种新型焊接方法,局部真空电子束焊接常被用于制造厚大的奥氏体不锈钢焊接接头,而该类接头的焊接残余应力和变形问题受到广泛关注。对板厚40 mm的SUS310S不锈钢局部真空电子束焊接的对接接头进行了研究,并利用光学显微镜表征接头的组织形貌,利用显微硬度计测量接头的硬度分布,采用盲孔法装置和三坐标测量仪测量了接头的残余应力与面外变形。同时,基于ABAQUS有限元软件平台,通过编写用户子程序开发了一种复合热源模型来模拟局部真空电子束焊接过程中的热输入。采用所开发的“热-弹-塑性有限元”计算方法,模拟了接头在局部真空电子束焊条件下的残余应力与变形,模拟结果与试验结果吻合良好,验证了所开发的“热-弹-塑性有限元方法”的有效性。同时基于数值模拟结果,还详细讨论了局部真空电子束焊厚板对接接头的残余应力分布与焊接变形特征。     

Investigations on welding residual stress and distortion in a cylinder assembly by means of a 3D finite element method and experiments

In the present work, both experimental and numerical simulation methods are used to investigate the characteristics of welding distortion and residual stress distribution. A 3D thermo-mechanical Finite Element Analysis (FEA) method is used to predict the welding distortion and residual stress of cylinder-shaped multi-pass layer weldments. Each weld pass is performed using a quarter-circle balanced welding procedure. To investigate the influence of deposition sequence and welding heat input on the welding distortion and residual stress, a continuous welding procedure is also calculated. The corresponding FEA models considered a moving heat source, the deposition sequence, and temperature-dependent thermal and mechanical properties. The results predicted by 3D FEA model are generally in good agreement with the measurements. Finally, the numerical and experimental results suggest that both deposition sequence and heat input affect welding distortion and residual stress distribution. Furthermore, the 3D thermal-mechanical FEA method can predict cylinder-type welding distortion.     

Analysis of transient temperature and residual thermal stresses in friction stir welding of aluminum alloy 6061-T6 via numerical simulation

Residual stress is lower in friction stir welding (FSW) compared with other melting weldment processes. This is due to being solid-state process in its nature. There are several advantages in utilizing stir welding process. Lower fluctuation and shrinkage in weldment metal-enhanced mechanical characteristics, less defects, and ability to weld certain metals otherwise impractical by other welding processes are to name just a few of these advantages. These have caused an ever increasing attention by the concerned to the process of FSW. In this investigation, three-dimensional numerical simulation of friction stir welding was concerned to study the impact of tool moving speed in relation with heat distribution as well as residual stress. Simulation was composed of two stages. Firstly, thermal behavior of the piece while undergoing the welding process was studied. Heat is generated due to the friction between tool and the piece being welded. In the second stage, attained thermal behavior of the piece from previous stage is considered as inlet heat of an elasto-plastic, thermo-mechanical model for the prediction of residual stress. Also, in the second stage, tool is eliminated and residual stress distribution is found after complete cooling of the piece and disassembly of the clamp. Material characteristic are introduced into the proposed model as temperature-dependent parameters. Obtained residual indicate that heat distribution along thickness varies and is asymmetrical enormously. Moreover, longitudinal residual stress in the weld which increases as speed of process and tool movement ascends. In the prediction of results of residual stress, only heat impact was studied. This was recognized as the main element causing minor difference in results obtained for simulation in comparison with that of actual experiment.     

Numerical analysis of welding residual stress using heat source models for the multi-pass weldment

Numerical prediction of welding-induced residual stresses using the finite element method has been a common practice in the development or refinement of welded product designs. Various researchers have studied several thermal models associated with the welding process. Among these thermal models, ramp heat input and double-ellipsoid moving source have been investigated. These heat-source models predict the temperature fields and history with or without accuracy. However, these models can predict the thermal characteristics of the welding process that influence the formation of the inherent plastic strains, which ultimately determines the final state of residual stresses in the weldment. The magnitude and distribution of residual stresses are compared. Although the two models predict similar magnitude of the longitudinal stress, the double-ellipsoid moving source model predicts wider tensile stress zones than the other one. And, both the ramp heating and moving source models predict the stress results in reasonable agreement with the experimental data.     

Investigation of welding residual stress of high tensile steel by finite element method and experiment

Due to varying temperature distribution of welding area during welding process, thermal stress is generated. It is known that the thermal stress forms residual stress. The welding residual stress has an important effect on welding deformation, embrittlement fracture, fatigue fracture, etc. In this paper, residual stress due to welding was numerically investigated by finite element method. To verify the results of numerical analysis, the residual stress of high tensile steel was measured by the hole-drilling method. Temperature change experimentally measured at the location of 3-mm-off-weld-bead, in addition, was compared with the numerical analysis. The above methodologies were applied to H-plate with 13.5mm thickness through MIG welding process. The distributions of the residual stress and the temperature distributions from the experimental and the numerical analyses were confirmed to be close.     

辅助热源影响焊接残余应力的研究

采用曲壳单元热弹性有限元法,对ＬＳＮＤ静态低应力无变形焊接控制技术中辅助热源影响焊接残余应力的规律进行了数值模拟。计算结果表明,辅助热源如与焊接热源同时冷却则对焊接残余应力的影响不大,只有焊缝冷却至低温阶段后再冷却的辅助热源才有利于降低焊接残余应力。     

残余应力对焊接接头CTOD设计曲线的影响

基于BISPD6493：1991初级评定，采用热弹塑性有限元分析方法，研究了残余应力和强度组配对横向裂纹平板对接接头CTOD设计曲线的影响规律。结果表明，强度组配和残余力对CTOD设计曲线具有明显的影响；残余应力对接头中的短裂纹影响较大，PD6493：1991初级评定不适用于接头中含有位于拉伸残余应力区内的短裂纹情形，随着裂纹尺寸的增大，残余应力的影响逐渐减弱；在应用PD6493：1991初级评定曲线对接头中的大裂纹情形进行评价时，将得出偏于保守的结果。     

分体式捣镐的焊接有限元模拟

介绍了铁路捣固车的工作原理、捣镐的失效形式以及国内外捣镐的特点和使用寿命。选择分体式捣镐为研究对象,运用ANSYS对捣镐的焊接过程进行模拟。采用高斯热源模型进行了焊接温度场数值模拟,通过ANSYS的APDL命令流、动态填充热流密度表,方便地实现了移动热源的加载,得到了焊接温度场和残余应力场分布数据,较好地模拟了实际焊接过程。仿真结果符合已有的焊接过程残余应力产生理论,验证了仿真过程的正确性。     

超声冲击消除残余应力频率参数的确定

建立模拟焊接过程的三维有限元模型,得到了焊接残余应力的应力场分布,通过对此焊接残余应力场的分布进行研究,可以对焊接结构的质量和使用性能进行预测。应用ANSYS的模态分析功能,得到了模型的固有频率,在固有频率下进行超声冲击消除残余应力会得到较好的效果,并验证了输入频率大于固有频率时,超声冲击消除残余应力的效果与在固有频率下冲击的效果差别不大。