焊接后热与焊后热处理温度对焊接残余应力松弛的试验研究

针对工程实际，研究了焊接后热与焊后热处理温度对焊接残余应力松弛的影响，结果表明：在一定温度下，焊接后热对焊接残余应力的松弛效果不明显，而焊后热处理可以大幅度地消除焊接残余应力。     

Q235钢经逆焊接处理后抗腐蚀及疲劳性能的研究

介绍了采用逆焊接加热处理的方法后,Q235钢抗应力腐蚀及抗疲劳性能的影响及机理.在本实验中将Q235钢试件分别进行250℃和3500℃加热处理,再用冷水只对焊缝处进行快速冷却,使焊接区获得比相邻区低的负温差,实现调整和消除焊接残余拉应力的目的.实验结果表明,逆焊接加热处理有效的降低了焊接残余应力,减缓了应力腐蚀速率,提高了Q235钢的抗疲劳性能.     

机械应力消除法对焊接残余应力的影响

大直径全焊接阀体球阀制造的最后一道工序是焊接,由于采用橡胶圈密封,为防止密封圈的损坏,导致密封性能降低,焊后不能采用焊后热处理消除焊接残余应力。为了控制阀体焊接残余应力,选择机械应力消除法,建立阀体机械应力消除法的加载压力与时间的关系曲线,采用有限元分析和试验相结合的方法,研究机械应力消除法对焊接残余应力的影响。机械应力消除法前后采用盲孔法测量阀体外表面的残余应力。结果表明,采用二维轴对称有限元法可以模拟机械应力消除法过程,机械应力消除法可以降低阀体外表面轴向应力和环向应力的峰值,使残余应力分布更加均匀,可以作为焊后热处理的替代工艺。     

焊接残余应力对超声波冲击处理焊接接头疲劳性能的影响

采用含高值焊接残余应力的非承载纵向角接接头进行了Q235B钢焊态与超声波冲击态的疲劳对比试验,研究了焊接残余应力对超声冲击处理焊接接接头疲劳性能的影响规律。结果表明:焊接残余应力对超声波冲击处理后焊接接头疲劳性能的影响较小。使用不含高值焊接残余应力的小试件来评估超声波冲击处理对相同接头形式及板厚的大型焊接结构疲劳性能的改善程度可能是偏于安全的。     

TC4钛合金磁控窄间隙TIG焊试板热处理前后三维应力

针对100 mm和31 mm厚TC4钛合金磁控窄间隙非熔化极惰性气体保护焊(Tungsten inert gas, TIG)试板,采用压痕应变法测量表面残余应力分布,采用全释放应变法测量厚度方向的三维残余应力分布。结果表明,两种厚度试板的焊接残余应力数值有所不同:100 mm厚试板表面纵向和横向残余应力峰值高达600～700 MPa,接近材料屈服强度的70%～80%;31 mm厚试板表面纵向和横向残余应力峰值较低,仅达到材料屈服强度的40%～50%。两种厚度残余应力差异较大的原因主要由较大厚度下横向收缩的累积效应造成。经过650℃的焊后真空热处理,两种厚度的焊接试板纵向和横向应力均显著降低,应力降低幅度最高超过50%,剩余残余应力峰值均不超过200 MPa,焊缝处沿厚度方向分布的各向残余应力均接近零值,表面残余应力出现了重新分布。     

消除旋挖钻机动臂焊接残余应力测试方法研究

<正>旋挖钻机动臂用于连接其上车和钻桅三角架,是旋挖钻机作业时的主要承载结构件之一,承受着较大的振动和冲击载荷。动臂焊接完成后的焊接残余应力,直接影响其承载能力和疲劳寿命。本文通过试验对比方法,探讨采用施工作业方法消除焊接应力的效果。1.消除焊接残余应力方法(1)热处理为消除结构件焊接后的残余应力,通常采用热处理方法。但动臂结构尺寸较大,对热处     

焊接构件热处理工艺控制要点

为保证焊接构件性能与质量,提高焊缝金属的塑性,消除或减少焊接残余应力,防止产生裂纹,必要时需对焊接构件进行热处理。根据热处理工序与焊接工序的先后顺序,常把焊接构件的热处理分为预热处理、后热处理和焊后热处理3种。     

焊接残余应力测试方法的研究

在同一焊接试板同一部位分别用钴孔法及X衍射法测量焊接残余应力,通过分析对比发现钻孔法测试残余应力结果是可信的,而X射线衍射法所测得的残余应力值应减去钢板表面原有的轧制残余应力后才是焊接残余应力。本文还把上述两种方法的测试结果与Masubuchi提出的对接焊缝内纵向残余应力的分布进行比较,提出了工程中估算残余应力的方法。     

P92钢管道焊接残余应力场研究

采用红外热成像仪测试了P92钢管道焊接温度场,并采用X射线衍射方法对P92管道焊接接头热处理前后的残余应力分布进行了测试.采用有限元方法对P92钢焊接温度场进行了计算和分析,并采用间接法用温度场结果计算残余应力场.分析比较了焊后热处理前后的焊接残余应力变化情况,证明焊后热处理对焊接残余应力具有一定的消除作用.     

6061铝合金薄板焊接应力与焊接变形

研究了6061铝合金薄板TIG焊焊接应力、焊接变形与焊接电流、焊接电压和板材尺寸的关系.随着焊接线能量的增加,铝合金的纵向和横向收缩变形增加;随着板的长度的增加,由于约束增加,板的纵向残余变形减少,厚度方向的抗弯增大,横向变形增大.板焊后,焊缝处受拉应力,而紧靠焊缝的母材处却受压应力,其余部分受拉应力且焊接线能量越大,残余应力越大.     

超声波消除铝合金焊接件残余应力的机理研究

介绍了残余应力的产生、影响及铸统消除焊接残余应力的方法和原理,并从宏观（应力应变）和微观（位错理论）两个方面阐述了利用超声波消除焊接残余应力的机理;利用盲孔法对铝合金焊接板残余应力消除前后进行了测量,其消除效果可达到38．7％,并采用金相分析的方法对焊缝组织进行了位错分析,证明经过超声处理后在焊缝组织中晶体产生位错滑移并细化了晶粒达到应力释放的目的,从而进一步证实了该方法的有效性.     

Effects of initial condition of steel plate on welding deformation and residual stress due to welding

The effects of initial deflection and initial residual stress in steel plate on the out-of-plane deformation and residual stress due to welding are investigated from analysis results of thermal elastic-plastic FEM modeling with large deflection theory. Initial residual stress due to plate forming has very little effects on welding deformation and welding residual stress. For initial deflection, with concave profile (Type I), welding induced deformation has the same type as initial deflection and its magnitudes are small. When initial deflection is in the direction parallel to weld Une (Type II), welding induced deformation has minor variations. When initial deflection is bended in the direction normal to weld line (Type III), welding deformation was largely generated along the width direction of the steel plate. On the other hand, the variation in type of initial deflection does not affect the residual stress and plastic strain.     

双湿式搅拌机底部框架焊缝结构微区残余应力数值模拟

运用有限元软件ANSYS对双湿式搅拌机底部框架焊接过程进行了数值分析.采用高斯热源模型模拟手工钨极氩弧焊源,利用APDL编写循环程序实现热源的移动,得到双湿式搅拌机底部框架焊后的变形和残余应力场.从焊缝结构微区的Von Mises等效应力分布云图和节点的残余应力分布曲线可见:整个结构的焊后残余应力均为压应力,其值远小于材料的屈服强度,最大残余应力发生在沿焊缝方向上,从垂直焊缝方向的残余应力分布曲线可见,在焊缝处横向残余应力发生跳跃变化.     

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.     

超长箱形结构现场对接焊接的应力分析及工艺方案

分析了箱形结构对接板在自由状态、受到约束状态、载荷作用下和工作应力与残余应力叠加时施焊的应力状态,探讨了降低焊接残余应力水平、提高现场焊接质量的工艺方案。指出了2段梁在对接焊接时,降低约束作用、减小残余应力是制订箱形梁对接工艺的关键。     

Laser welding of Haynes 188 alloy sheet: thermal stress analysis

Laser welding of Haynes 188 alloy sheets is carried out. Temperature and stress fields developed in the welding section are predicted numerically incorporating the finite element algorithm. The microstructural changes in the welding region are examined using the optical and electron scanning microscopes. The microhardness variation across the weld zone is measured and associated with the residual stress formed in this region. It is found that the microhardness follows the residual stress distribution in the weld core. The maximum residual stress is less than the elastic limit of the substrate material.     

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。     

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.     

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.     

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。