在线测量薄板焊缝区的变形

针对薄板在堆焊过程中焊缝区发生较大塑性变形的问题,提出一种基于数字图像弱相关技术的光学非接触在线测量焊接变形的方法,在焊接及冷却过程对焊缝区域全场及关键点的变形状态进行跟踪测量,获取变形规律.对Q235薄板进行钨极惰性气体保护焊（TIG）堆焊试验,结果表明,垂直于薄板方向上的变形量远大于其余两个方向;薄板焊缝区在焊接过程中先呈凸起状,逐渐冷却后呈马鞍状;薄板焊缝关键点及焊缝区的面外变形量随焊接电流的增大而明显增大.此方法对验证薄板焊接变形的数值模拟预测和揭示焊接变形机理等具有重要的指导意义.     

焊接焊缝变形的测量研究

针对目前无法采用先进的测量手段获取精确的焊接焊缝变形规律,使得焊接矫正工艺往往不能达到预期效果,提出一种非接触在线全场测量焊接焊缝变形的方法。基于数字图像相关技术,结合传统氩弧焊焊接工艺,对焊缝关键点进行全程跟踪测量并获取变形规律。此方法对焊接变形机制研究提供依据,提供焊接矫正方法思路,对焊接工艺具有重要的指导意义。     

焊缝变形的研究

针对焊缝处在焊接过程中因产生大量残余应力而引起的板料发生塑性变形,提出一种基于数字图像的非接触在线测量焊接变形的方法,综合运用数字图像相关技术和双目视觉技术,全程跟踪测量焊缝处关键点,获取变形规律。此方法对研究焊接变形机理有重要的指导意义。     

ENiCrMo-3等级镍基合金单层带极电渣堆焊工艺研究

针对产品技术要求中ENiCrMo-3等级镍基合金堆焊层厚度大于等于4.5 mm、堆焊层表面及堆焊层表面以下3.2 mm处化学成分需满足ASME规范Ⅱ卷C篇SFA-5.11 ENiCrMo-3和弯曲性能合格的条款,采用单层带极电渣堆焊工艺增加堆焊厚度的方法取代常规工艺中采用双层带极电渣堆焊的方法,在平板上和筒体内壁两种工况下进行堆焊试验,摸索出了ENiCrMo-3等级镍基合金焊带单层电渣堆焊焊接工艺参数。试验结果表明,除焊接热输入相关变量外,上坡量对焊缝成形尤为重要,对比平板堆焊和内径1 620 mm筒体内壁堆焊的焊接参数可知,单层堆焊厚度大于等于4.5 mm时,两种结构下的适用焊接参数差异较大,平板堆焊参数不能适用于筒体内壁堆焊。     

薄板TIG堆焊屈曲变形的预测

针对TIG堆焊所引起的薄板复杂屈曲变形问题,采用基于热弹塑性理论的有限元法建立薄板焊接变形预测模型,提出了数字图像相关法对预测屈曲模型进行试验验证并设计了薄板焊接变形检测试验装置. 结果表明,基于数字图像相关技术的非接触变形检测方法能够全场动态获取堆焊屈曲变形数据,全面验证了焊接变形有限元预测模型,基于高斯热源模型、非线性瞬态热传导边界条件、材料高温性能参数等的热?力耦合热弹塑性预测模型具有较高的精度.薄板焊接变形冷却后呈马鞍形,结合动态温度场与应力场,对揭示焊接马鞍形屈曲变形机理具有重要的意义.     

Nd:YAG激光+脉冲MAG电弧复合热源规范参数对平板堆焊焊缝表面成形的影响

利用余高-熔宽比表示焊缝表面铺展性并与焊缝余高一起作为参数来评价复合热源平板堆焊焊缝的表面成形,通过试验研究了Nd：YAG激光＋脉冲MAG复合热源堆焊过程中焊接规范参数对复合热源平板堆焊焊缝表面成形的影响并分析了激光对复合热源堆焊焊缝表面成形的影响.研究结果表明,在电弧功率变化过程中,随着激光功率的增大,其对平板堆焊焊缝表面成形的影响也逐渐增大;焊接速度变化过程中,激光束能量的加入不仅改善堆焊焊缝表面成形还极大地提高了焊接速度;而在光丝间距和离焦量变化过程中,激光束对复合热源平板堆焊焊缝表面成形的影响很小.     

焊缝收缩力的数值模拟研究

数值模拟焊接变形的方法主要有热弹塑性有限元法和固有应变法,目前又提出一种更为简便的方法--焊缝收缩力法.阐述了焊缝收缩力的理论和计算方法,针对平板堆焊实例,通过热弹塑性有限元法分析得出焊接线能量与焊缝收缩力的关系.     

磁控大电流MAG焊的磁头优化及应用研究

从增强工程实用性、磁控效果、冷却效果和气体保护效果等角度出发,设计了两种新型的磁场发生装置,并进行了磁控大电流MAG平板堆焊和角焊缝焊接工艺试验.试验结果表明,采用所设计的磁场发生装置进行焊接时,焊接飞溅很小,焊缝成形良好,明显优于采用空心线圈作为磁控器件的焊接效果.     

CMT Cycle Step工艺参数对焊缝表面特征纹路及成形尺寸的影响

采用CMT Cycle Step焊接工艺进行平板堆焊正交试验,研究了送丝速度、焊接速度、熔滴数量和间隔时间四个参数对焊缝表面特征纹路及成形尺寸的影响,建立了各参数与焊缝表面鱼鳞纹步长S、焊缝熔宽B、堆焊层厚度h之间的回归模型.结果表明,随着焊接速度、熔滴数量和间隔时间的增大,焊缝表面鱼鳞纹步长S呈逐渐增大的趋势.适当减小焊接速度和间隔时间,可有效减小焊缝表面高度差Δh,提高焊缝表面成形质量.随着送丝速度和熔滴数量的增大,焊缝熔宽B和堆焊层厚度h均逐渐增大;随着焊接速度的增大,焊缝熔宽B和堆焊层厚度h逐渐减小.根据理论分析和回归分析得到准确性较高的回归方程,为预测焊接焊缝成形以及优化焊接工艺参数提供理论依据.     

低相变点焊缝金属接头的焊接残余变形

试验中低相变点焊缝金属的固态相变温度在190℃左右，由于焊缝金属相变体积膨胀使其焊接接头的焊接残余变形降低。利用低相变点焊条LTrE和普通焊条E5015通过V形坡口对接接头和半V形坡口T形接头的角变形以及平板堆焊试验，探讨了焊缝金属固态相变对焊接变形的影响。两种接头角变形试验结果表明，LTTE焊条试件具有较小的角变形，其角变形分别为E5015焊条试件角变形的69．1％和64．3％；LTTE焊条平板堆焊试件出现反变形，在该试验条件下反变形挠度为-1．9mm，而E5015焊条试件的正变形挠度为2mm。这些试验结果为减小和控制焊接残余变形提供了一条有效的方法。     

Effects of heat input on welding buckling distortion by experimental measurement method

An experimental method based on digital image correlation technology is proposed to measure welding buckling distortion for bead-on-plane with tungsten inert gas welding. This study focuses on the effect of welding heat input for dynamic buckling and full-field distribution. The experimental results demonstrate that heat input has a great influence on welding buckling distortion. The longitudinal shrinkage of the weld bead is in direct proportion to the heat input. In the weld bead, the longitudinal plastic strain is small, while the transverse strain is large. The key points on the line, that is perpendicular to the bisector of the weld bead, experience a distorted trend of positive increase, constant displacement, negative increase and stable displacement, although the heat inputs are different.     

薄板焊接特征屈曲的数值分析

在薄板焊接中,由于局部加热和迅速冷却产生了沿焊缝方向的焊接收缩应力,而导致焊接薄板发生屈曲变形.本文采用以热弹性为基础的有限元数值模拟与薄板结构稳定理论相结合的方法,对薄板焊接屈曲变形进行计算机数值模拟,并且分析了约束类型、单元尺寸、长宽比对薄板焊接屈曲载荷的影响,最后得出焊接薄板的屈曲失稳判据.     

薄板高强铝合金LY12CZ焊接工艺参数的优化

从力学角度出发，通过调整焊接温度场，控制焊缝及近缝区的应力应变发展，实现了高强铝合金LY12CZ薄板的低应力少变形无热裂焊接。运用正交试验设计来安排试验、筛选因子，并用一次回归正交设计调优运算优化因子的匹配，找到了影响铝合金薄板焊接变形的主要因子和最佳工艺参数匹配，揭示了主要工艺参数对减小变形效果的影响规律。     

Mitigation of welding induced buckling distortion using transient thermal tensioning

Abstract

Welding induces residual stresses in structures and may cause buckling distortion if the stresses exceed the critical buckling stress of the structure. Reducing the welding heat input or increasing the structural stiffness reduces or eliminates buckling distortion. However, where, because of the design constraints, structure geometry and weld size are fixed, the transient thermal tensioning process is effective in reducing buckling distortion. An experimental verification and demonstration of transient thermal tensioning for minimising welding induced buckling distortion is presented. Conventional welding was carried out to demonstrate buckling distortion and establish a baseline case. Buckling distortion was eliminated using transient thermal tensioning during welding under the same welding conditions. After buckling distortion was eliminated, angular distortion became evident, which was eliminated using mechanical restraints alongside transient thermal tensioning. Residual stress measurements were obtained using the blind hole drilling method and a comparison of residual stresses for the baseline panel and for the panel with transient thermal tensioning is presented.     

Predictive analysis of buckling distortion of thin-plate welded structures

The welding buckling distortions of thin-plated structures were investigated based on finite element methods.An engineering treatment method for predicating the buckling distortion was proposed.The equivalent applied thermal-load was used to simulate the welding residual stress,thus the calculation of complex welding distortion can be transformed into 3D elastic structural applied-load analyses,which can reduce the quantities of calculating work effectively.The validation of the method was verified by comparison of the numerical calculation with experimental results.The prediction of buckling distortion for side-walled structures of passenger train was performed and the calculation was in agreement with measuring results in general.It is shown that the main factors for producing the buckling are the intermittent fillet and plug weld during welding general.It is shown that the main foactors for groducing the buckling are the intermittent fillet and plug weld during welding the stiffened beams and columns to the panel.     

A new method for welding aluminum alloy LY12CZ sheet with high strength

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Stress and distortion mitigation technique for welding titanium alloy thin sheet

Abstract

A stress and distortion mitigation technique for Gas Tungsten Arc Welding (GTAW) of titanium alloy Ti–6Al–4V thin sheet is presented. The proposed welding technique incorporates a trailing heat sink (an intense cooling source) with respect to the welding torch, and it is also called the Dynamically Controlled Low Stress No-Distortion (DC-LSND) technique. The development of this mitigation technique is based on both detailed welding process simulation using the advanced finite element technique and systematic laboratory experiments. The finite element method is used to investigate the detailed thermomechanical behaviour of the weld during conventional GTAW and DC-LSND GTAW. With detailed computational modelling, it is found that by the introduction of a heat sink at some distance behind the welding arc, a saddle shaped temperature field is formed as a result of the cooling effects of the heat sink; the lowest temperature exists in the zone where the heat sink is applied. High tensile action on the surrounding zone is generated by abrupt cooling and contraction of the metals beneath the heat sink, which increases the tensile plastic strain developed during the cooling process and decreases the compressive plastic strain developed in the heating process, and therefore mitigates the residual stresses and plastic strains within and near the weld. The experimental results confirmed the effectiveness of the DCLSND technique and the validity of the computational model. With a proper implementation of the DC-LSND technique, welding stress and distortion can be reduced or eliminated in welding titanium alloy Ti–6Al–4V thin sheet, while no appreciable detrimental effects are caused on the mechanical properties of welded joints by applying the heat sink in the GTAW process.     

Q345B钢板焊接热循环及实时角变形测试

对Q345B钢板进行多层多道焊接,使用K型接触式热电偶测温模块和激光位移传感系统测量焊接过程中的热循环和角变形。结果表明,多层多道焊的热循环峰值温度随焊道的逐渐靠近而升高;距离焊缝越近,峰值温度越高,对应的升温速度也越快;焊接角变形主要产生于焊接阶段,表现为逐渐增加,而在层间冷却阶段很小,最终焊接角变形约为4.78°。