基于BP神经网络遗传算法的薄板CMT点焊变形

焊接是汽车车身制造的一个关键环节,焊接质量的好坏严重影响汽车车身质量,所以焊接参数的选择至关重要. 针对薄板焊接质量控制问题,论文利用BP神经网络解决非线性问题的优势,建立焊接变形量与工艺参数之间映射关系模型;结合遗传算法构建基于遗传神经网络焊接的工艺参数优化系统;同时设计正交试验,将该方法与正交试验法相对比. 结果表明,该方法可以有效地实现CMT(cold metal transfer)点焊焊接变形预测与工艺参数优化. 通过预测模型给出合理参数,指导钢薄板和铝合金薄板的CMT点焊变形试验,提高焊接的效率.     

基于正交试验的铝合金薄板脉冲MIG焊参数优化方法研究

针对铝合金薄片MIG焊接对能量控制精度要求高、工艺参数匹配困难的问题,通过对2 mm铝合金薄板的工艺参数进行的三因素三水平的正交试验,和对试验参数的最优组合进行分析,总结出一种工艺参数匹配及优化的方法,并利用此方法完成了对1mm铝合金薄片的焊接,证明了这一方法的有效性.     

铝合金薄板氩弧焊变形控制技术探讨

本文主要探讨铝合金薄板结构的焊接应力变形及其预测与控制,为了有效地控制焊接应力变形并通过焊接工艺试验,采用预应变法辅助配合合理的夹具使用形式和布置,能够明显提高控制焊接应力变形的效果,减小和控制焊接变形。     

LD10随焊预拉伸作用位置的有限元分析

对于铝合金的焊接其焊后残余应力导致的焊接变形,尤其对于薄板的焊接其焊接变形问题更为严重。本文运用MSC.Marc大型有限元模拟软件对LD10铝合金的预拉伸工艺进行三维模拟,为优化铝合金预拉伸工艺的工艺参数,提供了理论依据和指导。结果说明:在弹性应力范围内,随着预应力作用范围的增大,试件的纵向残余拉应力峰值、纵向残余弹、塑性变形量均逐渐减小。分析认为,预拉伸应力部分抵消了焊接区因局部加热而导致的压缩塑性变形,减小了焊接残余应力,从而起到控制薄板焊接失稳变形的目的。     

基于田口法的高硅铝合金超高旋转速度搅拌摩擦焊接工艺优化

超高旋转速度搅拌摩擦焊借助超高旋转速度摩擦热量实现了薄板高硅铝合金的连接,这一方法大大降低了搅拌摩擦焊接的轴向力,减小了焊接变形,对焊接薄板铝合金具有独特的优势。文中以焊缝成形质量和焊接接头抗拉强度作为响应值,基于田口法对影响焊接质量的主要焊接工艺参数(旋转速度、焊接速度和下压量)进行试验设计,优化高硅铝合金超高旋转速度搅拌摩擦焊工艺。结果表明,焊接速度和下压量是显著影响因素,最优焊接工艺参数焊接速度为60 cm/min,旋转速度为14 000 r/min,下压量为1.8 mm。这一工艺条件下高硅铝合金超高旋转速度搅拌摩擦焊接接头的最大抗拉强度为129 MPa,达到母材高硅铝合金抗拉强度的97%。     

基于田口法的高硅铝合金超高旋转速度搅拌摩擦焊接工艺优化

超高旋转速度搅拌摩擦焊借助超高旋转速度摩擦热量实现了薄板高硅铝合金的连接,这一方法大大降低了搅拌摩擦焊接的轴向力,减小了焊接变形,对焊接薄板铝合金具有独特的优势。文中以焊缝成形质量和焊接接头抗拉强度作为响应值,基于田口法对影响焊接质量的主要焊接工艺参数(旋转速度、焊接速度和下压量)进行试验设计,优化高硅铝合金超高旋转速度搅拌摩擦焊工艺。结果表明,焊接速度和下压量是显著影响因素,最优焊接工艺参数焊接速度为60 cm/min,旋转速度为14 000 r/min,下压量为1.8 mm。这一工艺条件下高硅铝合金超高旋转速度搅拌摩擦焊接接头的最大抗拉强度为129 MPa,达到母材高硅铝合金抗拉强度的97%。     

基于正交试验的T形接头焊接工艺优化

焊接变形可以直观地看到,控制变形手段也非常多. 焊接残余应力分布复杂,关键位置残余应力大小对产品有着很大的影响. 文中利用焊接数值模拟和试验相结合的手段,采用单因子和多因子正交试验相结合的设计方法,以焊接残余应力为评价指标,对T形接头焊接的工艺参数进行优化设计,获得了T形接头的残余应力分布状况. 结果表明,拼焊间隙为2 mm以下时,焊缝宏观形貌满足要求;焊接速度对焊接残余应力的影响最为显著,其次为送丝速度和拼焊间隙. 利用数值模拟和试验相结合的方法,优化了焊接工艺参数,降低了焊接残余应力的峰值,有效地减少了试验次数,节约了成本.     

LD10薄板随焊锤击工艺的有限元分析

对于铝合金的焊接其焊后残余应力导致的焊接变形,尤其对于薄板的焊接其焊接变形问题更为严重。本文运用MSC.Marc大型有限元模拟软件对LD10铝合金的随焊锤击工艺进行三维模拟,为优化铝合金随焊锤击工艺的工艺参数,提供了理论依据和指导。结果说明:由于焊接热源后的锤击作用使得作用区域的金属发生了塑性延展,从而导致工件的纵向残余拉应力峰值、纵向残余弹、塑性变形量均逐渐减小。分析认为,随焊锤击能够减少焊接区因局部加热而导致的压缩塑性变形,降低了焊接残余应力,从而起到控制薄板焊接失稳变形的目的。     

液体火箭发动机关键部件自动焊工艺

以发动机关键件之一的燃气发生室为例,针对其具体结构合理设计了焊接试件,运用正交试验的方法对焊接工艺参数进行筛选,得到影响焊接质量的主要影响因子和最优工艺参数匹配。最后编制了相应的焊接工艺管理信息系统,可以方便的新增、修改、删除、浏览、查询和排序焊缝参数、焊接规范和焊接效果等,在实际生产中受到用户好评。     

应力应变、疲劳与脆断、断裂力学

薄板结构焊接残余应力的数值分析;铝合金薄板焊接应力三维有限元模拟;QFP器件不同引线材料对焊点可靠性影响的有限元分析;基于ABAQUS平台对球冠结构焊接变形的数值试验;铝合金搅拌摩擦焊接头残余应力分布;立方氮化硼超硬磨料与45钢钎焊接头残余应力有限元分析;纵向磁场对低碳钢MIG焊焊缝组织及性能的影响。     

随焊激冷减小铝合金薄板的焊接变形

研究了随焊激冷减小铝合金薄板焊接变形的效果及夹具的散热条件对该效果的影响,研究表明,随焊激冷能够减小铝合金薄板的焊接变形,其效果受夹具自身冷却作用影响很大。随着夹具散热条件的降低,随焊激冷所起的作用增强,但降低焊接变表的效果仍不够明显,适当预热夹具本身可以减小焊接变形,但更重要的是预热使激冷造成了温差拉伸,因此获得了最小的焊接变形。     

NUMERICAL SIMULATION OF CONTROLLING IN TITANIUM ALLOY SHEETS WELDING RESIDUAL STRESS BY TRAILING PEENING

It is a promising and new technology to apply welding with trailing peening to control welding stress and distortion of titanium alloy. Numerical simulation of conventional welding and welding with trailing peening of the titanium alloy sheet is carried out, using nonlinear finite element theory and the engineering analysis software MARC. The result shows that welding with trailing peening technology reduces longitudinal residual stress in welding joint effectively, and it is more effective to reduce residual stress to peen the weld than to peen the weld toe. It is a effective result that other technolooy and method used in welding can never achieved.     

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.     

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

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Influence of local heat treatment on residual stresses in electron beam welding

Abstract

Electron beam welding (EBW), as a high performance welding method, is also subject to requirements of high integrity welds which particularly include residual stresses affecting distortion and fatigue behaviour. In this context multiple beam technique may provide new applications of specific thermal weld treatment. The present work introduces a promising method of local post-heating in a certain distance to the current welding location applying multiple beams for the reduction in residual stresses in EB welded sheet metals. The conducted investigations include finite element analysis (FEA) and stress measurements in the weld seam area. Using a systematic approach within the FEA decisive process parameters are optimised with reference to the achievable reduction in residual stress. All simulation results are validated by experiments applying strain gauges for the stress measurement. Both simulations and experiments revealed a considerable decrease in residual stress achievable by appropriate positioning of additional heat sources combined with the right power input and beam focusing.     

铝合金薄板高斯脉冲MIG焊

提出了GAUSS-MIG焊模型,成功在2 mm和3 mm厚度的铝合金薄板进行了焊接试验.通过分析试验采集的信号,发现焊接电流电压波形规整、分布有规律,重复性好,能量输入集中,弧长稳定,证明了GAUSS-MIG焊的焊接过程平稳.GAUSS-MIG焊焊缝的力学性能比传统的铝合金双脉冲焊有一定的提高,并且焊缝外观鱼鳞纹清晰工整,表面光亮,熔高和熔深合适,焊接过程几乎无飞溅发生,电弧声柔和,焊接质量好.     

Dynamic process of angular distortion between aluminum and titanium alloys with TIG welding

The dynamic process of welding angular distortion in the overlaying welding of 5A12 aluminum alloy and BT20 titanium alloy was investigated. Information of dynamic distortion was got via self-made welding dynamic measuring system. Research results show that the characteristics of dynamic distortions at various positions of the plate edge parallel to the weld of 5A12 and BT20 alloy are different. Comparison between 5A12 and BT20 alloy shows that transverse shrinkage and downward longitudinal bending are main factors influencing the dynamic angular distortion processes of 5A12 and BT20 alloy under welding heat input of 0.32 kJ/mm. The angular distortion of 5A12 alloy is completely inversed with welding heat input increasing to 0.4 kJ/mm, and the position of weld center and buckling distortion become the primary factors.     

Effect of Ti content on TiN morphology,microstructure and toughness in coarse‐grained heat affected zone of Ti‐containing steels

It is well known that weld distortion, which has a negative influence on material properties, structural fabricability and structural integrity, should be controlled appropriately. There are many methods to control or reduce weld distortion, but most of them involve some costly process in addition to welding. In-process control of weld distortion becomes more preferable than post-welding process or other methods, when manufacturing efficiency is considered. In recent years, in-process control welding by additional cooling has been proposed as one of techniques for reducing weld distortion and partially applied for thin-plate structure in industries. However, the effectiveness of additional cooling method has not yet been fully clarified. In this study, the effectiveness of additional cooling method and appropriate cooling condition for effective reduction in weld distortion are investigated by three-dimensional thermal elastic–plastic analysis. In addition, the effect of locally cooled temperature distribution on generation behaviour of plastic strain is discussed. As a result, it is concluded that the effectiveness of additional cooling and appropriate cooling condition for reduction in weld distortion are dependent on weld distortion under consideration and welding conditions. Especially, it is necessary for reduction in weld distortion to set the cooling torch at the appropriate position. For example, in order to reduce angular distortion effectively, the appropriate cooling position is dependent on the mechanical melting length during welding.     

钛合金带热沉钨极氩弧焊中热沉作用

采用数值模拟和实验相结合的方法研究了钛合金TC4薄板常规及带热沉的钨极氩弧焊焊接过程中温度及应力应变的分布,考察了热沉对温度场和应力应变场的影响规律,探讨了使用该技术实现应力和变形控制的机理.结果表明:带热沉的钨极氩弧焊焊接过程中,紧随热源之后热沉急冷作用使得试件形成马鞍形温度场,而热沉作用部位温度最低.热沉作用部位的急冷收缩对周围金属产生拉伸作用,使得焊缝及近缝区金属升温过程中产生的压缩塑性应变减小,冷却过程中产生的拉伸塑性应变增大,接头中不协调应变减小,残余应力降低.实验测量与有限元模拟结果吻合良好,证实了采用热沉控制应力与变形的有效性和有限元模型的正确性.     

用旋转挤压方法控制薄板的焊接变形

提出了旋转挤压控制薄板焊接变形的新方法,它足利用特定形状的挤压头对焊缝及近缝区金属进行旋转挤压,产生拉伸塑性应变,减小甚至抵消残余压缩塑性应变,以此来消除焊接残余变形.该方法处理后的焊道表面平整光滑,减小了应力集中.结果表明,旋转挤压法能将薄壁构件焊接变形降到非常低的水平,选择适当的工艺参数,该方法能将焊接残余变形控制在常规焊接状态的3%以下.旋转挤压控制薄板焊接变形的效果与多个工艺参数有关,只有当各个工艺参数取值适当且匹配良好时,才能取得良好的焊接变形控制效果.