电磁锤随焊锤击控制焊接应力变形新工艺

通过用电磁锤锤头对焊后尚处于高温状态的焊趾和焊缝区金属施加一定频率的锤击力,迫使焊趾处的金属向焊缝中心流动,抵消致裂拉伸应变,达到防止焊接热裂纹的目的;同时使焊缝金属在纵向和横向充分延展,降低了焊接残余应力.试验结果表明:该工艺简单可靠、轻便灵活,不但能控制焊接变形、防止焊接热裂纹的产生,而且能使焊缝组织均匀细化;与未锤击时相比,试件焊缝纵向残余应力平均下降了约90%.     

随焊超声波激振法控制铝合金薄板焊接应力及变形

从力学角度出发提出随焊超声波激振控制高强硬铝合金薄板焊接变形的新方法,阐明其控制焊接应力及变形的机理。基于数值模拟分析,利用Marc建立铝合金薄板的随焊超声波激振热力耦合模型,找出最优焊接参数以及加载冲击与热源的最佳距离。利用自行研制的随焊超声波激振装置进行焊接试验。结果表明：激振距离为22 mm时,板长方向中截面残余拉应力峰值由常规焊的248 MPa下降到63 MPa,压应力峰值从-77 MPa降低到-27 MPa,低于薄板的临界失稳应力,薄板挠曲变形完全消失,且板边最大挠度由8.66 mm下降到0.9 mm。试验结果与模拟结果吻合较好。     

轿车车门铰链的焊接变形II.凸焊焊后残余应力及变形分析

针对轿车车门凸焊后会产生焊接变形的具体情况,建立了一个铰链和加强板的二维有限元凸焊模型。利用凸焊工艺过程分析得到的凸焊焊接温度场分布结果,在自由状态下对模型进行了热应力分析,获得了凸焊焊接热变形和焊后残余应力的分布情况。并结合轿车车门焊接的实际,分析了焊后车门铰链的变形趋势,取得了与试验结果相一致的结论。     

基于电磁控制的随焊锤击对焊接残余应力的影响

针对焊接残余应力难以消除的特点,结合几种能够实现随焊锤击功能的方案,提出了一种基于电磁控制的随焊锤击消应力的工艺方法,并研制出了基于电磁控制的随焊锤击试验装置.采用小孔释放法测量随焊锤击前后的残余应力,通过对比和试验分析得出了影响电磁锤随焊锤击效果的主要参数,其中锤击力和锤击温度对焊接残余应力的影响显著.     

钛合金薄板焊接应力的随焊锤击控制

将随焊锤击技术应用于钛合金薄板焊接应力与变形控制,分别对TC4钛合金薄板进行常规焊和采用随焊锤击技术对焊接应力与变形进行控制,结果证实,随焊锤击工艺有效地减小了薄板焊件的挠曲变形,焊缝的纵向残余应力减小到常规焊的1／10,最大焊接挠曲变形由常规焊的15mm减小为5mm。     

轿车车门铰链的焊接变形 II.凸焊焊后残余应力及变形分析

针对轿车车门凸焊后会产生焊接变形的具体情况,建立了一个铰链和加强板的二维有限元凸焊模型。利用凸焊工艺过程分析得到的凸焊焊接温度场分布结果,在自由状态下对模型进行了热应力分析,获得了凸焊焊接热变形和焊后残余应力的分布情况。并结合轿车车门焊接的实际,分析了焊后车门铰链的变形趋势,取得了与试验结果相一致的结论。     

随焊激冷控制铝锂合金焊接接头残余应力规律研究

采用ABAQUS软件对不同焊接工艺条件下2 mm铝/锂异种金属薄板搅拌摩擦焊过程进行数值模拟,通过建立搅拌摩擦焊热源与干冰冷源模型,将空冷和随焊干冰激冷条件下的温度场与应力场进行对比分析,研究发现：焊接温度场呈现前小后大的椭圆形分布,在垂直于焊缝方向的残余应力表现为“M”型趋势,并且残余应力的峰值位于搅拌头轴肩作用区的边缘位置。相较于空冷条件,随焊激冷工艺条件下AA2060焊件上表面的应力峰值降低约13%。在相同激冷距离下,随着激冷强度降低,热源与冷源间的温度梯度增大,焊件的残余应力降低,结果表明随焊激冷技术可以有效控制铝/锂薄板焊接残余应力。     

不同点固焊形式对焊接变形和残余应力的影响

借助有限元分析手段对不同点固焊形式的对接焊焊接过程进行模拟,经分析得到焊接变形和应力分布情况,采用实验手段验证试验结果。结果表明,点固焊位置相同,长度越长,获得的变形量越小;起、收弧的两端面点固焊变形在起、收弧两侧翘起,焊缝位置点固焊翘起的位置发生在与焊缝位置平行的两侧自由端;点固焊长度越长,仿真和实测结果的残余应力分布波动性越大;在起、收弧两端面点固焊获得的残余应力峰值最小;起、收弧两端面点固焊、点固焊2处残余应力值均降低,点固焊3处残余应力值增大。证明了有限元模型的正确性和有效性。     

随焊干冰激冷冷源尺寸对焊接残余应力影响的有限元分析

文中利用米粒状干冰颗粒作为冷却介质进行随焊激冷,通过将干冰颗粒与压缩空气混合,借助喷枪从喷嘴直接喷射于试板上,干冰颗粒与试件接触瞬间升华带走大量热量,实现局部快速冷却.基于热弹塑性有限元方法,对1561铝合金随焊激冷焊接的方法进行了模拟,分析不同长度和宽度的矩形冷源对随焊激冷控制残余应力的影响,从而对干冰喷嘴出口形状设计进行指导,以优化随焊激冷控制焊接应力与变形的效果.结果表明,最佳矩形冷源的长宽为40 mm×25 mm,板中心纵向残余拉应力由162 MPa降低为零,板两端纵向残余压应力由常规焊接的59.3 MPa减小到20.4 MPa,减小大约65.6%.     

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

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Controlling welding residual stress and distortion by a hybrid technology of transient thermal tensioning and trailing intensive cooling

ABSTRACT

A new method of hybrid technology for controlling welding residual stress and distortion is proposed, which contains the transient thermal tensioning with two symmetrical heat sources ahead and the trailing intensive cooling with a cooling source behind the welding heat source during the welding process. Welding temperature, stress and distortion were compared and discussed under different welding processes by experimental and numerical methods. The results reveal that the hybrid technology adjusted the temperature field during welding and redistributed the longitudinal residual stress of welding joint. Thus, the welding residual distortion was reduced. Compared with conventional metal inert gas welding, the reductions of the welding residual stress and distortion of joint by the hybrid technology reached 65% and 58%, respectively.     

残余应力的本质及其调整

残余应力是各种加工工艺产生的一种现象,是能量储存不均匀造成的,是材料内部不均匀塑性变形的结果,其本质是晶格畸变,而晶格畸变很大程度上是由位错引起的。根据等直纯弯曲梁建立了残余应力的力学模型,探讨了残余应力调整的方法。     

Low stress no distortion welding for aerospace shell structures

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大型构件T形焊接接头横向变形的研究

T形焊接接头是许多大型焊接结构件的主要构成方法。由于残余应力的存在,焊接后构件不可避免会产生变形,这种变形用纯理论方法难以解决,但可以结合构件对T形接头横向变形进行研究。本文重点分析了多个T形接头焊接的工艺试验结果,通过对试验数据的分析,得出了对T形接头焊接构件的横向变形的经验公式。     

Characteristics of welding distortion/residual stress generated by fillet welding with laser beam and verification of generality of its highly accurate prediction

It was found that the characteristics of welding distortion and residual stress generated by laser beam welding (LBW) had the same tendency as those by arc welding but that the absolute value was small. Moreover, the process of LBW is quite different from that of arc welding, the validity and generality of the dominant factors to predict high accuracy welding distortion and residual stress generated by welding could be verified by the high accurate prediction of welding distortion and residual stress which had been proposed based on arc welding. Inherent force was proposed as a parameter which could indicate the magnitude of compressive residual stress, which might influence the load-carrying capacity. Although inherent forces with LBW were 40% that of arc welding, it was found that control of welding heat input was important so as to improve the load-carrying capacity.