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焊接工艺对薄板结构焊缝区残余应力的影响 总被引:1,自引:0,他引:1
采用焊接温度场与热应力场非耦合的方式,对薄板结构焊缝区残余应力进行了热-弹塑性有限元分析,模拟了连续焊缝焊接热输入以及施焊断续焊缝时薄板两端张力大小对焊后残余应力的影响.结果表明,残余应力峰值与焊接热输入无关.降低热输入,可以减小塑性变形区宽度,并且使远离焊缝处的压应力数值减小,这将减小焊后薄板的失稳变形.焊接过程中对薄板两端施加拉力,焊后可以减小施力方向的残余应力峰值,但并不影响拉伸区的宽度,从而适当增大薄板两端的拉力可以减少焊接变形的产生. 相似文献
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为了对大面积厚板拼焊平台结构进行焊接变形预测,首先进行了缩比件焊接试验,并测试了焊接过程中的角变形,然后进行了实际焊道数量及焊道集中分组后缩比件的焊接数值模拟,验证了焊接有限元模型输入的准确性及焊道集中分组方案的合理性;最后根据建立的焊道集中规则建立了平台结构的焊接有限元模型,进行了焊接变形的预测.结果表明,实际焊道数量及焊道集中分组后缩比件焊接角变形的数值模拟结果与测试结果一致,角变形约为1.6°,验证了将实际焊接工艺中15层27道简化为5层5道的焊道集中方案的准确性;平台结构的焊接变形表现为局部下塌或上凸的面外变形,是由上下坡口不对称产生的焊接角变形及底部钢架支撑作用共同产生的,面外变形范围为−5.2 ~ 4.4 mm. 相似文献
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以工程实例分析了燃机透平静叶环气封体在返修焊接过程中的主要焊接变形风险,采用分段对称施焊顺序并严格控制焊接热输入来减小结构的焊接变形;在施焊过程中采用12只百分表实时监测气封体圆周及天地方向的焊接变形量。返修结果表明,气封体的整体焊接变形得到了有效控制,变形量在设计允许的范围内,焊缝经无损检验质量符合相关要求。本次成功返修为后续高精度加工件的返修焊接变形控制提供了有效的预防与控制措施及新的精益返修思路。 相似文献
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通过分析不同焊接热输入下Q890D钢板的焊接接头金相组织及热影响区硬度,考察了不同焊接热输入对其焊接接头强度、-20℃低温冲击吸收能量的影响。结果表明,Q890D钢在热影响区存在明显淬硬现象。当焊接热输入由低向高变化时,热影响区的硬度有上升趋势,而表面焊道的热影响区硬度远远高于打底焊道,说明多层多道焊时,后道焊缝对前道焊缝的热处理效果比较明显,减少了热影响区的淬硬组织。打底焊道的热影响区硬度低于焊缝及母材,存在焊后软化现象,焊接时需尽量避免过大的焊接热输入。焊缝金属中粗大贝氏体组织的增加,导致焊缝金属低温冲击吸收能量普遍低于热影响区。随着热输入的减小,焊接接头的抗拉强度和冲击吸收能量(包括焊缝、熔合线及HAZ)都有很大的提升。说明焊接热输入在一定范围内的变化对整个焊接接头强度及塑韧性有较大的影响。 相似文献
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采用单元温度对单元进行生死控制的有限元计算方法研究了拘束条件对2.5 mm厚铝锂合金5A90薄壁T形接头双光束激光焊接变形的影响,拘束条件包括对筋板施加和对底板施加两类,约束在焊接过程中施加,焊后冷却到室温去除.筋板拘束条件施加在筋板顶部和侧面,对比了施加与不施加约束两种情况,该两种情况连续焊接之前都采用点固焊对筋板进行固定.底板拘束条件通过在T形接头两侧设置压块对底板施压来实现,研究了压块与焊缝不同距离对焊接变形的影响.最后进行了试验验证.焊接过程中对筋板施加约束有利于减小焊接过程中及焊后筋板变形.底板纵向约束影响T形接头焊件挠曲变形的大小和方向,对角变形影响不大.焊接过程中对底板施加y向约束,有利于减小角变形.对底板加纵向约束与不加纵向约束两种情况进行了试验验证,变形方向及变形量最大值的计算结果与试验结果符合. 相似文献
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基于ABAQUS有限元软件的热弹塑性分析方法,分析了32 mm厚Q345qD钢对焊接头在熔化极气体保护焊下的残余应力和残余变形。结合试验测试和数值模拟,研究了4种不同焊接顺序对焊接接头残余应力分布和残余变形的影响。采用ABAQUS软件中的单元生死技术模拟焊接过程,热源模型采用双椭球体积热源。结果表明,数值模拟结果与试验结果相符,改变焊接顺序对温度场影响不大,两侧焊道单次交替焊接相比两侧焊道多次交替焊接的横向残余应力整体应力较小,最大值从356 MPa降到278 MPa,降低了21.91%;而两侧焊道多次交替焊接的纵向残余应力整体应力较大,纵向残余应力最大值从303 MPa升到368 MPa,增加了21.45%。与两侧焊道单次交替焊接相比,两侧焊道多次交替焊接的厚度方向变形较小,最大值从1.67 mm降到0.04 mm,降低了97.60%。 相似文献
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Satoshi Yamane Katsumasa Uji Toru Nakajima Hikaru Yamamoto 《Welding International》2013,27(2):103-109
The formation of stable back beads in a root pass weld during one side multi-layer welding is important to achieve high quality welded metal joints in MAG welding. The authors employed the switch back welding method for V groove joints without backing plates. In this switch back welding method, the torch moves forward and backward with an oscillation frequency of 2.5 Hz. In order to achieve this welding, personal computers control the conventional welding robot, the power source characteristic and the wire feeder unit. During the forward, the torch is weaving on the V groove gap without the weld pool. If the weaving width becomes wider than the proper width, the tip of the wire becomes high and a good back bead cannot be obtained. The weaving width is adjusted so as to get the proper width in the switch back welding. The suitability of the welding conditions for each root gap was verified by observation of the arc, the weld pool and the external appearance of back beads. A good back bead was obtained under V groove welding in 2–4 mm gap. 相似文献
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针对转向架构架焊接变形及根部焊道背部成形问题,研究坡口角度为30°的V形窄坡口旁轴式等离子-MAG复合热源焊接工艺.文中以SMA490BW耐候钢平板对接为研究对象,基于响应面法建立了主要影响熔深的等离子电流、MAG电流、焊接速度、等离子气体流量与焊缝根部焊道的熔深、背部余高之间的数学关系模型,并依此模型分析了等离子-MAG复合焊接工艺参数对焊缝熔深能力的影响,获得了合适的复合焊接工艺参数.与普通MAG焊相比,窄坡口等离子-MAG复合焊接工艺既可保证焊缝根部完全熔透又能有效地减小接头的焊接变形. 相似文献
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《Science & Technology of Welding & Joining》2013,18(1):38-44
AbstractIn fusion welding, gravity makes a molten metal flow downward and it sometimes causes an irregular shaped weld bead and weld defects such as an undercut. To solve this problem, the authors propose a new electromagnetic controlled molten pool welding process method which controls the molten metal flow by using upward electromagnetic forces, and the applicability of this method to industry is examined. In flat position welding with excessive heat input, the molten metal tends to sag down and an undercut defect is likely to occur. It is found that the upward electromagnetic force given by adjusting the conditions of magnetic field can lift the molten metal up, resulting in the remarkably improved shape of a penetration bead. It is further found that, even in overhead position welding, a well shaped penetration bead without undercuts is obtained by adjusting the welding touch angle as well as magnetic field conditions. 相似文献
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A robot used for multi-pass welding of the piping branch junctions and nozzle attachments to main pressure vessels is 4-DOF serial mechanism,two mobile joints and two rotary joints are adopted in design.The kinematic model was established with DH parameters,the inverse kinematics was solved.According to the forward and inverse kinematics equations,the robot kinematics was simulated in Matlab,the simulations indicate that the solution for inverse kinematics can satisfy the welding requirements well.As there are size errors,processing errors and welding deformation,the path of welding is forecasted according to the previous welding situation,and then,the path is taught at desired via-points,which plays an important role in submerged-arc welding.The submerged-arc welding experiments indicate that the robot and the welding methods are preferable to ensure welding quality. 相似文献
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在西气东输二线东段施工中,统计分析了1 700道φ1 219 mm×18.4 mm管道全位置自动焊焊接缺陷,发现环焊缝仰焊位置是产生超标缺陷最多的区域,而细长的未熔合是超标缺陷的主要形式。加强焊接过程控制是克服和提高管道自动焊合格率的重要措施。 相似文献