振动时效在铝合金厚板应力消减中的局限与应用

运用振动时效对材料应力消减的作用,结合铝合金厚板残余应力消减后的分布及效果,认为振动时效对厚板结构残余应力消减作用有限。而运用位错理论和最小能量法分析,发现振动时效对材料因内部微结构差异而形成应力集中区域的应力松弛释放有所贡献,在一定激振频率和时效时间条件下,完全可以造成材料局部的微屈服,减小了微结构间残余应力水平,从而对板内应力的均匀化过程起到一定效果。借助实验对厚板振动时效前后表面应力强度和板形尺寸稳定性对比发现,振动时效对稳定板形和消减大梯度表面残余应力具有显著作用。     

振动CO2气体保护焊缝残余应力和接头显微组织分析

采用振动CO2气体保护焊对轻型汽车驱动桥壳进行了焊接。对被焊接工件在常规CO2气体保护焊、常规CO2气体保护焊后振动时效处理及不同激振频率下振动CO2气体保护焊三种工艺进行了对比,并就不同条件下的焊缝残余应力、焊接接头显微组织作了分析。结果表明,采用适当振动参数, 在较大振幅时,振动CO2气保焊接能有效减小焊接变形,降低焊接残余应力,最大主动应力降低幅度达到41.74%。熔合区和过度区变窄,焊缝和热影响区晶粒明显细化,由柱状晶转变为等轴晶,魏氏组织减少甚至消失。     

振动时效消除拼焊不锈钢板的残余应力

为了消除超大不锈钢焊接底板的残余应力,研究了采用振动时效(VSR)的方法消除焊接残余应力。应用JB /T5926-91标准对振动时效工艺进行了定性的评价。通过对焊后和振动时效后底板焊缝上残余应力的对比测量,全面地、定量地了解振动时效工艺对残余应力的变化及最终的应力状况的影响,了解了VSR工艺的可行性和有效性,从而实现替代热时效工艺目标。     

用X射线衍射法测定振动时效后水电站钢岔管中的残余应力

介绍了采用振动时效技术消减水电站钢岔管焊接残余应力,以及用X射线衍射法进行焊接残余应力测试来对振动时效效果进行定量评价。并举例说明X射线衍射测试焊接残余应力的应用情况。     

大桥箱型梁振动时效工艺与效果评定

针对大桥箱型梁拼焊过程中产生的焊接变形,通过应用振动时效(VSR)工艺,以消除拼焊处残余应力,提高箱型梁的尺寸精度.通过振动过程中动应力分析和VSR工艺前后残余应力的测量,了解箱型梁拼焊处动应力和残余应力的分布状况,实验结果表明VSR工艺消应力效果良好.     

高强度铝合金厚板振动时效工艺的研究

高强度铝合金中存在的残余应力引起工件变形与尺寸不稳定,是长期困扰工程界的技术难题。振动时效是一种能有效地降低残余应力和提高尺寸稳定性的技术,其中,振动时效工艺的掌握至关重要。介绍了振动时效工艺的基本原则,再用悬吊简化的振动台的方法对高强度铝合金厚板进行振动时效,展示了其具体的振动时效的工艺过程,达到了理想的时效效果。铝合金厚板的振动时效工艺直接影响着时效效果。     

支铰钢梁的振动时效与残余应力分析

为消除刘家道口弧形闸门支铰钢梁焊接后的残余应力,通过有限元分析,确定了采用振动时效工艺,并对振动时效的效果进行了分析。结果表明：振动时效方案可有效消除钢梁的残余应力,为同类工程消除残余应力提供了范例和经验。     

热时效对消除钢结构焊接残余应力的工艺评估

针对钢结构拼焊过程中产生的焊接变形和残余应力,采用热时效工艺对焊接构件进行了消应力处理,然后采用盲孔法对焊接构件焊后和热时效后的残余应力分布及变化进行了测定,定量地评估了热时效消除钢结构焊接残余应力的工艺效果。结果表明：通过热时效处理,可使钢结构的焊接残余应力大大降低,消除应力效果良好。     

振动时效法在薄壁铸件上的应用

介绍了振动时效法消除残余应力的机理以及在薄壁铸件上的应用。通过对振动时效工艺参数,包括激振点、支撑点、激振频率、激振力和激振时间等的分析,优化出了薄壁铸件的振动时效工艺。振动时效后薄壁铸件残余应力降低35%以上,应力分布得到了均化,同时与热时效相比,节约工艺成本70%以上,大大地缩短了处理时间。     

振动时效技术在石油钻机大型焊接件上的应用

振动时效技术,简称“VSR”技术,它是利用亚共振原理消除和均化金属构件内部残余应力,防止构件产生焊接裂纹的一种新技术,可取代传统的热时效和自然时效工艺。它具有高效节能,低碳环保,节资省时,使用方便等特点,在目前能源日趋紧张、价格不断上涨时期显得尤为突出和重要^[1]。本文对石油钻机大型焊接件的振动时效工艺参数进行了研究。     

On the correction of plasticity effect at the hole edge when using the centre hole method for measuring high welding residual stress

Significant error caused by plasticity at the hole edge may arise when measuring sufficiently high welding residual stress by means of the hole drilling method. According to elastoplastic theory, a critical parameter of plastic deformation round the centre hole is obtained. On the basis of this critical parameter, a simple method is proposed to correct the stresses for the plasticity effect. It is shown in the experiments with welded joints that the correction method may improve the accuracy of high residual stress measurement.     

含焊接残余应力的结构模型参数修正研究

提出考虑焊接残余应力的结构模型参数修正方法。在预应力分布模型基础上建立含焊接残余应力的结构刚度矩阵方程,分析了焊接残余应力对结构刚度及结构振动特性的影响;以消除焊接残余应力对数值计算规模和计算精度的影响为目标。应用结构优化算法,以结构固有频率残差最小化为目标,开展有限元模型的结构参数修正研究;最后,以圆柱壳结构为例,实施基于结构模型参数修正的优化计算,验证方法的可行性。     

铝合金加筋壁板搅拌摩擦焊接残余应力及变形分析

目的对民机用铝合金加筋壁板搅拌摩擦焊接残余应力及变形进行研究。方法采用热-力耦合数值模拟方法,分析民机用铝合金加筋壁板搅拌摩擦焊接过程,分别模拟了采用3种焊接顺序进行蒙皮-长桁焊接时,壁板温度场分布规律及焊后残余应力及变形情况。结果铝合金壁板搅拌摩擦焊接后,沿焊缝方向残余应力为拉应力,由此导致长桁及与其连接的蒙皮产生向上的挠曲变形,垂直焊缝方向,焊缝两侧的壁板向上翘曲。结论对于3种焊接顺序,采用"先两侧、后中心"由外向里的焊接顺序,得到的壁板残余变形最小。     

高性能铜合金板带残余应力测量中的转动结构的应用和分析

利用转动结构对面内位移高度灵敏的特性提出了高性能铜合金板带残余应力测量的新方法,对转动结构作了有限元分析和结构优化。设计了实验装置模拟残余应力释放对转动结构变形的影响。实验与有限元分析结果取得良好一致。本研究表明转动结构具有较高的测量灵敏度和良好的线性,试样制作及数据测量方便,为高性能铜合金板带残余应力测量提供了一种新的检测手段。     

焊接参数对TC4薄板焊接过程的影响

目的 揭示焊接参数对TC4薄板焊接过程中温度场、位移场及应力场的影响规律。方法 基于有限元（FEM）模拟方法,运用Fortran语言对焊接热源及焊接参数进行定义,以模拟不同焊接参数下TC4薄板的TIG对接焊过程。结果 在稳弧阶段,温度场为一组以焊接方向为长轴的椭圆,且存在温度梯度,随着焊接速度的增大,温度场峰值、温度场温度梯度、熔池宽度和熔池体积逐渐减小,而焊接效率和焊接电流对温度场的影响与焊接速度刚好相反;随着焊接速度的增大,薄板最大变形量逐渐减小,焊接角变形及挠度变形逐渐得到改善,而焊接效率和焊接电流对位移场的影响与焊接速度刚好相反。在稳弧阶段,焊缝位置的残余应力为拉应力,两侧为压应力,随着焊接速度和焊接电流的增大,纵向残余拉应力逐渐增大,焊缝处高应力集中区的宽度逐渐减小,而焊接效率对应力场的影响与焊接速度刚好相反。在高焊接速度、中等焊接效率、低焊接电流参数条件下,可获得熔池体积小及熔池宽度窄的焊缝,有利于减小焊后残余应力与变形。结论 上述研究结果可为TC4薄板的焊接过程提供一定的理论指导。     

大型结构件焊接变形特征分析

从焊接残余应力产生机理入手,找出焊接变形的影响因素,通过数值分析推导焊接变形过程中残余应力产生的数学模型,用有限元模拟和试验方法检验模型并找出最优焊接方法．     

Effect of water-shower cooling during welding on tensile residual stress improvement in multi-layer welding of austenitic stainless steel plates

Abstract

A new welding method that uses a water shower behind the welding torch has been developed in order to reduce tensile residual stress in a welded region. When this method is applied to the welding of austenitic stainless steel, the welding and cooling conditions mainly determine how much the residual stress can be reduced. To optimize these conditions, we first used the robust design technique to determine the effects of the interpass temperature, the heat input quantity and the water-shower area on the residual stress distribution of bead-on-plate. We found that, to decrease the tensile residual stress, the interpass temperature should be high, the heat input low, and the water-shower area large. Effect of the water-shower cooling on multi-layer welding was examined analytically and experimentally. It was found that the residual stresses were tensile without water-shower cooling, but compressive with water-shower cooling under the optimized conditions. It can therefore be concluded that the new welding method is appropriate for reducing tensile residual stress in multi-layer welding of austenitic stainless steel.     

A study of the residual stress and deformation in the welding between half-pipe jacket and shell

Half-pipe jacketed vessels are widely used as the heating or cooling structure in the chemical industries. But the leakage of the welding joint between the jacket and cylinder is a big problem, which is greatly affected by the residual stress and deformation. This paper presents a finite element analysis of residual stress and deformation induced by welding half-pipe jacket to shell, and the effects of heat input, cooling inside the shell and welding sequence on residual stress have been discussed. It is found that large longitudinal stress is generated in the weld metal. Due to the local weld heating, the jacket and shell become un-circle. A wave shape of stress along the circumferential of shell is generated. With the heat input increase, the residual stress and ellipticity increase linearly. On the premise of entire penetration welding, smaller heat input should be used to avoid too big deformation. Filling the shell with cooling water can decrease the residual stress and ellipticity during the welding, and welding the two joints of one jacket simultaneously is also available, which provides a reference for the welding of half-pipe jacket.     

Influences of heat source model on welding residual stress and distortion in a multi-pass J-groove joint

Welding mechanical behaviors including residual stress and distortion are highly non-linear phenomena in nature. When numerical simulation methods such as thermal elastic plastic finite element method (FEM) are used to quantitatively predict welding residual stress and distortion, a long computational time is required especially for multi-pass joints. In real engineering structures, many weldments have large dimensions and complex shapes, and they are usually assembled by a multi-pass welding process. Therefore, it is necessary to develop time-effective computational approaches for practice engineering analysis. In this study, a method based on variable length heat sources was proposed for the analysis of thermo-mechanical behaviors for multi-pass joints. The welding residual stress field in a dissimilar metal J-groove joint with axis-symmetric geometrical shape, which was performed by a semi-circle balanced welding process, was investigated using the proposed method. The simulation results were compared with the measured data as well as the simulation results computed by a moving heat source. Meanwhile, the instantaneous line heat source was also employed to estimate the welding residual stresses in the same joint in an extreme case. The influences of heat source model (type) on welding residual stress and distortion were discussed.     

多角度交替缠绕复合圆筒的剩余应力算法及水压试验

针对含薄壁钢内衬碳纤维增强聚合物基复合材料（CFRP）多角度交替缠绕复合圆筒的剩余应力计算问题,基于正交各向异性材料的厚壁圆筒理论和弹性叠加理论,提出了考虑卸去芯模影响的多角度交替缠绕下CFRP各层和钢内衬剩余应力的逐层叠加算法,研究了恒缠绕张力下,芯模厚度和螺旋层缠绕角对CFRP各层和钢内衬剩余应力的影响。计算表明：芯模厚度越大则CFRP层剩余应力越低,但芯模厚度过大将减弱缠绕张力对钢内衬的强化效应;螺旋层缠绕角约65°时,环向层剩余应力出现极小值,螺旋层剩余应力和内衬剩余应力均出现极大值。针对缠绕张力对钢内衬的强化效应,通过水压试验加载过程中钢内衬声发射特征与复合圆筒外壁应变测试,测得的钢内衬屈服载荷与理论预测值一致,基本证实了算法的有效性。为提高CFRP层缠绕质量,基于等剩余应力假设,提出了多角度交替缠绕张力制度优化设计思路,适用于内压管的张力制度优化。