A simplified FE simulation method with shell element for welding deformation and residual stress generated by multi-pass butt welding

In order to propose a simplified simulation method using finite element (FE) model for predicting deformation and residual stress generated by multi-pass butt welding, a series of experiments and numerical analyses were carried out. 3-pass butt welding of steel plates was simulated by the thermal elasto-plastic analysis with shell elements and with solid elements respectively. A heat input model for considering the temperature distribution in the thickness direction in shell elements was proposed. The validity of the heat input model was verified by comparing analytical results with experimental results or other analytical results using solid elements. Furthermore, the effectiveness for saving computing time by using shell elements was confirmed from the comparison with the case using solid elements. It was confirmed that the welding out-of-plane deformation and residual stress could be predicted with high accuracy by the proposed method. The computing time was around 14% of that by the precise model with solid elements.     

焊接加固热作用对工形截面压弯钢构件承载性能的影响

为研究焊接加固热作用及不同初始负载对工字形压弯钢柱承载性能的影响,基于考虑热影响的热结构耦合分析方法进行了热源模型热输入改进,并考虑初始几何缺陷、初始残余应力及摩擦等,完成了不同负载下焊接加固的3个工字形压弯钢柱的模拟分析。研究了焊接位移时程、腹板应力应变重分布及荷载位移关系,通过有限元分析与相应试验结果对比验证,进而获得了试验无法获得的焊接温度场、翼缘与加固板间的焊接应力应变重分布以及翼缘边缘屈服承载力等结果,并将承载力结果与规范计算结果对比,考察了现有设计方法。结果表明,焊接顺序决定焊接变形的发展过程,焊接热输入和初始负载共同决定持载焊接的位移变化范围和焊接残余变形的大小;初始负载越大,应力应变重分布往偏心受力方向发展更多,承载力越低,而初始残余应力不影响极限承载力;采用考虑热影响的有限元方法具有一定可行性和总体安全性,规范设计方法仍有可提升空间。     

Introducing/reproducing of welding distortion and residual stress in analysis for elastic-plastic behaviors of steel plates under compressive loads

A series of analyses was carried out to elucidate treatment of welding imperfection for simulating elastic-plastic behaviors of steel plates under compressive loads. A thermal elastic-plastic analysis based on infinitesimal deformation theory was carried out on a single-pass butt-welding of thin steel plates to predict welding distortion and welding residual stress. The obtained welding distortion and welding residual stress were introduced into an elastic-plastic large deformation analysis as initial imperfection. However, it was elucidated that welding distortion and welding residual stress could not be reproduced precisely due to unbalanced force caused by the difference between both analysis theories. Therefore, it should be confirmed whether the introduced welding distortion and welding residual stress were reproduced with high accuracy. Consequently, if welding distortion and welding residual stress cannot be reproduced, the treatment such as the convergence calculation method applied in this study should be done for precise elucidation of the elastic-plastic behavior of plates under compressive loads.     

On the prediction of effect of direction of welding on bead geometry and residual deformation of double-sided fillet welds

The present study describes how the effect of direction of welding is useful to minimize distortion in submerged arc welded double-sided fillet joints. In present work, angular distortion of 12 mm thick double-sided fillet welds was measured for same direction and reverse direction welding. It has been observed that the maximum magnitude of the angular distortion for reverse direction fillet welding is lower. Thermal history in horizontal and vertical plate of fillet welds was also measured for both same direction and reverse direction welding. After welding, the fillet welds were sectioned, polished and etched to measure the effect of direction of welding on weld bead geometry. To predict the temperature distribution and thermal history, a finite element (FE) elasto-plastic thermo-mechanical model has been developed for submerged arc welded double-sided fillet welds by using moving distributed heat source. The three-dimensional FE thermal model was verified by comparing peak temperature obtained with experimental values. The model results matched fairly well with experimental results with a variation of 6 percent for sample 1 and 7.5 percent for sample 2 for the maximum values of distortion, and a variation of 2-8 percent for peak temperatures in horizontal plate and 9 percent in web plate.     

A review on assessment of fatigue strength in welded studs

Welding is one of the most important and highly developed joining methods; nevertheless unwanted side effects occur like thermal strains and altering of certain material properties induced by heating and melting. These effects lead to distortions and high residual stresses which should be kept to a minimum. To minimize distortion, various strategies are being developed. Stud welding is widely used in steel structures, power plants, and ship buildings due to the significantly technology including highest quality of production processes by continuous electrical control and the efficiency of such a process. Therefore, varying the heat input typically will affect the material properties including yield strength, tensile strength, hardness, and notch toughness in the stud arc welding. Well-defined heat sources offer a reproduced heat input into a highly localized area. The fatigue strength of stud welding has been investigated by performing welding process and microstructural observations. This paper is going to discuss the influence of heat input on the structural changes in stud arc welding.     

负载下焊接加固钢结构压弯构件受力性能的影响因素分析

为研究负载下焊接加固钢结构压弯构件的受力性能,采用考虑焊接热影响的有限元分析方法,对不同初始负载、偏心距、长细比及焊接热输入等级等影响因素进行分析。完成了包括未加固压弯钢柱及加固压弯钢柱共72个构件的受力全过程模拟分析,获得了各因素影响规律,并验证了考虑二阶效应的新的名义应力比计算公式。结果表明:未加固构件的初始负载水平可通过二阶式反映;初始几何缺陷模式及大小影响失稳破坏方向及焊接残余变形大小;影响加固构件极限承载力的主要因素依次为偏心距、长细比、焊接热输入、初始应力比;影响焊接残余变形的主要因素依次为焊接热输入、初始应力比、长细比;为新编《钢结构加固设计规范》关于负载下焊接加固压弯构件设计计算方法提供了参考和依据。     

基于盲孔法的高强焊接圆钢管表面残余应力试验研究

为研究高强焊接圆钢管残余应力分布模式,基于盲孔法对21个高强焊接圆钢管的5个外表面、1个端部内表面纵向残余应力分布进行测量;对盲孔法应变释放系数A、B进行平面试验及平面有限元标定,验证有限元标定的可靠性;进行柱面有限元标定并依据形状改变比能修正法对试验测量结果进行塑性修正,提出埋弧焊接、高频焊接圆钢管外表面纵向残余应力分布模型。研究结果表明：柱面有限元模型可弥补应变计弧面形状造成的误差,与平面试验标定结果相比,对于截面规格为φ325×8的埋弧焊接圆钢管标定系数A误差可达6.1%,对于截面规格为φ356×10的埋弧焊接圆钢管,标定系数B误差可达5.0%;与平面有限元模型标定结果相比,由柱面标定得到的应变释放系数A随直径增大而减小、系数B随直径增大而增大,并逐步趋近于平面标定结果。沿着焊接方向1/4、1/2、3/4柱高截面最大纵向残余应力数值相近,最大残余拉、压应力分别为0.96fy、-0.27fy。高频焊接圆钢管端部内表面与外表面残余应力分布模式不同,外表面以残余拉应力为主且最大为0.46fy,内表面以残余压应力为主且最大为-0.37fy。提出的纵向残余应力分布模型与实测数据吻合较好。     

组合热源电弧焊残余应力数值模拟

用大型有限元分析软件ANSYS,对钢材平板坡口电弧焊的温度场和应力场进行数值模拟。有限元模型选用三维实体单元,考虑材料物理性能随温度变化和对流边界等。采取表面高斯热源与焊缝区体热源相结合的组合热原模型模拟电弧焊的焊接热源。获得了三维电弧焊的焊接温度场和残余应力场,并对计算结果进行了分析,为准确求解焊缝强度、变形及指导钢结构施工设计和合理利用残余应力奠定了理论基础,提供了一种新的思路。     

Experimental research on surface residual stress of high strength welded circular steel tube based on hole-drilling strain-gage method

为研究高强焊接圆钢管残余应力分布模式，基于盲孔法对21个高强焊接圆钢管的5个外表面、1个端部内表面纵向残余应力分布进行测量；对盲孔法应变释放系数A、B进行平面试验及平面有限元标定，验证有限元标定的可靠性；进行柱面有限元标定并依据形状改变比能修正法对试验测量结果进行塑性修正，提出埋弧焊接、高频焊接圆钢管外表面纵向残余应力分布模型。研究结果表明：柱面有限元模型可弥补应变计弧面形状造成的误差，与平面试验标定结果相比，对于截面规格为φ325×8的埋弧焊接圆钢管标定系数A误差可达6.1%，对于截面规格为φ356×10的埋弧焊接圆钢管，标定系数B误差可达5.0%；与平面有限元模型标定结果相比，由柱面标定得到的应变释放系数A随直径增大而减小、系数B随直径增大而增大，并逐步趋近于平面标定结果。沿着焊接方向1/4、1/2、3/4柱高截面最大纵向残余应力数值相近，最大残余拉、压应力分别为0.96fy、-0.27fy。高频焊接圆钢管端部内表面与外表面残余应力分布模式不同，外表面以残余拉应力为主且最大为0.46fy，内表面以残余压应力为主且最大为-0.37fy。提出的纵向残余应力分布模型与实测数据吻合较好。     

平板对接焊的温度场和应力场有限元分析

针对中厚板在焊接过程中存在残余应力和变形,运用ANSYS热-结构的耦合分析功能,对焊接温度场和应力场进行了模拟计算。结果表明,焊缝区及附近存在较大的焊接残余拉应力,应力最大值接近或超过材料的屈服强度,离开焊缝区后焊接残余应力迅速衰减为压应力。     

Effects of welding residual stress on compressive behavior and ultimate strength of corroded plate

This study examined the effects of welding residual stress on the compressive behavior and the ultimate strength of the corroded plate. First, welding residual stress was obtained by the thermal elastic-plastic analysis. Then, the change of welding residual stress and the deflection due to the volume loss was investigated by using a newly developed program based on FEM. Finally, the effects of welding residual stress on the compressive behavior and the ultimate strength of the corroded plate were investigated by the elastic-plastic large deformation analysis. As results, the beginning point of the reduction of the initial stiffness with welding residual stress was earlier than that without welding residual stress. Such effect was observed significantly in the case that the volume was lost in the region which has compressive residual stress. Furthermore, the ultimate strength of the corroded plate was reduced by welding residual stress regardless of the plate length, the corroded regions and the reduction of the thickness. The effect of welding residual stress on the ultimate strength became small with the decrease of the thickness.     

焊接残余应力对网架负荷加固的影响分析

负荷条件下对网架结构进行加固时,焊接残余应力对网架结构的内力、变形有较大影响。本文结合某网架负荷加固工程,通过运用ANSYS有限元软件对焊接杆件施加等效温度荷载的方式,模拟网架负荷加固杆件焊接时的热胀冷缩。通过相应的应力、变形分析,得出焊接残余应力对网架结构负荷加固的影响。     

焊接工艺中的残余应力

介绍了建筑钢结构焊接残余应力的特点，分析了残余应力产生的原因，并从自然时效、热时效、振动时效几方面阐述了残余应力的消除方法，简单介绍了振动时效法在热风炉中的应用，最后论述了残余应力测量方法，以保证钢结构的结构安全性。     

热应力法在钢结构焊接疲劳模拟中的应用

基于ANSYS平台,给出了间接热应力法计算焊接残余应力的计算流程。以V型坡口钢板为例,利用APDL语言编程,获得了焊接温度场及残余应力场的分布规律,计算结果与实测结果比较吻合。对于进一步研究焊接疲劳具有指导意义。     

Experimental and FE analysis of submerged arc weld induced residual stress and angular deformation of single and double sided fillet welded joint

Submerged arc welding is well-known for its very high deposition rate and thus the capability to join very high thickness metal pieces in large structural applications. Fillet joints are mostly used in structural applications which can be extensively seen in shipbuilding, bridge construction, house buildings, automobile or any other large structures. Thermal stresses generates in a fusion welded joint due to high temperature gradient, which is the cause of the residual stresses upon cooling followed by the angular deformation and failure of the welded structure. As an effect of the thermal gradient, the induced longitudinal, transverse residual stress & angular distortion can vary in single sided and double sided submerged arc welded fillet joints, during designing & manufacturing welded structures which should be taken into account. The main objective of this paper is to quantify the amount of residual stresses and angular deformation in a fillet welding joint. An elasto-plastic thermomechanical model has been developed for predicting residual stresses. A comparison of the residual stress and angular deformation between single and double sided fillet weld joint has been made. The simulation results reveal that the amount of residual stress present in the single sided fillet weld is more and unbalanced in both side of the center of weld line compared to the double sided fillet weld and the predicted results have been matched with the experiments as well as published literatures.     

HRBF400钢筋手工电弧焊焊接接头组织性能分析

手工电弧焊因为其稳定的性能特点而被广泛用于各种焊材的焊接。通过分析手工电弧焊中不同焊接方法焊接接头的切口形貌、显微组织与硬度分布着重讨论了不同的焊接方法对热轧带肋钢筋组织性能的影响,为进一步优化其性能与工艺提供了理论依据。实验结果表明:由于焊接方法的差别及焊接过程中热输入不同,使得焊接接头的宏观形貌各不相同,具体表现在焊缝的深宽比、热影响区的大小及焊接缺陷等。接头的微观组织主要以先共析铁素体,低碳马氏体、回火索氏体、细晶铁素体和珠光体组成。不同的焊接方法,焊接接头的轴线方向及横截面的维氏硬度值也是各不相同,这就导致了其性能的差异。     

赞比亚硫酸贮罐底板焊接变形的控制技术

硫酸贮罐底板直径大、焊缝多、焊接量大,在焊接过程中将不可避免地产生焊接应力和焊接变形。焊接残余应力和变形的存在,会对焊接底板的承载能力和外形尺寸产生不同程度的影响。采用焊接变形控制技术后,可减少底板焊后的变形,释放焊接残余应力,改善焊接质量。自投产以来,至今运行状态良好,实践证明:这种技术方案能满足施工技术要求。     

Comparison of residual stress in relaxed and non-relaxed weldments of steel plates

In this study, two methods, X-ray diffraction (nondestructive) and hole-drilling (destructive) are applied to measure the residual stress of gas metal arc welded steel plate. Both non-relaxed and relaxed (local heating, furnace annealing and bead blasting) weldments are examined to understand the residual stress distributions before and after elimination of residual stresses. Results show that the heat affected zone of gas metal arc welding method is about 10 mm from the weld centerline. The local heating method is very effective in reducing the residual stress caused by the cold work of the original steel plate. The furnace annealing method reduces the residual stress to compressive but not uniformly distributed. The detrimental fluctuation of residual stress is successfully reduced and uniformly relaxed to be beneficially compressive in the bead blasting. Most importantly, X-ray diffraction shows more precise and better handling than hole-drilling method in terms of data error.     

Experimental study on residual stresses in welded monosymmetric I-section

为了研究单轴对称焊接工字形截面残余应力分布规律,采用盲孔法对15个单轴对称工字形截面试件进行了试验研究,得到了不同试件全截面纵向残余应力分布,研究了腹板高厚比、翼缘宽厚比、翼缘宽度、施焊顺序等对残余应力的影响。试验结果表明：残余压应力数值与截面尺寸直接相关,残余拉应力数值受截面尺寸影响较小;腹板中靠近宽翼缘一侧的残余压应力峰值大于靠近窄翼缘一侧的压应力峰值;翼缘宽度增大时,分布于所在翼缘和腹板的残余压应力减小;施焊顺序对翼缘上的残余应力及腹板上的残余拉应力峰值有一定影响,而腹板上的残余压应力没有明显变化。基于试验结果,提出了适用于单轴对称焊接工字形截面的残余应力分布模型,该模型能够较准确反映各种因素的影响。     

焊接残余应力的产生及其消除方法

在分析残余应力产生原理的基础上,介绍了焊接残余应力的概念,并探讨了焊接残余应力产生的原因及其影响因素,提出了消除焊接残余应力的方法,指出研究和测量构件中残余应力对生产和科学试验具有重要意义。