Numerical calculation of residual stress development of multi-pass gas metal arc welding

In various applications, welding-induced residual stresses have a substantial impact on the integrity of welded constructions. Tensile residual stress can promote stress-corrosion cracking, brittle fracture, and reduces the fatigue life in service, as well as influences component design due to critical stress concentrations within the component.In the present paper, a six bead multi-pass gas metal arc weld of 20 mm thick structural steel S355J2+N is experimentally and numerically investigated. The studies include transient 2D and 3D numerical calculations which consider temperature-dependent material properties, phase transformations, “thermal” tempering, transformation plasticity, volume change due to phase transformation, an elastic–plastic material model, and isotropic strain hardening. The experimentally determined and calculated residual stresses are in a good agreement. Furthermore, the influence of the preheat and interpass temperature on welding-induced residual stresses is shown in the present investigation.     

Optimization of Laminated Ceramic Composites for Minimum Residual Stress and Cost

Abstract: Optimal design of laminated ceramic components is of interest in various structural applications. Residual stresses are induced in laminated ceramic composites when they are cooled from elevated processing temperatures. These stresses can be minimized by tailoring the material compositions and thicknesses of the composite layers. While this is an effective method, the material cost of the composite increases with a decrease in the residual stress. A multiobjective optimization problem is formulated to consider both residual stress and cost. The constraint method and the min-max approaches are used to solve this problem. It is shown that the min-max solution yields the best compromise solution. The formulation considers wear resistance, fracture toughness, and delamination in the laminate.     

厚壁矩形中空截面冷弯型钢纵向残余应力试验研究

对壁厚超过6mm的厚壁矩形中空截面冷弯型钢进行试验研究。矩形中空截面采用两种成型方法:直接法(直接形成矩形)和间接法(先形成圆形,再转换成矩形)。采用两种方法(钻孔法和X射线衍射法)计算纵向残余应力的大小和分布。研究了沿截面周长方向和厚度方向的纵向残余应力的大小和分布。结果显示,沿厚度方向的纵向残余应力在外表面为拉力,内表面为压力,表现出类似于正弦曲线的非线性特性。此外,讨论了厚壁矩形中空截面冷弯型钢的成型过程和截面几何尺寸对残余应力的大小和分布的影响。最后,针对厚壁矩形中空截面冷弯型钢两种不同成型过程,分别给出相应的残余应力分布情况。     

Experimental investigation on longitudinal residual stresses for cold-formed thick-walled square hollow sections

This paper presents the experimental study on cold-formed thick-walled square hollow sections with thickness greater than 6 mm. Square hollow sections are formed using two different forming processes of a “direct square” way and an “indirect way from circular to square”. Two test methods of the hole-drilling method and the X-ray diffraction method are used to measure the magnitudes and distributions of longitudinal residual stresses. The magnitudes and distributions of longitudinal residual stresses along the section perimeter as well as along the section thickness are obtained in this study. It is shown that the longitudinal residual stresses are in tension at outer surface and in compression at inner surface, and present nonlinear distributions, which seems like “sine” curve along the section thickness. Furthermore, the effects of forming process and cross-section geometry on the magnitudes and distributions of longitudinal residual stresses for cold-formed thick-walled square hollow sections are discussed. At last, two distribution patterns have been proposed for the square hollow sections formed using two different forming processes, respectively.     

A study on the effect of weld groove designs on residual stresses in SS 304LN thick multipass pipe welds

Present research describes the effect of weld groove designs on residual stresses of thick SS 304LN pipe welds which are commonly utilized for applications such as boiling water reactor system, oil and steam piping. The faying surfaces of the pipe joints were machined to generate conventional and narrow groove geometries for welding. Circumferential multipass pipe welding was carried out without applying preheat and post weld heat treatment. Blind hole drilling technique was employed for measuring hoop and axial residual stresses in narrow and conventional grooved SS 304LN pipe welds considering plasticity and stress concentration effects of hole drilling process. The result exhibited 20 to 30 percent reduction in residual stresses in narrow grooved pipe welds. A finite element model was developed for estimating the pass by pass peak temperature distributions in the pipe welds. Sequentially coupled thermomechanical elastic-plastic analysis of both conventional and narrow groove pipe welds indicated close agreement between the predicted and experimentally determined hoop and axial residual stresses.     

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.     

Axially compressed cylindrical shells with local settlement

The design of cylindrical metal silos and tanks is often controlled by considerations of buckling under axial compression. Whilst the effects of geometric imperfections on the buckling strength have been extensively explored, few studies have explored the effects of defects in the boundary conditions and the effects of residual stresses have received even less attention.This paper investigates the initiation and development of imperfections caused by local differential settlement at the supported base and their effect on the elastic buckling of a thin cylindrical shell under axial compression. The shells were treated as initially perfect with perfect support, but developing geometric imperfections and residual stresses as a consequence of local displacement at the supported edge and with residual stresses consistent with the induced geometric imperfections.The results raise interesting questions concerning the criteria of failure and appropriate tolerance measurements for constructed cylindrical shells.     

Nonlinear vibration of initially stressed functionally graded plates

In this paper, nonlinear partial differential equations for the vibration motion of an initially stressed functionally graded plate (FGP) are derived. The formulations are based on the classical plate theory and derived for the nonlinear vibration motion of an FGP in a general state of arbitrary initial stresses. The material properties of the FGP are assumed to vary continuously from one surface to another, according to a simple power law distribution in terms of the constituent volume fractions. The motion of functionally graded ceramic/metal plate is obtained by employing the Galerkin method and then solved by Runge–Kutta method. The initial stress is taken to be a combination of pure bending stress plus an extensional stress in the plane of the ceramic/metal plate. It is found that the frequency responses of nonlinear vibration are sensitive of the state of initial stress, the amplitude of vibration and the volume fraction of FGP.     

厚壁冷弯方矩管和热轧H型钢轴压极限承载力的对比研究

运用ANSYS有限元软件,在综合考虑初始几何缺陷、残余应力、冷弯效应等因素的基础上,分析了厚壁冷弯方、矩钢管和热轧H型钢轴心压杆的极限承载力,并将它们的极限承载力计算结果进行对比,得出相关结论,为轻钢结构框架柱构件截面选型提供了参考.     

Analysis of an orthotropic cylindrical shell having a transversely isotropic core subjected to axisymmetric load

A long two-layered circular cylinder having a thin orthotropic outer shell and a thick transversely isotropic core subjected to an axisymmetric radialv line load has been analysed. For analysis of the outer shell the classical thin shell theory was adopted and for analysis of the inner core the elasticity theory was used. The continuity of stresses and deformations at the interface has been satisfied by assumming perfect adhesion between the layers. Numerical results have been presented for two different ratios of outer shell thickness to inner radius and for three different ratios of modulus of elasticity in the radial direction of outer shell to inner core. The results have been compared with the elasticity solution of the same problem to bring out the reliability of this hybrid method.     

考虑初始缺陷的冷弯矩型管轴压极限承载力研究

运用ANSYS通用有限元软件包,综合考虑初始几何缺陷、残余应力、冷弯效应等因素,分析了壁厚大于6mm的冷弯矩型管轴心压杆的极限承载力,得出其稳定系数,并与《钢结构设计规范》、《冷弯薄壁型钢结构技术规程》的计算结果进行对比,提出了冷弯中厚壁矩型管轴心压杆稳定系数的初步确定方法。     

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。     

金属拱型波纹屋顶中的残余应力测试及影响

金属拱型波纹屋顶是一种新型的大跨度拱型薄壳结构,在我国得到了越来越广泛的应用,并已逐步被人们所接受．但有关这种结构型式的理论与试验研究还不多,更没有实用的设计规范．作者以W666金属拱型波纹屋顶为研究对象,采用钻孔法测试了其残余应力,分析了测试结果,得到一些初步结论,并总结了残余应力对金属拱型波纹屋顶结构性能的影响．     

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.     

Residual stress influence on material properties and column behaviour of stainless steel SHS

The paper describes the influence of forming-induced residual stresses in stainless steel SHS (Square Hollow Sections) on both the material itself and the behaviour of compressed members. The residual stress contribution to the stress–strain diagram concerning the initial modulus of elasticity and non-linearity is shown by the comparison of as-delivered and stress-relieved material. An analytical model covering the influence of residual stresses on material behaviour was developed and verified numerically. The FE study using the Abaqus software determines the influence of residual stresses in compressed members both on local and global buckling. Finally, the study on behaviour of member includes the influence of a varying degree of material non-linearity as an independent parameter representing the behaviour of various steels in long and stub columns with residual stresses.     

Experimental and numerical investigations on residual stresses in a multi-pass butt-welded high strength SM570-TMCP steel plate

During fusion welding process, complex thermal stresses are inevitably generated. The presence of residual stresses can be detrimental to the integrity and the service behavior of the welded part. In this study, both an experiment and a finite element (FE) method were utilized to investigate residual stress distribution in high strength SM570-TMCP (thermo-mechanical controlled process) steel weldment, which was constructed using a multi-pass butt welding process. Firstly, experiments which included a tensile test at elevated temperatures, an observation of the microstructures and a residual stress measurement were carried out to examine characteristics of residual stresses in the weldment. Secondly, a three-dimensional thermo-mechanical FE model was developed to simulate the temperature field and the residual stress field incorporating the experimental results. The thermo-mechanical model used as well as the experimental procedure is described in detail, and the results obtained from the FE model are compared with the experimental measurements and discussed.     

Residual stress analysis of structural stainless steel sections

The magnitude and distribution of residual stresses in structural carbon steel sections have been thoroughly investigated. However, few residual stress measurements have been made on structural stainless steel sections. Stainless steel has differing material stress-strain characteristics and thermal properties to carbon steel, both of which influence the formation of residual stresses. This suggests that established carbon steel residual stress models may not be appropriate for stainless steel. With increased use of stainless steel in load bearing applications, it is important to establish the residual stresses that exist within structural members. An experimental program to quantify the residual stresses in stainless steel sections from three different production routes has therefore been carried out. Comprehensive residual stress distributions have been obtained for three hot rolled angles, eight press braked angles and seven cold rolled box sections, with a total of over 800 readings taken. This paper presents the experimental techniques implemented and the residual stress distributions obtained as well as discussing the assumptions commonly made regarding through thickness residual stress variations. In the hot rolled and press braked sections, residual stresses were typically found to be below 20% of the material 0.2% proof stress, though for the cold rolled box sections, whilst membrane residual stresses were relatively low, bending residual stresses were found to be between 40% and 70% of the material 0.2% proof stress.     

冷成型钢截面残余应力的有限元分析

冷成型钢截面上的残余应力可能是决定其性能和强度的一个重要因素。通过破坏性的试验方法对残余应力进行测量不仅费时,精度也很有限。本文提出了一个预测压弯成形薄壁截面上残余应力的有限元方法,该方法克服了实验室测量的缺点,提供了一个有力的工具来考察不同的成形参数对残余应力的大小和分布的影响,并因此可以对这些成形参数进行优化。在该方法中,通过解析的方法考虑了成卷和开卷的影响,并将得到的残余应力作为随后的冷弯过程有限元模拟的初始应力。经比较,本文方法的数值结果和实验室实测值吻合很好,证明了该方法的可行性和精度。本文方法给出了整个截面残余应力的分布和沿壁厚的变化,并解释了两个相同截面中残余应力可能会存在很大差别的原因。     

Residual stresses in cold-rolled stainless steel hollow sections

Stainless steel exhibits a pronounced response to cold-work and heat input. As a result, the behaviour of structural stainless steel sections, as influenced by strength, ductility and residual stress presence, is sensitive to the precise means by which the sections are produced. This paper explores the presence and influence of residual stresses in cold-rolled stainless steel box sections using experimental and numerical techniques. In previous studies, residual stress magnitudes have been inferred from surface strain measurements and an assumed through-thickness stress distribution. In the present study, through-thickness residual stresses in cold-rolled stainless steel box sections have been measured directly by means of X-ray diffraction and their effect on structural behaviour has been carefully assessed through detailed non-linear numerical modelling. Geometric imperfections, flat and corner material properties and the average compressive response of stainless steel box sections were also examined experimentally and the results have been fully reported. From the X-ray diffraction measurements, it was concluded that the influence of through-thickness (bending) residual stresses in cold-rolled stainless steel box sections could be effectively represented by a rectangular stress block distribution. The developed ABAQUS numerical models included features such as non-linear material stress-strain characteristics, initial geometric imperfections, residual stresses (membrane and bending) and enhanced strength corner properties. The residual stresses, together with the corresponding plastic strains, were included in the FE models by means of the SIGINI and HARDINI Fortran subroutines. Of the two residual stress components, the bending residual stresses were found to be larger in magnitude and of greater (often positive) influence on the structural behaviour of thin-walled cold-formed stainless steel sections.     

Proposed residual stress model for roller bent steel wide flange sections

The manufacturing process of structural wide flange steel sections introduces residual stresses in the material. These stresses due to hot-rolling or welding influence the inelastic buckling response of structural steel members and need to be taken into account in the design. Based on experimental data standardized residual stress models have been proposed for inclusion in inelastic buckling analyses. By incorporating these residual stress models their effect on the resistance of beams and columns can be obtained. Residual stress models for roller bent steel sections are currently not available. Roller bent wide flange sections are manufactured by curving straight members at ambient temperature. This manufacturing technique, which is also known as roller bending, stresses the material beyond its yield stress, thereby overriding the initial residual stresses prior to bending and generating an entirely new pattern. This paper proposes a residual stress model for roller bent wide flange sections, based on earlier conducted numerical investigations which were validated by experimental research performed at Eindhoven University of Technology. The proposed residual stress model can serve as an initial state of a roller bent steel section in fully non-linear finite element analyses to accurately predict its influence on the inelastic buckling response.