Welding-induced Residual Stresses Research Articles

Structural fatigue investigation of thermite welded rail joints considering weld-induced residual stress and stress relaxation by cyclic load

This study developed a structural fatigue life prediction model of thermite welded rail joints taking account of the weld-induced residual stress and stress relaxation by external cyclic load. A three-dimensional finite element model including the sequentially coupled thermal–mechanical simulation and cyclic plasticity constitutive simulation was developed to investigate the welding process induced residual stress and the redistribution of the residual stresses due to cyclic bend fatigue loading, respectively. The numerical results of the finite element model were compared with experimental residual stress data to confirm the accuracy of the model developed. The fatigue crack propagation life prediction taking into account the as-welded residual stress and the stress redistribution was performed. The predicted life of weld-toe cracks at web-to-base location will be overestimated by at least 50% if residual stress and relaxation is not considered.

Friction stir welding induced residual stresses in thick steel plates from experimental and numerical analysis

ABSTRACT Friction stir welding induces a relatively low level of deflection, and residual stresses and recent advances in the welding technology has shown that friction stir welding may now be broadly used in steel welding leading to significant improvement of the welding quality for new constructions and repairs. In the present study experimental and numerical analyses of friction stir welding in thick steel plates are performed. A finite element model is developed, based on a new heat input source mathematical formulation, accounting for the welding transient thermo-mechanical process of the friction stir welding-induced residual stresses. The welding-induced residual stresses, estimated by the new developed finite element model, are compared with the experiment. The present study shows that the newly developed heat source finite element model demonstrates an acceptable agreement between the numerical and experimental results. A sensitivity analysis concerning the essential governing parameters predicting the friction stir welding – induced residual stresses is also addressed.

Prediction of Reheat Cracking Behavior in a Service Exposed 316H Steam Header

Reheat cracking in an ex-service Type 316H stainless steel steam header component has been investigated in this study. The examined steam header was in service for 87,790[Formula: see text]h and the cracks in this component were found in the vicinity of the weld toe. The root cause of this type of failure was due to the welding residual stresses. The welding-induced residual stresses had been present in the header at the early stage of the operation and were released during service. In this paper, a novel technique has been proposed to simulate the residual stress distribution normal to the crack direction by applying remote fixed displacement boundary conditions in an axisymmetric model. This approach can simulate the presence of residual stresses in actual components without the need to develop full weld simulation to quantify them. The predicted residual stress levels and distributions normal to the crack direction have been found in good agreement with the measured residual stresses available in the literature for a similar header. The creep crack growth (CCG) rates have been characterized using the fracture mechanics [Formula: see text] parameter and estimated using predictive models.

Ultimate Compressive Strength Computational Modeling for Stiffened Plate Panels with Nonuniform Thickness

The aim of this paper is to develop computational models for the ultimate compressive strength analysis of stiffened plate panels with nonuniform thickness. Modeling welding-induced initial deformations and residual stresses was presented with the measured data. Three methods, i.e., ANSYS finite element method, ALPS/SPINE incremental Galerkin method, and ALPS/ULSAP analytical method, were employed together with existing test database obtained from a full-scale collapse testing of steel-stiffened plate structures. Sensitivity study was conducted with varying the difference in plate thickness to define a representative (equivalent) thickness for plate panels with nonuniform thickness. Guidelines are provided for structural modeling to compute the ultimate compressive strength of plate panels with variable thickness.

Study on Ultimate Compressive Strength of Aluminium-Alloy Plates and Stiffened Panels

This work reviews the ultimate compressive strength of aluminium plates and stiffened panels. The effect of boundary condition, initial imperfection, welding-induced residual stress and heat-affected zone are discussed. As the effect of manufacturing technology lacks in the literature, this effect is analysed employing the finite element method, considering the technology of welding and integrated extrusion. The numerical analyses have shown that the ultimate strength of the integrated extruded stiffened panel is relatively higher than the one of the traditional welded panel.

Fatigue Strength Assessment of a Butt-Welded Joint in Ship Structures Based on Time-Domain Strain Approach

Fatigue strength assessment of a butt-welded joint in ship structures based on a time-domain strain approach is performed in this study. The service life load histories applied to the butt-welded joint located on the deck of a bulk carrier are generated, accounting for the still-water and wave-induced loads. The rainflow counting method is applied to analyze the load histories, and the long-term distributions of the load range are compared with those based on the conventional spectral fatigue analysis. An approach of converting the load history to a series of closed notch stress-strain hysteresis loops and several open notch stress-strain hysteresis curves is proposed and demonstrated under variable amplitude loading. The approach is based on analytical notch stress-strain estimations and consists of several steps to consider the material memory effect, overcoming some limitations of the existing methods. To determine the fatigue damage for the variable amplitude loading, a design fatigue curve is derived considering the uncertainty in the fatigue lives and load sequence effects. The intrinsic fatigue limit concept is used to filter the small amplitude cycles that do not have a damaging effect. The fatigue strength of the butt-welded joint is analyzed, taking the weld-induced residual stress and misalignment effects into account explicitly. The notch mean stresses or strain amplitudes of the cycles are significantly enhanced because of the presence of a high level of weld-induced tensile residual stress or misalignment, resulting in highly severe fatigue damage. 1. Introduction Complex ship structures containing geometrical and material discontinuities are prone to fatigue because of cyclic loads. Therefore, fatigue strength assessment has been an important criterion in the ship structural design (Guedes Soares & Moan 1991). Various fatigue design concepts for the assessment of welded joints, where fatigue failures mostly originate, are applied (Xu 1997; Radaj et al. 2006), and they can be classified into two types. The first one is based on S-N curves in combination with the Palmgren-Miner rule, and the second one is based on the crack propagation models and failure criteria.

Direct measurements and numerical predictions of welding-induced initial deformations in a full-scale steel stiffened plate structure

Abstract As a sequel to another paper of the authors on welding-induced residual stresses [1], this paper aimed to obtain a direct measurement database of welding-induced initial deformations in a full-scale steel stiffened plate structure and also to study the applicability of computational models to predict them. A full-scale steel stiffened plate structure in association with bottom plate panels of an as-built 1,900 TEU containership was fabricated by exactly the same technology of welding as used in today's shipbuilding industry. The 3D scanner was employed to measure welding-induced initial deformations of the structure. Computational models using the three-dimensional thermo-elastic-plastic finite element method were developed to predict the plate initial deflections. A comparison between direct measurements and numerical predictions was made. Details of direct measurement databases are documented as they are useful to validate the computational models formulated by other researchers.

On residual stress analysis and microstructural evolution for stainless steel type 304 spent nuclear fuel canisters weld joint: Numerical and experimental studies

Chloride-induced stress corrosion cracking (CISCC) in the weldments of austenitic stainless steel canisters is one of the primary safety concerns during the dry storage of used nuclear fuel at Independent Spent Fuel Storage Installations in coastal areas. In order to evaluate the CISCC behavior in the canister, a 3D sequentially coupled thermo-mechanical finite element model was built to simulate the residual stresses induced by two intersecting longitudinal and circumferential multi-pass welds in austenitic stainless steel mockup canister. Weld-induced residual stresses from simulation were in good agreement with the experimental measurement results by deep-hole drilling and contour methods. Through-wall high tensile axial and hoop stresses were observed in both the fusion zone and heat affected zone (HAZ) in the longitudinal and circumferential weld, respectively. On the other hand, the microstructure within the weldments of 304 stainless steel mockup was characterized using optical microscopy, scanning electron microscopy, electron back-scattered diffraction and energy dispersive X-ray spectroscopy methods. A few amount of MnS inclusions in both the base metal and HAZ, and a lot of (Mn,Si)xOy inclusions in the fusion zone were found. Meanwhile, there is some α′-martensite in the base metal, while the martensite was reversed in the HAZ. In the fusion zone, there is a lot of δ-ferrite. The martensite reversion phenomenon was also verified by the combination of Feritscope test and thermal simulation, which could predict a martensite reversion temperature as 400C°. The welding residual stresses and microstructure analysis results could offer the instructive information for the prediction of CISCC behavior of the spent nuclear fuel canisters.

Probing residual stresses in stationary shoulder friction stir welding process

Stationary shoulder friction stir welding (SSFSW) is a new variant of the conventional FSW with rotation of only the tool probe to reduce the rate of heat generation along the tool–workpiece interface and hence, weld joint residual stresses. Studies on the evolution of residual stresses in SSFSW are rare as the process is new. A detailed investigation on the evolution of welding-induced residual stress is reported here for SSFSW and the conventional FSW of four different aluminum alloys. A finite element method–based numerical model, JWRIAN-Hybrid, is used for the three-dimensional heat transfer and thermo-mechanical stress analyses. The computed results are validated extensively with the corresponding experimentally measured results. The results show approximately 10% to 20% reduction in the peak residual stresses in SSFSW under identical welding conditions.

Experimental Study of Residual Stresses in Hybrid Laser Arc and Submerged Arc-Welded 10-mm-Thick Low-Carbon Steel Plates

Abstract Offshore structures are constantly exposed to a multihazard marine environment that threatens their structural integrity. This imposes a high risk for extensive structural failures while various deterioration mechanisms may degrade the available capacity of the structures. Thus, no reliable decisions can be reached regarding design, operation, and survivability of the structures unless a deep comprehension of their fatigue performance is available, including welding-induced residual stresses. In particular, the continuous increase in size of the weldments for the offshore wind industry needs special attention with regard to welding-induced residual stresses, as they can reduce fatigue life, promote distortion, and contribute to stress corrosion cracking. Thus, the current design methods and increased structural dimensions as well as new design and manufacturing methods need to be inspected, understood, and optimized. Related to this, there is a growing need for evaluation of the effect of welding methods with various heat input density distributions. This article deals with the influence of welding method on the welding-induced residual stresses in 10-mm-thick low-carbon structural steel plates. The residual stresses are investigated in hybrid laser-arc welded and submerged arc butt-welded steel plates by means of experimental temperature profile measurements and neutron diffraction measurements and in accordance with existing production procedures. The residual stresses were measured at three different depths in the plates. The goal of the analysis is to gain a comprehensive understanding of the distribution and development of residual stresses in relation to the welding method for better control of the residual stresses and distortion. The repeatability of the neutron diffraction measurements is also investigated and reported in this article.

Thermomechanical parametric studies on residual stresses in S355 and S690 welded H-sections

In order to examine and compare welding-induced residual stresses in welded H-sections of different steel grades and heat input energy, extensive parametric studies were carried out using fully calibrated and highly efficient finite element models to perform coupled thermomechanical analyses. Numerical results including temperature history and distributions, residual stress distributions and magnitudes, and force equilibrium were discussed, and comparisons were made between calibrated finite element models with different steel grades, and different heat input energy during welding.It was established that the residual stresses in S690 welded H-sections were proportionally less pronounced when compared with those in S355 welded H-sections of similar dimensions. Residual stresses in multi-pass S355 and S690 welded H-sections were shown to be significantly reduced, when compared with those in single-pass welded H-sections of similar dimensions. A simplified pattern was proposed to describe both the distributions and the magnitudes of residual stresses, and a set of formulae was also provided. It was confirmed that the residual stress pattern given in a definitive ECCS document for S355 sections was very conservative, and applicability of that pattern to S690 welded H-sections would significantly over-estimate residual stresses in these S690 sections. Hence, the proposed residual stress pattern together with the set of formulae for both S355 and S690 welded H-sections with single-pass and multi-pass welding should be adopted for accurate prediction of their structural behaviour.

An ICME Modeling Application for the Optimization of a Tie-Down Weld Sequence in Ship Production

Aircraft tie-downs have been widely used to secure airplanes, helicopters, and other transportation vehicles to a ship's deck. A multi-pass welding process is typically used for integrating tie-downs to the deck plate to develop the required strength at the joint. During and after welding, the surrounding deck material around the tie-downs must deform elastically to preserve dimensional continuity, creating residual stresses. Weld-induced residual stress is a major concern because the tie-downs are subject to cyclic, dynamic loading which could induce cracking and directly impact the fatigue life of the deck plate structures during services. To select an optimized welding sequence that minimizes weld-induced residual stress in the welded joint, an integrated computational materials engineering approach was used to evaluate the effect of welding sequences on residual stress distributions. Various deck materials (including ABS Grade DH36 and HSLA-100 steel alloys) and welding sequences were investigated to identify the optimized welding sequence which reduced radial residual stress distribution, resulting in lower final deck plate distortion. 1. Introduction Like many heavy industries, shipbuilding has a need for developing lightweight, high-strength, durable structures to improve payload capacity and mission performance, and reduce total ownership costs. The engineering design criteria and the thin-steel alloy material advancement developed to meet these requirements has outpaced the improvement of many manufacturing processes, necessitating a greater understanding of the influence of material properties on producibility issues during construction that could impact the performance of ship structures at sea. Residual stresses are "locked-in" stresses that develop in materials and structures because of welding or material handling processes during manufacturing that are independent of the presence of any external loads. Typical residual stress-induced buckling distortions in ship structures are developed as an elastic response to any incompatible local plastic strains that exist in the material after welding (Huang et al. 2003, 2004).

Effect of Rate of Heat Input on Thermomechanical Tensioning for Distortion Mitigation

Effect of Rate of Heat Input on Thermomechanical Tensioning for Distortion Mitigation

Numerical Comparison of Cruciform weld and Butt weld simulation and a Study of Fracture Mechanics on Two Types of Welds

The modeling of the welding is desirable to guess the deformation of the components during manufacture, the position and the magnitude of maximum residual stresses and to envisage metallurgical effects in specific zones. The welding are problems of complex modeling requiring the thermal and structural solutions. This has to lead to the development of several software packages and codes for simulation by finite elements. The welding condition, the properties of the structure and their interactions have significant influences on the thermal and structural responses (temperature history, distortion, and residual stress) in welded structures. This paper presents a finite element procedure for the prediction of welding-induced residual stresses and distortions. Comparison is made with tow numerical example. The first example is a butt welded joint of two plates, while the second is a Cruciform welded joint of two plates with four passes. Moreover, a comparison between the Cruciform weld and the butt-weld which we can obtain the parameters of the linear fracture mechanics; stress intensity factor K and energy release rate G.

Residual Stress Distribution Analysis in Advanced Materials by Neutron Diffraction: The Case of Spherical Storage Tank Butt Weld

The two-axis diffractometer SPN-100 at the Center of Accelerators and Nuclear Analytical Methods (CANAM) in Řež, is a neutron diffraction instrument dedicated to residual stress analyses in polycrystalline materials, it has recently been equipped with a new two-dimensional position sensitive detector (2D-PSD) and a six-axis robotic arm for sample positioning. Recent results of strain/stress distribution measurements with the upgraded tools are presented. The measured materials are made of C-Mn unalloyed steel used for spherical storage tank. Welding-induced residual stresses have direct influence on ductility and toughness of both weld metal and heat affected zone of the weld area, which affect the service life time of structures. Normal, transversal and longitudinal components of the stresses obtained in the vicinity of the butt weld from a spherical storage tank were measured by neutron diffraction at CANAM.

Numerical investigation on the residual stresses in welded T-joints made of dissimilar materials

This study used the Finite Element (FE) method to numerically analyze the thermo-mechanical behavior and residual stresses in dissimilar welded T-joints. Residual stresses induced by the fusion arc-welding of steel joints in power generation plants are a concern to the industry. The structural integrity assessment of welded structures requires the consideration of weld-induced residual stresses for the safe operations in power plants, which may be compromised by their presence. Details on the used thermo-mechanical FE model and the results analysis are herein presented.

Inspection of the residual stress on welds using laser ultrasonic supported with finite element analysis

Ultrasonic evaluation for residual stress measurement has been an effective method owing to its easy implementation, low cost and intrinsically being nondestructive. The velocity variations of acoustic waves in materials can be related to the stress state in the deformed medium by the acoustoelastic effects. In this study, a laser/EMAT ultrasonic method is proposed to evaluate the surface/subsurface longitudinal residual stress distribution generated by gas metal arc welding (GMAW). The velocity variation ΔV/V of Rayleigh wave, which is a surface wave, will be experimentally measured. Q-Switched Nd:YAG laser is used to generate a broadband ultrasonic wave. An electromagnetic acoustic transducer (EMAT) is attached to the welding plate for Rayleigh wave pick up. As the ultrasound receiver, the EMAT is used to measure time of flight (ToF) of the Rayleigh waves traveling along a specific path parallel to the direction of the welding seam. ToF measurements are obtained by changing Rayleigh wave path to welding zone center distance from 0 to 45 mm. A 3D thermomechanical-coupled finite element model is then developed to validate the capability of the proposed technique for welding-induced residual stress evaluation. The distributions of the normalized velocity variations from ToF experiments are compared with the distribution of the normalized longitudinal residual stresses from finite element analysis (FEA). It has been shown that there is a good correlation between these two distributions. The proposed technique provides a potential nondestructive avenue for surface/subsurface residual stress evaluation for welding parts.

Finite element analysis of thermal residual stresses in castellated beams

The objective of the study is to numerically investigate the residual stresses in castellated beams. The fabrication processes with cutting and welding will significantly change the residual stresses of the castellated beam compared to its parent I-beam (or H-beam). These residual stresses have a significant impact on the lateral-torsional buckling resistance of castellated beams. However, due to the complexity of the problem, the investigations are far from complete. In this study, three-dimensional finite element models are developed to simulate the thermal residual stresses in the castellated beams due to the cutting and welding fabrication processes. The temperature fields and the cutting-induced and welding-induced residual stresses are numerically investigated. In addition, the predicted thermal residual stresses are then validated with experimental results in the literature. With the validated model, a parametric study is conducted to investigate the effects of the sectional parameters on the thermal residual stresses, including the flange thickness (tf), the flange width (bf), and the thickness of the web (tw), etc. Then, the influences of tf, bf, and tw, etc. on the thermal residual stresses at the flange tips are compared. Finally, the potential development of residual stress distributions in castellated beams is discussed.

Evaluation of multi-pass welding-induced residual stress using numerical and experimental approaches

ABSTRACTIn the present work the welding-induced residual stresses in steel plates, due to multi-pass welding are investigated numerically and experimentally. The transient finite element model is developed to estimate the axial residual stresses induced by butt welding. Element birth and death technique is used to simulate the welding process in ANSYS. Plates with 6 mm thicknesses are modelled by one and three passes of welding to investigate the effect of multi-pass welding on the induced residual stress. An experimental study is performed to calibrate the numerical results for both thermal and mechanical analyses. The X-ray diffraction method is used for measuring the residual stress. A good agreement is achieved between numerical and experimental results. It is concluded that, multi-pass welding has significant effects on the residual stress distribution.

Influence of weld-induced residual stresses on the hysteretic behavior of a girth-welded circular stainless steel tube

The present study attempts to characterize the relevance of welding residual stresses to the hysteretic behaviour of a girth-welded circular stainless steel tube under cyclic mechanical loadings. Finite element (FE) thermal simulation of the girth butt welding process is first performed to identify the weld-induced residual stresses by using the one-way coupled three-dimensional (3-D) thermo-mechanical FE analysis method. 3-D elastic-plastic FE analysis equipped with the cyclic plasticity constitutive model capable of describing the cyclic response is next carried out to scrutinize the effects that the residual stresses have on the hysteretic performance of the girth-welded steel tube exposed to cyclic axial loading, which takes the residual stresses and plastic strains calculated from the preceding thermo-mechanical analysis as the initial condition. The analytical results demonstrate that the residual stresses bring about premature yielding and deterioration of the load carrying capacity in the elastic and the transition load ranges, whilst the residual stress effect is wiped out quickly in the plastic load domain since the residual stresses are nearly wholly relaxed after application of the cyclic plastic loading.