Welding Residual Stress Field Research Articles

Analysis of circumferential CO2 arc welding welded shield machine hob to investigate the welding residual stress fields

Analysis of circumferential CO2 arc welding welded shield machine hob to investigate the welding residual stress fields

Numerical study of full penetration single- and double-sided U-rib welding in orthotropic bridge decks

Under the repeated action of residual stress and wheel load caused by welding, fatigue cracks easily occur on the top plate-U rib welding of an orthotropic bridge deck (OBD). These affect the service life. To study the influence of different full-penetration welding methods on the residual stress and fatigue of OBD, this study compared the residual stress, welding deformation, and fatigue performance of full-penetration single- and double-sided welding through finite element analysis. The welding temperature and residual stress fields were simulated based on Goldak's double ellipsoid heat source model using the thermal elastic-plastic method. The numerical results were verified using measured data from relevant literature, and the two were in good agreement. The results showed that the longitudinal residual stress of the double-sided welded U-rib was larger than that of the single-sided welded U-rib, primarily in the compressive stress range, and the maximum deviation reached 99.44 MPa. The longitudinal displacement of single-sided welding along the weld direction was 0.060 mm lesser than that of double-sided welding, and the maximum vertical displacement perpendicular to the weld direction was 2.457 mm lesser than that of double-sided welding. For the same frequency of fatigue load (wheel load), the fatigue strength of single-sided welding was larger than that of double-sided welding, and the fatigue life increased by 29.7%. In this study, analysis models of the full-penetration single-sided and full-penetration double-sided welding were established, which could provide a reference for structural fatigue assessment using the two full-penetration welding techniques under the influence of residual stress.

Hydrogen diffusion simulation of the X80 pipeline steel girth weld zone considering the synergistic effect of the structure–stress–concentration field

Hydrogen embrittlement failure, caused by hydrogen permeation and diffusion in the girth weld zone of pipelines, is the main obstacle to large-scale hydrogen blending transportation. Accordingly, a three-dimensional model of the girth weld zone of X80 pipeline steel was established. Considering the influence of structural inhomogeneity in the weld zone, multi-field sequential coupling simulation technology was used to analyze the diffusion process of hydrogen under the combined action of the residual stress and hydrogen concentration fields. A synergistic mechanism between hydrogen enrichment, structural characteristics, and residual stress in the weld zone was revealed. The results indicated that the structural inhomogeneity in the girth weld zone and residual stress field significantly influenced the hydrogen concentration distribution. Moreover, for the hydrogen diffusion process at the grain boundaries, the impact of the residual stress was greater than that of the structural inhomogeneity. This study further clarifies the spatial distribution of hydrogen atoms induced by multi-field coupling in the weld zone and provides a reference for the safety assessment of girth weld layers from an engineering perspective.

Digital twin-driven framework for fatigue life prediction of welded structures considering residual stress

The welding of steel generates substantial welding residual stress (WRS), which exerts a significant impact on the fatigue life of steel bridges. In this study, a physical model for calculating the fatigue crack growth (FCG) life of welded specimens in the WRS field is established based on the weight function method. Experimental data validates the reliability and precision of the proposed physical model. The impact of WRS on the fatigue life of structural components is scrutinized and analyzed. On this basis, a digital twin (DT) framework driven by a physical-data model is proposed to consider the inherent parameter uncertainty in FCG behavior within the WRS domain. A dynamic Bayesian network (DBN) is used to characterize the evolution characteristics of fatigue crack states over time in the digital space. Particle filter algorithm is used as DBN inference method. The results show that the calculation of the physical model is in good agreement with the experimental values. Neglecting the influence of WRS distribution may lead to an overestimation of fatigue life in welded structures. The DT framework can update uncertain parameters online and realize the accurate prediction of the FCG life in the WRS field.

Role of welding residual stress in stainless steel piping with application of the leak-before-break technology

The predicted leakage rate of piping circumferential through-wall cracks (CTWC) under various loading levels is a critical factor for the application of leak-before-break (LBB) technology. In current engineering approaches, the effect of welding residual stress has not been carefully taken into account. In this paper, both numerical analyses and comparative verification are adopted to examine the influence of typical welding residual stress field on the crack opening displacement for austenitic stainless steel piping with representative geometric dimensions and in situ measured material performance curves. An in-depth investigation is carried out to reveal the effect of the residual stress on morphological parameters of the CTWC flow channel. In the case where the residual internal stress of welding has the greatest effect, the Henry-Fauske model is employed to analyze the flow medium passing through the CTWC and the corresponding leak rate for a typical nuclear power plant. The results indicate that the welding residual stress leads to a substantial change in the crack opening displacement and crack morphology parameters. Both the current GE/EPRI method and the NUREG/CR-6837 modification recommended by the American Electric Power Research Institute underestimate the effect of this phenomenon, resulting in a higher prediction of the medium leakage rate. A similar situation is most likely to occur for the cases of short cracks in thin-walled piping and long cracks in thick-walled piping. Additionally, the obtained results reveal that the welding residual stress causes the whole crack surface to open negatively, and the axial line of the long crack on the thick-walled piping is close to a conic curve under specific conditions.

BÉZIER BASE EXTENDED ISOGEOMETRIC NUMERICAL METHOD FOR THERMO ELASTIC-PLASTIC ANALYSIS OF CRACK PROPAGATION IN CRACKED PLATE UNDER WELDING RESIDUAL STRESS AND THERMAL LOAD

A new procedure in the field of Bézier base extended isogeometric method (XIGA) has been introduced to analyze the effect of welding residual stress and thermal load on crack propagation rate and fatigue life. This new procedure is based on the constitutive thermoelastic plastic equation. The main parts of this procedure are using the B´ezier base XIGA method to calculate the redistribution of welding residual stress due to crack growth and to compute the value of stress intensity factor (SIF) in the welding residual stress field. For this purpose, the grid points of Bézier elements (with C0-continuity) around the crack line and the crack tip are identified by the level set representation. Then, discontinuous enrichment functions are added to the isogeometric analysis approximation. Thus, this method does not require the re-meshing process. The results show that there is a good agreement between the results of proposed numerical method and the Hole-Drilling Strain-Gage method. The interaction integral method has been used to extract SIF. The effects of welding residual stress and thermal load on the SIF are considered using the superposition method. Also, the Walker equation has been modified to calculate the fatigue life caused by thermal loading and welding residual stress. The results display a good agreement between the proposed method and the finite element method. Due to the advantages of the Bézier based XIGA method, which eliminates parametric space and allows the precise addition of enrichment functions to the basis functions of cracked elements (crack line or crack tip), the obtained results are highly accurate that shows this method is effective for analyzing discontinuous problems.

Determination of the three-dimensional welding residual stress in a thick plate T-welded joint using the stepwise eigenstrain-contour method

The stepwise eigenstrain-contour method (SECM) for determining three-dimensional welding residual stress (WRS) was developed based on conventional eigenstrain-contour method. A thick plate T-welded joint specimen was manufactured and its three-dimensional WRS was measured via the SECM. The SECM was then verified by the superposition method, which obtains the three-dimensional WRS on the cut surface by superposing the measurement results of the hole-drilling method and the standard contour method. Finally, the three-dimensional eigenstrain field and WRS field in the thick plate T-welded joint specimen were comprehensively analyzed. The results show that the SECM greatly improves the reconstruction accuracy of the WRS components in non-principal directions of the welded joint, thus extending the standard contour method to three-dimensional WRS measurement. Overall, the three-dimensional WRS in the specimen presents self-equilibrated tension-compression distribution. The peak longitudinal, transverse and vertical WRSs on the whole mid-length section of the specimen are 382.3 MPa (0.92 σy), 152.7 MPa (0.37 σy) and 105.8 MPa (0.26 σy) respectively, which usually appear near the bottom of weld zone. The transverse and vertical WRSs are usually smaller than the longitudinal WRS, and the WRS in the flange is generally greater than that in the web.

Nondestructive Evaluation of Stress Corrosion Cracking in a Welded Steel Plate Using Guided Ultrasonic Waves

Abstract Stress corrosion cracking (SCC) had occurred in early-generation high-level nuclear waste tanks constructed by welding carbon steel. This paper describes an ultrasonic inspection system and its fundamental ability to detect and quantify the length of SCC on thick welded steel plates. The finite element method (FEM) was applied to simulate the welding process to estimate the welding residual stress field. Growth of stress corrosion cracks is driven by crack stress intensities exceeding the subcritical cracking threshold intensity. The subject plate was experimentally inspected with ultrasonic nondestructive evaluation (NDE) techniques to characterize the extent of SCC. The NDE system uses a piezoelectric transducer to generate guided waves in the thick steel plate, and a scanning laser Doppler vibrometer (SLDV) to measure multidimensional time–space wavefield data over a user-defined scanning area in the plate surface. The measured wavefield data can show wave interactions in a localized area in the plate due to the presence of the discontinuities of the SCC. To generate an inspection image that can precisely show the crack’s location and/or the dimension, the wavefield data are further processed to generate inspection image that maps the entire sample plate so the crack can be clearly identified in the plate while its length can be readily estimated. The ultrasonic test results for crack length agree well with the visually estimated length and are close to that predicted by the FEM for cracks in the weld residual stress field.

On the performance of monopile weldments under service loading conditions and fatigue damage prediction

AbstractThick weldments used in offshore structures frequently act as fatigue crack initiation sites due to stress concentration at weld toe as well as weld residual stress fields. This paper investigates the cyclic deformation behavior of S355 G10+M steel, which is predominantly used in offshore wind applications. Owing to the vast size difference of monopile structure and weld cross‐section, a global–local finite element (FE) method was used, and the weld geometry was adopted from circumferential weld joints used in offshore wind turbine monopile foundations. Realistic service loads collected using supervisory control and data acquisition (SCADA) and wave buoy techniques were used in the FE model. A nonlinear isotropic–kinematic hardening model was calibrated using the strain controlled cyclic deformation results obtained from base metal (BM) as well as cross‐weld specimen tests. The tests revealed that the S355 G10+M BM and weld metal (WM) undergo continuous cyclic stress relaxation. Fatigue damage over a period of 20 years of operation was predicted using the local stress at the root of the weldments as the life limiting criterion. This study helps in quantifying the level of conservatism in the current monopile design approaches and has implications towards making wind energy more economic.

Fatigue Crack Propagation Analysis of Orthotropic Steel Bridge with Crack Tip Elastoplastic Consideration

Abstract: Due to the complex structure of the orthogonal steel bridge deck and dense weld, fatigue cracks are prone to occur in the typical welding details. Welding residual stress will cause a plastic zone at the crack tip. In this paper, an elastoplastic constitutive model of Chaboche material was introduced, and the extended finite element method (XFEM) was used to study the influence of material elastoplasticity and crack tip plastic zone on the law of fatigue crack propagation. By judging the stress state of the residual stress field at the crack tip and selecting different crack propagation rate models to investigate the crack propagation law when plastic deformation was considered, the propagation path and propagation rate of fatigue crack of the orthotropic bridge deck were obtained. The results show that, whether the residual stress field is considered or not, the plastic deformation at the crack tip will not cause the obvious closure of the fatigue crack at the U-rib toe during the crack propagation process, but will significantly affect the crack propagation path. When material plasticity is considered, the propagation angle of fatigue crack at the U-rib toe basically remains unchanged along the short-axis direction of the initial crack, but increases along the long-axis direction, and the crack tip plastic zone inhibits the propagation of the crack tip on one side. Compared with linear elastic materials, the crack propagation law considering material plasticity is more consistent with the actual fatigue crack propagation law in bridge engineering. In terms of the propagation rate, if the residual stress field is not considered, the fatigue crack propagation rate at U-rib toe with plasticity considered is slightly higher than that without plasticity considered, because plastic deformation will affect the amplitude of energy release rate. When considering the welding residual stress field, the fatigue crack propagation rate at U-rib toe is increased due to the combined actions of plastic deformation and stress ratio R.

Numerical simulation on residual stresses of stainless steel SS-304 thin welded pipe

The major concern in the high tech industries like oil and petroleum industries, automobiles, aeronautical, and nuclear power plants is the control of the defects like distortion in the welded joints and residual stresses occur due to arc welding on the circumferential joints of the thin pipes. Three-dimensional non-linear thermal and thermomechanical numerical simulations are conducted for the tungsten inert gas welding process of SS-304 stainless steel pipes. In this article, numerical analysis of the distribution of the temperature and the welding residual stress fields induced after the welding is done. Study on the effect of the welding heat input by varying the welding parameters (like welding current and welding speed) based on finite element simulations is conduit to examine the results on the residual stresses which is also called as the ‘locked-in’ stresses. The precision of the finite element model is validated for the welding residual stresses. The intention of this study is to provide the information to verify the validity of ongoing process circumferential manufacturing technology for thin-walled pipes, so to avoid the failure of these kinds of structures which are in service because of these intrinsic stresses.

Evaluation of crack opening displacement of through-wall circumferential-cracked pipe using direct weight function method

This paper presents a direct weight function-based method to evaluate the crack opening displacement (COD) which is a key parameter in leak-before-break (LBB) assessment and in probabilistic fracture mechanics (PFM) assessment of nuclear piping systems. The focus of this study is a circumferential-cracked pipe with non-linearly through-wall distributed stress loaded on the crack face. Parametric finite element analyses (FEA) were performed to calculate COD associated with different crack face pressure (CFP) loadings. The analyses matrix covers a wide range of pipe size and crack lengths. The crack mouth COD values at three locations: at outside surface, inner surface and mid-thickness were considered. The numerical results were then used to determine the coefficients that construct the direct weight functions. The proposed solution can be used to predict the COD resulted from given weld residual stress (WRS) field with the general prediction error being less than 8%. The research outcome can provide more computational efficiency in both deterministic LBB assessment as well as PFM analyses of pressurized pipes.

Numerical simulation of residual stresses in aluminum alloy welded joints

The lightweight design makes thin-plate welded structures used widely, especially for the aluminum alloy thin-plate welded structure, it is very important to study the fatigue fracture properties of the structure considering the influence of residual stress. A solid model of a butt joint of aluminum alloy with a double-pass weld is established. Both the welding temperature fields and residual stress fields are simulated through the thermal elastic–plastic method. The welding experiment is also performed with the corresponding joint, which is welded by means of metal inert-gas (MIG) welding. Consequently, the computational and experimental results of residual stress are in good agreement. Moreover, the thermal elastic–plastic method is employed to calculate the residual stress fields of typical welded joints. Based on the inherent strain theory, the transverse and longitudinal inherent strain of the joints are decomposed from the total strains and applied to both solid and shell models of the three types of joints to calculate the residual stress fields of them. The results of the solid and shell models using the two methods are practically consistent, which indicates that the inherent strain method can predict the residual stress on the shell model efficiently and accurately. Thus, the method of predicting the welding residual stress of thin-plate structures based on the inherent strain is proposed, which provides a reference for the structural fatigue assessment under the influence of residual stress.

Measurement of internal residual stress field in multi-layer fillet welded joint of ultra-thick circular plate and tube

It is well known that both the internal and surface residual stresses in welded joints have great influence on the corrosion resistance and creep and fatigue strength of welded structures. In this study, the inherent strain theory and stress released method by the electric charge cutting were used to measure the internal residual stress field in a multi-layer fillet welded joint of ultra-thick plates and tube. A L-shape sample and several C-shape samples were cut from the original plate-tube fillet welded joint to separate the efficient inherent strain components. The inherent strain components in the L-sample and C-samples were the same as those in the welded joint. They were identified by performing inversely an elastic finite element analysis. Finally, by applying the identified inherent strains into the original welded joint modeled by FEM, the 3D welding residual stress field was reproduced by elastic analysis. It was shown that the circumferential stress σθ was obviously larger than other residual stress components in the plate-tube fillet welded joint. The tensile residual stress on the welded surface was smaller than that under the surface of 10 mm. The residual stresses on the inner surface of the tube were smaller than those on the welded surface and the axial stress component on the inner surface of the tube was compressive which may be contributed by water cooling during welding.

Numerical simulation of distortion-induced fatigue crack growth using extended finite element method

Aiming to investigate the propagation behaviour of distortion-induced fatigue cracks in steel bridge web gaps, multi-scale numerical analysis models were built based on fracture mechanics theory and extended finite element method (XFEM), combining with the full-scale fatigue tests data. Propagation behaviours of representative fatigue cracks in vertical stiffener web gaps and horizontal gusset plate web gaps were analysed. Finite element models of welds connecting web, vertical stiffener and horizontal gusset plate were built, and the welding residual stresses of such details were analysed. Significant transverse welding residual tensile stresses exist at stiffener web weld toes for web gap details. Residual stress measurements were conducted, and the crack shape and the propagation direction path were basically the same with that in the numerical simulation, indicating that the numerical simulation results were relatively reliable. Furthermore, the welding residual stress fields were considered in the crack propagation analysis models. Representative fatigue cracks at web gaps are Mode I leading mixed-mode cracks of Modes I, II and III. Crack propagation considering welding residual stress has faster propagation rate and is more consistent with fatigue test results. The welding residual stress cannot be ignored for analysis and assessment of distortion-induced fatigue cracks in steel bridges.

A novel approach to evaluate mixed-mode SIFs for a through-thickness crack in a welding residual stress field using an effective welding simulation method

This paper accurately evaluates mixed-mode SIFs (MM-SIFs) for cracks in welding residual stress (WRS) fields using a novel approach based on finite element method (FEM). For this reason, the interaction integral method (IIM) available in WARP3D, an open source code, was developed to include normal and shear stress components in MM-SIF solutions. The effectiveness of the developed WARP3D-IIM was verified based on the superposition method and by means of well-established analytical and numerical reference solutions using an inclined through-thickness cracked FE model. After validating the adequacy of the developed WARP3D-IIM, different welding simulations were conducted using JWRIAN (Joining and Welding Research Institute ANalysis). JWRIAN, a sophisticated welding simulation in-house code, was adopted as a welding simulation tool to predict WRS. Different weld line (WL) orientations, as well as different perpendicular distances between WLs, were performed to investigate their influence on the behavior of MM-SIFs. The developed WARP3D-IIM and superposition method were thereafter employed to evaluate MM-SIF solutions for an inclined through-thickness crack in the simulated WRS fields. Different crack angles were also employed to examine the effect of the induced WRS on calculated MM-SIFs. SIF solutions resulting from WRS were validated with analytical reference solutions. Results showed that WRS has a considerable influence on the behavior of MM-SIFs. Moreover, WL orientation as well as the perpendicular distance between WLs revealed a significant influence on the induced WRS and thus MM-SIF solutions. On the other hand, the crack angle showed a remarkable effect on the behavior of MM-SIFs. MM-SIFs calculated at through-thickness crack fronts were influenced by the induced WRS distribution as well as crack angle.

Study on influence of three kinds of stress on crack propagation in butt welds of spiral coil waterwall for ultra supercritical boiler

The spiral coil waterwall is the main pressure parts and the core functional components of Ultra Supercritical Boiler. In the process of operation, the spiral coil waterwall is under the combined action of welding residual stress, installation defects stress and working fluid stress, Cracks and crack propagation are easy to occur in butt welds with defects. In view of the early cracks in the butt welds of more T23 water cooled walls, in this paper, the influence of various stresses on the crack propagation in the butt welds of spiral coil waterwall was studied by numerical simulation. Firstly, the welding process of T23 water cooled wall tube was simulated, and the welding residual stress field was obtained. Then,on the basis, put the working medium load on the spiral coil waterwall, the supercoated stress distribution of the welding residual stress and the stress of the working medium is obtained. Considering the bending moment formed by stagger joint which is the most common installation defects, the stress field distribution of butt welds in T23 water-cooled wall tubes was obtained by applying bending moment on the basis of the stress field of the welding residual stress and the working medium stress. The results show that, the welding residual stress is small, the effect of T23 heat treatment after welding to improve the weld quality is not obvious; The working medium load plays a great role in the hoop stress of the water cooled wall tube, and promotes the cracks in the butt welds; The axial stress on the water cooled wall tube produced by the installation defect stress is obvious, the stagger joint, and other installation defects are the main reason of crack propagation of spiral coil waterwall. It is recommended that the control the bending moment resulting from the stagger joint not exceed 756.5 NM.

Evaluation of a self-equilibrium cutting strategy for the contour method of residual stress measurement

An assessment of cutting-induced plasticity (CIP) is performed, by finite element (FE) prediction of the plastic strain accumulation along the cut tip when the EDM wire sections the NeT TG4 weld benchmark specimen along two cutting directions. The first direction corresponds to a conventional (C) cutting strategy, whereby the EDM wire cuts through the thickness of the weld specimen and travels in a direction transverse to the weld. The second direction corresponds to a self-equilibrating cutting (SE) strategy, whereby the EDM wire cuts across the transverse direction of the weld specimens and travels through the thickness of the plate. The cutting thus progresses simultaneously through the compression-tension-compression regions of present weld residual stress (WRS) field. This type of cutting strategy is believed to minimize the CIP by minimising residual stress redistribution during cutting, due to stress equilibration across the sectioned material. The simulated cutting procedures are conducted under a range of clamping conditions to assess whether mechanical restraint has a primary or secondary influence on CIP accumulation. Both predictions of CIP and the resultant back-calculated WRS demonstrate that (i) mechanical restraint is the primary variable influencing CIP development, and (ii) under no circumstance does a self-equilibrating cutting strategy perform significantly better than a conventional cutting approach. The reason that self-equilibrating cuts are not effective is illustrated by calculating the Mode I (KI) stress intensity factor (SIF) along the cut tip, and correlating trends in KI to CIP development.

Numerical and experimental description of the welding residual stress field in tubular joints for fatigue assessment

In order to achieve fatigue resistant welded structures, it is necessary to manage and control welding process-related factors which affect the fatigue strength. These factors are sometimes present as welding defects and sometimes as inevitable residual stresses which are unwanted by-products of welding processes. This subject has been treated in welding research communities since the 1950s. However, the extent of this effect was unclear and is still a matter of debate. Having advanced predictive tools for accurate determining welding residual stresses will not only lead to the possibility of considering precise welding residual stress effects during life estimation but also can be useful to have effective measures for the subsequent mitigation or modification of the welding residual stress fields. The objective of this study is to describe experimentally and numerically the welding residual stress field in welded tubular joints made of structural steel S355J2H in terms of two different case studies. Residual stresses in cylindrical specimens with dummy welds (case-1) and bead on tube welds (case-2) are determined experimentally by means of x-ray, synchrotron, and neutron diffraction techniques. The SYSWELD software is used to calculate the welding residual stresses numerically by integrating the metallurgical transformation effects in order to compute the link between material microstructure and residual stresses. Thermal and metallurgical calculations couple the temperature field and phase proportions by considering the latent heat of fusion/solidification and the transformations in the transient heat conduction equation. Obtained results which include both thermal and metallurgical history are used as input data for mechanical calculations afterward. The accuracy of the both thermal and structural models is validated through experiments for temperature distribution and residual stresses.

封止溶接によって生じる残留応力分布の適正化による原子力発電プラント予防保全・補修技術の高度化

封止溶接によって生じる残留応力分布の適正化による原子力発電プラント予防保全・補修技術の高度化