Welding Residual Stress Research Articles

Application of local fatigue approaches on corroded welded joints with consideration of weld geometry and residual stresses

Corrosion can significantly affect the fatigue strength of steel structures. On the one hand, it can cause stress concentrations by changing the surface geometry, and on the other hand, it can lead to embrittlement of the material. In welded steel components, sharp notches are already present due to the weld geometry, which may interact with the notches from corrosion. In addition, residual stresses exist in the fatigue-relevant area, which can also be partially modified by surface preparation methods such as clean blasting. In the current standards, all the mentioned effects are considered by reducing the design stress-life (SN) curves, in which all aforementioned effects are superimposed. One possibility to consider the effects separately is the application of local concepts, with which the influence of the geometry, here obtained from 3D-scans, the influence of measured residual stresses, and the influence of material can be considered individually. For butt and fillet welds investigated in this study, it could be shown that by considering the real geometry via a reverse engineered 3D-solid model, the locations of crack initiation in the fatigue tests, measured by digital image correlation (DIC), matched with the numerically predicted locations in most cases. Moreover, it was shown that by taking into account the real geometry and residual stresses, the use of local approaches can result in a substantially reduction of the scatter in SN-curves from Tσ = 2.17 to Tσ = 1.26, demonstrating the great reliability of the applied method.

Fatigue crack growth and life assessment of full penetration U-rib welded joints considering residual stresses

The combination of cyclic stresses and welding residual stresses (WRS) can significantly contribute to fatigue cracking in steel bridge decks. This study aims to investigate the effect of WRS on the fatigue life and crack propagation of single-sided and full penetration double-sided U-rib welded joints through experimental and numerical methods. Fatigue tests were conducted to study fatigue crack initiation and propagation behavior. Utilizing the ABAQUS software, a thermoelastic-plastic finite element method was employed to determine the residual stress distribution. Subsequently, based on linear elastic fracture mechanics (LEFM), fatigue crack propagation and life assessment were performed using ABAQUS and FRANC3D software under the coupling of residual stresses and external cyclic stresses. Findings reveal that WRS play a crucial role in fatigue life by altering the effective stress ratio during fatigue crack growth. The effective stress ratio ranges from 0.15 to 0.57, while the changing trends differ between single-sided and double-sided U-rib welded joints. The fatigue crack growth rate of double-sided U-rib welded joints is lower compared to single-sided U-rib welded joints with the same deck thickness. Furthermore, the introduction of WRS induces a mixed mode I, II, and III fracture at the outer weld toe of the U rib, with mode I fracture predominating, which leads to a deviation in the crack propagation path. The fatigue life prediction results agree well with experimental findings when considering WRS. Importantly, these predictions tend to be conservative, thereby ensuring safety and reliability in engineering applications.

Controlling method of the welding residual stress in support platform of hydrogenation reactor

The support platform is an essential component of a hydrogenation reactor, providing stable support for internal components and ensuring efficient reactions. However, the manufacturing method of overlay welding and complex structure of support platform unavoidably generates welding residual stresses (WRS) and stress concentration, posing a threat to operational reliability. In this paper, the WRS distribution and cracking causes of the support platform of hydrogenation reactor was studied by the finite element method (FEM) combined with experimental research. Four manufacturing processes for the support platform were compared in terms of their residual stresses, and the influence of welding heat input and fillet size on the WRS was discussed. The results indicate that the abrupt increase in residual stresses at the fillet region following the machining of the base layer has enhanced the likelihood of crack occurrence. The cumulative effect of stress concentration resulting from improper welding processes and structural discontinuities, along with the tensile stress during normal operating conditions, renders the surface layers susceptible to cracking during service. The manufacturing process significantly influences the distribution of residual stresses. To obtain a reliable and crack-resistant large-sized hydrogenation reactor support platform, a welding procedure with a certain machining allowance at the support platform location prior to overlay welding should be adopted. The fillet size has a notable effect on the residual stresses at the fillet region of transition layer. Recommended fillet sizes are 15 mm radius for the base layer, 11 mm radius for the transition layer, and 8 mm radius for the surface layer. Additionally, the heat input greatly affects the hoop stresses in the transition layer, in order to avoid the occurrence of cracks, a recommended heat input of approximately 20 kJ/cm is suggested.

Corrugated steel web I-girder welding deformation and residual stress research

The distribution law of residual stresses in the welding of corrugated steel web I-girders is still unclear. It is investigated by a combination of experiments and numerical simulations. The three-dimensional thermoelastic finite-element model of corrugated steel web and conventional flat web I-girders were established. Use the resistance strain gauge method to measure the residual stress in the welded corrugated steel web I-girders to verify the correctness of the established finite element model. Analysis of welding residual stress distribution and deformation of two types of I-girders through experimental data and numerical simulation data. The results show that the established finite-element model is correct, and the experimental residual stress values are matched with the simulated values. Two different web I-girders have significant differences in their welding residual stress distribution. At the same time by the two deformation curve can be seen, welding deformation and web shape related.

Analysis and design of column splicing flange joints with different weld types

To improve the seismic performance of steel column splicing flange joints, different weld details between the column and the flange plate were proposed in this study, and four full-scale specimens were designed and tested under cyclic loads. Finite element analysis was conducted to further check the joint performances and the weld behaviors. The hysteresis behaviors, yield moment, ductility, bolt forces, energy dissipation, stress and strains were analyzed. The parametric analysis, with finite element models validated by test results, was conducted, discussing the influences of the weld details, weld geometries and flange openings. According to the results, three of the four different weld details developed different advantages on ductility or energy dissipation capacity, bolt tension distribution, stress or strain distributions. Larger weld leg size would increase the resistance of the bolted flange splice joint, but may also cause weld residual stress and prying force. The reduction of flange opening can improve the stiffness and yield moments of the Type B flange joints. Formulas for the yield moments of the joints with recommended weld types were proposed and validated by both test and numerical analysis results, and additional formulas to check weld details were proposed for seismic design of bolted flange joints in prefabricated steel structures.

Influence of laser shock peening on Residual stress and microhardness of AA2219 friction stir weld

This work focuses on the effect of Laser Shock Peening (LSP) on residual stress (RS) and microhardness of AA2219 T87 Friction Stir Weld (FSW). FSW plate was laser peened, covering all the regions of the weld and RS measurement was carried out before and after peening. RS distribution across the weld is non-uniform, and the profile is M shaped with tensile RS near to weld center and compressive RS away from the center. The maximum tensile RS is + 123.5 MPa and + 96.7 MPa on the top and bottom surfaces, respectively. LSP has reversed the tensile RS to compressive with a single pass of peening, and the subsequent passes increased the compressive RS further. Peak tensile RS changes to compressive RS of −20 MPa, −130.2 MPa, and −195.5 MPa with single, three and six passes of peening, respectively, on the top surface. It is due to plastic deformation and strain-hardening effect induced on the surface during LSP. An increase in hardness due to LSP on the surface and subsurface levels is noticed, and increased number of passes affected higher depth.

Residual stress and microstructure control in welding of SA508 low alloy steel

Various types of solid-state phase transformation (SSPT) occur during the SA508 steel welding process, especially for multi-pass welding. The multiple thermal cycles lead to a more complex microstructure distribution and significantly influence the residual stress distribution. Therefore, to better control the microstructure and residual stress, it is necessary to optimize the process parameters which are closely related to the welding thermal cycles. This study established a thermo-mechanical-metallurgical multi-field coupling model and then validated it using X-ray and neutron diffraction residual stress measurement tests. Furthermore, the influence of welding heat input and preheating temperature on the formation of phase constituents and the ultimate residual stress field were analyzed in detail, concomitantly with a comprehensive discussion on their underlying mechanisms. The results showed that the increase of heat input expanded the domain occupied by the bainite phase, accompanied by the increase of compressive stress region. Moreover, the rise of preheating temperature promoted the bainite phase transformation, thus decreasing the longitudinal compressive stress and the stress gradient. The variation induced by welding parameters was closely related to the welding cooling rates. To obtain a full bainite and low residual stress condition of welded joint, it becomes imperative to exercise control over cooling rates, maintaining them at approximately 1.0 °C/s.

A dynamic fracture model of the pipeline with girth weld considering welding residual stresses

AbstractThe fracture analysis of girth‐welded pipes is a vital link in the integrity assessment of oil and gas pipelines. However, the effect of welding residual stresses (WRS) on the load‐carrying capacity of the girth‐welded pipe with the crack remains unclear. In this study, based on the WRS simulation results verified by the full‐scale pipe welding experiment, a dynamic fracture finite element model could describe the fracture process of the pipe with the crack in the inner surface of the girth weld considering WRS was developed by the Gurson–Tvergaard–Needleman (GTN) damage model. Based on this fracture model, the fracture behavior of the pipe under tensile load in the presence of WRS was clarified, and the effect of WRS on the load‐carrying capacity was studied. The results indicated that the critical displacement and strain capacity of the pipeline decreased by 12.42% and 13.04% due to the negative action of the WRS.

Residual stresses effects on fatigue crack growth behavior of rib-to-deck double-sided welded joints in orthotropic steel decks

Rib-to-deck (RTD) innovative double-sided welded joints have the potential to enhance the fatigue resistance of orthotropic steel decks (OSDs). However, welding residual stress (WRS) has been reported to be a contributing factor to fatigue cracking of steel bridges. This paper performed fatigue crack growth of the RTD innovative double-sided welded joints of OSD considering WRS. Firstly, a thermal-mechanical sequential coupling finite element model (FEM) of the RTD double-sided welded joints was established. The WRS distribution along the direction of deck thickness was analyzed. Secondly, the FEM of the OSD segment with crack was established. The fatigue crack behavior of RTD double-sided welded joints under the combined action of vehicle load and WRS was studied. Finally, the influences of initial crack on fatigue life was analyzed. Results indicate the distribution of the transverse WRS along the direction of deck thickness is tension-compression-tension stress, which has the characteristics of the sinusoidal function. The ∆ Keff value increases significantly considering WRS than without considering WRS during crack growth. WRS has a significant effect on fatigue life, and the fatigue life of the weld toe without considering WRS is about twice that of considering WRS. The crack depth and aspect ratio ( a0/ c0) of the initial crack affect the fatigue life of RTD double-sided welded joints.

Thermal cycle method’s applicable conditions for predicting residual stresses in low-strength steel weldments induced by arc welding

The present study purposes to systematically investigate the viability of the fast computation method “thermal cycle method (TCM)” for simulating welding residual stresses (WRS) in transforming and non-transforming low-strength steel weldments under various restraint conditions. Both experimental and finite element analysis were performed. Comparison of the predicted WRS with the measurements reveals that TCM is completely not suitable to assess WRS in the transforming low-strength steel weldments with low restraint degrees in numerical simulation. Nevertheless, that is feasible overall when the constraint degree is high, although this method reduces the accuracy of the calculated longitudinal residual stress to some extent in base material (BM). For non-transforming single-phase low-strength steels, no matter how much the restraint degree of the weldment is, it is trustworthy using TCM instead of the commonly applied moving heat source to calculate WRS for reducing the computational time. Based on the current work, the application conditions of TCM for the assessment of WRS in the low-strength steels induced by arc welding are systematically clarified.

Numerical simulation and experimental study of residual stress in dissimilar aluminum alloy laser composite welding

The study combined experimental and numerical simulation methods to investigate the distribution of residual stress in laser composite welding of dissimilar aluminum alloys 6063 and 5083. Using the Simufact Welding simulation software and a combined volume heat source, the distribution patterns of transverse and longitudinal residual stress fields at different welding speeds were analyzed. The blind hole method was used to test the residual stress after welding. The results showed that the use of a combined volume heat source model for heat source calibration yielded ideal results, and the thermal cycle curve was basically consistent with the simulation and experimental results of residual stress. As the welding speed decreased, the longitudinal residual stress of the parent material on both sides significantly decreased, while the transverse residual stress increased. The majority of tensile and compressive stresses on both sides of the 5083 and 6063 aluminum alloys decreased with a decrease in welding speed. The Von Mises equivalent stress indicated that the cooling process is the main stage for residual stress generation. When the welding speed decreased, the peak value of longitudinal residual stress on the 6063 aluminum alloy side decreased from 230 to 90 MPa, while that on the 5083 aluminum alloy side decreased from 304 to 150 MPa. These findings provide an important basis for controlling and reducing the residual stress and deformation of dissimilar aluminum alloy laser arc composite welded components.

New possibilities for laser welding of highly loaded transmission components by strategic use of simulation methods

Laser welding in transmission manufacturing opens up completely new kinds of product solutions with excellent properties in terms of wear, corrosion resistance, and service life. Current welding designs are characterized in particular by difficult-to-weld material combinations (e.g., steel versus cast iron) and a high component stiffness, which is correlated with high residual welding stresses. The major challenge for these mass-produced components remains both their crack-free weldability and their complex cyclic load capacity [U. Stamm, “Rissfreies Laserstrahlschweißen von Mischverbindungen aus Gusseisen und Einsatzstahl, Jahresbericht Fraunhofer IWS 2006” (2006); X. Shu, “Untersuchungen zum Laserstrahlschweißen von Werkstoffkombinationen aus Gußeisen und Stahl,” Dissertation, Shaker, Band 4/94 (1994), ISBN: 3-8265-0098-9; G. Göbel, “Erweiterung der Prozessgrenzen beim Laserstrahlschweißen heißrissgefährdeter Werkstoffe,” Dissertation, Fraunhofer-IRB-Verlag (2007), ISBN: 978-3-8167-7671-0]. Therefore, this contribution presents practical solutions for weld-compatible joint constructions and the reduction of residual stresses on the basis of a representative transmission design. Specifically, a systematic study is being conducted to understand and qualitatively evaluate effective methods for reducing residual weld stresses in circumferential welds. The recommendations developed as part of this study take particular account of the influence of process modifications, material conditions, and geometric aspects on weldability and component distortion. Here, structural welding simulations are performed and verified by experimental welding trials, including metallographic examinations. To ensure the required component fatigue strength, a practical concept for determining Wöhler curves is presented, which is based on structural mechanical simulations and multiaxial fatigue strength tests on simplified test specimens. The adaptations developed in this way facilitate the production of difficult-to-weld and highly stressed transmission components. In particular, time-consuming and cost-intensive iterations of laser welding tests can be significantly reduced or even eliminated [Brenner et al., “Neuere Ergebnisse zum Schweißen von Eisenbasiswerkstoffen mit Faserlasern, 5. Laser-Anwenderforum,” Strahltechnik Band 28 (2006), pp. 139–148, ISBN: 3-933762-18-9, S]. Furthermore, the systematic investigations provide effective recommendations for phenomenological understanding and solving typical welding challenges in practice [J. Standfuß, “Ganzheitliche innovative fügetechnische Konzepte am Beispiel des PKW-Antriebsstranges,” Fraunhofer Verlag (2010), ISBN: 978-3-8396-0125-9]. This applies, in particular, to load-transmitting components in the fields of e-mobility, aerospace, and industrial engineering [Wagner et al., “Entwickeln und Auslegen von lasergeschweißten Getriebe-komponenten für die Luftfahrt,” DVS-Berichte Band 365 (2020), pp. 62–69, ISBN: 978-3-96144-098-6].

Impact of Plate Thickness and Joint Geometry on Residual Stresses in 347H Stainless Steel Welds

Weldments of 347H stainless steel are potentially susceptible to stress relaxation cracking at elevated service temperatures. Mitigation of stress relaxation cracking susceptibility within a multipass weld requires a good understanding of welding practices and manufacturing techniques to control high tensile residual stresses. In this work, the dependence of residual stress distribution in 347H stainless steel on base plate thickness, joint geometry design, and preheating condition was systematically investigated by using three-dimensional finite element models. The finite element models were validated through good agreement between neutron diffraction measurements and calculated elastic strains. The single-V-groove welds with and without a preheating step all produced similar peak von Mises residual stresses, above 450 MPa, within both the fusion zone and heat-affected zone (HAZ). In plates thicker than 0.5 in. (12.7 mm), high tensile residual stress could be observed in a relatively large area, from the middle of the plate thickness to underneath the top surface. A double-V groove shifted the high tensile stress area to the middle thickness of the weld. A single-J-groove weld was able to confine the residual stress to a very small region near the middle thickness within the fusion zone and suppressed the von Mises residual stress within the HAZ to below 400 MPa.

An indentation method for measuring welding residual stress: Estimation of stress-free indentation curve using BP neural network prediction model

The measurement of welding residual stress (WRS) is necessary to formulate the stress control strategies, in order to ensure the reliability of engineering structures during their service life. The instrumented indentation technique can detect surface residual stress nondestructively with an acceptable accuracy, making it a desirable option for in-situ applications. However, it is difficult to meet the requirement for stress-free samples, particularly in the case of welded joints with non-uniform mechanical properties. In this work, the impact of stress-free indentation curves on determining WRS is furtherly studied based on the previously proposed indentation energy difference method. The WRS in a mismatched welded plate is measured using single reference method and distributed reference method, respectively. The study suggests that using the single reference method can lead to significant errors in determining the sign and magnitude of WRS in the weld zone. A prediction model combining the continuous spherical indentation (CSI) method and Back Propagation (BP) neural network is proposed to obtain the stress-free indentation curves of local positions nondestructively. And the CSI-BP method is verified through reverse finite element analysis and experiments.

Numerical investigation of effects of nickel-base alloy overlay size on the welding residual stresses in an austenite stainless steel narrow-gap girth weld

Based on the experimental measurement of the residual stress in the nickel-based alloy overlaid stainless-steel narrow-gap girth weld, an axisymmetric finite element (FE) model was established to simulate the residual stress in the girth weld to verify the model. Then a large number of numerical simulations were carried out with the verified FE model to study the effects of the size (height and length) of the nickel-based alloy weld overlay on the residual stress in the girth weld. The optimal overlay sizes to achieve sufficient depth of the compressive stress were investigated. The results show that as the overlay height increases, the hoop compressive stress depth from the inner wall at the weld centerline increases, while the range of the axial compressive stress distribution decreases. The hoop and axial compressive stress depths at the weld centerline increase as the overlay width increases, while the depth of the hoop compressive stress remains unchanged when the overlay width reaches a critical value. The effect of the overlay height on the hoop stress is greater than that of the overlay width, and it is more difficult to mitigate the axial stress by increasing the width of the overlay layer with a large overlay height. For the narrow-gap 304 stainless-steel pipe girth weld with a size of Ø273 mm × 28 mm, the optimum nickel-based alloy overlay is 14 mm in height and 210 mm in width, which can cause both hoop and axial stresses at the inner wall to be compressive, and the hoop compressive stress depth from the inner wall reaches 88 % of the pipe wall thickness and axial compressive stress depth reaches 78 % of the wall thickness.

Fatigue crack propagation characteristics of segmented egg-shaped pressure shells

This study focused on the fatigue crack propagation and fatigue life of an egg-shaped pressure shell fabricated by welding and hydroforming a six-segment frustum. First, the segmented egg-shaped pressure shell was designed, and the hydroforming was analysed by the finite element method (FEM). Moreover, the numerical simulation of the egg-shaped shell under uniform external pressure and welding residual stress was carried out, and the stress distribution at the weld was obtained. Second, the equivalent specimens were designed to have structures with maximum stress in the weld. Equivalent specimens with different initial crack shape ratios were tested, and the unified crack propagation rate model of 18Ni (250) was obtained by fitting the data. The fatigue life of the equivalent specimen was calculated by ABAQUS and FRANC3D software and compared with the test results. Finally, the crack propagation rate model was used to predict the fatigue life of the egg-shaped pressure shell. The results of this study provide a reference for prediction of fatigue damage and assessment of the safe operation of egg-shaped pressure shells.

Fracture failure analysis of a lightning rod on a substation frame considering residual thermal stress

The collapse of a typical lightning rod on a 500-kV high-voltage substation frame in central China is investigated to identify the mechanism of fracture. Comprehensive analyses are performed on the fracture morphology, metallurgical structure, chemical composition and mechanical properties of the materials at the fracture site. A finite element (FE) model of a typical lightning rod structure with an intersecting joint weld is developed and verified using experimental results. Based on the FE results and wind tunnel tests, the fatigue life is estimated for the lightning rod structure at the accident site considering residual stress. The results indicate that the fracture failure of the typical lightning rod structure is mainly caused by wind-induced fatigue damage in the weld area of the intersecting joint of the rod base and the frame beam. The welding residual stress has a severe impact on the fatigue life of the structure. Regardless of the welding residual stress, the actual fatigue life of the typical lightning rod structure under a long-term wind load is lower than the design service life. Therefore, complete analysis of the structure under complex wind-induced dynamic effects is needed in engineering design. Additionally, attention should be given to the quality control of the welding, and measures should be adopted to reduce residual stresses during manufacturing and installation.

Cyclic elastoplasticity and XFEM based fatigue life assessment of out-of-plane gusset welded joints

Conventional design methods for high-cycle fatigue failure of engineering components often assume a linear-elastic material behaviour. The different driving forces of crack initiation and propagation fail to be considered, resulting in less accurate predictions of fatigue life. To address this issue, the present study proposes a novel method to predict the fatigue life of out-of-plane gusset welded joints based on cyclic elastoplasticity and extended finite element method (XFEM). Incorporating the welding residual stress simulated by thermal–mechanical analysis, the cyclic stress–strain response of out-of-plane gusset welded joints was assessed by Fatigue SS (FSS) constitutive model. The crack initiation life was therefore predicted by the local strain approach considering the mean stress correction. Based on the converged cyclic stress–strain response, the crack propagation behaviour and life were predicted by XFEM in combination with Virtual Crack Closure Technique (VCCT). The influence of mean stress, mixed-mode crack and residual stress on crack initiation and propagation life was also investigated. The results show that the proposed method can predict the fatigue life of out-of-plane gusset welded joints under the pure tension loading with high accuracy against experimental results.

Experimental and Numerical Analysis of Residual Stresses in Similar and Dissimilar Welds of T91 and Super304H Steel Tubes

Experimental and Numerical Analysis of Residual Stresses in Similar and Dissimilar Welds of T91 and Super304H Steel Tubes

Study on Residual Stresses of 2219 Aluminum Alloy with TIG Welding and Its Reduction by Shot Peening

Large residual stress of 2219 aluminum alloy induced by Tungsten Inert Gas (TIG) welding decreases its service performances. Shot peening was adopted to decrease the residual stress of TIG welding. Numerical models of TIG welding and shot peening were established using the combined discrete and finite element methods (DEM–FEM). The results show that TIG welding induces tensile residual stress due to the heat exchange effect and the longitudinal stress is larger than that in the transverse direction. The maximum tensile stress occurs at a depth of 0.1 mm. The surface tensile stress changes to compressive stress after shot peening as the severe deformation induced by the shots changes the stress state of the plate. The maximum value of compressive stress (σm) and the peened depth with compressive stress (Z0) are adopted to describe the peening effect. The absolute value of σm increases with the increased peening speed and nozzle height. Mixed shots with a diameter of 0.8 mm and 1.2 mm induce larger value of σm than those with only a diameter of 1.2 mm. The value of Z0 increases with the ascending shots diameter and nozzle height, while it varies nonmonotonically with the peening speed. The effect of shot peening on the residual stress in TIG welding is discussed.