Welding Residual Stress Research Articles

Numerical Study on Welding Residual Stress and Microstructure in Gas Metal Arc Welding Square Tube–Plate Y-Shaped Joints

Welding residual stresses significantly influence the mechanical behavior of hollow section joints, especially in the pivotal connection zones of steel structures employed in construction. The research object of this study is the Q355 steel square tube–plate Y-joint welded using Gas Metal Arc Welding (GMAW) with CO2 Shielding. The thermodynamic sequence coupling method was employed to simulate the temperature field, microstructure distribution, and welding residual stresses in square tube–plate Y-joints. Based on the monitored temperature field data and the cross-sectional dimensions of the weld pool, this study calibrated the finite element model. Subsequently, the calibrated finite element model was employed to analyze the influence of microstructural phase transformations and welding sequences on the welding residual stresses in square tube–plate Y-joints. The research findings indicate that the peak transverse welding residual stresses in the branch pipes of the four joint zones were lower when considering the phase transformation effect than when not accounting for it in the calculations. There was no significant difference in the transverse and longitudinal welding residual stresses on the surface of branch pipes under the three welding sequences. However, there were certain differences in the microstructural content of the weld zones under the three welding sequences, with the martensite content in the third welding sequence being significantly lower than that in the other two sequences.

Effect of Laser Power on Weld Formability and Residual Stress of Unequal Thickness 410 Ferritic Stainless Steel/RCL540 Low-Carbon Alloy Steel.

In this paper, the butt joint of unequal thickness 410 ferritic stainless steel and RCL540 low-carbon alloy steel sheets are realized by laser welding. The effects of different laser powers on weld formability, mechanical properties, and residual stress in the welding process are investigated. It is observed that with increasing laser power, the heat accumulates at the bottom of the molten pool and weld metal, causing the ratios of upper and lower melt widths to decrease. The tensile test results show that all specimens fractured in the weak zone of the base metal on the stainless steel side at 10 mm from the weld seam. The residual stress distributions of the specimens are calculated using ABAQUS 2022 software and compared with the measurements of the blind-hole method. It is found that the stainless steel side produces tensile stresses, with the power increase offset by compressive stresses in the base metal. When the laser power is 1200 W, the welded joint has the best weld formability and mechanical properties and the least residual stress. The upper and lower melt width ratio is 1.17, the maximum microhardness of the weld metal is 374.7 HV, the maximum test force and tensile strength are 5617.5 N and 468.12 MPa, respectively, and the minimum values of the transverse and longitudinal stresses are -45.8 MPa and -106.4 MPa, respectively.

A parameterized modeling method for analyzing welding residual stress in orthotropic steel deck

This paper presents a new parameterized method for establishing OSD models and analyzing WRS, and two plugins are developed based on the graphical user interface (GUI) of Abaqus. This parameterized method addresses the extremely high cost of manual modeling of OSD in Abaqus. In the two presented plugins, the OSD dimensions and welds size, the material properties, the welding heating source, and the mesh properties are parameterized, and the OSD model can be created automatically by the plugins without users’ pre-processing operations in Abaqus, which significantly facilitates the OSD modeling and the WRS analysis. The plugins developed in this study can provide the WRS analysis in the OSD with any dimensions and welding technologies, and the applicability of the plugins is verified by the consistency between the simulated WRS analysis results by plugins and those reported in the literature.

Analyzing the Influence of Welding Process Selection on Residual Stresses in Tube-to-Tubesheet Welded Joints

Tube-to-tubesheet joints are used in the fabrication of shell and tube type heat exchangers, steam generators, boilers, condensers, and end shields of pressure tube type nuclear reactors like CANDU (Canada Deuterium Uranium) and PHWR (Pressurized Heavy Water Reactor). The weld joints connecting the tubes to the tubesheets are of prime importance as they have a direct impact on equipment safety. In the fabrication of these critical class-1 nuclear components, full penetration weld joints are used. Typically, these full penetration weld joints are created through multi-pass Tungsten Inert Gas (TIG) welding. However, more recent techniques, such as single-pass Electron Beam Welding (EBW) and Laser Beam Welding (LBW), have also been employed for this purpose. The fabrication time of these pieces of equipment containing full penetration weld joints can be drastically reduced if single-pass welding techniques are used compared to multi-pass welding techniques. However, the residual stresses developed in these joints due to the localized heat input and the substantial constraints of the tubesheet are unknown. Different welding processes, such as TIG welding, EBW, or LBW, can lead to varying levels of residual stresses in these joints, subsequently impacting their longevity. Weld residual stress plays a significant role in the initiation of failure modes of these tube-to-tubesheet welded joints, such as stress corrosion cracking, fatigue, and corrosion fatigue.This paper analyzes the residual stresses developed at the tube-to-tubesheet interface resulting from different welding techniques, such as multi-pass TIG welding and single-pass EBW/LBW. A comprehensive three-dimensional coupled thermo-mechanical finite element analysis is employed for this purpose. The findings reveal a significant difference, with single-pass EBW exhibiting up to 32% lower residual stresses compared to multi-pass TIG welding. Additionally, the Heat Affected Zone (HAZ) in EBW is approximately 50% smaller than in TIG welding, and the equivalent distortion in EBW is reduced by 90% compared to multi-pass TIG welding. In summary, this investigation concludes that single-pass EBW offers distinct advantages for tube-to-tubesheet weld joints, including reduced residual stresses, a smaller HAZ, and lower distortions.

Creep relaxation to relieve residual stress in girth-butt welded X80 pipelines: Simulation and experiment

The residual stress in girth-butt weld presents safety risks for large-diameter oil-gas pipelines, necessitating an in-depth investigation into the welding residual stress and the development of effective methods to mitigate these stresses, thereby enhancing structural integrity. In this work, a finite element girth-butt welding model was developed to predict the residual stress of X80 pipelines. The residual stress relief resulting from local post-weld heat treatment (PWHT) was simulated based on the Norton creep model applicable to X80 steel. The simulation results, encompassing the residual stress both before and after PWHT, were validated through blind-hole drilling measurements. The results demonstrate that the welding residual stresses across all orientations were significantly reduced following PWHT, with a maximum stress reduction of approximately 360 MPa. The primary mechanical mechanism for residual stress relief was identified as high-temperature creep, and it was concluded that the PWHT alleviated welding residual stress effectively when the heating temperature exceeded the creep activation temperature. The consistency between the finite element analysis results and the experimentally measured residual stresses affirms the validity and feasibility of the finite-element-based approach for predicting welding residual stresses.

Enhanced elastic stress solutions for junctions in various pipe bends under internal pressure and combined loading ([formula omitted] pipe bend, U-bend, double-bend pipe)

Piping systems in nuclear power plants normally operate under high pressure and high temperature. To efficiently manage space within these systems, pipe bends are extensively used. However, the welded joints connecting these pipes may be susceptible to flaws due to weld residual stress, transient loads, and operating environments. When flaws are present in such areas, analytical evaluation of flaws is to be carried out based on fracture mechanics parameters such as stress intensity factor. To calculate the stress intensity factor, distributions of the elastic stress are required. Therefore, this paper presents closed-form approximations of elastic stress in the junction between a pipe bend and a straight pipe under internal pressure. Review of the existing elastic stress solutions for estimating the stresses in pipe bends was carried out analyzing their limitations. Based on those limitations elastic stress solutions for thick to thin wall pipe bends were proposed and were validated against finite element (FE) analysis for thick-wall to thin-wall pipe bends under internal pressure and combined loading (i.e. internal pressure, in-plane bending, out-of-plane bending inflicted simultaneously). 90° pipe bend, U-bend and double-bend pipe configurations were considered and showed good agreement with the FE results exhibiting less than 5.8 % discrepancies. The accuracy of the elastic stress solutions for pipe bends provided in the existing code are summarized and validated in the appendix as well.

Numerical prediction and control of deformation and residual stress in double-sided arc welding of large pressure hull

Double-sided arc welding (DSAW), as an advanced connection method, has become a typical method for large pressure hull with thick plates. However, welding deformation and residual stress will seriously affect the dimensional deviation and fatigue life of the product. Therefore, it is a very important work to predict and control the welding deformation and residual stress. A novel dynamic heat distribution model considering the weave of welding torches is proposed to accurately predict DSAW deformation and residual stress in this paper. It is worth noting that this paper also puts forward a method to control the welding deformation and residual stress by flexible constraints of multi-point array, which makes the radial deformation less than 2 mm and the maximum axial stress is 423.98 MPa. This research provides a new idea for the accurate prediction and control of welding deformation and residual stress, which has great engineering significance.

Numerical and experimental studies on the effect of cryogenic treatment on welding residual stress of TIG welded EN8 steel plate

Most of the conventional welding process induces Welding Residual Stress (WRS), hydrogen embrittlement and distortions to welded components. The post-weld mechanical behaviour has an impact on both structural integrity and operational effectiveness of the welded component. Traditional Post Weld Heat Treatment (PWHT) is capable of relieving WRS to some extent. Based on recent research, Heat Treatment (HT) cycles are comprised of conventional HT and Cryogenic Treatment (CT) gives better fatigue life to welded components by redistributing the residual stress field. There is a need for further research to explore the impact of different parameters of CT affects the mechanical behaviour of welded specimens. In this study, numerical and experimental investigations are conducted to understand the impact of HT cycles comprised of austenitizing, quenching, CT and tempering process, over the TIG welded EN8 plates. Numerical model is developed for predicting the variation in WRS with each stage of HT cycles and observed a considerable redistribution of WRS after the completion of proposed HT cycle. Using the proposed HT cycle, the influence of different soaking periods of CT over the welded components are studied experimentally and shows that 36 hours soaking period have higher impact on the welded component’s mechanical behaviour.

Analysis of variables in finite element analysis for multi-pass welding in nuclear power plant components, part 1: Comprehensive study with experimental validation using scientific weld specimen

The influence of various parameters in welding simulations using finite element analysis (FEA) was investigated in this study. Welding experiments and finite element simulations were conducted to analyze residual stress and post-welding distortion. It was a specially designed V-groove specimen, filled with bead passes using Gas Tungsten Arc Welding (GTAW), that facilitated the measurement of distorted shapes and residual stress. Advanced measurement techniques, including three-dimensional laser scanning and the contour method, were used to capture detailed data on the welded specimen. Three different heat source models (body heat flux, temperature boundary, and Goldak's double-ellipsoidal model) were employed in the simulations, and their effect on residual stress distributions was analyzed. Additionally, the effects of hardening models, bead deposition methods, bead shape modeling, welding sequences, and lumping of weld passes on simulation were systematically analyzed. The findings suggest that a combined approach using different modeling techniques and careful calibration of parameters can enhance the reliability of simulations in predicting weld residual stress and distortions.

Prediction of dK/da effects on stress corrosion crack growth rate of irradiated stainless steels based on slip oxidation mechanism

This study developed a predicting method for the crack growth rate (CGR) of stress corrosion cracking (SCC) under varying stress intensity factor (K) conditions for irradiated stainless steel (SS). First, optimization of the Hashimoto-Koshiishi model equation for calculating CGR under varying dK/da conditions was carried out using the Rice, Dugan, and Sham (RDS) equation for the crack tip strain rate. Second, the model input coefficients were set to incorporate the effect of dK/da on SCC CGR to fit the experimental data. Finally, the effect of dK/da on the CGR for 3 dpa irradiated SS of a core shroud was evaluated taking into account the weld residual stress distribution. The model prediction showed that there was little effect on the CGR for the increasing and decreasing K regions in the plate thickness direction of the core shroud under boiling water reactor (BWR) normal water chemistry, but the effect was not negligible for the decreasing K region under BWR hydrogen water chemistry.

Experimental evaluation of multiple-component residual stress distribution in a dissimilar metal repair joint of ferritic/martensitic steel using the asymmetric-cut and the symmetric-cut contour method

A thick multi-pass butt-welded ferritic/martensitic steel (P91) joint is prepared and the local region of the weld is repaired with an ENiCrFe-3 nickel-based alloy using the manual metal arc welding method. The repair weld including part of the base metal is then subjected to ultrasonic impact treatment (UIT). A three-cut contour method, including two asymmetric cuts and one symmetric cut, is developed in the present study to obtain the two-dimensional residual stress distributions at different locations, and the stress release after multiple cuts is considered to get the original stress distribution before cuts. The measurement procedure is introduced in detail. The longitudinal stresses in the repair weld and the initial weld of the P91 steel joint, as well as the transverse stress at the weld center, are finally obtained. The effects of the dissimilar metal repair weld at the local region on the longitudinal and transverse welding residual stresses are investigated. In addition, the applicability of UIT to mitigate the surface stress in nickel-based alloy repair weld is analyzed. The results show that the transverse and longitudinal stresses in the nickel-based alloy repair weld are both tensile stresses, the maximum longitudinal stress is close to the yield strength of the B91 weld metal and occurs in the heat-affected zone of the repair weld located in the initial weld. Repair welding causes the internal transverse compressive stress region to be narrower than in the original weld. UIT can be used to introduce compressive stress to the surface layer of the nickel-based alloy repair weld.

Using Iterative Correction to Improve the Accuracy of the Blind-Hole Welding Residual Stress Test.

An iterative correction method for the stress release coefficient, leveraging numerical simulation, has been innovatively developed to address the significant error issues associated with the blind-hole method in high-stress residual stress testing of steel structures. This method effectively reduces measurement error in high residual stress regions through a discriminant iteration process. The finite element analysis technology was employed to accurately simulate the blind-hole method's test process, and additionally, Python was utilized for customizing the secondary development of ABAQUS software, thereby automating and optimizing the method. When compared with simulation and experimental data from the welding process, the efficiency, accuracy, and reliability of the correction method have been verified. The proposed method eliminates the need for tedious calibration experiments inherent in traditional methods, significantly enhancing the test's automation level and convergence speed, and ensuring measurement accuracy, which provides an innovative solution for the accurate evaluation of residual stress in steel structures.

An experimentally validated thermomechanical model for a parametric study on reducing residual stress in cast iron repair welding

Remarkable casting properties and superior mechanical characteristics of cast iron make it an ideal material for a wide range of industrial applications. However, the production of cast iron components may result in the formation of cracks and defects, posing a significant threat to their structural integrity. Repair welding is a promising solution to resolve cast iron production defects. However, repair welding cast iron components poses unique challenges that stem from residual stress (RS) formation and the possibility of cracking during the repair process. Moreover, research on cast iron repair is scarce. To overcome these challenges, this paper presents a thermo-mechanical model validated by experiments to reduce RS in cast iron repair welding through the optimization of welding parameters and weld sequences as well as the geometry of the repair area. An experimental bead-on-plate weld is set up in order to validate the developed thermo-mechanical model. The temperature distribution in the weld is measured using thermocouples placed around the weld line. An X-ray diffraction technique is used to measure the axial and transverse RS at different points around the weld line. The developed finite element model is employed to simulate the repair welding process and analyze the effect of inter-pass temperature, the number of welding passes, welding sequences, and groove geometry on the RS. The numerical approach applied in this study provides a framework for repair welding optimization of cast iron and other materials, fostering the development of more efficient and reliable repair methods for industrial applications.

Effects of ultrasonic vibration on residual stress distribution and local mechanical properties of AA6061/Ti6Al4V dissimilar joints by resistance spot welding

The joining of dissimilar titanium and aluminum alloys has potential applications in railway and aerospace industries, owing to substantial weight reduction and better economic viability. In this study, the residual stress distribution and local mechanical performance of ultrasonic-assisted resistance spot welding (UaRSW) welds were investigated. The welding current, welding time, and electrode force of the RSW process were set as 9.0 kA, 350 ms, and 1.0 kN respectively, and the frequency and power of ultrasonic vibration were 20 kHz and 800 W. The residual stress was evaluated by X-ray diffraction (XRD) method and numerical simulation, and these methods showed a reasonable match. There was tensile residual stress distributed on RSW welds and UaRSW welds, but the value of residual stress was reduced by about 30% at welding nugget and 20% at heat affected zone (HAZ) with the ultrasonic vibration, the reduction of residual stress in UaRSW welds was attributed to the more uniform temperature distribution and lower plastic deformation resistant of AA6061. The welding peak temperature was decreased from 1673.4 °C to 1584.2 °C with the ultrasonic vibration, resulted from the modified Al/Ti contact surface and reduced contact resistance. The miniature tensile test results showed the improvement of mechanical performance by ultrasonic vibration. The maximum load of welding nugget region increased from 19.6 N to 22.3 N, and the elongation obtained 10% increase. This hybrid welding technique shows a potential to improve the quality of welds with ensured efficiency, which is also simple to realize automation in the manufacturing industry.

Design of a multi-manipulator robot for relieving welding residual stress

Design of a multi-manipulator robot for relieving welding residual stress

The impact of welding residual stresses on fatigue crack growth behaviour in aluminium alloy plates: a numerical and experimental investigation

ABSTRACT This paper presents the findings of an investigation into fatigue crack growth in Compact Tension (CT) samples made of an aluminium alloy that contains welding residual stresses. The samples were welded using the TIG welding process, and the fatigue crack growth was measured through experimental means. To model the welding process and resulting residual stresses, as well as their impact on the rate of fatigue propagation, 3-D thermal-mechanical finite element (FE) analyses were conducted. The simulations revealed that the residual stresses induced by welding relaxed during fatigue loading. Both the experimental and FE results demonstrated similar relaxation behaviour of the specimens under fatigue loading. This study highlights the significant influence of residual stresses on the propagation of fatigue cracks in aluminium alloy specimens. By combining experiments and numerical simulations, a comprehensive understanding of how welding residual stresses evolve during fatigue loading and affect crack growth rates is achieved. The agreement between the experimental and FE models confirms the effectiveness of the finite element method in investigating the influence of residual stresses on the behaviour of fatigue crack propagation in structures fabricated through welding processes.

Experimental and Numerical Simulation Study on Residual Stress of Single-Sided Full-Penetration Welded Rib-to-Deck Joint of Orthotropic Steel Bridge Deck

Orthotropic steel bridge decks (OSDs) play a key role in long-span bridges, and full-penetration welding technology is crucial to improve their structural performance. This study proposes an innovative single-sided full-penetration welding rib-to-deck (RTD) joint technology. The accuracy of the numerical simulation in predicting the temperature field and stress field was verified by the combination of an experimental and numerical simulation, and the welding residual stress (WRS) of single-sided full-penetration welded RTD joints was analyzed. In addition, the effects of different welding parameters and RTD joint geometry on the WRS are discussed. The results show that the experimental results are consistent with the simulation results, indicating that the single-sided full-penetration welding technology without a groove is feasible. The WRS shows a peak tensile stress near the weld, which gradually decreases and transforms into compressive stress as the distance increases. In addition, the WRS of the roof surface and the U-rib surface increases slightly with the increase in the roof thickness and the welding speed. The research results are of great significance to optimize the welding process, improve the fatigue performance, and prolong the service life of steel bridge decks, providing a new technical method for bridge engineering.

Effect of welding residual stresses on the fatigue life assessment of welded connections

Welding residual stresses impose significant influences on the fatigue behavior and structural integrity of welded connections in various engineering applications. Understanding the effects of these residual stresses on fatigue life is crucial for ensuring the reliability and safety of welded structures. This paper proposes a damage-incorporated thermal–mechanical simulation method to examine the effect of welding residual stresses on the fatigue life prediction of welded plates and circular hollow section (CHS) X-joints. Compared to the experimental X-ray diffraction measurements and the fatigue tests, the predicted residual stresses and fatigue life demonstrate good agreement with experimental results for both high-cycle and low-cycle fatigue. The location of fatigue cracks resembles closely the estimation from a uniform fatigue damage indicator. The fatigue life prediction without incorporating the welding residual stresses does not affect significantly the life estimation for low-cycle fatigue but can cause substantial over-predictions for high-cycle fatigue.

Combined effects of local residual stresses, internal pores, and microstructures on the mechanical properties of laser-welded Ti-6Al-4V sheets

Laser-welded Ti-6Al-4 V is prone to severe residual stresses, microstructural variation, and structural defects which are known detrimental to the mechanical properties of weld joints. Residual stress removal is typically applied to weld joints for engineering purposes via heat treatment, in order to avoid premature failure and performance degradation. In the present work, we found that proper welding residual stresses in laser-welded Ti-6Al-4 V sheets can maintain better ductility during uniaxial tension, as opposed to the stress-relieved counterparts. A detailed experimental investigation has been performed on the deformation behaviours of Ti-6Al-4 V butt welds, including residual stress distribution characterizations by focused ion beam ring-coring coupled with digital image correlation (FIB-DIC), X-ray computerized tomography (CT) for internal voids, and in-situ DIC analysis of the subregional strain evolutions. It was found that the pores preferentially distributed near the fusion zone (FZ) boundary, where the compressive residual stress was up to -330 MPa. The removal of residual stress resulted in a changed failure initiation site from the base material to the FZ boundary, the former with ductile and the latter with brittle fracture characteristics under tensile deformation. The combined effects of residual stresses, microstructures, and internal pores on the mechanical responses are discussed in detail. This work highlights the importance of inevitable residual stress and pores in laser weld pieces, leading to key insights for post-welding treatment and service performance evaluations.

Experimental and numerical investigations on dynamic response of butt-welded plates subjected to blast load

Experimental and numerical investigations on the small-size butt-welded plates subjected to air blast loads were conducted to highlight the effect of welded joints on the blast proof structures. The inherent characteristics of welded joints, including geometry, mechanical properties and welding residual stress were evaluated and discussed in the computation of blast loading. The geometry shape was assessed through macrographic of the welded joints. The distribution of mechanical and thermal physics property was determined through basic experiments using the specimens extracted from different zones of a welded joint. Welding residual stress was calculated in a thermo-mechanical coupled model. Conventional Weapons Effects Program (CONWEP) is more economic but limited compared with Arbitrary-Lagrangian–Eulerian (ALE) method. ALE and CONWEP methods were applied to simulate the air blast load applied on the plates. Effectiveness and efficiency of the methods were discussed. The results of the two programs could both coincide well with the experiment measurements. The models under six conditions were calculated to uncouple and discuss the effect of material property distribution and welding residual stress on the dynamic response of the welded structure. Permanent deflections were considered to assess the capacity of welded structures. Welding residual stress fields and the local weak materials are advantageous to the bending deformation. The phenomenological expressions of permanent deflection across thickness under different welding conditions were established based on simulation results. The effect of aspect ratio of the welded structures was also be discussed.