Transverse Weld Research Articles

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.

Fatigue testing strategies for the X65 steel catenary riser with small‐scale specimens considering the effect of welding residual stress

AbstractTo accurately evaluate the fatigue performance of a full‐scale deep‐water steel catenary riser (SCR) using small‐size specimens, six fatigue testing strategies were explored, considering the effect of welding residual stress. Through a comparison with the full‐scale resonant bending fatigue testing results, the most equivalent strategy using small‐scale specimens was identified. The results indicate that the test strategies applying constant stress underestimated the fatigue life, compared with that of a full‐scale specimen; meanwhile, fatigue life values obtained from the low‐stress ratio testing strategy were higher, particularly in the low‐stress range region. Comparatively, the fatigue lives obtained for the 100 mm‐wide specimens without cutting were higher in the high‐stress range region. The variable‐applied mean stress strategy using the 25 mm‐wide welded joint specimen was the most suitable for equivalence with the full‐scale fatigue testing, with only a 9.7% difference in the fatigue life testing results. The difference between the applied mean stress and the actual transverse welding residual stress under various fatigue testing strategies is the key factor affecting the equivalence of the fatigue testing results.

PWHT influence on welding residual stress in 45 mm bridge steel butt-welded joint

To investigate the spatial distribution of welding residual stress (WRS) and effect of post welding heat treatment (PWHT) on WRS relaxation in the welded components of steel bridges, a 45 mm-thick Q345qD butt-welded specimen was manufactured. Experimental measurement and numerical simulation methods were employed to examine specimen surface and internal WRSs. The simulated results exhibited good agreement with the measured ones, confirming the rationality of the numerical simulation process. Subsequently, through the PWHT simulation in ABAQUS, the evolution of WRS during PWHT was comprehensively analyzed and the effect of PWHT parameters on the stress relaxation was studied. The measured and simulated results show that the longitudinal welding residual stresses (LWRSs) are tensile in the weld region and compressive away from the weld. High-value stresses are mainly concentrated on specimen surfaces and the mid-thickness. Transverse welding residual stresses (TWRSs) present multi-layered distribution, alternating between tension and compression within the weld region. WRS reduction mainly occurs during the heating stage of PWHT, with slight decrease during the holding stage and an increase during the cooling stage. Optimizing PWHT parameters, including temperature, and holding time, heating/cooling rates, proved effective in achieving substantial WRS relaxation.

Evaluation of the fatigue resistance of butt-welded joints in towers of wind turbines — a comparison of experimental studies with small scale and component tests as well as numerical based approaches with local concepts

Wind turbines must endure a high number of load cycles during their service lifetime. Therefore, the fatigue strength verification plays an important role. Butt-welded joints are one of the most common structural details in the tower structure of wind turbines. In general, the nominal stress method is used for their fatigue verification. The Eurocode 3 part 1–9 is the current design standard for this field of application and defines the fatigue resistance by pre-defined FAT-classes. This paper presents recent results of fatigue tests on small-scaled specimens and large components with transverse butt welds to discuss the validity of the FAT-class. In addition, results from numerical simulations for the verification with the effective notch stress and the crack propagation approach are used for comparison. For this purpose, macroscopic measurements of the weld seam geometry and a 3D scan were used for a realistic consideration of the notch effect in the simulation. Based on the consistency between the numerical results and the fatigue tests, the influence of the seam geometry on the fatigue resistance was worked out. Furthermore, a prediction of the fatigue strength of butt-welded joints with plate thicknesses up to 80 mm was carried out.

Numerical investigation of the influence of transverse welds on the strength of aluminum alloy I - shaped members – beams

The weldability of high strength aluminum alloys is an important consideration when designing aluminum structures. While these alloys do suffer significant strength loss in the weld heat affected zone (HAZ), available design codes are often overly conservative in their guidelines regarding the design of welded aluminum members. This paper presents a numerical investigation of the effect of reduced strength in the HAZ adjacent to a transverse weld in simply-supported aluminum alloy beams subject to concentrated end moments. Nonlinear finite element (FE) models were developed, validated, and applied in a parametric study of non-welded and transversely welded 6061-T6 flexural members with an I-shaped cross section. The FE model included initial geometric imperfections and material nonlinearities in both the HAZ and the base material. The parametric study examined 400 unique beam cases defined by the combination of four factors, including slenderness ratio or unbraced length, weld location along the beam span, post-yield material stiffness model, and loading case or resulting moment gradient. The FE results were subsequently compared with capacities predicted by the Aluminum Association’s Specification for Aluminum Structures, with proposed modifications to SAS also provided. A similar study on columns is presented in a companion paper within this issue.

Numerical investigation of the influence of transverse welds on the strength of aluminum alloy I-shaped members – Columns

This paper presents a numerical investigation, using finite element analysis, of the effects of transverse welds on the structural behavior of aluminum-alloy compression members. A non-linear finite element (FE) model was developed, and validated using experimental tests, to simulate the behavior of 6061-T6 aluminum-alloy columns with an I-shaped AW6×4.03 section geometry. The FE model included different material properties for the heat-affected zone (HAZ) that occurs in the proximity of the weld and the remaining base material, and incorporated both geometric and material nonlinearities. A parametric study of 80 columns with and without transverse welds was conducted, which investigated ten unbraced lengths, three weld centerline locations along the member length, and two types of post-yield material stiffness models, including elastic-perfectly plastic and strain hardening materials. The FE results provide clear evidence of the significance of the HAZ strength reduction on the load carrying capacity of welded aluminum-alloy columns. Numerical results were compared with those obtained using the provisions within the Aluminum Association’s Specification for Aluminum Structures, and they were used to develop proposed modifications to these provisions, which can remove the degree conservatism observed. A similar study on beams is presented in a companion paper.

EQUIPMENT FOR MECHANISING THE SUBMERGED ARC WELDING PROCESS

Flux welding is a notable, reliable, and adaptable method of combining metals among other welding techniques. Flux welding is an arc welding technique that employs a substance known as "flux" to shield the weld pool from any chemical reactions with atmospheric constituents while welding. Flux materials often comprise borax, hydrochloric acid, or zinc chloride. In the process of flux welding, a joint is covered with a layer of flux, or alternatively, a flux-coated or flux-cored electrode is employed. Upon the formation of the weld pool, the flux undergoes melting and adheres to the pool, thus safeguarding it against any potential reaction with air constituents. This manuscript describes equipment used in mechanized flux welding process in order to improve its performance. Lincoln Electric NA-3N submerged arc welding equipment on a universal lathe longitudinal carriage was designed. The equipment was mounted on a carriage with a maximum longitudinal travel of 2380 mm and a maximum transverse stroke of 410 mm. This carriage moves the welding equipment. The longitudinal advance allows longitudinal and transverse welding on this system.

Modeling the strength of aluminum extrusion transverse welds using the film theory of solid-state welding

Reducing production scrap is vital for decarbonizing the aluminum industry. In extrusion, the greatest source of scrap stems from removing profile sections containing transverse (charge) welds that are deemed too weak for their intended purpose. However, until now, there has been no predictive transverse weld strength model. This article establishes a transverse weld strength model as a function of billet properties and extrusion parameters. It extends the film theory of solid-state welding by enhancing Cooper and Allwood's plane strain model to consider non-plane strain deformations at the billet-billet interface. These enhancements are informed by analyzing oxide fragmentation patterns through shear lag modeling and microscopy of profiles extruded from anodized billets. Model predictions are assessed through shear tests on welds from single and two-piece billets, extruded into rod, bar, and multi-hollow profiles. The experiments reveal that negative surface expansions at the weld nose cause interface buckling and weaker welds, but both surface expansions and weld strengths increase with distance from the nose. In non-axisymmetric profiles, deformation conditions and strengths vary across, as well as along, the weld. Two-piece billet welds are longer but reach bulk strength long before weld termination. The model predicts these trends and shows that die pressures are sufficient for micro-extrusion of any exposed substrate through interface oxide cracks. This underscores the significance of interface strains in exposing substrate and determining the weld strength. The model can help increase process yields by determining minimum lengths of weak profile to scrap and aiding process optimization for increased weld strength.

Validation of a full scale CFD simulation of a self-propelled ship with measured hull roughness and effect of welding seams on hull resistance

This study presents the verification and validation of a full scale self-propulsion computational fluid dynamics (CFD) model including measured hull roughness and welding seams. The reference for validation is comprised of speed trial data from five sister ships. To ensure numerical accuracy, resistance and propeller open-water CFD simulations are verified and validated against model tests from two different towing tanks and discrepancies are found to be within the experimental uncertainty of model scale testing. The self-propulsion CFD results emphasise the necessity of measuring hull roughness for accurate performance calculations with discrepancies less than 3.4% on the delivered power relative to the fitted speed trial results. It is found that the empirical Townsin/Mosaad roughness formulation with measured average hull roughness, as recommended by ITTC, provides similar results, as modifying the wall functions using the Colebrook/Grigson roughness function. Homogeneous and heterogeneous roughness modelling methods are found to provide similar results for the studied ship. Modelling of the transverse welding seams on the hull surface is found to increase the total resistance by approximately 0.1% per seam, resulting in a total estimated increase in resistance of 1.5–1.8%. Finally, adding a fairing is found to significantly reduce the resistance penalty from welding seams.

Deformation behaviour of high‐strength steel welds using DIC

AbstractThis paper focuses on the deformation and strength behaviour of high‐strength steel (HSS) transverse fillet welds. The behaviour of six lap‐welded fillet joints made of high‐strength steels (HSSs) is investigated under tension load through experiment. Due to some weaknesses in the deformation measurement using traditional techniques, the digital image correlation technique (DIC) is used to measure the deformation of transverse fillet weld connections. The development of the deformation on the specimen throughout the loading process was analysed using DIC measurement. The deformation of transverse fillet lap‐welded connections from HSS is always less than 1 mm. The strength calculated from the weld's fracture surface area shows better results than the theoretical weld area because it provides the real strength of the weld. In most cases, the weld failure did not occur along the throat section. Moreover, it is confirmed that the analytical models offered by prEN 1993‐1‐8:2020 are conservative for all the specimens.

Fatigue behavior at flange thickness transitions with cope holes – design model for engineering practice

AbstractFlange thickness transitions are common constructional details in welded girders, such as crane runway girders or main girders of highway and railway bridges, to adapt the bending moment capacity of the girder to variable bending moment distributions. At these details the transverse butt weld is often decisive for the fatigue verification of the member. Based on comprehensive studies at Graz University of Technology, including also two fatigue tests, stress concentration factors for the fatigue verification of the butt welds at the girder flange were developed. However, due to the complex local stress fields at the flange thickness transition, cope holes were not included in these studies.Within a research cooperation of Graz University of Technology and Ruhr University Bochum, flange thickness transitions with cope holes are studied recently. Based on comprehensive numerical FE‐ calculations within the practically relevant geometric parameter range, the complex local stress fields near the cope hole are analyzed both, within the web and the flange plate. For validation of the FE‐model also strain measurements were carried out at large‐scale test girders. Applying the hot spot stress method, the decisive hot spots are determined, and a simplified design model is developed for an accurate prediction of these hot spot stresses.The paper presents this design model in detail and shows its accuracy ‐ compared to the FE‐results ‐ for a wide range of different geometrical conditions, as used in practice (e.g. variation of girder dimensions, flange thickness ratio, tapering to the outside and to the inside).Finally, also the results of full‐scale fatigue tests on two different welded girders with flange thickness transitions and cope holes are presented. This provides an accurate fatigue resistance for the proposed design model, based on the hot spot stress method.

Curvature Effects on Responses from Transverse Flaws in Piping Welds

In this paper, the practical limitations surrounding the probability of detection of transverse weld flaws are discussed when performing manual, skewed ultrasonic inspection of piping welds.

Prediction of transverse welding residual stress considering transverse and bending constraints in butt welding

Welding residual stress is generated by the thermal stress caused by rapid local heating and cooling during welding using a welding heat source. The distribution and size of the residual welding stress are affected by the joint type, welding conditions, constraints, etc., which also affect the fatigue, fracture, and buckling strengths. Therefore, because the magnitude and distribution of residual stress are very important for the safety evaluation of structures, guidelines for structural integrity evaluation suggest a method for deriving the welding residual stress. However, the welding residual stress presented in the guidelines is in a state without constraint; if a constraint exists, it is suggested to use the yield stress of the base material. This can lead to a very conservative design using the yield stress as the welding residual stress in the recent trend of the increasing use of high-strength steels with increased yield stress. Therefore, it is very important to investigate the relationship between constraint and residual stress during welding and to predict the residual stress according to the degree of constraint. In this study, the effects of member thickness, yield stress, lateral constraint, and bending constraint on the welding residual stress in butt welding were investigated, and predictive factors for welding residual stress were established. To this end, a thermal elastic–plastic analysis was performed by changing the thickness, yield strength, lateral constraint, and bending constraint size of the member. Subsequently, the analysis results were used to train a deep neural network (DNN) to predict the residual stress at the center of the weld and toe. In addition, the influence of input factors that affect the prediction accuracy during DNN learning was considered.

Investigation of mechanical and microstructural properties in joining dissimilar P355GH and stainless 316L steels by TIG welding process

In this study, the joining of high-temperature and pressure-resistant P355GH and austenitic stainless 316L steels by the Tungsten Inert Gas (TIG) welding method was investigated in terms of microstructure, mechanical properties, and weld efficiency. Comprehensive tests were carried out for the weld zone, heat-affected zones (HAZ), and base metals. In metallographic characterization research, optical microscope (OM), field emission scanning electron microscope (FESEM), energy dispersive X-ray spectroscopy (EDX/EDS), X-ray diffraction (XRD), and EBSD analyses were performed. Average grain size and IPF (Inverse Pole Figure) map were determined from the EBSD analysis of P355GH steel, welded zone, heat-affected zones (HAZ), and 316L steel. Vickers microhardness, bending, Charpy V-Notch impact, and tensile tests were performed to determine the mechanical properties of the welded joint and the base materials. According to the EBSD results, the average grain size of the P355GH base metal was 5.13 ± 1 μm, the average grain size of the 316L base metal was 16.33 ± 5 μm, and the average grain size of the weld center was 10.09 ± 6 μm. As a result of XRD analysis, the delta ferrite phase was determined in the microstructure of the welding region. The highest Vickers microhardness value was determined as 268 ± 15 HV at the weld center. In the tensile test results, the highest tensile strength observed in the transverse weld joint was 593.92 ± 06 MPa and rupture occurred in the 316L region. Bending forces were measured as 34.331 ± 10 kN and 32.966 ± 11 kN for transverse and longitudinal welded samples, respectively. The TIG welding process showed superior properties such as toughness, high plastic deformability, and high weld efficiency of 101.89% in the joining of 316L and P355GH materials.

Attributes of intergranular corrosion in AA6061-AA7075 double sided friction stir weld

The present study aims to observe the distinguishable progression of intergranular corrosion (IGC) in dissimilar AA6061-AA7075 double-sided friction stir welds (DSFSW) with and without employing secondary heating. Transverse weld specimen sectioned along the weld line, to separate advancing and retreating side, are electrochemically corroded. Secondary heating helps in impeding the most accelerated corrosion rate dominated over the AA7075 region by approximately 50%. The double stirred region remains least susceptible to corrosion due to the dissolution and break down of precipitates. The degree of homogenization during stirring of dissimilar alloy controls the degree of material depletion during corrosion, making intercalated structure unfavourable in terms of corrosion. IGC is found more aggressive in AA7075 structurally intercalated with AA6061 in stir zone. The coarse grain, wider precipitate free zones and continuity of the precipitates along grain boundary (GB) are interpreted as most influential factors. Additional/secondary heating resulted into retardation of IGC within the AA7075 but resulted continuous IGC along the GBs of AA6061. Low angle GBs appears more resistive against IGC as they allow the formation of lean precipitates on contrary to high angle GBs. Secondary heating boosts breakdown and dissolution of corrosion sensitive secondary phase particles reducing the intergranular corrosion tendency.

Analysis of the cause of destruction of the repair welded joint of a coiled tubing pipe

The article presents the results of studies of the destruction of coiled tubing after repair with the formation of a transverse weld using fusion welding without subsequent heat treatment. The design features of the repair welded joint are considered. A description of the operating conditions of the tubing is presented – ambient temperature, working fluid temperature, pressure, working fluid flow rate, number of round trips, as well as the characteristics of the working environment containing chloride salts, hydrochloric acid solution and gaseous nitrogen (with a high percentage oxygen content). To determine the cause of the failure and identify the corresponding defects, the method of visual-measuring control, determination and analysis of the results of measurements of the hardness and chemical composition of the material of the pipe and weld, mechanical tests were used. Particular attention was paid to fracture analysis, detection of defects in the form of pores, as well as metallographic studies of the microstructure of the welded joint. The ability to use manual arc welding for pipe repair in case of failure, as well as the identification of possible defects obtained during the repair and operation of coiled tubing, allows you to more quickly repair equipment and ensure an increase in its service life, eliminating unwanted downtime. The use of additional heat treatment and well-prepared surfaces for welding by cleaning and degreasing has a significant impact on the quality of the welded joint and leads to minimal formation of defects (pores, microcracks) that affect the further operation of the equipment as a whole, operated under tensile stress conditions during repeated static bending coiled tubing.

Experimental investigation of longitudinal and transverse welds during sideways extrusion

Differential velocity sideways extrusion (DVSE) is a novel process for fabricating curved profiles; welding quality during extrusion is an important issue for its industrial application. In this study, solid bars of aluminium alloy AA1070 were extruded from multiple billets at 500 °C using the novel process and the microstructure and mechanical properties of the extrudate were investigated. The weld formed between the billets includes longitudinal and transverse solid-state weld regions formed as the metal was extruded. The longitudinal welds have better mechanical properties than the transverse welds. Dynamic recrystallisation (DRX) occurred in areas with high dislocation density during the extrusion process and as a result, grains across the bonding interfaces of longitudinal welds have been formed, which improves the weld quality. In the areas with the transverse welds, macro weld defects can be observed at the weld front. With further progress of sideways extrusion, the defect density reduced and new grains formed at the bonding surface.

Numerical Modelling for Resistance of Welds in Steel Structures from High‐Strength Steel

AbstractThis paper presents the overview of the numerical design model of welds in structural steels using finite element shell element. Many researches are emerging in the field of advanced modelling of welds in steel connections by using finite element analysis in order to represent accurate geometry and stiffness of welds. There are several weld modelling techniques used for the computation of structural hot spot stresses in fatigue; oblique shell elements, rigid links and increased thickness techniques. The article intends to eliminate the gaps in knowledge about the numerical modelling of welds using shell elements to compute the direct resistance of the welds in structural steels.This paper focuses on the study of numerical design calculation for the resistance of the welds in steel structures from high‐strength steels. Inclined shell elements are used to represent geometry and the stiffness of the welds during modelling of transverse fillet welds in double lapped joint. Several design standards, and guidelines are widely used to check the resistance of the welds. To verify and validate the results of finite element models, analytical and experiment results from literature are used in the undermatching welding conditions. Based on numerical design calculations, a general approach of inclined shell element is recommended to represent the welds for computation of the direct resistance of the welds in steel structures.

Welding Mode Justification for a T-Joint

The paper proposes a method for calculating the mode of single-pass arc welding depending on the geometric parameters of the T-fillet weld. The authors reveal the dependence of the residual welding stress level on the welding mode, taking into account the stress concentration due to uneven heating and transverse weld shrinkage. Resulting from the comparison of three modes of single-pass arc welding (manual, mechanized, and automatic), the optimal modes that ensure the maximum lifetime of welded structures are determined.

Investigating the Residual Stresses During Angular Hard Facing of Mild Steel

In this study, permanent stress and deformations resulting from angular weld seams of the hardfacing process in flat plates were investigated. Temperature distributions, stress distributions, and permanent deformations were calculated in the study carried out with the finite element method. Experiments in the literature were used for validation. A very high agreement was obtained between the experimental and model results. Since only longitudinal and transverse welds were examined in previous studies, how angular welds will affect stress and deformations has been demonstrated in this study. In addition, the changes in stresses were calculated considering the cooling time after the welding process. Among the findings, it has been observed that long weld seams cause higher temperatures, deformations, and stresses. In addition, after cooling, it is seen that the stresses increase even more in terms of both tension and compression.