Welded Structures Research Articles

Taguchi, Grey Relational Analysis, and ANOVA Optimization of TIG Welding Parameters to Maximize Mechanical Performance of Al-6061 T6 Alloy

This study presents a comprehensive investigation into optimizing Tungsten Inert Gas (TIG) welding parameters to enhance the mechanical performance of the widely used Al-6061 T6 alloy, specifically in a double V joint configuration with a plate thickness of 6 mm, for aerospace applications. The Taguchi method was employed to design the experiments, providing a robust framework for analyzing the influence of the electrical current, voltage, and gas flow rate on weld quality. Additionally, a Grey Relational Analysis (GRA) and an Analysis of Variance (ANOVA) were used to validate the optimal welding parameters and quantify the significance of each factor. The optimized parameters were determined to be an amperage of 180 A, a voltage of 18 V, and a gas flow rate of 10 L/min, resulting in significant improvements of up to 40% in tensile strength and 23% in hardness, demonstrating the effectiveness of the optimized conditions. The findings provide valuable insights into welding metallurgy, offering practical guidelines for enhancing high-performance welded joints in critical industrial applications. This study underscores the potential of combining Taguchi, GRA, and ANOVA methodologies to achieve superior mechanical properties and reliability in welded structures.

Enhancement on mechanical properties via phase separation induced by Cu-added high-entropy alloy fillers in metastable ferrous medium-entropy alloy welds

This study evaluated the weldability of metastable ferrous medium-entropy alloys using high-entropy alloy fillers with various Cu contents and elucidated the strengthening mechanisms at room and cryogenic temperatures by focusing on the formation of a Cu-rich phase (FCC2) in the weld metal (WM). The WM with higher Cu content exhibited more dual face-centered cubic (FCC) phases with dendrite-shaped compositional heterogeneity due to phase separation driven by higher mixing enthalpy. The FCC2 induced greater lattice distortion, resulting in higher nano-hardness and stronger solid-solution hardening. In addition, the increased presence of FCC2 in the WM promoted grain refinement and the formation of additional grain boundaries within individual grains. After cryogenic deformation, the base metal and heat-affected zone in transverse welds underwent martensitic transformation from metastable FCC (transformation-induced plasticity), while the diluted WMs exhibited twinning-induced plasticity because of their higher stacking fault energy (SFE) compared to the base metal. The combination of these deformation mechanisms enhanced the cryogenic tensile properties without compromising ductility. Furthermore, the cryogenic tensile properties of weld with higher Cu content were further improved due to the increased formation of deformation twins in the WM. The consumption of solute Cu to form more Cu-rich FCC2 resulted in compositional variations in the matrix (FCC1), leading to a further reduction in the SFE of FCC1 and the activation of additional twin formation. Additionally, FCC2 with a relatively higher SFE refined secondary twins as well as contributed to further dislocation accumulation. This study suggests that the formation of Cu-rich phase in the WM can enhance mechanical properties at both room and cryogenic temperatures and provides a valuable approach for the future development of welding materials to improve the mechanical properties of FCC-based welded structures.

Residual Fatigue Life Estimation of Damaged Welded Structures

This paper presents a finite element modeling procedure to determine of crack growth behaviour of butt welded joints under the subject of load for mode I. This paper presents a computation procedure to determine the ratio of fatigue crack growth in butt welded plates for mode I fracture mechanics loading conditions. The presence of residual stresses in welded structures can significantly affect the material’s resistance to fatigue under cyclic loading. The presence of tensile residual stresses adversely affects the fatigue crack growth rate increased it. Change of microstructure and hardening material as a result of the welding process also has a negative impact on the growth of the crack. Accurate prediction and reliable assessment of the residual stress are important for the structural integrity and residual life assessment of welded parts design. Although there are several techniques for the determination of residual stresses, the finite element method (FEM) is one of the most convenient and useful. This paper presents a finite element modeling procedure to determine of crack growth behaviour of butt welded joints under tensile load for mode I. Keywords: Welding, Residual stress, Residual life, Crack growth, FEM, Butt welded joint

Laser beam welding of T joints for aluminum–Copper–lithium aircraft panels: Effect of filler wire on recyclability and weldability

This study assessed the weldability and recyclability of four filler wires, two commercial (ER4047 and ER2319) and two experimental (ER2395 and J300), for laser beam welding of aluminum-Copper-lithium (Al–Cu–Li) aircraft panels. The results showed key differences in porosity and crack formation. The ER2319 filler exhibited a higher tendency for wormhole-type porosity compared to the others, which had similar pore area fractions. ER2395 displayed the longest crack length, likely due to its high lithium content. Chemical compatibility with the Al–Cu–Li base alloy AA2198 was confirmed for the ER2319, ER2395, and J300 filler wires, enabling 100% closed-loop recyclability without disassembly or alloy sorting. However, the high silicon content (around 11%) of ER4047 resulted in a recycled alloy that exceeded the allowable Si limit for AA2198, making it unsuitable for closed-loop recycling. Several end-of-life (EoL) strategies were explored for scrap fractions from ER4047-welded coupons. The 0C and 1C cutting strategies yielded hybrid fractions incompatible with AA2198 but suitable for the more Si-tolerant AA2196 alloy. The 3C strategy, involving weld seam separation before remelting, optimized recycling rates and minimized environmental impact. Additionally, a pre-scrap characterization method was developed to analyze weld seam composition, allowing for the prediction of recyclability issues and filler wire mass estimation in coupons where both the skin and stringer were made of the same alloy. This method provides a practical approach for evaluating welded structures in future recycling efforts.

Impact toughness behaviour of A516 GR. 60 steel welded joints

Impact fracture behaviour of welded joints made of A516 Gr. 60 is analysed as a commonly used carbon structural steel for welded structures. Impact testing on Charpy instrumented pendulum is performed using specimens with a notch at positions: the base metal (BM), heat-affected-zone (HAZ), and weld metal (WM). The total impact energy is presented as a sum of energies for crack initiation and crack propagation to make the analysis more sophisticated and comprehensive. The effect of temperature up to -60 °C was also analysed to prove the A516 Gr. 60 steel usability at subzero conditions.

Optimization of polypropylene high-strength injection molding welding and interface structure analysis

Secondary injection molding is an effective method for joining polymer parts, where the weld interface plays a critical role in the overall performance of the part. This study discusses the influence of injection molding parameters on the interface strength of polypropylene and polypropylene (PP-PP) secondary injection molding and analyzes the welding interface structure. The injection molding parameters for PP-PP were optimized using the Taguchi method and the signal-to-noise ratio (S/N). The optimal injection molding parameters were determined to be a mold temperature of 120°C, injection temperature of 350°C, and injection speed of 100 mm/s. The interface tensile strength was measured at 33.42 MPa, corresponding to 98.1% of the tensile strength of the base material. Among these parameters, mold temperature has the greatest influence on the strength of the welding interface. Secondly, polarizing microscopy, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) were employed to observe and analyze the crystal structure and fracture failure modes at the interface. The results indicate that elevated injection molding parameters promote the formation of crystal nuclei and spherulite growth at the secondary melt interface, with the spherulite size at the interface significantly affecting the interface strength. This study offers valuable reference for the welding of other polymers and fiber-reinforced materials.

A new analytical model for predicting the welding deformation of large welded plates with equivalent moments

The efficient prediction of welding deformation is important for the deviation control of large welded structures. In this paper, an analytical model is proposed to predict the welding deformation of large aluminium alloy plates. The welding-induced equivalent moments are calculated based on the inherent strain of a small-scale welded plate. The large welded plate is regarded as a corner-supported plate subjected to the equivalent moments. The welding deformation of the large welded plate is analytically derived by using the reciprocal theorem of work, and is validated by the experimental data. The effect of heterogeneous weld properties and plate dimensions on the welding deformation is quantitatively discussed. The proposed model can facilitate the deformation prediction of large welded structures.

Influence of the Pulse Mode of Manual Metal Arc Welding on Weldment Distortions.

As a result of the thermo-mechanical impact during welding, distortions are generated in welded structures. These distortions significantly influence the geometric and dimensional accuracy of welded structures, in many cases lowering their working characteristics and reliability. An optimal design for welded structures is a prerequisite for increased reliability and reduction in manufacturing cost, and such an optimal design can be achieved knowing the distortions in weldments. Despite the fact that pulsed metal inert gas welding and metal active gas welding have been broadly applied in the last few decades, nowadays, few manufacturers, for instance, Fronius, EWM, Redco, and Perfect Power Welders, offer such an option for manual arc welding. This work aims to determine the influence of the parameters of pulsed welding modes on distortions that are generated during manual arc welding. Two different inverter welding power sources were used, and the welding distortions were measured by 3D scanning. The results showed that the pulsed mode during manual arc welding led to a reduction in distortions compared to the conventional welding mode. The crucial part of the manual welding system proved to be the qualification and performance of the welder.

The Multi-Frame Imaging Detection of Ultrasonic Guided Waves in Welded Structural Plates Based on Arc Sparse Array with Left Rank

The imaging detection of ultrasonic guided waves in plates using arc sparse arrays is highly significant for weld scattering conditions. A novel approach for detecting welded plate structures using the left rank of ultrasonic guided waves in arc sparse arrays was proposed. The relationship between the receiving matrix and the left rank was analyzed, along with the connection between the arc sparse array with the left rank and the receiving aperture. The imaging mechanism of the ultrasonic guided waves in arc sparse arrays with left rank under weld scattering conditions was investigated. The results of imaging experiments demonstrated a downward trend in the gray and background gray of the multi-frame images. As the left rank reaches approximately 64% of the full rank, the slope of the image gray and background gray decreases gradually, leading to the appearance of an inflection point. With an increasing signal-to-noise ratio curve, the imaging improved during the multi-frame imaging process of ultrasonic guided waves for the arc sparse arrays with left rank under weld scattering conditions. This research showed that the multi-frame imaging of ultrasonic guided waves in welded structural plates using arc sparse arrays with left rank effectively characterized scattering information with millimeter-scale wavelength size. The experimental results validated the feasibility of the theoretical analysis. This research provides a crucial foundation for the further exploration and application of the multi-frame imaging detection of ultrasonic guided waves using irregular arrays in welded structural plates.

Применение высокопрочной стали для создания полувагонов повышенной грузоподъемности

Purpose: substantiation of the possibility to increase the load capacity of gondola cars using high-strength steel in the car body structure. Methods: gondola cars load capacity changing analysis. Numerical research of the effect of the steel yield strength value on the mass of the beam structure according to the criteria of strength and stiffness for a beam on two hinged supports operating in bending, and also according to the buckling criteria of a compressed beam. Gondola car body structure finite element analysis in order to confirm the strength and buckling parameters with the normative requirements. Results: the analysis of load capacity of universal fouraxle gondola cars built in the period from the beginning of production of the first Russian cars up to the present time was performed. Results of the analysis of the effect of steel yield strength on the mass of the structure according to the strength criteria and stiffness for a beam on two hinged supports operating in bending, and also according to the buckling criteria of a compressed beam was presented. High-strength steel technical requirements for welded structures of freight wagons is considered. Parameters for evaluating the suitability of rolled high-strength steel for freight wagon construction are given. The results of strength and stability analysis of the gondola car model 12-6744 with high-strength steel, which confirm the design compliance of the car in terms of normative parameters of strength and stability with the requirements of the existing standards are given. The gondola car model 12-6744 advantages are described, as well as the economic effect of its operation for the consignor. Practical importance: the possibility of using high-strength steel to increase the load capacity of gondola cars is substantiated. The gondola car model 12-6744 with high-strength steel was designed. Its advantages are given, and the economic effect of operating such a wagon for the consignor is shown.

Comparison of Fatigue Life and Crack initiation of T-Shaped CHS and SHS Welding Structures

Comparison of Fatigue Life and Crack initiation of T-Shaped CHS and SHS Welding Structures

Fatigue reliability analysis of bogie frames considering parameter uncertainty

With the increasing service life of bogie frames, the risk of fatigue failure becomes significant, making fatigue reliability analysis crucial for ensuring operational safety. However, accurately analyzing fatigue reliability presents a significant challenge with uncertain factors such as load fluctuations, unstable material shaping, and dimensional manufacturing deviations. To address this, this paper establishes a comprehensive active learning reliability framework based on surrogate models, enabling high-fidelity modeling and precise fatigue reliability analysis of welded frames under parameter uncertainty. The material utilization method was developed using APDL for secondary development to efficiently evaluate frame fatigue failure indicators. The effectiveness of this method was validated by combining the improved Goodman-Smith fatigue limit diagram and test bench fatigue tests, which helped identify the locations on the frame most prone to fatigue fractures. An Atom Search Optimization-BP Neural Network surrogate model was established with the objective of maximum material utilization, and the fatigue reliability of the bogie frame was obtained by combining the active learning function and the Monte Carlo method. The results show that the uncertainty design parameters greatly impact the fatigue reliability of critical welded structures. The proposed method improves the accuracy and efficiency of the fatigue reliability analysis of the bogie frame.

Adaptive scaled boundary finite element method for hydrogen assisted cracking with phase field model

This study introduces a numerical framework for analysing hydrogen assisted cracking, employing the scaled boundary finite element method. This is the first instance where the scaled boundary finite element method is employed to model hydrogen embrittlement. The phase field model is utilized to simulate defects, complemented by adaptive meshing using polytree mesh. The ability of the scaled boundary finite element method to treat polygonal elements assists in mitigating the problem of hanging nodes that arises from polytree decomposition. The adaptive framework is developed to predict crack propagation using an initial unstructured quadrilateral mesh generated from any commercial software. The hydrogen atom concentration depends on the hydrostatic stress gradient, which is calculated by interpolating nodal hydrostatic stress with scaled boundary shape functions and taking the gradient. A staggered solution approach is adopted to concurrently tackle hydrogen transport, elasticity, and phase field equations. The methodology is validated using Mode-I edge notch specimens and analysing crack propagation from corrosion pits, with results demonstrating close agreement with existing data. Subsequently, the framework is extended to address more intricate scenarios, such as crack propagation in X-shaped plates and hydrogen transmission in tanks. As the last example, more advanced image based fracture analysis of weld structure is investigated. This example studies the possibility of analysing the hydrogen diffusion directly from TEM imagery. Moreover, we investigate how hydrogen concentration influences structural failure.

Study on the Mechanical Response Behavior of X80 Pipeline Steel Welding Structure under Tensile Stress

Abstract The weld joint is composed of the weld area and the heat-affected area. The heterogeneity of the organizational structure will lead to local strain mismatch and affect its mechanical properties. This paper studies the strain distribution characteristics of the weld area and the heat-affected area under tensile stress, and reveals the respective strain response mechanism of the two regions. It is found that the weld area has lower yield strength and hardness, greater uniform elongation and strain hardening index. The plastic strain of the weld joint under tensile stress is highly heterogeneous, and the strain response mechanism is mainly based on the processing hardening effect. The strain response of the heat-affected area is weak and is affected by grain-oriented hardening. The research results provide a theoretical basis and experimental basis for the design of pipeline steel welding process and the safety evaluation under plastic deformation conditions.

Effect of Cr Element in Gas-Shielded Solid Wire for Oil and Gas Long-Distance Pipeline on Microstructure and Low Temperature Toughness of Weld.

In this paper, the influence of Cr element on the mechanical properties of welded joints of gas-shielded solid wire used in oil and gas long-distance pipelines was studied by means of tensile test, impact test, and hardness test, and the microstructure and crack propagation path of weld were characterized by means of an optical microscope, scanning electron microscope, and electron backscattering diffraction. The results show that with the addition of Cr, the strength and toughness of the weld are significantly improved, in which the tensile strength is increased from 607 MPa to 656 MPa, and the impact toughness is increased from 126.37 J to 223.79 J. The proportion of the ferrite side plate in the weld structure is reduced by about 20%, and the effective grain size of acicular ferrite is reduced by about 15%. The reason is that the addition of the Cr element improves the hardenability of the weld structure, inhibits the formation of the ferrite side plate, and promotes the effective refinement of acicular ferrite, which increases the proportion of high-angle grain boundaries in the weld, effectively hindering the crack propagation, improves the crack propagation work, and thus improves the strength and toughness of the weld.

Tuning residual stresses in welded structures by exploiting bio‐inspired suture interfaces

AbstractNature offers a valuable source of inspiration when designing optimized structures. For instance, when two or more shells are joined during growth processes, Nature prefers to exploit interlocking paradigms to enhance the strength of the bond—cranial sutures are one example. Mimicking this distinctive characteristic when welding thin metallic elements may offer some structural benefits. The present study theoretically investigates the possibility of mitigating the detrimental tensile residual stress that always originated by welding processes, by exploiting Computational Welding Mechanics. Specifically, two plates joined by laser welding following sinusoidal paths (i.e., wave‐like), alongside a linear one, will be studied and compared. Thanks to the distinctive temporal and spatial heat distributions of sinusoidal welding, both welding stress and strain develop in dissimilar ways compared with linear path welding—this is reflected to the resulting weldment distortion too. The results show that geometrically optimized sinusoidal welding can effectively reduce residual stress magnitudes compared with the linear configuration counterpart. The implications of these findings are of particular interest when dealing with the structural performance of welded structures, especially in fatigue contexts.

Alternatives to Reduce Hot Cracking Susceptibility of IN718 Casting Alloy Laser Beam Welds with a Mushroom Shape

Reducing hot cracking is essential for ensuring seamless production of nickel superalloys, which are extensively used in welded structures for aircraft engines. The prevalence of hot cracking in precipitation-strengthened alloy 718 is primarily governed by two factors: firstly, the chemical composition and the coarse microstructure formed during solidification, and secondly, the activation of hot cracking mechanisms, which is particularly critical in mushroom-shaped welding morphologies. In this study, different nickel-based superalloys welded using laser beam welding (LBW), more specifically bead on plate welding (BoP), specimens are compared. The cracking susceptibility of both wrought and two investment casting 718 alloys with tailored chemical compositions is examined through the application of both continuous and pulsed LBW. Additionally, various pre-weld treatments, including with and without Pre-HIP (hot isostatic pressing), are analyzed. The influences of chemical composition, LBW parameters and pre- and post-welding treatments on both internal and external cracks determined by conventional and advanced non-destructive tests are studied. A clear reduction of hot cracking susceptibility and overall welding quality improvement was observed in a tailored 718 alloy with relatively high Ni (55.6% wt) and Co (1.11% wt) contents.

Parametric characterization of the Christopher–James–Patterson model for crack propagation in welded zone of A7N01 Aluminum alloys

AbstractAluminum alloy is a widely used material in railway vehicle structures. In order to accurately analyze the crack propagation mechanism of Aluminum alloy welding structures and predict their crack propagation life, this study focuses on the A7N01 Aluminum alloy and proposes a full‐field strain solution method based on the least‐squares method. For the first time, digital image correlation (DIC) experimental measurements are combined with the finite element analysis method to determine the shape and size of the plastic zone at the crack tip of the compact tension (CT) specimen. And it also calculates the crack propagation driving force parameters of the Christopher–James–Patterson (CJP) model using traditional crack propagation driving parameters. The research results revealed that the plastic zone at the crack tip captured by DIC experiments is in good agreement with the finite element simulation results. Additionally, the crack growth rate curve of the A7N01 Aluminum alloy, fitted based on the CJP model, is insensitive to the stress ratio. The results offer an effective approach to utilizing the da/dN‐∆KCJP curve in analyzing A7N01 Aluminum alloy and welded structural failures, broadening the scope of engineering applications for the CJP model.

Experiments and modeling of microstructural and mechanical behaviors of laser-welded Ni-based superalloy at high temperatures

The performance of welded Ni-based superalloys at high temperatures is essential to be evaluated due to their particular service environment for aero-engines and high-speed aircrafts. The tensile properties and related microstructural evolutions such as the carbide precipitate and grain of a laser-welded Ni-based alloy were experimentally and numerically investigated at different temperatures (20, 300, 500, 800 °C). The results show that at room temperature, the strength of the Base Material (BM) was slightly smaller, with a difference of less than 1%, than the Welded Material (WM), which can be attributed to the more uniformly distributed needle-shaped carbide precipitates in the WM than those nonuniformly coarser spherical ones in the BM. While at 300 °C and 500 °C, the strength of WM decreased more obviously compared with that of BM due to the more apparent growth of grain: 13.52% loss in yield strength in WM alloys as compared with BM alloys at 300 °C, and 16.57% at 500 °C. At 800 °C, the strength of BM and WM both decreased to a similar level due to Dynamic Recrystallization (DRX). However, a much higher elongation was observed for the BM than WM (less than 50% of BM), which can be attributed to the enhanced dislocation accumulation capability of the large spherical carbides along grain boundaries on the fracture surface in BM. Furthermore, a unified model considering the welding effects on both microstructures (dislocation, carbides, and grain) and mechanical properties evolutions at different temperatures was developed and validated. Based on this model, the key temperature ranges (20–600 °C) where apparent weakening of strength and uniform plasticity occurs for welded structures were identified, providing a direct guidance for potential structure and process design.

Prediction of residual stresses in welded structures based on neural network: a review

Prediction of residual stresses in welded structures based on neural network: a review