Welding Behavior Research Articles

Bead‐to‐Bead Analysis: Introducing an Innovative Methodology for Accelerated Quantitative Analysis of the Welding Behavior of Bead Foams

ABSTRACTPerformant lightweight components made of bead foams are essential for a sustainable transformation of industry in multiple areas. An in‐depth understanding of the welding process is key in reaching maximum mechanical properties. This study presents the novel methodology of Bead‐to‐Bead analysis, providing a superior way in directly and quantitatively evaluating the welding behavior of bead foams compared with current approaches. Individual beads of expanded polystyrene (EPS) and expanded thermoplastic polyurethane (ETPU) are welded in a rheometer at defined parameters. A subsequent tensile test in combination with the analysis of the welded surface allows the evaluation of shrinkage/softening of the beads during welding and their tensile strength. For EPS, softening of the amorphous material is observed at the beginning of glass transition (~95°C) in addition to an increased welding quality. Residual stresses in ETPU lead to initial shrinkage followed by softening above 140°C. Welding of ETPU starts at 100°C and reaches a maximum at 140°C. The subsequent thermal analysis of the welded beads show the importance of recrystallization processes during cooling due to the formation of new crystalline domains across the bead interfaces. In the absence of such domains, sufficient bonding between beads is not possible.

Identification of the Local Mechanical Behavior of FSW Welds Using the Inverse Method

Identification of the Local Mechanical Behavior of FSW Welds Using the Inverse Method

The Influence of Pigments on Ultrasonic Welding Behaviour of 3D Printed Components Using the Low Force Stereolithography Technology

The purpose of this paper is to study the strength characteristics of V4 resin components that are welded using ultrasonics. These components are created using the Low Force Stereolithography (LFS) technology, which reduces the printing forces for achieving the best possible finish. Welding components are 3D printed with a Form 3+ 3D printer, known for its high printing precision, employing a powerful laser and a spatial filter. Key characteristics of the ultrasonically welded components can be extracted, analysed, and summarized to provide guidance on the optimal resin selection.

Study on fracture behaviour of pipeline girth welds based on curved wide plate specimens: Experimental and numerical analysis

Understanding the fracture characteristics and strain capacity of pipelines with girth welds under external loads is crucial for evaluating pipeline safety. The use of curved wide plate (CWP) specimens closely resembling full-scale (FS) pipelines in geometry provides a more realistic representation of crack tip constraint states compared to small-size fracture toughness test specimens in laboratory settings. This study aims to investigate the ductile fracture characteristics of center cracks on the outer surface of girth welds in high-grade steel pipelines under external loads through large-scale CWP tensile tests and advanced numerical simulations. Tensile tests were conducted on CWP specimens using a kiloton tensile testing machine, with double crack opening displacement (COD) gauge monitoring crack mouth opening displacement (CMOD), and high-precision displacement sensors and strain gauges tracking deformation and strains at various positions. The study yielded significant experimental results, and a finite element (FE) model of the CWP was developed using the nonlinear finite element method (FEM) to validate the experimental data against simulation results. The FE model was then used to investigate the influence of material properties on crack propagation resistance and driving force curves. A method for determining the ultimate tensile strain capacity (UTSC) of pipelines based on actual material fracture toughness was proposed. This research contributes valuable experimental data for further exploration of fracture behaviour in large-scale pipeline girth welds and offers insights for safety evaluations of such welds.

Influence of friction stir welding on the localised corrosion behaviour of AA2060 T8E30 and AA2099 T83 Al-Li alloys

The effect of friction stir welding (FSW) on the microstructure and localised corrosion behaviour of the dissimilar weld of AA2099 T83 and AA2060 T8E30 alloys is investigated. FSW results in a drastic change in the microstructure thus altering their corrosion behaviour. The heat-affected region exhibits similar attack morphology to their respective base metal but is the most protected region. The stir zone (SZ) is the most susceptible to attack. During immersion of the entire weld, attack initiation occurs from the AA2060 SZ due to galvanic activity within the region caused by the overlap of the grains in the weld zone.

Study on Laser Transmission Welding Technology of TC4 Titanium Alloy and High-Borosilicate Glass.

As the demand for high-performance dissimilar material joining continues to increase in fields such as aerospace, biomedical engineering, and electronics, the welding technology of dissimilar materials has become a focus of research. However, due to the differences in material properties, particularly in the welding between metals and non-metals, numerous challenges arise. The formation and quality of the weld seam are strongly influenced by laser process parameters. In this study, successful welding of high-borosilicate glass to a TC4 titanium alloy, which was treated with high-temperature oxidation, was achieved using a millisecond pulsed laser. A series of process parameter comparison experiments were designed, and the laser welding behavior of the titanium alloy and glass under different process parameters was investigated using scanning electron microscopy (SEM) and a universal testing machine as the primary analysis and testing equipment. The results revealed that changes in process parameters significantly affect the energy input and accumulation during the welding process. The maximum joint strength of 60.67 N was obtained at a laser power of 180 W, a welding speed of 3 mm/s, a defocus distance of 0 mm, and a frequency of 10 Hz. Under the action of the laser, the two materials mixed and penetrated into the molten pool, thus achieving a connection. A phase, Ti5Si3, was detected at the fracture site, indicating that both mechanical bonding and chemical bonding reactions occurred between the high-borosilicate glass and the TC4 titanium alloy during the laser welding process.

Low cycle fatigue analysis of welded joints considering material cycling behavior

In order to describe the local cyclic behavior of welds during low cycle fatigue of welded structures, so as to effectively assess the low cycle fatigue of structures, a structural strain numerical method is proposed. Based on the plate and shell theory and elastic-plastic theory, the numerical method of equivalent structural strain parameter is derived, and the UMAT subroutine of ABAQUS software is used to solve the structural strain parameters directly. The fatigue life of the welded specimens of different materials was evaluated, and the predicted life was basically the same as the test life, among which the maximum error of the predicted life of structural steel was 12%, the maximum error of the predicted life of aluminum alloy was 15.7%, and the maximum error of the predicted life of titanium alloy was 7.3%. The fatigue data of different materials were analyzed by using the master E-N curve, and the results showed that all the evaluated fatigue data were distributed in the same narrow band of the master E-N curve, which proved the effectiveness of the equivalent structural strain range for the evaluation of low cycle fatigue of welded specimens.

Investigation of Irradiation Hardening and Effectiveness of Post-Irradiation Annealing on the Recovery of Tensile Properties of VVER-1000 Realistic Welds Irradiated in the LYRA-10 Experiment

Assessing the embrittlement and hardening of reactor pressure vessel steels is critical for the extension of the service lifetime of nuclear power plants. This paper summarises the tensile test results on the irradiation behaviour of realistic VVER-1000 welds from the STRUMAT-LTO project. The welds were irradiated at the HFR (Petten, the Netherlands) to a fluence of up to 1.087 × 1020 n·cm−2, and their irradiation hardening was studied by means of tensile testing. The four grades, with different Mn and Ni contents, show different hardening behaviours. The highest degree of irradiation hardening is observed for the weld that has the highest combined Ni + Mn content. The results show that there is a synergetic effect of Mn and Ni on the irradiation hardening behaviour of the VVER-1000 welds. Besides irradiation hardening, the effectiveness of post-irradiation annealing treatments on the recovery of the tensile properties is studied in the present work. Post-irradiation annealing treatments conducted at 418 °C and at 475 °C proved to be effective for three of the four investigated welds. For the realistic weld with the highest combined Ni + Mn, only the annealing at 475 °C led to the complete recovery of the tensile properties.

Investigation of the Fracture Behavior of High-Strength Structural Steel and Welds based on Micromechanical Models

Investigation of the Fracture Behavior of High-Strength Structural Steel and Welds based on Micromechanical Models

Experimental Investigation on Wear and Corrosion Behavior of Stir Cast Alloys and Friction Stir Cast Welds

Experimental Investigation on Wear and Corrosion Behavior of Stir Cast Alloys and Friction Stir Cast Welds

Influence of Imposed Strain on Weldability of Dievar Alloy.

The presented work is focused on the influence of imposed strain on the weldability of Dievar alloy. Two mechanisms affecting the microstructure and thus imparting changes in the mechanical properties were applied-heat treatment (hardening and tempering), and rotary swaging. The processed workpieces were further subjected to welding with various welding currents. In order to characterize the effects of welding on the microstructure, especially in the heat-affected zone, and determine material stability under elevated temperatures, samples for uniaxial hot compression testing at temperatures from 600 to 900 °C, optical and scanning electron microscopy, and microhardness testing were taken. The testing revealed that, although the rotary swaged and heat-treated samples featured comparable microhardness, the strength of the swaged material was approximately twice as high as that of the heat-treated one-specifically 1350 MPa. Furthermore, it was found that the rotary swaged sample exhibited favorable welding behavior when compared to the heat-treated one, when the higher welding current was applied.

Corrosion behavior of austenitic stainless steel and nickel-based welded joints in underwater wet welding

Marine structures such as ports, bridges, pipelines, vessels, and platforms are an essential part of modern infrastructure, where the use of higher-strength steel provides savings in logistics and construction. However, the repair of higher-strength steels can be challenging, especially underwater. Wet shielded metal arc welding is the most widely used and least expensive method for underwater welding repairs, but is very susceptible to hydrogen-induced cracking. Thus, researchers and welding engineers aim to reduce the amount of hydrogen in the weld material. Recent success has been achieved through the use of austenitic welding consumables, such as austenitic stainless steel and nickel-based electrodes. The use of these consumables drastically reduces the amount of diffusible hydrogen in the weld metal. However, these austenitic materials usually have different corrosion potential as compared to the structural steel the weld beads are applied to. This creates the risk of severe galvanic corrosion. In the presented study, the corrosion behavior of welds created with austenitic stainless steel and nickel-based electrodes were studied. Samples were aged for 1.5 years in the Baltic Sea. Simultaneously, the effectiveness of corrosion protection systems such as coating and Impressed Current Cathodic Protection (ICCP) were evaluated. Localized corrosion occurred in the heat-affected zone when austenitic electrodes were used in the corrosive environment. The localized corrosion depth after 1.5 years in the Baltic Sea and in the salt spray layer was approximately 250 µm and 390 µm, respectively. The ICCP system and the use of a coating were effective in preventing localized corrosion. The low pitting corrosion density of 2.5 × 103 m−2 corresponds to grade A1 according to the standard and was found to be negligible as compared to the localized corrosion in the heat-affect zone.

Experimental study and numerical simulation of cellular I-beam manufactured using refill friction stir spot welding technology

The paper presents analyses of thin-walled I-beams constructed from 6061-T6 aluminum alloy using refill friction stir spot welding (RFSSW). A parametrized finite element model of the reference cellular beam was developed, and the results from numerical simulations and experiments were compared. Subsequently, the validated numerical model was utilized to conduct an in-depth analysis of three additional beams featuring distinct cross-sections. To assess the weld behavior, experiments were conducted on samples composed of two sheets connected by two spot welds. The outcomes of these investigations underscore the suitability of RFSSW as a method for constructing thin-walled structures in civil engineering applications.

Investigation of Microstructure, Oxides, Cracks, and Mechanical Properties of Ti-4Al-2V Joints Prepared Using Underwater Wet Laser Welding.

Developing advanced underwater welding technology for titanium, which is the key structural material for underwater applications, is of great significance for the design, fabrication, and maintenance of submarine equipment. In this study, in order to investigate the underwater welding microstructure and mechanical properties of Ti-4Al-2V alloy, underwater wet laser welding was conducted on Ti-4Al-2V alloy using varying laser power. The microstructure and properties of the welding joints were characterized and analyzed. The microstructure of the heat-affected zone and fusion zone in the welding joints are not significantly different from those of welding in air, but a mixed oxide layer composed of Al2O3 and TiO2 is formed on the surface of the fusion zone. Due to internal stress, a large number of cracks initiate on the oxide layer and propagate to the joints. In the 4 kW and 5 kW joints, a penetrating crack formed due to the excessive accumulation of internal stress breaking up the α phase. The mechanical properties of the joints are significantly affected by the laser power. The tensile strength of the 3 kW and 4 kW joints is comparable to that of the base metal, which is about 600 MPa, while the 5 kW joint shows brittle fracture with no plastic deformation and 228 MPa strength. This research lays a solid foundation for understanding the underwater wet laser welding behavior of titanium alloys.

Underwater wet welding of high-strength low-alloy steel using self-shielded flux-cored wire with highly exothermic Al/CuO mixture

Underwater wet welding processes with minimal energy consumption and high efficiency is the future goal for researchers in the field. Al/CuO exothermic mixtures in consumables for land welding process can improve welding process stability and decrease the electrical dependence of the welding process. To confirm the beneficial effects of Al/CuO thermite and gain a better understanding of metallurgical properties of the thermite welds in underwater environment, this study investigated underwater wet self-shielded flux-cored arc welding (FCAW-S) of high-strength low-alloy steel with highly exothermic Al/CuO mixture. The effects of Al/CuO thermite on arc stability, weld metallurgical behavior and melting characteristics of flux-cored wire were clarified. The ratio of chemical heat in the flux to the heat required to melt welding wire increased from 4.7% to 38.4% with the addition of Al/CuO, potentially accelerating the melting of flux-cored wires. The arc stability with thermite addition was superior to that without the addition of thermite. The presence of copper as a result of metallurgical reactions had a substantial impact on metallurgical behavior of underwater wet welds. The ferrite weld was a non-equilibrium Cu supersaturated solid solution, which increased the microhardness and tensile strength of wet welds. The measured cooling time proved that the incorporation of Al/CuO had the capacity to reduce cooling rate. The incorporation of 50 wt% thermite yielded a 7.8% increase in welding process efficiency compared to the base formulation. Current work provided an important direction for the development of a chemically self-heating flux-cored wire.

The Influence of Groove Geometry on the Creep Fracture Behavior of Dissimilar Metal Welds between Ferritic Heat-Resistant Steels and Nickel-Based Alloys

This study investigates the influence of groove geometry on the high-temperature creep life and fracture behavior of Dissimilar Metal Welds (DMWs) between low-alloy steel 2.25Cr1Mo and austenitic stainless steel 347H using Inconel 82 nickel-based filling metal. This research aims to reveal the effect of groove geometry, especially the stepped groove, on creep crack propagation path and creep life, through a combined approach of finite element simulation considering stress triaxiality and experimental validation. The study reveals that the stepped groove alters the creep crack propagation path, enhancing the endurance life by deflecting cracks away from the weld/heat-affected zone (HAZ) interface and directing them into regions with higher creep resistance. The experimental results verify the simulation findings, revealing that the stepped groove joints exhibited longer creep life with changes in failure location and mechanism compared to the V-groove joints. However, it was found that the stepped groove intensified the stress concentration at the early creep stage. Thus, a good balance should be achieved between the negative (stress concentration at interface) and positive (changing crack paths) effects of the stepped groove to extend the creep life of DMWs.

Numerical assessment of welding sequences in single-pass pipe welding for minimizing residual stresses

This research aims to investigate the impact of different welding sequences in the circumferential direction on the welding process of 304 stainless steel pipes. A fully coupled transient thermo-mechanical simulation technique used to numerically replicate welding behaviour on a single-pass butt-welded cylinder joint with a nominal diameter of 300 mm and a thickness of 8.38 mm. Five distinct welding sequences are considered, and temperature profiles are measured at four circumferential positions. The findings reveal that the residual stresses within and near the weld deposit are indeed influenced by the chosen welding sequence. In case 1, the value of maximum temperature reached 1840 Degree K at point T4, achieving equilibrium between the flux input and heat losses during welding. In case 3, the maximum temperature value (1530 Degree K) is lower than all other cases due to better heat distribution. Respective to the temperature distribution the maximum stress values in case-1 to 5 are 211, 201, 138, 146, and 147 Mpa. Based on a comprehensive analysis of these factors, case 3 emerges as the preferable welding sequences for pipes falling in the NPS 10 to NPS 24 size category.

The prediction of residual stress of welding process based on deep neural network

The welding process has been an efficient method for producing essential and complex manufacturing parts in various industrial design fields. The post-weld residual stress can have detrimental effects on welded components. Therefore, systematic studies of residual stress are essential for evaluating welding behaviors and mechanisms in welded structures. They can provide a valuable reference and optimization for addressing residual stress relief. Numerical finite element analyses based on thermal-mechanical models offer a comprehensive approach to simulate real welding, providing a reliable means to determine and quantify the distribution of residual stress based on welding parameters and material properties. Furthermore, the finite element analysis is capable of generating adequate and dependable datasets in relation to the classical experiment. However, the finite element simulation is not considered an efficient method for predicting the magnitude and distortion of residual stress due to its high computational cost. A deep learning framework with powerful automatic learning abilities could potentially be used as an alternative method to efficiently predict residual stress. The purpose of the current study is to propose an innovative modeling approach for accurately and effectively predicting residual stress. A deep network model with Convolutional Neural Network using Adam optimization is integrated with numerical finite element analyses of a single-pass beam weld in SUS304 stainless steel. Finite element analysis is used to generate extensive residual stress datasets, which are partly used to train the deep network model and partly used for model validation. The deep network model aligns closely with the finite element analysis results, with a root-mean-square error (RMSE) of less than 12, an absolute fraction of variation (R2) of greater than 0.95, a mean absolute error (MAE) of less than 6.8 and a mean absolute percentage error (MAPE) of less than 1.1. Furthermore, this study highlights the potential advantage of using a deep network model with strong memory capabilities to directly predict residual stress for identical structural components and welding processes.

Comparative Analysis and Weld Behaviour of Mg-AZ31 and AL2024 with Various Profile Pin by Using FSW Process

Comparative Analysis and Weld Behaviour of Mg-AZ31 and AL2024 with Various Profile Pin by Using FSW Process

Penetration depth, phase balance and corrosion behaviour in activated TIG welding of UNS S32205

The aim of this research is to investigate the impact of a flux containing 80% TiO2 and 20% CeO2, under protective atmosphere (100% Ar, 98% Ar-2% N2, and 95% Ar + 5% N2) on penetration depth, phase equilibrium, and corrosion behaviour of autogenous A-TIG welds generated at constant current density. The reason for choosing cerium in the flux composition and nitrogen in the shielding gas is their effect on the phase balance of austenite and ferrite in this alloy. Metallography, ferritoscopy, and potentiometry were employed in the examination of the welds. The use of a two-component flux increased the penetration depth in TIG welding by up to 87%. Adding 2% and 5% nitrogen gas to the shielding gas in active TIG welding further increased the penetration depth to 117% and 130%, respectively. The results of ferritoscopic analysis reported the amount of austenite in the base metal and conventional TIG weld as 48% and 32%, respectively. However, the use of two-component flux increased the amount of austenite in the weld metal to 39%. Additionally, the addition of 2% and 5% nitrogen to the shielding gas in active TIG welding increased the amount of austenite in the weld metals to 60% and 76.6%, respectively. According to cyclic potentiodynamic polarization studies, active TIG welding with different nitrogen gas concentrations showed improved general and pitting corrosion properties in weld metals compared to conventional TIG welding. Consequently, weld metal resulting from active TIG welding with 2% nitrogen gas exhibited corrosion properties almost identical to that of the base metal.