Search Results (300)

The objective of this work was to investigate the effect of a special activating component, under the ZB-3 brand, on the welding and technological properties of a welding electrode when incorporated into the coating of a rutile welding electrode. Pulsed radiation activation was used to produce the nanostructured activating component ZB-3. The results showed the beneficial effect of the electrode doped with ZB-3 on the formation of welding beads. At the same time, an improvement in the quality of weld formation is observed with a ZB-3 activator content of up to 8%. The qualities of the weld formation were significantly improved. Also, an increase in the breaking length of the electrode arc by more than 10% was established with a ZB-3 activator content of up to 2%, and the depth of penetration of the welded metal increased to 40%. Full article

Damage is inevitably induced in titanium alloy laser-welded (LW) joints after prolonged service, making weld repair an economical and effective restoration method. This study employed gas tungsten arc welding (GTAW) to repair pre-damaged TC4 LW joints, with a systematic investigation on the microstructural and mechanical properties of the repaired joints. The results indicate that both the LW and the GTAW-repaired (GTAW-R) joints exhibit acicular α′ martensite in the fusion zone (FZ). However, the maximum length and width of the α′ phase in the FZ of the GTAW-R joint are 67% and 78% larger than those in the LW joint, respectively. The heat-affected zone (HAZ) of both types of joints comprises α′, α, and β phases. Similarly, due to the higher heat input in GTAW, the α′ phase in the HAZ of the GTAW-R joint is coarser. Differences in acicular martensite size result in an average microhardness of 356.3 HV in the FZ of the GTAW-R joint, which is 15.2 HV lower than that of the LW joint. The higher heat input of GTAW leads to a prolonged duration at elevated temperatures in the HAZ, promoting the formation of acicular α′ phase and, consequently, a slightly higher microhardness compared to the HAZ of the LW joint. The average tensile strength of the GTAW-R joint is 1032 MPa, equivalent to 98.4% of the LW joint strength (1049 MPa) and 96.8% of the BM strength (1066 MPa). Tensile fracture in the LW joint occurs in the BM region, whereas the coarser microstructure in the repair weld leads to fracture in the FZ for the GTAW-R joint. This study demonstrates that when the damage length in an LW joint is less than 20%, GTAW repair can effectively restore the joint strength. Full article

Wire and arc additive manufacturing is a promising technology for fabricating large and complex metallic components. Wire arc methods, like MIG and MAG, use an electric arc to melt and deposit metal wire layer-by-layer. The improvement of the surface depends on the multi-bead overlapping model. However, the high quality of multi-layer deposits is reduced by structural irregularities, such as geometric defects, poor fusion, and reduced mechanical properties of the weld bead. The analysis of a single weld bead that solidifies on a base material can be carried out to improve the geometry of the microstructure, to improve the mechanical properties, and to understand the relationship between welding parameters and the bead dimensions. In the present study, current metal welding technologies and strategies in wire-arc additive manufacturing were discussed, and different weld bead geometries using BÖHLER SG2 solid wire were realized, varying the robot’s trajectory length and welding speed. The computational models are proposed to create a dependence between the controllable welding input parameters and resulting geometrical weld bead outputs (width, height, length, and radius) for prediction and optimization. These models, using techniques such as support vector machines and artificial neural networks, can be a good tool for controlling quality by understanding these input–output relationships. However, the SVM has revealed a superior performance based on metrics for the nonlinear and intricate relationships between the geometrical weld beads and welding parameters. Full article

This study investigates the joint characteristics of a 60-layered copper foil stack using linear vibration ultrasonic welding for lithium-ion pouch cell applications. With increasing demand for high-capacity electric vehicle batteries, ensuring the reliability of multilayer electrode joints is essential. Experiments were conducted by varying vibrational amplitude, welding time, and clamping pressure. Weld quality was analyzed based on indentation profiles, joint strength, and failure modes. Results revealed that optimal welding energy (500–900 J) produced well-formed joints without surface cracks or tearing. Excessive welding energy (>900 J) led to material thinning and interfacial failure. The maximum T-peel peak load of 138.7 N was obtained at the 30th joining interface under 25 µm amplitude, 0.8 s welding time, and 1.5 bar clamping pressure. Interface-dependent optimum conditions were observed, reflecting thickness–direction variations in deformation and bonding within the 60-layer stack. Indentation length and depth correlated linearly with welding energy. Failure modes transitioned from no adhesion to tearing and button-pull types. The findings provide guidelines for optimizing welding parameters for high-quality multilayer foil joints in battery manufacturing. Full article

Currently, the non-uniformity of girth weld positions makes their limit state a crucial determinant of pipeline safety. The design method based on the limit state is pivotal in ensuring the integrity and reliability of the pipeline system. Challenges often emerge when determining the limit states of girth welds using semi-empirical formula methods, primarily due to difficulties in accurately identifying influential factors. The quantitative impact of each influence parameter on the crack driving force and the results determined by the semi-empirical formula remain unclear. This study utilizes numerical simulation methods to systematically analyze the quantitative sensitivity laws of critical factors such as crack depth on the crack driving force to address this challenge. The findings revealed that the strength matching coefficient, crack depth, and misalignment are the most significant factors influencing the crack driving force, followed by crack length, softening rate, yield-to-strength ratio, internal pressure, and wall thickness. The effects of tensile strength and outer diameter are relatively minor. A comprehensive database of crack driving forces is constructed using a parameter matrix approach. Combined with the LightGBM machine learning algorithm, a full-scale prediction model for the strain capacity of pipeline girth welds is developed. Predictions for 18 sets of wide-plate test results from the literature confirm the high accuracy of the prediction model, with a prediction accuracy of 6.48%. This research provides a robust reference for accurately determining the limit state of pipeline girth welds and effectively meets the demands of rapidly advancing welding technologies and increasingly complex service environments. Full article

Hot cracking in fully austenitic stainless steel welds is mainly caused by plastic strain accumulated while the weld cools through the brittle temperature range (BTR). This study proposes a simple mechanical model to estimate the plastic strain increment in the BTR and to clarify the effects of heat input and plate size (thickness and width). In the model, the BTR plastic strain increment is expressed as the sum of three terms: thermal contraction strain, bending strain due to a non-uniform temperature field, and an additional term caused by external restraint. Hot cracking is judged by whether the BTR plastic strain increment exceeds the critical strain. The model is applied to a restrained plate hot cracking test and a side-bead cracking test. For the side-bead test, we formulate the crack-driving bending moment per unit weld length and derive a simple relation between crack-tip curvature and local plate width. Using this relation, the critical-strain criterion is converted into a critical curvature. The critical curvature provides a practical index to compare cracking sensitivity for different geometries and heat inputs in welded structures. Full article

Sequential ultrasonic spot welding is an interesting joining method for overlapping thermoplastic composite structures. In the framework of the EU Clean Aviation Multi-functional Fuselage Demonstrator (MFFD) and the lower shell SmarT multifunctional and INteGrated TP fuselage (STUNNING) projects, SAM XL and TU Delft Aerospace Engineering collaboratively developed and demonstrated a robot-based sequential ultrasonic spot welding process for the sub-assembly of structural frames and clips in a fuselage section demonstrator. This full-scale thermoplastic composite fuselage section demonstrator, which was recently awarded the 2025 JEC Innovation award, measures 8.0 m in length and 4.0 m in diameter. Our robot-based sequential ultrasonic spot welding technology played an important role in ensuring the joining of structural clips and frames in the stiffened fuselage skin of the demonstrator, through the use of more than 1600 spot welded joints with an average welding time of approximately 10 s per spot, thereby significantly reducing cycle times as compared to traditional joining methods such as fastening or riveting. This paper provides a comprehensive overview of the technology development process and highlights the results achieved during the sub-assembly of the demonstrator, as well as the challenges encountered. Full article

To address challenges in weld recognition during vacuum electron beam welding caused by dark environments and metal reflections, this study proposes an improved hybrid algorithm combining YOLOv11-seg with adaptive Canny edge detection. By incorporating the UFO-ViT attention mechanism and optimizing the network architecture with the EIoU loss function, along with adaptive threshold setting for the Canny operator using the Otsu method, the recognition performance under complex conditions is significantly enhanced. Experimental results demonstrate that the optimized model achieves an average precision (mAP) of 77.4%, representing a 9-percentage-point improvement over the baseline YOLOv11-seg. The system operates at 20 frames per second (FPS), meeting real-time requirements, with the generated welding trajectories showing an average length deviation of less than 3 mm from actual welds. This approach provides an effective pre-weld visual guidance solution, which is a critical step towards the automation of electron beam welding. Full article

Friction stir welding (FSW) was employed to achieve a reliable joining of 2 mm thick dissimilar metals, 6061 aluminum alloy and AZ31B magnesium alloy. This study revealed the evolution of interfacial interlocking features and their impact on the mechanical properties of the joints under different welding speeds (25–35 mm/min). The results indicate that the Al/Mg FSW joint interface exhibits a strip-like interlaced structure, the morphological characteristics of which are closely related to the welding speed. For quantitative analysis, the ratio of interlocking length to plate thickness (embedding ratio) was used as a quantitative indicator of the structural interlocking feature. As the welding speed increased from 25 mm/min to 35 mm/min, the embedding ratio decreased from 13.2 to 7.9, and the average thickness of the intermetallic compound (IMC) layer decreased from 2.71 μm to 2.19 μm. Transmission Electron Microscopy (TEM) results confirmed that the Al/Mg FSW joint interface consists of a bilayer of IMCs, specifically Al₃Mg₂ and Al₁₂Mg₁₇, with thicknesses of 220 nm and 470 nm, respectively. Tensile testing of joints with different embedding ratios demonstrated that the tensile strength of the welded joint exhibits a positive correlation with the embedding ratio, reaching a maximum of 178 MPa. Full article

This study proposes a cylindrical high-temperature-resistant fiber-optic composite sensor based on the EFPI-FBG hybrid structure for simultaneous temperature and pressure measurement, addressing the demand for high-performance monitoring in harsh environments. The sensor’s core consists of a cylindrical pressure chamber, a metal substrate, and an EFPI-FBG sensing structure fixed via resistance welding and high-temperature ceramic adhesive. The cylindrical pressure chamber converts pressure into axial deformation to modulate the EFPI cavity length, while the FBG with one end floating is exclusively used for temperature compensation, avoiding pressure interference. The EFPI cavity length exhibits a linear relationship with pressure, achieving a sensitivity of 0.171 μm/MPa and a linear correlation coefficient of 0.9986. Stable operation up to 600 °C and 20 MPa is demonstrated, with a decoupling matrix enabling accurate dual-parameter sensing. Full article

With the advancement of welding technology, the demand for 70S-6 welding wire steel has steadily increased in industries such as construction, automotive, pressure vessels, and line pipe manufacturing. To optimize the production process of the target material, this study utilized the finite-element software ABAQUS to numerically simulate the multi-pass finish rolling process of 70S-6 welding wire steel. The study investigates the effects of the key rolling parameters—pass distribution (8/10/12 passes), finish rolling temperature (860/880/900 °C), and rolling speed (0.5 Vp/1.0 Vp/1.5 Vp, here Vp denotes the reference industrial rolling speed) on the rolling force, temperature field, and equivalent stress/strain during finish rolling. The results show that the increased number of passes homogenizes deformation, reduces local stress concentration and enhances mechanical properties. Specifically, 12 passes reduce the peak rolling force from 250,972 N to 208,124 N, significantly enhancing stress and temperature uniformity across the section. Increasing the finish rolling temperature lowers the pass-averaged flow stress and attenuates rolling-force fluctuations. At 880 °C, the simulated core–surface temperature gradient is minimal (50 °C), whereas at 900 °C the gradient increases (80 °C) but the rolling-force histories exhibit a lower peak level and smaller low-frequency oscillations; thus 880 °C is preferable when through-thickness thermal uniformity is targeted, while 900 °C is more suitable when a smoother load response is required. Increasing the finish rolling speed from 0.5 Vp to 1.5 Vp reduces the peak rolling force from 233,165 N to 183,665 N and significantly damps low-frequency load oscillations. However, it concurrently intensifies stress localization at the outer-surface tracking points P3/P4, which are in direct contact with the rolls, where the local equivalent stress approaches 523 MPa, even though the overall strain distribution along the bar length becomes more uniform. Overall, the optimal processing window is identified as a 12-pass schedule, a finish rolling temperature of 880–900 °C, and a rolling speed of 1.0–1.5 Vp, which can improve both rolling quality and temperature and stress and strain uniformity. Full article

A batch of drill pipe joints in a well cracked and failed due to hardbanding. In this study, various experiments were conducted to analyze the reasons for cracking failure, including data verification, macroscopic morphology analysis, mechanical properties, microstructure analysis, and micro-Vickers hardness of cracked areas, as well as macroscopic, metallographic, and energy spectrum analysis of the fracture surface after opening the cracked area. The results indicated that (1) the chemical composition, tensile strength, Charpy impact test, and Brinell hardness results of the joint met the requirements of the order technical conditions. (2) The hardbanding in the cracked area had multiple pores and cracks on its outer surface and inside. The maximum diameter of the internal porosity was about 3.4 mm, and the length of the internal crack was about 1 mm. (3) The main reason for the cracking of a batch of drill pipe joints due to hardbanding is a quality problem of the secondary repair welding of the hardbanding. The cracks in the failed drill pipe originated from the porosity and cracks in the hardbanding of the drill pipe box joint. Under the influence of alternating stress and high-pressure mud erosion underground, the cracks rapidly extended to the inner wall, and the porosity in the hardbanding accelerated crack propagation, ultimately causing the drill pipe to crack and fail. Full article

A weak-axis moment connection incorporating a double reduced beam section and a box-reinforced panel zone (WDRBS) is introduced for hot-rolled H-shaped columns. The configuration is intended to shift inelastic demand away from the column face and to constrain weak-axis panel-zone distortion. A series of finite element models is established and calibrated to examine the cyclic response of this connection type. By varying the geometric parameters of the second reduction zone, a closed-form expression for determining its cutting depth (c₂) is formulated, allowing both reduced regions to yield concurrently, i.e., the Optimum State. The numerical investigation demonstrates that connections designed according to this equation exhibit stable hysteresis, limited weld-adjacent plastic ll rightstrain, and sufficient deformation and energy-dissipation capacities. All specimens exhibit plastic rotations greater than 0.03 rad, ductility ratios greater than 3.0, and equivalent viscous damping ratios greater than 0.3. To facilitate engineering implementation using common hot-rolled sections, a simplified method is further proposed to approximate the admissible range of c₂ with practical accuracy. While the length of the second reduction region has only a modest influence on peak strength (approximately 1.5–6%), it markedly affects the failure mechanism and plastic-hinge distribution. A stepwise design procedure for WDRBS connections is accordingly recommended. The study does not consider composite-slab interaction or gravity-load effects, and the findings—based solely on finite element simulations—require future verification through full-scale experimental testing. Full article

This article presents the results of research on the possibility of extruding oxygen-free copper pipes in bridge dies. The possibility of continuous production of a finished product of any length with a uniformly deformed wall was analysed. One of the most important elements of the work was to determine the shape of the tool (die and bridge) that would allow durable connection of the material. Numerical studies conducted using the commercial computer programme FORGE^®NxT 2.1, including analysis of the distribution of material temperature and hydrostatic pressure in the welding zone of the bridge die affecting the copper joint during the manufacture of tubular profiles, confirmed the validity of the research issue. The results of the numerical studies were supplemented by laboratory tests, confirming the accuracy of the selected variant of the finished product manufacturing process. The process of bonding under conditions of two-part material compression was used for physical modelling of copper welding. The tests were conducted using the Gleeble 3800 metallurgical process simulator with the PocketJaw module. Based on the analysis of the obtained results, it was found that for tubes with a wall-thickness-to-inner-diameter ratio of 0.5, it is justified to use tools with a longer sizing section and welding chamber, as well as a larger mandrel generating-line angle within the welding chamber. Full article

The static stability of an elastic, incompressible nanorod subjected to an extensional force is analyzed. The force is applied to a rigid rod that is welded to the free end of the nanorod. The material behavior of the nanorod is described using a two-phase local/nonlocal stress-driven model. Mathematically, the problem is formulated as a system of nonlinear differential equations suitable for nonlinear analysis. For the analysis, the Liapunov–Schmidt method is employed. Depending on a geometric parameter (the length of the rigid rod) and nonlocal parameters (the small length-scale parameter and the phase parameter), the buckling load and post-buckling behavior of the nanorod are determined. The results show that the nonlocal effect increases the buckling load, indicating a stiffening effect. An increase in the length of the rigid rod decreases the buckling load. Regarding the post-buckling behavior, it is shown that both supercritical and subcritical bifurcations can occur, depending on the values of the geometric and nonlocal parameters. The occurrence of a subcritical bifurcation, which is highly undesirable in real-world constructions, is a novel effect not observed in the classical Bernoulli–Euler theory. Full article