Welding in the World最新文献

The analysis in this study is centered on the butt laser welding of 2.5-mm-thick sheets of 6063-T6 and 6082-T6 aluminum alloys. This type of joint is common in new energy vehicle bodies. It helps to reduce weight and combines the strength and toughness of both alloys. This investigation applies numerical simulation to examine the effects of laser heat input on the behavior of the molten pool’s flow. A rise in heat input is associated with a decrease in the molten pool’s stability. This phenomenon is evidenced by the retrograde and ascending movement of the liquid metal within the pool. The formation of columnar crystals is observed in the weld metal zone (WMZ) adjacent to the fusion line (FL) on both sides, while equiaxed crystals are primarily found at the heart of the WMZ. With increased heat input, the weld joint’s micro-hardness, ultimate tensile strength, and elongation undergo an initial increase and are followed by a decrease. The side of 6063-T6, characterized by a lower initial hardness, undergoes rapid solidification near the FL, leading to the formation of fine non-equilibrium grains. Due to their small size and high defect density, the mechanical strength is reduced, which is the site of fracture. Recommended for publication by Commission IV—Power Beam Processes.

Laser-directed energy deposition (L-DED) demonstrates high reliability in repairing titanium alloy components, validated through fatigue assessments of Ti60 heterogeneous structures containing base material (BM) and deposited zone (DZ). The present L-DED process achieves robust metallurgical bonding with near-isotropic DZ microstructures, yielding minimal strength mismatch and comparable fatigue lives between BM and DZ. Deposited material can be near defect-free as confirmed via X-ray computed tomography. A cyclic plasticity model, calibrated using wrought material data, simulates interfacial multi-axial stresses and strain localization. Critical plane-based models predict fatigue lives effectively, demonstrating the applicability of conventional assessment frameworks in medium- to high-cycle fatigue regime. DZ shows better defect tolerance than the BM, with its higher fatigue limit based on Murakami’s empirical model. Stress triaxiality near the interface accelerates low-cycle fatigue damage, yet no interfacial failures occur, highlighting the process’s mechanical robustness. These findings validate the L-DED process in balancing defect control and performance, providing a reliable methodology for aerospace component repair.

In response to the crisis of global climate change, various national and industrial efforts to reduce greenhouse gas emissions continue to be implemented. In particular, the aviation, automotive, and material industries are striving to reduce CO₂ emissions by utilizing magnesium alloys to achieve product weight reduction. Magnesium alloy, as a representative lightweight non-ferrous metal, has been observed in other studies to exhibit excellent properties, such as high specific strength, electromagnetic shielding ability, and vibration and impact absorption. However, due to the inherent material properties of magnesium alloys, challenges arise when welding is conducted. This is in contrast to other metals such as iron-based alloys. Therefore, various studies are still being conducted to address and improve these issues. In this study, bead-on-plate experiments using fiber laser welding on magnesium alloys were conducted to determine the appropriate butt welding conditions. Based on the derived conditions, butt welding was performed, followed by an analysis of the mechanical behavior and microstructure to investigate the characteristics. The results of this study identified a correlation between the characteristics of magnesium alloys and their mechanical behavior during fiber laser welding, suggesting that the findings could serve as fundamental data for future industrial applications.

This study investigates the impact of laser overlap welding parameters on the mechanical and microstructural properties of dissimilar joints between AISI 1018 low-carbon steel and stainless steel 301LN. A series of experiments were conducted varying laser power, travel speed, and oscillation amplitude to determine optimal welding conditions. Tensile tests revealed that the welds exhibited significantly different strengths and displacements, with the optimal parameters achieving a maximum load of 39.6 kN and a displacement of 9.3 mm. Macrostructural analysis indicated that higher oscillation amplitudes resulted in broader but shallower welds, whereas lower amplitudes achieved deeper penetration. Microstructural examination showed varied phase formations, including martensite and bainite, influenced by the diffusion of alloying elements such as chromium and nickel. The formation of chromium carbides significantly enhanced the hardness of the fusion zone, with microhardness values reaching up to 470 HV at moderate penetration. Fractographic analysis of tensile-tested samples highlighted different fracture mechanisms, with optimal welds fracturing in the base material rather than the weld interface, indicating superior joint strength. This study provides critical insights into optimizing laser overlap welding parameters to enhance the mechanical performance and structural integrity of dissimilar metal joints, contributing to improved industrial welding practices.

The influence of external constraint time on the stress and deformation caused by laser welding of thin SUS301L stainless steel was quantitatively studied. Due to the inability to accurately control the fixture constraint time in the experiment, this paper uses a three-dimensional thermal elastoplastic finite element simulation method to study the deformation, stress, and strain changes of welded stainless steel plates under different fixture constraint times. In order to improve simulation accuracy, the relationship between mesh size and thermal input in finite element analysis is analyzed. The method of sequential coupling thermo-mechanic is proposed to analyze the transient temperature field and deformation during welding. The thermal and mechanical material properties used in the simulation follow a non-linear relationship as a function of temperature. Meanwhile, the accuracy of the simulation model was verified based on the temperature history by the K-type thermocouple and weld profile measured. The results show that the length of the clamp restraint time will indeed have a certain effect on the deformation after welding. Release of the clamp 25 s after the end of welding can effectively reduce the welding deformation from 1.3 to 1.21 mm, which is a 7% reduction.

The welding efficiency and weld formation quality of pipeline external welding are important factors that constrain the site laying speed and service performance of long-distance oil and gas pipeline. It is urgent to optimize the structure and function of pipeline welding equipment and control system, and improve the intelligent level of the external welding process. This paper focuses on improving weld bead formation quality during the pipeline all-position welding. Based on the Pieper criterion, a 5-degree of freedom (DOF) welding robot is designed. It can meet the control requirements of welding torch position and posture (WTPP) that comply with the welding process parameters at any welding position of pipeline. The kinematic model of the designed robot is established, and an analytical solution to its inverse kinematics is derived. Combined with the composite sensor based on combined laser line structured lights vision sensor and gravity sensor, the pipeline all-position intelligent welding system is integrally constructed. Based on this, the detection method of welding groove size and WTPP parameters is proposed. Through the designed program control strategy, the intelligent adjustment experiments of the WTPP were carried out during the pipeline all-position welding process. The lateral tracking deviation of welding torch was not more than 0.25 mm; the vertical tracking deviation was not more than 0.63 mm, and the posture angles feedback control deviation were not more than 0.8°. The good weld formation effect was obtained, which provides support for the improvement of the intelligent level of pipeline external welding. 

Wire arc additive manufacturing (WAAM) is an advanced and cost-effective technique for fabricating large-scale metal components; however, the process induces significant residual stress due to complex thermal cycles, leading to defects such as deformation and cracking. This study presents a generalized finite element analysis (FEA) model to investigate the temperature distribution and residual stresses evolution during the GTAW-based WAAM process. A thermo-mechanical explicit model was developed using Ansys software and validated experimentally using K-type thermocouples and X-ray diffraction (XRD) techniques. Additionally, detailed mechanical characterization, including tensile strength, impact strength, hardness, and electron backscatter diffraction (EBSD)-based microstructural analysis, was conducted. The numerical simulation demonstrated strong agreement with experimental results, with a maximum relative error of less than 8%. The findings reveal that WAAM-fabricated ER70S-6 components exhibit almost homogenous and isotropic mechanical properties throughout the build wall, indicating superior structural integrity.

This study focuses on the utilization of high-frequency mechanical impact (HFMI) treatment for rehabilitating pre-fatigued steel bridge components. It incorporates time of flight diffraction (TOFD) for precise crack depth measurement, alongside strain range drop monitoring to enhance assessment accuracy. The experimental setup involves fillet weld specimens with cope hole geometry, using S355MC steel. The HFMI treatment process employs 3-mm diameter pins to achieve an HFMI indentation depth of 0.2 mm. The study demonstrated that HFMI treatment effectively extends the fatigue life of steel bridge components, showing significant improvements for cracks up to 1.2-mm deep. TOFD measurements, validated against manual optical measurements, consistently indicated crack depths within ± 0.1-mm accuracy. This precision is critical for assessing the HFMI treatment’s effectiveness in repairing pre-fatigued structures. The strain range drop method was used as a stop criterion to evaluate crack depth in real time, effectively reducing the number of TOFD measurements required during fatigue crack growth testing. The experimental results showed that HFMI treatment could improve fatigue life, moving specimens’ performance well above the IIW recommended FAT125 curve for treated steel details. In conclusion, this investigation confirms the significant potential of HFMI treatment for extending the life of pre-fatigued steel bridge components. The combined use of TOFD and strain range drop monitoring provides a robust framework for accurately assessing and optimizing HFMI treatment.

In this research, the effects of the welding angle on the behavior of the molten pool, keyhole, and welding defects in the laser-MAG hybrid welding process of 14-mm-thick AH36 high-strength shipbuilding steel are thoroughly analyzed. High-speed photography was used to observe the behavior of the molten pool and keyhole, while synchronized oscilloscope measurements revealed a strong correlation between arc voltage fluctuations and keyhole oscillation frequencies, demonstrating the dynamic interplay between arc plasma and keyhole stability. The results reveal that the welding angle significantly affects the quality of weld formation, molten pool flow, keyhole behavior, collapse, and bottom hump, as well as spatter phenomena. When the welding angle is 82.5°, optimal weld formation quality is achieved, characterized by a stable molten pool shape and regular keyhole behavior. At a 75° welding angle, the molten pool shape and keyhole behavior exhibit significant instability, leading to poor weld formation. This results in the periodic formation of the narrowest throat on the surface of the molten pool, presenting a wide-narrow-wide serrated characteristic, which triggers surface collapse and hump defects. Furthermore, at a 97.5° welding angle, intense unstable fluctuations occur within the molten pool, causing the molten metal to overcome surface tension and bulge beyond the surface of the molten pool, forming violent fluctuations and a raised liquid column that progressively detaches from the molten pool to form spatter. The research findings indicate that an appropriate welding angle can optimize the behavior of the molten pool and reduce welding defects.