Search Results (119)

Climate concerns are driving the automotive industry to adopt advanced manufacturing technologies that aim to improve energy efficiency and reduce vehicle weight. In this context, lightweight structural materials such as aluminium alloys have gained significant attention due to their favorable strength-to-weight ratio. Laser welding plays a crucial role in assembling such materials, offering high flexibility and fast joining capabilities for thin aluminium sheets. However, welding these materials presents specific challenges, particularly in controlling heat input to minimize distortions and ensure consistent weld quality. As a result, numerical simulations based on the Finite Element Method (FEM) are essential for predicting weld-induced phenomena and optimizing process performance. This study investigates welding-induced distortions in laser butt welding of 1.5 mm-thick Al 6061 samples through FEM simulations performed in the SYSWELD 2024.0 environment. The methodology provided by the software is based on the Moving Heat Source (MHS) model, which simulates the physical movement of the heat source and typically requires extensive calibration through destructive metallographic testing. This transient approach enables the detailed prediction of thermal, metallurgical, and mechanical behavior, but it is computationally demanding. To improve efficiency, the Imposed Thermal Cycle (ITC) model is often used. In this technique, a thermal cycle, extracted from an MHS simulation or experimental data, is imposed on predefined subregions of the model, allowing only mechanical behavior to be simulated while reducing computation time. To avoid MHS-based calibration, this work proposes using thermal cycles acquired in-line during welding via infrared thermography as direct input for the ITC model. The method was validated experimentally and numerically, showing good agreement in the prediction of distortions and a significant reduction in workflow time. The distortion values from simulations differ from the real experiment by less than 0.3%. Our method exhibits a slight decrease in performance, resulting in an increase in estimation error of 0.03% compared to classic approaches, but more than 85% saving in computation time. The integration of real process data into the simulation enables a virtual representation of the process, supporting future developments toward Digital Twin applications. Full article

Laser–MIG hybrid welding–brazing was performed to join TC4 titanium alloy and 5083 aluminum alloy with ER5356, ER4043 and ER2319 filler wires. The effects of the different filler wires on the microstructural features and mechanical properties of Ti/Al welded–brazed butt joints were investigated in detail. The wetting and spreading effect of the ER4043 filler wire was the best, especially on the weld’s rear surface. Serrated-shaped and rod-like IMCs were generated at the top region of the interface of the joint with ER4043 filler wire, but rod-like IMCs did not appear at the joints with the other filler wires. Only serrated-shaped IMCs appeared in the middle and bottom regions for the three filler wires. The phase compositions of all the IMCs were inferred as being made up of TiAl₃. The average thickness of the IMC layer of joints with the ER5356 and ER2319 filler wires was almost the same and thinner than that of the joint with the ER4043 filler wire. The average thickness was largest in the middle region and smallest in the bottom region for all the joints with the three filler wires. The average microhardness in the weld metal of ER5356, ER4043 and ER2319 filler wires could reach up to 77.7 HV, 91.2 HV and 85.4 HV, respectively. The average tensile strength of joints with the ER5356, ER4043 and ER2319 filler wires was 106 MPa, 238 MPa and 192 MPa, respectively. The tensile samples all fractured at the IMC interface and showed a mixed brittle–ductile fracture feature. These research results could help confirm the appropriate filler wire for the laser–MIG hybrid welding–brazing of Ti/Al dissimilar butt joints. Full article

TC4 titanium alloy and 5083 aluminum alloy with different groove shapes were joined by laser-MIG hybrid welding–brazing using ER4043 filler wire. The effects of groove shape on the weld formation, intermetallic compounds and tensile property of the Ti/Al butt joints were investigated. The welds without obvious defects could be obtained with grooves of I-shape and V-shape on Ti side, while welds quality with grooves of V-shape on Al side and V-shape on both sides were slightly worse. The interfacial intermetallic compounds (IMCs) on the brazing interface were homogeneous in the joints with groove of V-shape on Ti side, and V-shape on both sides, which had similar thickness and were both composed of TiAl₃. Unlike the IMCs mainly composed of TiAl₃ at the I-shape groove interface, TiAl₃, TiAl, and Ti₃Al constituted the IMCs at the V-shape on Al side interface. The average tensile strength of Ti/Al joints with groove of I-shape was the highest at 238 MPa, and was lowest at 140 MPa with groove of V-shape on Al side. The tensile samples mainly fractured at IMCs interface and the fractured surfaces all exhibited mixed brittle–ductile fracture mode. Based on the above research results, I-shape groove was recommended for laser-arc hybrid welding–brazing of 4 mm thick Ti/Al dissimilar butt joints. Full article

In large welding structures, maintaining a uniform assembly condition and machined dimension in the pre-welding groove is challenging. The assembly condition and machined dimension of the pre-welding groove significantly impact the selection of the welding parameters. In this study, laser–arc hybrid welding is used to perform butt welding on 6 mm Q345 steel in various assembly conditions, and we propose an adaptive model of the BP neural network optimized by a genetic algorithm (GA) for laser–arc welding. By employing the GA algorithm to optimize the parameters of the neural network, the relationship between the pre-welding groove parameters and welding parameters is established. The mean square error (MSE) of the GA-BP neural network is 0.75%. It is verified via experiments that the neural network can predict the welding parameters required to process a specific welding morphology under different pre-welding grooves. This model provides technical support for the development of intelligent welding systems for large and complex components. Full article

Laser welding–brazing experiments with 6061 aluminum alloy and Q235 steel were conducted using AlSi12 and ZnAl22 as filler metals. The macroscopic morphologies and microstructures of welding–brazing joints were analyzed by optical microscopy (OM) and scanning electron microscopy (SEM). The effects of Si and Zn elements in filler wires on the macroscopic morphologies, interfacial microstructures, tensile properties, and corrosion resistances of joints were studied. The results show that the wettability of ZnAl22-filler wire was better than that of AlSi12-filler wire. The fusion zone of the joint welded with AlSi12-filler wire consisted of α–Al solid solution and Al–Si eutectic mixture, while the interfacial reaction zone was composed of η-Fe₂(Al, Si)₅ and τ₅-Fe_1.8Al_7.2Si. The fusion zone of the joint formed using AlZn22-filler wire consisted of α–Al solid solution, η-Zn solid solution, and ZnAl eutectic structure. The joint welded with AlSi12-filler wire showed better tensile strength and corrosion resistance compared to that welded with ZnAl22-filler wire. Full article

In order to further study the effect of welding residual stress on the fatigue strength of a TC4 titanium alloy sheet during laser welding, a laser welding butt joint model for TC4 titanium alloy sheets was established using ABAQUS (2022) software. The temperature and residual stress fields generated during the welding process were comprehensively simulated, and the melt pool shape and residual stress magnitudes were experimentally verified. The experimental parameters included a laser power range of 900–1200 W, welding speeds of 12.5 and 25 mm/s, and a double-sided welding approach with a cooling interval of 20 s between passes. The findings indicate that welding residual stress is primarily concentrated around the weld and the heat-affected zone, predominantly as tensile stress, with the maximum value observed at the weld’s initiation point, reaching 920 MPa—close to the material’s tensile strength limit. Under ideal conditions (without considering welding residual stress), the fatigue life at the weld area is estimated to reach 188,799 cycles, while the fatigue life of the base material without welding is calculated to be 167,109 cycles. However, when accounting for welding residual stress, the fatigue strength of the sheet decreases significantly, with the minimum fatigue life occurring at the weld toe, measured at 10,471 cycles. This study demonstrates that welding residual stress has a substantial impact on the fatigue life of TC4 titanium alloy sheets, particularly in the heat-affected zone, where the fatigue life is reduced by nearly 94% compared to the ideal condition. These results provide critical insights for improving the fatigue performance of laser-welded TC4 titanium alloy components in engineering applications. Full article

The recent technological advancements in today’s manufacturing industry have extended the quality control operations for welding processes. However, the realm of pre-welding inspection, which significantly influences the quality of the final products, remains relatively uncharted. To this end, this study proposes an innovative vision system designed to extract the seam gap width and centre between two components before welding and make informed decisions regarding the initiation of the welding process. The system incorporates a deep learning semantic segmentation network for identifying and isolating the desired gap area within an acquired image from the vision sensor. Then, additional processing is performed, with conventional computer vision techniques and fundamental Euclidean geometry operations for acquiring the desired width and the centre of that area with a precision of 0.1 mm. Additionally, a control graphical interface has been implemented that allows the operator to initiate and monitor the entire inspection procedure. The overall framework is applied and tested on a manufacturing case study involving the laser welding operations of sheet metal parts, and although it is designed to handle gaps of different shapes and sizes, it is mainly focused on obtaining the characteristics of butt weld gaps. Full article

This investigation aimed at evaluating the weldability of a 2.1 GPa-grade hot stamping steel (HSS) containing 0.40 wt.% carbon using laser butt welding. It is shown that the subject HSS can be properly joined by laser welding without welding defects, such as voids and micro-cracks. The mechanical properties of joints before and after hot stamping were examined using cross-weld uniaxial tension and Vickers hardness, while microstructure was systematically characterized using optical microscopy and electron backscatter diffraction. The experimental results demonstrate that fresh martensite was formed in the weld nugget after welding, leading to a hardness much higher than that of the base metal. Nevertheless, such cross-weld microstructural heterogeneity was erased after hot stamping and low-temperature baking heat treatments, resulting in a uniform microstructure of lath martensite across the weld. As a result, the joint after hot stamping and baking exhibited an ultimate tensile strength of 2140 MPa and a total elongation of 12.03%, with the fracture occurring in the base metal. Such excellent mechanical properties of the joint demonstrate the great weldability of the present 2.1 GPa-grade HSS during laser welding. Full article

Infrared (IR) magneto-optical (MO) bi-imaging is an innovative method for detecting weld defects, and it is important to process both IR thermography and MO imaging characteristics of weld defects. IR thermography and MO imaging can not only run simultaneously but can also run separately in special welding processes. This paper studies the sensing processing of eddy current IR thermography and MO imaging for detecting weld defects of laser spot welding and butt joint laser welding, respectively. To address the issues of high-level noise and low contrast in eddy current IR detection thermal images interfering with defect detection and recognition, a method based on least squares and Gaussian-adaptive bilateral filtering is proposed for denoising eddy current IR detection thermal images of laser spot welding cracks and improving the quality of eddy current IR detection thermal images. Meanwhile, the image gradient is processed by Gaussian-adaptive bilateral filtering, and then the filter is embedded in the least squares model to smooth and denoise the image while preserving defect information. Additionally, MO imaging for butt joint laser welding defects is researched. For the acquired MO images of welding cracks, pits, incomplete fusions, burn-outs, and weld bumps, the MO image processing method that includes median filtering, histogram equalization, and Wiener filtering was used, which could eliminate the noise in an image, enhance its contrast, and highlight the weld defect features. The experimental results show that the proposed image processing method can eliminate most of the noise while retaining the weld defect features, and the contrast between the welding defect area and the normal area is greatly improved. The denoising effect using the Natural Image Quality Evaluator (NIQE) and the Blind Image Quality Index (BIQI) has been evaluated, further demonstrating the effectiveness of the proposed method. The differences among weld defects could be obtained by analyzing the gray values of the weld defect MO images, which reflect the weld defect information. The MO imaging method can be used to investigate the magnetic distribution characteristics of welding defects, and its effectiveness has been verified by detecting various butt joint laser welding weldments. Full article

Dissimilar welding between aluminum and copper poses significant challenges, primarily due to differences in their thermal and mechanical properties, resulting in brittle intermetallic compounds, limited joint strength, and high electrical resistivity. This study aims to overcome these issues by employing Ag-18Cu-10Zn filler material and optimizing laser power with a focus on improving joint strength and electrical conductivity. The results indicate that the incorporation of silver and zinc enhances the phase composition and microstructure of the weld. By forming solid solution phases such as Ag₂Al and Cu₅Zn₈, the brittle Al₂Cu phase commonly found in traditional Al/Cu welding is replaced. This not only promotes the heterogeneous nucleation of fine silver-rich grains but also restricts the excessive growth of silver-poor grains, resulting in a uniform distribution of fine grains throughout the weld. These modifications contribute to both fine-grain strengthening and dispersion strengthening. At an optimal laser power of 750 W, joint strength reaches 109 MPa, while joint resistivity decreases to 3.19 μΩ·cm, 12.6% lower than that of the aluminum alloy base material. This study proposes a process for achieving highly conductive, reliable Al/Cu dissimilar metal joints, potentially impacting the aluminum–copper connections in battery modules for new energy vehicles. Full article

In this paper, the butt joint of unequal thickness 410 ferritic stainless steel and RCL540 low-carbon alloy steel sheets are realized by laser welding. The effects of different laser powers on weld formability, mechanical properties, and residual stress in the welding process are investigated. It is observed that with increasing laser power, the heat accumulates at the bottom of the molten pool and weld metal, causing the ratios of upper and lower melt widths to decrease. The tensile test results show that all specimens fractured in the weak zone of the base metal on the stainless steel side at 10 mm from the weld seam. The residual stress distributions of the specimens are calculated using ABAQUS 2022 software and compared with the measurements of the blind-hole method. It is found that the stainless steel side produces tensile stresses, with the power increase offset by compressive stresses in the base metal. When the laser power is 1200 W, the welded joint has the best weld formability and mechanical properties and the least residual stress. The upper and lower melt width ratio is 1.17, the maximum microhardness of the weld metal is 374.7 HV, the maximum test force and tensile strength are 5617.5 N and 468.12 MPa, respectively, and the minimum values of the transverse and longitudinal stresses are −45.8 MPa and −106.4 MPa, respectively. Full article

Aluminium and its composites are widely used in production to enhance the strength of lightweight objects. In this study, an AA7075/SiC composite was fabricated using a stir casting route. Multi-objective optimization and finite element analysis were performed with various process parameters on a manufactured aluminium composite (AA7075 + SiC) undergoing a laser beam welding process. Four welding parameters, i.e., pulse frequency, power, welding speed (transverse), and wire size were taken for laser welding as per the L-9 orthogonal array for experimental study. Tensile strength, deflection, temperature distribution, Rockwell hardness (fusion zone), and Rockwell hardness (heat affected zone) were taken as output parameters after welding. The standard deviation objective weighting–grey relational optimization method optimized the process parameter. ANSYS APDL 23 software was utilized to simulate the entire laser welding method with a cylindrical heat source to predict the temperature distribution in the butt-welded plates. This software uses finite element analysis and gives a deviation of only 5.85% for temperature distribution with experimental results. This study helps to understand the effect of various parameters on the welding strength of the aluminium composite. Full article

Laser welding on thin plates of high-strength steel is increasing in various industrial applications. The mechanical behavior of welded joints depends on their local properties, which in turn depend on the welding parameters applied to join the base material. This work characterizes the local properties of butt-welded joints of thin plates of high-strength–low-alloy (HSLA) steel. This study focuses on the effect of welding parameters on the microstructure, tensile response, microhardness, and weld bead profile. For this purpose, a factorial experimental design was formed, covering a heat input range from 53 to 75 J/mm. This study identified the main effects and interactions of welding speed and laser power on the weld bead profile and on its width. The microstructure, weld bead width, hardness, and tensile mechanical properties were significantly influenced by heat input. Furthermore, numerical simulations on real weld bead profiles revealed high values of the stress concentration factor and suggested a correlation with heat input. Full article

This study aims to investigate the effect of the laser beam overlap rate on the mechanical properties of Al3003 aluminum alloy arc weldment with laser peening. To determine the optimal laser beam overlap rate for laser peening of the weldment, peening experiments were conducted on bead-welded and butt-welded specimens with varying overlap rates, and the effect of the beam overlap rate was analyzed. As the overlap rate increased, the residual stress changed from tensile to compressive, with the highest level of compressive residual stress at the overlap rate of 75%. Laser peening was performed on the aluminum weldment of the prototype, applying the optimal peening conditions identified earlier. As a result of comparing the residual stress, hardness, and tensile strength of the weld before and after laser peening, it was found that the tensile residual stress in the weldment was improved to a compressive residual stress of about −50 MPa or more. The hardness and tensile strength of the weld increased after peening, and the mechanical properties were also improved. Full article

Laser beam welding (LBW) is a highly demanded process for premium-quality joints in aeronautic, energy, or industrial sectors, where flexibility and low-heat-affected zones are required. One of the main applications of LBW in the near future is expected to be the welding of new turbine engine components, which are typically made of Nickel-based superalloys. However, parameter setup is time- and resource-consuming, where experiment-based methods are typically employed. Therefore, the process development is far from an efficient resource utilization. In the present work, an LBW numerical model is developed and experimentally validated through a machine-integrated monitoring system. The LBW model is based on solving the heat transfer problem produced by the laser and provides the resulting temperature field, as well as the weld bead dimensions. The model includes a variable heat source that automatically adapts to the welding regime, conduction, or keyhole. For the model validation, two Inconel 718 sheets of different thicknesses are butt-welded and an error of around 10% is obtained, which ensures the validity of the model. Full article