Modeling Of Laser Welding Research Articles

Heat transfer and fluid flow modeling of steel-Inconel laser welding in an overlap configuration

This paper introduces a multiphysical model for laser welding in a lap joint configuration with dissimilar metals. Initially solved in a 2D axisymmetric configuration for static shots, the model is extended to 3D to simulate laser welding with a weld seam formation. Heat transfer, fluid flow, and species tracking are solved with the level set method to describe dynamically the keyhole and melt pool behavior. Validation against experimental data shows an accurate description of the main phenomena. The paper mainly highlights the need of introducing a thermal contact resistance to correctly predict the melted area dimensions. The study emphasizes the importance of considering imperfect material contact and proposes an effective approach for thermal contact resistance, a phenomenon poorly discussed in the literature.

Multi- objective modeling and optimization of dissimilar laser welding by integrating an artificial intelligence predictive model with NSGA-II algorithm

This study presents a pioneering approach in laser welding of two dissimilar materials by integrating an Artificial Intelligence (AI)-based on predictive model with the Non-dominated Sorting Genetic Algorithm II (NSGA-II) for optimizing key performance characteristics of Nickel-based alloy and duplex 2205 stainless steel. Focusing on four primary input variables including laser power, welding speed, focal distance and deviation, the research aims to predict and optimize the responses including temperature field adjacent to the melt pool, penetration depth, and tensile strength of the joint according to the experimental results. The developed AI model first accurately forecasts these characteristics based on the inputs. This predictive accuracy is critical in defining the optimal target values. Considering the multidimensional nature of the problem, where enhancing one characteristic could compromise another, the study employs a Multi-Objective Optimization (MOO) strategy. This is where the innovative integration with NSGA-II becomes pivotal. Renowned for its efficiency in navigating multiple, potentially conflicting objectives, NSGA-II assists in achieving a balanced optimization of all target parameters. This method is adept at considering the complex interdependencies among various characteristics. The novelty of this work lies in its unique combination of AI for prediction and MOO for optimization and it is for the first time that machine learning is applied on this kind of alloys with four features and four targets.

A modelling approach for laser welding of busbars to lithium-ion prismatic cell terminals to enhance failure prediction

Laser welding is increasingly being used to connect automotive battery packs and weld busbars to prismatic cell terminals due to its ability to weld a wide variety of materials at high speed. The choice of material for the connecting busbars is primarily based on weldability, weight, electrical/thermal conductivity and cost. Aluminum (Al) is increasingly being chosen as busbar material to meet these criteria. This paper investigates laser overlap welding of Al for producing busbar-to-terminal interconnects for prismatic cell assembly. To understand the strength of these laser-welded joints in the early stages of design, the joints must be modelled. In addition, the structural modelling of battery module connections is critical to understanding the impact resistance (crash safety) of electric vehicles. Fusion-based modelling of laser welding is computationally inefficient and difficult to integrate into large structural models e.g., full vehicle crash models. Instead, it is more computationally efficient to generate a structural model of the weld, tuned to experimental test data, which can be easily integrated into larger models. LS-DYNA was employed to model the mechanical behavior of 1 mm to 1 mm AA1050 laser welds. Welding was performed using a wobble head integrated with a 1 kW CW fiber laser system. The simulation is based on laser weld with a rectangular pattern and was developed from experimental data from lap shear, T-peel, cross-tension and torsion tests. This modelling approach was extended to obtain joint strength for laser welding a 1.5 mm 1060 Al busbar to a 4 mm 1060 Al prismatic cell terminal. The predicted load–displacement curves closely matched the test data.

Study on improvement of weld defect in oscillating laser welding of aluminum alloy T-joints assisted by solder patch

During oscillating laser welding of aluminum alloy T-joints assisted by solder patch, it is found that the pore defect can be reduced and the high quality welded T-joints are obtained. To understand the effect of oscillating laser on the formation process of T-joint welds, a dynamic model for laser welding of aluminum alloy T-joints assisted by solder patch is developed in this paper to analyze the dynamic behaviors of keyhole and molten pool. Based on the dynamic model, the morphology characteristics of keyhole and the evolution processes of molten pool temperature and flow fields during conventional laser welding and oscillating laser welding are calculated and compared. The simulation results are found to be kept consistent with the experimental results. It is demonstrated that the keyhole is characterized with better morphology and higher stability and the degassing condition of molten pool is improved during oscillating laser welding compared with conventional laser welding. The molten pool temperature and flow fields are much more uniform during oscillating laser welding. The obtained results are efficient for suppressing weld defects and achieving high quality welding of aluminum alloy T-joints.

Simultaneous reduction in laser welding energy consumption and strength improvement of aluminum alloy joint by addition of trace carbon nanotubes

The widespread use of laser welded aluminum alloys in industrial production offers potential benefits to sustainable development and socio-economic progress. It simultaneously enhances the weld strength while reduces the energy consumption. Despite the promise of these alloys, research on reducing their energy consumption during laser welding is lacking. In this study, a dual effect of enhancing joint strength in 2A12 aluminum alloy and reducing energy consumption is achieved by the addition of trace carbon nanotubes (CNTs). The “welding efficiency" is defined and an energy consumption model for laser welding of aluminum alloys is developed. Next, the laser welding process with the addition of trace CNTs (LC) and the single laser welding process (LW) were compared and analyzed. The results indicate that adding trace CNTs can reduce energy consumption by more than 33 % and increase joint strength by 101 MPa. Furthermore, it is found that the LC process offers significant energy-saving advantages over other laser welding of aluminum alloy processes described in previous studies. These improvements is attributed to the increased laser absorption by the aluminum alloy induced by trace CNTs, as well as their residual presence in the joint, which acts as a strengthening medium. This work provides new insights and presents a novel approach for achieving low-carbon, high-quality welding of aluminum alloys.

A novel integrated process-performance model for laser welding of multi-layer battery foils and tabs

A novel integrated process-performance model for laser welding of multi-layer battery foils and tabs

An Inhomogeneous Model for Laser Welding of Industrial Interest

An innovative non-homogeneous dynamic model is presented for the recovery of temperature during the industrial laser welding process of Al-Si 5% alloy plates. It considers that, metallurgically, during welding, the alloy melts with the presence of solid/liquid phases until total melt is achieved, and afterwards it resolidifies with the reverse process. Further, a polynomial substitute thermal capacity of the alloy is chosen based on experimental evidence so that the volumetric solid-state fraction is identifiable. Moreover, to the usual radiative/convective boundary conditions, the contribution due to the positioning of the plates on the workbench is considered (endowing the model with Cauchy–Stefan–Boltzmann boundary conditions). Having verified the well-posedness of the problem, a Galerkin-FEM approach is implemented to recover the temperature maps, obtained by modeling the laser heat sources with formulations depending on the laser sliding speed. The results achieved show good adherence to the experimental evidence, opening up interesting future scenarios for technology transfer.

Multi-Component Evaporation and Uneven Aluminum Distribution during High-Power Vacuum Laser Welding of Ti-6Al-4V Titanium Alloy

Titanium alloy is an important material for the manufacture of key components of deep-sea submersibles. High-power vacuum laser welding is an important method for welding TC4 thick plate (40–120 mm) structures. However, due to the low melting point of aluminum, its uneven distribution in the weld caused by evaporation during welding affects the quality of joints. This paper conducted experimental and simulation studies to investigate the effect of process parameters on multi-component evaporation and uneven aluminum distribution. Based on a three-dimensional model of vacuum laser welding, the mechanism of the uneven distribution of aluminum in the weld is explained. The results show that the uneven distribution of aluminum in the weld is mainly related to the metal vapor behavior and keyhole morphology. As the welding speed rises from 1 m/min to 3 m/min, the proportion of aluminum in the metal vapor and the degree of compositional unevenness increase. When the laser power increases from 6 kW to 18 kW, the proportion of aluminum in the metal vapor and degree of unevenness increase, peak at 12 kW, and then decrease. This work facilitates the selection of suitable process parameters to reduce aluminum evaporation during the high-power vacuum welding of Ti-6Al-4V alloys. Joints with a more stable performance can be obtained by avoiding the uneven distribution of aluminum.

Computational modeling of laser welding for aluminum–copper joints using a circular strategy

Dissimilar metal welding poses a significant challenge for researchers in the welding and materials science communities due to the different properties of the metals involved. In this study, we present a novel approach for determining the optimal processing parameters for continuous laser welding (CLW) of dissimilar metals, specifically aluminum and copper, using a circular strategy. The approach utilizes computational fluid dynamics (CFD) simulations to model the welding process and predict joint quality. We validated a CFD-based numerical model for predicting the melt-pool shape across a range of laser power and circular welding speed values. Additionally, we developed artificial neural network (ANN) models that can predict melt pool interface width, penetration depth, and copper concentration for any combination of processing conditions. Using surrogate modeling, we identified the optimal values of laser power and welding speed that result in the highest quality joint. Our results showed that the optimal processing conditions were a laser power of 2950W and a circular speed of 55 mm/s, which resulted in a high-quality Al–Cu joint with maximum shear strength of 2200 N. Microstructural analysis and tensile-shear strength testing confirmed that the optimal conditions resulted in a low degree of intermixing and the absence of large intermetallic compounds (IMCs) in the weld seam. Overall, study offers a valuable contribution to the welding and materials science communities by presenting a novel approach to address a common challenge in dissimilar metal welding. Our approach can be applied to other types of dissimilar metal welding and may inform the development of new welding techniques in the future.

Laser welding of dissimilar materials - simulation driven optimization of process parameters

Laser welding can be used to join dissimilar materials to produce lightweight structures, and electric vehicle battery systems, which are important means of limiting the carbon emissions in the transport industry. Due to the differences in melting temperatures, thermal conductivities, and mutual solubility of dissimilar materials, it is still challenging to create defect-free joints with high mechanical strength, or low contact electrical resistance. In this work, we present a state-of-the-art numerical model of laser welding, developed within the Computational Fluids Dynamics (CFD) paradigm. The multi-physics model simulates melting, flow, and solidification of the alloys and accounts for the laser-material interactions, phase change, temperature and alloy-dependent thermophysical properties, recoil pressure, buoyancy force, and Marangoni effect. The simulation predicts weld penetration depth and width, alloy mixing, as well as the temperature gradient and cooling rate during the solidification that can be further fed into a micro-structure prediction model. The model is coupled with an optimization tool, which iterates over different process parameters to optimize the joint. The methodology is presented for steel to aluminium welding in lap configuration, but it can be used for other materials such as steel-copper, aluminium-copper, or steel-nickel, and in arbitrary geometrical configuration.

Carbon Emission Modeling and Multi-response Evaluation of Fiber Laser Welding

Carbon Emission Modeling and Multi-response Evaluation of Fiber Laser Welding

Effect of Laser Micro-Texturing on Laser Joining of Carbon Fiber Reinforced Thermosetting Composites to TC4 Alloy.

Carbon fiber reinforced thermosetting composites (CFRTS) and TC4 alloy are important structural materials for lightweight manufacturing. The hybrid structure of these two materials has been widely used in the aerospace field. However, the CFRTS-TC4 alloy joint formed by the traditional connection method has many challenges, such as poor environmental adaptability and stress concentration. Laser micro-texturing of metal surface-assisted laser connection of CFRTS and TC4 alloy has great potential in improving joint strength. In order to study the effect of laser micro-texturing on the laser bonding of CFRTS and TC4 alloy, the simulation and experimental research of laser welding of TC4 alloy and CFRTS based on laser micro-textures with different scanning spacings were carried out, and the interface hybrid pretreatment method of laser cleaning and laser plastic-covered treatment was introduced to assist the high-quality laser bonding of heterogeneous joints. The results showed that the established finite element model of CFRTS-TC4 alloy laser welding can predict the temperature field distribution of the joint during the welding process and reflect the forming mechanism of the joint. The laser micro-textures with different scanning spacings will lead to a difference in the temperature field distribution on the polyamide (PA6) interface, which leads to a change in heat input on the CFRTS surface. When the laser scanning spacing is 0.3 mm, the joint strength can reach 14.3 MPa. The failure mechanism of the joint mainly includes the cohesive failure of the internal tear of the carbon fiber and the interfacial failure of the interface between the PA6 resin and the TC4 alloy.

Influence of the free surface reconstruction on the spatial laser energy distribution in high power laser beam welding modeling

An accurate and efficient description of the spatial distribution of laser energy is a crucial factor for the modeling of laser material processing, e.g., laser welding, laser cutting, or laser-based additive manufacturing. In this study, a 3D heat transfer and fluid flow model coupled with the volume-of-fluid algorithm for free surface tracking is developed for the simulation of molten pool dynamics in high-power laser beam welding. The underlying laser-material interactions, i.e., the multiple reflections and Fresnel absorption, are considered by a ray-tracing method. Two strategies of free surface reconstruction used in the ray-tracing method are investigated: a typical piecewise linear interface calculation (PLIC)-based method and a novel localized level-set method. The PLIC-based method is discrete, resulting in non-continuous free surface reconstruction. In the localized level-set method, a continuous free surface is reconstructed, and, thus, the exact reflection points can be determined. The calculated spatial laser energy distribution and the corresponding molten pool dynamics from the two methods are analyzed and compared. The obtained numerical results are evaluated with experimental measurements to assure the validity of the proposed model. It is found that distinct patterns of the beam multiple reflections are obtained with the different free surface reconstructions, which shows significant influence not only on the molten pool behaviors but also on the localized keyhole dynamics.

Numerical Simulation of Preheating Temperature on Molten Pool Dynamics in Laser Deep-Penetration Welding

In this paper, a heat-flow coupling model of laser welding at preheating temperature was established by the FLUENT 19.0 software. The fluctuation of the keyhole wall and melt flow behavior in the molten pool under different preheating temperatures were analyzed, and the correlation between keyhole wall fluctuation and molten pool flow with spatters and bubbles was obtained. The results indicate that when the outer wall in the middle of the rear keyhole wall is convex, the inner wall is concave, which causes spatter or the bottom of the keyhole to collapse. When the metal layer in the middle of the rear keyhole wall turns into obliquely upward flow, welding spatter is generated. In contrast, the metal layer in the middle of the rear keyhole wall changes to flow into the keyhole, and the bottom of the keyhole collapses. When the preheating temperature is 300 K (ambient temperature), 400 K, and 500 K, the inner wall in the middle of the rear keyhole wall is concave. With the increase in the preheating temperature, the area of the concave gradually increases, and the size of the liquid column behind the keyhole opening gradually decreases. When the preheating temperature is 300 K, there are more spatters above the molten pool. In comparison, when the preheating temperature is 400 K or 500 K, there are less spatters, and the bottom of the keyhole collapses.

Study on laser beam butt-welding of NiTinol sheet and input-output modelling using neural networks trained by metaheuristic algorithms

Though NiTinol, the equiatomic Ni-Ti alloy, is revolutionizing different fields of engineering, manufacturing and medicine since its discovery as a functionally advanced material, poor formability and machinability, and the limitations of available fabrication techniques applied for this alloy are restricting its applications in the form of various desired products. Now-a-days, laser welding is the mostly reported joining technique applied to the alloy. Though the difficulties associated with fabrication method and the cost of the alloy are high enough, a computationally efficient model for quick and precise prediction of operating parameters in order to obtain the specified attributes of the laser welded NiTinol sheets is significantly missing in the literature. In the present work, basic metallographic study related to laser welding of NiTinol sheets in butt-joint configuration was investigated. At the same time, an efficient forward and reverse model had been developed with the help of artificial neural network (ANN). These ANNs were trained with the help of regression equation model using five different metaheuristic techniques separately for the development of both forward and reverse models. Laser power, scan speed, frequency, duty factor and focal positions were treated as the input process variables and three different weld attributes, namely bead-area, micro hardness of the bead and tensile strength of the bead were considered as output variables of the process. The developed model was capable enough of predicting the outputs, which were in good agreement with the experimental data, for both forward and reverse models. The novelty of this study deals with the development and testing of feed-forward neural network and recurrent neural network trained using five different metaheuristic techniques for both the forward and reverse modelling of fibre laser welding of NiTinol alloys.

Simulation of the Effect of Keyhole Instability on Porosity during the Deep Penetration Laser Welding Process

The quality of a laser deep penetration welding joint is closely related to porosity. However, the keyhole stability seriously affects the formation of porosity during the laser welding process. In this paper, a three-dimensional laser welding model with gas/liquid interface evolution characteristics is constructed based on the hydrodynamic interaction between the keyhole and molten pool during the laser welding process. The established model is used to simulate the flow and heat transfer process of molten. The Volume of Fluid (VOF) method is used to study the formation and collapse of the keyhole and the formation of bubbles. It is found that bubbles are easy to form when the keyhole depth abruptly changes. There are three main forms of bubbles formed by keyhole instability. The front wall of the keyhole collapses backward to form a bubble. The back wall of the keyhole inclines forward to form a bubble. The lower part of the keyhole produces a necking-down effect, and the lower part of the keyhole is isolated separately to form a bubble. In addition, when the keyhole does not penetrate the base metal, the stability of the keyhole is high and the percentage of porosity is low.

Numerical study of thermal fluid dynamics and solidification characteristics during continuous wave and pulsed wave laser welding

Pulsed wave (PW) mode laser welding is often preferred under conditions where specific heat input and tailorable cooling rate are required. Previous works on numerical modelling of laser welding mainly focus on continuous wave (CW) mode, while physical understanding of PW mode from numerical investigation is scarce. In this work, a 3D multi-physics thermal fluid model is developed considering both CW and PW modes laser welding. The main physical factors involving heat transfer, thermal fluid flow, Fresnel absorption, recoil pressure induced by metal evaporation, Marangoni effect driven by surface tension, free surface tracing, and laser multiple reflections inside the keyhole are included in this model. The model is tested and validated against the corresponding experimental results for laser welds of stainless steel 316 L. The simulated weld fusion cross sections and surface molten pool agree well with the experimentally observed results for both CW and PW modes. The results show that PW mode exhibits a higher depth of penetration and a smaller molten pool at the same heat input with CW mode. In CW mode laser welding, the shape of keyhole is unstable, while its depth keeps relatively stable. There are two main flow patterns in the molten pool of CW mode welding: an outward flow from keyhole outlet to the rear weld pool and a clockwise flow from the keyhole tip to the rear weld pool. While for PW mode, keyhole and molten pool show periodic behaviors with a period of the laser energy output used. The periodic fluid flow pattern is mainly affected by the gradually changed surface tension and suddenly changed recoil pressure. Furthermore, it is found that a finer microstructure with a smaller secondary dendrite arm spacing is obtained in PW mode due to a higher cooling rate from both the calculated and experimentally measured results.

MODELING OF THE WELD PRIMARY MACROSTRUCTURE FORMATION AT LASER WELDING

In modern shipbuilding, those enterprises and shipyards that introduce innovative and highly efficient technologies gain an advantage in the competitive struggle. The experience of the largest European shipyards, such as Meyer Werft and Blohm und Voss in Germany, Kvaerner Massa Yard in Finland, Fincantieri in Italy, shows the great potential of laser equipment in creating breakthrough technologies in shipbuilding. The leading role among the developed technologies is played by the technologies of laser and laser-arc welding. Compared to arc welding, laser and laser-arc welding increase the welding speed by 2-3 times, and a decrease in butt gaps leads to a decrease in the need for welding consumables. The approaches to creating a model for predicting the metal structure and mechanical properties of a welded joint in laser welding are discussed in the paper. This will make it possible to establish welding modes at the preproduction stage and obtain the properties of welded joints specified by the designer. This model is based on mathematical calculations of the thermal regime of welding and the process of crystallization of welds. A mathematical model of laser welding is used, taking into account the presence of a vapor-gas channel, which allows laser radiation to penetrate the entire thickness of the weld, which ensures the formation of a deep, narrow weld. The results of the calculation make it possible to determine the shape of the penetration pool and the position of the main temperature lines in the heat-affected zone. For beam welding methods, it is proposed to approximate the surface of the melt pool (crystallization front) by a cubic spline. Its main advantage is that the entire shape of the surface is modeled most accurately and completely, which allows you to build the surfaces of all areas of the bath without excluding any parts. On the basis of such a spline, the predominant direction of crystallite growth, their growth rate in the direction of welding are determined, and the integral characteristics of the emerging primary macrostructure of the weld metal are found. Based on the criteria characterizing the process of crystallization, a prediction of the macrostructure of the weld metal is given.

Numerical and experimental investigation on the mechanism of synchronous trailing cold air heat sink in eliminating the deformation during laser welding SUS301L thin sheet

In order to control and eliminate the welding induced welding deformation of thin stainless steel a laser welding method assisted by a new type of synchronous trailing cold air heat sink is first proposed in this paper. This kind of heat sink is obtained by using vortex tube compressed air refrigeration (VTCAR), which is safe, of low cost and easy to be implemented compared with other commonly used heat sinks such as argon-water mixture, liquid nitrogen, etc. Then, a thermo-elastic-plastic multi physical field coupling numerical model of laser welding with a cold air heat sink located at the rear of laser beam is established, and the effects of the places where the VTCAR heat sink is exerted and heat sink parameters including the heat sink strength and the distance between the heat sink and the laser beam on the welding induced welding deformation are numerically studied. Such two cases as the heat sink is located on the top and bottom surface of the sample respectively are considered. The simulation results show that the cold source exerted on the top surface has the more significant effect than that on the bottom surface under the same heat sink parameters, and the position of heat sink, exactly speaking, the distance between the cold source and the laser beam, has a decisive effect on reducing welding induced buckling. The smaller the distance, the smaller the welding induced buckling. At the heat sink strength of 200 ml and the distance of 5 mm, the equivalent residual stress decreases by 8.09%, and the maximum welding induced deformation decreases by 31.62%. Thirdly, experiments of laser welding with a synchronous trailing VTCAR heat sink are carried out onSUS301L thin sheet. It can be seen that the specimen appears a saddle shape after welding. The coordinate values of the points on the outer plane of the post weld specimen are measured by three coordinates measuring machine, from which the actual welding deformation can be obtained. Both the specimen shape and the measured welding deformation value are in good agreement with the simulation results based on the large deformation theory, which verifies the correctness and the accuracy of the above simulation model. Finally, the mechanism of the synchronous trailing VTCAR heat sink in eliminating the deformation is discussed by inherent strain theory. In the cooling stage during laser welding, the heat sink not only reduces the temperature field of the base metal near the weld, but also makes the typical comet characteristics at the tail of the weld pool disappear and become a flat temperature profile, which effectively reduces the temperature gradient in the weld area and weakens the longitudinal tensile plastic strain of the weld specimens, and eventually reduces Tendon force and the welding inherent strain. There is a high consistency between Tendon force and the welding deformation, so Tendon force can be taken as the basis for evaluating the welding induced welding deformation.

Modeling of laser welding of stainless steel using artificial neural networks

Laser Welding (LW) is a process which is used to effectively weld metal, alloy or thermoplastics. Laser Welding uses a high concentrated beam of laser to melt the material and to perform welding. Its demand is increasing rapidly in automation as it is fast, more precise, have a deep penetration capacity and have less heat affected zone (HAZ), reduced tendency to spiking thus suitable for Ultra-Narrow Gas Laser Welding (UNGLW). Due to the high cost and time-consuming nature of laser welding experiments, repetition of one experiment in a wide range of data is not feasible. Artificial neural networks have been introduced as an effective tool for predicting values of outcomes and input parameters of various machining processes. In this work, the effect of laser power, welding speed and wire feed rate on the weld quality, i.e., tensile strength and overlap factor is investigated by ANN. Modelling of laser welding of stainless steel is performed using feed forward back propagation trained neural network. The projected outcomes are found to be in good agreement with the previous experimental findings.