Simulation Of Welding Process Research Articles

Distortion simulation of gas metal arc welding (GMAW) processes for automotive body assembly

Distortion simulation of gas metal arc welding (GMAW) processes for automotive body assembly

The Influence of the Tool Tilt Angle on the Heat Generation and the Material Behavior in Friction Stir Welding (FSW)

To improve the accuracy of numerical simulation of friction stir welding (FSW) process, the tool tilt angle must be considered as a significant parameter. In this study, specific considerations for mechanical boundary conditions in Eulerian domain is employed to investigate the tool tilt angle influence on the thermomechanical behavior in FSW. Aluminum 6061-T6 with a thickness of 6 mm under a rotational speed of 800 RPM, a transverse speed of 120 mm/min, and a plunging depth of 0.1 mm were employed for the simulations. Results showed an almost symmetric temperature profile predicted by the model without considering the tool tilt angle, while after incorporating the tool tilt angle, the peak temperature point is moved to the tool backside (around 400 °C), resulting in better material bonding, enhancing the weld joint quality. Without accounting for the tool tilt angle, the highest temperature of 389 °C is observed, while with the tilt angle the maximum temperature of 413 °C is achieved. The temperature variations at different points of the leading (around 360 °C) and the trailing sides (around 400 °C) of the welding tool were measured. It was observed that, after considering the tilt angle, as the tool moves, a smooth and quick increase for the temperature at the tool trailing side is achieved. This smooth and quick increasing of the temperature at the trailing side results in reducing the possibility of the formation of defects, cracks, and voids. Finally, comparisons showed that the model computational time is acceptable, and using Eulerian formulation leads to achieving a remarkable accuracy.

Numerical Study on Welding Residual Stress Distribution of Corrugated Steel Webs

Residual stresses are an inevitable result of the welded fabrication process of corrugated steel webs (CSWs), resulting in structures with high and unpredictable stress fields, causing unexpected failures. The residual stress field is affected by structural parameters and the welding path of CSWs. This study proposes the welding process simulation method for CSWs with element birth and death technology. The optimization design method of heat source parameters is proposed. The feasibility of the simulation method is verified by comparing the numerical results with the experimental results of relevant literature. As a part of the study, a comparison of residual stress fields upon cooling welded CSWs with bending angles of 30, 45, and 60 degrees is presented. Thereafter, the effect of two types of single-sided welding paths and double-sided welding construction processes on residual stress distribution is discussed. Generally, the study results have shown that the equivalent residual stress near the weld reaches the maximum 344 MPa, which is very close to the Q345 steel yield strength. The size of the bending angle has no major effect on the residual stress distribution pattern, but it influences the residual stress value at the bending position. The residual stress at the bending position increases with the bending angle of CSWs. Different welding paths significantly impact the residual stress of the weld toe, and selecting a reasonable welding path can effectively reduce the residual stress value by 20 to 40 MPa.

Dissimilar laser lap welding of Mg and Al alloys using a CoCrFeNi medium-entropy alloy interlayer

Laser welding of Mg to Al dissimilar metals is of great significance in various industries, such as automobile, electrical, electronics, and energy systems, which promotes lightweight composite structure. However, Mg-Al intermetallic compounds (IMCs) have tremendous detrimental effects on the dissimilar metal joining of Mg to Al. In this work, dissimilar Mg/Al alloys joints with CoCrFeNi medium-entropy alloy (MEA) powders interlayer were achieved by the laser welding process, and the effect of different laser powers on the microstructure and mechanical properties of the joints was analyzed, reaching a maximum tensile shear strength of 100.12 MPa. The formation mechanism of the interface was investigated by experimental investigations and thermodynamic calculations. In addition, a numerical simulation of the laser welding process was carried out to reveal the temperature field of the molten pool and the flow change process. Based on the law of multi-component HEA phase formation, the interfacial metallurgical products were calculated and analyzed. The results of the energy dispersive spectroscopy show that the molten CoCrFeNi MEA powders reacted with Al to form Al-rich AlxCoCrFeNi phase, due to a more negative generation enthalpy compared to Mg-Al IMCs. With the increase of laser power, the Al-rich AlxCoCrFeNi phase mixed layer went through four states of agglomeration, continuity, interruption and dispersion, while the IMCs at the interface gradually increased and finally tend to be continuity. Due to the physical barrier of MEA and formation of Al-rich AlxCoCrFeNi phase, the formation of the Mg-Al IMCs phase was effectively suppressed, which improved the shear properties of the joints. The material- microstructure-property relations was established in this work, which facilitated the development of laser welding technology for Mg and Al alloys.

Prediction of Weld Strength in Power Ultrasonic Spot Welding Process Using Artificial Neural Network (ANN) and Back Propagation Method

In this presented work, the employment of artificial neural network (ANN) connected with back propagation method was performed to predict the strength of joining materials that carried out by using ultrasonic spot welding process. The models which created in this study were investigated and their process parameters were analysed. These parameters were classified and set as input variables like for example applying pressure, time of duration weld and trigger of vibrating amplitude while weld strength of joining dissimilar materials (Al-Cu) is set as output parameters. The identification from the process parameters are obtained using number of experiments and finite element analyses based prediction. The results of actual and numerical are accurate and reliability, however its complexity has significant effect due to sensitive to the condition variation of welding processes. Therefore, the needed for an efficient technique like artificial neural network coupled with back propagation method is required to use the experiments as an input data in simulation of ultrasonic welding process, finding the adequacy of modeling process in prediction of weld strength and to confirm the performance of using mathematical methods. The results of the selecting non-linear models show a noticeable potency when using ANN with back propagation method in providing high accuracy compared with other results obtained by conventional models.

Mechanism and numerical simulation analysis of laser welding 5182 aluminum alloy/PA66 based on surface texture treatment

The direct connection of dissimilar materials is a hot topic in current research. 5182 aluminum alloy and 30 % glass fiber reinforced PA66 are two commonly used materials in automobile body production. The metal surface is pretreated before laser welding to improve the connection strength of metal and plastic. The influence of laser process parameters on the connection mechanism of dissimilar materials is studied, and the connection mechanism is further explained by numerical simulation of welding process. The results show that the laser input energy increases with the increase of laser power and the decrease of welding velocity. The laser input energy affects the melting of plastic and the filling effect of micro-structures. The filling effect of molten plastic on micro-structures is improved with the increase of laser input energy. The connection strength is increased from 951 N to 1341 N. The thermal decomposition of plastic will produce welding defects when the laser input energy is too high, which will be detrimental to welding strength.

Investigation of Laser Butt Welding of AISI 304L and Q235 Steels Based on Numerical and Experimental Analyses

The fiber laser butt welding of AISI 304L and Q235 low-carbon steel is performed in this study. An integrated heat source combined with an asymmetric double-ellipsoidal heat source and a cylindrical heat source is designed to perform the numerical simulation of the laser butt welding process. With the established numerical simulation model, the formation of the welded joint is studied by investigating the thermal process. The effects of the laser power and laser beam offset to the sides of the center of the welding gap on the welded joint shape and strength are experimentally investigated, and the optimum laser power and laser beam offset are determined via tensile strength and hardness tests of the weldment. The numerical simulation results based on the asymmetric heat source agree well with the experimental results and are applied to investigate the mechanisms for forming different welded joint shapes in AISI 304L and Q235 steels. The different thermal conductivity and melting temperatures of the two dissimilar metals result in the different shapes of the welded joint.

Variable profile heat source models for numerical simulations of arc welding processes

Numerical modeling of arc welding and correlated processes tend to be challenging, since they have complex physical phenomena. Several heat sources, with geometric parameters to be adjusted, have been developed to impose the energy input of the process. This study proposes two variable profile heat sources, with only two geometrical parameters, that intend to achieve good accuracy, regardless the welding process, base material and thickness of the welded plates. These sources are tested against GTAW and GMAW processes of butt joints of carbon and stainless steel plates with two different thicknesses. Numerical simulations are performed in ANSYS® APDL software, and performance of these new heat sources are compared with classical ones, namely the 3D Conical and the Double Ellipsoid. Weld profiles and thermal cycles from experiments are compared with numerical ones. Although all heat sources had difficulties to predict accurately results in cases of GMAW processes, numerical results of the new heat sources had equal or better agreement than the classical ones.

Atomic diffusion behavior near the bond interface during the explosive welding process based on molecular dynamics simulations

Based on the Hastelloy/stainless steel explosive-welded composite (the main elements are Ni and Fe respectively), this work investigated the diffusion behavior of main elements near the bond interface during the explosive welding process through molecular dynamics simulations and experiments. According to the characteristics of temperature and pressure of explosive welding process, the simulation of explosive welding process is classified into three stages, namely loading stage, unloading stage, and cooling stage. The diffusion behavior of the main elements (Ni and Fe) near the interface was investigated by two methods. The first one is to calculate the mean square displacement of the main elements. And the second one is to compare the system configurations and the results of radial distribution function at different stages. In the simulation, the thickness of the diffusion layer of the Vpx (the transverse velocity)= 0.2 km/s, Vpx= 0.4 km/s, Vpx= 0.6 km/s, Vpx= 0.8 km/s weldments are about 14, 20, 49, and 61 Å. The results show that the atomic diffusion near the interface mainly occurs in the unloading stage and the beginning of the cooling stage. Only when the melting occurs during these stages, the atoms of the bonding interface can diffuse obviously. In this experiment, the thicknesses of the diffusion layer at the wave peak and the vortex zone are about 20 µm and 230 µm respectively. This conclusion is verified by the results of experimental investigations and the references. Also, the diffusion layer thickness with the increasing the absolute value of Vpz (the longitudinal velocity) and Vpx, and the absolute value of Vpz can make a greater contribution to the thickness of the diffusion layer than that of Vpx. The thickness of the diffusion layer at the interface will be significantly increased if the melting occurred during the welding process.

Prediction of welding residual stress and distortion in multi-layer butt-welded 22SiMn2TiB steel with LTT filling metal

The objective of this study is to investigate the influence of low transformation temperature (LTT) filling metal on residual stress and distortion in multi-layer butt-welded 22SiMn2TiB steel. A three-dimensional thermal elastic–plastic finite element model is developed for LTT filling metals, and metallurgical phase transformation is taken into account to predict the martensite fraction of the weld metal. A thermodynamic-based method is employed to calculate martensite start temperature (Ms) and the influence of dilution on Ms is also considered. Volume change due to austenite transformation during heating and martensite transformation during cooling are coupled with the numerical simulation of welding process. The evolution of welding residual stress and welding distortion are both predicted. The simulation results revealed that the distortion of welding plate using LTT filling metal is much smaller than that using austenitic metal. In the weld zone, transverse residual stress is lower using austenitic filling metal, but longitudinal stress is much smaller using LTT filling metal. Longitudinal stress distribution for both LTT and austenitic filling metals is very high in the heat-affected zone, which is close to the yield stress of base metal. The LTT filling metal can not only guarantee the strength of welded joint for armor steel, but also reduce the welding distortion obviously, and the residual stress is also very low at the same time. The predicted temperature profiles and welding distortion are generally in good agreement with the experimental ones.

Humping Formation and Suppression in High-Speed Laser Welding.

Increasing welding speed can promote the productivity of laser welding. However, humping defects often occur, which limits the application of this strategy. The existing explanations for the humping formation remain vague, and mitigation and suppression methods are limited. In this research, high-speed imaging experiments and numerical simulation of the high-speed laser welding process are performed. Through careful examination, the humping phenomenon is explained. At high welding speed, the high-speed melt flow caused by recoil pressure is hindered by the solidified region in the melt pool, leading to the occurrence of a swelling. The swelling then grows, forming a valley in front of the swelling under the effect of surface tension. The solidification of the valley results in the occurrence of a second swelling. This process repeats and humping defect forms. Marangoni force and viscous force also have influence on this process. In addition, it is found that adding a Tungsten Inert Gas arc behind the laser beam can effectively suppress the humping.

Numerical simulation of ultrasonic vibration-enhanced friction stir welding process of dissimilar Al/Mg alloys

Numerical simulation of ultrasonic vibration-enhanced friction stir welding process of dissimilar Al/Mg alloys

Thermo-mechanical modelling of the Friction Stir Spot Welding process: Effect of the friction models on the heat generation mechanisms

Friction Stir Spot Welding involves complex physical phenomena, which are very difficult to probe experimentally. In this regard, the numerical simulation may play a key role to gain insight into this complex thermo-mechanical process. It is often used to mimic specific experimental conditions to forecast outputs that may be substantial to analyse and elucidate the mechanisms behind the Friction Stir Spot Welding process. This welding technique uses frictional heat generated by a rotating tool to join materials. The heat generation mechanisms are governed by a combination of sliding and sticking contact conditions. In the numerical simulation, these contact conditions are thoroughly dependent on the used friction model. Hence, a successful prediction of the process relies on the appropriate selection of the contact model and parameters. This work aims to identify the pros and cons of different friction models in modelling combined sliding-sticking conditions. A three-dimensional coupled thermo-mechanical FE model, based on a Coupled Eulerian-Lagrangian formulation, was developed. Different friction models are adopted to simulate the Friction Stir Spot Welding of the AA6082-T6 aluminium alloy. For these friction models, the temperature evolution, the heat generation, and the plastic deformation were analysed and compared with experimental results. It was realized that numerical analysis of Friction Stir Spot Welding can be effective and reliable as long as the interfacial friction characteristics are properly modelled. This approach may be used to guide the contact modelling strategy for the simulation of the Friction Stir Spot Welding process and its derivatives.

A semi-analytical method for the calculation of double-ellipsoidal heat source parameters in welding simulation

Structural integrity assessment of welded components requires the determination of residual stress and deformations induced by the welding process. The implementation of both a numerical static mechanical analysis and a thermal transient analysis is needed in order to accurately determine stress and strain fields. The most faithful representation of the heat flow provided by the welding torch in thermal simulations is realized with Goldak’s double ellipsoid, especially in case of MIG/MAG and combined TIG-MIG/MAG welding. The correct determination of the temperature trends during the welding process simulation is essential for the subsequent mechanical FEA. In order to obtain the above-mentioned temperature trends, some parameters must be determined ex ante, e.g., the geometrical characteristics of Goldak’s double ellipsoid. Generally, a large number of trial simulations must be performed in order to define these parameters. However, manual fitting is often complicated. To overcome such difficulties, in this work, it is reported a combined analytical and numerical method to determine the parameters using the genetic algorithm NSGA-II. First-attempt parameters are obtained through the solution of the Fachinotti’s analytical formulation. This first stage requires a restricted set of experimental data, such as weld pool extension and one temperature trend in the proximity of the seam. Afterwards, first-attempt parameters and experimental data are used to determine the final parameters by means of a set of numerical thermal simulations guided through the genetic algorithm optimization. To confirm the good-functioning of the method, a numerical analysis for the simulation of the experimental data and another FE simulation performed with the final results of the method are presented.

Modeling and simulation of friction stir welding process for AA6061-T6 aluminum alloy using finite element method

Friction Stir Welding (FSW) is a process of welding materials that generates heat through friction. Plastic deformation, nonlinear material movement, tool-to-structural evolution friction, and heat production from friction and plastic deformation all have an impact on FSW operation. In this paper, thermo-mechanical characteristics of aluminum alloy AA6061-T6 during the FSW process were simulated based on COMSOL® software using a finite element approach. A conceptual model was created to interpret the thermal and structural analyses. According to the obtained results, the temperature rises on the top and bottom surfaces as the axial force increases but decreases along the line perpendicular to the weld direction. The overall temperature decreases as the forward welding speed rises within the acceptable induced temperature range of the workpiece, while the axial force and rotational speeds stay stable.

Numerical Simulation of Laser Welding Process for Aluminum

Numerical Simulation of Laser Welding Process for Aluminum

Present Situation and Prospect of Welding Simulation Technology

In this paper, we mainly introduce the research status and development trend of welding numerical simulation technology. It is mainly reviewed that the simulation of molten pool flow field, welding temperature field and mechanical field, welding deformation and residual stress, hydrogen diffusion analysis, carbon migration of dissimilar steel welded joints, special welding process, microstructure of welded joints and grain growth process of welding heat affected zone. Then we discuss the special welding process simulation technology and special software for welding simulation. Finally, the development of welding numerical simulation technology in China are concerned.

Simulation of the electron beam welding process of a bimetallic ring by means of ANSYS

The article is devoted to modeling the process of electron beam welding in the manufacture of electric motors with a bimetallic ring used in biofuel preparation reactors. The main problem at the current stage of production is the choice of the technological mode of welding and the repeatability of the result. In this work, the authors simulate the welding of electric motors with a bimetallic ring under various technological modes in the ANSYS simulation environment in the process of electron beam welding. The result of the work will be a graphical representation of the temperature distribution on the surface of the product at various values of the technological parameters (electron beam current, welding speed and welding process time). Today, the choice of modes for a new technological process is carried out experimentally, which entails high material costs. The approach proposed by the authors allows, with minimal time and material costs, to select a technological mode for welding products from new alloys.

Large-Scale Welding Process Simulation by GPU Parallelized Computing

The computational design of industrially relevant welded structures is extremely time consuming due to coupled physics and high nonlinearity. Previously, most welding distortion and residual stress simulations have been limited to small coupons and reduced order (from three-dimensional [3D] to two-dimensional [2D]), or inherent strain approximations were used for large structures. In this current study, an explicit finite element code based on a graphics processing unit was utilized to perform 3D transient thermomechanical simulation of structural components during welding. Laser brazing of aluminum alloy panels as representative of automotive manufacturing scenarios was simulated to predict out-of-plane distortion under different clamping conditions. The predicted deformation pattern and magnitude were validated by laser scanning data of physical assemblies. In addition, the code was used to investigate residual stresses developed during multipass arc welding of a nuclear industry pressurizer surge nozzle and subsequent welding repair where a 3D simulation was necessary. Taking the experimental data as reference, the 3D model predicted better residual stress distribution than a typical 2D asymmetrical model. Stress evolution in welding repair was also presented and discussed in this study. The efficient numerical model made it feasible to use integrated computational welding engineering to simulate welding processes for large-scale structures.

Weld pool dynamics and joining mechanism in pulse wave laser beam welding of Ti-6Al-4V titanium alloy sheets assembled in butt joint with an air gap

A validated CFD model coupling the multiple phases and multiple physics was developed for the dynamic simulation of pulse wave laser welding (PWLBW) process of 1.2 mm-thick Ti-6Al-4V alloy sheets assembled in butt joint with a reserved air gap. A laser spot diameter of 700 μm was used to compensate for the energy loss with the clearance applied at 0.2 mm and therefore improve the gap bridging ability. The distributions and evolutions of temperature, velocity, phase interface and weld pool dimensions were characterized and discussed to reveal the joining mechanism and the heat and flow behaviors during welding. The results show that the liquid bridges firstly occur in the middle height of sheets as the welding begins, and rapidly extend to the whole thickness with the increasing heat input. The reduction on laser power causes the rebounding of keyhole surface and the backfilling of molten metal. The keyhole closes at root surface and rebounds completely in 2 microseconds, leading to the merging of liquid bridges, bottom-up moving of high temperature area, and temporarily enlargement on weld pool size at root surface. During the pulse interval, the weld pool volume shrinks significantly and the molten metal slows down from Marangoni vortexes to thermal buoyance flows. The proposed process parameters allow an air gap accounting for 16.67% of specimen thickness and result in a well-formed and defect-free weld bead.