Modeling Of Welding Process Research Articles

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.

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.

Assumptions for Modeling of the Hot Plate Welding Process Considering the Automatic Welding Machine Design

Drive and conveyor belts are widely used in processing and mining industries. One of their types, which are often used in light-duty applications, are the belts with round cross-section and several millimeters in diameter. They are often made of thermoplastic elastomers, in particular ofweldable polyurethane. Their production process requires to carry out the operation of joining the belt ends to obtain a closed loop. This operation is often carried out by means of butt welding utilizing the hot plate method. This process is often performed by hand using simple tools. Authors took an effort to design the automatic welding machine, which can make durable joints of this type automatically. The design works comprise control system configuration which calls for identifying the technological parameters of the process, being the reason for undertaking the research works on the hot plate welding process. The main aim of this activity was to formulate of the mathematical model of the hot plate welding of round drive belts which is necessary to identify the process parameters and the correlations between them. In the paper, the assumptions for the hot plate welding process modeling were presented. During their formulating, technical conditions were taken into consideration resulting from some of the characteristics observed in an automatic welding device prototype which had been implemented for industry production.

Modeling analysis and optimization of temperature curve of welding furnace

Reflux welding is widely used in SMT (surface patch technology) During this production process, the quality of the product is essential to maintain the temperature and the furnace speed required by the process. The furnace temperature curve in the furnace is an important form of reaction welding process. In order to improve the process efficiency of the return furnace, the heating welding process model is established based on the Fourier heat conduction law,1 D heat conduction model and Newton cooling law and draws the furnace temperature curve model. Then, the upper boundary of the conveyor speed using the boundary analysis and multiple target planning, and further explore the research and optimization direction of subsequent process flow. At the same time, this paper examines and analyzes the modeling process and results, and effectively demonstrates the scientific nature and accuracy of the model. Finally, the paper analyzes the significance of the above model and research in chip processing.

Validated Multi-Physical Finite Element Modelling of the Spot Welding Process of the Advanced High Strength Steel DP1200HD.

Resistance spot welding (RSW) is a common joining technique in the production of car bodies in white for example, because of its high degree of automation, its short process time, and its reliability. While different steel grades and even dissimilar metals can be joined with this method, the current paper focuses on similar joints of galvanized advanced high strength steel (AHSS), namely dual phase steel with a yield strength of 1200 MPa and high ductility (DP1200HD). This material offers potential for light-weight design. The current work presents a multi-physical finite element (FE) model of the RSW process which gives insights into the local loading and material state, and which forms the basis for future investigations of the local risk of liquid metal assisted cracking and the effect of different process parameters on this risk. The model covers the evolution of the electrical, thermal, mechanical, and metallurgical fields during the complete spot welding process. Phase transformations like base material to austenite and further to steel melt during heating and all relevant transformations while cooling are considered. The model was fully parametrized based on lab scale material testing, accompanying model-based parameter determination, and literature data, and was validated against a large variety of optically inspected burst opened spot welds and micrographs of the welds.

Increasing fatigue crack initiation life in butt-welded UIC60 rail by optimization of welding process parameters

In this work, to reduce the fracture in butt-welded rail under service loads, a numerical study is carried out to estimate the crack initiation life. For this purpose, the J-S model in terms of the critical plane method is used. To increase the fatigue life of the welded joint, considering the amount of fractured butt welded joints in the railway of the Iranian network, the important variables of the flash-butt welding process are optimized. To this end, the welding process modeling in Abaqus is converted to Python code, and by using a coupled procedure utilizing Matlab, the optimization process is performed by the imperialist competitive algorithm (ICA). The capability of each governing variable on increasing crack initiation life is discussed.

Using Hybrid Artificial Neural Network and Particle Swarm Optimization Algorithm for Modeling and Optimization of Welding Process

This study addresses a hybrid procedure used for modeling and optimization of gas tungsten arc (GTA) welding process of AL5052 alloy. There are different process input parameters among which welding current ([Formula: see text], frequency ([Formula: see text], welding speed ([Formula: see text], and gap ([Formula: see text] are the most important ones considered in GTA welding process. Furthermore, heat affected zone (HAZ) is considered as the most important quality measure of the process. To gather the required data for the modeling and optimization purpose, design of experiments (DOE) approach has been used. Image processing technique is used to take accurate measurements of HAZ values. In order to determine the relationship between process input variables and output measures, artificial neural networks (ANNs) have been used. Then, the trained ANNs have been used to find the optimal value of the outputs using particle swarm optimization (PSO) algorithm. Experiments have been done to verify the optimal levels of the input parameters. Verification results demonstrate that the proposed ANN-PSO procedure is quite efficient in modeling and optimization (with about 4% error) of GTA welding process.

Numerical modeling and simulation for laser beam welding of ultrafine-grained aluminium

Laser beam welding of aluminium offers huge potential for a wide variety of welding of different thickness parts with the method of thermal conductivity due to the relatively high difference between melting temperature and evaporation. However, due to the high melting temperature and good thermal conductivity of this light metal, the temperature gradients during the welding process are usually high, causing residual stresses in the weld, which can lead to undesirable deterioration of the weld pool properties and the quality of the process. Physical modelling and simulations of the laser welding process are powerful tools for gaining a fundamental understanding of the technological process. They are also a suitable tool for preliminary assessment of the intervals in which the real preliminary experiments for process optimization should take place. This work is devoted to the numerical modelling of the process of welding ultrafine-grained aluminium using a fibre laser. A three-dimensional model of the welding process was created, using the finite element method implemented in the program ABAQUS. The temperature fields at depth z and on the surface x, y in the welded samples is determined. The temperature change as a function of time for different coordinates of the weld is also analysed. During numerical calculations, the power, machining speed and diameter of the workplace are variable. The obtained results are compared with real experiments conducted in the laboratory by other researchers.

Investigations on Joining of High Density Poly Ethylene Sheets using Resistance Welding Technique

As a result of growing potential for high performance applications, parts made of HDPE materials is gaining greater interest for industry. Hence, the studies on joining of HDPE has got much significance. In this work, resistance welding of HDPE sheets was performed focusing on the governing set of parameters, current, pressure and time. Design of experiment (DOE) is done using full factorial design. The Analysis of Variance (ANOVA) was done with shear strength of weld as main parameter with the assistance of MINITAB software. Optimum parameters were identified in the study were medium level parameters produced good strength and better finished welded samples. Microstructure taken through Scanning electron microscopy (SEM) was supportive for this observation as there was a uniform flow of HDPE material without any void around the implant SS mesh for the best weld condition. The Finite element (FE) modeling of the resistance welding process was also performed using ANSYS to predict the thermal distributions occurring during the process depending on different levels of current and time inputs.

Numerical simulation of arc, metal transfer and its impingement on weld pool in variable polarity gas metal arc welding

• A unified numerical model involving arc, droplet and molten weld pool for VP-GMAW process is presented. • The heat transfer behavior and driving forces of metal formation and falling on the weld pool is quantitatively discussed. • At the same welding current during pulse cycle, the arc temperature in EN current phase is greater than EP current phase. • The arc plasma generated at EN current phase shows a constricted arc shape at the electrode tip. • The phenomenon of finger-like shape penetration observed during experiment is simulated and explained. A unified numerical model of the variable polarity gas metal arc welding process is developed based on the solution of magnetohydrodynamic equations within the framework of the phase-field algorithm. The droplet formation, necking, detachment, transfer through the arc plasma, and impingement onto the weld pool are investigated at different electrode positive (EP) and electrode negative (EN) regions of the current pulse regime under the condition of one droplet per pulse. The current density, electromagnetic force, surface tension, transient melt-flow velocity, and Joule heating effects are calculated. The numerical results indicate that the arc plasma generated in the EN current phase has a constricted arc shape at the electrode tip compared with the typical bell shape arc in the EP current phase. At the same welding current during the pulse cycle, the arc plasma temperature in the EN current phase is greater than that in the EP current phase. The model shows that before the droplet detaches, the surface tension forces are dominant, whereas during the EP current phase, the electromagnetic forces strongly intensify along the liquid bridge, thereby causing droplet detachment. In addition, the phenomenon of finger-like shape penetration due to the momentum transferred by a falling droplet to the bottom of the weld pool is simulated. The predicted results well agree with the high-speed images and weld pool parameters, accordingly validating the formulated model.

Analysis of Temperature Field Dynamics in Electrofusion Welding of Polymer Pipes at Low Temperatures

Technique for determining technological parameters of electrofusion welding of polyethylene pipes at ambient temperatures below standard, based on analysis of temperature field dynamics in heat-affected zone, is proposed. Mathematical model of thermal welding process used in calculations is presented, considering temperature dependence of phase transformation heat and crystallinity degree of polymer material. Results of determining parameters for electrofusion welding of polyethylene pipes and welding of branch saddle topload to polyethylene pipe are presented. Effectiveness of calculated determination of welding parameters is confirmed by tests of welded joints made according to proposed welding technology at naturally low temperatures.

Study on prediction method of crack propagation in absorber weld by experiment and simulation

As an important equipment for purifying crude oil and natural gas in energy industry, absorber is subjected to harsh working environment of high stress and severe corrosion. Especially, weld is the weak region of the absorber, which faces significant risk of crack propagation due to residual stress caused by the welding process, working pressure and temperature. Meanwhile, crack propagation in absorbers with high pressure, high temperature and toxic media can often cause disastrous consequences. Therefore, to solve this problem, a systematic method considering welding, heat treatment and working process is presented in this paper to predict crack propagation completely in the weld. In the case, based on actual conditions, a finite element model (FEM) of welding process considering transient heat transfer and heat radiation for residual stress field analysis is established to obtain the far-field stress for cracks. Then, the detailed analysis of stress field and stress intensity factor (KI) under the obtained far-field stress at the crack tip is carried out through the method of integrating the strain energy density (SED) in the crack tip region. Finally, experiments of fracture toughness (KIC) of undamaged weld specimens and post-corrosion weld samples are carried out to compare with KI obtained by FEM and evaluate the safety of existing cracks. The method presented in this paper is a complete system that can provide a universal technological basis for crack propagation prediction and safety assessment of pressure vessel.

Statistical modeling and optimization of the resistance welding process with simultaneous expulsion magnitude consideration for high-strength low alloy steel

In this investigation, the regression analysis together with the desirability function approach was involved to optimize the resistance welding parameters for the high-strength steel HSLA 420. The Box-Behnken experimental design (BBD) was employed for the control factors of welding time, welding current, and electrode pressure. The values of nugget diameter, ultimate peak load, maximum displacement, and absorption energy were identified and processed using the approach of multiple-objective optimization based on ratio analysis (MOORA). The weight loss of the base metal before and after welding was measured and computed to estimate the welding expulsion magnitude. The calculated statistical parameters displayed that the welding current had the most momentous influence on the welding quality and welding expulsion. The welding joints free of expulsion with sufficient mechanical properties can be achieved at the welding current of 8.4 kA, electrode pressure of 0.5 MPa, and welding time of 13 cycles.

Математическое моделирование распределения энергии при вводе в материал изделия луча в процессе электронно-лучевой сварки

Modeling of electron beam welding processes is one of the most important parts of applied research, because full-scale experimental investigations are either expensive or highly labor intensive. The problem of modeling the temperature fields at the electron beam entering stage during welding is considered. The aim of the study is to simplify the adjustment of the electron beam welding process technological parameters and to elaborate and develop more efficient control algorithms through replacing full-scale experiments by model ones. The mathematical body of the proposed solutions is constructed using the theories of thermal and welding processes, based on which the energy distribution mathematical models are developed. For practically implementing the computations, an algorithmic support is presented that allows the mathematical models to be applied in modern modeling systems, such as Matlab, Comsol Multiphysics, and Ansys. Apart from supplementing the set of existing mathematical models of the electron beam welding process, the obtained models for calculating the temperature in the beam entering area widen their application for calculating and optimizing the welding process, taking into account the workpiece temperature in the electron beam entering area. By using the proposed solutions, several numerical experiments were carried out for a workpiece made of VT-14 titanium alloy and two pieces of different thickness made of AMg-6 aluminum alloy. The obtained temperature fields and the rms values of process parameters are almost identical with the results of previously conducted full-scale studies.

On the mechanisms involved in the tensile strength of a dissimilar Ti6Al4V/316L laser welded assembly

The aim of the present work is to analyze the thermomechanical behavior of dissimilar laser seams by means of FE modeling. The case of a Ti6Al4V/316L assembly with vanadium insert was considered. Effective mechanical properties of the main materials and cords were first estimated from NHT measurements. Modeling of the double pass laser welding process was performed first by considering shrinking of the two weld seams during manufacturing, to get the residual stress state in the welded assembly. Modeling of the tensile test was performed in a second step to study the assembly behavior during loading. In these modeling results, the mesh was the cross-section of the micrograph of the assembly itself. The corresponding stress/strain curve was calculated and results were reported for the residual stress state after manufacturing as well as a stress state close to the Ultimate Tensile Strength.

Effect of arc breaks and short circuits on lack of fusion formation at sidewalls of groove during multi-pass weaving of pipelines

To evaluate the effect of the short-time arc breaks along the side-walls of grove during multi-pass welding virtual study of this effect is performed using deterministic mathematical model of arc welding process. It is established that breaks in arc burning lead to the appearance of craters, which may not be remelted during the subsequent pass. It is shown that the effect of the duration of the arc breaks on the craters depth increases with increase in the amplitude and period of oscillations. The effect of breaks is more noticeable if they occur when approaching the groove face than if they occur when moving from the groove face to the center of the pass. When analyzing the welding monitoring data, it is necessary to take into account not only the arc power, but also the parameters of transverse oscillations of the torch, including the phase of arc breaks relative to these oscillations.

Parametric Study Of Friction Stir Spot Welding (FSSW) For Polymer Materials Case Of High Density Polyethylene Sheets: Experimental And Numerical Study

Friction stir spot welding (FSSW) is a very important part of conventional friction stir welding (FSW) which can be a replacement for riveted assemblies and resistance spot welding. This technique provides high quality joints compared to conventional welding processes. Friction stir spot welding (FSSW) is a new technology adopted to join various types of metals such as titanium, aluminum, magnesium. It is also used for welding polymer materials which are difficult to weld by the conventional welding process. In various industrial applications, high density polyethylene (HDPE) becomes the most used material. The parameters and mechanical properties of the welds are the major problems in the welding processes. In this paper, we have presented a contribution in finite element modeling of the friction stir spot welding process (FSSW) using Abaqus as a finite element solver. The objective of this paper is to study the HDPE plates resistance of stir spot welding joints (FSSW). First, we show the experimental tests results of high-density polyethylene (HDPE) plates assembled by friction stir spot welding (FSSW). Three-dimensional numerical modeling by the finite element method makes it possible to determine the best representation of the weld joint for a good prediction of its behavior. Comparison of the results shows that there is a good agreement between the numerical modeling predictions and the experimental results.

Optimization of A-TIG Welding Process Using Simulated Annealing Algorithm

Flux-assisted tungsten inert gas welding process, also known as activated tungsten inert gas (A-TIG) welding, is extensively used in order to improve the performance of the conventional TIG welding process. In this study, the orthogonal array Taguchi (OA-Taguchi) method, regression modeling, analysis of variance (ANOVA) and simulated annealing (SA) algorithm have been used to model and optimize the process responses in A-TIG welding process. Welding current (I), welding speed (S) and welding gap (G) have been considered as process input variables for fabricating AISI316L austenitic stainless steel specimens. Depth of penetration (DOP) and weld bead width (WBW) have been taken into account as the process responses. In this study, SiO2, nano-particle has been considered as an activating flux. To gather required data for modeling, statistical analysis and optimization purposes, OA-Taguchi based on the design of experiments (DOE) has been employed. Then the process responses have been measured and their corresponding signal-to-noise (S/N) ratio values have been calculated. Different regression equations have been applied to model the responses. Based on the ANOVA results, the most fitted models have been selected as an authentic representative of the process responses. Furthermore, the welding current has been determined as the most important variable affecting DOP and WBW with 68% and 88% contributions, respectively. Next, the SA algorithm has been used to optimize the developed models in such a way that WBW is minimized and DOP is maximized. Finally, experimental performance evaluation tests have been carried out, based on which it can be concluded that the proposed procedure is quite efficient (with less than 4% error) in modeling and optimization of the A-TIG welding process.

Modelling the power system of a resistance welding machine electrical complex

The article has investigated the operation of the electrical complex of a resistance welding machine with thyristor current regulation. The model of the resistance welding process is presented as a control object with known input parameters, output parameters and external disturbances. The input parameters are the following: the preset welding current, a mode parameter (hard, soft), the prearranged welding time, the preset compression force, etc. The output parameters related to welding quality are the following: welding current, electrodes voltage, welding energy, resistance of the section «electrode-the part-electrode». The output parameters related to the indicators of ensuring electromagnetic compatibility of the electrotechnical complex with the electrical network are the following: the current consumed from the electrical network, reactive power consumed from the network, PF (power factor), THDI (current’s total harmonic distortion), load asymmetry coefficient. The external disturbing factors, the effect of which leads to the deterioration of the quality of welded joints are the following: fluctuations of the supply voltage, change of resistance of the welding circuit caused by the ferromagnetic masses, change of the welding circuit resistance due to its heating and/or wear, wear of the electrodes, change of the state of the welding parts surfaces, welding current bypass. The influence of disturbing factors on the welding process has been analyzed and it has been confirmed that in order to ensure a high-quality welded joint, it is necessary to stabilize the energy released in the welding contact. A model has been developed that simulates a change in the resistance of the welding circuit during the welding cycle. A model of the energy stabilization subsystem has been developed; it calculates the energy that is released in the welding contact and, when it reaches the preset value, the machine is turned off. To calculate the required energy, the heat balance equation was used, that takes into account both the useful energy, spent on the creation of the welded joint and the energy losses due to heat removal to the electrodes, to the welded parts, and convective heat transfer (which is usually neglected). The obtained results of the useful energy calculation take into account the latent heat of fusion. As a result of the simulation, it has been shown that the release of the necessary amount of energy, given welding current, results in an increase in the welding duration: taking into account the changes in resistance during welding, the welding duration grows up to 20%, taking into account the voltage fluctuations (-15%) the welding duration grows up to 30%. Under the influence of both disturbing factors, the welding duration can increase up to 60%, provided that the necessary welding quality is ensured. Thus, it has been shown that besides the magnitude of the welding current, it is possible to adjust the duration of welding, providing the necessary energy in the welding contact (taking into account the restrictions on the duration of current)

Modelling resistance welding of thermoplastic composites with a nanocomposite heating element

Electrically conductive nanocomposite heating elements are being developed as a complement to traditional carbon fibre or stainless steel heating elements in resistance welding of thermoplastic composites. Here we present the development of a finite element model of the resistance welding process with these new heating elements, from which we establish a process window for high quality welded joints. The finite element model results were validated experimentally and a lap shear strength improvement of 28% is reported relative to previously published results. Fractography analysis of the broken joints revealed a thin-layer cohesive failure mode due to the brittleness of the nanocomposite heating elements.