An Improved Method of Capturing the Surface Boundary of a Ti-6Al-4V Fusion Weld Bead for Finite Element Modeling (original) (raw)
Linking a CFD and FE analysis for Welding Simulations in Ti-6Al-4V
Finite element (FE) modelling of fusion welding methods has become an established numerical tool used by high-value manufacturing industries and academic communities, largely due to its capabilities to predict residual stress and distortion. However, a major drawback of this type of approach is the requirement to perform a test weld at the relevant process parameters, geometry and material to understand the size and shape of the weld pool formed. With this knowledge a priori the FE model can then be used to best-fit the thermal cycles to the part, and from the thermal field predict the mechanical response to this thermal loading. This well-established method of FE simulation reduces the predictive capabilities of the model. Thus, an improved method of using a different modelling strategy to feed the thermal cycles in to the FE model is desirable. A computational fluid dynamics (CFD) modelling capability has been developed which is able to predict not just weld pool shape, but using real physical phenomena such as surface tension and thermo-capillary forces, buoyancy forces and interfacial phenomena between solid-liquid and liquid-gas phases, can predict thermal fluid flow lines within the molten region, the presence of regions susceptible to porosity and the formation of the keyhole phase, containing metallic vapor. Using simplistic Cartesian coordinates the fusion boundary can be extracted from CFD analysis for entry in to an FE model for structural analysis in terms of residual stress and distortions. Therefore, the modelling approach predicts both fluid type and structural type properties of the transient welding operation. Introduction The titanium alloy Ti-6Al-4V remains by far the most commonly used titanium alloy in high-technology manufacturing [1] , with particularly widespread use in the aerospace and aero-engine industries, owing largely to its excellent strength : weight ratio [2]. In the manufacture of modern gas-turbine jet-engines, titanium alloys are used to manufacture both rotating and stationary components, all of which are subject to very closely controlled manufacturing tolerances. Indeed, given the strict guidelines for the use of newer-generation materials in to a jet-engine component, there remains a distinct advantage in retaining the use of fully certified materials from engines of previous generations, such as Ti-6Al-4V. Components including turbine discs and blades, the compressor drum and the fan remain commonly manufactured using Ti-6Al-4V. The complex geometries of aero-engine components lead to the requirement for welding techniques to join parts structurally. Welding methods used as standard within the aerospace industry include older arc-type welds such as tungsten inert-gas (TIG) welding [1] , as well as newer beam-type processes such as laser and electron-beam welding [3]. The underlying physical phenomena associated with beam processes are more complex as the material experiences localized vaporization in these high power-density processes.
Mathematical model of bead profile in high deposition welds
Journal of Materials Processing Technology, 2015
Mathematical models of reinforcement and penetration profile in high deposition welds produced by multiple-wire processes are presented. A practical approach for assessment of shape and size of weld bead is introduced wherein characteristic coefficients (α i) of parametric equations y = f (α i , x) are expressed as functions of process parameters such as welding current, speed, and voltage, and they are determined by calibration of model with experimental observations using a heuristic technique. The validity of new model is demonstrated through a case study presentation on twin-wire welding. Compared to a semi-elliptical reinforcement and a cosine/parabolic penetration profiles in single-wire welds, an elliptical segment and a composite trigonometric function, respectively, are found more appropriate to represent multiple-wire welds. The effects of process parameters on bead profile and weld bead dilution for straight and reverse polarities over a wide range of process parameters are evaluated. The developed models explain effect of welding parameters on weld bead shape and weld cooling time, thus, apt for determining dimensions of heat source in modelling of welding processes.
High speed fusion weld bead defects
Science and Technology of Welding and Joining, 2006
A comprehensive survey of high speed weld bead defects is presented with strong emphasis on the formation of humping and undercutting in autogenous and non-autogenous fusion welding processes. Blowhole and overlap weld defects are also discussed. Although experimental results from previous studies are informative, they do not always reveal the physical mechanisms responsible for the formation of these high speed weld bead defects. In addition, these experimental results do not reveal the complex relationships between welding process parameters and the onset of high speed weld bead defects. Various phenomenological models of humping and undercutting have been proposed that were based on observations of events in different regions within the weld pool or the final weld bead profile. The ability of these models to predict the onset of humping or undercutting has not been satisfactorily demonstrated. Furthermore, the proposed formation mechanisms of these high speed weld bead defects are still being questioned. Recent welding techniques and processes have, however, been shown to be very effective in suppressing humping and undercutting by slowing the backward flow of molten metal in the weld pool. This backward flow of molten weld metal may be the principal physical phenomenon responsible for the formation of humping and undercutting during high speed fusion welding.
A transient finite element simulation of the temperature and bead profiles of T-joint laser welds
Materials & Design, 2010
Laser welding is a high power density welding technology, which has the capability of focusing the beam power to a very small spot diameter. Its characteristics such as high precision and low and concentrated heat input, helps in minimizing the micro-structural modifications, residual stresses and distortions on the welded specimens. In this study, finite element method (FEM) is adopted for predicting the bead geometry in laser welding of 1.6 mm thick AISI304 stainless steel sheets. A three-dimensional finite element model is used to analyze the temperature distribution in a T-joint weld produced by the laser welding process. Temperature-dependent thermal properties of AISI304 stainless steel, effect of latent heat of fusion, and the convective and radiative boundary conditions are included in the model. The heat input to the model is assumed to be a 3D conical Gaussian heat source. The finite element code SYSWELD, along with a few FORTRAN subroutines, is employed to obtain the numerical results. The T-joint welds are made using a Nd:YAG laser having a maximum power of 2 kW in the continuous wave mode. The effect of laser beam power, welding speed and beam incident angle on the weld bead geometry (i.e. depth of penetration and bead width) are investigated. Finally, the shapes of the molten pool predicted by the numerical analysis are compared with the results obtained through the experimentation. The comparison shows that they are in good agreement.
Transactions of the Indian Institute of Metals, 2020
In the present paper, multi-response mathematical model is established for prediction of weld bead geometry in cold metal transfer (CMT), MIG pulse synergic (MIG P), and MIG manual (MIG M) welding of AA6061-T6 using ER4043 (AlSi5%) as a filler material. Central composite face-centered design under response surface methodology is employed to develop the design matrix for conducting the experiments. The developed model is employed in finding the optimal process parameters for good weld bead aesthetics. Current (I) and welding speed (S) are opted as input process parameters for response output such as penetration, dilution, and heat input. This model is proficient to forecast the main effects and interactive effects of two factors of the opted welding process parameters. Results show that higher current values with low welding speeds result in deeper penetration, high amount of dilution with higher heat input, and vice versa. With lower heat input, CMT has high dilution and penetration with respect to MIG pulse synergic and standard MIG welding. Repeatability of CMT process is much higher as compared to the other two processes. The optimal process parameters are 92.518 A and 7.50 mm/s for CMT, 109.418 A and 10.873 mm/s for MIG P, and 110.847 A and 11.527 mm/s for MIG M with 61.11%, 68.80%, and 72.6% desirability, respectively. Predicted output values generated from regression model equation obtained from welding process parameters are very close and sometimes overlaid on actual output that obviously demonstrates the suitability of the second-order regression equations. A good amount of penetration and dilution with low heat input is required for better joint efficiency. Keywords Weld bead geometry Á Bead on plate Á CMT Á MIG pulse synergic Á MIG manual and mathematical modeling
Materials Testing, 2024
The primary aim of this study is to analyze the influence of inter-pulse tungsten inert gas (IP-TIG) welding parameters (peak current, inter-pulse current, and inter-pulse frequency) on weld bead geometry, tensile properties, and microstructure of Ti6Al4V alloy joints for gas turbine applications. IP-TIG welding principally featured by magnetic arc constriction and pulsing was employed to overcome the high heat input problems in TIG welding of thin Ti6Al4V alloy sheets such as wider bead and HAZ, coarsening of beta grains, inferior ductility, distortion of joints, and atmospheric contamination which significantly deteriorates the mechanical performance of welded sheets. The tensile properties and microhardness of IP-TIG joints were evaluated and correlated to the microstructural features. The microstructural features were analyzed using optical microscopy. The fractured surfaces of tensile specimens were studied using scanning electron microscopy. Results showed that the Ti6Al4V alloy joints developed using peak current of 50 A, interpulse current of 30 A, and inter-pulse frequency of 20 kHz exhibited greater strength, hardness and elongation. It showed greater tensile strength of 1030 MPa, yield strength of 981 MPa, and elongation of 10 % and FZ microhardness of 391 HV 0.2. It is mainly due to the development of refined grains in fusion zone (FZ).
Influence of Welding Process Parameters on Bead Geometry-A Review
2017
Surfacing techniques are developed to impart desirable properties like corrosion and wear resistance to low cost substrates like low carbon steels. Weld surfacing is capable of processing prefabricated and worn-out components. The various welding parameters influence the heat input, bead geometry and occurrence of weld defects. This paper briefly looks into various methods adapted to model, regulate and control weld surfacing techniques. The knowledge on effects of welding process parameters, percentage of overlap, inter-pass temperature, pulse characteristics, oscillation methods and control techniques is helpful to tailor the properties of the deposits. This review is mainly focused on selected welding techniques that can be readily and economically adopted for surfacing process.
Modeling of weld bead geometry on HSLA steel using response surface methodology
The International Journal of Advanced Manufacturing Technology, 2016
With increasing requirements of higher strength to low weight ratio materials, high-strength low-alloy (HSLA) steel has achieved higher commercial importance. Plasma arc welding has the capability to join metals without edge preparation, weldment in a single pass and minimum angular distortion. Due to these embedded capabilities, plasma arc welding is preferred over conventional joining processes for HSLA steel applications involving part thickness greater than 3 mm. The quality of plasma arc-welded joints is highly dependent on input process parameters. This paper aims to develop empirical models for the prediction of weld bead geometry including front bead height, back bead height, front bead width, and back bead width. A series of tests were conducted to investigate the effect of four input process parameters including current, voltage, welding speed, and plasma gas flow rate on weld bead geometry using a face-centered central composite design. The confirmation experiments and ANOVA results validated the models within 95 % accuracy. Current was found to be the most influential factor affecting the weld bead geometry followed by speed. Furthermore, current and speed and speed and gas flow rates were identified as most influencing interaction factors. The innovation in this research is the empirical modeling of weld bead geometry for HSLA using plasma arc welding.
Numerical Prediction of Weld Bead Geometry in Plasma Arc Welding of Titanium Sheets Using COMSOL
Plasma Arc Welding (PAW) is one of the important arc welding processes used in electronics, medical, automotive and aerospace industries due its high accuracy and ability of welding any hard materials. Though PAW is more complex and requires more expensive equipment compared to other commercial arc welding processes, it finds application in automotive sectors. In automotive applications, titanium metal is used particularly in motorcycle racing, where weight reduction is critical while maintaining high strength and rigidity. Titanium is in the group of reactive metals, which means that they have a good affinity for oxygen and readily forms an oxide layer leads to oxygen embrittlement. Therefore, the welding of titanium sheets is still an emerging technology in automotive sectors. The present investigation deals with the numerical simulation of plasma arc welding of 2 mm thick Ti-6Al-4V alloy using Finite Element code COMSOL. A Modified Three Dimensional Conical (MTDC) heat source model and a newly developed heat source model are considered for performing the numerical simulation to predict the temperature distribution on thin sheets of titanium alloy. The temperature dependent material properties of Ti-6Al-4V such as thermal conductivity, specific heat and density are used for performing the numerical analysis. Based on the results, it is observed that the predicted weld bead geometry from the temperature distribution plots using newly developed heat source model is in good agreement with the corresponding experimental result.
Optimization of Bead Geometry in CO2 Laser Welding of Ti 6Al 4V Using Response Surface Methodology
Engineering, 2011
In the presented study, the laser butt-welding of Ti 6Al 4V is investigated using 2.2 kw CO 2 laser. Ti 6Al 4V alloy has widespread application in various fields of industries including the medical, nuclear and aerospace. In this study, Response Surface Methodology (RSM) is employed to establish the design of experiments and to optimize the bead geometry. The relationships between the input laser-welding parameters (i.e. laser power, welding speed and focal point position) and the process responses (i.e. welded zone width, heat affected zone width, welded zone area, heat affected zone area and penetration depth) are investigated. The multi-response optimizations are used to optimize the welding process. The optimum welding conditions are identified in order to increase the productivity and minimize the total operating cost. The validation results demonstrate that the developed models are accurate with low percentages of error (less than 12.5%).
Ti–6Al–4V TIG Weld Analysis Using FEM Simulation and Experimental Characterization
Iranian Journal of Science and Technology, Transactions of Mechanical Engineering, 2019
This study involves thermal, metallurgical and mechanical analysis during tungsten inert gas welding of Ti-6Al-4V alloy aiming at optimizing the welding current to enhance the mechanical properties. Firstly, a 3D transient FEM simulation of TIG Ti-6Al-4V weld using ABAQUS software, based on a Gaussian distribution of power density in space, has been built to predict the effect of welding current on the heat input, weld bead geometry, temperature and residual stresses distribution across the welding line. Secondly, a validation of FEM with the experimentally measured temperature distribution and welding bead geometries has been presented. Finally, experimental study of the effect of TIG welding current, the suitable range predicted from FEM, on the microstructure, hardness and tensile strength of 12-mm-thick alloy plate is discussed. Using FEM, the suitable range of welding current was predicted to be 130-170 A. There was a close agreement among the experimental results and the FEM simulation data. It has been found that low welding current of 130 A results in high tensile strength and hardness of the welding joint. This is attributed to low heat input, high cooling rate and the formation of a fine grain structure containing martensite-phase with low values of residual stresses.
Optimization of Bead Geometry in CO2 Laser Welding of Ti 6Al 4V Using Response Surface Methodology
balance, 2011
In the presented study, the laser butt-welding of Ti 6Al 4V is investigated using 2.2 kw CO 2 laser. Ti 6Al 4V alloy has widespread application in various fields of industries including the medical, nuclear and aerospace. In this study, Response Surface Methodology (RSM) is employed to establish the design of experiments and to optimize the bead geometry. The relationships between the input laser-welding parameters (i.e. laser power, welding speed and focal point position) and the process responses (i.e. welded zone width, heat affected zone width, welded zone area, heat affected zone area and penetration depth) are investigated. The multi-response optimizations are used to optimize the welding process. The optimum welding conditions are identified in order to increase the productivity and minimize the total operating cost. The validation results demonstrate that the developed models are accurate with low percentages of error (less than 12.5%).
Prediction and Optimization of Weld Bead Geometry
VOLUME-8 ISSUE-10, AUGUST 2019, REGULAR ISSUE, 2019
Bead geometry plays very important role in predicting the quality of weld as cooling rate of the weld depends on the height and bead width, also bead geometry determines it’s residual stresses and distortion. Weld bead geometries are outcomes of several welding parameters taken into consideration. If arc travel is high and arc power is kept low it will produce very low fusion. If electrode feed rate is kept higher width is also found to be on higher side which makes bead tto flat. Also, the parameters like current, voltage, arc travel rate, polarity affects weld bead geometry. Hence, this paper uses techniques like ANN, linear regression and curvilinear regression for predictions of weld bead geometry and their relations with different weld parameters. I. INTRODU
scirp.org
In the presented study, the laser butt-welding of Ti 6Al 4V is investigated using 2.2 kw CO 2 laser. Ti 6Al 4V alloy has widespread application in various fields of industries including the medical, nuclear and aerospace. In this study, Response Surface Methodology (RSM) is employed to establish the design of experiments and to optimize the bead geometry. The relationships between the input laser-welding parameters (i.e. laser power, welding speed and focal point position) and the process responses (i.e. welded zone width, heat affected zone width, welded zone area, heat affected zone area and penetration depth) are investigated. The multi-response optimizations are used to optimize the welding process. The optimum welding conditions are identified in order to increase the productivity and minimize the total operating cost. The validation results demonstrate that the developed models are accurate with low percentages of error (less than 12.5%).
European Mechanical Science, 2018
Bead penetration depth plays a significant role on the quality and integrity of welds, as deeper penetration can improve the strength and load bearing capacity of weldments in service condition. Based on Design of Experiment (DOE), an experimental design matrix having thirteen (13) center points, six (6) axial points and eight (8) factorial points resulting in twenty (20) experimental runs was generated for TIG welding current, voltage, gas flow rate (L/min) and temperature. Maximum bead penetration of 8.44 mm was obtained from the FEM simulation with corresponding input variables of 190 A, 19 V, 18 L/min and 298.44 o C compared to maximum bead penetration of 7.942 mm obtained from the welding experimentation with corresponding input variables of 155 A, 22 V, 15.50 L/min and 278.46 o C. To clearly understand the rate of heat distribution across the as-welded plate, FEM bead penetration profiles were developed using Solid Works (2017 version) thermal transient analysis which revealed that the higher the temperature distribution the wider the Heat Affected Zones (HAZs) which are indications of phase transformations and alterations in mechanical properties of the welded metal which may lead to induced residual stresses if the welding parameters particularly the amperage is not controlled adequately. In addition, there was proximity in the trend of bead penetration from the regression plot where the FEM model had a coefficient of determination (R 2) of 0.9799 while R 2 of 0.9694 was obtained for the welding experimentation, indicating about 97.4% variance which in this context signifies that both bead penetration values can be adopted for real practical scenarios where deep weld bead penetrations are required.
VOLUME-8 ISSUE-10, AUGUST 2019, REGULAR ISSUE
Bead geometry plays very important role in predicting the quality of weld as cooling rate of the weld depends on the height and bead width, also bead geometry determines it’s residual stresses and distortion. Weld bead geometries are outcomes of several welding parameters taken into consideration. If arc travel is high and arc power is kept low it will produce very low fusion. If electrode feed rate is kept higher width is also found to be on higher side which makes bead tto flat. Also, the parameters like current, voltage, arc travel rate, polarity affects weld bead geometry. Hence, this paper is a review of different experimentations and modeling techniques regarding predictions of weld bead geometry and their relations with different weld parameters.
The International Journal of Advanced Manufacturing Technology, 2016
Ti-6Al-4V is an alloy increasingly used in aeronautics due to its high mechanical properties coupled with lightness. An effective technology used to manufacture titanium components with a reduced buy-to-fly ratio is laser beam welding. Previous studies showed that the key factor that rules the mechanical properties and the fatigue life of the joint is its morphology. The aims of this paper were to investigate the influence of the geometrical features of the joints (height of the top and root reinforcement, depth and radius of the underfill, and the valley-valley underfill distance) on their mechanical properties and also to conduct a finite element (FE) analysis on the real geometry of the welded joints. Ti-6Al-4V rolled sheets 3.2 mm thick were welded in butt joint configuration using a laser source and their performance was studied in terms of weld morphology, microstructure, Vickers microhardness and fatigue life. A full factorial plan, designed varying the welding speed and laser power, was carried out. The real geometry and then the joint morphology were studied through an innovative approach: for each specimen, both the total weld face and the total root surface were acquired using a confocal microscope. Finally, through these acquisitions, the clouds of points of the scanned surfaces were used in order to carry out a FE analysis capable of providing a stress concentration factor, K t , value for each detected joint. The main results are the realization of a reliable FE model by an experimental agreement and the relationship found amongst the fatigue performances and some noticeable metallurgical and geometrical features, such as the underfill depth and the aspect ratio defined as the ratio between the maximum height of the joint and the valley-valley underfill distance.
IRJET, 2020
Metal Inert Gas (MIG) welding is a widely used joining process across the industry. It uses a solid consumable filler wire which is heated and melted by generating an arc between wire and the workpiece. The popularity of this welding technique is because of its versatility, high quality welds, ability to get fully automated and use in mass producing units. The process can successfully weld a large number of materials for which suitable filler wire can be made available. Aluminium is a material of immense industrial potential because of its many favourable mechanical properties. It poses a little reluctance towards joining through welding. The present work involves investigating the weldability of aluminium from the view point of weld bead geometry and shape relationship. Aluminium grade 1200 has been selected for the present work because of its utility in manufacturing pipelines, shipbuilding industry, etc. the important input parameters chosen for the study were welding speed (WS), voltage and wire feed rate (WFR). An attempt is made to establish a mathematical relationship between the input and response parameters which in this case are weld width (W), height of reinforcement (HOR) and weld reinforcement form factor (WRFF), which is the ratio of W and HOR. Design of experiment (DoE) technique was used to conduct the experiments in a structured way and develop the model, response surface methodology is used to analyse the results graphically. The developed model was analysed and its significance was checked using ANOVA analysis. 1.0 INTRODUCTION MIG welding has its widespread applications in automotive industry, pipeline welding, shipbuilding industry and many more because of its ability to produce uniform, slag-free, clean and strong welds. Welding of aluminium is a little difficult process because of two main reasons; first being the formation of refractory oxide layer on its surface and second is its high thermal conductivity. The oxide layer is refractory in nature with very high melting point. This oxide layer poses difficulties during the welding of aluminium. The oxide layer acts as an insulator resulting in difficulty in establishment of arc between the work and the electrode. Secondly, the high conductivity does not allow the heat of welding to raise local temperature to rise to the melting point thereby resulting in no welding. Special steps are required to be taken for the welding of this metal. Typical steel liners can scratch and shave aluminium feed wire easily being hard inside. Teflon liners were used in place of steel liners to reduce friction and eliminate wire shaving. burnback is also very common in MIG welding of aluminium. To prevent burnback, nozzle plate distance was increased and copper-zirconium alloy contact tips were used along with increasing the shielding gas flow rate. Researchers have made various attempts to predict and interpret the effects of welding parameters on the weld bead [1-4]. The intricacy of the weld bead is directly affected by weld schedules and thus the manufacturing costs of assemblies and procedures [5]. The welded joints have been found to fracture from the weld deposit, close to fusion line. This is because of presence of porosity in this area [6]. Instead of many challenges faced during the welding of aluminium, the material still offers many lucrative advantages as a construction material, being its easy workability, machinability and excellent strength to weight ratio. In the present case, aluminium 1200 is used because of its high corrosion resistance, good weldability and high anodising capability. It also possesses high coefficient of reflection and high thermal conductivity. It is classified as a non-heat treatable commercially pure aluminium inspite of 99% minimum requirement for aluminium content. Aluminium 1200 used consists of aluminium (minimum 99%), iron+silicon(1%), magnesium(0.05%), titanium(0.05%), manganese(0.05%), copper(0.05%), zinc(0.01%), and other elements(0.015%) [7]. DoE approach was used to generate the combination of experiments to be conducted. Central Composite Face centre design approach was found suitable for the number of variables and levels opted for the present study. This design comprises fractional factorial design with centre points, amplified using cluster of axial points (star points) that enables the correct approximation of the curvature. It is capable of predicting quite accurately the first order terms, second-order terms and interaction terms [8]. A total number of 15 runs were conducted. The software was used to develop the