Search

Purpose This paper aims to numerical and experimental analysis on substrate deformation and plastic strain induced by wire arc additive manufacturing. Design/methodology/approach The component has the form of a hollow, rectangular thin wall consisting of 25 deposition layers of SS316L on an SS304 substrate plate. Thermo-mechanical finite element analysis was applied with Goldak’s double-ellipsoidal heat-source model and a non-linear isotropic hardening rule based on von Mises’ yield criterion. The layer deposition was modelled using simplified geometry to minimize overall pre-processing work and computational time. Findings A new material modelling of SS316L was obtained from the chemical composition of the evolved component characterized by scanning electron microscope/energy dispersive X-ray and further generated by an advanced material-modelling software JMatPro. In defining heat-transfer coefficients, transient thermometric analysis was first performed in the bead and on the substrate, which was followed by an adjustment of the heat-transfer coefficients to reflect the actual temperature distribution. Based on the adjusted model and boundary conditions, sensitivity analysis was conducted prior to the ultimate simulation of substrate deformation and equivalent plastic strain. Furthermore, this simulation was verified by conducting a series of automated wire + arc additive manufacturing tests using robotic gas Metal arc welding with distortion measured by coordinate-measurement machine and equivalent plastic strain measured by optical three-dimensional-metrology measurements (Gesellschaft für Optische Messtechnik). Originality/value It can be concluded that a proper numerical computation using the adjusted model and property-evolved material exhibits a similar trend with acceptable agreement compared to the experiment by yielding an error percentage up to 30% for deformation and up to 21% for equivalent plastic strain at each individual measurement point.

This paper is dealing with an investigation using nonlinear numerical computation for manufacturing to predict substrate distortion induced by a hollow-shaped Wire Arc Additive Manufacturing (WAAM) process. The WAAM component is designed in a thin-walled rectangular form consisting of twenty-five deposited layers with austenitic stainless-steel wire SS316L as feedstock and SS304 as substrate material. In this investigation, two different material models were investigated which was directly retrieved from numerical computation or virtual manufacturing software database and evolved component material composition obtained from experiment and characterized using Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray (EDX) analysis as well as generated using advanced modelling software JMATPRO for creating new properties including the flow curves. The hollow shape is modelled based on simplified rectangular mesh geometry with identical specimen dimension during experiment. A coupled thermomechanical solution is adopted including phase-change phenomena defined in latent heat, whereby temperature history due to successive layer deposition is simulated by coupling the heat transfer and mechanical analysis. Further, transient thermal distribution is calibrated from experiment obtained from thermocouple analysis at two reference measurement locations. New heat transfer coefficients are to be adjusted to reflect actual temperature change. Prior to simulation execution, a sensitivity analysis was conducted in order to find the optimal number of elements or mesh size towards temperature distribution. Based on these boundary conditions, WAAM distortion is verified using robotic welding system equipped with pulsed power source. The experimental substrate distortion is measured on various points prior to and after the process. It can be concluded based on the adjusted model and experimental verification that using nonlinear numerical computation, the prediction of substrate distortion with evolved material property of component yields closer average result within the relative error less than 11% compared to database material giving doubled inaccuracy up to 22%.

Porous metallic materials are materials that have closed cell or open cell pores within their microstructure and have unique properties such as permeability and high stiffness-to-weight ratio depending on the type of the pore. Open cell pores in porous metallic materials allow minuscule particles such as air to pass through, giving it its permeability property. Permeability in porous metallic materials can further serve as air vents in injection moulds allowing the process to have a better surface finish and also dispel heat from the system better. Additive manufacturing can manufacture these materials to save time and cost and provides more intricate designs compared to traditional manufacturing. This study aims to manufacture maraging 300 steel with tailored porosity by controlling the processing parameters in the selective laser melting (SLM) process. The effect of each parameter on relative density was determined using an L9 orthogonal array through Taguchi’s Design of Experiments. It was found that hatch spacing had the largest effect, followed by laser power, layer thickness, and scanning speed. Regression modelling found that the equation can provide a good prediction of the relative density. When the processing parameters were related to energy density function, regression equation utilising energy density has a better performance, but its use is restricted to the range of energy density reported. The materials became permeable when the relative density is less than 95%. Permeability increases linearly with a sharp increase at a relative density below 80% due to the high volume of open pores. In terms of mechanical properties, both compression modulus and yield strength decrease with decreasing relative density. The method shown here can be applied to produce, within the same part, a combination of porous and non-porous sections in the same manufacturing process.

This study focused on investigation of the effect of process parameter to the tensile strength of a spot welded S235 low carbon steel through simulation and experiment. Resistance spot welding (RSW) is commonly used in joining metal sheets due to its key capabilities, which is time and cost effective as well as high adaptability for automation. However, strength and reliability of a spot welded joint especially in an auto vehicle can be unpredictable. Premature failure of a spot welded joint can be difficult to be predicted but common factors that had been discussed in many research is related with fatigue and residual stress. Process parameter is recognized as one of critical factors affecting the reliability and quality of a spot welded joint. Different type of material and thickness may require different set of parameter to achieve an optimum result. Experimental procedure alone to demonstrate and investigate the effect could be too costly and time inefficient. Therefore, design of experiment and non-linear FEM simulation analysis were used to analyze and validate the result. This study shows the significance of process parameters such as weld current and electrode pressure to the strength of a spot welded joint and accurate setting is needed prior to the welding process to achieve an optimum result.

This study deals with the fatigue life assessment of the transverse fillet weld and transverse fillet weld on weld fatigue specimen of the offshore steel S460G2+M with a thickness of 10 mm. These specimens were joined using gas metal arc welding (GMAW) with ER80S-N1 filler metal of 1.0 mm in diameter and mixed gases of 80% Ar + 20% CO2 as the consumables. Upon the welding completion, some of the fatigue specimens are treated using high-frequency mechanical impact device called pneumatic impact treatment (HFMI/PIT). The treatment procedure uses 90Hz of frequency, 6 bars of pneumatic pressure and 2 mm pin radius with aims to enhance the lifespan of the specimen. These fatigue specimens are classified in as-welded and HFMI/PIT. The fatigue test was conducted to all fatigue specimens until failure using a 250KN Instron fatigue machine with a constant amplitude loading, a stress ratio of 0.1 and stress loading from 55% to 75% of the yield strength of the base material. The fatigue data were evaluated based on the International Institute of Welding (IIW) evaluation procedures. Further, the fatigue life comparison between the as-welded and HFMI/PIT of both fatigue specimens also with the FAT class recommendation of the IIW for transverse fillet weld is plotted in the S-N curve diagram. Based on the assessment, it is found that the HFMI/PIT fatigue specimens attained higher fatigue life than the as-welded of both fatigue specimens. The most significant of fatigue life improvement after the HFMI/PIT is the HFMI/PIT transverse fillet weld. These treated welds obtained 256 MPa of FAT class which is 79 % higher than FAT class recommended by the IIW for the transverse fillet weld. Besides, the multi-pass welds on the groove weld of the transverse fillet weld on welds are found to contribute to a lower fatigue life of this specimen due to the existing weld defects on the fractured surface of the groove weld.

This fundamental research deals with the investigation of material property model influences on distortion induced by multi-layered Wire Arc Additive Manufacturing (WAAM) with synergic-pulsed gas metal arc welding (P-GMAW) process which was modelled and simulated by means of non-linear numerical computation. The material property models of stainless steel SS316L component to be compared stem from three different sources namely existing database, initial wire and evolved component. The new property models were generated with advanced material modelling software JMATPRO based on chemical compositions analysed at initial wire and component using SEM–EDX. The flow curve for each material model was taken with the strain rates ranging from 0.001 to 1.0 s−1. In the numerical simulation, a coupled thermomechanical solution was adopted including phase-change phenomena defined in latent heat. Goldak’s double ellipsoid was applied as heat source model and simplified rectangular bead with hexagonal element type and meshing was developed to avoid extensive pre-processing effort and to reduce the computational time at post-processing level. Temperature behaviour due to the successive layer deposition was simulated considering heat transfer effect coupled to mechanical analysis. The adjustment of simulative transient to experimental thermal distribution lead to new fitted heat transfer coefficient. Prior to execution of numerical simulation, a sensitivity analysis was conducted to find the optimal number of elements or mesh size towards maximum reached temperature. It can be concluded based on the adjusted model, selected mesh size and experimental validation that numerical computation of substrate distortion with evolved material property of component and initial wire of SS316L yield closer average result within the relative error ranging between 11 and 16% compared to database material giving more than 22%.

This paper presents basic procedure on coupled design and simulation process for 3D metal printing. As case study, the selected automotive component is front upright with the proposed material of austenitic stainless steel SS316L. This component is modelled based on real application loads and constraints in order to improve driving performance. Various outcomes are created by using generative design method based on preserve and obstacle geometry, selected materials and additive manufacturing method. Preferred design outcome will undergo smoothing process using T-Spline method and be analysed to identify the weak point at the base and bionic shape. Smoothing procedure will include additional material and sharp edge removal until desired stress and safety factor are achieved. Since 3D metal printing consist of rapid high temperature gradient during printing process, the residual stress and distortion of the final component are to be identified in order to mitigate the imperfection using mechanical analysis from inherent strain direct approach method. This process simulation using numerical computation is conducted to define best build orientation. It is expected that, the coupled design and simulation procedure for 3D metal printing can contribute to lightweight and resource-efficient additive manufacturing process.

This paper presents an investigation on deformation behaviour using elastic inherent strain method (ISM). The deformation of bead-on-plate substrate is induced by GMAW process in which the selected material of filler and substrate is austenitic stainless steel SS316L. A simplified rectangular bead geometry is modelled and the process is simulated using numerical software MSC Marc/Mentat. The inherent strain value is estimated based on process parameters and physical properties of selected material, the effective area and the structural clamping positions. The residual stress and deformation result predicted using ISM are to be compared with thermo-mechanical numerical simulation which is executed under consideration of temperature dependent isotropic hardening rule and heat source model using model Goldak’s double ellipsoid. Further, computational time between these two methods are to be compared. It can be concluded that ISM is very potential to be implemented to predict residual stress and distortion with short computational time.

Continuing improvement in the field of virtual crack closure technique of metals provides the opportunity for reliable probabilistic fatigue crack growth. The paper presents an analysis of mode I fatigue crack growth in low carbon steel. Experiment was carried out with Single Edge Notched Tension (SENT) specimens to determine its fatigue crack growth parameters on the specimens under constant amplitude loading. Linear elastic fracture mechanic crack path was modelled with the finite element method according to its experimental observation using the virtual crack closure technique (VCCT) in MSC Marc/Mentat. The simulation predicts the fatigue crack growth rate in high cycle fatigue. The simulated fatigue crack growth rate (FCGR) produced using SENT model represents good similar feature with the experimental process at stress ratio R = 0 Based on the remeshing model, it is also found that the results of crack growth rate and cycle count show good agreement within acceptable discrepancy compared to the experiment from Paris law diagram.

In this study, the austenitic grain size in bead-on-plate heat-affected zone (HAZ) are predicted as grain size has been widely known as an important factor affecting the deformation mechanism of materials, its microstructures and mechanical properties. At the first stage, a numerical model of bead-on-plate process using Goldak’s double ellipsoid heat source model is used to assess the temperature distribution during and after welding of austenitic stainless steel SS316L filler wire and plate. The numerical computation is conducted based on temperature-dependant materials properties using commercial FEM software MSC Marc/Mentat with user subroutine. Further, a numerical model is developed by using ordinary differential equation (ODE) for calculating the free grain growth algorithm combined with the presence of growing precipitates. The initial grain size (D0) value was obtained from optical microscopy observation while other values such as modified kinetic constant (M0) and activation energy (Qa) are defined through experimental investigation with various temperature ranges and holding times. It can be concluded that the austenite grain growth prediction algorithm during the bead-on-plate welding thermal cycle was successfully executed. As the outcome, grain sizes were predicted and compared with experimental investigation.

This paper presents the application of inherent strain method (ISM) for predicting distortion on selective laser melting (SLM) specimens using general purposed finite element method (FEM) software. Since the prediction distortion might acquire extensive computational time, direct analytical approach is applied as an alternative to other method such as thermo-mechanical method. The procedure will start with the estimation of initial inherent strain value based on process parameters and material properties of austenitic stainless steel SS316L as well as the effective area. The selected SLM parameters are laser power, beam spot diameter and efficiency, along with material properties. It is to be expected, that the simulation outcome of simplified geometry with general purposed numerical software, MSC Marc/Mentat 2019 will exhibit acceptable estimation compared to specialized additive manufacturing software.

This research deals with the influences of material model on deformation which is induced by Wire Arc Additive Manufacturing (WAAM) process simulated by means of thermo-mechanical non-linear FEM method. The feedstock material model is based on stainless steel SS316L which stems from three different sources namely existing database, initial and deposited wire. The actual feedstock materials were analyzed using SEM–EDX and modelled using JMATPRO software. MSC Marc/Mentat is used as the numerical computation software to develop WAAM model and to carryout simulation analysis. The plasticity model of each material is taken based on the isotropic hardening rule with von-mises yield criteria. The strain rate is selected within the range of 0.01–1.0 s−1 and Goldak’s double ellipsoid is chosen as heat source model. Simplified rectangular bead shape as meshed model is developed to avoid the huge pre-processing effort as well as to reduce the computational time. The transient temperature distribution is performed as means of thermal analysis on all three simulation models prior to investigating the deformation result of the WAAM component. Based on the result of the simulation, the noticeable difference can be examined by the transient temperature distribution and substrate distortion. The substrate distortion analysis shows that the distortion pattern based on real SS316L filler wire has more distortion compared to WAAM with default library database of SS316L. By using material model based on database of SS316L, the substrate distortion and transient temperature distribution are lower compared to other models.

This research focuses on investigating major imperfection in coupled processes of ““Welding-to-Forming”” and “Forming-to-Welding” which are frequently found in parts production in automotive industries. Finite Element Method (FEM) based Virtual Manufacturing (VM) approach is used to predict final dimensional change in both welding and forming processes through the utilization of specialized FEM software Simufact.Welding and Simufact.Forming. This research is to demonstrate the accuracy in predicting final geometry in both coupled processes where the physical properties from the first process serves as the initial condition for the later process. Low carbon steel S235 with thickness of 2 mm along with filler material ER70s mild steel is selected as material for both coupled process simulations. This study incorporates thermo-mechanical FEM as the solver for computational process as well as assign Goldak’s Double Ellipsoid Heat Source model on welding simulation that serves as moving heat source, while in forming process, a sheet metal bending process with hydraulic press is incorporated. For each coupled process, the result of the first manufacturing process will be transferred with legitimate procedure proposed by Simufact software and will serve as the initial condition for the subsequent manufacturing process. The FEM-based VM simulation was successfully conducted for both coupled process and shows in simulation result, that the average final displacement due to spring-back effect on coupled processes of “Welding-to-Forming” is 1.52 mm, while on “Forming-to-Welding” simulation results, the average final distortion yields the value of 1.12 mm.

This study presents a numerical analysis of spot-welded DP600 steel sheets to evaluate the strength of the spot-welded joint and damage model under tensile-shear loading conditions. The quality of spot-welded joint is highly dependent on process parameter, material properties and setting on the equipment. Experimental testing is commonly used method to validate the spot-weld quality, but it is costly and time consuming. The present work aims to verify the capability of FEM simulation to model the spot-welding process and generate a reliable result. The spot weld is modeled according to a standardized dimension using a non-linear FEM simulation. The main parameters used to simulate the spot-welding process are current, electrode pressure, and weld cycle. The boundary conditions were set-up in the simulation according to mechanism applied in real application and experiment. As spot weld is governed by electrical-thermal, mechanical, and metallurgical, it has been observed that the material plasticity, thermal and electrical contact conductivity are critical input in spot welding simulation. The simulation result obtained from this study is useful for future works to validate the spot-welding behavior in the FE simulation compared with experiment.

This research presents an investigation of material property model effects of thick-walled Wire Arc Additive Manufacturing (WAAM) process on deformation behaviour which involves thermo-mechanical non-linear numerical computation. A 3D thermo-elastic–plastic WAAM model is developed using general purposed FEA software MSC Marc/Mentat. The material models of component stainless steel SS316L were simulated based on two different sources namely material X5Crnimo18_10_1from default library database and evolved wire. The thermo-mechanical and thermo-physical material properties of evolved wire SS316L were obtained using chemical composition analysis SEDM-EDX and generated by advanced material modelling software. Component geometry was modelled using simplified rectangular shape and mesh which consists of ten layers and three strings. The numerical simulation was implemented under consideration of temperature dependent hardening rule with von-mises yield criteria and Goldak’s double ellipsoid heat source model was utilized. Based on the adjusted thermal coefficient parameters, the transient temperature distribution between two different material property models were analysed. The outcome of this research is to characterise the substrate deformation induced by WAAM process using material models of evolved component SS316L and existing material from default library database.

A chained forming–welding process is to be investigated and analyzed using experimental verification and numerical simulation in which the material and mechanical properties are fully transferred between processes. The investigated part is in the form of a tube with dimension of 300 mm (l) × 20 mm (OD) × 1.5 mm (t) made of a low carbon steel material DC04 commonly used for automotive parts and support structure. At first, a series of experiment using industrial U-/O-bending machine and fully automated robotic gas metal arc welding (GMAW) process on longitudinal slot were sequentially conducted and analyzed towards final geometrical change, macrostructure, and residual stress. Further, numerical simulation method using specialized FEM software Simufact.Forming and Simufact.Welding is developed to predict the major properties following the actual process parameters during experimental forming and welding process. Throughout the simulation of forming and welding process, additive isotropic hardening plasticity model based on von Mises yield criterion is selected with a wide range of operating temperature and Goldak’s double-ellipsoid is defined as welding heat source model. Based on the analysis outcome, it can be concluded that coupled forming–welding process simulation can be suitably implemented to forecast major material and mechanical properties of tube manufacturing within accepted range of error under consideration of material history.

Tensile residual stress in friction stir welded (FSW) Aluminum alloy joints is well known to be detrimental to fatigue resistance properties of joints imperiled to dynamic loading. Hence, it is important to translate the prevailing tensile residual stress to a more favorable compressive residual stress to enhance the fatigue life cycle of the welded joints. In this study, the longitudinal and transverse residual stress for FSW AA 6061 joints is measured using the hole-drilling method with electronic speckle pattern interferometry (ESPI) for various conditions. This method combines the tried-and-true hole-drilling method with digital imaging and ESPI, eliminating the application of a strain gage through stress depth profile measurements by incremental drilling. The residual stress is measured for the FSW as-welded and high frequency mechanical impact/pneumatic impact treatment (HFMI/PIT)-treated conditions.

Porous metallic materials are materials that have closed cell or open cell pores within their microstructure. These materials have high stiffness-to-weight ratios and serve as good heat exchanging materials due to the high surface area. Selective Laser Melting (SLM) method of additive manufacturing (AM) can manufacture these materials to save more time and provides more intricate designs compared to traditional manufacturing. The aim of this study was to manufacture porous materials by controlling the processing parameters (laser power, scanning speed, layer thickness, and hatch spacing) that affect the energy density applied on the metal powder during the melting. Lower energy density applied in the laser melting process leads to higher porosity. The experiments were designed using an L9 orthogonal array through Taguchi’s method to minimize the number of runs carried out. SLM Tool Steel 1.2709 specimens were manufactured with three levels of each processing parameters that contribute to a lower energy density compared to the standard energy density of 69.4 J/mm3. The relative density of each specimen was measured using Archimedes’ methods and converted to Signal-to-Noise (S/N) Ratios. The S/N ratios were used to analyze the ranking of parameters to the effect of relative density through MINITAB. The ranking of parameters was confirmed by conducting Analysis of Variance (ANOVA) analysis with the S/N ratios and comparing the percentage contribution of each parameter towards the relative density of the specimens. Hatch spacing was found to have the most effect on the relative density the most followed by laser power, layer thickness and scanning speed. Regression analysis was conducted to obtain a regression equation for relative density in terms of the four SLM processing parameters. Confirmation tests will be conducted by fabricating porous specimens with the regression equation with a targeted relative density and measuring the relative density of the fabricated specimen.

This novel study presents an unconventional approach to find the best governing process parameters of high frequency mechanical impact technique based on multi-objective optimization method. In this investigation, the post-weld mechanical treatment is aimed to enhance fatigue resistance of structural friction-stirred weld subjected to fluctuating loads by obtaining nominal sub-surface hardness. The experimental study was conducted on aluminium alloy AA 6061 with thickness of 6 mm under varied parameters centred on indenter diameter, air pressure and impact frequency. The investigation began with obtaining optimum parameters for single response by using conventional Taguchi method with L9 orthogonal array. Next, advanced optimization approach by means of multi-objective Taguchi method attempts to consider the multiple responses simultaneously which are sub-surface hardness and structural life. As the final results, the optimum value was acquired by calculating the total normalized quality loss and multiple signal-to-noise ratios based on unequal desirability. The significant level of the parameters was evaluated by using analysis of variance. Furthermore, the second-order model for predicting the objectives was derived by applying response surface methodology. It can be summarized that, first, the affecting parameters to obtain superior structural life can be ordered at significant level of ca. 65, 25 and 10% for air pressure, impact frequency and indenter diameter, respectively. Secondly, using subsequent post-weld mechanical treatment, the life cycle number can be extended up to 12 times on friction-stirred weld. Finally, based on the experimental confirmation test, the proposed method can effectively estimate the structural life and surface hardness within the acceptable range of relative error.

This paper presents the fundamental investigation on crack propagation rate (CPR) and Stress Intensity Factor (SIF) for a typical fatigue and welded specimens which are Compact Tension (CT) and Single Edge Notch Tension (SENT) as well as Butt and longitudinal T-joint. The material data of austenitic stainless steel SS316L was used to observe crack propagation rate with different initial crack length and different tensile load was used for the fracture mechanics investigation. The geometry of the specimens was modelled by using open source software CASCA while Franc 2D was used for post processing based on Paris Erdogan Law with different crack increment steps. The analysis of crack propagation using fracture mechanics technique requires an accurate calculation of the stress intensity factor SIF and comparison of the critical strength of the material (KIC) was used to determine the critical crack length of the specimens. it can be concluded that open source finite element method software can be used for predicting of fatigue life on simplified geometry.

This fundamental investigation presents the study on the grain growth prediction for bead-on-plate of stainless steel SS316L. At first, the numerical model is developed by using basic equation with ordinary differential equation for calculating the grain growth with the presence of growing precipitates. The modified kinetic constant (M o *) is defined based on experimental investigation using quench and deformation dilatometer for peak temperature of 1200°C and holding time of 30 seconds. The FEM simulation is conducted based on temperature dependant materials properties using MSC Marc/Mentat. As the outcome various temperature ranges for calculating the grain growth are presented. These results are to be used for further investigation using experimental bead-on-plate.

This research focused on the development of numerical approximation procedure applied for resistance spot welding process which includes testing procedure to evaluate the tensile strength of a spot welded joint. The spot weld is modelled according to standardized dimension for tensile test with main material properties of Cu-sw as electrode and low carbon steel S235 as sheets with 1mm thickness. It is including electric conductivity, resistivity and heat transfer coefficient in solid body as well as contact interface. The FEM simulation is conducted using the process parameter of current 15,000A, force 5,000 N and different stages of time following the welding process and tensile test which is simulated after released both electrodes and material reaches the initial temperature with contact clamp velocity of 5mm/min. It is expected that the resistance spot welding process can be successfully simulated and producing result within acceptable range of errors.

In this paper, the numerical model of coupled process forming to welding by means of FEM is developed in order to analyse the displacement. Simufact. Forming and Simufact. Welding are utilized to execute a thermomechanical FEM analysis of forming to welding coupled process. Prior to welding process, a sheet metal bending process is performed in order to bend the 2mm plate into a U-shaped geometry. The material used for this process is S235 low carbon steel along with filler material ER70s. Goldak’s double ellipsoid model is chosen as the heat source model for GMAW simulation. A series of sheet metal bending and GMAW experiment is executed in order to verify the distortion result produced by FEM analysis. ABB IRB 2400/16 is the assigned robotic welding equipment used in GMAW process while sheet metal bending machine SUNFLUID 800/2007 is utilized for sheet metal bending process. For the calibration model, a forming force between FE simulation will be compared with the forming force of experimental bending process. The final results have shown that the distortion result of FEM analysis of coupled process forming to welding shows a good agreement with the experimental coupled process.

This research deals with the fatigue life investigation using experiment and FEM simulation on longitudinal fillet weld of structural offshore steel S460G2+M with a thickness of 10mm. The experimental fatigue test is conducted based on nominal stress (NS) approach while the simulation uses the effective notch stress (ENS) approach for fatigue life assessment. The investigation begins with the preparation of the longitudinal fillet weld fatigue specimen using Milling Machine based on the IIW fatigue specimen design recommendation and joined using the semi-automatic GMAW process following the AWS D1.1 procedure. Fatigue testing on non-load carrying fillet weld is conducted using the Instron Fatigue Machine with a stress ratio of 0.1 with constant amplitude loading and stress loading from 50%-75% of the yield strength of the base material. For the simulation approach, the 3D longitudinal fillet weld geometry is created using CAD based on the ENS design procedures of IIW where the sizes and dimensions are similar to the experimental fatigue specimen. The static elastic stress analysis of the model is conducted using MSC Marc/Mentat FEM software. Based on the IIW fatigue data evaluation, it is found that the natural mean curve of the longitudinal fillet weld obtained 146 MPa of FAT class which exceeds approximately 106% from the IIW FAT class recommendation for a longitudinal fillet joint. However, the characteristic curve of 97.7% failure probability of the parts only attained 95 MPa of FAT class, but still exceeds approximately 33% form the IIW FAT class. In the ENS fatigue assessment of the 3D longitudinal fillet weld, it is found that the model obtained 195MPa of FAT class which is inferior approximately 15 % from the FAT class recommendation of IIW. Also, it is found that both S-N curves of NS after conversion to ENS system have a good agreement with the S-N curve of ENS of 3D longitudinal fillet weld model and the IIW recommendation due to only 16 % and 34% lower as compared with the IIW FAT class recommendation for ENS.

One of the main challenges in correlating welding parameters and weld quality is its complexity to include as many as possible factors. In this research, the effects of spot welding parameters on weld quality were investigated. The effects of weld time, weld current, and electrode force on the sizes of fusion zone and heat affected zone, and tensile-shear load were studied. These welding parameters and weld quality were analysed using the three response Taguchi L9 orthogonal array method in Minitab 17. Second-order regression models of fusion zone size, heat affected zone size and tensile-shear load were constructed by adapting Response Surface Method. The optimum weld time was 0.2 s, weld current of 10 kA and the required electrode force was 2.3 kN. These parameters were within 5% discrepancies with the experiment results. Weld current was the most important welding parameter that determines the weld quality, with the contribution of 69%. From our observation, the failure mode was the pullout type, a generally accepted failure for welded joint. The outcomes of this research contributed to the advancement in optimization technique for RSW joint, by increased the number of weld quality from two to three response.

Springback is the phenomenon in which the material strip unbends itself after forming process. It is caused by the geometrical, mechanical properties or other process parameters. This paper focused on finite element simulation investigation on effects of geometrical parameters on the springback amount of the High Strength Steel (HSS). Two geometrical parameters, punch radius (Rp) and die opening (Wo) were selected and their effect on springback studied. Finite element simulation of U-bending test was performed using Simufact.formingTM with material database (MatILDa) and the level of the springback was measured. The result of the simulation shows that different values of punch radius (Rp) and die opening (Wo) are significant to the springback effect. 3 variable values of (Rp) and (Wo) selected in this studied are (2mm, 4mm, 6mm) and (30mm, 36mm, 48mm) respectively. The findings of the simulation could be used to accurately and reliably predict springback behavior of the tested material. The value of the springback increases, as the value of the die opening (Wo) increases. Meanwhile, the increasing value of the punch radius (Rp) will lead to decreasing springback value. From this finding, a proper prevention method can be taken to eliminate springback, achieve improvement in the forming process as well as reduce processing time and cost.

This study presents the effect of the governing parameters in friction stir welding (FSW) on the mechanical properties and weld quality of a 6mm thick 6061 T651 Aluminum alloy butt joint. The main FSW parameters, the rotational and traverse speed were optimized based on multiple mechanical properties and quality features, which focus on the tensile strength, hardness and the weld quality class using the multi-objective Taguchi method (MTM). Multi signal to noise ratio (MSNR) was employed to determine the optimum welding parameters for MTM while further analysis concerning the significant level determination was accomplished via the well-established analysis of variance (ANOVA). Furthermore, the first order model for predicting the mechanical properties and weld quality class is derived by applying response surface methodology (RSM). Based on the experimental confirmation test, the proposed method can effectively estimate the mechanical properties and weld quality class which can be used to enhance the welding performance in FSW or other applications.

Additive-manufacturing technologies have been gaining tremendously in popularity for some years in the production of single-part series with complex, close-to-final-contour geometries and the processing of special or hybrid materials. In principle, the processes can be subdivided into wire-based and powder-based processes in accordance with the Association of German Engineers (VDI) Guideline 3405. A further subdivision is made with respect to the smelting technology. In all of the processes, the base material is applied in layers at the points where it is needed in accordance with the final contour.The process that was investigated was wire-based, multi-pass welding by means of gas–metal arc welding. This was accomplished in the present study by determining the material parameters (thermo-mechanical and thermo-physical characteristics) of the welding filler G3Si1 (material number: 1.5125) that were necessary for the numerical simulation and implementing them in a commercial FE program (MSC Marc Mentat). The focus of this paper was on simulation and validation with respect to geometry and microstructural development in the welding passes. The resulting minimal deviation between reality and simulation was a result of the measurement inertia of the thermocouples. In general, however, the FE model can be used to make a very good predetermination of the cooling behaviour, which affects the microstructural development and thus the mechanical properties of the joining zone, as well as the geometric design of the component (distortion, etc.).

This paper deals with the investigation on the potential of welding deformation’s prediction tool using linear thermal elastic numerical method. The weld-induced distortion was analyzed on combined butt and T-joints with thickness of 9 mm which is commonly applied in ship panel structure. In this research, the distortion behavior was predicted by means of a relatively new finite element (FEM) code developed by INPRO and ESI Group which utilizes shell elements in the numerical method to allow fast computational time. In order to verify the simulation results, a series of experiments using a fully automated welding process were carried out to measure the weld-induced distortions. By comparing the results between both methods, it can be summarized that the linear elastic FEM using this software is capable of predicting the distortion within minutes while providing a reasonable agreement with the experiments.

This paper presents the effects of spot welding parameters on multi-response weld quality and optimizes the governing parameters of Resistance Spot Welding (RSW) towards the tensile shear strength and nugget size using Taguchi method. The main affecting welding parameters such as electrode force, weld time and weld current were determined as the basis for quality evaluation. The selected quality features were classified into shear strength and nugget size which were required for application with highly dynamic loading. The optimum welding parameter was obtained using multi signal-to-noise ratio (MSNR) and the significant level of welding parameters was further analysed using analysis of variance (ANOVA). Based on the results, electrode force was found to be most effective parameter affecting shear strength and nugget size. The experiment was conducted at optimum welding parameter and validated the used of multi-objective Taguchi method for enhancing performance and optimizing the welding parameters in RSW process.

The robot can perform Flux Cored Arc Welding (FCAW) at high productivity and consistency in quality. The quality of the welding depend on the selection of welding parameter and deposition geometry. These input has to be known before the start of production, generally the welding operator will obtain the information through experimental trial and error. This project planned to develop a tool that can advise the choice of welding parameter that produce quality weld bead with desired geometry. This research focused on the correlation of heat input on weld bead geometry and the range of welding parameter for fillet design welded in downhill direction (3F). From the correlation trend-line equations and welding parameter population boundary, the weld bead geometry and welding parameter for quality deposit are predicted. Consequently two calculators were developed to display the values digitally. The deviation of predicted bead geometry from actual welding is less than 1mm. Mean Absolute Deviation (MAD) is less than 0.4mm, accuracy is good. A wide range of welding parameters can be generated for quality welding at desired bead geometry.

A robotic system can convert the semi-automatic Flux Cored Arc Welding (FCAW) to an automatic welding system. The critical requirement in automated welding process is that the optimal welding parameter has to be set before welding start. These input welding parameters cannot be easily guessed unless one has the knowledge. Only very specific range of heat input that produces quality weld deposition. The correlation between the heat input and fillet weld bead can be displayed in a unique trend-line graph. Mathematical formulas that match the trend-line profile can be used to create a prediction calculator that displays the digital values of weld bead geometry when welded at a specific range of heat input. Small Mean Absolute Deviation between predicted and measured geometry means good prediction accuracy. With this correlation chart, the welding parameter for quality weld bead can be selected and the geometry of FCAW weld deposition in 2F position can be predicted accurately without trial and error.

This paper presents an unconventional method to optimize the governing process parameters of Friction Stir Welding (FSW) towards the mechanical properties and weld quality. The optimization approach attempts to consider simultaneously the multiple quality characteristics namely tensile strength, nugget zone hardness and weld quality class using Multi-objective Taguchi Method (MTM). The experimental study was conducted for plate thickness of 6.0 mm under different rotational and traverse speed. The optimum welding parameters were investigated using Taguchi method with L9 orthogonal array. The significant level of the welding parameters is to be investigated by using analysis of variance (ANOVA). Furthermore, the optimum value was analyzed by means of MTM which involved the calculation of total normalized quality loss (TNQL) and multi signal to noise ratio (MSNR).

This paper presents an investigation of the welding sequence effect on induced angular distortion using FEM and experiments. The specimen of a combined joint geometry was modeled and simulated using Multipass Welding Advisor (MWA) in SYSWELD 2010 based on the thermal-elastic-plastic approach with low manganese carbon steel S3355J2G3 as specimen material and Goldak's double ellipsoid as heat source model. To validate the simulation results, a series of experiments was conducted with two different welding sequences using automated welding process, low carbon steel as parent metal, digital GMAW power source with premixed shielding gas and both-sided clamping technique. Based on the results, it was established that the thermo-elastic-plastic 3D FEM analysis shows good agreement with experimental results and the welding sequence “from outside to inside” induced less angular distortion compared to “from inside to outside”.

This paper presents an investigation on hot forging process using simulation and experimental study. The product to be investigated was water meter housing made of material CuZn40Pb2. In the simulation part, Finite Volume Method (FVM) was applied by using commercial FEM/FVM software SIMUFACT version 10.0 and material database MATILDA. The simulation parameters followed the actual setting under consideration of the machine characteristic and friction. The simulation was further verified using crank-pressed forging machine with graphite lubrication. As the final result, the comparison defect of folds and laps between simulation and experiment is presented. It can be concluded that this simulation software offered fast solution analysis time in prediction of forging defects within good agreement between simulation and experiment.

In this research, the capability of the multipass welding advisor (MWA) is to be evaluated in analyzing the angular distortion that is induced by gas metal arc welding (GMAW) process used to join a combination of butt and T-joint with thickness of 9 mm. The MWA in SysWeld 2010 is applied to develop and compare 2D/3D finite element analysis (FEA) based on the thermal elastic–plastic approach with low manganese carbon steel S355J2G3 as parent and weld material. For this simulation, the heat source of GMAW follows the Goldak's double ellipsoid model that is available within the FEA code. Detailed procedures of MPA are presented throughout this study followed with a comparison between 2D and 3D results of distortion and computational time on the combined types. To validate the simulation results, a series of experiments was conducted on low carbon steel using robotic welding process, GMAW power source with shielding gas composition of Ar (80 %)/CO2 (20 %), and both-sided clamping method. It was established that the results of 3D simulation and experiments showed acceptable accuracy, while 2D results offers a fast solution analysis time in estimating distortion trend.

Digital radiography incresingly is being applied in the fabrication industry. Compared to film- based radiography, digitally radiographed images can be acquired with less time and fewer exposures. However, noises can simply occur on the digital image resulting in a low-quality result. Due to this and the system’s complexity, parameters’ sensitivity, and environmental effects, the results can be difficult to interpret, even for a radiographer. Therefore, the need of an application tool to improve and evaluate the image is becoming urgent. In this research, a user-friendly tool for image processing and image quality measurement was developed. The resulting tool contains important components needed by radiograph inspectors in analyzing defects and recording the results. This tool was written by using image processing and the graphical user interface development environment and compiler (GUIDE) toolbox available in Matrix Laboratory (MATLAB) R2008a. In image processing methods, contrast adjustment, and noise removal, edge detection was applied. In image quality measurement methods, mean square error (MSE), peak signal-to-noise ratio (PSNR), modulation transfer function (MTF), normalized signal-to-noise ratio (SNRnorm), sensitivity and unsharpness were used to measure the image quality. The graphical user interface (GUI) wass then compiled to build a Windows, stand-alone application that enables this tool to be executed independently without the installation of MATLAB.

In this paper, a local/global approach has been used to predict weld induced distortion in butt joint. This approach combines non-linear thermo-elastic plastic and linear elastic analyses to compute final distortion triggered by the welding process. Distortion can lead to dimensional inaccuracy and thus causing the rise in fabrication cost. In this study, Finite Element Method (FEM) software Sysweld and Pam-Assembly were used for computing the welding deformation. The material used for the simulation was low carbon steel with thickness of 4 mm. Based on the result obtained, it was observed that this approach provides fast computation time and efficient solution.

This paper presents an alternative method to optimize parameters on single V butt welding. The effect of single-passed welding parameters such as current, voltage, welding speed and width of weaving movement on major welding defects by using a one-sided clamping method was investigated. The optimum parameter values were analyzed using Multi Objective Taguchi Methods (MTM) which started with the application of the common Taguchi methods (L8) Orthogonal Array (OA) and Total Normalized Quality Loss (TNQL) followed by ANOVA under simultaneous consideration of response weighting factors. Further, the value was analyzed by employing Multi Signal to Noise Ratio (MSNR). For the experimental study, a robotic welding system ABB IRB 2400/16 with digital welding power source KEMPPI Pro Evolution ProMIG 540 MXE with shielding gas Argon 80% and Carbon Dioxide 20% were applied. The material used is low carbon steel with 4 mm plate thickness. Based on the verification test result, it is found out that MTM can be used as an alternative method to investigate the optimum value of single passed welding parameter with multiple quality features.

Resistance Seam Welding (RSEW) is an ideal welding method to produce airtight joints where welding input parameters play a very significant role in determining the quality of weld nugget and heat affected zone (HAZ) formation. This research is aimed to study the nugget and HAZ development of 1 mm low carbon steel using RSEW. Welding parameters such as weld current, weld time, weld speed and pressure were identified and investigated to study their effect on the formation of weld nugget by using 24 factorial designs. The objective of this work is to find the optimum parameter to optimize the width of weld nugget and HAZ in order to obtain a good quality of RSEW. Furthermore the mathematical models were developed to predict the weld zone development. Experimental confirmation test was conducted at an optimal condition for observing accuracy of the developed model. Based on the confirmation test, the proposed method can be effectively used to predict the size of weld zone which can improve the welding quality and performance in RSEW.

In this project, the residual stress due to multipassed welding process at the fillet weld will be studied using 2D Finite Element Analysis (FEA) simulation method and experimental investigation. Due to the extensive capabilities and dedicated tools for the simulation of welding, including material deposit via element activation or deactivation and predefined or customized moving heat sources, SYSWELD 2010 was chosen as the FEA software. The material with a thickness of 9 mm was structural steel S355J2G3 for simulation and low carbon steel for the experiment. The clamping condition was selected to obtain the best relationship between simulation and experiment by using Strain Gage. The model was dedicated to multipassed welding using the robotic welding system

The cost of development of WPS will be very expensive if the welding parameter is selected based on trial and error. Optimal welding condition cannot be easily guessed unless the operator has records of good welding. If a calculator that can predict the welding parameter for the desired bead geometry accurately, such tool will be extremely useful for any fabrication industry. This paper intends to investigate the correlation between the welding parameter and weld bead geometry of 2F position T-fillet carbon steel, when welded by 1.2 mm diameter wire submerged arc welding. Keeping only one parameter as variable, 2F fillet weld coupons are welded by SAW with a range of welding current, welding voltage and welding speed. Only weld bead geometry that complied with the quality requirement of code of practice AWS D1.1 is considered. The trendline graph is created to fit the correlation between the heat input and the fillet weld geometry. By incorporating the trendline formulas into the calculator, the weld bead geometry can be predicted accurately for any welding parameter. The mean absolute deviation (MAD) between the predicted geometry and the experimental results is less than 0.50mm.

This paper presents an alternative method to optimize process parameters of resistance spot welding (RSW) towards weld zone development. The optimization approach attempts to consider simultaneously the multiple quality characteristics, namely weld nugget and heat affected zone (HAZ), using multi-objective Taguchi method (MTM). The experimental study was conducted for plate thickness of 1.5 mm under different welding current, weld time and hold time. The optimum welding parameters were investigated using the Taguchi method with L9 orthogonal array. The optimum value was analyzed by means of MTM, which involved the calculation of total normalized quality loss (TNQL) and multi signal to noise ratio (MSNR). A significant level of the welding parameters was further obtained by using analysis of variance (ANOVA). Furthermore, the first order model for predicting the weld zone development is derived by using response surface methodology (RSM). Based on the experimental confirmation test, the proposed method can be effectively applied to estimate the size of weld zone, which can be used to enhance and optimized the welding performance in RSW or other application.

In this research, the effect of parameters in Resistance Spot Welding (RSW) on the weld zone development was first investigated using Taguchi Method. Further, the RSW parameters were to be optimized based on multiple quality features, focusing on weld nugget and Heat Affected Zone using multi-objective Taguchi Method (MTM). The optimum welding parameter for MTM was obtained using Multi Signal to Noise Ratio and the significant level was further analyzed using Analysis of Variance. Lastly, Response Surface Methodology was employed to develop the mathematical model for predicting the weld zone development. The experimental study was conducted under varied welding current, weld time and hold time. To validate the predicted model, experimental confirmation test was conducted for plate thickness of 1 and 1.5 mm. Based on the results, the developed model can be effectively used to predict the size of weld zone which can improve the welding quality and performance in RSW.

This paper investigates the capability of linear thermal elastic numerical analysis to predict the welding distortion that occurs due to GMAW process. Distortion is considered as the major stumbling block that can adversely affect the dimensional accuracy and thus lead to expensive corrective work. Hence, forecast of distortion is crucially needed and ought to be determined in advance in order to minimize the negative effects, improve the quality of welded parts and finally to reduce the production costs. In this study, the welding deformation was simulated by using relatively new FEM software WELD PLANNER developed by ESI Group. This novel Welding Simulation Solution was employed to predict welding distortion induced in butt and T-joints with thickness of 4 mm. Low carbon steel material was used for the simulation and experimental study. A series of experiments using fully automated welding process were conducted for verification purpose to measure the distortion. By comparing between the simulation and experimental results, it was found out that this program code offered fast solution analysis time in estimating weld induced distortion within acceptable accuracy.

This paper investigates the simulation technique for analyzing the distortion behavior induced by welding process on welded plate which was clamped on one side. This clamping method is intended to enable the investigation of the maximum distortion on the other side. FEA software SYSWELD was employed to predict multipassed butt weld distortion of low carbon steel with thicknesses of 6 mm and 9 mm. The simulation begins with the development of model geometry and meshing type followed by suitable selection of heat source model represented by the Goldak’s double ellipsoid model. Other parameters such as travel speed, heat input, clamping method etc. were determined. The model is dedicated for multipass welding techniques using Gas Metal Arc Welding (GMAW). The experimental works were conducted by using Robotic welding process.

In this paper, the capability of linear thermo-elastic numerical analysis method to estimate the welding deformations was investigated. The weld induced deformation is considered as the major stumbling block that can affect the dimensional accuracy. Based on this fact, welding distortion is necessarily to be predicted, if experimental investigation becomes expensive, to minimize the negative effects, improve the quality of welded parts and finally to reduce production cost. In this study, the welding distortions on butt and T-joints with thicknesses of 4 mm and 6 mm were simulated using relatively new FEM software WELD PLANNER developed by ESI Group. The material used for the simulation was low Carbon steel. By comparing the results between simulation and experiment, it was found out that this software provided immediate solution for computational analysis time and was capable to predict the distortion within acceptable accuracy.

Research highlights? Fuzzy expert system to predict the effect in CO2 laser cutting process was developed using MATLAB FL Toolbox. The relationship between laser cutting parameters (power, speed and gas pressure) and FL predicted cutting output characteristic (surface roughness and dross inclusion) was established. Appropriate selection parameters in fuzzy inference process leads to a good correlation between the experimental and prediction result. Development of the FL model provide a good foundation and encouragement for laser industrialist to expand the use of lasers in materials processing. In laser cutting, the surface quality and metallurgical characteristics of the end product is what matters the most in terms of laser cutting quality. Thus, an attempt has been carried out to develop an expert system using fuzzy logic model to predict the effect of carbon dioxide (CO2) laser cutting quality based on laser cutting parameters onto 1mm thickness of Incoloy? alloy 800. The predicting fuzzy logic model is implemented on Fuzzy Logic Toolbox of MATLAB using Mamdani technique. A set of training and testing consists of 125 data used in the fuzzy logic model are arranged in a format of three input parameters that cover the power, assist gas pressure and cutting speed, and two output parameters which are the surface roughness and dross inclusion. The relationships between experimental results, fuzzy logic model and statistical results for both training and testing performance exhibited a good correlation. Based on the results of the study, it shows that the proposed fuzzy logic model can be used to predict the surface roughness and dross inclusion of carbon dioxide (CO2) laser cutting process for Incoloy? alloy 800.