PREDICTION OF WELD INDUCED ANGULAR DISTORTION OF SINGLE SIDED AND DOUBLE SIDED FILLET JOINT BY SAW PROCESS

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1 5 th International & 26 th All India Manufacturing Technology, Design and Research Conference (AIMTDR 2014) December 12 th 14 th, 2014, IIT Guwahati, Assam, India PREDICTION OF WELD INDUCED ANGULAR DISTORTION OF SINGLE SIDED AND DOUBLE SIDED FILLET JOINT BY SAW Arpan Kumar Mondal 1*, Pankaj Biswas 2, Swarup Bag 3 &Manas M Mohapatra 4 1* Department of Mechanical Engineering, Indian Institute of Technology Guwahati, India , m.arpan@iitg.ernet.in 2 Department of Mechanical Engineering, Indian Institute of Technology Guwahati, India , pankaj.biswas@iitg.ernet.in 3 Department of Mechanical Engineering, Indian Institute of Technology Guwahati, India , swarupbag@iitg.ernet.in 4 Department of Mechanical & Industrial Engineering, Indian Institute of Technology Roorkee, India , manasfme@iitr.ac.in Abstract In this present work a numerical elasto-plastic thermo-mechanical model has been developed to predict the weld induced angular distortion of single sided and double sided fillet joint by SAW process. The welding was carried out by using recyclable flux-filled backing strip in single pass. The angular deformations for both the cases have been measured experimentally. It has been found that the maximum magnitude of angular deformation is lower in case of double sided fillet joint. A detail comparative study of the angular deformation between single and double sided fillet joint has been presented in this study. It has been observed that the developed elasto-plastic thermo-mechanical model is well comparable with experimental results. Keywords: submerged arc welding,elasto-plastic, thermo-mechanical model, single and double sided fillet weld joint, single pass, angular deformation. 1 Introduction While assembling several parts welding deformation is a serious concern. Referring to Deng and Murakawa (2011) angular deformation affects the structural integrity, dimensional accuracy as well as the quality & performance of the final part, thus leads to an unstable structure. Deng &Murakawa (2011)and Biswas et al. (2009) stated that arc welded stiffened panels are the part of any large structure and can be seen in shipbuilding, bridges etc. The localized nonuniform heating and cooling during welding develops residual stress followed by permanent deformation in the base metal and weld itself, thus reduces the proper functioning of the welded structure. Therefore, it is essential to estimate the magnitude of angular deformation due to welding in a welded structure to increase the weld structure efficiency and functional ability. The angular deformation can be determined experimentally or it can be predicted by using some numerical techniques. Finite Element (FE) analysis of welding is highly effective in predicting thermomechanical behaviour. It has been more than four decades ever since Ueda and Yamakawa (1971) proposed a thermal elastic plastic finite element method to analyse the thermal transient stresses induced in a butt and fillet weld under a moving electrode. Following the pioneering work of Ueda and Yamakawa (1971) and many researchers(deng&murakawa (2011), Biswas et al. (2009), RadajDieter (1992) andhong et al. (1998))have successfully developed a large number of numerical models based on the finite element method to predict temperature distribution, analysing the welding residual stress and distortion both in 2D and 3D modes. Teng et al.(2001) have investigated the residual stresses and distortion of T-joint fillet welds using two dimensional finite element analyses. Tsai et al. (2004) modelled the angular distortion of T-joints using plasticity based distortion analysis. Michalerisand 34-1

2 PREDICTION OF WELD INDUCED ANGULAR DISTORTION OF SINGLE SIDED AND DOUBLE SIDED FILLET JOINT BY SAW DeBiccari(1997) successfully predicted the distortions during fusion welding using temperature dependent material properties of the steel in the finite element modelling. Mahapatra et al. (2007) analysed the effect of tack position on angular deformation in single sided submerged arc welded fillet joints. Tsai and Cheng (1999) investigated distortion mechanism and the effects of welding sequence on thin panel distortion using finite element analysis.the works of the above researchers indicates that angular deformation in a welded joint is a matter of real concern which strongly affects the performance of the structure. However it has seen that adequate importance has not been provided to the work related to comparative study of angular deformation between the single and double sided fillet joints. The present study aims to develop a finite element based thermomechanical model considering elasto-plastic response of material for predicting residual stresses and the angular deformation. The numerical model considers temperature dependent material properties and latent heat of melting and solidification. The numerical results have been validated with experimentally measured angular deformation to address the reliability of developed model. Finally the developed model has been utilised to do a comparative study between single and double sided submerged arc welded fillet joints. 2 Finite element (FE) model A three dimensional finite element thermomechanical model has been developed to analyze the residual stresses distribution pattern in SAW with filletjoint configuration. First of all, the heat transfer analysis is carried out to find out the nodal transient temperatures over the entire welded plate.then the nodal temperatures were applied as load for structural analysis where residual stress and corresponding angular deformation has been predicted. The heat source model in welding has an important effect on the heat distribution pattern in the vicinity of the weld zone where fusion zone and the HAZ are formed. As the plate thickness number for SAW is 0.88, the heat flow can be considered as two dimensional (Sorensen (1999)). For the process of submerged arc welding, the heat distribution of heat source may be characterized as a distribution of heat flux on the weldment surface. In this study, the heat from the welding arc is applied at any given instant of time as a normally distributed heat flux which is expressed as 3Q q sup ( r ) = exp 3 2 πr 2 r r (1) whereq is heat input from arc and is equal to the multiplication of arc voltage, current and efficiency, r is the radial distance from the centre of heat source on the plate surface and is the effective arc radius that defines the region in which 95% of heat flux is deposited (Mahapatra et al. (2007), EdwardFriedman (1975) andpathak&datta (2004)). The nonlinear elasto-plastic analysis has been performed by using the result obtained from the transient heat transfer analysis. The flow chart of FE model of mechanical analysis for predicting residual stresses is depicted in Figure1. In this analysis von- Mises yield criterion and associated flow rules are consideredas stated in the literatures of Cheng W. (2005)and HenrikAlberg(2005). The boundary conditions which prevented rigid body motions are also incorporated in the modelling. Eight nodded brick element is used for the thermal analysis and similar eight nodded elements are used for structural analysis.the plasticity is assumed as rate independent and is modelled by assuming bi-linear isotropic hardening behaviour along with associated flow rule. Equilibrium Equation σ + F = 0 From thermal analysis T { } e Stress strain relationship = D { σ } [ ]{ ε } Stress strain relationship { σ } = [ D]{ ( ε } + { ε } + { ε }) Figure 1Flow chart of thermomechanical analysis The von-mises yield criteria is followed as: = + + (2) Elastic, plastic, and thermal strain relationship ε = ε + ε + ε where,,, are principal stresses and is the average one dimensional stress. Temperature dependent material properties used for the transient heat transfer and elasto-plastic analysis which can be found elsewhere (Adak& Mandal(2003), Brown& Song (1992)). However, temperature dependent convection coefficients and yield stress for steel are considered from published literaturesadak and Mandal (2003) and Udea et al. e pl Displacement Field U th e pl th 34-2

3 5 th International & 26 th All India Manufacturing Technology, Design and Research Conference (AIMTDR 2014) December 12 th 14 th, 2014, IIT Guwahati, Assam, India (1986). The solution was obtained using the ANSYS package. 3 Experimental investigations In the present investigation a constant current SAW set up, copper coated mild steel electrode of 3.1 mm diameter and granular flux have used for carrying out the experiments. Figure 2 Submerged arc welded set up from the experimental analysis is shown in the Table 1. The maximum magnitudes of angular deformation are considered both for fillet side and opposite side. For both cases the percentage of deviation of the predicted results from the experimental results lays in between 9.07% to 17.57%, thus shows the accuracy of the developed finite element model. The developed numerical model is used to simulate the residual stress and distortions both for single and double sided fillet joints. This section provides the detail analysis of obtained results and possible conclusion on the comparison between single and double sided fillet joint. The residual stress distribution pattern for fillet welding was validated with published literature of Ma et al.(1995). Figure 4 illustrates the comparison between predicted results and published data for longitudinal (Sx) and transverse (Sy) residual stress. A good agreement can be observed in figure 4 and this indicates that the FE model for present parameters set can be used in a reliable manner.after validating the present study, the same have been used to study the welding residual stresses distribution both single and double sided fillet welding. Table 1 Comparison of angular deformation between simulation experiments Angular deformation Opposite Side Angular deformation Fillet Side Exp. Pred. Error Exp. Pred. Error Figure 3Submerged arc welded fillet joints (A) Single and (B) double sided (%) (%) The mild steel plates used in this study were of dimension 8 mm thick 100 mm X 200 mm with web height of 50mm for each half of the fillet joint. For double sided fillet welding two sided were welded one after another and transient thermal history was predicted accordingly.figure 2 shows the ADORE submerged arc welding set up. Figure 3 shows the submerged arc welded specimens of single and double sided fillet joints. The experiments conducted to study the angular deformation for single sided fillet joint and double sided fillet joint. Before welding the tack welded samples were marked to measure the coordinates before and after the welding to estimate magnitude of angular distortions. The angular distortions are measured by a co-ordinate measuring machine (CMM). Single Sided Double Sided The comparison of simulation results of single and double sided fillet welding are shown in Figs. 5 to 8. Figures 5, 6 and 7 represent the longitudinal, transverse and von-misses residual stress distribution pattern respectively. 4 Results and Discussions A comparison of the predicted angular distortion from the finite element analysis with the angular distortion 34-3

4 PREDICTION OF WELD INDUCED ANGULAR DISTORTION OF SINGLE SIDED AND DOUBLE SIDED FILLET JOINT BY SAW Figure 4 Comparison of residual stresses with published literature (Ma et al. 1995) Figure 7Contour plot of angular deformation of double sided fillet weld The maximum value of longitudinal residual stress is 409 MPa (tensile) for single sided fillet weld but for double sided fillet weld it 399 MPa. In case of single sided fillet joint the residual stress is unbalanced in both sides. The maximum magnitude of transverse residual (figure 6) stress is very less than compared to longitudinal residual stress. For single sided fillet joint it is 47 MPa and for double sided fillet it is 555 MPa. Figure 5Comparison between longitudinal residual stresses Figure 8Contour plot of angular deformation of single sided fillet weld Figure 6Comparison between transverse residual stresses From figures 5 and 6, it was observed that within and closer to the welding region the residual stress is tensile in nature and away from the weld line it is compressive in nature. The figure 7 and 8 shows contour plots double and single sided fillet joints respectively. It can be seen from figure 7 that within & closer to the welding region the amount of deformation increases with the distance perpendicular to the welding line. In the figure 8 the amount of angular deformation in the single sided fillet weld is very less in the opposite side of the fillet. The maximum value of angular deformation in case of double sidedd fillet weld is mm and in case of single sidedd fillet weld it is mm. 34-4

5 5 th International & 26 th All India Manufacturing Technology, Design and Research Conference (AIMTDR 2014) December 12 th 14 th, 2014, IIT Guwahati, Assam, India But the angular deformation of single sided fillet joint was less than the double sided fillet joint. Which implies the single sided fillet joint may be preferred than double sided fillet joints, thus saves time and resources. The results obtained through analysis and those obtained from published literatures compared fairly well with a variation of about 9 % to 17 % only. References Figure 9 Comparison between the angular deformations The figure 9 illustrates the distortions of the single and double sided fillet welded MS plate. The distortions are taken perpendicular to the weld line from center of weld to both side of the weld at the middle length of the weld line. The angular deformation in weld is the product of the weld shrinkage force during cooling and residual stress after complete solidification. It is clear from the Figure 9 that the maximum magnitude of the angular distortion both in single and double sided fillet joint is almost same. However in case of single sided fillet joint the angular deformation is completely unsymmetrical in both side of the fillet. As in case of double sided fillet joint the welding is done in both side of the fillet that s why the angular deformation developed is well balanced in both the side but cumulative value of the angular deformation is more in case of double sided fillet joint. 5 Conclusions A comparative study was done between the welding induced residual stress& angular deformation in single and double sided fillet joint configuration by means of finite element modeling and simulation. The following conclusions can be derived from the present investigation: A three dimensional finite element model for predicting residual stresses for SAW have been developed utilizing the nonlinear transient thermo-mechanical analysis assumingelastoplastic behavior of mild steel. The maximum value of angular deformation in case of double sided fillet weld is mm and in case of single sided fillet weld it is mm. The angular deformation in single sided fillet joint was unbalanced in both sided of the fillet. The cumulative angular deformation was more in double sided fillet joint. The maximum value of residual stress is more in case of single sided fillet joint compare to that of double sided fillet joint. Adak, M. and Mandal, N. R. (2003), Thermo-mechanical analysis through a Pseudo- linear Equivalent Constant stiffness System, Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment, Vol. 217, pp 1-9. Alberg, H. (2005), Simulation of welding and heat treatment modelling and validation, PhD thesis, Lulea University of Technology, Sweden. Biswas, P., Mahapatra, M.M. and Mandal, N.R. (2009), Numerical and experimental study on prediction of thermal history and residual deformation of double-sided fillet welding, Proceedings of the IMechE, Part B: Journal of Engineering Manufacture, Vol. 224, pp Brown, S. and Song, H. (1992), Implication of Three-Dimensional Numerical Simulation of welding of Large Structures, Welding Journal., Vol. 71, pp. 55s-62s. Cheng, W. (2005), In-plane shrinkage strains and their effects on welding distortion in thin-wall structures, PhD thesis, The Ohio State University, USA. Deng, D., Ma, N. and Murakawa, H. (2011), Finite element analysis of welding distortion in a large thin-plate panel structure, Transactions of the Japan Welding Society, Vol. 40, pp Friedman, E. (1975), Thermo mechanical Analysis of the Welding Process Using the Finite Element Method, Transactions of ASME., Vol. 97, pp Hong, J. K., Tsai, C. L. and Dong, P. (1998), Assessment of numerical procedures for residual stress analysis of multipass weld, Welding Journal, Vol. 77, pp. 372s 382s. Michaleris, P. and DeBiccari, A. (1997), Prediction of welding distortion, Welding Journal, vol. 76, pp. 172s-180s. Ma, N. X., Ueda, Y. and Murakawa, H. (1995), FEM analysis of 3D welding residual stresses and angular distortion in T-type fillet welds, Transactions of the Japan Welding Research Institute, Vol. 24, pp Mahapatra, M. M., Datta, G. L., Pradhan, B., and Mandal, N. R. (2007), Modelling the effects of constraints and single axis welding process parameters on angular distortions in one-sided fillet welds, Proceedings of the IMechE, Part B: Journal of Engineering Manufacture, Vol. 221(B3), pp Pathak, A. K. and Datta, G. L. (2004), Three-dimensional finite element analysis to predict the different zones of microstructures in submerged arc welding, Proceedings of the IMechE, Part B: Journal of Engineering Manufacture, Vol. 218, pp Radaj D. (1992), Heat Effects of Welding: Temperature Field. Residual Stress, Distortion, Springer-Verlag. Sorensen, M. B (1999), Simulation of Welding Distortions in Ship Section, Ph.D Thesis, Department of Naval Architecture and Offshore Engineering, Technical University of Denmark, ISBN Teng, T. L., Fung, C. P., Chang, P. H., and Yang, W. C. (2001), Analysis of residual stresses and distortions in T-joint fillet welds. Intertional Journal of Pressure Vessels and Piping, Vol. 78, pp Tsai, C. L., and Jung, G. H. (2004), Plasticity-based distortion analysis for fillet welded thin- plate T-joints, Welding Journal, vol. 83, pp. 177s-187s. Tsai, C. L. and Cheng, W. T. (1999), Welding distortion of thinplate panel structures, Welding Journal, vol. 78, pp. 156s-165s. 34-5

6 PREDICTION OF WELD INDUCED ANGULAR DISTORTION OF SINGLE SIDED AND DOUBLE SIDED FILLET JOINT BY SAW Ueda, Y. and Yamakawa, T. (1971), Analysis of thermal elastic plastic stress and strain during welding by finite element method, Transactions of the Japan Welding Society, Vol. 2, pp Ueda, Y., Fukuda, K. and Kim, Y. C. (1986), New measuring method of axisymmetric three dimensional residual stresses using inherent strains as parameters, ASME Journal of Engineering Material and TechnologyTransactions, Vol. 108, pp