Thin plates, which are widely used in ship structures, undergo weld-induced buckling distortions ... more Thin plates, which are widely used in ship structures, undergo weld-induced buckling distortions because of their lower critical buckling strength. Thus, there is a need for an active in-process distortion control mechanism in the welding involving thin plates. In this regard, a ThermoMechanical Tensioning (TMT) method was developed and implemented successfully. In the current work, experimental investigation of the effect of TMT pull on the resulting welding distortions is studied and also the TMT process is compared with a heat sinking technique. The experimental results indicate that an increase in the TMT pull would reduce the extent of weld-induced buckling distortions. The results also suggest that a complicated heat sinking technique can be effectively replaced by a TMT process in reducing the welding out-of-plane distortions. The concept of TMT is further extended to the fabrication of grillage structures used in ship structures, which includes longitudinal and transverse we...
Severe distortions are observed in fabrication of large stiffened ship panels using lower thickne... more Severe distortions are observed in fabrication of large stiffened ship panels using lower thickness plates ranging from 3 mm to 10 mm. It requires expensive postwelding fairing operations. It is naturally preferable to control the distortion during fabrication than to apply fairing operations. Welding sequence plays an important role in controlling distortion. The aspect of weld sequencing has been studied only on a small and extremely simple form of test models. Possible welding sequences were worked out, based on principles of heat balancing or heat accumulation and subsequent behavior of such panels. Based on this, large stiffened panels were fabricated using low carbon steel of shipbuilding quality considering four different welding sequences. Initial and final distortions of these panels were measured using high precision coordinate measuring machine. In this investigation, experiments and measurements played a very important role, as numerical simulation of such large panels w...
The present work deals with the prediction of heat source parameters of Goldak's double ellip... more The present work deals with the prediction of heat source parameters of Goldak's double ellipsoidal model for flux cored arc welded fillet joints through an artificial neural network (ANN). Extensive experiments were carried out on low-carbon mild steel plates of thickness ranging from 3 mm to 10 mm. In each case, welding current (I), voltage (V), and speed (υ) were recorded as the welding parameters. The flux cored arc welding of fillet joint was carried out using 100% CO2 as the shielding gas. This work is based on the simple and fundamental presumption that the weld pool is the primary source of heat which is delivered from the welding arc. Therefore, the magnitude and distribution of heat can be defined through the weld pool dimensions. Hence, these dimensions were directly considered for determining the heat source ellipsoid parameters. These parameters, namely, front double ellipsoidal length (Cf), rear double ellipsoidal length (Cr), half-width of the heat source (a), and...
In shipbuilding industry, thin plates are widely used to maintain the minimum hull weight and to ... more In shipbuilding industry, thin plates are widely used to maintain the minimum hull weight and to increase the fuel efficiency. These thin plates, when welded, are more prone to buckling distortions. So, it is very much important to predict these buckling distortions beforehand and try to mitigate them in the fabrication stage rather than doing it later. By doing this, the competitiveness in cost and time can be increased. In this study, a numerical investigation on the reduction of buckling distortions in the fabrication of orthogonal stiffened panels as used in shipbuilding was conducted. A method of in-process distortion mitigation technique, named as thermo-mechanical tensioning (TMT) was introduced to reduce the compressive residual stress in the far-field zone. The detail stress development mechanism in TMT process is discussed here. Commercially available finite element software ANSYS® 15 was used for calculations. The simulations revealed that the peak tensile stresses in the weld zone and the corresponding far-field compressive residual stresses get significantly reduced by the implementation of TMT. Thus, with reduction of compressive residual stress, buckling of such stiffened panels is effectively mitigated.
Analysis of fillet-welded T-sections was carried out using the commercial finite element software... more Analysis of fillet-welded T-sections was carried out using the commercial finite element software ANSYS® for SM400A shipbuilding steel. To avoid the time consuming experimental technique, this model was validated with the existing experimental and numerical results. The vertical deflection, transverse shrinkage, and longitudinal residual stress were considered to validate the present model. After validating the model, the longitudinal, transverse, and normal plastic strains were collected from flange, web, and weld bead portions throughout the thickness and were averaged. These plastic strains were converted into corresponding longitudinal, transverse, and normal welding forces and were applied in an elastic model to obtain the distortions. The average welding force method was found to be very efficient in determining the distortions of welded structures. It was found that the proper distortion pattern for single-sided fillet welding can be obtained by incorporating the additional shrinkage forces from the weld bead.
Interruptions in the welding process in shipbuilding are unavoidable because of complex geometry ... more Interruptions in the welding process in shipbuilding are unavoidable because of complex geometry and human fatigue. This article presents an uncoupled threedimensional finite element (FE) modeling technique for bead-on-plate welding and an interruption in the welding process for low carbon and high notch toughness steel plate typically used in shipbuilding. The goal of the FE model was to successfully predict the effect of various time delays in the welding interruption on the residual stress distributions. The FE results are compared with the experimental results for the validation of the model. The experimental work was completed using the neutron diffraction method. The element birth-and-death algorithm was used in ANSYSW to simulate the filler metal deposition. A double ellipsoid heat source was used to simulate the heat source of the weld pool. The FE model considers the temperaturedependent nonlinear material properties and uses the temperature-dependent combined coefficient of heat loss. The study found that weld interruptions in the welding process change the residual stress patterns and cause an increase in the maximum longitudinal tensile residual stresses. However, the maximum longitudinal compressive stress reduces as a result of interruptions in the weld process. This study found that a weld interruption duration of approximately 2 minutes is optimum for both fatigue and buckling strength. This study also analyzed the effect of preheat on longitudinal residual stress distribution and concluded that a suitable short time lag without any preheat is equivalent to preheat after a long welding interval.
A lack of generalized solutions to the heat source model with submerged arc welding of low-carbon... more A lack of generalized solutions to the heat source model with submerged arc welding of low-carbon, mild steel plates led to this investigation. A double-ellipsoidal heat source model was considered. Through extensive experimentation and measuring relevant parameters of the weld pools, regression equations were established. The increased heat flow caused by turbulence of the molten metal due to various driving forces such as buoyancy, plus Lorentz and Marangoni, was captured in the simulation by increasing the thermal conductivity of the liquid metal. It was found that a higher value of thermal conductivity provides a better correlation with the experimentally measured shapes of the weld pool. The regression equations developed in this work and used for determining the double-ellipsoidal heat source parameters, along with the increased thermal conductivity of the molten weld metal, are found to provide a realistic picture of heat flow for submerged arc welding of plates with thicknesses ranging from 6 to 16 mm.
International Journal of Manufacturing Research, 2013
Effect of friction stir welding (FSW) tool geometries on aluminium welds were investigated using ... more Effect of friction stir welding (FSW) tool geometries on aluminium welds were investigated using different tool shoulder and pin probe geometry profiles. A combination of 27 tool shoulder and pin profile geometries were used for the experimental purpose using a design matrix. The effect of these tool geometries on the friction stir welds like the weld strength, weld cross-section area and grain sizes were investigated. The effects of the tool geometries were predicted using artificial intelligence techniques such as artificial neural networks (ANN) and fuzzy logic modelling. It was observed that, for a combination of FSW tool geometries, the ANN model was not so effective in predicting the FSW weldment characteristics, while the fuzzy logic model was able to predict the same with much lower percentage of error for the test cases.
Retour page d'accueil Chercher, sur, Tous les supports. Retour page d'accueil, ... more Retour page d'accueil Chercher, sur, Tous les supports. Retour page d'accueil, Plus de 1.622.000 de titres à notre catalogue ! Notice. ...
Thin plates, which are widely used in ship structures, undergo weld-induced buckling distortions ... more Thin plates, which are widely used in ship structures, undergo weld-induced buckling distortions because of their lower critical buckling strength. Thus, there is a need for an active in-process distortion control mechanism in the welding involving thin plates. In this regard, a ThermoMechanical Tensioning (TMT) method was developed and implemented successfully. In the current work, experimental investigation of the effect of TMT pull on the resulting welding distortions is studied and also the TMT process is compared with a heat sinking technique. The experimental results indicate that an increase in the TMT pull would reduce the extent of weld-induced buckling distortions. The results also suggest that a complicated heat sinking technique can be effectively replaced by a TMT process in reducing the welding out-of-plane distortions. The concept of TMT is further extended to the fabrication of grillage structures used in ship structures, which includes longitudinal and transverse we...
Severe distortions are observed in fabrication of large stiffened ship panels using lower thickne... more Severe distortions are observed in fabrication of large stiffened ship panels using lower thickness plates ranging from 3 mm to 10 mm. It requires expensive postwelding fairing operations. It is naturally preferable to control the distortion during fabrication than to apply fairing operations. Welding sequence plays an important role in controlling distortion. The aspect of weld sequencing has been studied only on a small and extremely simple form of test models. Possible welding sequences were worked out, based on principles of heat balancing or heat accumulation and subsequent behavior of such panels. Based on this, large stiffened panels were fabricated using low carbon steel of shipbuilding quality considering four different welding sequences. Initial and final distortions of these panels were measured using high precision coordinate measuring machine. In this investigation, experiments and measurements played a very important role, as numerical simulation of such large panels w...
The present work deals with the prediction of heat source parameters of Goldak's double ellip... more The present work deals with the prediction of heat source parameters of Goldak's double ellipsoidal model for flux cored arc welded fillet joints through an artificial neural network (ANN). Extensive experiments were carried out on low-carbon mild steel plates of thickness ranging from 3 mm to 10 mm. In each case, welding current (I), voltage (V), and speed (υ) were recorded as the welding parameters. The flux cored arc welding of fillet joint was carried out using 100% CO2 as the shielding gas. This work is based on the simple and fundamental presumption that the weld pool is the primary source of heat which is delivered from the welding arc. Therefore, the magnitude and distribution of heat can be defined through the weld pool dimensions. Hence, these dimensions were directly considered for determining the heat source ellipsoid parameters. These parameters, namely, front double ellipsoidal length (Cf), rear double ellipsoidal length (Cr), half-width of the heat source (a), and...
In shipbuilding industry, thin plates are widely used to maintain the minimum hull weight and to ... more In shipbuilding industry, thin plates are widely used to maintain the minimum hull weight and to increase the fuel efficiency. These thin plates, when welded, are more prone to buckling distortions. So, it is very much important to predict these buckling distortions beforehand and try to mitigate them in the fabrication stage rather than doing it later. By doing this, the competitiveness in cost and time can be increased. In this study, a numerical investigation on the reduction of buckling distortions in the fabrication of orthogonal stiffened panels as used in shipbuilding was conducted. A method of in-process distortion mitigation technique, named as thermo-mechanical tensioning (TMT) was introduced to reduce the compressive residual stress in the far-field zone. The detail stress development mechanism in TMT process is discussed here. Commercially available finite element software ANSYS® 15 was used for calculations. The simulations revealed that the peak tensile stresses in the weld zone and the corresponding far-field compressive residual stresses get significantly reduced by the implementation of TMT. Thus, with reduction of compressive residual stress, buckling of such stiffened panels is effectively mitigated.
Analysis of fillet-welded T-sections was carried out using the commercial finite element software... more Analysis of fillet-welded T-sections was carried out using the commercial finite element software ANSYS® for SM400A shipbuilding steel. To avoid the time consuming experimental technique, this model was validated with the existing experimental and numerical results. The vertical deflection, transverse shrinkage, and longitudinal residual stress were considered to validate the present model. After validating the model, the longitudinal, transverse, and normal plastic strains were collected from flange, web, and weld bead portions throughout the thickness and were averaged. These plastic strains were converted into corresponding longitudinal, transverse, and normal welding forces and were applied in an elastic model to obtain the distortions. The average welding force method was found to be very efficient in determining the distortions of welded structures. It was found that the proper distortion pattern for single-sided fillet welding can be obtained by incorporating the additional shrinkage forces from the weld bead.
Interruptions in the welding process in shipbuilding are unavoidable because of complex geometry ... more Interruptions in the welding process in shipbuilding are unavoidable because of complex geometry and human fatigue. This article presents an uncoupled threedimensional finite element (FE) modeling technique for bead-on-plate welding and an interruption in the welding process for low carbon and high notch toughness steel plate typically used in shipbuilding. The goal of the FE model was to successfully predict the effect of various time delays in the welding interruption on the residual stress distributions. The FE results are compared with the experimental results for the validation of the model. The experimental work was completed using the neutron diffraction method. The element birth-and-death algorithm was used in ANSYSW to simulate the filler metal deposition. A double ellipsoid heat source was used to simulate the heat source of the weld pool. The FE model considers the temperaturedependent nonlinear material properties and uses the temperature-dependent combined coefficient of heat loss. The study found that weld interruptions in the welding process change the residual stress patterns and cause an increase in the maximum longitudinal tensile residual stresses. However, the maximum longitudinal compressive stress reduces as a result of interruptions in the weld process. This study found that a weld interruption duration of approximately 2 minutes is optimum for both fatigue and buckling strength. This study also analyzed the effect of preheat on longitudinal residual stress distribution and concluded that a suitable short time lag without any preheat is equivalent to preheat after a long welding interval.
A lack of generalized solutions to the heat source model with submerged arc welding of low-carbon... more A lack of generalized solutions to the heat source model with submerged arc welding of low-carbon, mild steel plates led to this investigation. A double-ellipsoidal heat source model was considered. Through extensive experimentation and measuring relevant parameters of the weld pools, regression equations were established. The increased heat flow caused by turbulence of the molten metal due to various driving forces such as buoyancy, plus Lorentz and Marangoni, was captured in the simulation by increasing the thermal conductivity of the liquid metal. It was found that a higher value of thermal conductivity provides a better correlation with the experimentally measured shapes of the weld pool. The regression equations developed in this work and used for determining the double-ellipsoidal heat source parameters, along with the increased thermal conductivity of the molten weld metal, are found to provide a realistic picture of heat flow for submerged arc welding of plates with thicknesses ranging from 6 to 16 mm.
International Journal of Manufacturing Research, 2013
Effect of friction stir welding (FSW) tool geometries on aluminium welds were investigated using ... more Effect of friction stir welding (FSW) tool geometries on aluminium welds were investigated using different tool shoulder and pin probe geometry profiles. A combination of 27 tool shoulder and pin profile geometries were used for the experimental purpose using a design matrix. The effect of these tool geometries on the friction stir welds like the weld strength, weld cross-section area and grain sizes were investigated. The effects of the tool geometries were predicted using artificial intelligence techniques such as artificial neural networks (ANN) and fuzzy logic modelling. It was observed that, for a combination of FSW tool geometries, the ANN model was not so effective in predicting the FSW weldment characteristics, while the fuzzy logic model was able to predict the same with much lower percentage of error for the test cases.
Retour page d'accueil Chercher, sur, Tous les supports. Retour page d'accueil, ... more Retour page d'accueil Chercher, sur, Tous les supports. Retour page d'accueil, Plus de 1.622.000 de titres à notre catalogue ! Notice. ...
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