A new configuration for space radiator is proposed introducing a fin of regular hollow pyramidal ... more A new configuration for space radiator is proposed introducing a fin of regular hollow pyramidal shape with triangular cross section, giving a higher improvement in heat loss per unit mass than that of other corresponding configurations previously proposed under same working conditions. The significance of the present configuration and its advantage over other regular hollow configurations are discussed and effect of various design parameters on heat transfer is analyzed in presence of radiation interaction with an isothermal base attached to it. Optimum parameters are identified for which improvement in heat loss per unit mass is the maximum. It is found that the fin efficiency decreases with increase in the emissivity & height of the fin and increases with increase in thickness & top radius of the fin. Correlations are presented for optimum design parameters, optimum improvement in heat loss per unit mass and fin efficiency.
Multidiscipline Modeling in Materials and Structures, 2008
Friction stir welding (FSW), a process that involves joining of metals without fusion of filler m... more Friction stir welding (FSW), a process that involves joining of metals without fusion of filler materials. It is used already in routine, as well as critical application for the joining of structural components made of Aluminum and its alloys. Indeed it has been convincingly ...
Proceedings of The Institution of Mechanical Engineers Part C-journal of Mechanical Engineering Science, 2009
Abstract: The energy of a laser beam is generally calculated based on the laser power and its pro... more Abstract: The energy of a laser beam is generally calculated based on the laser power and its processing speed. In this work, the laser welding modes such as conduction, conduction penetration, and keyhole welding of thickness 1.6, 2, and 2.5 mm AISI304 stainless steel ...
... The FEM program requires the con-stitutive constants determined by the material property test... more ... The FEM program requires the con-stitutive constants determined by the material property tests, the dimensions of the tool geometry, and the fric-tion coefficient/z. The optimum friction coefficient was obtained by matching the simulated strain at the pole to the measured value. ...
Laser welding is a high power density welding technology, which has the capability of focusing th... more Laser welding is a high power density welding technology, which has the capability of focusing the beam power to a very small spot diameter. Its characteristics such as high precision and low and concentrated heat input, helps in minimizing the micro-structural modifications, residual stresses and distortions on the welded specimens. In this study, finite element method (FEM) is adopted for predicting the bead geometry in laser welding of 1.6 mm thick AISI304 stainless steel sheets. A three-dimensional finite element model is used to analyze the temperature distribution in a T-joint weld produced by the laser welding process. Temperature-dependent thermal properties of AISI304 stainless steel, effect of latent heat of fusion, and the convective and radiative boundary conditions are included in the model. The heat input to the model is assumed to be a 3D conical Gaussian heat source. The finite element code SYSWELD, along with a few FORTRAN subroutines, is employed to obtain the numerical results. The T-joint welds are made using a Nd:YAG laser having a maximum power of 2 kW in the continuous wave mode. The effect of laser beam power, welding speed and beam incident angle on the weld bead geometry (i.e. depth of penetration and bead width) are investigated. Finally, the shapes of the molten pool predicted by the numerical analysis are compared with the results obtained through the experimentation. The comparison shows that they are in good agreement.
International Journal of Advanced Manufacturing Technology, 2009
The investigation of transient temperature profiles of a weld joint produced by the laser welding... more The investigation of transient temperature profiles of a weld joint produced by the laser welding process is presented. A three-dimensional finite element model is developed using a commercial finite element code ANSYS in order to obtain the behavior of temperature field and molten pool shape during the welding process. A three-dimensional conical Gaussian heat source is employed as a heat source model for performing a non-linear transient thermal analysis. The temperature-dependent material properties of AISI 304 stainless steel sheet are taken into account, which has a great influence on the temperature fields indicated by the simulation results. The effect of latent heat and the convective and radiative boundary conditions are also included in the model. A series of laser welds are performed using a 2-kW continuous wave Nd:YAG laser welding system. The experimental trials are conducted by varying the laser input parameters namely beam power, welding speed, and beam incident angle to validate the model. The results show that there is a good agreement between the finite element simulation and the experimental observations.
Multidiscipline Modeling in Materials and Structures, 2009
This paper presents the influence of beam incidence angle on austenitic stainless steel sheet sub... more This paper presents the influence of beam incidence angle on austenitic stainless steel sheet subjected to a high density laser beam having Gaussian power density distribution. Bead-on trials are conducted on 3.15 mm thick commercial AISI 304 austenitic stainless steel sheet using a Nd:YAG laser source with a maximum output of 2kW in the continuous wave mode. The effects of
A new configuration for space radiator is proposed introducing a fin of regular hollow pyramidal ... more A new configuration for space radiator is proposed introducing a fin of regular hollow pyramidal shape with triangular cross section, giving a higher improvement in heat loss per unit mass than that of other corresponding configurations previously proposed under same working conditions. The significance of the present configuration and its advantage over other regular hollow configurations are discussed and effect of various design parameters on heat transfer is analyzed in presence of radiation interaction with an isothermal base attached to it. Optimum parameters are identified for which improvement in heat loss per unit mass is the maximum. It is found that the fin efficiency decreases with increase in the emissivity & height of the fin and increases with increase in thickness & top radius of the fin. Correlations are presented for optimum design parameters, optimum improvement in heat loss per unit mass and fin efficiency.
Multidiscipline Modeling in Materials and Structures, 2008
Friction stir welding (FSW), a process that involves joining of metals without fusion of filler m... more Friction stir welding (FSW), a process that involves joining of metals without fusion of filler materials. It is used already in routine, as well as critical application for the joining of structural components made of Aluminum and its alloys. Indeed it has been convincingly ...
Proceedings of The Institution of Mechanical Engineers Part C-journal of Mechanical Engineering Science, 2009
Abstract: The energy of a laser beam is generally calculated based on the laser power and its pro... more Abstract: The energy of a laser beam is generally calculated based on the laser power and its processing speed. In this work, the laser welding modes such as conduction, conduction penetration, and keyhole welding of thickness 1.6, 2, and 2.5 mm AISI304 stainless steel ...
... The FEM program requires the con-stitutive constants determined by the material property test... more ... The FEM program requires the con-stitutive constants determined by the material property tests, the dimensions of the tool geometry, and the fric-tion coefficient/z. The optimum friction coefficient was obtained by matching the simulated strain at the pole to the measured value. ...
Laser welding is a high power density welding technology, which has the capability of focusing th... more Laser welding is a high power density welding technology, which has the capability of focusing the beam power to a very small spot diameter. Its characteristics such as high precision and low and concentrated heat input, helps in minimizing the micro-structural modifications, residual stresses and distortions on the welded specimens. In this study, finite element method (FEM) is adopted for predicting the bead geometry in laser welding of 1.6 mm thick AISI304 stainless steel sheets. A three-dimensional finite element model is used to analyze the temperature distribution in a T-joint weld produced by the laser welding process. Temperature-dependent thermal properties of AISI304 stainless steel, effect of latent heat of fusion, and the convective and radiative boundary conditions are included in the model. The heat input to the model is assumed to be a 3D conical Gaussian heat source. The finite element code SYSWELD, along with a few FORTRAN subroutines, is employed to obtain the numerical results. The T-joint welds are made using a Nd:YAG laser having a maximum power of 2 kW in the continuous wave mode. The effect of laser beam power, welding speed and beam incident angle on the weld bead geometry (i.e. depth of penetration and bead width) are investigated. Finally, the shapes of the molten pool predicted by the numerical analysis are compared with the results obtained through the experimentation. The comparison shows that they are in good agreement.
International Journal of Advanced Manufacturing Technology, 2009
The investigation of transient temperature profiles of a weld joint produced by the laser welding... more The investigation of transient temperature profiles of a weld joint produced by the laser welding process is presented. A three-dimensional finite element model is developed using a commercial finite element code ANSYS in order to obtain the behavior of temperature field and molten pool shape during the welding process. A three-dimensional conical Gaussian heat source is employed as a heat source model for performing a non-linear transient thermal analysis. The temperature-dependent material properties of AISI 304 stainless steel sheet are taken into account, which has a great influence on the temperature fields indicated by the simulation results. The effect of latent heat and the convective and radiative boundary conditions are also included in the model. A series of laser welds are performed using a 2-kW continuous wave Nd:YAG laser welding system. The experimental trials are conducted by varying the laser input parameters namely beam power, welding speed, and beam incident angle to validate the model. The results show that there is a good agreement between the finite element simulation and the experimental observations.
Multidiscipline Modeling in Materials and Structures, 2009
This paper presents the influence of beam incidence angle on austenitic stainless steel sheet sub... more This paper presents the influence of beam incidence angle on austenitic stainless steel sheet subjected to a high density laser beam having Gaussian power density distribution. Bead-on trials are conducted on 3.15 mm thick commercial AISI 304 austenitic stainless steel sheet using a Nd:YAG laser source with a maximum output of 2kW in the continuous wave mode. The effects of
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Papers by Siva Shanmugam