IJSRD || National Conference on Recent Trends & Innovations in Mechanical Engineering || April 2016 ISSN(online): 2321-0613 ©IJSRD 2016 Published by IJSRD 13 Simulation of Thermal Stress of SS316 using ANSYS Harinadh Vemanaboina 1 G.Edison 2 Suresh Akella 3 1 Research Scholar 2,3 Professor 1,2 SMEC, VIT University, Vellore, Tamilnadu, India 3 Sreyas Institute of Engineering & Technology, India Abstract— Welding is widely used in all the fabrication processes for the development of complex structural components. The weld distortion is one of the major constraints which cannot be completely avoided irrespective of material type and thickness. 3D transient thermal finite element model is established to measure the thermal stress and weldments. The temperature stress modeling is one of the complex processes which utilize the weld parameters and material properties at higher temperatures. A Suitable heat flux is to be given as input for the developed model to analyze welding process. The temperature distribution and stress analysis have been carried out with developed model by using the temperature dependent material properties of SS316 using ANSYS. Key words: Welding, Thermal Stresses I. INTRODUCTION Welding is a process used in the fabrication of various steel structures for applications from thin sections to thicker sections in various applications like pressure vessels, chemical plants and nuclear reactors. The main problem associated with welding is the presence of residual stresses and deformations developed within the sections which may cause the failure at the later stages by Masubuchi [7]. During the welding process, the material exposed to heat flux causes a phase change of the metal during melting. The temperature distribution is non-uniform like fusion zone with molten metal, heat affected zone and the base metal zone. The present study is focused on the understanding of the heat flux mechanism with heat source used for TIG weld process with developed constant heat source model applied to the stainless steel, SS316 material by using the temperature dependent properties and finite element approach. The temperature distribution is estimated which can further give the estimation of the weld deformations and stresses. II. FORMATION & SIMULATION OF WELDING PROCESS The heat energy equations are referenced in many including Frewin [5]. For an isotropic, conductive material with equal coefficient of conductivity kx, ky, kz (W/mK) in all three chosen orthogonal coordinates. Equation (1) gives the heat energy in the weld area with temperature, T (K) obtained both in spatial, x, y, z (m) and temporal, t (sec), terms. Q (W/m 3 or J/m 3 s) is the net heat from the input and the losses in the form of convection & radiation. The boundary conditions given are T0(x, y, z, 0) throughout the body at time zero or at the starting of the weld, this is an essential boundary condition. In addition, the natural boundary conditions have to apply consisting of normal conduction     heat flux q, convection h (T-T0), and the radiation term, ) ( 4 0 4 T T     2   2  +   2   2  +   2   2  +  =  [   −   ] (1) Together, the boundary conditions are summed up as: 0 ) 0 ( ) 0 ( 4 4       T T T T h q K n  (2) When symmetric boundary and insulation boundaries are considered as adiabatic, with no heat flowing through the surface, they are obtained by making convection zero, and conduction zero from the surface. Where, Kn is the thermal conductivity normal to the surface in W/mK, h is the convective heat transfer coefficient in W/m 2 K, ε is emissivity of surface radiating, σ is the Stefan Boltzmann’s constant, which 5.67*10 -8 , W/m 2 K 4 . When it is difficult to use radiation boundary condition, it is combined with convective heat flux by using a modified coefficient, hr, for hot rolled steel plates with an error of about 5% is, ℎ  = 2.4 ∗ 10 −3 ∈ 1.61 (3) Radiation inclusion will increase solution time by about three times and hence combined with convection. A. Finite Element for Simulation The heat equations (1) can be represented in tensor form so the elemental transient heat equation is obtained and later summed to get the system equation which is analysed with time. ⌊()⌋{} + [()]{} = {()} (4) Where K is a temperature dependent conductivity matrix. C is the temperature dependent capacitance matrix based on specific heat its product with the rate of temperature gives heat. The above equation can be solved numerically, with standard FEM models with Crank-Nicholson or Euler time integration models. An initial temperature Ti is assumed K, C and