【正文】 in the Simulations Controls window and set the Environment temperature to 850 C. 16) Set the value of the Convection Coefficient to N/(s*mm*C). 17) Press Ok in the Processing Conditions window and press Ok in the Simulation Controls window. Question: What is “temperature based” stepping? This is a method by which the time step size is determined by using the calculated temperature gradient from the previous step to estimate a user defined maximum temperature change. The parameters that need to be set are the desired maximum temperature change, the largest allowable time step size and the smallest allowable time step size. Also, the Step Definition needs to be changed to Temp in order that the first step of the simulation DTMAX is calculated while the rest of steps are determined from the temperature field. . Creating New Objects Object 1: At this point, the user will insert all the objects required for this simulation. 1) Click on the Objects button in the Control window. We need to load the work piece geometry and create a mesh for it. 2) Change the Object name to Gear Tooth. 3) Click on the Geometry button in the Objects window and load the IGES file . 4) After the gear tooth has been loaded reverse the geometry to make it counterclockwise. 5) Click on the Check Geometry button to ensure that the geometry is legal. 6) Click Ok in the Geometry window. 7) After this, click on the Mesh icon in the Objects window. Set the number of mesh elements to 500 and adjust the weighting factor for the meshing such that boundary curvature has a weighting factor of 1 while leaving the other weighting factors unchanged. Set the number of thickness 安徽建筑工業(yè)學(xué)院畢業(yè)設(shè)計（論文） 44 elements 4 and the maximum size ratio between elements 3. 8) Generate the mesh for the gear tooth and press Ok. 9) Set the Material type ElasticPlastic. 10) Click on the Boundary Conditions icon and set the vertical velocity to zero for the bottom section. (Figure ). 11) Click on the thermal tab in the Boundary Conditions window to set the heat exchange boundary conditions (Figure ). 12) Set the thermal boundary conditions to Heat Exchange with the Environment for the outside part of the tooth and the bore (inner) section. 13) Press Ok when finished when applying these boundary conditions. 14) Click on the Material icon to bring up the Material Selection window. This is the window in which the material type is selected for a particular object. 15) Click on the AISI1045, COLD selection and press Ok. At this point the temperature and the phase position of the object needs to be defined. Figure : Gear tooth section with velocity boundary conditions. At this point the temperature and the phase position of the object needs to be defined. Question: What are weighting factors and why are they necessary? Weighting factors are variables that one can assign in order to emphasize or deemphasize the density of the mesh based on object parameters. By increasing the weighting factor for boundary curvature, the mesh generator will tend to place more elements in regions where the boundary of the object has higher curvature. 安徽建筑工業(yè)學(xué)院畢業(yè)設(shè)計（論文） 45 Figure : Gear tooth section with heat exchange boundary conditions. 16) Click on the Default icon and set the Temperature to 20 C and the Atom percent (weight percent) to . At this time the user will initialize the phase position of the object. 17) Click on the Objects Tabs, then click on the Elements Data Icon and click on the Transformation Tab to see where the position of the object material is defined. (Figure ) 安徽建筑工業(yè)學(xué)院畢業(yè)設(shè)計（論文） 46 Figure Element windows with Transformation data This window specifies several values in for the object phase position. The value, VOLFC, is the volume fraction of a specific phase in the object. The sum of the volume fraction values for all the phases at any time must be equal 安徽建筑工業(yè)學(xué)院畢業(yè)設(shè)計（論文） 47 to unity. The user can initialize the object to be pure binate at the beginning of the simulation by clicking on the VOLFC value for the Binate phase and then clicking on the Initialize Values icon directly to the left. Click on the Binate box to make it the active box and click on the Initialize button (I) next to the table. Set the value to 1 and click on the Ok button. Initialize the VOLFS variable for Binate to be unity as well, following the same procedure. The VOLFS variable specifies the transformation limit of a given phase. Thus, by specifying a value for VOLFS of , 100 % of the Binate is allowed to transform into Austenite. 18) Press Ok in the Initialize Elements window and then press Ok in the Elements window. 19) Click on the Properties icon in the Objects window and change the EP Initial Guess to Use previous step solution. 20) Click Ok in the Object Properties window. Question: What is meant by EP Initial Guess? In order to solve an FEM problem, a numerical solver is required. DEFORM? uses NewtonRapson or Quasi NewtonRap son to solve for the deformation of elasticplastic , for both of these methods, an initial guess is required. As the initial guess gets better, the speed and likeness of convergence increases. By default, the FEM engine uses a rigidplastic Calculation as the initial guess for an elasticplastic material. Another method that DEFORM? May implement is to perform the calculation for an elastic material. The third method is to use the result from the previous step as the initial guess. This is usually the best method if the deformation in the object is small. Object 2: This object will be used for the sole purpose of constraining object 1. 1) In the Objects window, add another object by clicking on the Add Object icon. This object number will default to 2. 2) Se