1、计算机在材料科学中的应用上机实验八计算机在材料科学中的应用上机实验八铸件凝固过程的分析（Solidification of a Casting）3.1.1. Problem Specification Applicable ANSYS Products: ANSYS/Multiphysics, ANSYS/Mechanical, ANSYS/ED Level of Difficulty: moderate Interactive Time Required: 60 to 90 minutes Discipline: thermal Analysis Type: nonlinear transi
2、ent Element Types Used: PLANE55 ANSYS Features Demonstrated: solid modeling, conduction, convection, phase change, selecting, solution control, time-history postprocessing, use of a get function Applicable Help Available: (NOTE: The contents of the particular help topic that you choose will appear i
3、n this browser window, replacing the information you are now reading. When you are finished reading the help topic, click on the browsers Back button to return to this tutorial.) Thermal Analysis Guide - Chapter 3. Transient Thermal Analysis, Elements Reference - PLANE553.1.2. Problem DescriptionThi
4、s is a transient heat transfer analysis of a casting process. The objective is to track the temperature distribution in the steel casting and the mold during the solidification process, which occurs over a duration of 4 hours. The casting is made in an L-shaped sand mold with 4 inch thick walls. Con
5、vection occurs between the sand mold and the ambient air.GivenMaterial Properties for SandConductivity (KXX)0.025 Btu/(hr-in-oF)Density (DENS)0.054 lb/in3Specific heat (C)0.28 Btu/(lb-oF)Conductivity (KXX) for Steelat 0oF1.44 Btu/(hr-in-oF)at 2643oF1.54at 2750oF1.22at 2875oF1.22Enthalpy (ENTH) for S
6、teelat 0oF0.0 Btu/in3at 2643oF128.1at 2750oF163.8at 2875oF174.2Initial ConditionsTemperature of steel2875 oFTemperature of sand80 oFConvection PropertiesFilm coefficient0.014 Btu/(hr-in2-oF)Ambient temperature80 oFApproach and AssumptionsA 2-D analysis of a one unit thick slice will be performed. Ha
7、lf symmetry is used to reduce the size of the model. The lower half is the portion modeled.The mold material (sand) has constant material properties. The casting (steel) has temperature-dependent thermal conductivity and enthalpy; both are input in a table of values versus temperature. The enthalpy
8、property table captures the latent heat capacity of the metal as it solidifies. Radiation effects are ignored.Solution control is used to establish several nonlinear options, including automatic time stepping. Automatic time stepping determines the proper time step increments needed to converge the
9、phase change nonlinearity. This means that smaller time step sizes will be used during the transition from molten metal to solid state.3.1.3. Prepare for a Thermal Analysis改变工作文件名：Utility MenufileChange Jobname CastingNew log and error files? Yes3.1.3.1. Step 1: Set preferences.To Set Preferences:1.
10、 Main Menu Preferences2. (check) “Individual discipline(s) to show in the GUI” = Thermal3. OK3.1.4 Build Geometry1. Define keypoints.To take advantage of symmetry in this problem, model only half of the L. First, construct the trapezoid representing the outline of the mold by defining the four corne
11、r points of the trapezoid and then defining an area connecting these four keypoints.1. Main Menu: Preprocessor -Modeling-Create -Keypoints -In Active CS 2. Enter 1 for keypoint number - 3. Enter 0,0,0 for coordinate locations - 4. Apply to define keypoint 1 (keypoint will be at 0,0,0) - 5. Enter 2 f
12、or keypoint number - 6. Enter 22,0,0 for coordinate locations - 7. Apply to define keypoint 2 - 8. Enter 3 for keypoint number - 9. Enter 10,12,0 for coordinate locations - 10. Apply to define keypoint 3 - 11. Enter 4 for keypoint number - 12. Enter 0,12,0 for coordinate locations - 13. OK - Remove
13、the global triad symbol so that it wont obscure the view of the keypoint at the origin. 14. Utility Menu: PlotCtrls-Window Controls-Window Options 15. Set location of triad to Not shown - 16. OK - .2. Create areas for mold and casting.Now create an area for the mold by connecting the four keypoints.
14、1. Main Menu: Preprocessor -Modeling-Create -Areas-Arbitrary -Through KPs 2. Pick keypoints 1 through 4 in sequential order. You can see the lines form as you pick. 3. OK to create area (in picking menu) 4. Toolbar: SAVE_DB To create the area for the casting, carve out the area from the first area.
15、This is done by creating a rectangle primitive (dont worry about the exact dimensions on the right side; it can be longer than it needs to be), overlapping the areas (Boolean operation), and then deleting the extraneous area left over.5. Main Menu: Preprocessor-Modeling-Create-Areas-Rectangle-By Dim
16、ensions 6. Enter 4 and 22 for X-coordinates - 7. Enter 4 and 8 for Y-coordinates - 8. OK - 9. Utility Menu: PlotCtrls- Numbering 10. Turn on keypoint numbers - 11. Turn on area numbers - 12. OK - 13. Utility Menu: Plot- Areas 14. Main Menu: Preprocessor -Modeling-Operate -Booleans-Overlap-Areas 15.
17、Pick All to choose both areas for overlapping - 16. Main Menu: Preprocessor -Modeling-Delete -Area and Below 17. Pick area 3 18. OK (in picking menu) to delete area 3 19. Utility MenufileSave as Castinggeom.db3.1.5. Define Materials3.1.5.1. Step 3: Define material properties.Define the sand mold mat
18、erial properties as material number 1. These are not functions of temperature.1. Main Menu Preprocessor Material Props Material Models2. (double-click) “Thermal”, then “Conductivity”, then “Isotropic”3. “KXX” = 0.0254. OK5. (double-click) “Specific Heat”6. “C” = 0.287. OK8. (double-click) “Density”9
19、. “DENS” = 0.5410. OKNotePC Users: You can view a demo on defining one material model by pointing your Internet Explorer browser to the following URL address: The metal casting is defined as material number 2. These properties change significantly as the metal cools down from the liquid phase to the
20、 solid phase. Therefore, they are entered in a table of properties versus temperature.First define the temperature dependent thermal conductivity.11. Material New Model 12. “Define Material ID” = 213. OK14. (double-click) “Isotropic”15. Add Temperature three times to create fields for the four tempe
21、ratures.16. “T1” = 017. “T2” = 264318. “T3” = 275019. “T4” = 287520. “KXX” at “T1” = 1.4421. “KXX” at “T2” = 1.5422. “KXX” at “T3” = 1.2223. “KXX” at “T4” = 1.22You will now copy the four temperatures so you will be able to paste them into the Enthalpy dialog box.24. Select the temperatures by holdi
22、ng the left mouse button and dragging across the temperature row so that the row is highlighted.25. Ctrl then c to copy the temperatures.26. OKNext, define the temperature dependent enthalpy.27. (double-click) “Enthalpy”28. Add Temperature three times to create fields for the four temperatures.29. P
23、aste the temperatures into the dialog box by highlighting the T1 temperature field, and pressing Ctrl then v.30. “ENTH” at “T1” = 031. “ENTH” at “T2” = 128.132. “ENTH” at “T3” = 163.833. “ENTH” at “T4” = 174.234. OKNotePC Users: You can view a demo on adding a temperature dependent material model by
24、 pointing your Internet Explorer browser to the following URL address: 3.1.5.2. Step 4: Plot material properties vs. temperature.1. (double-click) “Thermal conduct. (iso)” under Material Model Number 2.2. Graph3. OKNotePC Users: You can view a demo on graphing a temperature dependent material model
25、by pointing your Internet Explorer browser to the following URL address: 4. (double-click) “Enthalpy” under the right or left window.5. Graph6. OK7. Material Exit8. Toolbar: SAVE_DB3.1.5.3. Step 5: Define element type.You will now define the element type as PLANE55.1. Main Menu Preprocessor Element
26、Type Add/Edit/Delete2. Add .3. “Thermal Solid” (left column)4. “Quad 4node 55” (right column)5. OK6. Close7. Utility MenufileSave asCastingmodel.db3.1.6. Generate Mesh3.1.6.1. Step 6: Mesh the model.1. Utility Menu Plot Areas Specify a SmartSize of 4. This will allow a slightly finer mesh than the d
27、efault and yet the resulting number of elements will be within the ANSYS ED program limits for the maximum number of elements.2. Main Menu Preprocessor Meshing MeshTool3. (check) “Smart Size”4. (slide) “Fine Course” = 45. MeshMesh the mold area first. Note that the material attribute reference numbe
28、r defaults to 1 and there is no need to set attributes before meshing the area.6. Pick the mold area A5 (Hint: Place the mouse cursor on top of the A5 label when you pick - this is the picking hot spot, based on the centroid of the area.). 7. OKBefore meshing the casting area, set the material attri
29、bute to that of steel (material 2).8. (drop down in MeshTool) “Element Attributes” = Global, then Set 9. (drop down) “Material number” = 210. OK11. Utility Menu Plot Areas12. Mesh in MeshTool13. Pick area A414. OK15. Close in MeshTool16. Utility Menu Plot Elements Note: The mesh you obtain may vary
30、slightly from the mesh shown here. As a result of this, you may see slightly different results during postprocessing. For a discussion of results accuracy, see Planning Your Approach in the ANSYS Modeling and Meshing Guide.To verify that the elements have the right materials, plot them with different colors for different materials.17. Utility Menu PlotCtrls Numbering18. (drop down) “Elem / Attrib numbering” = Material numbers19. OKNote: the elements of mat
