有限元分析及应用上机实验报告学院：机电工程学院专业：机械工程班级：硕士1606班*名：***学号：*********指导教师：***日期：2016.12.021.QuestionFig.1. Schematic diagram of herringbone roof truss.Question: The geometric dimensions of the chevron roof is shown in Fig.1,you should analyze it by statics，as a result you should give the displacement and axial force and axial force diagram of the deformation diagram.Conditions: The ends of the roof truss were fixed, the sectional area of the truss is 0.01m2, elastic modulus is2.0×1011 N/m2, poisson's ratio is 0.3.2.The software usedANSYS Finite element software (APDL 15.0)3.Solving processPoint 1 was choosed as the Coordinate point, horizontal to the right was the X axis，the upright direction is choosed as the Y axis to create a coordinate system. The nodes was numbered as shown in Figure 1，node 1 and node 5 was fixed，and the force on node 6,7,8 was is 1k N，the direction is opposite to the Y-axis3.1 The preparatory work before analysis（1）Specify the new file name. Select Utility>Menu> File>Change Jobname, then pop-up the dialog box Change Jobname, input the the working file name ‘2D-sp’ in the Enter New Jobname, click OK to finish the difinition, as shown in Fig.2.Fig.2. The difinition of working file name.（2）Specify a new title. Select Utility>Menu>File>Change Title，then pop-up the dialog box Change Title, input the the file name ‘2D-sp pro’ in the Enter New Title, click OK to finish the difinition, as shown in Fig.3.Fig.3. The difinition of file name.（3）Re-refresh the graphics window.Select Utility>Menu>Plot>Replot, the defined information was displayed in the graphics window.（4）Define the structural analysis.Run the main menu Main Menu>Preferences，then choose the Structural, click OK to complete the definition of the analysis type , as shown in Fig.4.Fig.4. The definition of the structural analysis.3.2 Define the element typeRun the main menu Main Menu>Preprocessor>Element Type>Add, then pop-up the dialog box Element Types, click the button Add to build a new element type, then pop-up the dialog box Library of Element Types, choose Link first, and then select 3D finit stn 180（Link1），click the button OK to finish the definition of the element type, click the button Close to finish the settings, as shown in Fig.5.Fig.5. The definition of the element type.3.3 Define the real constantsRun the main menu Main Menu>Preprocessor>Real Constants Add, then pop-up the dialogbox of real constants, click the button Add to come into the constant input dialog box, as shown in Fig.6. Input the sectional area of the truss (0.01m2) in AREA, click the button OK to finish the input of the real constants, as shown in Fig.7.Fig.6. Get into the instance constant dialog box.Fig.7. The d efinition of the real constants.3.4 Define the material propertiesRun the main menu Main Menu>Preprocessor>Material Props>Material Models, then pop-up the dialog box of material properties, and select Structure、Linear、Elastic、Isotropic, as shown in Fig.8.When the selection was completed, appeared the Material Properties input dialog box appears，then input elastic modulus 2e11 and the poisson's ratio 0.3, as shown in Fig.9, click OK to finish the input of the material properties.Fig.8. Get into the setting of material properties.Fig.9. The difinition of the material properties.3.5 Establish the analytical model（1）Create the nodes. The coordinates of the 1—8 nodes as shown in Table.1. Run the main menu Main Menu>Preprocessor> Modeling>Create>Nodes>In Active CS. The create node entry dialog box appears as shown in Fig.10. Input the first node 1 and its’ x, y, z coordinate, then click Apply to finish the creating of the node. Similarly, create the nodes 2—8, click OK to finish the creating of the nodes, as shown in Fig.10.Fig.10. The dialog box of nodes input.Fig.11. The creation of the nodes.The created nodes as shown below：（2）Created the bar unitRun the main menu Main Menu>Preprocessor>Modeling>Create >Elements>Auto Numbered>Thru Nodes, then pop-up the dialog box Element from Nodes, pick the nodes 1 and 2, click Apply to complete the first lever unit . Similarly, pick both ends of the rod in turn, click Apply to complete the lever unit, lastly click OK, as shown in Fig.12.Fig.12. Model establishment of the herringbone truss.3.6 Apply constraints and loads（1）Impose constraintsRun the main menu Main Menu>Solution>Define Loads>Apply>Structural> Displacement>On Nodes, the pick menu appears, select nodes 1 and 5 in turn, then click OK, the constraint definition dialog box appears，as shown in Fig.13. Choose All DOF to constrain all degrees of freedom，other items by default，then click the button OK to complete the constraint definition.Fig.13. Impose the constraints.（2）Apply the loadRun the main menu Main Menu>Solution>Define Loads>Apply>Structural> Force/Moment>On Nodes, the pick menu appears, select nodes 6, 7 and 8 in turn, click OK , then the load definitions dialog box appears，as shown in Fig.14.The load type is concentrated force FY. The value is -1000 , Then click the OK button to complete the application of the load.Fig.14. The application of the load.Figure after load application as shown below:3.7 SolutionRun the main menu Main Menu>Solution>Solve>Current LS, then pop-up the dialog box Solve Current Load Step, click STAT Command, then click STAT Command>File>Close toclose the STAT Command window, then click OK to finish the steps.Then the computer started the solution. The promption of "Solution is done" indicated that the solution was completed, click the button Close to finish the solution, as shown in Fig.15.Fig.15. The process of the solution.3.8 View the analysis results（1）Define the cell table. In ANSYS, some data can not be directly accessed, so we need to complete the definition of cell to access the results.Run the main menu Main Menu>General Postproc>Element Table>Define Table, then pop-up the dialog box, click the button Add. The unit table definition dialog box appeared, as shown in Fig.16.Fig.16a. The definition of the cell table.Fig.16b. The definition of the cell table.（2）Display the axial force (axial stress) diagram. Run the main menu MainMenu>General Postproc>Plot Results> Contour Plot>Elem Table. Then pop-up the cell table result selection dialog box , as shown in Fig.17. Choose A-STR and click OK to view the axial force (axial stress) diagram , as shown in Fig.18.Fig.17. Contor plot of Element Table Data.（3）Display the result.The result as shown in Fig.18.Fig.18. The final result.。