Spur Gears Static Stress Analysis with Linear Material Models

Size: px

Start display at page:

Download "Spur Gears Static Stress Analysis with Linear Material Models"

Opal Bennett
5 years ago
Views:

$75 in-lb is applied to the pinion. Use the Exercise A.dmit file located in the "Exercise A\input file" directory. The gears are manufactured out of steel and are based on a diametral pitch of 8.$

1 Exercise A Spur Gears Static Stress Analysis with Linear Material Models Beam and Brick Elements Objective: Geometry: Determine the stress distribution in the spur gears when a moment of in-lb is applied to the pinion. Use the Exercise A.dmit file located in the "Exercise A\input file" directory. The gears are manufactured out of steel and are based on a diametral pitch of 8. There are 10 teeth in the pinion, 24 teeth in the main gear and the width of both gears is 0.25 inches. Loads: Constraints: Elements: A moment of in-lb will be applied to the pinion. A joint will be created at the center of the pinion. The pinion will be constrained to only rotate about its center. The main gear will be fully fixed at the shaft hole to simulate a locked condition. Beam Brick Material: Contact: Steel (ASTM-A36) Surface contact will be defined between the pinion and the main gear. Finite Element Analysis in Practice Gear Design Supplement /11/2005 1

2 2 Finite Element Analysis in Practice Gear Design Supplement /11/2005

3 Solution Opening the Model The CAD Solid Model environment of FEMPRO is used to create a mesh on all solid models. You can open CAD models from any of the CAD solid modelers or universal CAD formats that ALGOR supports. "Start: Programs: ALGOR V17: FEMPRO" Press the Windows "Start" button. Select the "Programs" pull-out menu and then select the "ALGOR V17" pull-out menu. Select the "FEMPRO" command. The ALGOR FEMPRO application will now appear. Press the "Open" icon at the left side of the dialog. Navigate to the Exercise A\input file directory and change the "Files of type" drop-down box to the "ALGOR Direct Memory Image Transfer Files (*.dmit)" option in the ALGOR Files section as shown in Figure 1. Then select the file Exercise A.dmit and press the "Open" button. Figure 1: Select Type of File to Open A dialog will appear asking you to choose the design scenario for this model. Press the button to accept the default of "Single analysis: Static Stress with Linear Material Models". Finite Element Analysis in Practice Gear Design Supplement /11/2005 3

Meshing the Model "Mesh: Model Mesh Settings " "Options " If the "Model Mesh Settings" dialog does not automatically appear, use the "Mesh: Model Mesh Settings " command to bring it up.

4 Meshing the Model "Mesh: Model Mesh Settings " "Options " If the "Model Mesh Settings" dialog does not automatically appear, use the "Mesh: Model Mesh Settings " command to bring it up. Press the "Options " button on the "Model Mesh Settings" dialog to change the default mesh settings. Click on the "Options" tab. 15 Enter a value of "15" in the "Angle (1-90 degrees)" field in the "Edge curve refinement" section as shown in Figure 2. Figure 2: Model Mesh Settings Dialog Click on the "Model" icon on the left side of the "Model Mesh Settings" dialog Enter a value of "0.01" in the "Tolerance value" field. Press the button to accept the changes. "Mesh model" Press the "Mesh model" button to create the mesh. "No" Press the "No" button when asked to view the mesh results. 4 Finite Element Analysis in Practice Gear Design Supplement /11/2005

Right click on the "Contact" heading in the tree view and select the "Surface Contact" command as shown in Figure 3 below.

5 Defining Surface Contact The default contact option of "Bonded" will be changed to "Surface Contact". This type of contact will prevent the surfaces from penetrating each other, but still allow them to pull away from each other with no resistance. Right click on the "Contact" heading in the tree view and select the "Surface Contact" command as shown in Figure 3 below. Using the Joint Creation Utility Figure 3: Setting the Contact Type The joint creation utility will be used to create a pin joint (i.e., a "spider-web" of beam elements) at the location of the shaft hole in the pinion. The pin joint will facilitate constraining of the pinion to rotate about its center and also the application of the moment load. "View: Rotate" <Ctrl> Access the VIEW pull-down menu and select the "Rotate" command. Using the mouse, rotate the model around to get a clear view of the shaft hole in the pinion. Zoom and pan operations can also be used to get a closer view. Click on one of the two surfaces for the shaft hole in the pinion. The surface will turn to a magenta color to indicate that it is selected. While holding down the <Ctrl> key, click on the second surface of the shaft hole in the pinion. Both surfaces for the hole should now be selected, as shown in Figure 4 below. Finite Element Analysis in Practice Gear Design Supplement /11/2005 5

Figure 4: Selected Surfaces for Joint Creation Utility

pull-down menu and select the "FEA Editor" command to

6 Figure 4: Selected Surfaces for Joint Creation Utility "Create Joint" Right click anywhere in the display area. Select the "Create Joint" command. Press the button to create the pin joint as shown in Figure 5 below. Figure 5: Pin Joint "Tools: FEA Editor" Access the TOOLS pull-down menu and select the "FEA Editor" command to move to the FEA Editor environment to set up the analysis. 6 Finite Element Analysis in Practice Gear Design Supplement /11/2005

7 Setting up the Analysis in the FEA Editor Environment The FEA Editor environment is used to specify all element and analysis parameters for a model and to apply any loads and constraints. When transferring a new model to the FEA Editor environment, a red X will appear on several items in the tree view. The presence of a red X is an indication that this important data item has not yet been specified. All of the red Xs will need to be eliminated before the model is ready for analysis. Units Definition A unit system will be specified to match the one used in the original 3-D solid model file. In the "Units Definition" dialog, press the button to accept the default unit system of "English (in)". Modifying the Pin Joint The element type for the pin joint will be changed from the default of truss elements to beam elements in order to support the application of a moment load. "Modify: Description..." PIN JOINT "Beam" "Modify Element Definition..." Right click on the heading for Part 3 in the tree view. Select the "Modify" pull-out menu and then select the "Description " command. Type in "PIN JOINT" for the "Description". Press the button to accept the change to the description for Part 3. Right click on the "Element Type" heading for Part 3 in the tree view. Select the "Beam" command. Right click on the "Element Definition" heading for Part 3 in the tree view. Select the "Modify Element Definition..." command. Press the button on the "Element Definition" dialog to accept the default sectional properties. Assignment of Material Properties All components of the spur gear assembly, including the beams for the pin joint, are manufactured out of steel. Right click on the "Material" heading for Part 1 in the tree view. "Modify Material " Select the "Modify Material..." command. "Steel (ASTM - A36)" Scroll down and select the "Steel (ASTM - A36)" item from the list of available materials. "View Properties" Press the "View Properties" button to view the material properties associated with this type of steel. Press the button to close the properties window. Press the button to accept the material selected for Part 1. Finite Element Analysis in Practice Gear Design Supplement /11/2005 7

Repeat this same procedure to define the material properties for Parts 2 and 3. After assigning the material properties, all red Xs should now be removed from the tree view.

8 Repeat this same procedure to define the material properties for Parts 2 and 3. After assigning the material properties, all red Xs should now be removed from the tree view. Constraining and Loading the Pinion The pinion will be constrained so that it can only rotate about its center. In addition, a moment will be applied at the center to simulate a torque loading. "View: Orientation: XY Top" "View: Zoom Area" "Selection: Shape: Rectangle" "Selection: Select: Vertices" Access the VIEW pull-down menu and select the "Orientation" pull-out menu. Select the "XY Top" command. Access the VIEW pull-down menu and select the "Zoom Area" command. Move the cursor to a position just below and to the left of the pinion and click. Then, move the cursor to a position just above and to the right of the pinion and click to zoom in on the pinion. Access the SELECTION pull-down menu and select the "Shape" pull-out menu. Select the "Rectangle" command. Access the SELECTION pull-down menu and choose the "Select" pull-out menu. Select the "Vertices" command. Refer to Figure 6 below. Move the cursor to a position just below and to the left of the center of the pin joint and click. Then, move the cursor to a position just above and to the right of the center of the pin joint and click to select the two vertices along the axis of the pin joint. Figure 6: Rectangle Select of Vertices "Add: Nodal Boundary Conditions " Right click anywhere in the display area. Select the "Add" pull-out menu and then select the "Nodal Boundary Conditions " command. Activate the "Tx", "Ty", "Tz", "Rx" and "Ry" checkboxes in the "Constrained DOFs" section to activate the constraints in these directions. Note that the "Rz" checkbox is not constrained so that the pinion can pivot about these vertices. 8 Finite Element Analysis in Practice Gear Design Supplement /11/2005

"Add: Nodal Moments " Press the button to apply these constraints to the selected vertices. A red circle will appear on each vertex to indicate that it is partially constrained.

9 "Add: Nodal Moments " Press the button to apply these constraints to the selected vertices. A red circle will appear on each vertex to indicate that it is partially constrained. With the vertices still selected, right click anywhere in the display area. Select the "Add" pull-out menu and then select the "Nodal Moments " command Type " " in the "Magnitude" field. This will divide the total moment of in-lb equally between the 2 selected vertices. "Z" In the "Direction" section, select the "Z" radio button to specify that the moment will act about the Z axis. Press the button to apply the moments to the selected vertices. A blue circular arrow will appear on each vertex, as shown in Figure 7 below, to indicate that a moment is applied to the vertex. Figure 7: Moments Applied to Pinion Constraining the Main Gear The shaft hole on the main gear will be fully constrained to simulate a locked condition. "View: Enclose" "Selection: Select: Surfaces" Access the VIEW pull-down menu and select the "Enclose" command to enclose the model. Access the SELECTION pull-down menu and choose the "Select" pull-out menu. Select the "Surfaces" command. Refer to Figure 8 below. Move the cursor to a position just below and to the left of the shaft hole in the main gear and click. Then, move the cursor to a position just above and to the right of the shaft hole and click to select the two surfaces for the hole. Finite Element Analysis in Practice Gear Design Supplement /11/2005 9

Press the button to apply the constraints. Red triangles will appear on each vertex of the selected surfaces to indicate that they are fully constrained.

10 Figure 8: Rectangle Select of Gear Surfaces "Add: Surface Boundary Conditions " "Fixed" Right click anywhere in the display area. Select the "Add" pull-out menu and then select the "Surface Boundary Conditions " command. Press the "Fixed" button to fully constrain all 6 degrees of freedom. Press the button to apply the constraints. Red triangles will appear on each vertex of the selected surfaces to indicate that they are fully constrained. Analysis "Analysis: Perform Analysis " Access the ANALYSIS pull-down menu and select the "Perform Analysis " command to run the analysis. At the completion of the analysis, FEMPRO will automatically transfer to the Results environment. 10 Finite Element Analysis in Practice Gear Design Supplement /11/2005

11 Results Evaluation and Presentation By default, the von Mises stress results are displayed, as shown in Figure 9. Figure 9: von Mises Stress Results "Results: Displacement: Magnitude" Access the RESULTS pull-down menu and select the "Displacement" pull-out menu. Select the "Magnitude" command to view the displacement results as depicted in Figure 10 below. Figure 10: Displacement Results Finite Element Analysis in Practice Gear Design Supplement /11/

Evaluating Contact Forces "View: Orientation: Isometric" "Results: Element Forces and Moments: 1) Axial Force" Access the VIEW pull-down menu and select the "Orientation" pull-out menu.

Select the "1) Axial Force" command to view the contact forces in the contact elements as shown in Figure 11 below.

12 Evaluating Contact Forces "View: Orientation: Isometric" "Results: Element Forces and Moments: 1) Axial Force" Access the VIEW pull-down menu and select the "Orientation" pull-out menu. Select the "Isometric" command. Access the RESULTS pull-down menu and select the "Element Forces and Moments" pull-out menu. Select the "1) Axial Force" command to view the contact forces in the contact elements as shown in Figure 11 below. Figure 11: Contact Forces "Contact Force " In the tree view, right click on the "Contact" heading. Select the "Contact Force " command to show the total of all contact forces as approximately 160 lbf. This completes the exercise. To review a completed archive of this exercise, refer to the file Exercise A.ach in the Exercise A\results archive directory. 12 Finite Element Analysis in Practice Gear Design Supplement /11/2005

ME Week 12 Piston Mechanical Event Simulation

ME Week 12 Piston Mechanical Event Simulation Introduction to Mechanical Event Simulation The purpose of this introduction to Mechanical Event Simulation (MES) project is to explorer the dynamic simulation environment of Autodesk Simulation. This