Thermal Stress Analysis

Transcription

1 Thermal Stress Analysis Determine the temperature-induced stresses in a disk brake rotor. Lesson: Thermal Stress Analysis of a Disk Brake Rotor In this exercise we'll perform a Thermal Stress analysis on a disk brake rotor. The brake rotor will be modeled using 1/8th symmetry. This has two effects: 1. A smaller model that results in faster solve times. 2. Easy application of boundary conditions on the symmetry planes. A temperature differential will be applied to the cast iron brake rotor to simulate the thermal loads that act on the model in its operating environment. We'll examine the safety factor, heat flux, and stresses acting on the model as a result of these thermal loads.

2 Open the Model Open the geometry and save a copy. Open the Brake Rotor Model In the Samples section of your Data Panel, browse to: Basic Training 11 - Simulation BrakeRotor 1. Click the Show Data Panel icon ( ) at the top of the screen, if the Data Panel is not currently shown. The Data Panel appears at the left side of the program window. 2. The top level (home view) of the Data Panel is divided into two subsections - PROJECTS and SAMPLES. Scroll to the bottom of the PROJECTS list if necessary to see the SAMPLES list. 3. Locate the Basic Training entry under SAMPLES and double-click it. The Data Panel now displays a list of the folders containing the training lesson models. 4. Click the 11 - Simulation folder. 5. Select the BrakeRotor model. Save the Model When opening a sample model for the first time the active workspace in Fusion is the Modeling Workspace. The model is in Read only and needs to be saved to a personal project. 1. Click File Save As. 2. Optionally, create a Project to store your training models. a. Click New Project b. Specify the project name c. Press Enter. 3. Optionally, create a folder within the project to store your training models. a. Click New Folder b. Specify a folder name c. Press Enter. d. Double-click the new folder to make it the current file saving location. 4. Click Save.

3 Create Study Create a Thermal Stress study Access the Simulation Workspace 1. Click the workspace selection in the top left corner. 2. Select the SIMULATION workspace from the drop-down list. Note: Notice that the New Study dialog is opened automatically. 3. Select the Thermal Stress study type. 4. Click OK. Choose the Units for the Simulation You may have set different default units than are initially defined when Fusion 360 is installed. Also, the simulation units are independent from the units specified in the MODEL workspace. So, the units system can change when you switch to the SIMULATION workspace. Therefore, verify that the proper units are specified to be consistent with this tutorial. 1. Click the Edit button next to the Units node in the browser. 2. Select U.S. (in.) as the unit system and click OK. Note: This exercise will use a cast iron material for the break rotor.

4 Apply Materials The brake rotor is made of cast iron. Cast iron is commonly used for brake rotors due to the thermal characteristics of the material. We'll use the Iron, Gray Cast ASTM A48 Grade 20 from the material library. 1. Click MATERIAL > Study Materials. 2. Select Iron, Gray Cast ASTM A48 Grade 20 as the study material. 3. Click OK. Selecting the Yield Strength as the safety factor criteria allows us to easily determine if the rotor will yield. If the safety factor falls below 1.0, the yield strength will have been exceeded and the part will begin to deform.

5 Apply Constraints The 1/8th symmetry model allows for easy boundary conditions. The x-symmetry plane is constrained in the x-direction, the y-symmetry plane is constrained in the y-direction, and the z- symmetry plane is constrained in the z-direction. Applying the constraints on the symmetry planes fully constrains the free-body movement of the model. 1. Click CONSTRAINT > Structural Constraint. 2. Make sure they Type is set to Fixed. 3. Select the two faces on the YZ plane of the brake rotor as shown below. 4. Activate Ux. 5. Click OK. 6. Repeat these steps, constraining the Uy direction for the two faces on the XZ plane and the Uz direction for the 8 faces on the XY plane.

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7 Apply Loads The brake rotor is loaded by applying two different temperatures to the geometry. The inner surface of the brake rotor has an applied temperature of 100 F. The opposite end of the brake rotor has an applied temperature of 400 F. 1. Click LOAD > Thermal Load. 2. Select the interior surface of the brake rotor as shown below. 3. Make sure Type is set to Applied Temperature. 4. Specify a temperature of 100 F. 5. Repeat these steps for the opposite end of the break rotor as shown below, applying a temperature of 400 F.

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9 Adjust Mesh Settings and Solve In the next steps, we'll adjust the default mesh size and solve the Thermal Stress study. 1. Click MANAGE > Settings. 2. Switch to the Mesh panel. 3. Drag the slider on the mesh size to the left as shown to reduce the size of the mesh. 4. Click OK. 5. Click SOLVE > Solve. 6. Choose between solve On Cloud or Locally and click Solve.

10 Review Results After the simulation is complete, we can review the results of the Thermal Stress study. In particular, we'll examine the safety factor, the heat flux, and the stress concentrations around the notches in the brake rotor. 1. With Safety Factor selected as the result, click INSPECT > Show Min/Max. 2. Notice that the safety factor is just larger than 1.0, indicating the rotor will not yield as a result of the applied temperature loads. Also notice that the regions of the model with the lowest safety factor are located near the edges of the notches. To get a better understanding of why the safety factor is lowest around the edges of the notches we'll take a look at the heat flux and the stress. 1. Click INSPECT > Hide Min/Max. 2. Switch to the Heat Flux result.

11 Notice how the largest heat flux is located around the notches. This makes perfect sense considering the notches in the brake rotor are designed to dissipate heat. 3. Switch to the Stress result. As we might expect, the largest stresses are located on the edges of the notch, due to the high heat flux in this region.