MAE 323: Lab 8 Hertzian Contact

Instructions

© 2011 Alex Grishin MAE 323 Lab Instructions 1

MAE 323: Lab 8

Lab Learning Objectives

Hertzian Contact

• Gain familiarity with geometry creation and simplification

• Learn to validate FE models and qualify FEA results

© 2011 Alex Grishin MAE 323 Lab Instructions 2

MAE 323: Lab 8 Hertzian Contact

• In Lab 8, the entire FEA process is completed, with the focus being on geometry simplification and post-processing

Lab 8 focus

FEA Process

Geometry

Meshing

Loads and Boundary Conditions

Solving

Lab 8 focus Post-processing © 2011 Alex Grishin MAE 323 Lab Instructions 3

MAE 323: Lab 8

Problem Statement

Hertzian Contact

• Two different industrial rollers (next slide) are made of a mineral- filled elastomer.

• They are controlled by a hydraulic slide mechanism which brings them together with a force of 2500 lbf for the purpose of flattening and curing sheet stock of composite material for the electronics industry.

• The elastomer material has a Young’s Modulus of 1.0e5 psi and Poisson’s Ratio of .3.

• You are tasked with determining the maximum contact pressure experienced by the rollers.

• You are to construct an appropriate finite element model and compare your result to an analytical solution.

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MAE 323: Lab 8 Hertzian Contact

Problem Statement: Schematic

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MAE 323: Lab 8

Geometry Creation

Hertzian Contact

• Create the geometry in the ANSYS DM or the CAD software of your choice.

• Use the dimensions on the previous slide – Remember that this is a 2D analysis

• You should have two separate surface bodies, not one

• Take into consideration symmetry, singularities and the effects of the load and how they are applied

• Transfer your geometry to Workbench Mechanical using a Static Structural analysis (remember to change your analysis type to 2D in the geometry properties before attaching the static structural component)

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MAE 323: Lab 8

Adding a material

Hertzian Contact

• Double click on Engineering Data in your Project Page

• Click where it says “Click here to add a new material” and type “Elastomer X”

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MAE 323: Lab 8

Adding a material cont.

Hertzian Contact

• On the left side of the screen under Toolbox, expand Linear Elastic

• Click on Isotropic Elasticity and drag it to your “Elastomer X” material

• Input the Young’s modulus and Poisson’s ratio in the yellow boxes that will appear

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MAE 323: Lab 8

Adding a material cont.

Hertzian Contact

• Make sure your units for your values are correct

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MAE 323: Lab 8

Workbench Mechanical Setup

•Once in Mechanical, make sure each part gets the “Elastomer X” material

•Do this by clicking on each surface body (under “Geometry” in the tree outline). Then select the material in the Details View

Hertzian Contact

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MAE 323: Lab 8

Workbench Mechanical Setup

Hertzian Contact

• Expand the Connections stem in your project outline tree – Expand the Contacts stem

• Ensure that the contact has the correct behavior (e.g. frictionless, frictional, bonded, etc.) and is in the correct region

• Apply the specified force

• Make sure your model is constrained

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MAE 323: Lab 8

Workbench Mechanical Setup

Hertzian Contact

• Under your contact settings, make sure your Interface Treatment is set to ‘Adjust to Touch’

• Under Analysis Settings, make sure Weak Springs is set to ‘Off’

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MAE 323: Lab 8 Hertzian Contact

Mesh Settings 1. Keep relevance 100

2. Keep midside nodes

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MAE 323: Lab 8

Mesh Refinement

Hertzian Contact

• Perform a local mesh refinement (using the sphere of influence, for example) to get a maximum contact pressure that comes within 3 percent of the analytical value. – The analytical value can be calculated using the equations in the Template

• To look at the max. contact pressure: RMC on Solution>Insert>Contact Tool

• Once the contact tool is inserted, RMC>Insert>Pressure and Penetration

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MAE 323: Lab 8

Mesh Refinement

Hertzian Contact

• If you use a sphere of influence, keep in mind that both bodies will require one.

• Please try to remember all the lessons we learned previously about the Workbench mesh sizing controls.

• Record your mesh refinement results in Table 1 of the Template

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MAE 323: Lab 8 Hertzian Contact

To Answer the Lab Template Questions

• To answer the questions, you may want to reproduce your solution in the other 2D formulation for comparison (in the project page, right-click on the top cell (Static Structural) and select “Duplicate”).

RMC

• In the Duplicated model, change the 2D formulation (for example, if the first model was plane stress, change the copied model to plane strain), then re- run to view results.

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MAE 323: Lab 8

For Images and Results

Hertzian Contact

• Be sure that all of your images are taken from the final, converged results. That is, your mesh is refined to within 3% of the analytical value

• To show the contour plots superimposed on the mesh:

– Click on the desired result, for example, normal stress and do the following

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