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Chapter 17

Design Analysis using Inventor Stress

Analysis ModuleObjectives:

Create Simulation Study

Apply Fixtures and Loads

Perform Basic Stress Analysis

View Results

Assess Accuracy of Results

Output the Associated Simulation Video

File

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Design analysis

In this chapter we will explore basic design analysis usingInventor Stress Analysis Module. The stress analysis module is aspecial module available for part, sheet metal, and assemblydocuments. The Stress Analysis Modulehas commands unique toits purpose. With Autodesk Inventor 2013, Contact Analysis,

Frame AnalysisandDynamic Analysis can also be performed.

Inventor Stress Analysis Moduleprovides a tool for basic stressanalysis, allowing the user to examine the effects of appliedforces on a design. Displacements, strains, and stresses in a partare calculated based on material properties, fixtures, and appliedloads. Stress results can be compared to material properties, suchas yield strength, to perform failure analysis. The results can also

be used to identify critical areas, calculate safety factors atvarious regions, and simulate deformation.Inventor Stress

Analysis Moduleprovides an easy-to-use method within theAutodesk Inventors Stress Analysis Moduleto perform an initialstress analysis. The results can be used to improve the design.

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Linear static analysis

In Inventor Stress Analysis Module, stresses are calculated usinglinear static analysisbased on the finite element method.Linear static analysisis appropriate if deflections are small andvary only slowly. Linear static analysisomits time as a variable. Italso excludes plastic action and deflections that change the wayloads are applied. The finite element method (FEM)is a numerical

method for finding approximate solutions to complex systems.The technique is widely used for the solution of complex problemsin engineering mechanics. Analysis using the method is called

finite element analysis (FEA)

Elastic Plastic STRAIN

STRESS

Linear

Elastic

region Yield

Point

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Finite Element Analysis

In the finite element method, a complex system is modeled as anequivalent system of smaller bodies of simple shape, or elements, whichare interconnected at common points called nodes. This process iscalled discretization,an example is shown in the figures below. Themathematic equations for the system are formulated first for each finiteelement; and the resulting system of equations is solved simultaneouslyto obtain an approximate solution for the entire system. In general, abetter approximation is obtained by increasing the number of elements,which will require more computing time and resources.

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Problem Statement

Determine the maximum normal stress that loading produces inthe aluminum plate.

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Preliminary Analysis

The nominal normal stress developed at the smallest cross section

(through the center of the hole) in the plate is

Geometric factor = .75/2 = 0.375

Stress concentration factor K is obtained from the graph, K = 2.27

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Finite Element Analysis Procedure

1. Preliminary Analysis.2. Preparation of the finite element model:

a. Model the problem into finite elements.

b. Prescribe the geometric and material information of the system.

c. Prescribe how the system is supported.

d. Prescribe how the loads are applied to the system.

3.Perform calculations:

a. Generate a stiffness matrix of each element

b. Assemble the individual stiffness matrices to obtain the overall, or

global, stiffness matrix.

c. Solve the global equations and compute displacements, strains, andstresses.

4. Post-processing of the results:

a. Viewing the stress contours and the displaced shape.

b. checking any discrepancy between the preliminary analysis resultsand the FEA results.

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Create the CAD model

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Assign the Material Properties

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Start theStress AnalysisModule

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Apply Constraints

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Applying Load

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Create a Mesh and Run the Solver

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View the FEA Results

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Refinement of the FEA Mesh Global Element Size

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Refinement of the FEA MeshLocal Element Size

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Comparison of Results