Transcript Chapter 1 Introduction and AutoCAD Fundamentals

Chapter 17
Design Analysis using Inventor Stress
Analysis Module
Objectives:
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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
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In this chapter we will explore basic design analysis using
Inventor Stress Analysis Module. The stress analysis module is a
special module available for part, sheet metal, and assembly
documents. The Stress Analysis Module has commands unique to
its purpose. With Autodesk Inventor 2013, Contact Analysis,
Frame Analysis and Dynamic Analysis can also be performed.
Inventor Stress Analysis Module provides a tool for basic stress
analysis, allowing the user to examine the effects of applied
forces on a design. Displacements, strains, and stresses in a part
are calculated based on material properties, fixtures, and applied
loads. Stress results can be compared to material properties, such
as yield strength, to perform failure analysis. The results can also
be used to identify critical areas, calculate safety factors at
various regions, and simulate deformation. Inventor Stress
Analysis Module provides an easy-to-use method within the
Autodesk Inventor’s Stress Analysis Module to perform an initial
stress 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 using
linear static analysis based on the finite element method.
Linear static analysis is appropriate if deflections are small and
vary only slowly. Linear static analysis omits time as a variable. It
also excludes plastic action and deflections that change the way
loads 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 problems
in engineering mechanics. Analysis using the method is called
finite element analysis (FEA)
STRESS
Linear
Elastic
region
Yield
Point
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Elastic
Plastic
STRAIN
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Finite Element Analysis
In the finite element method, a complex system is modeled as an
equivalent system of smaller bodies of simple shape, or elements, which
are interconnected at common points called nodes. This process is
called discretization, an example is shown in the figures below. The
mathematic equations for the system are formulated first for each finite
element; and the resulting system of equations is solved simultaneously
to obtain an approximate solution for the entire system. In general, a
better 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 in
the 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
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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
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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, and
stresses.
4. Post-processing of the results:
a. Viewing the stress contours and the displaced shape.
b. checking any discrepancy between the preliminary analysis results
and the FEA results.
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Create the CAD model
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Assign the Material Properties
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Start the Stress Analysis Module
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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 Mesh – Local Element Size
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Comparison of Results
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