Transcript Accuracy of Fully Elastic vs Elastic Plastic Draf+

Accuracy of Fully Elastic vs. Elastic-Plastic Finite Element Analysis
Masters of Engineering
Rensselear Polytechnic Institute
By
Nicholas Szwaja
June 11, 2012
Introduction
• Purpose: Analyze the accuracy of Finite Element
Analysis (FEA) when it is used to compare fully
elastic and elastic-plastic deformation in high
strength steel
• Investigate elastic plastic reverse loading in FEA
• Method: Use FEA to model a tensile test using a
standard specimen.
– Apply tensile load using fully elastic and elastic-plastic
material properties
– Apply tensile load to yield the HSS test specimen and
then apply compressive load to analyze stress and
strains
Fully Elastic Results
Deflection is
0.00836 inches
Hand Calculations:
•Von Mises Stress = 54,019 psi
•Deflection = 0.00916 in
Elastic Plastic Results
Data Point HSS Tensile Test
Results
Discussion
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Fully Elastic Model Stress Strain Curve Is Linear Regardless Of Force
Applied
Fully Elastic FEA Model Shows No Signs Of Decreasing Cross Sectional
Area Or Necking
Fully Elastic FEA Model Within 2.3 % Of Hand Calculation Values
Elastic Plastic FEA Follows Data Point Lab Results To 100% accuracy
Elastic Plastic FEA Model Shows Decrease In Cross Sectional Area And
Starts To Neck
No Method Of Determining Fracture Point, Cross Sectional Area Continues
To Decrease
Reverse Loading In FEA ABAQUS Uses The Elastic Plastic Material
Properties That Do Not Have Negative Strain Or Stress Values
Reverse Loading Acts Linearly During The Compression Phase Of The
Analysis
Deflection And Stress Is Equivalent For The Tensile And Compressive
Loading. Not Accurate Based On Actual Test Data. For Accurate Results
Material Plastic Stress And Plastic Strain Need To Be Manually Uploaded
Into the Material Selection
Conclusion
• FEA ABAQUS is an approximation tool and is only as
accurate as the material properties provided
• Fully Elastic and Elastic Plastic FEA Analysis react
differently and knowledge of the failure modes are
required
• Elastic Plastic analysis requires further material property
details
• FEA and hand calculations provide theoretical solutions
while real world data provides the most accurate
solutions
• Reverse loading requires additional material properties
to develop negative stress and strain values. FEA
ABAQUS will react linearly after the HSS tensile
specimen has plastically deformed