become an fea expert, solidworks simulation
DESCRIPTION
Some steps on how to become an FEA expert. The presentation was given at a SolidWorks Users Group summit at Penn State University, so the background examples are general in nature but with some focus on SolidWorks SImulation software.TRANSCRIPT
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SolidWorks Simulation:
Go from Novice to Expert
in 32 Easy Slides
Joe Galliera
DS SolidWorks Corp.
Senior SIM Tech Mgr, EAST
September 25, 2013
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Question of Accuracy
“Structural Engineering is the Art of moulding materials we do not wholly understand into shapes we cannot precisely analyse, so as to withstand forces we cannot really assess, in such a way that the community at large has no reason to suspect the extent of our ignorance.”
― Dr. A. R. Dykes, in the May 1978 issue of the
Institution of Structural Engineer’s official journal,
The Structural Engineer
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Where you are now? Novice? Expert?
Everything you think you know is…
Wrong
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Only Difference between a Novice & Expert
The Expert knows…
What Questions to Ask.
And how to go about
answering them.
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In the simplest terms, FEA answers
complex questions about structural
behavior...
Based on a Given Set of
Assumptions!
What is FEA?
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10 in. 2 in.
1 in.
1000 lbs. Y
X
(0,0,0) Z
Y
(0,0,0)
Problem Inputs: • Geometry:
•Thickness
•Length
•Width
• Load
• End Restraint
• Material Properties
Problem Statement
What are the Assumptions?
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10 in. 2 in.
1 in.
1000 lbs. Y
X
(0,0,0) Z
Y
(0,0,0)
Problem Inputs: • Geometry:
•Thickness
•Length
•Width
• Load
• End Restraint
• Material Properties
What are the Assumptions?
X Manufacturing Tolerances
Magnitude & Direction
Unobtainium?
Actual material values from supplier
Small Displacement
Linear Elastic Stress-Strain
Gravity?
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10 in. 2 in.
1 in.
1000 lbs. Y
X
(0,0,0) Z
Y
(0,0,0)
Problem Statement
What are the Assumptions?
Every Input is an Assumption!
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Dilbert Knows
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What Does This All
Mean?
All FEA Solutions are
wrong…
Usually the Answers are right
but the Questions are wrong!
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The Assumption Set That Defines the Problem…
• Geometry
• Properties
• Material
• Element
• Interactions (Boundary Conditions)
• Mathematical Representation (Mesh)
• Idealization
• Convergence …Controls the Accuracy!
What is a “Question” in FEA Terms?
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Steps to running an analysis 1. Objective?
2. Expected Answer?
3. Simplify Geometry
4. Materials
5. Restraints & Loads
6. Mesh
7. Solve
8. Interpret Results
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Boundary Conditions… Loads & Constraints
…Represent the Interactions of the Parts You
Didn’t Model with the Parts You Did!
Your Boundary Conditions MUST NOT Impose
Displacements, Stresses, Rigidity, or Other
Behavior That the Parts You Didn’t Model
Wouldn’t Have Imposed.
What are Boundary Conditions?
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Problems Simulating Real Life Conditions…
1. Tension Spring Failure
2. Offset Shaft Bearing Model
3. Torqued Frame
4. Railcar Floor Casting
5. Backboard Linkage
6. Wheelbarrow Handle
7. Ball Valve CFD
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Tension Spring Failure
Field Failure
Test & FEA Failure
Insufficient Knowledge of the System
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Tension Spring Failure
Threaded Rod
Insufficient Knowledge of the System
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Offset Shaft Bearing Model Overly Constrained
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Fixed Bearing – 32 ksi
Pinned Bearing – 98 ksi
Offset Shaft Bearing Model Overly Constrained
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Torqued Frame Improper Interpretation of Interaction
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Enforced Displacement - Surface
Enforced Displacement – Pinned Tube
Torqued Frame Improper Interpretation of Interaction
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Enforced Displacement - Surface
Enforced Displacement – Pinned Tube
Torqued Frame Improper Interpretation of Interaction
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Fully Constrained
At Attachment Interfaces?
Railcar Floor Casting Under-modeled System
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1
2
34
56
7
1
2
34
56
7
1.45 R.
24.0
8.00
2.35
1.125 1.80
1,200 lbs.
G1
UL UL
G2
LL N
N P P
LL
X Y +
Basketball Backboard Link Incorrectly Calculated or Estimated Loads
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-25,000.00
-20,000.00
-15,000.00
-10,000.00
-5,000.00
0.00
5,000.00
10,000.00
15,000.00
20,000.00
25,000.00
30,000.00
1 2 3 4 5 6 7
Ratchet Position
Rea
ctio
n (L
bs)
G1_X
G1_Y
G1_Mag
G2_X
G2_Y
G2_Mag
UL_X
UL_Y
UL_Mag
LL_X
LL_Y
LL_Mag
P_X
P_Y
P_Mag
N_X
N_Y
N_Mag
Basketball Backboard Link Incorrectly Calculated or Estimated Loads
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X
Z
Y
Should Z Rotations be released
On Grip Portion of Handle?
Wheelbarrow Handle Incorrect Restraints
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Rotations Freed on Grip
Max. Disp.
0.070 in.
VMS Exceeding
20,000 psi.
Ty=0
Rz=0
Wheelbarrow Handle Incorrect Restraints
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Grip “Pinned”
Max. Disp.
0.315 in.
VMS Exceeding
20,000 psi.
Pinned Connection
Only Ty=0
Wheelbarrow Handle Incorrect Restraints
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Ball Valve CFD Failure to Mimic Physical Test Conditions
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Ball Valve CFD Failure to Mimic Physical Test Conditions
Upstream Static
Pressure Gauge
Downstream
Static Pressure
Gauge
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Tips for Improved Simulations 1. Anticipate Behavior – Use Common Sense
2. Build Free Body Diagrams
3. Identify Stiffness Differentials
4. Determine Model Sensitivity
5. Utilize Hand Calculations
6. Beware of Over-Constraining
7. Watch out for Rigid Body Motion
8. Utilize Force Summations
9. Review Historical Data
10. Utilize Outside/Inside Support for Sanity Check
11. Build Test Models
12. Correlate to Appropriate Constructed Tests
13. Generate Reports / Document Sources
14. Build up Models Slowly – Use Simplified Techniques First
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In Summary…
1. Understands the Physics Involved
2. Can Manage Assumptions
3. Knows How to Use Software Tools
4. Properly Interprets Results
An Expert:
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Questions?