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Finite Elements Analysis Basics

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Finite Elements Analysis Basics Analysis Foundation In designing the gear shafts below, what quantities would we examine? Stress Strain Displacement Rotation ... – PowerPoint PPT presentation

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Title: Finite Elements Analysis Basics

1
Finite Elements Analysis Basics
2
Analysis Foundation
• In designing the gear shafts below, what
quantities would we examine?
• Stress
• Strain
• Displacement
• Rotation
• Temperatures

3
Analysis Foundation
• In designing a valve, burner, or heat sink, what
quantities would we examine?
• Pressure drop
• Temperatures
• Mass flow rate
• Velocities
• Fluid mixing

4
Analysis Foundation
• Hand calculations are easily applied to simple
geometries.
• Cylinders
• Blocks
• Beam structures
• They are not easily or accurately applied to
general (complex) shapes.

? To analyze complex shapes we break them into
many simple shapes and compute the combined
response.
5
FEA Analogy Area
• Suppose we want to compute the area of a generic
shape.

6
FEA Analogy Area
• What do we do to improve the accuracy of the area
measurement?

7
FEA Mesh
• The pieces we divide the model into are called
ELEMENTS. Equations are generated for each
element. These are combined into a system of
equations for the entire structure. Matrix
algebra is used to solve the system of equations.

8
FEA Mesh Elements
• Each element is a simple solid.
• Elements are connected together at locations
called NODES.

9
FEA Mesh Elements
• A BRICK element model often must be created
MANUALLY.
• A TETRA element can be created AUTOMATICALLY.

10
Brick Elements vs. Tetra Elements
• Brick Models
• Usually have many fewer elements than a Tetra
model (Quicker Solution).
• - Time-consuming to generate.
• - Very difficult to create a brick model for
complex parts.
• Tetra Models
• Quick to generate the model (with Automatic
meshing).
• The same accuracy can be achieved as with
Bricks.
• Can mesh very complex parts.
• - Usually have more elements than a Brick model.

11
Brick Elements vs. Tetra Elements
12
Brick Elements vs. Tetra Elements
13
Analysis Accuracy
• Fewer elements will solve more quickly.
• More elements will be more accurate.
• You need to strike a balance between model size
and run time.

14
Accuracy vs Mesh Size
15
Accuracy vs Mesh Size
16
Mesh Transition
• Many times different locations in the model do
not require the same accuracy.
• Use mesh control and transition capabilities to
focus the computational effort in the areas where
the most accuracy is required.

17
Design Analysis Steps
• Geometry definition.
• Define component materials.
• Define physical situation with boundary
conditions.
• Mesh the model.
• Run the analysis (solve the system of equations).
• View and evaluate the results.