515 - an introduction to fea via solid edge and...
TRANSCRIPT
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515 - An Introduction to FEA via Solid Edge and FEMAP Mark Sherman, Director or Femap Development, Siemens PLM Software
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4th Generation VLC
courtesy of Edison2
Agenda: 515 - An Introduction to FEA via Solid Edge
and FEMAP
Who am I?
What you will learn
Solid Edge capabilities
Demonstrations
Benefits of this topic
How to learn more
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About: Mark Sherman
Mark Sherman
Director or Femap Development
Siemens PLM Software
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What you will learn
This session will cover the basics of Finite Element Analysis with an emphasis on
how to use FEA tools to effectively influence the design process and increase
product quality and performance. Proper application of the tools provided in both
Solid Edge and FEMAP will be discussed. This session should be useful to
designers and engineers who want to more fully understand the structural,
dynamic and thermal performance of individual parts and complex systems.
Fundamental concepts of FEA will be discussed, as well as advanced topics and
advanced analysis disciplines, including highlights from the next day's FEMAP
Symposium.
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A Brief History of FEA and FEM
The concept of a “Finite Element” was introduced by Prof. R.W. Clough of UC Berkeley in
1960 at an ASCE Conference.
NASTRAN (NASA STRuctural ANalysis) was developed for NASA by a consortium of
several companies for the analysis of the Saturn V rocket.
Siemens PLM Software acquired MSC.Nastran source code in 2003 and has
greatly improved the performance and capabilities of
NX Nastran through the latest release of NX Nastran 8.1
Finite Element Modelers(Pre/Post Processors), the tools used to generate Finite
Element meshes and view results, were first commercialized in the 1970s.
Siemens PLM Software began the first commercial offering of FEM software with
the introduction of SDRC SuperTab in the 1970’s.
Siemens continues to support the analysis community with Femap and NX CAE
pre/post-processors.
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The Solution
Consider a single degree of freedom system – a simple spring:
Apply the following conditions to generate a system of simultaneous equations where
displacements are the unknowns:
Equilibrium of forces and moments
Strain- displacement relations
Stress-strain relations
K: spring stiffness P: applied load
u: displacement
K u = P (static analysis)
?
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Solution for Multiple DOFs
Any real structure can be modeled as a collection of elements connected at
nodes
With many elements and nodal dof’s, a matrix approach to the solution is
adopted
All element matrices are assembled into a global stiffness matrix
Kgg =
k11 k12
k21 k22 ka =
Element stiffness matrix ka kb
1 2 3
ka11 ka12
ka21 ka22 + kb22 kb23
kb32 kb33
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Modeling of Real Structures
• The behavior of the real structure is obtained by considering the collective behavior of the discrete elements.
• The user is responsible for the subdivision or discretization of real-world structures.
• Element choice has significant influence on the behavior • A graphic preprocessor such as FEMAP/SE Simulation is the key tool for
generating a model that accurately simulates real world structures
Kgg =
ka -ka
-ka ka + kb -kb
-kb kb
• Contributions from all other elements
n x n
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Small Example
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Small Example
K u = P (static analysis)
u = K-1 P
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Small Example in FEMAP
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FEA in Solid Edge and FEMAP
Solid Edge Simulation FEMAP w/NX Nastran
Linear Static
Normal Modes
Buckling
Steady State Heat
Transfer
Nonlinear *Geometric NL in ST6
Advanced Nonlinear
Superelement
Aeroelasticity
Advanced Dynamics
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Linear Static Analysis
Solid Edge FEMAP
• Isotropic Materials
• Tri/Quad Shell Elements
• Beam Elements
• Tetrahedral Solid
Elements
• Loads – Forces,
Pressures
• Constraints
• Isotropic Materials
• Tri/Quad Shell Elements
• Beam Elements
• Tetrahedral Solid
Elements
• More Element Types
• Composite Laminates
• Equation Based Loads
• Data Surface Loads
• Additional Load Types
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Linear Static Analysis
• 90%+ of all FEA projects
• 100% Linear – if you double the loads,
you get double the response
• Material stays in the elastic range –
return to original shape
• Small Deformation
Maximum Displacement much smaller
than characteristic dimensions of the
part being studied, i.e. displacement
much less than the thickness of the
part
• Loads are applied slow and
gradually, i.e. not Dynamic or Shock
Loading
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Linear Static Analysis
• What can you expect to learn from a
linear static Finite Element Analysis
• Displacements
• Load Paths
• Stress*
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Linear Analysis is small displacement, small angle theory
Must use nonlinear analysis if the displacement changes the stiffness or loads
Pressure loads on flat surfaces, have no membrane component unless nonlinear
large displacement solution performed.(load carried by bending stiffness only)
Linear contact is a misnomer, contact condition is iterative solution, but no other
nonlinear effects are considered.
Mesh density required is a function of the desired answers
Must have enough nodes so model can deform smoothly like the real structure.
In general, accurate stresses require more elements than accurate displacements.
Goal is for a small stress gradient across any individual element
Normal modes should always be run before any dynamic solution
Confirm model behavior, stiffness and mass properties are correct
Important Guidelines
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Live Example – Simple Truss
Example – Truss Model
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Beam Model
• Initial Sizing
• General Idea of Deflection
and even Stress Level
• Model Checkout – Run
Modes!
• Symmetry in Mode Shapes
Example – Truss Model
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Beyond the Beam Model
• Crippling
• Nonlinear Failure
• Beam Models will
show column
buckling
• Shell Models can
detect flange
instabilties
Example – Shell Model
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Example – Solid Model
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Details – Glued Connection
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Detailed Local Model
Free Body Interface Load
Check Strength of Weld
288.56 #/inch weld shear
163.96 #/inch weld tension
================================================================================================================
** TOTAL SUMMATION **: 5.90822887, -563.430786, 320.078766, 188.497498, -4.823166E-5, 6.9473767
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Detailed Sub-Model
Extract Sub-Model
Apply Free Edge
Displacements (or loads)
Refine mesh in area of
interest
Better results
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Linear Statics - Stresses
To accurately recover stresses in shell and solid elements, the
mesh must be very dense in areas of high stress gradients
Stress Changing Too
Fast Across One Element
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Stresses from the Web
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Linear Statics - Stresses
To accurately recover stresses in shell and solid elements, the
mesh must be very dense in areas of high stress gradients
Stress Changing Less Across
an Element – More Accurate
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Linear Statics - Stresses
Keeping Model Size “Reasonable”
Increase the Mesh Density where you need it, decrease it where
you don’t
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Linear Statics - Stresses
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Guidelines for Good Stress Interpretation -
Singularities
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Guidelines for Linear Static Analysis - Stresses
• Remember the limitations of “Linear” analysis
• Increase Mesh Density in High Stress Regions
• Ignore Stress Answers at Singularities
• Zero Radius Fillets
• Inside Corners
• Loaded and Constrained Nodes
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Advanced Dynamics Examples
Frequency response analysis is used to compute structural response to steady-state oscillatory
excitation. Examples of oscillatory excitation include rotating machinery, unbalanced tires,
and helicopter blades. In frequency response analysis the excitation is explicitly defined in
the frequency domain. Excitations can be in the form of applied forces and enforced motions
(displacements, velocities, or accelerations).
Request responses
between 50 and 80 Hz,
every 0.05 Hz
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Advanced Dynamics Examples
Live Demo – Use the finite element model to adjust the
design to avoid
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FEMAP Symposium
• FEMAP Symposium Preview
• Overview of what our FEMAP Partners do
with the software
• Provide idea
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SDC Verifier - Wouter van den Bos
www.sdcverifier.com 34
The goal of SDC Verifier is checking structures according
to standards and report generation.
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Report Generation in Designer
www.sdcverifier.com 35
Export To Word Print and Preview without Word
Extra Items
Regenerate
part of report
Edit Item
Properties
Move items
(Drag and
Drop)
Edit properties
with context
menu easily
Toolbox with all project items
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Fatigue Essentials/Stress-Life Made Easy with Femap
- George Laird, Predictive Engineering Inc
• Fatigue Analysis
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Frederic Boilard, MAYA and Eric Preissner, PEC
Using Femap for Large Space System Analysis
SAToolkit for Femap
Random and Sine solutions from Nx NASTRAN normal modes results
Efficient post-processing of Nx Nastran results
Ranking, sorting, enveloping, filtering
Summaries by groups, subcases, etc.
Margins of safety for different failure types
Direct manipulation of .op2 file data
Extremely efficient for large models
Automatic Femap compatible graphical results
Automatic report generation
HTML, MS Excel®, ASCII
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SAToolkit suite
Random vibration processor
Sine vibration processor
Element force processor
Energy processor
Modal processor
Stress processor
Grid point force processor
Mass processor
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Femap / Excel® API
Allow to link Excel® and Femap
Permits to drive Femap changes from Excel®
Material import / export MAT1, MAT2 and MAT8
Property import / export CBAR, CBEAM, CBUSH, PSHELL, PSOLID and CONM2
Create groups from nodes and element ranges
Extract mass per properties or group for easy
mass tuning
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Simulating Drop Loads Impact on a Structure
with Femap and NX Nastran - John LeCour,
Saratech
• Proper use of Rigid elements
to model masses
• How to define impact
conditions
• Assessing different solutions
for impact assessments
• Setting up a Transient
Solution for impact loads
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Tips for Debugging Finite Element Models in
Femap and Nastran - David Weinberg, NEi
Software
Diagnose Common Problems
when models don’t run
Singularities
Disconnected Elements
Mixed Mesh Shell/
Solid Mesh Issues
Quad Element
In-Plane Rotations
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Nonlinear Analysis Using Femap with NX Nastran
- Chip Fricke, Principal Application Engineer
Overview of Nonlinear Analysis
Comparison of the NX Nastran Nonlinear and NX Nastran Advanced Nonlinear
Solvers
Nonlinear Material Models
Example – Large Deformation using both NX Nastran Nonlinear and Advanced
Nonlinear
NX Nastran Basic Nonlinear Analysis
NX Nastran Advanced Nonlinear Analysis
Femap Examples and NX Nastran Technical References
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What Defines Nonlinear Analysis
Material Nonlinearity
Transient (time-dependent) loading
Large displacement
Contact due to
• Closure or opening of large gaps
• Rigid contact bodies
• “Double-sided” contact
• Edge to Edge contact
• Collision or impact
• Load Direction Changes with Deflection
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Advanced Postprocessing Using the Femap API
- Patrick Kriengsiri, Senior Software Engineer
How Output is Stored in the FEMAP Database
Attached Results vs. Internalized Results
Controlling Output Display with the FEMAP View Object
Output Set and Output Vector Objects
FEMAP Results Browsing Object
Output Processing
Creating User Output
Importing Custom Output Data
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Existing FEMAP APIs
Andy Haines - Applications Engineer - FEMAP
An rundown of existing FEMAP API scripts including:
• Stress Linearization Tool
• Calculate and Thicken Tool for shell elements for variable thickness
geometry
• Hide/Show Entities Tool for easy manipulation of viewable entities
• Auto Bolt-maker Tool for creating “spider and beam” bolts
• CBUSH Reference Coordinate System visualization
• Other useful tools currently available
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FEMAP Tips and Tricks
Andy Haines - Applications Engineer - FEMAP
A chance to learn about “lesser known” functionality already available in the
FEMAP product in the following areas:
• User Interface
• Geometry
• Modeling
• Visualization
• Analysis
• Post-Processing
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Dynamic Response Analysis with External
Superelements - Joe Brackin, Senior Software
Engineer
One efficient technique for performing system level dynamic
analysis is to use Craig-Bampton style external superelements for
some components. Femap now supports the creation and use of
external superelements. By adding the Craig-Bampton modal
information to the standard external superelement, we can very
efficiently increase the accuracy of the dynamic behavior of the
component. We will demonstrate the creation and use of Craig-
Bampton style external superelements in a system level normal
modes analysis in Femap.
This example will demonstrate the use of external superelements to
perform a normal modes solution of a rocket system composed of 3
components.
Example steps:
1) Solve for the normal modes of the rocket system without
superelements.
2) Create an external superelement representing each booster.
3) Create a normal modes solution for the center tank and attach the
booster external SE.
4) Create a new booster external SE with Craig-Bampton modes
added.
5) Perform a second rocket system normal modes solution using the
Craig-Bampton booster to demonstrate the increased accuracy.