515 - an introduction to fea via solid edge and...

Unrestricted © Siemens AG 2013 All rights reserved.

4th Generation VLC courtesy of Edison2

#SEU13

515 - An Introduction to FEA via Solid Edge and FEMAP Mark Sherman, Director or Femap Development, Siemens PLM Software


Siemens PLM Software

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



About: Mark Sherman

Mark Sherman

Director or Femap Development




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.



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.



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)

?



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



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



Small Example



Small Example

K u = P (static analysis)

u = K-1 P



Small Example in FEMAP



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



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




• 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




• What can you expect to learn from a

linear static Finite Element Analysis

• Displacements

• Load Paths

• Stress*



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



Live Example – Simple Truss

Example – Truss Model



Beam Model

• Initial Sizing

• General Idea of Deflection

and even Stress Level

• Model Checkout – Run

Modes!

• Symmetry in Mode Shapes

Example – Truss Model



Beyond the Beam Model

• Crippling

• Nonlinear Failure

• Beam Models will

show column

buckling

• Shell Models can

detect flange

instabilties

Example – Shell Model



Example – Solid Model



Details – Glued Connection



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



Detailed Sub-Model

Extract Sub-Model

Apply Free Edge

Displacements (or loads)

Refine mesh in area of

interest

Better results



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



Stresses from the Web




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




Keeping Model Size “Reasonable”

Increase the Mesh Density where you need it, decrease it where

you don’t



Guidelines for Good Stress Interpretation -

Singularities



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



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



Advanced Dynamics Examples

Live Demo – Use the finite element model to adjust the

design to avoid



FEMAP Symposium

• FEMAP Symposium Preview

• Overview of what our FEMAP Partners do

with the software

• Provide idea



SDC Verifier - Wouter van den Bos

www.sdcverifier.com 34

The goal of SDC Verifier is checking structures according

to standards and report generation.



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



Fatigue Essentials/Stress-Life Made Easy with Femap

- George Laird, Predictive Engineering Inc

• Fatigue Analysis



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



SAToolkit suite

Random vibration processor

Sine vibration processor

Element force processor

Energy processor

Modal processor

Stress processor

Grid point force processor

Mass processor



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



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



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



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



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



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



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



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



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.

515 - an introduction to fea via solid edge and...

Documents