Femap Basic - Day 2

Femap Training

Basic Course

© UGS Corp. 2006. All rights reserved.Femap with NX Nastran 1-2

Femap with Nastran - Basic

Day 2 Agenda

Building Geometry in Femap, Import and Modifications

• Exercise 6 - Creating Solid Meshing

• Exercise 7 - Tetrahedral vs. Hexahedral Meshing

Midsurfacing of Geometry

• Exercise 8 - Midsurface Modeling

• Exercise 9 - Interactive Midsurface Meshing

Definitions of Loads and Constraints

• Exercise 10 - Bearing Load

FE Assembly Connections

• Exercise 11 - Solid Assembly with Linear Contact

Analysis Set Manager and Nastran Solution Sequences

Visualizing and Documenting Results

• Exercise 12a,b - PostProcessing with Deformed Contour and XY Plots


Femap Basic Importing and Meshing Geometry


Direct CAD Interfaces

Solid Edge (.par, .psm, .pwd, .asm)

NX Unigraphics (.prt)

NX I-deas (.idi)

Pro/Engineer (.prt, .asm)

Catia v4 (.mdl, .exp, .dlv)

Catia v5 (.catP*) – optional

SolidWorks (.sldprt, .sldasm)

Standard CAD Interfaces

Parasolid

ACIS

STEP (AP 203 Solid Entities, AP 214 Surfaces)

IGES

DXF

STL – reads .stl files as triangular surface mesh

Geometry Import Formats


Sheet Solids vs. Solids

General considerations

Any parasolid entity that has area and no volume (i.e. a surface,

or stitched body of surfaces) is called Sheet Solid.

Any parasolid entity that has area AND volume is Solid

Verify volume with the Tools, Mass Properties, Solid Properties

command.

Sometimes this can cause confusion when stitching, and there is

an unknown sliver. The part looks like a solid and lists out as a

solid, but when you look at the messages window it will say

"Sheet Solid 1 Created, Solid 1 Passes Body Checking"


Troublesome Geometry

The challenge of meshing a part will usually arise from a

combination of two factors

The modeling approach of the part

The geometry translation interface that was used to bring the

geometry into Femap

You usually don't know if you have a problem with your

geometry until you try to mesh it

The Messages window is valuable for troubleshooting the

areas of your geometry the mesher is having trouble with


Troublesome Geometry

Geometry, Solid, Cleanup command

Is used to "cleanup” a solid

This command will check the solid

and remove any extraneous features

which are not part of the actual solid

Geometry, Solid, Explode/Stitch

commands

Sometimes, problems with small

slivers, or edges that don't quite meet

each other can be solved by

exploding the solid, and re-stitching it

with a tolerance wider than the

slivers.


The solid meshing process of

Femap is done internally

First involves meshing of

surfaces of the solid with plot-

only plate elements

The plate mesh is evaluated,

and if it is a valid surface mesh,

Femap then creates tetrahedral

elements moving from the

outside mesh inward.

The Messages window

documents each step of the

meshing process.

The Process of Solid Meshing


Feedback from Messages Window

The error message:

“Boundary Intersection. No edges of the boundary to be

meshed may intersect any other boundary edge” - usually

means that elements are being created on top of each other,

or are protruding into each other

This is usually due to a discontinuity or other error in the

geometry that is being meshed


Boundary Surface from Surfaces

on Solid

Geometry Boundary Surface From Surfaces on Solid

Takes the surfaces you select and uses the enclosing outer curves to

form a regular boundary surface

The surfaces must be stitched into a solid.

This feature works best with surfaces that have small to moderate

curvature.

Can be used to remove sliver surfaces by selecting surfaces that

surround the sliver.


Edge and Feature Supression

Mesh, Mesh, Control Feature Suppression

Example – suppress the hole

in the block when meshed.

© UGS Corp. 2006. All rights reserved.Femap with NX Nastran

Exercise 6

Creating Solid Meshing

1-12


Exercise 7

Tetrahedral vs. Hexahedral Meshing

1-13


Femap BasicMidsurfacing of Geometry


Mid-surfacing commands allows users

to extract midsurfaces in order to

reduce the complexity and increase

accuracy of the FE Model

For the part shown:

Solids: 113,512 nodes and 63,875

elements ( > 3 minutes solve time)

Shells: 1725 nodes and 1576 elements

(< 10 seconds solve time)

Mid-surfacing of Geometry


Geometry, Midsurface Commands

Geometry, Midsurface, Single in Solid

Creates a single trimmed mid-surface between

two surfaces of a solid.

Geometry, Midsurface, Single

Creates a single sheet surface between two

surfaces that extends beyond extent of both

surfaces.

Geometry, Midsurface, Trim to Solid

Trims a surface with a solid and deletes any

part(s) of the surface which lie outside the

volume of the solid.

Geometry, Midsurface, Trim with Curve

Trims or breaks a surface with a curve


Geometry, Midsurface, Extend

Extends a surface by using one of a surface's edge curves using Extend

Shape method



Geometry, Midsurface, Automatic

Automatically generates midplanes, trims them

to solid and cleans up any surfaces that are

determined not to be part of the model

Mid-surfaces are extracted from parallel faces

Automatically creates a group called “Midsurface”



Geometry, Midsurface, Offset Tangent Surfaces

Offset Tangent… for use on solids of constant

thickness only

The offset surfaces will be automatically stitched

together and finally you will be asked if you want to

delete the original solid.

Geometry, Midsurface, Generate, Intersect and

Cleanup

These are the steps in order that the automatic

command follows.

Geometry, Midsurface, Assign Meshing Attributes

Prompt’s you for the material for the selected

surface(s) and then automatically create the

properties referencing the original thickness(es) of

the solid.



New Mid-surfacing approach

Start with the command Geometry – Midsurface, Offset

Tangent Surfaces…

Pick one face on inside or

outside of the sheet metal solid

Femap finds the rest

V10 New Mid-Surfacing Method


New Mid-surfacing approach Enter Offset Distance or

Measure Offset Distance



New Mid-surfacing approach Delete orginal solid and

automesh using Property

Attributes Only



New Mid-surfacing approach Automesh using Meshing

Attributes (Triangles)



New Mid-surfacing approach Automesh using Meshing

Attributes, More Options



New Mid-surfacing approach Automesh using Meshing Attributes and Interactive Meshing



Exercise 8

Midsurface Modeling


Exercise 9

Interactive Midsurface Meshing


Femap BasicLoads and Constraints


Body or Global Loads – applied to the entire model.

Acceleration Translational (gravity) and Rotational

Rotational Velocity and Center of Rotations

Thermal – Default Temperature

Body Loads


Structural Loads

Load Type Points Curves Surfaces Nodes Elements

Force

Force Per Length

Force Per Area

Force Per Node

Moment

Moment Per Length

Moment Per Area

Moment Per Node

Displacement

Enforced Rotation

Velocity

Rotational Velocity

Acceleration

Rotational Acceleration

Distributed Load

Pressure


Thermal Loads


Temperature

Element Temperature

Heat Flux (Heat Energy /Unit Area)

Heat Flux per Length

Heat Flux per Node

Heat Generation (Heat Energy /

Unit Volume)

Element Heat Flux

Convection

Radiation

Element Heat Generation


Fluid Loads


Static Fluid Pressure

Total Fluid Pressure

General Scalar

Steam Quality

Relative Humidity

Fluid Height Condition

Unknown Condition

Slip Wall Condition

Fan Curve

Periodic Condition


Notes on Loads

Nastran Displacement and Enforced Rotation loads require

constraining the loaded object in the direction of the applied load

(NX, MSC.Nastran)

e.g. A Displacement Load of x=.10, and y=.10 applied to a point

requires that the corner be constrained in X and Y

For NX Nastran Advanced Nonlinear (SOL601), loads should be

applied with a time-based function.

For solvers other than NX Nastran, refer to the Femap Users Guide

for details on the loads supported by Femap for the solver used

Also refer to that solver’s documentation on how to apply loads.


Creating Load Sets

Model, Load , Create/Manage Set command creates a new or

activates an existing load set

You may create as many different load cases as necessary


Creating Load

Model, Load command creates a new load

referring to defined Load Set

To apply any loads the selection of model

entity must be done first

Load can be applied on mesh and/or

geometry

Load type depends on analysis type and

application entity


Advanced Loading with Functions

Model, Functions uses to create general X vs. Y tables

Data Entry can be created

By choosing a single value, using a linear ramp or equation

By using Get XY Plot Data function from two column text file


Model, Load on Surface,

Bearing Force with Normal To

Surface option checked

Bearing Loads


Bearing Loads definitions can

have an included angle – here

bearing load is defined with 120

degree Load Angle

Femap Version 10.1.1Bearing Loads


Advanced Loading, Distributed Loads

You can make load equations as a function of nodal or element

centroidal location without having previously created a function

XEL and XND will give the x coordinate of the element's centroid, or

node's location, respectively.

The input, !i will cycle through all of the entities you selected in the

entity selection box to apply the load on.


Dynamics Analysis Load Set Options

Provides the solution type and control information for dynamics

The Model, Load, Dynamic Analysis command

Direct Transient

Modal Transient

Direct Frequency

Modal Frequency


Nonlinear Analysis Load Set Options

Model, Load, Nonlinear Analysis

Static

Creep

Transient


Heat Transfer Analysis Load Set

Options

Model, Load, Heat Transfer

command is used for:

Radiation

Free Convection

Forced Convection

Not required for conduction-

only models.


Creating Constraint Sets

Model, Constraint, Create/Manage Set command creates a new

or activates an existing constraint set

You may create as many different constraint sets


Constraints Definition

Constraints specified on model mesh

For example Model, Constraint, Nodal specifies six (6) nodal

degrees of freedom

X translation = 1, X rotation = 4

Y translation = 2, Y rotation = 5

X translation = 3, Z rotation = 6


Constraints Definition

Geometric Constraints - applied

to Geometry and Expanded to

model mesh during export into

solution

Model, Constraint, On Point

Model, Constraint, On Curve

Model, Constraint, On

Surface

Standard Types, Advanced

Types, Surface and

Cylinder/Hole predefinitions


Exercise 10 - Bearing Load


Femap Basic

FE Assembly Connections


FEM Data Units

Femap is unitless

Femap does not track units

But…

Femap standard material and beam section libraries use in-lbs units

Solid geometry defaults to inches on desktop, meters in model file database

Parasolid (regardless of product) always stores data in meters

Units conversion tool lets user convert units of data in model

User must be aware of current units system being used


FEM Data Units

Femap uses the Parasolid geometry engine to interact with CAD solid model

In order for Parasolid to guarantee the precision of solids, all entities must be within a "size box" that is 1000 x 1000 x 1000 centered at the origin

In order for parts to be modeled that would fall outside this box, most CAD systems utilize a scale factor

As recommended by Parasolid, most parts are stored internally in meters

Users expecting to work in a US unit system of inches and pounds will find that the Parasolid solid itself is 39.37 times smaller inside Parasolid.


Tools, Convert Units

Convert all quantities using

conversion of basic units

Convert specific entities with

individual conversion factors

E.g. convert N-mm units in

model to N-m

Length: 0.001 m = 1 mm

Mass: 1000 kg = 1 tonne

Force: 1 N = 1 N

Energy: 0.001 N•m = 1

N•mm

Units Conversion


Solid Geometry Scale Factor

Scaling of geometry is done

internally in Femap so that with

default scaling, a part of 1.0 on

the desktop will be stored as

0.0254 in the database

Inches on desktop, meters in

database

If user wishes to create solid

geometry in mm, then set scale

factor to 1000

Parasolid: always stored in SI no

matter what unit it is created in

Independent of product (Femap,

UGNX, SOLID EDGE, etc.)


Solid Geometry Scale Factor

Import parasolid geometry

Stored in SI

Desire to work in mm units in Femap

Solid geometry scale factor = 1000


What is a FEA Assembly?

In the context of a Finite Element Model, an Assembly should be

considered to be any FEM model with more than one element type

or property.

Examples are:

Multi-body solid assembly (same or multiple materials)

Beam models with multiple cross-sectional areas

Mixed Shell and Solid models

Mixed Beam and Shell models


Finite Element Model Connections

Coincident Node

Shell to Solid and Beam to Solid Connections

Welded Connections

Mesh “Connections” and Properties


Coincident Nodes

For model mesh check runTools,

Check, Coincident Nodes

command and Merge…

For large models, or models

where you anticipate there a large

number of coincident nodes,

uncheck the List Coincident

Entities option

Depending on how the model was

set up before meshing (e.g. use of

“Slice Match”, etc.), some meshes

will be generated automatically

with coincident nodes


Shell to Solid and Beam to Solid

Connections

Shell and Beam Elements have 6 DOFs per node, while Solids

Elements have 3 DOFs per node.

Use “RBE3” Rigid Element to transmit rotations between Solids and

Shells and Solids and Beams

To create a RBE3, use Interpolation Factor in the Rigid Element dialog

box


Rigid Elements

New Node At Center can be

used from Independent section

of Define RIGID Element

When used, FEMAP will

automatically create a node at

“center” of all the selected

Dependent (or converted Nodes

to Average) nodes


Rigid Elements

Convert button for conversion

of rigid element to

interpolation element and vice

versa. When converting from

rigid element to interpolation,

FEMAP will ask “OK to Convert

only Translational Degrees of

Freedom?”


Welded Connections

Femap supports Weld/Fastener Elements

Creates CWELD (NX , NEi, MSC) or CFAST elements for Nastrans

(NX , MSC) only

Spot Weld uses an “effective length” calculation based on the

thickness of the two shell elements connected.

A fastener element uses a similar type of connection.


Welded Connections

Femap supports Weld/Fastener Elements

Multiple options for generating Weld/Fastener Elements

Orientation of Weld is defined by either “Projection”

method or “Axis” method and may be limited by the type of

Weld selected


Mesh, Connect Menu

Generation of Constraint Equations (MPC’s), Rigid and Line

Elements connections between meshes as closest links

Also allows “unzipping” of coincident nodes


Connect Menu

Contact Regions, Properties, and Connections are moved to the

Connect menu

Connect, Automatic command finds the closest matching

surfaces between solids and automatically”

Specify search tolerance and type of contact

Model Info window has a Connections object tree


Connection (Contact) Properties

In the Define Connection Property dialog box, first select the tab for the solver

For NX Nastran select in Connect Type for different types of contact behavior like

Contact or

Glue

Always press the Defaultsbutton when switching Contact Type or manually creating a new Connection Property.


Connect Menu

Fluid Region command creates individual segmentsrepresenting incompressible fluid volume regions andis available in Nastrans (NX, MSC) supported solution sequences (SOL 103, 107-112, 129 and 200).

Bolt Region command creates individual regions of a single element or multiple elements where you would like to apply a bolt "preload" (NEi, NX, MSC).

Rotor Region command creates individual regions of nodes to be used as individual "rotors" in rotor dynamic analysis in NX Nastran. Rotor Dynamics is only supported in supported Nastran Solution Sequences 110 and 111.


Exercise 11

Solid Assembly with Linear Contact


Analysis Set Manager


FEA Solution Setup

Direct access to solver when preinstalled in File, Preferences, Interfaces…


FEA Solution Setup

Start analysis using Model, Analysis…New then typeTitle and choose

Analysis Program and Analysis Type, OK


FEA Solution Setup

Analyze starts solution of active

Analysis Set

Export creates Nastran input file

like .DAT, .NAS

Active selects Analysis Set for

solution

Preview Input displays input file,

which can be edited, analyzed or

exported


NX Nastran Solution Setup

Direct access from Model, Analysis… choose New Analysis Set

and NX Nastran as Analysis Program


Check Analysis Options and Analyze…

2-71



Close NX Nastran Monitor after solution

2-72



NEiNastran Solution Setup

Direct access from Model, Analysis… choose New Analysis Set and

NEiNastran as Solver.


Check Anaysis Options and Analyze…

2-74



Review the input file and Run analysis

2-75




Review NEiNastran Error/Warnings box after analysis regarding errors

and warnings and Exit editor


Visualizing and Documenting Results


Nodal vs Centroidal Stresses

Output data from analysis programs varies in the

position that it is calculated

Nodes or the centroid of the element

If you select nodal data, e.g., translations, Femap

uses it directly

For results with element centroid data but no corner

data, you can either:

Average the Centroidal values for all the elements connected

to each node (default); or

Use the Maximum of the Centroidal values of the connected

elements.


Nodal vs Centroidal Stresses

For results with element centroid data and element

corner data you can either:

Average the values at each node (element corner data) to

determine the data (default),

Use the maximum of the values at each node (element corner

data)

Average the Centroidal values for all the elements connected

to each node (ignores the corner data you have); or

Use the Maximum of the Centroidal values of the connected

elements.


View Select dialog box

Deformed style

Deformed

Animation

Vector

Trace

Contour style

Contour, Criteria

Beam Diagram

IsoSurface

Section Cut

Vector

Deformed and Contour Data to select data, e.g., von Mises Stress

View Select Command


Post Data can be accessed with the context-

sensitive menu (right mouse)

Key items to specify: Output Set, Deformation,

Contour, Contour Options

Deformed and Contour Data


Deformation and Contour Output Vectors can

be transformed into different directions or

coordinate systems using the Transformation

buttons.

Deformation Transformation dialog box allows

you to choose Destination to transform the

chosen nodal output vector into and which

Active Components will be displayed

Deformed and Contour Data -

Transforming Output


Contour Transformation dialog box allows you to

transform output that references global X, Y, Z

components into any chosen coordinate system or

into the nodal output coordinate system at each

node.

Deformed and Contour Data -

Transforming Output


Contour Options

The contour algorithm in Femap will use

either nodal or elemental data to perform

the contouring.

Data Conversion options

Average, Use Corner Data (default)

Average, without Corner Data

Maximum Value – with or w/o Corner Data

Minimum Value– with or w/o Corner Data

Element options

Provides the capability to “Smart Average”

results. Thus accounting for discontinuities

in material or geometry and providing a

more accurate representation of the results.

Can display Double-sided Planar Contours


Example

Four elements sharing node “N”, with corner data

Stress at node N can be calculated

Average with and without Corner Data

with: σN = (σW+ σX+ σY+ σZ)/4

without: σN = (σA+ σB+ σC+ σD)/4

Maximum Value with and without Corner Data

with: max (σW, σX, σY, σZ)

without: max (σA, σB, σC, σD)

Minimum Value with and without Corner Data

with: min (σW, σX, σY, σZ)

without: min (σA, σB, σC, σD)

Node “N”

Example – Nodal Data Conversion


Example – Nodal Data Conversion


XY Plots

Use View, Select (F5) command to

generate XY plots

XY vs ID - plots XY data as a function of ID

XY vs Set - plots XY data versus the output

set number for an Output Vector across

several Output Sets

XY vs Set Value - similar to “vs Set”, except

uses Output Set value for X

XY vs Position - plots XY data vs the position

of nodes or element in an axis direction for an

output Vector in on Output Set

XY vs Function - (not a postprocessing

option) plots XY data for a function


XY Plots of Functions

Functions can be displayed

quickly by selecting the

function to be displayed in

the Model Info window and

selecting Show from the

context-sensitive menu.

Opens a new graphics view

titled “XY Show”


Freebody Display

In the View Select dialog box,

choose Deformed and Contour

Data, Freebody Display

Plots Freebody information of

the entire body or a selected

group of elements.

Must have recovered Grid Point

Force Balance data from

analysis, if not only Applied and

reaction forces will be available.

Total Summed Loads to check

the model equilibrium

Choose the types of entities to

be viewed


Loads from a Free body Diagram

Generate a Freebody

diagram

Select the Model, Loads,

Loads from Freebody

command

Creates nodal loads from the

Free body diagram as

displayed on the screen in the

Active Load Set.


Animation Commands

Create the animation in the View Select dialog box and select

Animate as the Deformed Style

This will create an animation of the active Deformation Output

Vector in the Deformed and Contour Data Dialog Box


Animation Options

By selecting the View, Advanced Post, Animation command, you

can control the speed of the animation.

Once the plot is animating, it can be saved as an Avi file using the

File, Picture, Save command and selecting the .avi format.


Detailed Post Processing Options

Accessed via the View, Options command

(F6 and Ctrl+O hotkeys)

Located in the Category,

PostProcessing

Long list of options, key ones include

Post Titles

On/off, Location…

Deformed Style

Scale, Automatic scaling options

Contour/Criteria Style, Levels and Legend

Note: Post Processing options are saved along

with the View Style in the View Library.


Post Toolbar

Allows quick display of Deformed and Contour plots

Detailed Postprocessing settings accessible from the Post Options

pulldown icon


Exercise 12a

Post-Processing with Deformed

Contour Plots


Exercise 12b

Post-Processing with XY Plots

Femap Basic - Day 2

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Transcript of Femap Basic - Day 2