Radioss Impact 1day

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RADIOSS for Impact Explicit Large Displacement Analysis

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Proprietary Information of Altair Engineering, Inc.I HyperWorks 10.0

Table of Contents

RADIOSS for Impact Analysis Explicit Large Displacement

Analysis Chapter 1: Introduction to RADIOSS......................................................................1

Chapter 2: RADIOSS Tools......................................................................................9 Exercise 2.1: First Run with RADIOSS ................................................................................. 15

Chapter 3: Elements...............................................................................................17 Exercise 3.1: Hands on Twisted Beam ................................................................................ 41

Chapter 4: Common Features ...............................................................................43

Chapter 5: Time Step Control................................................................................51 Exercise 5.1: Time Step Demo with an Example.................................................................. 59

Chapter 6: Materials ...............................................................................................61 Exercise 6.1: Tensile Test Setup using HyperMesh ............................................................. 71

Chapter 7: Interfaces..............................................................................................81 Exercise 7.1: Box Tube on HyperMesh ................................................................................ 97

Proprietary Information of Altair Engineering, Inc.HyperWorks 10.0 II

Proprietary Information of Altair Engineering, Inc.III HyperWorks 10.0

Chapter 1

Introduction to RADIOSS

Proprietary Information of Altair Engineering, Inc.HyperWorks 10.0 RADIOSS for Impact Analysis 1

Chapter 1 - Introduction to RADIOSS

Copyright © 2008 Altair Engineering, Inc. All rights reserved. Altair Proprietary and Confidential Information

Structural Mechanics

Fluid-Structure interaction

Material characterization

Application Fields


Stamping Safety

Composite shell

Application Fields

Proprietary Information of Altair Engineering, Inc.RADIOSS for Impact Analysis 2 HyperWorks 10.0



Computational Fluid DynamicsComputational Aero AcousticsNoise Vibration Harshness

Centrifugal Fan Noise

Centrifugal Fan Noise

Application Fields


1. Geometry (Physical model)

• 1D, 2D or 3D ? � � � � Beam, Shell or Solid ?

2. Physical laws (conservation)

• Physical laws (conservation)

• Mass conservation

• Energy conservation

• Momentum conservation (equilibrium)

3. Formulation:

• Choice of time and space discretizations

• Lagrangian

• Eulerian

• Arbitrary Lagrangian Eulerian (ALE)

4. Space Discretization:

• Finite Element (FE)

5. Time Integration:

• Newmark schemeExplicit formulation

Implicit formulation

simple form + Central Difference Method

Modeling A Physical Problem




How to combine time and space discretization?

1. Lagrangian Formulation (Structural Analysis)

• The mesh points coincide with the material points

• Elements are deformed with material

• Element deformation = Material deformation

2. Eulerian Formulation (CFD - fluid)

• Nodes fixed in space, Material goes through the mesh

• Fixed nodes � � � � No degradation of mesh in large deformation problems

3. ALE: Arbitrary Lagrangian Eulerian Formulation (Impact - missile)

• Between two previous formulations

• Internal nodes move to minimize element distortion

Formulations


Formulations

Fluid flow for three kinds of formulations




Newmark scheme

Time Integration

Explicit formulation

Implicit formulation

simple form + Central Difference Method

ttn-1 tn tn+1

21−nx&

2

1+nx&

1+nxnx1−nx

nx&&

txxx nnn∆+= −+ &&&&

21

21

txxxnnn ∆+= ++

211 &

xn+1 is obtained with a precision 2t∆


Explicit Flow Chart

Time integration

ttt ∆+=

extF •Loop over elements

∂∂

+∂∂=

i

j

j

iij x

v

x

v

21ε&

)( ijij f εσ && =( ) ( ) tttt ijijij ∆+=∆+ σσσ &

•Assemble { } { }hrgFF ,int{ }contF

∑= iii mFv&

intF

txxx nnn∆+= −+ &&&&

21

21

txxxnnn ∆+= ++

211 &




Implicit Newmark Flow Chart

[ ] [ ] [ ]CMK ,, Form

{ }{ }{ }000 ,, Initialize UUU &&&

1..7i a det. then , t,Select i =∆ αδ

( )( ) ; ;1

;2 ;1

;1 ;

; ;

76

254

21

31

2

11

0 2

tata

aa

aa

aa

t

t

tt

∆=−∆=−=−=−==

==

∆∆

∆∆

δδαδ

αδ

αα

αδ

α

[ ] [ ]CMKK 10ˆ Form aa ++=

[ ] [ ] TLDLKK =ˆ:ˆ izeTriangular

[ ] [ ] [ ] { } { } { } [ ] { } { } { }

+++

+++= ∆+∆+ UUUCUUUMRR &&&&&& tttttttttt541320 aaa aaa ˆ

{ } { }Rtttt ˆ Solve ∆+∆+ =ULDLT

{ } { } { }( ) { } { }{ } { } { } { }UUUU

UUUUU&&&&&&

&&&&&

tttttt

ttttttt

aa

aaa∆+∆+

∆+∆+

−+=

−−−=

76

320


Velocity

Non Linearity

Static Dynamic

Rupture

Damage

Buckling

Plasticity

Elasticity

Explicit

Explicit �� Implicit

Implicit




Complexity

Cost (CPU)

Static / Elastic Nonlinear Dynamic

Implicit

Explicit

Explicit �� Implicit


Explicit Implicit(-) Conditional stability (+) Always stable

(-) Small (+) Large

(+) Precision (+) Precision

(+) [M]-1 (diagonal matrix) (-) ([M]+α[K])-1 (non diagonal)

(+) Low memory (10 MW) (-) High memory (6000 MW)

(+) Dynamic and Shock problems (+) Dynamic and Static problems

(+) « Element-by-Element » method

• Local treatment

(-) Global resolution

•Need of convergence at each step

(+) High Robustness

• High and Coupled nonlinearities

(-) Low Robustness

• Null pivots, Divergence, …

(+) Relatively low cost

• « Low » CPU, « Low » Memory

(-) Too expensive

• High CPU, High Memory

ctt ∆<∆

t∆ )( sµ t∆ )(ms

( )2t∆≈θ( )2t∆≈θ

Advantages / Disadvantages





Chapter 2

RADIOSS Tools


Chapter 2 - RADIOSS Tools


Access Radioss from HyperWorks 10.0 Suite:

Radioss Tools

Launch Radioss

Radioss Manuals


Pre-Processor - HyperMesh




HyperCrash

Databases. properties. materials

• RADIOSS Input (fixed/block)• NASTRAN Format• Universal Format (IDEAS)• Ls-Dyna Format• Pam 2G Format

• RADIOSS Input (fixed/block)• NASTRAN Format• Universal Format (IDEAS)• Ls-Dyna Format• Pam 2G Format

• RADIOSS 4.1 block and Fixed Formats• RADIOSS 4.1, 4.4 & 51 Block Formats• Nastran Format• Universal Format (Ideas)• Ls-Dyna Format•Pam 2G Format


Create / Modify a RADIOSS

model from a FE mesh

Pre-Processor - HyperCrash




HyperCrash

QualityMenu

QualityMenu

Model CheckerMenu

Model CheckerMenu

ConnectionMenu

ConnectionMenu

Mesh EditingMenu

Mesh EditingMenu

LoadcaseMenu

LoadcaseMenu

SafetyMenu

SafetyMenu

Pre-Processor - HyperCrash




ENGINE

_0000.rad / D00

_0000.out / L00

_0000.rst / R00

_0001.rst / R01

_0001.out / L01 A01-Ann T01

_0001.rad / D01

Input Deck (ASCII)

Listing File (ASCII)

Restart File (BINARY)

Restart File (BINARY)Engine File (ASCII)


Animation File(Binary)

TH File (Binary)

Processor – RADIOSS Computation

STARTER


• Checks consistency of the model

• Gives you warning and errors

• Generates R00 file for engine

Listing File (ASCII)Restart File (BINARY)

Input Deck (ASCII)

STARTER

RADIOSS Starter

_0000.rad / D00

_0000.rst / R00 _0000.out / L00




• Generates output files (Annn Tnnn)

• Details the computation (Lnn)

• Generates Rnn file for restart

Restart File (Binary)

TH File (Binary)

_0001.rst / R01

ENGINE

Restart File (Binary)Engine File (ASCII)


Animation File(Binary)

T01 A001-Annn 0001.out / L01

_0000.rst / R00

RADIOSS Engine

_0001.rad / D00


• Reads animations (Annn)

• Displays selected variables (Von Mises Stress, Plastic

Strains, etc.

Post-Processor–HyperView




• Reads Time history (Tnn)

• Plots selected variables (Energies, Nodal, Element, and etc.)

Post-Processor – HyperGraph


File Description Read by Written by Format

_0000.rad

D00 (V4) Input RADIOSS File

Starter/ HyperMesh

HyperCrash

HyperMesh HyperCrash

ASCII

_0001.rad

D01 (V4) Engine input Engine

HyperCrash

/Text EditorASCII

_000n.out

L00, Lnn (V4)List files Text Editor Starter/Engine ASCII

_000n.rst

R00, Rnn (V4)Restart files Engine Starter/Engine

Binary

(by default)

Annn Animation files HyperView Engine Binary

Tnn Time history file HyperGraph EngineBinary

(by default)

RADIOSS Files



Exercise 2.1: First Run with Radioss

Objective To introduce the Radioss manager and give a first overview about the simulation process using Radioss.

The model simulates an impact of a half section box beam on a rigid wall with symmetric boundary conditions.

Model Description • Units: Length (mm), Time (ms), Mass (g), Force (N) and Stress (MPa) • Simulation time

o 0001.rad [0 – 10] ms o 0002.rad [10 – 16] ms

• The model is represented on its ½ symmetric part (Z - axes). • On the free extreme (x minor) where the 500,000 g is attached has an initial velocity

VX = 5 mm/ms applied to it. • Box dimensions = 80 x 80 x 480 with a uniform thickness = 1.5 mm • Results requested:

o /ANIM/ELEM/EPSP Plastic strain o /ANIM/ELEM/VONM Von Mises stress

• Johnson-Cook Elasto-Plastic Material /MAT/LAW2. o STEEL

ρ = 7.9 g/mm3 [Rho_I] Initial density E = 199355 N/mm2 [E] Young’s modulus ν = 0.29 [nu] Poisson’s ratio

σ0 = 185.4 [a] Plasticity yield stress

Κ = 540.0 [b] Plasticity hardening parameter n = 0.32 [nu] Plasticity hardening exponent σΜΑΞ = 336.6 [SIG_max] Max Stress



• Input files for this tutorial: MY_MODEL_0000.rad, MY_MODEL_0001.rad and MY_MODEL_0002.rad

Step 1: Open Radios Manager

Step 2: Run the model MY_MODEL_0000.rad using Radioss Manager on the class_exercise folder with the options: –starter

Step 3: Review the listing file called MY_MODEL_0000.out and verify the model: 1. If the checking had finish with no error.

2. See if there is any warning

3. Please find the minimum time step, and write it down. MIN DT = _____________.

Step 4: Edit the engine file 1. Add on the end of the file these 2 commands: If the checking had finish with no error.

/ANIM/ELEM/EPSP ............................................................................. Plastic Strains

/ANIM/ELEM/VONM ..................................................................... VonMises Stresses

Step 5: Run the engine file using the RADIOSS Manager with the option: -engine

Step 6: Review the files generated Animation (A0n) files with HyperView, Time-History (T0n) files with HyperGraph, Listing (.out) files with a Text Editor.



Chapter 3

Elements


Chapter 3 - Elements


Stress/Strain - Definitions

• Logarithmic TRUE STRAIN tensor

• Cauchy TRUE STRESS tensor

( )engtrue ll εε +=⎟⎟⎠

⎞⎜⎜⎝

⎛= 1lnln

0

( )engengtrue εσσ += 1


• Usually used for small deformation simulations :• Linear elastic studies

• Usually not used for crash analysis

• Sometimes used to resolve some special numerical problems :• Large mesh distortion due to large deformations

• Decrease of time step due to decrease of element length

• Negative volume of brick elements due to large deformation

Stress/Strain – Small strain option




• Under Integrated Elements (1 IP)• Efficiency

• Constant Stress over Elements

• Hourglass mode exists

• Zero energy deformation• Strain and stress are zero

1 2

X

Y34

IP

0=xd 0=xxε 0=xxσ

8 Nodes SOLID

4 Nodes SHELL

Hourglass Formulation


• Additional internal forces are required to maintain the deformation stability of the element • Resistance forces [ Generate an ARTIFICIAL energy

f1f21 2

X

Y

f3f4 34

IP

Hourglass - Control




• 12 translational modes:• 3 rigid body modes (1, 2, 9)

• 6 deformation modes (3, 4, 5, 6, 10, 11)

• 3 hourglass modes (7, 8, 12)

• 12 rotational modes:• 4 out of plane rotation modes (1 [ 4)• 2 deformation modes (5, 6)• 2 rigid body or deformation modes (7, 8)• 4 hourglass modes (9 [ 12)

Hourglass – Shell Modes


• 4 modes for each directions:• 12 hourglass modes for a brick element

Hourglass – Brick Modes




• For the Model: HE/IE < 10%• Plot Global Hourglass for the model in HyperGraph

• For each Subset/Part: HE/IE < 10%• Select PARTS for Output in the D00 file

• Plot Hourglass for selected Parts in HyperGraph

• Check Hourglass with HyperView• Add the command below in the Engine file

• /ANIM/ELEM/HOURG

• Display Hourglass contour over Elements

Hourglass - Checking


3D – Solid - Hexahedron

• A simple Brick element:• 8 nodes with Linear interpolation

• Integration :• Reduced 1 POINT (DEFAULT)

• Full 8 POINT

• Characteristic length

•

s

t

r

1 2

65

34

78

areafacelargestVolumelc =




Put nodes of the same edge together to obtain other shapes

Use of a normal tetra element is recommended

Degenerated Solid Elements


• Element symmetry must be respected

• Not recommended elements:

Not Rec’d Element Degenerations




3D – Solid - Tetrahedron

• 4 nodes solid tetrahedron• Linear shape functions

• Integration:• 1 POINT

• No HOURGLASS

• Shear Locking

• Low convergence


• aalc 816.032==


3D – Solid - Tetrahedron

• 10 nodes solid tetrahedron• Quadratic shape functions

• Integration :• 4 POINTS

• No HOURGLASS

• Low time step

• No shear locking

• High convergence


.0 ac2al 264

6

5==

a




Quadratic 4 nodes tetra element

• Quadratic 4 nodes tetra element• 4 nodes tetra element with enriched nodal variables (6 DOF per each node)• 4 integration points• Displacement of the dummy nodes is computed on the basis of rotational DOF

• Advantages

• High time step versus 10 nodes tetra element with same accuraccy• Shear locking effect low or negligible (it may appear in bending)• Compatibility with shells


• Other solid elements:• HA8: 8 node linear brick with variable integration schemes from 2x2x2 to

9x9x9• HEPH: 8 node linear brick with 1 integration point , Elastic-plastic physical

stabilization method• BRICK20: 20 node quadratic brick with reduced 2x2x2 or full 3x3x3

integration schemes

• SHELL16 : Thick shell element

1 2

3

5

6

78

910

13 14

1517

18

1920

4 1112

1 2

356

78

9

101314

15

16

3D – Other Elements




• Isolid: Solid & Hourglass formulations• Default = 0 1 IP

• 12 8 IP

• 24 HEPH

• Ismstr: Small Strain control• Default = 0 Large Strain

• 1 Small Strain from t = 0

• 2 Small Strain if criteria reached

3D – Solid Control Card


• Bushings• Inserts• Barriers• Bumpers• Dummies• Seat

3D – Solid - Applications




2D – Shell Q4 Formulations

• Crashworthiness simulations: Over 90% shell elements BT

• Four Node Quadrilateral Elements (Q4)• Belytshko & Tsay (BT) formulation (DEFAULT)

• 1 Integration Point [ Hourglass

• Unphysical Hourglass Control

• QEPH• 1 Integration Point [ Hourglass

• Physical Hourglass Control

• BATOZ• 4 Integration Point No hourglass


2D – Shell Q4 - BT

• 1 Integration point over the surface

• Low cost elements to save CPU time

• Four non-coplanar nodes

• Normal constant over the element (without curvature)

• The local z axis is the vector product of two element diagonals

• For warped surfaces precision

• Drawbacks: Hourglassing, flat element and cannot couple bending & membrane behavior

z

N1

N2

N3N4

4231 NNNNze ×=

4231 NNNN ×




2D – Shell Q4 - QEPH

• Four-node curved element

• Four independent normals at nodes

• Hourglass physical Stabilization

N1

N2

N3N4n1

n2

n3n4


• Fully Integrated Elements: 4 Gauss point over the element• More Expensive Today 3*CPU cost

• Variable Stress over Elements

• No Hourglass

X

Y

IP IP

IP IP

1 2

34

0≠xd 0≠xxε 0≠xxσ

2D – Shell Q4 - Batoz




• BT• Use of Q4BT (Belytschko Tsay) : robust, CPU cost effective

• Popular + Compatible + Cannot couple bending-membrane behavior

• Best choice for coarse mesh

• QEPH• 15% CPU > BT + Sensitive to mesh quality + Avoid hourglassing

• Good trade off quality/cost

• BATOZ• No Hourglass + Good curvature + Couples bending-membrane

behavior

• Best choice for fine mesh

2D – Shell Q4 - Conclusion


2D – Shell Q3 – C0

• Q3 • A flat facet element

• No HOURGLASS

• Too stiff

• Degenerated Q4 (Not Recommended)• Q4 T3

• Non homogenous mass

• distribution

m/4m/4

m/4m/4

x

yz




2D- Shell Q3 – DKT18

• DKT18: Batoz Triangle:• Three in-plane integration points with Hammer scheme

• No hourglass

• Good bending behavior but high cost element• Globally, twice more expensive than C0 element

x

yz


• Global Integration (DEFAULT)• Average value is computed

• Bad strain/stress computation for the bending out of plane

• Integration Points• From 1 to 5

• 1 IP gives no out of plane stiffness

• Use 5 for a good accuracyz

N1

N2

N3N4

2D – IP Through Thickness




• Iterative algorithm:• Use Newton-Raphson method

• CPU , precision

• Two methods :• Radial return (IPLAS = 2)

• Iterative algorithm (IPLAS = 1)

• Radial return:• CPU m, precision m

Iterative Plasticity

Iplast = 1

Plastically Admissible Stresses


• By default Radioss considers a constant thickness through the element:• Ithick = 0

• To take the thickness changes into account :• Ithick = 1

Thickness Changes

Ithick = 1

Thickness Variation




• Ishell: Shell & Hourglass • formulations

• Default = 0 BT

• 4 BT with improved Hourglass

• 12 BATOZ

• 24 QEPH

• Ismstr: Small Strain control• Default=0 Large Strain

• 1 Small Strain from t = 0

• 2 Small Strain if criteria reached

2D – Shell Control Card


Manufacturing Automotive

2D – Shell - Applications




1D – Beam Element

• A standard Euler-Bernouilli beam

• Element with three nodes• Third node to define the orientation of the cross-section

L

xy

z

1

23

y

z

1, 2 3


1D – Beam Element

• Beam inputs:• A : cross section area

• Ix : moment of inertia of cross section about local x axis

• Iy : moment of inertia of cross section about local y axis

• Iz : moment of inertia of cross section about local z axis

• Recommendations:

• Time Step:

AL > 44 10121.0 AIIA zy <<

100/01.0 << zy II )(2)(5.0 zyxzy IIIII +<<+

)3/,12/1,4min(5.0 BBa +=

cLat =Δ ρ

Ec =with

),max(/2zy IIALB =




1D – Beam Control Card


1D – Truss Element

• A standard two node element

• Material law:• Type 1 : Linear Elastic

• Type 2 : Elastic Plastic

• Property set: • A : Cross section area

• Time Step:

N1 N2

ctL

t)(

=Δ L(t) : Current Truss length

ρEc =




• Suspensions, Supports …

1D – Beam/Truss–Applications


• Type 4• Spring with 1 d.o.f.

• Type 8• Mathematical spring

• Type 12• Pulley type

• Type 13• Beam type

1D – Springs




+

=

• Simple physical spring with a dashpot•

• 1 d.o.f spring:• Tension-Compression behavior

• The nodal forces are always collinear

• Time step is depending on the spring mass, its stiffness and its damping•

MCCKMdt −+

=2

xckxF &+=

1D – Spring Type 4


1D – Spring Type 8, 12, 13

• Type 8:• Mathematical def. having 6 DOF’s total; L > 0

• Not enough DOF’s to represent Rigid Body Motion

• Global momentum not respected

• Type 12:• 3 Nodes to define pulley

• Deformable rope with friction at node 2

• Sliding is locked when node 1 or 3 touches node 2

• Type 13:• Works like a Beam element (bending & shear coupled); L > 0

• 12 DOF’s to represent Rigid Body Motion

• 3 nodes, 2 to define axis of spring and 3rd for local frame




Linear Spring Non linear Elastic Spring H=0 Non linear Elastic-Plastic SpringWith Isotropic Hardening H=1

Non Linear Elastic-Plastic Spring With uncoupled hardening H=2

Non Linear Elastic-Plastic Spring With kinematic hardening H=4

Non Linear Elastic-Plastic Spring With nonlinear unloading H=5

F

δ

F

0lδ

F

0l

residδ

δ

F

0lδ

F

0l

δ

F

0l

f2

f1

δ0l

1D – Spring Property Set


F

dtd /δ

• Dashpot behavior

• Multidirectional Failure Criteria

DX

DY

Dyp

Dyn

DxpDxn

1D – Spring Property




1D – Spring Control Card


• Joints• Rivets• Spotwelds• Pretension• Retractors• …

1D – Spring Applications




Fixed format number Description Keywords0 Void element TYPE0, VOID1 Shell element TYPE1, SHELL2 Truss element TYPE2, TRUS3 Beam element TYPE3, BEAM4 Spring element TYPE4, SPRING5 Old rivet TYPE5, RIVET6 Orthotropic solid element TYPE6, SOL_ORTH8 General spring element TYPE8, SPR_GENE9 Orthotropic shell element TYPE9, SH_ORTH

10 Composite shell element TYPE10, SH_COMP11 Sandwich shell element TYPE11, SH_SANDW12 3 nodes spring element TYPE12, SPR_PUL13 Beam type spring element TYPE13, SPR_BEAM14 General solid element TYPE14, SOLID

PROPERTY SET LIST

Element Compatibility


MATERIAL LAWS DESCRIPTIONLaw Type Description

34 BOLTZMAN Viscoelastic Boltzman25 COMPSH Elastic plastic orthotropic Composite shell14 COMPSO Elastic plastic orthotropic Composite material24 CONC Elastic plastic brittle Reinforced concrete22 DAMA Elastic plastic Ductile damage21 DPRAG Elastic plastic Drücker-Prager Law for rock or concrete, hydrodynamic behaviour is given by a function1 ELAST Elastic Linear elastic model

19 FABRI Shell orthotropic Linear elastic orthotropic33 FOAM_PLASTIC Viscous plastic Closed cell, elasto-plastic foam35 FOAM_VISCOUS Viscous elastic Generalized Kelvin-Voigt32 HILL Elastic plastic orthotropic Hill’s model43 HILL_TAB Elastic plastic orthotropic Tabulated Hill model28 HONEYCOMB Orthotropic Honeycomb material4 HYD_JCOOK Johnson Cook Strain rate and temperature dependent yield stress6 HYD_VIS Hydrodynamic Viscous Turbulent viscous flow3 HYDPLA Elastic plastic hydrodynamic Von Mises isotropic hardening, polynomial pressure

40 KELVINMAXWELL Viscous elastic Generalized Maxwell - Kelvin law10 LAW10 Elastic plastic Drücker-Prager Law for rock or concrete, hydrodynamic behaviour is polynomial23 LAW23 Elastic plastic Ductile damage42 OGDEN Hyperelastic Ogden - Mooney-Rivlin27 PLAS_BRIT Elastic plastic brittle Brittle shell (aluminum, glass)2 PLAS_JOHNS Elasto plastic (Johnson Cook) Von Mises isotropic hardening

36 PLAS_TAB Elastic plastic Piecewise linear2 PLAS_ZERIL Elastic plastic (Zerilli-Armstrong) Von Mises isotropic hardening

29 USER1 User’s30 USER2 User’s31 USER3 User’s38 VISC_TAB Viscous elastic Foam (Tabulated law)0 VOID Void material Fictitious





Law 2D QUAD 3D BRICK SHELL TRUSS BEAM34 BOLTZMAN yes yes25 COMPSH yes14 COMPSO yes yes24 CONC yes yes22 DAMA yes yes yes21 DPRAG yes yes1 ELAST yes yes yes yes yes

19 FABRI yes33 FOAM_PLASTIC yes yes35 FOAM_VISCOUS yes yes yes32 HILL yes43 HILL_TAB yes28 HONEYCOMB yes yes4 HYD_JCOOK yes yes6 HYD_VIS yes yes3 HYDPLA yes yes

40 KELVINMAXWELL yes yes10 LAW10 yes yes23 LAW23 yes yes42 OGDEN yes yes27 PLAS_BRIT yes2 PLAS_JOHNS yes yes yes yes yes

36 PLAS_TAB yes yes yes2 PLAS_ZERIL yes yes yes

29 USER1 yes yes yes30 USER2 yes yes yes31 USER3 yes yes yes38 VISC_TAB yes yes0 VOID yes yes

ELEMENT COMPATIBILITY



Exercise 3.1: Hands on Twisted Beam





Exercise 3.1: Hands on Twisted Beam

Objective To test different shell element formulations available in RADIOSS with a twisted beam.

BT Shell behaves poorly when the elements are warped and in bending. The test will confirm this.

Model Description • Units; NOT DEFINED.

• Simulation time

o D01 [0 – 0.02001]

o D02 [0.02001 – 0.05001]

• The model is a rectangular plate twisted on Axes X.

• The simulation consist on clamp on one extreme and on the other apply a force on the middle node with the value = 1 on Y direction.

• Plate dimensions = 12 x 1.1 with a uniform thickness = 0.32 mm

• Elastic Material: /MAT/LAW1.

ρ = 7.34e-3 [Rho_I] Initial density

E = 29e6 [E] Young’s modulus

ν = 0.22 [nu] Poisson’s ratio

• Input files for this tutorial:

o BT : TWISBEAM_0000.rad, TWISBEAM_0001.rad and TWISBEAM_0002.rad

o BATOZ: TWISBE12_0000.rad, TWISBE12_0001.rad and TWISBE12_0002.rad

o QEPH : TWISBE24_0000.rad, TWISBE24_0001.rad and TWISBE24_0002.rad



Step 1: Copy the folders BATOZ, BT and QEPH from the Model Files directory to the solved folder.

Step 2: Open RADIOSS Manager

Step 3: Run the models TWISBE12, TWISBEAM and TWISBE24 using RADIOSS Manager on the class_exercise folder with the option: –both

Step 4: Review the listing files for each run and verify on the results: 1. Plot Dy (Y-Displacement) of the node in time history with HG (one window for each shell

formulation)

DISPLACEMENT (mm)



Chapter 4

Common Features


Chapter 4 - Common Features


• The interfaces solve the contact between two parts

• Different kinds of interfaces exist depending on the contact

Surface 2

Surface 1

Interfaces


• Four kinds of rigid walls are available• Infinite plane

• Cylindrical rigid wall

• Spherical rigid wall

• Parallelogram

• Each wall can be fixed or moving

• A rigid wall is defined by a Master Node and a group of slave Nodes

• The group of Slave Nodes is defined by an explicit list and/or by a “distance for slave search”

• A rigid wall is a Kinematic Condition

Rigid Wall




Diameter

M

Slave Nodes

M1M0

Plane Rigid Wall

SphericalM

M1 Cylindrical

Slave Nodes

Rigid Wall


• A Rigid Body is an underformable structure

• A Rigid Body is defined with a set of slave nodes and a master node

• A kinematic condition is applied on each node and for all directions

• By default, the master node is moved to the center of mass

Input master nodelocalization

Rigid body center of mass

Rigid Body




Rigid Parts (Undeformable parts, wallsengine, battey) Connections between Parts

Rigid Body


• Simulate a volume of gas or fluid

• Requirement• The surface defined must be closed

• The shell normal must be oriented outward the volume

• Only 3 or 4 shell elements sets

• 5 types of monitored volume• Type 3 for tire and fuel tank

• For simple unfolded airbag use monitored volume type 4

• For chambered airbag use type 5

Monitored Volumes




Tire

Tank

AirbagDeploying

Monitored Volumes


• A boundary condition is a constraint on node degrees of freedom

• A boundary condition is a kinematic condition

• 6 degrees of freedom :• X translation

• Y translation

• Z translation

• X rotation

• Y rotation

• Z rotation

#-BOUNDARY CONDITION:#--1---|---2---|---3---|---4---|---5---|/BCS/1boundary_condition#trarot nskew gr_node101 110 0 1004

# BCS NODE GROUP/GRNOD/NODE/1004group_of_nodes

207#--1---|---2---|---3---|---4---|---5---|

Boundary Conditions




• Initial velocity: defined by a value in each direction and a group of nodes

• Imposed velocity: defined by a function, a direction and a group of nodes

• Imposed displacement (Block only): same as Imposed Velocity

Velocity & Imposed Displacements


Concentrated load Pressure load

Gravity load

F P

g

Loads & Gravity




• An added Mass is a mass which is added on a group of nodes

• The mass is equally divided among the nodes in the group or is added to each node of the list

#-ADDED MASS:#--1---|---2---|---3---|---4---|---5---|/ADMAS/1/1BOAT#- Mass| Node|

0.5 1000/GRNOD/NODE/1000/ADDED MASS

207

Added Masses


• SKEW FRAMES are used to define local directions

• Two types of skew frames are available in RADIOSS• Fixed skew frame

• Moving skew frame

Moving skew frame (defining by 3 nodes)

YsZs

Xs

Fixed skew frame

Skew Frames




• A section is a cut in the structure where forces and moments will be stored in TH files

• A section is defined by a group of element, a group of nodes and a skew defined by three nodes

Sections



Chapter 5

Time Step Control


Chapter 5 - Time Step Control


• Explicit Scheme:• Conditionally stable

• If Stable scheme

• Unstable case:• If information passes across more than one element per time step

• Stability Condition depends on two factors:• Size of the smallest element Numerical

• Sound propagation speed Physical

criticaltt Δ<Δ

Fext(t)L

Stability of Time Integration


• Courant’s stability condition

• Characteristic length• It depends on the shape of the element:

clt c<Δ

c : Speed of sound in the material

lc : Characteristic element length

l

l cl cll

l

lD

DAlc =lc = 0.707 l lc = 0.866 l

Courant’s Stability Condition




• In principle, no need of user intervention (automatic)

• The time step is calculated using two methods:• Element time step

• Nodal time step

• The time step is influenced by existence of interfaces• Interface time step

Time Step Control in Radioss


Element Time Step Control

• For the smallest element, the following relation must be verified:

• Scale Factor:• To ensure the stability

• To introduce the nonlinearity in Courant’s condition

• Particular cases:• One element mesh Sf = 0.1

• Foams (high nonlinearity) Sf = 0.67

⎟⎠⎞

⎜⎝⎛<ΔclSt fe Where Sf is the Scale Factor

σ

ε

↓Δ etρρε

σ∂

∂=<Δ c

Ec

ellt ↑∂

∂ε

σ↑ε




Nodal Time Step Control

• For any node, the following relation must be verified:

• For a regular mesh:

• For an irregular mesh (generally):

m : nodal massk : equivalent stiffness of nodek

mtn2

<Δ

en tt Δ=Δ

en tt Δ>Δ


• The interface time step depends on the type of interface used:

• Type 2: • Just a kinematic condition No need of time step condition

• Types 3, 4, 5 and 8:• A small stiffness is used Stable with Sf = 0.9 or less

• Types 7, 10 and 11:• A variable stiffness is used

• May be large enough compared to element stiffness

• A stability condition must be established

kmti

2=Δ

Interface Time Step




RADIOSS Input for Time Step Control

Time Step Control in Engine (0001.rad) file

/DTΔTsca ΔTmin

/DT/BRICK/DT/SHELL/DT/QUAD Element Time Step Control/DT/SH_3N/DT/BEAM…

/DT/INTER Interface Time Step Control/DT/NODA Activate Nodal Time Step Control

Larger Time Step for non-optimized mesh


• /DT/Keyword2ΔTsca ΔTminKeyword 2: Brick, Quad, Shell, Sh3n, Truss, Beam, Spring, Airbag, Inter, Noda

• /DT/Keyword2/Keyword3ΔTsca ΔTminKeyword 2: Stop, Del, Cst

• Delete Option

/DT/BRICK/DEL

/DT/SHELL/DEL

…

/DT/INTER/DEL

• DEL option Mass / Volume is lost Change of the physicsChange of the physics

To delete Elements where mintte Δ<Δ

To remove nodes from interface where mintti Δ<Δ





• Constant Option:/DT/NODA/CST

/DT/INTER/CST

• To apply a constant time step

• Radioss adds mass to the model to satisfy the nodal stability condition

• Increase of kinetic energy

• The added mass should be checked by user to ensure the validity of results

/DT/BRICK/CST

/DT/SHELL/CST

• Switch an element to small strain formulation time step is then independent of the size of the element



• Many time step options influence the results:• Keep the numerical model close to the physical problem

• Small Time Step for:• Stiff material:

• Light material:

• Small element:

• For mild steel:

• Remove details to save CPU time

• More than 1 Million elements are needed to mesh a complete car model with 5x5mm2 elements

↑E

↓ρ

↓l

↓Δt

↓Δt

↓Δt

(For crash problems)

With ρEel

clt ==Δ

Characteristic lengthfor elements

mml 5min ≈smc /5000≈st μ1≈Δ

Remarks on Time Step Control




• Default values:• Scale factor = 0.9

• Minimum time step = 0

• By default if Δte < Δtmin :• Radioss deletes the shell element which control the time step

• Radioss stops calculation if a brick element control the time step

• The /DT/INTER concerns only the interface type 7

Remarks on Time Step Control


• Take a simple Tensile Test model• Case 1: Run it with Natural Time Step (No Time Step Commands)

• Time Step is 2.164E-4

• Total Number of Cycles = 55467 Cycles

• Case 2: Add Command:/DT/NODA

0.9 0

• Time Step = 2.2521E-4

• Total Number of Cycles = 53291 Cycles

• This proves that Nodal Time Step > Element Time Step

• Case 3: Add Command:/DT/NODA/CST

0.9 3E-4

• Time Step = 3E-4 Must be input after reviewing Nodal Time Step in Starter Listing File

• Total Number of Cycles = 40001 Cycles with 2.19% Added Mass 28% Faster Computation

• This explains why we add mass to the models For Faster Computation Time

• In Dynamic Analysis, it’s recommended not to add more that 2% Mass

Demo of Time Step Control in RADIOSS




Exercise 5.1: Time Step Demo with an Example



Exercise 5.1: Time Step Demo with an Example

Objective

To understand the influence of time step commands by using tensile test model.

vρ

TENSILE

Only a quarter of the specimen is needed to be meshed:

Model Description

• UNITS: Length (mm), Time (ms), Mass (kg), Force (kN) and Stress (GPa) • Simulation time

o 0001 [0 – 10] • The model is Quarter size mesh with symmetric boundary conditions. • Boundary Conditions:

o The 3 upper right nodes (TX, TZ and RZ, RY, RZ) o The center node on left is totally fixed (TX, TY, TZ, RZ, RY, RZ)

o A symmetry boundary condition on all bottom nodes (TY, TZ, RZ, RY, RZ) • Proof bar dimensions = 11 x 100 with a uniform thickness = 1.7 mm • Elastic-plastic Material: /MAT/LAW2 (Aluminum 6063 T7)

ρ = 2.7e-6 Kg/mm3 [Rho_I] Initial density E = 60.4 GPa [E] Young’s modulus ν = 0.33 - [nu] Poisson’s ratio σ0 = 0.09026 GPa [a] Yield Stress K = 0.22313 GPa [b] Hardening Parameter n = 0.374618 - [n] Hardening Exponent σmax = 0.175 GPa Maximum Stress

All other values that are not listed above are default values.



These are the main steps of this exercise: 1. Run the model without any time step control (natural time step)

2. Set a nodal time step

3. Set a constant nodal time step.

Step 1: Run the model without time step commands. 1. Launch RADIOSS using the launcher located on Programs >> Atair HyperWorks >>

RADIOSS

2. On the input file select the starter file TENSI51_0000.rad

3. Enter with the options – both to run the starter and the engine at the same time.

3. Select Run.

4. After you run the model, open the file TENSI51_0001.out and look for the TIME-STEP values, write down here the mean value you have found.

Element time step = _____________.

Step 2: Run the model with /DT/NODA. 1. Open the file TENSI51_0001.rad and add this command to it:

/DT/NODA

0.9 0

2. Repeat the steps 1.2 – 1.4.

Mean time step = _____________.

Step 3: Run the model with /DT/NODA. 1. Open the file TENSI51_0001.rad and add this command to it:

/DT/NODA/CST

0.9 0.3E-3

2. Repeat the steps 1.2 – 1.4.

Mean time step = _____________.

DM/M = _____________



Chapter 6

Materials


Chapter 6 - Materials


Material Laws In RADIOSS

(15)Composite Shell with Chang-Chang failure

(43)Hill (tabulated)

Composite Solids

Composite Shell

Hill

Crushable foam

Honeycomb

Fabric

Ogden-Mooney-Rivlin

Hook

Model

(14), (53)

(25)

(32)

(50)

(28)

(19)

(42)

(1)

Law (MID)

Elastic-plastic orthotropic composites

Elastic-plastic orthotropic shells

Nonlinear pseudo-plastic orthotropic solids with strain rate effect

Nonlinear pseudo-plastic orthotropic solids without strain rate effect

Linear elastic for orthotropic shells

Composite and

Orthotropic materials

Hyper elastic

Linear elastic modelIsotropic Elasticity

DescriptionType



(52)Ductile damage for porous materials, Gurson

von Mises with viscoplastic flow

(23)Ductile damage for solids

(2)Johnson-Cook

(2)Zerilli-Armstrong

Ductile damage for solids and shells

Reinforced concrete

Predit rivets

Aluminum, glass, etc.

Drucker-Prager for rock or concrete

Piecewise linear

Cowper-Symonds

Zhao

Model

(44)

(22)von Mises hardening with ductile damage

(24)

(54)

(27)

von Mises hardening with brittle damage

(10), (21)

(36)

(48)

Law (MID)

von Mises hardening without damage

Elastic-plasticity of

Isotropic Materials

DescriptionType





(34)Boltzmann

(35)Generalized Kelvin-Voigt

(38)Tabulated law

(40)Generalized Maxwell-Kelvin

Fictitious

Steinberg-Guinan

von Mises isotropic hardening with polynomial

pressure

Hydrodynamic viscous

Johnson-Cook

Closed cell, elasto-plastic foam

Model

(4)Strain rate and temperature dependence on yield stress

(6)Turbulent viscous flowHydrodynamic

(0)Void materialVoid

(49)Elastio-plastic hydrodynamic with thermal softening

(3)Elastio-plastic hydrodynamic

(33)Visco-plastic

Law (MID)

Visco-elasticViscous Materials

DescriptionType


Failure Models In RADIOSS

• Independent and can be coupled with compatible material laws

• /FAIL/TYPE/MAT_ID




• Law 2: Elastic Plastic Isotropic (Von Mises)

• Law 27: Elastic Plastic Brittle

• Law 28: Honeycomb Material

• Law 36: Elastic Plastic Isotropic Piecewise Linear

Materials discussed in this class


• Elastic for stresses lower than the yield stress

• Plastic when the stress reaches the yield stress

• Available for brick, shell, beam and truss elements

• Two plasticity models:• Johnson-Cook

• Zerilli Armstrong

Material Law 2: Elastic-Plastic




Stress-Strain relation:

)1)(ln1)(( *0

mnp Tcba −++= ε

εεσ &&

Influence of temperature change

Influence of strain rate

Influence of plastic strain

σ

pε

a

b

= Stress level

= Plastic strain

= Yield stress

= Hardening modulus

n = Hardening Exponent

c = Strain rate coefficientε&

0ε&= Strain rate= Reference strain rate

Material Law 2: Johnson-Cook


Stress-Strain relation:

Influence of temperature change and strain rate

Influence of plastic strain

σ

pε

= Stress level

= Plastic strain

C0 = Yield stress

n = Hardening Exponent

ε&

0ε&

= Strain rate

= Reference strain rate

( )( )( ) npCTCTCCC εσ ε

ε54310 0

lnexp ++−+= &&

Material Law 2: Zerilli-Armstrong




• Element rupture if the plastic strain is larger than εmax

• For shell elements:• Ruptured element is deleted

• For solid elements:• Deviatoric stress tensor is set to zero

• The element is not deleted

Material Law 2: Element Rupture


Layer crackingCrack orientation

1

2

• Only for shell elements• The isotropic elastic-plastic computation and modeling is the

same as for law 2• Law allows material damage and brittle failure

• Glass, aluminium, …

• Brittle failure is modeled by the introduction of a crack• Crack throughout the element thickness for type 1 elements (regular

shell)• Crack in the layer that the material is applied for type 11 elements

(composite shell with variable layers)

Material Law 27: Elastic-Plastic Brittle




• Damage effected material

• Nominal and effective stress:

• Linear damage:

• Linear stress:

εt1 = Tensile rupture strain in direction 1εm1 = Maximum strain in direction 1dmax1 = Maximum damage in direction 1εf1 = Maximum strain for element

deletion in direction 1

σ

ε

yσ

E E(1-d)

ptε tε mε

Linear damageLinear stress

( )deffn −= 1σσ d : damage factor 0 < d < 1

tmtd εεεε−−=

( )( )( )p

ttm

mE εεεεεεσ −

−−

=

Material Law 27: Damage Model


• Typical honeycomb, crushable foams

• Only for solid elements

• Two drawbacks:• No viscous effect

• Plastic behavior

• Material behaves as three independent membrane spring:• Hook’s law

• For an isotropic material

s

t

r

1

5

2

6

34

78

⎪⎪⎪

⎭

⎪⎪⎪

⎬

⎫

⎪⎪⎪

⎩

⎪⎪⎪

⎨

⎧

⎥⎥⎥⎥⎥⎥⎥

⎦

⎤

⎢⎢⎢⎢⎢⎢⎢

⎣

⎡

=

⎪⎪⎪

⎭

⎪⎪⎪

⎬

⎫

⎪⎪⎪

⎩

⎪⎪⎪

⎨

⎧

31

23

12

33

22

11

31

23

12

33

22

11

31

23

12

33

22

11

000000000000000000000000000000

εεεεεε

σσσσσσ

GG

GE

EE

332211 EEE == 231231211EGGG ===and

Material Law 28: Honeycomb




• Plasticity is represented by independent stress-strain curves• Material behavior is always orthotropic

• The input yield stress is always positive

• Volumic strain or strain dependent yield curve (user’s choice)

• The failure plastic strain is input for each direction• If the failure strain is reached in one direction, the element is deleted

User definedyield curve ij

ijσ

( )10−= ρ

ρμ ijεor

Material Law 28: Honeycomb


• Isotropic elastic-plastic material

• User defined function for the stress-strain curve

• Available for brick and shell elements

• Elastic portion of material stress-strain curve defined by Young modulus and Poisson’s ratio

• Material plasticity curves can be given for an arbitrary number of strain rates

• Linear interpolation of strain-stress curve

• For a given strain rate

• For a given plastic strain0εε &&≤1εε &&=1εε &&≥

pε

σ

Mat. Law 36: Elastic-Plastic Tab.




Exercise 6.1: Hands on Tensile Test





Exercise 6.1: Tensile Test Setup using HyperMesh

Objective To simulate a uniaxial tensile test using a quarter size mesh with symmetric boundary conditions

Only a quarter of the specimen is needed to simulate the tensile test

Model Description • UNITS: Length (mm), Time (ms), Mass (kg), Force (kN) and Stress (GPa) • Simulation time D01 [0 – 10.] • The model uses Quarter size mesh with symmetric boundary conditions. • Boundary Conditions:

o The 3 upper right nodes (TX, TZ and Rx, RY, RZ) o The center node on left is totally fixed (TX, TY, TZ, Rx, RY, RZ)

o A symmetry boundary condition on all bottom nodes (TY, TZ, Rx, RY, RZ) • At the left side is applied a constant velocity = 1 mm/ms on -X direction. • Proof bar dimensions = 11 x 100 with a uniform thickness = 1.7 mm

Johnson-Cook Elastic Plastic Material /MAT/PLAS_JOHNS (Aluminum 6063 T7)

• ρ = 2.7e-6 Kg/mm3 [Rho_I] Initial density • E = 60.4 GPa [E] Young’s modulus

• ν = 0.33 - [nu] Poisson’s ratio • σ0 = 0.09026 GPa [a] Yield Stress • K = 0.22313 GPa [b] Hardening Parameter • n = 0.374618 - [n] Hardening Exponent • σmax = 0.175 GPa [SIG_max] Maximum Stress • ε max = 0.75 [EPS_max] Failure Plastic Strain

Input file for this tutorial: tensile.nas.



Step 1: Load the model. 1. Launch HyperMesh.

2. Go to Preferences pull-down menu, pick User Profiles….

3. Pick Nastran and click OK. 4. Go to the File pull-down menu and pick Import.

5. Navigate until you pick the file tensile.nas

6. Click Import.

Step 2: Convert Nastran deck to RADIOSS. 1. Go to Tools menu , convert functionality.

2. Select the NASTRAN to RADIOSS {Block Format} option as below

3. From the Nastran to Radioss conversion browser on the left select the Radioss template

as Block44 and hit the convert button. A conversion status window pops up showing the completion of conversion and the Radioss block user profile is automatically loaded

4. Note: You can use the Convert panel from the TOOLS page instead. However the convert option from the menu bar is recommended.

Step 3: Update the materials.

1. On Collector toolbar, click Materials ( ).

2. Go to update sub-panel.

3. Click mats button and select Mat1_1.



4. Click select. 5. Click type = ELASTO-PLASTIC

6. Click card image = and select M2_PLAS_JOHNS_ZERIL.

7. Click update/edit button

8. Input the values as shown in the following image.

9. Click return twice to get back to main menu.

Step 4: Update the properties.

1. On Collector toolbar, click Properties ( ).

2. Go to update sub-panel.

3. Click props button and select PSHELL_1.

4. Click select. 5. Click card image = and pick P1_SHELL.

6. Click update/edit 7. Input values as shown in the following image.

8. Click return twice to get back to main menu.



Step 5: Update bar component with material and property.

1. On Collector toolbar, click Components ( ) 2. Go to update sub-panel. 3. Click comps button and select COMP_PSHELL_1.

4. Click card image = and pick Part. 5. Click update

6. Click return to exit the panel.

7.

Step 6: Create Boundary Conditions 1. From the utility page, start the BC’s manager or pull down menu Tools BCs manager, 2. Enter name as constraint1, choose type boundary condition and set the GRNOD to Nodes

3. Click on the nodes, nodes selection appears; select the three nodes as shown in the figure below and click proceed.

4. Fix all degrees of freedom, except Ty

5. Click create tab to create the constraint. The created constraint appears in the table also handle appear in graphics

6. Enter name as constraint2, choose type boundary condition and set the GRNOD to Nodes

7. Select node as shown in the picture below



8. Fix all degrees of freedom

9.Click create tab to create the constraint. The created constraint appears in the table also handle appear in graphics 10. Enter name as constraint3, choose type boundary condition and set the GRNOD to Nodes

11. Select node as shown in the screen

12. Fix all degrees of freedom except Tx

13.Click create tab to create the constraint. The created constraint appears in the table also handle appear in graphics

Step 7: Create Imposed Velocity 1. From the utility page, start the BC’s manager,. 2. Enter name as velocity, choose type imposed velocity and set the GRNOD to Nodes 3. Select the nodes as shown in the figure below

4. Set the direction as X and Y scale as -1.0 5. Click on the Create/Select curve ID, a XY curve editor comes up 6. Create a new curve with Name Load and values as in table



7. Close the XY curve editor, the created curve is assigned to this constraint 8. Click create to create the velocity boundary condition

Step 11: Create output requests. 1. Go to the Utility Menu and click Engine File.

2. In the RADIOSS Engine File Tool window, click the GENERAL tab and enter values as in the following image:

3. Click Apply.

4. In the ANIM tab, enter values as in the following image, open the panel if something is not visible:



5. Click Apply.

6. Click Close.

Step 12: Export the model as TENSILED00.

1. On Standard toolbar at the top of the HyperMesh window, click Export ( ).

2. For File:, click the folder icon and navigate to destination directory where you want to run.

3. Enter the name TENSILED00 and click Save.

4. Click the downward-pointing arrows next to Export options to expand the panel.

5. Click Auto export engine file to export the engine file with the model file.



6. Click Export. 7. Click Close.

Step 13: Open RADIOSS Manager from windows Start menu

Step 14: Run the model TENSILED00 using RADIOSS Manager on the class_exercise folder with the option: –both

Step 15: Review the listing files for this run and verify on the results: 1. See if there is any warning or errors on .out files

2. Using HyperView plot the displacement and strain contour.



EXERCISE EXPECTED RESULTS

Total Displacement Contour (mm)

Plastic Strain Contour





Chapter 7

Interfaces


Chapter 7 - Interfaces


For beams, bars or springs

Edge-to-edge impact (7+11)Impact between two lines11

Tied After impact with or without reboundLike type 7 but with a tied contact10

Good contact at all speedsGeneral purpose contact impact between 2 parts7

User defined contactContact between two rigid bodies6

Not recommended anymoreContact for a single part4

Use of type 7 is recommendedContact between 2 parts3 & 5

Change of mesh density (solid)Tied interface, No sliding2

Fluid structure interactionFor Radioss ALE1 & 9

CommentsDescriptionType

Interfaces in RADIOSS


Radioss/Madymo CouplingEllipsoidal surfaces to segments contact15

Radioss/Madymo CouplingEllipsoidal surfaces to nodes contact14

ALE or Euler or Lag.Connects 2 fluid meshes with free, tied or periodic options12

CommentsDescriptionType

Fluid-structure inetractionsCEL Lagrange / Euler interface18

Meshes with 8- or 16-node thick-shell or 20 bricks

Contact between nodes to quadratic shape solids and solid-shells or between quadratic

shapes

16 / 17

Interfaces in RADIOSS

19 Slave and Master Surfaces Combination of Type 7 and Type11

21 Rigid master surface/slave surface Fast interface for Stamping




• The interfaces solve the contact between several parts of the model

• Contact modeling:• Type 7:

• Node-to-surface contact

• Symmetric Node-to-Surface contact

• Self-contact Node-to-Surface

• Generalized Node-to-Surface contact

• Type 11:• Edge-to-Edge contact

• Contact treatment:• Kinematic master-slave formulation

• Penalty method

Contact Modeling & Treatment


The velocity and displacement of the slave nodes are controlled by the master segments in order to satisfy the kinematic contact conditions

Slave nodes

Master surface

Nodes-to-Surface Contact




• The nodes of each surface are treated as slaves

• Each surface is treated as a master surface

Slave + Master

Slave + Master

Symmetric Nodes-to-Surface


Self-contact of a single surface due to buckling ...

Slave node + Master surface

Self-contact Nodes-to-Surface




• A node may be master and slave at the same time

• Slave nodes may belong to different surfaces

Slave NodesMaster nodes

Master surface

Generalized Nodes-to-Surface


Limitation of Nodes-to-surface




For contacts between beams, bars, springs or the edges of shells

Edge-to-Edge Contact


• Penalty method:

• A spring is added between a slave node and a master segment

• Each contact is treated as an element

• The kinematic continuities are not directly respected

• The energy conservation is verified

• The stiffness of the spring is very important

• Too stiff Numerical instabilities

• Too flexible Large penetration, kinematic discontinuity

Vm VsMm MsInterface Spring

Contact treatment in RADIOSS




• Type 2: Tied interface

• Type 7: General contact

• Type 11: Edge-to-Edge interface

Interfaces discussed in this class


• Tied interface is a kinematic condition

• Applications:

• To connect a fine and a coarse solid lagrangian mesh

• To connect spring elements to shell surfaces for spotweld or rivet modeling

Shell elements (master segments)

Spotwelds modeled by spring elements (slave nodes)

Type 2: Tied Interface




• Tied interface formulation:

• Masses and forces of the slave nodes are added to the master nodes

• Accelerations and velocities of the master nodes are computed with the added masses and added forces

• Kinematic constrains are applied to all slave nodes in order to keep them on the initial position with respect to their master segments

Type 2: Tied Interface


• For all types of impact between a set of nodes and a master surface

• A node can impact on several master segments

• A node can impact on the edge of a master segment

• Direct search of the closest segment• No search limitation

• Only edge-to-edge contacts are not solved

• Possible to put a slave node on the master surface

• Impact is possible on the two sides of segments

• Variable interface stiffness is used to avoid penetration larger than gap

• A time step is computed to insure the stability

Interface Type 7




Type 7: Search Algorithm

Fast Sorting Method


• A gap is used to:

• Give a physical thickness to the surface

• Allows to distinguish the impacts on the top or the lower part from the facet

• The contact is activated if:

• The node penetrates inside the gap

• Distance Between Node to Surface < Gape

P

PMaster gap

Slave gap

Type 7: Detection of Penetration




• Physical value for constant Gap:• GAP = 1/2 (thickness1+thickness2)

• Default value for GAPmin (used if no constant gap is given)• GAPmin= min (lmin/10 , t , l/2)

• lmin : the smallest side length of the master brick element

• l : the side length of the element brick

• t : thickness of the master shell

e1

e2

Type 7: Constant Gap


• Possible to use a different gap value for each interface segment

• The gap is computed for each impact as:

• Gap = Gapm+ Gaps (m: master s: slave)

• Gapm= ½ shell thickness or zero for brick elements

• Gaps = ½ largest thickness of the elements connected to the slave node

• or zero for a node connected to a brick or spring elements

• or ½ (beam cross-section)1/2 for beam elements

• If the slave node is connected to multiple elements, the largest Gaps is used

• The minimum value of Gap is given by Gapmin as it is explained previously

Type 7: Variable Gap




F

)(5.0pg

gsEtKCPKF sdtdp

s−

=+= Where E and t are the young modulus and thethickness of the master surfaceS is a scale factor (1 by default)

Type 7: Penalty Force


Type 7: Time Step

• A kinematic time step is applied to prevent large penetrations

• If dp/dt > 0

• For a crash problem:

• The nodal time step is computed as following:

p

g-pg

With

ssmm

mmt μ100)/5000(2

1=≤Δ

( )( )dtdp

pgt/

5.0 −≤Δ

KMt 2

≤Δ elementsInterface KKK +=




• Initial penetration is not allowed for interface type 7

• The node is deactivated from interface when:

• node to element mid-plane distance is smaller than 10-10*Gap

• For self impacting surfaces, use the following recommended value:

• Gap < (smallest segment edge) / 2

• For impact between stiff and soft materials the stiffness factor has to be adjusted

• S = Eslave*Thickslave / Emaster*Thickmaster

Type 7: Hints and Remarks


Contacts between a soft and a rigid part (foam/steel or tire/structure)

Rigid Soft

SlaveMaster

K1=Eslave / Emaster K2 = Eslave / Emaster = 1 / K1

2 interfaces

Rigid Soft

MasterSlave





• Deep penetrations are not tolerated • Deep penetration leads to:

• high penalty forces

• small time step

• infinite loop message

• large contact force vectors in post-processing

• Deep penetrations are caused by:• Initial penetrations of adjacent plates• Edge impacts• Full local collapse• Rigid body impact on another rigid body or on fixed nodes or on very stiff part• Impact between heavy stiff structures• High impact speed• Small gap



• Time step reduces for high speed impacts or small gaps

• To avoid time step problems:

• Increase gap, but check if no initial penetration is resulted

• Increase stiffness factor STFAC

• Some ENGINE options can be used but attention should be paid to the quality of results:

• /DT/INTER/DEL

• Some nodes will be allowed to pass through the impacted surface

• /DT/INTER/CST

• Nodal masses will be modified to maintain a constant time step





• Initial penetrations:• are generally due to the discretization

• result in high initial contact forces

• should be avoided

• Remedies:• Modify node coordinates

• Reduce gap• For small penetrations

• Deactivate node stiffness• Simple approach

• Option used after geometry adjustments

Initial penetration



• Simulates impacts between two lines

• Lines: Beams, Bars, Springs, Edge of shell elements

• Works as the interface type 7:

• Penalty formulation

• Same search method

• In association with interface type 7, the edge-to-edge impacts can be simulated

Interface Type 11




Exercise 7.1: Hands on Boxtube





Exercise 7.1: Box Tube on HyperMesh

Objective

To simulate buckling of a tube using half tube mesh with symmetric boundary conditions on X axis.

The figure illustrates the structural model used for this tutorial: a half tube with a rectangular section (38.1 X 25.4 mm), a length of 203 mm.

Model Description

• UNITS: Length (mm), Time (ms), Mass (kg), Force (kN) and Stress (GPa) • Simulation time: Engine [0 – 10.01] • The tube thickness is 0.914 mm. • An imposed velocity of 13.3 mm/ms (~30MPH) is applied to one of the ends of the

tube • Elasto-plastic Material /MAT/PLAS_JOHNS. (STEEL)

o ρ = 7.8e-6 Kg/mm3 [Rho_I] Initial density o E = 210 GPa [E] Young’s modulus o ν = 0.3 - [nu] Poisson’s ratio o σ0 = 0.206 GPa [a] Yield Stress o K = 0.450 GPa [b] Hardening Parameter o n = 0.5 - [n] Hardening Exponent o σmax = 0.0 GPa Maximum Stress

• Files need to complete this exercise: Filename: boxtube.nas



Step 1: Load the model.

1. Launch Hypermesh.

2. Go to Preferences menu, and select User Profiles….

3. Toggle Nastran and click OK.

4. From the File pull-down menu, select Import….

5. Under File selection, for File, browse the file boxtube.nas.

6. Click Import. 7. Click Close.

Step 2: Convert Nastran deck to RADIOSS. 1. From the main menu, go to the Tool page and select the convert panel.

2. From the Preferences menu, select User Profiles…. 3. Toggle RADIOSS-Block51 and click OK.

4. From the main menu, go to the 2D page and select the elem types panel, 2D & 3D sub-panel.

5. Select the element types as shown in the following image.

6. Select elems >> all. 7. Click update.

Step 3: Update the definition and values for Mat1_1.

1. On the toolbar, click Materials ( ).

2. Go to the update sub-panel.

3. Click mats and select Mat1_1.

4. Click select. 5. Set card image = to M2_PLAS_JOHNS_ZERIL.

6. Click update/edit.



7. Input the values as shown in the following image.

8. Click return.

Step 4: Update definition and values for property PSHELL_1.

1. On the toolbar, click Properties ( ).

2. Toggle to the update sub-panel.

3. Click props and select PSHELL_1.

4. Click select. 5. Set card image = to P1_SHELL.

6. Click update/edit . 7. Input the values as shown in the following image.

8. Click return.

Step 5: Update a component with a material and property.

1. On the toolbar, click Components ( ) and go to the update sub-panel.

2. Click comps and select COMP_PSHELL_1.



3. Click select. 4. Set card image = to Part. 5. Set material = to MAT1_1.

6. Set property = to PSHELL_1.

7. Click update.

Step 6: Create a rigid body.

1. On the toolbar, click Components ( ) and go to the create sub-panel.

2. For name= enter Rigids.

3. Switch card image = to no card image.

4. Click create. 5. Click return to go back to the main menu.

6. From the main menu, go to the 1D page and in the elem types panel, ensure that rigid configuration is set to RBODY type.

7. Click return to go back to the 1D page.

8. Click the rigids panel.

9. For nodes 2-n:, click the switch button and select multiple nodes.

10. For primary node click the switch button and select calculate node. 11. In the graphic area, select nodes as in the following image



12. Click create.

13. Click return to exit the panel.

Step 7: Create entity sets for a boundary condition. 1. From the main menu, go to the Analysis page and select the entity sets panel.

2. For name =, enter Boundary.

3. Set card image = to GRNOD.

4. Select the node as shown in the following image.

5. Click create. 6. As described in step 7.1 – 7.4, create an entity set with name Symmetry and card image

GRNOD and select the nodes as shown in the following figure.



7. Click create.

Step 8: Create boundary conditions.

1. Click Load Collectors ( ).

2. For loadcol name =, enter RBody.

3. Set card image = to BCS_Collector. 4. Click create/edit.

5. Click Grnod_id and select the entity set Boundary.

6. Fix Translation_Vx, Translation_Vy, Rotation_Wx, Rotation_Wy, and Rotation_Wz by toggling the check boxes next to each BC as shown in the following image.

7. Click return.

8. In the loadcol = field, enter Symmetry.

9. Set card image = to BCS_Collector. 10. Click create/edit. 11. Click Grnod_id and select the entity set Symmetry. 12. Fix Translation_Vx, Rotation_Wy, and Rotation_Wz by toggling the check

boxes next to each BC as shown in the following figure.



13. Click return twice to exit the panel.

Step 9: Create imposed velocity. Define load function:

1. From the main menu, go to the Post page and select XY plots and click the plots panel.

2. For plot =, enter load as shown in the following image.

3. Click create plot. 4. Click return.

5. Go to the edit curves panel.

6. Toggle math.

7. Enter the values as shown in the following image.

8. Click create.

A curve is now created and displayed in the graphic area. This curve is used to give imposed velocity to the master node of the rigid body.

9. Click return.



10. Click exit to return to the main menu.

11. Go to the Analysis page and select the entity sets panel.

12. For name =, enter velocity.

13. Set card image = to GRNOD

14. Select the master node of the rigid body as shown in the following image.

15. Click create.

16. Click Load Collectors ( ).

17. For loadcol name =, enter Velocity.

18. Set card image = to IMPVEL _Collector (use to scroll to the selection).

19. Click create/edit.

20. Click Grnod_id and select the entity set Velocity.

21. Set DIR to Z.

22. Set Scale_y to -1.

23. Click lfunct and select Curve1, the curve you created for imposed velocity.

24. All fields should be as shown in the following image.




Step 10: Create a rigid wall. 1. From the main menu, go to the Geom page and click nodes, or else press the F8 key.

You will create a base node for the rigid wall. A small gap is recommended between the mesh and the rigid wall.

2. Enter the coordinates as shown in the following image.

3. Click create node.

4. Click return.

5. From the main menu, go to the Analysis page and click on rigid walls panel, go to create sub-panel.

6. For name =, enter Rigid_Wall.

7. Set size = to 10.

8. Set type = to RWALL.

9. Set card image = to RWALL.

10. Click create.

11. Go to the geom sub-panel.

12. Click on base node and select the node created on step 10.2.

13. Set shape: to infinite plane,

14. For normal vector, switch to components.

15. For Z comp =, enter 1.

16. Click update.



17. Go to add sub-panel.

18. For slaves:, switch to nodes.

19. Click nodes >> by window and select the nodes shown in the following image.



20. Click select entities.

21. Click add.

22. Go to the card sub-panel.

23. Click edit to edit the card.

24. Select [fric] and enter 0.200.


Step 11: Create a self contact. 1. From the main menu, go to the Analysis page and select the interfaces panel.

2. For name =, enter Contact. 3. Set type = to TYPE 7.

4. Set card image = to TYPE 7.

5. Click create.

6. Go to the add sub-panel.

7. For master:, switch to comps in the drop down menu.

8. Click the comps entity selector and select the component COMP_PSHELL_1.

9. Click select. 10. Click update.

11. For slave:, switch to comps.

12. Click comps and select the component COMP_PSHELL_1.

13. Click select. 14. Click update.

15. Click review to review the interface.



16. Go to the card image sub-panel.

ing:

GAPmin = 0.900

17. Click edit. 18. Enter the follow

STFAC = 1 FRIC = 0.200


ngine File Tool, in the GENERAL tab, enter values as shown in the following image.

Step 12: Create an Engine file (0001.rad). 1. In the Utility browser, click RADIOSS Tools and then click Engine File.

2. In the Radioss E



3. Click the ANIM tab and enter values as shown in the following image.

5. Click Close.

t the model, write Starter (_0000.rad) and Engine files

, click Export (

4. Click Apply.

Step 13: Expor(_0001.rad).

1. On the Standard toolbar at the top of the window ).

2. Check options as shown in the following image.



3. Under File type:, click the file folder icon and navigate to the destination directory.

4. Enter the filename as TUBE and click Save.

Click Export. 5. Click Close.

Step 14: Open RADIOSS Manager from windows Start menu

Step 15: Run the model TUBE_0000.rad using RADIOSS Manager on the class_exercise folder with the option: –both

Step 16: Review the listing files for this run and verify on the results: 1. See if there is any warning or errors on .out files

2. Using HyperView plot the displacement and strain contour and vectors



EXERCISE EXPECTED RESULTS

Total Displacement Contour (mm)

Von Mises Stress Contour



Documents

Radioss Impact 1day