Advanced Simulation of SealingsCADFEM GmbH

Rainer Rauch

- 1 -

Recent developments in ANSYS V12 for the simulation of sealings

Element technology

Material models

Contact

Robust design and optimization

- 2 -

New Element: 4 Node Tetrahedron: SOLID285

Motivation for 4-node tetrahedral elementsCurrent mesh generators produce triangular and tetrahedral elements reliablyCan be used to mesh very complex geometrical shapesElement is less sensitive to distortion Element is vital to rezoning and large deformation problems such as metal-forming

Drawbacks with 4-node tetrahedral elementsStandard displacement element is hopelessly locked by the incompressibilityMixed displacement and pressure u/P formulation improves slightly the volumetric locking, however

Stability is of utmost concern of mixed u/P formulation

- 3 -

SOLID285: Stabilized Mixed u/P Formulation

DisplacementsHydrostatic pressure (HDSP)

Interpolation functionsLinear functions for both displacements and pressures

Added to satisfy LBB conditionIntroduced with enhanced strain methodCondensed out at element level

DOF: HDSPA new DOF in ANSYSIts energy-conjugate partner: DVOL volume changeConvergence check for both is controlled by CNVTOL

ezyx uuu ),,(

),,,( puuu zyx

),,,( puuu zyx

ez )

1

2

3

4

),,,( puuu zyx

),,,( puuu zyx

DOFsInternal

- 4 -

New Element Solid285

Poisson Ratio Theory

Mixed u/p enhanced

Tetra Error (%) Mixed u/p Error(%)

Pure Displace

mentError (%)

0.0000 3.7500 3.7275 0.5994 3.7274 0.6015 3.7235 0.70580.2500 4.4531 4.4242 0.6489 4.4237 0.6594 4.4124 0.91340.3000 4.5825 4.5520 0.6642 4.5513 0.6805 4.5365 1.00290.4900 5.0399 5.0008 0.7747 4.9701 1.3841 4.7941 4.87600.4990 5.0602 5.0204 0.7850 4.8935 3.2927 3.7532 25.82780.4999 5.0623 5.0224 0.7876 4.6940 7.2738 1.1884 76.5242

SOLID285 Regular u/P

1

2

3

4

ezyx uuu ),,(

),,,( puuu zyx

),,,( puuu zyx

4

ez ) ),,,( puuu zyx

),,,( puuu zyx

DOFsInternal

Expansion of a Thick walled cylinder under internal pressureUnstructured mesh with 10 divisions in thickness directionsCompare SOLID285 (Enhanced Tetra), regular mixed u/P and pure displacement formulations

Radial stress for v=0.4999 Analytical solutions: inner radius =-1, outer radius =0

- 5 -

Tension Bending Torsion Shear

Accuracy

Tension Bending Torsion Shear

Efficiency Tension Bending Torsion Shear

Robustness

Solid186Solid285

- 6 -

0.00

6000.00

0.00 15.00Weg [mm]

Kra

ft [N

]

Messung:Berechnung mit Solid 285:

Computer xp64 - 2 CPUs, 3 GHzMeshing- 3 Min.Analysis- 50 min.

- 7 -

Import Mesh Regenerate Geometry Parameterize Geometry

- 8

Linear Tets

SOLID285

SOLID187

- 9 -

Recent developments in ANSYS V12 for the simulation of sealings

Element technology

Contact

Robust design and optimization

- 10

New Formulations: Bergström-Boyce

Bergström-Boyce (TB, BB) polymer viscoelasticity for current element technologies

Elements: SOLID 185, 186, 187; SOLSH190; SHELL 208, 209, 281;

Features: pressure sensitive, combined with creep,Combinations: isotropic damage (Ogden-Drawback: no curve fitting available;

Benefits and ApplicationsTechnologies: filled/unfilled elastomers; biocompatible devices; artificial tissues.Robustness: experimentally validated; Physicality accounted: rate-dependence; hysteresis; symmetric stress relaxation; (mild) Mullins effects.

- 11

New Formulations: Mullins efect

Modified Ogden-Roxburgh (TB, CDM) isotropic damage model for current element technologies

Elements: SOLID 185, 186, 187; SOLSH190; SHELL 208, 209, 281;

Features: isotropic cyclic softening in filled polymers (Mullins effect),Combinations: almost all nearly-, or fully incompressible isotropic hyperelasticity models Drawback: no curve fitting available; not applicable for foams.

Benefits and ApplicationsTechnologies: filled/unfilled elastomers; damage in biocompatible devices and artificial tissues.Robustness: validated; Physicality accounted: amplitude dependent damage softening.

- 12

Example: TB,CDM (Ogden-Roxburgh)Objective: simulation of the cyclic, high-pressure response of rubber sealing;

Specifics: Mullins effect and BC induced incompressibility;

Material models: neo-Hooke with Ogden-Roxburgh;

Element technology:

-PLANE182 (ESF).

Sealing

Steel cylinders

- 13

Mullins effect: amplitude dependent (tangent) stiffness reduction

-0,2

0

0,2

0,4

0,6

0,8

1

1,2

-0,05 0 0,05 0,1 0,15 0,2 0,25 0,3 0,35 0,4 0,45

Uniaxial strain measure

Nor

mal

ized

uni

axia

lstr

ess

mea

sure

0,0292

0,2

0,0458

0,2

- 14 -

Recent developments in ANSYS V12 for the simulation of sealings

Element technology

Material models

Contact

Robust design and optimization

- 15

Rigid contact in WorkbenchWB now supports all types of rigid contacts

Solid, Shells and 2D; w,w/o midside nodesBenefits and Applications

Highly efficient contact simulation together with the flexible definitions of joints and drivers

- 16

Fluid Pressure Penetration

Modeling fluid pressure penetration- Fluid penetrating two contact surfaces- 2D/3D surface-to-surface contact pair- Small and large sliding contact- Rigid-flexible and flexible-flexible contact- Pressure progresses with contact status

Benefits and Applications- Leakage Simulation- Easy to use with few commands- Makes complex macros obsolete

- 17 -

Recent developments in ANSYS V12 for the simulation of sealings

Element technology

Material models

Contact

Robust design and optimization

- 18 -

- 19 -

- 20 -

- 21 -

Workflow: Parameters and optimization

- 21

geometry

material properties

b.c. from any physics

Overview in the project page

- 22 -

Sensitivities how big is the influence of an Input parameter on an Output parameter?

Correlation matrix Which are the best parameters to control the model behaviour?

Define a goal and let Design Exploration optimize your model by searching on a response surface

Workflow: Parameters and optimization

- 23 -