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SIMULIA UK RUM 2011 Tortworth Court, South Gloucestershire

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Session 2 – Modelling Techniques

Advanced Analysis Ltd, DAMT Ltd and TWI Ltd.

Tony Richards

Application Engineer

DS UK Ltd

18th October 2011

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Advanced Analysis Ltd Getting Bodies into Contact – The Despair and Joy.

(Richard J. Tyrrell)

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Advanced Analysis Ltd

“BACK to BASICS”

Contact Default contact discretization method in Abaqus Release

6.10 and above, is Surface to Surface contact. Used by both General Contact and Contact Pairs.

Choice between general contact and contact pairs is largely a trade-off

between defining the contact and analysis performance.

Robustness and accuracy of both methods are similar.

Advantages of Surface to Surface contact. Often improves the accuracy of contact stresses and produces a smoother

contour pattern.

Reduces likelihood of slave node snagging and master nodes penetrating

slave surface.

Much less sensitive to the choice of master and slave surfaces

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Advanced Analysis Ltd

Surface to Surface contact is the recommended method,

with the following option. Contact Property - Constraint enforcement method.

• Use Penalty with either Linear or Nonlinear contact stiffness.

• As Penalty is not a Kinematic constraint (No Over-Constraint

problems).

In *Step use the Unsymmetric Equation Solver Matrix Storage (unsymm=yes),

gives better convergence..

Node to Surface contact, some recommendations. In *Step use the Unsymmetric Equation Solver Matrix Storage (unsymm=yes),

when the model has 3D curved master surfaces, gives better convergence.

Slave surface should be the finer meshed surface.

If surfaces are of a similar mesh density, then the Slave surface should be the

softer material.

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Advanced Analysis Ltd

Contact Pair - Small Sliding

Formulation. Small relative sliding between surfaces (i.e.

Bolted surface).

Be warned, the contact is governed by

local contact planes/lines that are defined in

the initial configuration, at the start of the

analysis, and are not tracked or updated

throughout the analysis.

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Advanced Analysis Ltd Controls Contact Controls Automatic Tolerances parameter, recommended for contact chattering.

Solver controls Be careful if changing the solver controls, you may change your results.

Controls are intended for advanced users, in 99% of circumstances it is not

necessary to modify them. Use the defaults, they work.

Stabilization Automatic stabilization (*Static, Stabilize).

Contact stabilization (*Contact Controls, Stabilize).

• Consider reducing stabilization defaults, they can be a little aggressive.

Check Stabilization energy (History output ALLSD).

Recommendation is to ensure ALLSD is <5% of the ALLIE (Internal Energy)

for Static’s and ALLSD <5% of the ALLKE (Kinetic Energy) for Dynamic’s.

The lower ALLSD is, the better

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DAMT Ltd Abaqus Analysis of Aircraft Safety-Harness Buckle Assembly.

(R P Johnson)

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DAMT Ltd

Work in Progress As Bob’s Abaqus Analyses were not completed when the RUM paper was

submitted, I therefore, have little to offer in this presentation.

The one item noticed; Convergence issues in Preliminary analysis using

Abaqus release 6.9.

• Maybe some of Richard Tyrrell’s suggestion may help?

• Maybe trying a newer release of Abaqus, substantial on going product

development is producing improvements release by release.

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TWI Ltd Abaqus and Optimisation: The inverse Analysis

of a Nano-Indentation.

(Tyler London & Vitor Marques)

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TWI Ltd

Isight This type of problem would lend itself

to be optimised, very efficiently, using

SIMULIA’s Isight software.

Use of the Isight Data Matching

component to calculate difference in

area (Isight – Objective function).

Model and Material changes would

use the Isight Abaqus component.

Optimization algorithm, probably,

Isight’s NLPQL – ‘Non-linear Programming by Quadratic Lagrangian’ or other

similar gradient based algorithm, Isight has a large number of built-in

algorithms.

Abaqus analyses and Isight optimisation are handled automatically by Isight,

without any need for manual intervention.

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Thank You.