Realistic Simulation of a Flexible Mechanism Using ABAQUS/Simulia

Copyright 2007 Dassault Systèmes

Realistic Simulation of a Flexible Mechanism

Dale BerrySIMULIA

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• Dassault Systèmes brand for delivering Realistic Simulation software

• ~7000 DS employees worldwide

• Headquarters in Providence RI• Staff from DS simulation group in

France, now part of SIMULIA• Over 550 people, more than 430

technical staff

• Worldwide presence – 28 offices and 9 representatives

• Focused on Abaqus FEA, Multiphysics, and SLM product lines

SIMULIA

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SIMULIA Analysis Highlights

• Analysis engine• Abaqus FEA

• Powerful analysis engine – the flagship of SIMULIA simulation

• Interactive simulation products• CATIA V5 FEA Simulation

• Routine analysis tools for CATIA V5 designers

• Abaqus for CATIA V5• Focused & proven Abaqus workflows

for CATIA V5 engineers• CATIA V5-embedded solution

• Abaqus/CAE• Full featured pre and postprocessing

environment for FE experts/analysts• CATIA V5 associative import

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Static Load Case Modeling

• Abaqus for CATIA (AFC) was used for the static load cases

• Native CATIA V5 geometry

• Straightforward static load modeling requirements

• Geometric changes required for design iteration

• Easy to achieve when defining analysis model directly on CAD geometry

• Analysis model can subsequently be exported if additional modeling is desired in standalone Abaqus FEA products

• No model re-creation is required

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Modeling preliminaries

• Hide components not relevant to static simulation objectives

• Publications to define geometrical entities reused for definition of BC, interactions and connections

• Allows automatic updating when replacing components in the model

• Meshing was performed using CATIA tools for tetrahedral unstructured meshing

• Most commonly used Abaqus analysis features are available in AFC, including material definitions and non-linear geometric modeling

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Contact modeling

• Connections between parts can be modeled either using deformablecontact, rigid contact, or as an idealized connector component

• If the stress state depends strongly on the nature of contact where parts interact, connectors should be used with caution

• For this exercise, both approaches were used. The final resultspresented are for the case of full contact modeling

Connectors for part interaction Full contact with pins

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Static Load Case Application

• Loads for braking and turning were applied directly to the CATIA geometry

• Loads and boundary conditions are associative to the CAD geometry

• If design changes are made (strut lengths, cylinder diameters, hole sizes, etc.) the model updates automatically

• No tire model was required for the static load cases, however spring and dashpot elements can easily be added if necessary

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Results and model iteration

• Static stress results – initial model

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Results and model iteration

• Geometry modification• Modification of the fillet radius between lug and outer cylinder to avoid

stress concentration

• Analysis model is fully associative with the geometry – updates automatically upon geometry changes

Initial design Iteration 1 Iteration 2

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Drop Test Simulation Objective

• Pre-processing and model set-up• Associative import with CATIA was used (new in V6.7)

• This capability allows a CATIA assembly to be read directly intoAbaqus/CAE without the need for geometry translation

• The import is associative, meaning all part names, sets, colors, etc. are maintained in the imported representation

• Subsequent changes to the CATIA geometry are sent to Abaqus/CAE with a single mouse click, and all defined loads, boundary conditions, partitions, etc. are maintained

• The complete meshing capabilities in Abaqus/CAE allowed the entire assembly to be modeled in approximately 1 hour

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Substructures

• Substructures were used for model reduction to allow fast turnaround time yet still obtain accurate results

• Commonly referred to as superelements in FEA literature

• The substructures in Abaqus/Standard allow for large rotations and translations of the substructure at the usage level

• Model a complex structure with only retained degrees of freedom

• Large rotations and displacements can still be considered in thesolution

• Stresses are recoverable within substructures to obtain dynamic results

• Substructures in Abaqus can be used to provide boundary conditions to submodels of high stress areas such as attachment locations and areas with high stress gradients

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Abaqus/CAE Analysis Process

• Other details• Structure was given an initial drop velocity of 120 in/sec

• Air spring damping curve was defined as piecewise linear

• How this curve was arrived at will be discussed momentarily

• Connectors in Abaqus/CAE are essentially the equivalent of virtual parts in AFC

• Connectors representing the tires were given mass and rotational inertia

• Connectors were used in place of pins to model the interfaces of various parts

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Abaqus/CAE Analysis Process

• Tire modeling• Due to the focus on minimum solution time, a discrete tire model was

not used. However, Abaqus has significant tire modeling capabilities• A complete suite of tools for modeling hyperelastic and other nearly

incompressible materials

• A coupled Eulerian-Lagrangian solution capability to be released in V6.7EF allows prediction of hydroplaning on wet runways

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Damping Curve Definition

• Damping curve definition process• The reaction force will be the summation of stiffness and damping

contributions of the system

• With a little guesswork regarding the velocity of compression, we can estimate the required damping as c = ΔF / v

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Damping Curve Definition

• Damping curve definition process• The value of using substructures allows either a manually iterative

process (used here) or integrating the process into an optimization routine

• The final damping curve developed for this exercise is as follows:

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Drop Simulation Results

• Damping curve definition process• This damping distribution leads to a dynamic load curve of the following

form:

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Drop Simulation Results

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Optimization with Abaqus

• SIMULIA maintains strong relationships with several partners who provide leading edge optimization technology

• OPTIMUS• HyperStudy, OptiStruct• iSIGHT• modeFRONTIER• TOSCA• VisualDOC• HEEDS

• Both the static load simulation results from AFC, as well as the stress results from the substructure model, can be used to drive an optimization study

• With the associative geometry in either CATIA or Abaqus/CAE, parametric and topological optimization processes are straightforward to define

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Summary

• SIMULIA provides many tools for performing simulations of complex physical systems

• AFC runs within CATIA and has tools for static, dynamic and kinematic analyses

• Abaqus/CAE can associatively import CATIA geometry and perform repair operations if required

• Modifications to part design (for example adding fillets to lugs) can be easily handled in either AFC or Abaqus/CAE

• Substructures and connectors allow complex models to be solved efficiently and accurately

• SIMULIA works with many partners to extend realistic simulation and provide leading edge modeling capabilities

Realistic Simulation of a Flexible Mechanism Using ABAQUS/Simulia

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