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 into.
Realistic Simulation of a Flexible Mechanism
Dale Berry SIMULIA
Copyright 2007 Dassault Systèmes
SIMULIA • 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
Copyright 2007 Dassault Systèmes
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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 Copyright 2007 Dassault Systèmes
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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 deformable contact, 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 results presented are for the case of full contact modeling Connectors for part interaction
Copyright 2007 Dassault Systèmes
Full contact with pins
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 Copyright 2007 Dassault Systèmes
Iteration 1
Iteration 2
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 into Abaqus/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
Copyright 2007 Dassault Systèmes
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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 the solution • 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
Copyright 2007 Dassault Systèmes
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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
Copyright 2007 Dassault Systèmes
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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
Copyright 2007 Dassault Systèmes
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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
Copyright 2007 Dassault Systèmes
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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:
Copyright 2007 Dassault Systèmes
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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
Copyright 2007 Dassault Systèmes
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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 Copyright 2007 Dassault Systèmes
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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
Copyright 2007 Dassault Systèmes
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