Methodology and Tools for Virtual Prototyping: Finite...
Transcript of Methodology and Tools for Virtual Prototyping: Finite...
MSC Confidential
Methodology and Tools for Virtual Prototyping:
Finite Element Analysis (Structural, Thermal,
Mechanical, Coupled)
Nastran/Marc
Daniele Catelani
Senior Project Manager MSC Software
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FEM Structure representation
• Real behavior of structures is
extremely complex
• Mathematical Representation has
to take into account:
– Geometry
– Structure charachteristic
– Material
– Constraints
– Load
– Analysis to perform
– Output to get
– ...
• Some representation is needed to
allow study
?
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FINITE ELEMENTS
● A finite element model of a component or system is a
mathematical representation of it using small, but finite
sized, simply shaped, connected entities ( i.e. line, surface,
solid) called finite elements.
Component (Geometric Model) Tetrahedral Mesh of Geometry
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FINITE ELEMENTS
● Finite elements come in different shapes and forms
● Linear and parabolic elements
Bar Tri
Tet HexWedge
Quad
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• Displacement method
• Every subdomain is represented by stiffness matrix, depending on
element type and characteristic
• For each element the following equation is evaluated
{ P }e = [ k ]e { u }e
{ P }e = applied external forces
[ k ]e = element stiffness matrix, in which the term kij represents force on the j dof when i dof disp = 1.0 ( kij= kji )
{ u }e = disp vector of element nodes
• STRUCURE Σ{ P }e = Σ[ k ]e Σ{ u }e { P } = [ k ] { u }
FEM introduction
ASSEMBLY
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FEM introductionHow to choose the structural element
• Depending on geometry
– Geometrical dimension ratio
– 1D Lateral Dimensions are negligible wrt Longitudinal
– 2D two dimensions are greater
– 3D No dimension is greatest
Undeformed configuration
}
Modello realizzato con elementi tridimensionali
Solu
tio
n 1
Solu
tio
n 2
Analysis goal influences element choice
• 1D element; properties have to simulate right behavior
• Lumped mass for wheels
• Lumped mass for representing inertia distribution
Simplified model
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FEM introductionMaterial
• Elastic or non elastic
– Plastic deformation = residual deformation
– Temperature effects
– Deformation ratio effect
– Hardening effect
– …
e
s T2
T1
e2
e3
Superficie di
snervamento
iniziale
Superficie di snervamento
dopo la deformazione plastica
O
L’incremento di carico
aumenta le dimensioni
della superficie di
snervamento
e1
e2
e3
O
e1
O’
Superficie di
snervamento
iniziale
Superficie di snervamento
dopo la deformazione plastica
L’incremento di carico sposta la
superficie di snervamento senza
aumentarne le dimensioni
INCRUDIMENTO ISOTROPOINCRUDIMENTO CINEMATICO
e
s
e
t (time)
e0
t1
Creep Recovery
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• Elasto-Plastic : (MATEP)
• Temperature dependence : (MATORT), (MATTEMP)
• Failure : (MATF)
– ( Hill, Tsai-Hu, Hoffmann, Puck, Hashin, Hashin Tape and Fabric,...)
– Progressive failure analysis
• Gasket : Nonlinear elastic and elasto-plastic (MATG)
• Cohesive : (MCOHE)
• Orthotropic Nonlinear Elasticity
(MATORT/MATSORT)
• Anisotropic Plasticity (MATEP with ‘aniso’ option –
Hill and Barlat’s models)
FEM introductionMaterial library MSC Nastran
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• Pressure dependent plasticity (MATEP - Mohr-Coulomb and Drucker-Prager)
• Shape memory (MATSMA)
• Other: (MATEP ,MATVE,MATVP)
• Creep (MATVP - Maxwell and Kevin models)
• Elastomers (MATHE - Mooney, Ogden, Arruda-Boyce
and Gent models)
SOL 400 Nonlinear Material Implementation Marc material models in the standard Nastran elements (Cont.)
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Tipi di carichi Schede di input MD NASTRAN Forze applicate direttamente ai nodi Momenti applicati direttamente ai nodi
FORCE, FORCE1, FORCE2 MOMENT, MOMENT1, MOMENT2
Carichi sugli elementi 1D Carichi di pressione e trazione su elementi 2D e 3D
PLOAD1 PLOAD, PLOAD2, PLOAD4, PLOADX
Carichi di accelerazione traslazionale (Gravità,..) Carichi derivanti da diversi campi di accelerazione Carichi dovuti a force centripete e/o accelerazioni angolari
GRAV ACCEL, ACCEL1 RFORCE
Carichi termici TEMP, TEMPD, TEMPP1, TEMPRB (+ Coefficiente di espansione termica)
Deformazioni assiali su elementi 1D DEFORM
Spostamenti imposti ai nodi (cedimenti vincolari..) SPC, SPCD
Combinazione lineare dei carichi LOAD
FEM introductionLoads /Constraints/Contacts
Touching Contact Permanent- Glue Contact
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• Linear Static
• Modal
• Buckling
• Frequency response
• Transient response
FEM analysis
MODAL ANALYSIS
Detailed FEM
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FEM analysis
• Damped modes
• Random
• Response Shock Spectrum
• Aeroelasticity (Static, Flutter, Transient)
• Nonlinear Static
• Nonlinear transient
• Strucural optimization (Properties, Material, Shape, Topology, Topometry, Topography)
• Superelements
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WORKFLOW IN Patran
● The Main Menu
2 - Import Geometry
1 - Select Analysis Code
2 - or Build
Geometry3 – Create
Analysis Model
5 - Evaluate and Publish
Analysis Results
4 - Perform the
Analysis
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