Transcript 5.7 New Features - Slovak University of Technology in

3.3 Element Technology
Overview:
A. Beam Enhancements
1. Cross-Section Mesh Refinement
2. Built-Up Sections
3. Plasticity
B. Mixed U-P Formulations
C. Pressure Load Stiffness
NEW FEATURES 5.7
• In this chapter, we will present a brief overview to
the following topics:
D. 20-Noded Layered Solid
E. Initial Stress
Training Manual 001419
15 Aug 2000
3.3-1
Element Technology
A. Beam Enhancements
• Cross-Section Enhancements
– No hard limits on section size (number of section cells)
– Cross-section mesh refinement
• Needed for accurate shear correction factors & direct shear
stress calculations
– Built-up (multi-material) cross-sections
– Applications:
NEW FEATURES 5.7
– Shear center, warping rigidity and shear correction factors
are calculated for all sections, including user mesh
• sandwich beams
• airfoils
• MEMS
• reinforced beams
Training Manual 001419
15 Aug 2000
3.3-2
Element Technology
… Beam Enhancements
• Transformed section method is used for multimaterial cross sections
• Extensive material library
– Orthotropic elasticity, BISO, MISO, BKIN, MKIN, KINH,
NLISO, Creep, Chaboche, Rate Dependent plasticity, User
material
• Initial Stresses supported for built-up beams
NEW FEATURES 5.7
• Sparse solver used for efficient section solution
– assign initial stress based on the cell material number
• 3D post processing (/ESHAPE, /EFACET)
– visualization of direct shear stress
Training Manual 001419
15 Aug 2000
3.3-3
Element Technology
… Beam Enhancements
• Cross-Section Mesh Refinement
– Available for common and custom sections
• Refine by picking elements (EREFINE)
NEW FEATURES 5.7
• Refine with slider bar
Training Manual 001419
15 Aug 2000
3.3-4
Element Technology
… Beam Enhancements
• Built-Up Sections for BEAM188 and BEAM189
– Available for common and custom sections
NEW FEATURES 5.7
– Ability to specify a cross-section made up of different
materials (EMODIF)
Training Manual 001419
15 Aug 2000
3.3-5
Element Technology
… Beam Enhancements
• Plasticity for BEAM188 and BEAM189
• Axial and the torsional shear stress components behave
independently
• As a result of this approximation, the equivalent stress output
by PRSSOL may at times exceed yield stress and yet no active
yielding is reported
– At revision 5.7, the actual state of stress within the beam is
used to perform the plasticity calculation
NEW FEATURES 5.7
– At revision 5.6, the treatment of material nonlinearities at
the section points is based on uncoupled behavior
between the stress components
• The new formulation will release the restriction on the beam
elements of handling complete state of stress in plasticity and
will provide more realistic state of stress in the beam elements
Training Manual 001419
15 Aug 2000
3.3-6
Element Technology
B. Mixed U-P Formulations
• Mixed U-P formulation option added to elements:
PLANE182, PLANE183, SOLID185, SOLID186, SOLID187
• Applications
– hyper-elastic materials (typically fully incompressible)
– elasto-plastic materials undergoing large plastic strains
– linear elastic materials with Poisson’s ratio > 0.4999
• Advantage - better convergence and more robust
NEW FEATURES 5.7
– Includes hydrostatic pressure as an independent DOF
• Disadvantages
– Additional DOF’s (longer solution time per equilibrium iteration)
– Does not support modal and buckling analyses
Training Manual 001419
15 Aug 2000
3.3-7
Element Technology
… Mixed U-P Formulations
• Activation
– keyopt(6) = 0, regular formulation (default)
• The solver (EQSLV command) must be either the frontal solver
(default) or the sparse solver - (frontal is recommended)
• Internal nodes used for pressure DOF’s
– Created automatically
– Not accessible by user
NEW FEATURES 5.7
– keyopt(6) = 1 (or 2 for SOLID187), mixed U-P formulation
*** NOTE ***
CP=
54.625
TIME= 14:28:22
Internal nodes from 2360 to 3831 are created.
1472 internal nodes are used for 18x elements with mixed formulation.
Training Manual 001419
15 Aug 2000
3.3-8
Element Technology
… Mixed U-P Formulations
• The examples below were solved with mixed U-P
formulations
NEW FEATURES 5.7
Inflation of a
hyperelastic membrane
Inflation and pinch flat of
a bicycle tire
Training Manual 001419
15 Aug 2000
3.3-9
Element Technology
C. Pressure Load Stiffness
• Pressure load stiffness option added to elements:
PLANE2, PLANE42, SOLID45, SOLID46, SOLID64, SOLID65, PLANE82, VISCO88, VISCO89,
SOLID92, SOLID95, SURF153, PLANE182, PLANE183, SOLID185, SOLID186, SOLID187
– Improved convergence for large deflection analyses
– Improved accuracy for linear buckling analyses
• New options on existing commands:
– Pressure load stiffness controlled by a new field (Key3) on
the SOLCONTROL command
NEW FEATURES 5.7
• Benefits models with element pressure loads
– Unsymmetric stiffness matrix controlled by a new Option on
the NROPT command
Training Manual 001419
15 Aug 2000
3.3-10
Element Technology
… Pressure Load Stiffness
• SOLCONTROL, Key1, Key2, Key3
– Key3 = NOPL
– Key3 = no entry (default)
• Include pressure load stiffness for elements SURF153, SURF154, SHELL181,
PLANE182, PLANE183, SOLID185, SOLID186, SOLID187, BEAM188, and BEAM189
• Do not include pressure load stiffness for elements PLANE2, PLANE42,
SOLID45, SOLID46, SOLID64, SOLID65, PLANE82, VISCO88, VISCO89, SOLID92, SOLID95, and SOLID191
– Key3 = INCP
• Include pressure load stiffness for elements PLANE2, PLANE42, SOLID45,
NEW FEATURES 5.7
• Do not include pressure load stiffness for any elements
SOLID46, SOLID64, SOLID65, PLANE82, VISCO88, VISCO89, SOLID92, SOLID95, SURF153, SURF154, SHELL181,
PLANE182, PLANE183, SOLID185, SOLID186, SOLID187 BEAM188, BEAM189, and SOLID191
Training Manual 001419
15 Aug 2000
3.3-11
Element Technology
… Pressure Load Stiffness
• NROPT, Option, --, Adptky
– Option = UNSYM
– If an unsymmetric matrix is needed for pressure load
stiffness effects, use NROPT,UNSYM
– For analyses involving friction, using NROPT,UNSYM is
useful (and, in fact, sometimes required) for problems
where the normal and tangential (sliding) motions are
strongly coupled, such as in a wedge insertion problem
NEW FEATURES 5.7
• Use full Newton-Raphson with unsymmetric matrices of
elements where the unsymmetric option exists
– You should first try NROPT,FULL; then try NROPT,UNSYM if
you experience convergence difficulties
Training Manual 001419
15 Aug 2000
3.3-12
Element Technology
D. 20-Noded Layered Solid
• New element: SOLID191 3D 20-Noded Layered Structural Solid
– Enhances element library for composites
• stable, fully integrated
– Uses SOLID95 displacement shapes
• Better accuracy for curved boundaries
– Input similar to SOLID46
– Includes stress stiffening capability
– Does not support nonlinear materials or large deflections
NEW FEATURES 5.7
– Uses SHELL91 data structure
Training Manual 001419
15 Aug 2000
3.3-13
Element Technology
E. Initial Stress
• Enhancements made to Initial Stress loading
– New commands
– Defines a set of initial stress values
• ISWRITE
– Determines whether an initial stress file is written (or not)
– New options
• Ability to apply initial stresses only to specified materials
– Existing command
NEW FEATURES 5.7
• ISTRESS
• ISFILE
– Reads an initial stress state from a file into ANSYS
– Lists initial stresses
– Deletes initial stresses
Training Manual 001419
15 Aug 2000
3.3-14