3.2 Material Models
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Training Manual 00141915 Aug 2000
3.2-1
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.73.2 Material Models
• Material enhancements in ANSYS 5.7 include:
A. Material Definition GUI
B. Hyperelasticity
C. Metal Plasticity
D. Viscoplasticity
E. User Material Subroutine for 18x Elements
![Page 2: 3.2 Material Models](https://reader036.fdocuments.us/reader036/viewer/2022062321/56813065550346895d963cea/html5/thumbnails/2.jpg)
Training Manual 00141915 Aug 2000
3.2-2
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.7Material Models
A. Material Definition GUI
• New GUI for material model definition
– Applicable to all linear and nonlinear materials (except ANSYS/LS-DYNA and FLOTRAN fluids)
– Logical tree structure sorted by discipline and behavior
– Associates all properties (MP’s and TB’s) for a material model, which is treated as a single entity
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Training Manual 00141915 Aug 2000
3.2-3
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.7Material Models
… Material Definition GUI
• Definition and editing of models
– Intuitive definition of complex relationships (combination models)
– Dynamic interface, e.g., {stress vs. strain} vs. temperature
• Provides a framework for future expansion
– Experimental data input
– Support for external material database (XML, proprietary…)
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Training Manual 00141915 Aug 2000
3.2-4
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.7Material Models
… Material Definition GUI
All models in database
All available materials grouped by discipline
• Models and disciplines
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Training Manual 00141915 Aug 2000
3.2-5
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.7Material Models
… Material Definition GUI
Expanded folder shows material model contents
Materials are grouped by behavior
• Subgroupings
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Training Manual 00141915 Aug 2000
3.2-7
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.7Material Models
B. Hyperelasticity
Background:
• Existing (5.6) mixed U-P elements (56, 58, 74, 158) have limited application
– Assumed not incompressible
– Pressure is NOT a DOF (eliminated before solution)
– Penalty based formulation causes problems
– Input via• TB,MOONEY,mat,ntemp,npts
• Material property dialogs
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Training Manual 00141915 Aug 2000
3.2-8
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.7Material Models
… Hyperelasticity
New in ANSYS 5.7:
• Mixed U-P formulation added to all 18x family of elements (except beams which are naturally excluded).
– Poisson’s ratio of 0.5 allowed (incompressible)
– Compressible and incompressible parts are two separate formulations
– Lagrange multipliers for Pressure DOF
– Includes all relevant stress states
– Input via:• New TB,HYPER option*
• New material definition GUI
*TB,BOYCE has been moved to TB,HYPER
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Training Manual 00141915 Aug 2000
3.2-9
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.7Material Models
… Hyperelasticity
• New formulation also offers more hyperelastic material models:
– Mooney-Rivlin
– Ogden
– Neohookean
– Polynomial
– Arruda-Boyce
– User hyperelasticity
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Training Manual 00141915 Aug 2000
3.2-10
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.7Material Models
...Hyperelasticity
• Example: Axisymmetric plug using Ogden model
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Training Manual 00141915 Aug 2000
3.2-11
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.7Material Models
...Hyperelasticity
• Example: Cook membrane problem using Mooney material
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Training Manual 00141915 Aug 2000
3.2-12
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.7Material Models
C. Metal Plasticity
• ANSYS 5.7 represents a significant change in the philosophy of material implementation: Keep material behavior separate from element technology.
– Allows complex behavior to be simulated by combining simple behaviors
– Easier to maintain existing material models and add new ones
• New plasticity model: Hill type anisotropy
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Training Manual 00141915 Aug 2000
3.2-13
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.7Material Models
...Metal Plasticity
Hill type Anisotropy
• Must be combined with another form of plasticity such as bilinear isotropic hardening
• 6 input constants define the ratio of the yield value in each orthogonal direction to that specified on the hardening model.
• Elastic portion of model may be isotropic or orthotropic
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Training Manual 00141915 Aug 2000
3.2-14
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.7Material Models
...Metal Plasticity
• Example - uniformly loaded stainless steel plate with constant pressure
BISO only BISO with Hill anisotropy
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Training Manual 00141915 Aug 2000
3.2-15
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.7Material Models
… Metal Plasticity
• Plasticity options available in 5.7:
– Isotropic hardening laws
– Kinematic hardening laws
– Anisotropic plasticity
– Viscoplasticity
– User material
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Training Manual 00141915 Aug 2000
3.2-16
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.7Material Models
D. Viscoplasticity
• Types of viscoplasticity in ANSYS 5.7:
– Creep• Implicit Creep
• Explicit Creep
• usercreep for implicit and usercr for explicit
– TB,ANAND for 106, 107 and 108 only
– TB,RATE for 18x elements• Peryzna
• Peirce
– User Material for 18x elements
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Training Manual 00141915 Aug 2000
3.2-17
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.7Material Models
… Viscoplasticity
• BISO only
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Training Manual 00141915 Aug 2000
3.2-18
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.7Material Models
… Viscoplasticity
• BISO plus Perzyna
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Training Manual 00141915 Aug 2000
3.2-19
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.7Material Models
… Viscoplasticity
• BISO plus Peirce
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Training Manual 00141915 Aug 2000
3.2-20
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.7Material Models
E. User Material
• Why User Material?
– Not all materials can be included• some material behavior proprietary
• need to apply limited resources to general behavior
– Gives users the ability to create custom material behavior
• Subroutine usermat*, which was beta at 5.6, is now released.
– Note: Some differences exist between beta and released versions. 5.6 users should re-create user material at 5.7.
*Not to be confused with USERPL, USERCR, etc
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Training Manual 00141915 Aug 2000
3.2-21
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.7Material Models
… User Material
• Subroutine usermat
– For 18x elements only, i.e, only structural analyses at the present time
– User must specify both linear and nonlinear properties
– Requires relink of ANSYS (use ANSCUSTOM script)
– Demonstration routine includes BISO plasticity
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