R15.0 Structural Mechanics – Deep Dive

R15.0 Structural Mechanics –
Deep Dive
Harish Radhakrishnan
ANSYS Inc.
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March 12, 2014
Topics
Contacts
Mesh Adaptivity / Rezoning
Usability
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March 12, 2014
Contact Technology
Enhancements
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March 12, 2014
Bolt Thread Modeling
Complex geometric features in bolts threads
often result in undesired simplification
Frictionless, Frictional, Rough and NoSeparation
Both 2-d and 3-d models supported
Assumes small strain formulation
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March 12, 2014
True thread Virtual Thread
…Bolt Thread Modeling
Define thread parameters in contact details window
– Mean Pitch diameter
– Thread Pitch distance
– Thread angle
– Starting/ending orientation points
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March 12, 2014
…Bolt Thread Modeling
• With sufficient mesh refinement, stress profiles match very closely
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March 12, 2014
MADPL: Contact Surface Wear
Archard wear model: Simulates the progressive loss of material from the contact surface. Assumes rate of volume loss, ,due to wear is proportional to the contact surface pressure and relative sliding velocity at the contact surface. Wear is in direction opposite to contact element normal.
where:
= wear coefficient
= material hardness
= pressure exponent
= contact pressure
= the relative sliding velocity
= velocity exponent
Contact nodes are moved to new positions. Contact variables (for example, contact pressure) change. The underlying continuum elements also experience a loss in material (and volume), thus simulating the wear.
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… Contact Surface Wear
Defined by TB and TBDATA commands:
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Applicable to nonlinear contact only (frictional, frictionless and rough)
Asymmetric behavior recommended
Penalty based formulation recommended for convergence
Nodal detection necessary
© 2013 ANSYS, Inc.
March 12, 2014
… Contact Surface Wear
Brake Pad Model:
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MECHANICAL ‐ Compression Only support
• Compression only support boundary condition is implemented with a rigid‐flexible frictionless contact pair with defaults…
─ Augmented Lagrange formulation
─ FKN=1.0
─ No stiffness updating • Contact stiffness factor and stiffness updating are now exposed in details window for easier user adjustment.
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March 12, 2014
Mechanical – Trim Contact
“Trim Contact” automatically reduces the number of contact elements generated within each pair, thereby speeding up processer time. “Program Controlled” will typically turn Trim Contact ON for small and large deflection. However, no trimming is done for manually created pairs.
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March 12, 2014
Mesh Adaptivity
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Why Mesh Adaptivity ?
Fully Automatic Remeshing
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Innovation
2D
Automatic Criteria
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Contact
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Energy
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Desired Frequency
© 2013 ANSYS, Inc.
March 12, 2014
3D
SOLID285 split now
supported
Usability Improvements
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Import Mesh
You can use Mechanical as a standalone post‐processor.
• Combine External Model with Mechanical. • Use Mechanical Tools > Read Results Files
test‐1.cdb
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Model Assembly
Define transformations and re‐use data
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Model Assembly
Allows user to split then later re‐assemble model
Upper Sub‐Assembly
Original Assembly
Sub‐Assembly models can be worked on independently, and later assembled
Sub‐Assembly models are updated separately at project level
Shaft/Connector Sub‐Assembly
Lower Sub‐Assembly
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Model Assembly
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Combine pre‐existing models, meshes, and geometries
Update connections, define loads, solve in Mechanical
Define transformations and copies in the assembly R15 will only process Geometry, Mesh, Material, and Named selection from External Model. No Connections, results, etc. Model Assembly functionality as built into Workbench is purposely limited. The ACT Extension for Model Assembly can combine Contacts, etc. from individual files. +
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Node/Element Selection
Mesh pick mode
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Node Filter
Element Filter
Selection Information Window
Selection information including element id, type, corresponding body, and node list
User can control information
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Use with criterion based named selections
Several different choices for selection criteria including:
• ID
• Type (Hex20, Tet10, Quad4, etc)
• Location (local or global)
• Distance (from a coordinate system)
• Size (Volume for solids, Area for Shells/2D)
• Mesh Metric (Quality, Skewness, Jacobian, etc)
• Convert to/from nodes (NSLE, ESLN)
• From other Named Selections
(stacked selection)
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Use Named Selections of geometry to find attached nodes and elements
Grow layers of mesh using criterion based selections
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Path Location using Direct Node Selection
A user will now be able to select nodes to define the location of the start and end of a path object in Mechanical.
The user can preselect two nodes and insert a path object, or the user can select the nodes and apply to an existing path object. If the user selects more than one node, the location will be calculated at the centroid of the nodes.
The selection is not associative. The location is obtained, but the nodes are not stored.
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March 12, 2014
Thank you
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March 12, 2014

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