1 © 2013 ANSYS, Inc. May 27, 2014 ANSYS Confidential
Recent Developments in ANSYS/Structure
Yongyi Zhu
UGM, May 2014
2 © 2013 ANSYS, Inc. May 27, 2014 ANSYS Confidential
2014 UGMs Topics:
Recent Developments in Contact modeling
ANSYS HPC for Mechanical Applications
Modeling Layered Composites the Simple Way
Other Enhancements
3 © 2013 ANSYS, Inc. May 27, 2014 ANSYS Confidential
Spot Weld • Mesh independent
• Connect surfaces
Pretension + Pretorsion – Apply pre-loads for bolt-joint – Large rotation based
Technology Overview: Special modules
Brake Squeal Ansysis – Predict unstable modes
– Friction, Slip rate, Damping
– Lining wear effect
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Fluid penetration loading – Apply fluid pressure based on contact status – Path dependent
Technology Overview: Special modules
Bolt-Thread modeling – Do not need to mesh threads
– Contact normal is computed internally based on bolt-thread parameters
Debonding or Bonding • Delaminating
• Friction stir welding
Tool
Contact interface
Friction Stir welding
5 © 2013 ANSYS, Inc. May 27, 2014 ANSYS Confidential
Wear modeling – Wear contact surface due to pressure and friction – Contact nodes are physically moved
Technology Overview: Special modules
UPF for contact interactions – User’s own complex interactions
– Cohesive/adhesive, lubrication
Impact Constraint • It satisfies momentum and energy balance
• It predicts the duration of contact and the rebound velocities
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Surface Projection Based Contact
Contact integration is done on the overlapping area instead of whole contact element
• Higher order: Division of quadratic patches into linear sub-segments
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3D Patch test
Existing contact: Gauss point + Augmented Lagrange Does not pass the patch test
New projection based contact + Lagrange Multiplier Results in constant VM stress Passes the patch test
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Stress Analysis of a C-Channel
Hot Side Convection T = 2400 F h = 50 BTU/(in-hr-F) Cold Side Convection T=1800 F h = 16.67 BTU/(in-hr-F) E = 37e6 psi CTE = 2.3e-6 in/in/F K = 1.167 BTU/(in-hr-F) Elements: Solid 70 Contact Conductance: 145000
Bonded contact Between each two layers
Cylindrical Smoothing is defined
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Stress Analysis of a C-Channel
Temperature Existing surf-surf contact
Temperature New projection based contact
Pressure Existing surf-surf contact
Pressure New projection based contact
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MADPL: Contact Surface Wear
where:
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Contact Surface Wear Contact Pressure Before Wear Contact Pressure After Wear
Wear Wear Pressure Pressure
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• User-Define Contact Interactions (USERINTER.F) – Includes interaction in the normal direction, interaction in the tangential direction,
and interaction among coupled multiphysics fields.
– User defined damping can be used for complex modal, harmonic (frequency domain), and transient (time domain) analysis.
• User-Define Friction (USERFRIC.F) Enhancement
• Defining Real Constants via a User Subroutine (USERCNPROP.F) – The Real constants can vary with pressure, penetration, temperature, and your own
defined state variables.
– Time or frequency (harmonic analysis)
• Defining Real Constants in Tabular Format
• Defining friction coefficient in Tabular Format
User Programming Features
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• In a lubricated contact problem the two flexible solid surfaces induces a motion in a fluid phase between them, which in turn generates traction that act to deform the solid surfaces.
• The fluid phase is assumed to be governed by the classical ReyNolds equation.
UPF Application: Lubricated Contact
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UPF Application: Lubricated Contact
Contact gap
Contact pressure
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Bolt Pretension & Pretorque
• Supports Large rotation based pretension and pretorque loads
• Supports locking in subsequent loadsteps
• The preloaded Bolt needs to be sliced in advance of analysis.
• The two cut surfaces are connected by a cylinder joint or a scew joint.
• The pretension loading is applied via Joint load (FJ,,FZ)
• The pretorque loading is applied via Joint Load (FJ,,MZ)
• The loading can be locked via DJ,,UZ,%_FIX% and DJ,,ROTZ,%FIX%
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• ‘Increment’ - applies user defined offset as an incremental sequential adjustment for challenging bolted assemblies
─ Value gets added to the solved deformation from the previous step
─ Is ramped on from previous step
─ Can follow ‘Load’, ‘Adjustment’ or ‘Open’ after LS1
─ Can be applied multiple times in sequence
Bolt Pretension Incremental load
– Supports Restarts
• If a solution restart is performed from a substep of a load step including an ‘Increment’, the increment value gets added to the solved deformation value at the beginning of the selected restart sub-step.
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Bolt Pretension & Pretorque • Screw joint is created in Workbench with a cylindrical joint
• A command snippet under the joint allows to express translation of the screw as a function of the rotation
Cylindrical joint
Type screw joint
Thread step size
• Defined a relation between Z axis displacement and rotation around Z : Uz = pitch * RotZ
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• You can easily apply a moment a torque or a rotation to the joint by sliding it to Setup
Bolt Pretension & Pretorque
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Bolt Pretension & Pretorque
• Screw joint produces some interesting results in terms of contact
Frictional Stress under Bolt Head
Frictional Stress between the two bolted bodies
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Using a cylinder/screw joint the stress appear without significant bending
Using conventional bolt pretension, the stresses appear with significant bending with rotation
Bolt Pretension & Pretorque
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• Produce the bolt thread stress profile without meshing the threads
─ Contact Normals computed internally based on user defined bolt thread parameters.
─ Supports 3D and 2D(MAPDL only) axisymmetric models
─ Frictional, Frictionless, Rough and No Separation
─ Applicable only for standard straight threads
─ Small strain formulation, small rotation
• Much easier to set up
• Improved run time efficiency
– In this test case:
• True thread model solves in 22167 sec.
• Virtual thread model solves in 9142 sec.
Geometry Correction: Bolt Thread Modeling
True thread Virtual Thread
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• Build conventional surface to surface asymmetric contact between cylindrical faces.
• Define thread parameters in contact details window
– In MAPDL, use SECTYPE and SECDATA commands
Bolt Thread Modeling
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• With sufficient mesh refinement, stress profiles match very closely
…Bolt Thread Modeling
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• Automatic Mesh splitting and morphing would allow for local topology correction so that problems become solvable
• Criteria based nonlinear adaptivity supports element distortion, mean strain energy and contact status
• Load Step and Part/Region specific rules can be defined
Mesh Nonlinear Adaptivity
Split Elements: 2->4
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Nonlinear adaptive meshing help solve large deformations models by splitting the mesh in sensitive areas
Nonlinear Adaptivity: 3D sealing of windows
• Challenges
– Complicated part shapes
– Need deformation details at corners
– Multiple load steps
• Approaches
– Different nonlinear adaptivity criteria at different load steps
– First load step: Location based criterion
– Second load step: Energy based criterion
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• Automatic Mesh splitting and morphing
• Criteria based nonlinear adaptivity
• Load Step and Part/Region specific rules
Nonlinear Adaptivity
Courtesy: Texas Iron Works Inc, Houston TX.
ANSYS solutions for composites let you efficiently design complex composites structures
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2014 UGMs
ANSYS HPC for Mechanical Applications
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Mechanical HPC Capabilities
• Types of parallel processing for Mechanical APDL
– Shared memory parallel (-np > 1) • First available in v4.3 • Can only be used on single machine
– Distributed memory parallel (-dis -np > 1) • First available in v6.0 with the DDS solver • Can be used on single machine or cluster • Recommended for all multiple core analyses due to performance!
– GPU acceleration (-acc) • First available in v13.0 using NVIDIA GPUs • Supports using either single GPU or multiple GPUs • Can be used on single machine or cluster
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Distributed ANSYS Architecture
Geometric domain decomposition approach
• Break problem into N pieces (CPU domains)
• Elements can only belong to a single D-ANSYS process
• Nodes can be shared across multiple processes
• Communicate information across the boundaries as necessary using MPI
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Scalability Considerations
Load balance (we enhance it every revision) • Each processor does same amount of work, no waiting
• It is done by domain decomposition: user cannot control it
Amdahl’s Law (we enhance it every revision) • Algorithmic enhancements: every part of the code is to run in parallel
• DANSYS major hurdles are: CE/CP, Contact, etc.
User controllable items: • Contact pair definitions: big contact pairs hurt load balance
• CE definition: many CE terms hurt load balance and Amdahl’s law
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Scalability Considerations: Contact
• Avoid defining whole exterior surface as one piece target
• Break pairs into smaller pieces if possible
• Remember: one whole contact pair is processed in one
processor
Define half circle
as target, don’t
define full circle
Avoid overlapping
contact surface if
possible
Define potential
contact surface
into smaller
pieces
32 © 2013 ANSYS, Inc. May 27, 2014 ANSYS Confidential
Distributed ANSYS Performance
• Improved the domain decomposition step in R15.0
– Faster performance at higher core counts (better scalability)
8 node Linux cluster (8 cores and 48 GB of RAM per node, Infiniband DDR)
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R15.0 GPU Acceleration Enhancements
• Improved performance on NVIDIA (Kepler) GPUs – R15.0 can be up to 30% faster than previous version
1.2x 1.2x 1.4x
1.5x
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Turbine benchmark BGA benchmark
Re
lati
ve S
pe
ed
up
Improved Performance on Tesla K20
R145 (8 cores)
R145 (8 cores + 1 GPU)
R15 (8 cores + 1 GPU)
Linux server (32 Intel Xeon E5-4650 cores @ 2.7 GHz, 2 Tesla K20Xm, 512 GB RAM)
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Maximizing Performance Distributed ANSYS Performance
1 Billion DOF 64 Cores 13 Hours Later
Whole new class of problems can be SOLVED!
1 Billion DOF Solved!
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2014 UGMs
Modeling Layered Composites the Simple Way
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Composites offer tremendous weight savings, increased performance, and design flexibility for a wide range of applications
The simulation of composites products is challenging because of a complex setup due to the many different materials, orientations and plies layups as well as specific failure analysis
ANSYS solutions for composites let you efficiently design complex composites structures
Composite Modeling
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ANSYS Composite PrepPost provides and easy definition of interface layers for the computation of delamination
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Accuracy is provided by validated element formulation, solution speed by the solver performance
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Improved First-Fly Failure Analysis
39
• Failure criteria, computed from stress or strain results, are commonly used to determine where the failure may start
• Failure criteria added: Hashin, Puck, LaRc03, LaRc04, USER
• Material strength properties can be defined through TB, FCLI command, eliminating limitations on the number of temperatures and material types
• FCTY to select specific failure criteria for post-processing
• Extended to support all elements
LaRc03 fiber failure criterion on a composite plate under uniaxial load. FC < 1 Safe
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Sub-modeling techniques are useful to create a local 3D model of any part of a composites structure, reducing the computational cost while improving the local accuracy of the results
Global Results
SHELL
SOLID Local results
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Thermal support for solid composites allows thermal induced stress calculations
Thermal solid composites are now supported in models with Imported Layered Sections.
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Enhanced SOLSH190 Transverse Shear • Transverse shear strains are enhanced to allow for parabolic
distribution through the thickness
• Improved accuracy in element stiffness and stress results
• Activated via KEYOPT(2)
Without transverse shear enhancement With transverse shear enhancement
Reference max. deflection: 0.0602.
Reference max. transverse Shear: 6854
Thick clamped square plate under distributed load
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Progressive Damage Material Models
• Nonlinear material models to simulate damage progression in layered composites.
• Suitable for determining the ultimate composite strength
• Damage initiation based on failure criteria
• Damage evolution with instant material property degradation (MPDG) or Continuum Damage Mechanics (CDM) methods
• Available solution quantities:
– PDMG : progressive damage parameters
– PFC : failure criteria based on effective stresses
Progressive failure of a 3-ply composite plate
Fiber Tension Damage Matrix Tension Damage
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To further improve your design, you could investigate advanced failure modes such as crack propagation, progressive damage or drop-test analysis
Debonding of a composite structure
Start of damage (layer 1)
Progressed damage (layer 1)
Progressed damage (layer 3)
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Optimize your product by performing as many virtual design variations as you need before creating the first physical prototype
Change the value of any dimension then update the entire model automatically
Create response surfaces for optimization
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2014 UGMs
Other Enhancements
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• The T-stress represents the stress acting parallel to the crack faces
• T-Stress calculation is now supported in R15
• It helps predict stability and whether the crack will deviate from the original plane
• Continued R&D on crack growth simulation based on XFEM
Fracture Mechanics *
* Stress intensity factor K and the elastic T-stress for corner cracks L.G. ZHAO, J. TONG and J. BYRNE
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• Support implicit Creep with Chaboche Kinematic Hardening
• Support for USER CZM laws for modeling advance delamination
• Option to Control results output data of User State variable, which helps reduce size of the RST file
• Shape Memory Alloy support for beam elements allows for faster modeling and computation of structures
Materials Technology
Beam188 Solid185
Total Solution Time BEAM188 : SOLID185=1:4
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• ARCLENGTH solver is typically used for applications like nonlinear buckling, sheet warpage etc.
• Re-written, More robust at R15, supports • MPC bonded contact
• Models with mixed shell/solid elements and elements with U/P formulation
• Remote loads, Tabular loads (need to be linear), Non zero displacement boundary conditions
• Distributed Parallel Processing
Enhancements to ARCLENGTH solver
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• Multi-frame Restart with 22X Helps with transient problems with thermal-electric physics e.g. Joule Heating,
• Linear Perturbation now supported with 22X elements for Piezoelectric and LF EMAG applications
• Fast Thermal solver is now supported with distributed ansys
• View Factor data available in compressed binary format or higher precision ASCII file
Thermal & Coupled Physics
Image courtesy of Piezo Systems, Inc.
Image courtesy of Marlow Industries
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Robustness improvements for contact modeling
Nonlinear mesh adaptivity
Multi-physics coupling
Fracture mechanics
Composites
HPC
Your requests
Future Directions
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