Recent Developments in...

1 © 2013 ANSYS, Inc. May 27, 2014 ANSYS Confidential

Recent Developments in ANSYS/Structure

Yongyi Zhu

UGM, May 2014


2014 UGMs Topics:

Recent Developments in Contact modeling

ANSYS HPC for Mechanical Applications

Modeling Layered Composites the Simple Way

Other Enhancements


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


Fluid penetration loading – Apply fluid pressure based on contact status – Path dependent


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


Wear modeling – Wear contact surface due to pressure and friction – Contact nodes are physically moved


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


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


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


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


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


MADPL: Contact Surface Wear

where:


Contact Surface Wear Contact Pressure Before Wear Contact Pressure After Wear

Wear Wear Pressure Pressure


• 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


• 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


UPF Application: Lubricated Contact

Contact gap

Contact pressure


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%


• ‘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.


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


• You can easily apply a moment a torque or a rotation to the joint by sliding it to Setup




• Screw joint produces some interesting results in terms of contact

Frictional Stress under Bolt Head

Frictional Stress between the two bolted bodies


Using a cylinder/screw joint the stress appear without significant bending

Using conventional bolt pretension, the stresses appear with significant bending with rotation



• 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


• 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


• With sufficient mesh refinement, stress profiles match very closely

…Bolt Thread Modeling


• 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


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


• 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


2014 UGMs

ANSYS HPC for Mechanical Applications


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


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


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


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


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)


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)


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!


2014 UGMs

Modeling Layered Composites the Simple Way


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


ANSYS Composite PrepPost provides and easy definition of interface layers for the computation of delamination


Accuracy is provided by validated element formulation, solution speed by the solver performance


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


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


Thermal support for solid composites allows thermal induced stress calculations

Thermal solid composites are now supported in models with Imported Layered Sections.


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


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


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)


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


2014 UGMs

Other Enhancements


• 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


• 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


• 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


• 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


Robustness improvements for contact modeling

Nonlinear mesh adaptivity

Multi-physics coupling

Fracture mechanics

Composites

HPC

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