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Structural Capabilities
Christof Gebhardt, CADFEM Germany
3rd CADFEM ANSYS Simulation Conference, Ireland
23rd & 24th November 2015 - Engineers Ireland, Dublin
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Agenda
• Material
• Statics
• Dynamics
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Material
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Material Modeling
• Material behavior might depend on
• Load level
• Temperature, temperature history
• Time / Rate
• Load history
• Number of load cycles
• Direction of loading
• Humidity, neutron flux
• Material failure
ss
ET3
T2
T1
ee
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Material Modeling
• For all kinds of material
• Metal
• Rubber
• Plastics
• Composites
• Powder
• Concrete
• Soil
Source: Dynardo GmbHSource: MAN Diesel & Turbo SE
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Standard Material Models within ANSYS
Gummi, Kunststoffe
Metall
Geomaterial
Kleber
Dichtungen
Verschleiß
Kontakt
SMA
Dämpfung
Individuell
Migration
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Use case
• Clip on a pen
• Different material models
• Linear
• Bilinear
• s-e-table
• Results
• Impact of factor 2-3
• Nonlinear model is essential
Forxce [N] stresses [MPa]
Linear Material 2.89 43
Bilinear Material 1.35 14.1
s-e-table 1.45 13.8
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Geomechanics Material
• Accurate behavior
• Jointed rock, sand, clay, concrete
• Softening and hardening
• Opening and closing of gaps
• Rissbildung und –schliessen
• Porous media
• Nonlinearities
• Directional properties
• Analysis of damages buildings or
interaction with support
• Analysis of natural of created
cavities
Cavities and collapsing structures
Soil in different compositions
Interaction ofbuilding and support
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Geomechanics Materials for Non-Civil-Engineers
• Ceramics
• Graphite
• Wood
• Soft in tensile
• Stiff in pressure
• ??? Idea: homogenized cables
• Soft in pressure
• Stiff in tensile
Courtesy: Pfisterer Holding
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If Own Material Model Required: User Defined Material
• User programmable subroutines
• Implementation of own, new material
models in Fortran, C
• Example:
• Holzapfel material model for human
arteries
• Reinforcement by collagen fibrils
• Anisotropic, hyperelastic, biological
tissue
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Composite Solutions
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Endless Fiber vs. Short Fiber Reinforced
• Long fiber reinforced, layered
• Fast and efficient composite
preprocessing
• Composite optimized
post-processing with
up-to-date failure criteria
• Short fiber reinforced
• Account for microstructure in form of
size, shape, and orientation
• Investigate local stresses and strains
on fiber-matrix level
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Long Fiber: ANSYS Composite PrepPost
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Short Fiber: MOLDSIM Interface
• Connect Injection Molding simulation
with ANSYS Workbench
• Consider production process for
accurate material modeling
• locally varying fiber orientation
• initial stress distribution
• different stress distribution, factor
2.5 in deformation
• Quantify influence of scattering input
parameters
• fiber mass fraction, fiber aspect ratio,
position of injectors, processing
conditions
isotropic, homogenous (top) &
fiber reinforced, anisotropic (bottom)
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Benefits of Advanced Material Modeling
• Accurate behavior with comprehensive standard material model library
• Metals
• Rubber, foam
• Plastics
• Concrete, rock, soil …
• Openness for user defined material models
• Efficient composite workflow
• ANSYS Composite PrepPost ACP
• CADFEM MOLDSIM Interface
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Statics
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Industry Proven Workflows
• AGCO Powertrain:
Engineering time 1h
• Robust mesh generation
• Automatic contact detection
• Bolt load definition by object generator
• Robust and fast nonlinear contact
analysis
Courtesy of AGCO FENDT
3,367,393 Nodes
146 bolts
External forces from multibody simulation
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Static Analyses – Stiffness of a gear
• Stiffness of a gear
• Controlled deformation
• Load path and distribution
• Reduced contact pressure
• precision and life
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Static Analyses – Fatigue Life of an Injection Molding Machine
• Structural loads
• Pressure
• Thermal loads
• Temperature gradient
• Thermal strain
© CADFEM 2016nCode DesignLifeANSYS Fatigue FKM inside ANSYS
Fatigue Life
• Cyclic loading
• Unwelded structures
• With and without preload
• Stress and strain life
• Fast assessment without
focus on specific standard
• General purpose Fatigue
asessment
• Unwelded and welded
structrres
• Time and frequency
domain
• Test data
• Advanced technologie for
rotating principal stresses
• Static and dynamic
assessment according
FKM guideline
• Unwelded and welded
structures
• Steel and Aluminium
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Stability Analysis
• Linear Buckling
(Eigenvalue Buckling)
• Fast
• For linear systems
• No imperfections
• Non conservative results
• Often required by
rules & standards
• Nonlinear Buckling
• Imperfections
• All kind of nonlinearities
• Advanced Numerics for stabilization
• Arc length method
• Numerical stabilization
• Stabilization by inertia
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Stability Analysis
• Buckling of a crane cantilever
• Extensive experimental setup and
instrumentation
• Fast and cost effective FEA-
simulation and Optimization
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Benefits of Statics Simulations
• Stiffness in high precision
applications
• gear tooth, machine tools
• Strength for lightweight structures
• payload, costly materials
• Life-time reliable products by fatigue
simulation
• cyclic loaded structures
• Stability for slender structures
• cranes, wind turbines
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Dynamics
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Structural Dynamics
• Dynamic behavior considers mass
effects, inertia & damping
• Two Viewpoints
• Frequency domain
• Time domain
Dynamic deformation ≈ 2 x Static deformation
A chair may be loaded statically or dynamically
Statics 11.725
mm
Dynamics 23.31
mm
p(t)u(t)K(t)uCü(t)M
Courtesy of Herman Miller, Inc.
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Frequency Domain
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Modal Analysis
• Modal analysis yields
• Eigenfrequencies
• Eigenforms
• Foundation for modal superposition
• Effects available
• Pre-stress
• Rotordynamics: Frequency affected by
rotation speed
• Damping by internal / external fluid
• Friction induced vibration
• Goal: Prevent or enable resonance
m
k
Source: CADFEM GmbH
1st Eigenfrequency
2nd Eigenfrequency
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Harmonic Analysis
• Harmonic analysis yields
displacement and stresses as a
function of frequency
• Harmonically varying forces or
displacements can be applied
• Includes pre-stress effects and
damping
• Goal: Understand the vibration
amplitudes
Harmonic Response
3th Eigenfrequency
Source: Gebr. Hermle
Maschinenfabrik
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Random Vibration
• Simulation with stochastic approach
• Excitation with all frequencies &
unknown time history (e.g. white noise)
• Wind and wave excitation, electronics
in automotive or aerospace industry
• Based on Power Spectral Density
PSD
• Often standardized by assessment
rules
• Load for subsequent Fatigue
analysis
Source: Wikipedia
Power Spectrum Density
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Benefits of Dynamics in Frequency Domain
• Controlled vibrations
• Prevent resonance
• E. g. machine tools, drive systems,
plants
• Activate resonance
• E. g. sonotrodes, energy harvester
• Understand the driving factors for
amplitudes
• Frequency domain is fast!
• Speed by modal superposition
• Linear simulation model required
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Transient Dynamics
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Different Numerical Methods in Transient Dynamics
• Transient Dynamics requires results on n time steps
• Traditional Transient Full approach is time consuming
• Speed up the simulation in order of magnitudes
• Focus on the required effects
• Select the appropriate solution technology
Use explicit time integration
Condense body to a point
Use modal eigenvalues
Transient Full
Explicit
Rigid
Modal based Transient
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Explicit: Crash, Impact, Droptest
• All Nonlinearities
Goal: Integrity and Safety
Containment Test of a turbo machine
source: CADFEM
Drill hammer
droptest of a shower head, source: Hansgrohe
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Rigid Body Dynamics
• Fast rigid body transient analysis
• Joint library
• Stiffness and damping, stop angles
• Nonlinear effects included
• Large deformation, rotation
• Non-linear contact
Goal: Improved motion
Source: CADFEM GmbH
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Multibody Analysis with Flexible Bodies by CMS
• Joint Library
• Consider elasticities
• Nonlinear effects
• Contact
• Large rotation
• Goal: Accuracy
1Automatic detection of condensable
parts
User can decide if that parts should be
reduced or not
2
List of condensable parts
Integrated result expansion
3
4
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Additional Benefit of Elasticity: Fatigue!
• Transient stresses are basis for
fatigue assessment
• Rainflow counting
• Damage accumulation
• Computes the number of possible cycle
re-runs
• ANSYS nCode DesignLife
• Multiaxial assessment
• Parametric Workbench workflow
• Industry proven, established and
certified technology
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Benefits of Dynamics in Time Domain
• Improved motion in kinematic systems
• Rigid and flexible body behavior for adapted accuracy & speed
• Secured misuse
• Drop test, impact, crash
• Understanding for any time dependent process with any effect
• all kinds of loads
• all kinds of nonlinearities
• e. g. time dependent stresses for fatigue life
• Complete portfolio of simulation speed-up technologies for optimal
performance and accuracy
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Summary
• Material: Essential for accurate results
• Statics: Advanced workflows including assessment
• Dynamics: Different technologies for accuarcy and performance