Titelmasterformat durch Klicken bearbeiten Structural ... · Stability Analysis •Linear Buckling (Eigenvalue Buckling) •Fast •For linear systems •No imperfections •Non conservative

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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