7 Christian Gaier Multi Axial Fatigue Analysis With the Fe Post Processor Femfat Utmis 2010

Multi-axial Fatigue Analysis with the FE Post-processor

FEMFAT

Christian GaierUTMIS Spring Meeting, rebro, 25-26 May 2010

ECS / Disclosure or duplication without consent is prohibited

Content

Short introduction Engineering Center Steyr, Magna

Introduction fatigue solver FEMFAT

The influence parameter concept

Multiaxial fatigue life prediction with FEMFAT MAX

Theory

Channel based, transient and modal approach

Parallelization

Result visualization and interpretation

Critical load case

Application examples


Engineering Center Steyr, St. Valentin

Software Products Durability Analysis (FEMFAT)

Thermal Management (KULI)

Vehicle Driving Simulation (FASI)

Simulation Dip Coating (ALSIM)

Engineering Integration Base - PDM / SAP ERP Interface(EIB)

Electric-CAX Integration (EB Cable)

Technology NVH & functional chassis dyno

16 fully automated engine test benches

2 drivetrain test benches

Fatigue lab (more than 100 servo cylinders)

On-site proving ground for functional & endurance testing

Range of Services System Integration

Commercial Vehicle Engineering

Drivetrain Engineering

Engine Engineering

Simulation & Testing Services

Electric / Electronics

Acoustics and Vibration Diagnostics

Production in low Volumes

Headcount: ~400

map

ECS / Disclosure or duplication without consent is prohibitedAuthor: Gaier 5Date:17.05.10

TZS - Technology for the

Vehicle Development Process

Concept, design

DMU, load data

Dynamics - MBS FEA & fatigue

Vehicle thermal

management

First prototype

Fatigue laboratoryComfort & acoustics

Verified prototype

E-TIS Tech. Info Systems J.Reichweger 21

E-TB Simulation/Software R.Reitbauer18

E-TF Structural Analysis H.Dannbauer39

E-TH Fatigue Testing P.Phringer13

E-TM Load Data Measur. J.Traunbauer12

E-TA Acoustics A.Wieser

7

Staff 110

FEMFATCFD

KULI

KABI

ECS / Disclosure or duplication without consent is prohibited 6

FEMFAT -BASIC

-PLAST

-BREAK

-HEAT

-EHD

-NVH

-FEDIS

FEMFAT -WELD

FEMFAT -STRAIN FEMFAT -MAX

FEMFAT -SPOT

FEMFAT -LAB FEMFAT Visualizer

FEMFAT

Finite Element Method FATigue


MBS / MD

ABAQUS

MECHANICA

MEDINA

PATRAN

ANSYS

NASTRAN

I-DEAS

COSMOS

HYPERMESH

BASIC

MAX

WELD

SPOT

PLAST

BREAK

STRAIN

HEAT

FEMFAT

Interface

Files

Nodes

Elements

PODs

GroupsInterface

Files

Stresses

FEA

Solver

FEA

PreprocessorIn

terf

ac

e F

ile

s

Lo

ad

His

tori

es

Lo

ad

Sp

ec

tra

MB

S

Me

as

ure

men

t

MBS / MDADAMS

.

RPC III

Graphical

Presentation

FEA

Postprocessor

Material

Data Base

Haigh Diagrams

S/N Curves

Material

Generator

FEMFAT

Visualizer

Damages

Safety Factors

Fatigue Life

Interface

Files

Full Integration to FE-Software Environement


Stress Tensors

Material Properties

Stress Gradient

Mean Stress Influence

MultiAXial Load

Technological Influences

Size Influence

Temperature Influence

PLASTic Deformations

SPOT Joints s

Anisotropical Behaviourof Arc WELDs

etc.

S/N1 modified

by FEMFAT

Load CyclesS

tre

ss A

mp

litu

de

S/N material

from specimen tests

Local Stress Concept


Str

ess A

mp

litu

de S/N1

Load CyclesS/N material

S/N1


S/N2


Local component S/N curve for each FE-node

(synthetic S/N curves)


N

a

FF

location 1

S/N curve location 1

location 2

S/N curve location 2

Notch Support Effect, Local S/N Curve

Notch Support Effect

a endur 1 < a endur 2


endurance stress

Relative Stress Gradient

Bending =2/b

=2/b

a Bending

M M

Relative Stress Gradient

Tension / Compression alt TC=0

a Tens / Comp

=0

F F

v

v

TCaltBendingalt

enDurGb

f '2

11

Influence of the Relative Stress Gradient

to the Fatigue Strength

ECS / Disclosure or duplication without consent is prohibitedAuthor: FEMFAT Support 12Date:20.02.08

0

0.2

0.4

0.6

0.8

1

1.2

0 200 400 600

St37

St52

42CrMo4

GS40

GGG40

GG25

AlSi10Mg

According German FKM-Guideline

)100(101 3,, CTaf afTafTE

)10(0.11 3, Tf afTE

23

,, )10(1 Taf DTafTE

)50(101 3,, CTaf DTafTE

Rolled Steel

Fine grained steel

Grey Cast Iron, Nodular Cast Iron

Aluminum

Temperatur Influence


0,50

0,60

0,70

0,80

0,90

1,00

1,10

0 25 50 75 100 125 150 175 200 225

RZ, B

f SR

, a

f

St37

St52

42CrMo4

GS40

GGG40

GG25

AlSi10Mg

According IABG: Valid for UTS < 1200 MPa

Surface Roughness in m

)lg45.0(lg)(lg22.01

)lg45.0(lg)(lg22.01

, 53.0,

64.0,

53.0,

64.0,

MZMZ

CZCZ

RUTSR

RUTSR

afSRf

Surface Roughness Influence


0,80

1,00

1,20

1,40

1,60

1,80

2,00

0,00 10,00 20,00 30,00 40,00 50,00

sample thickness dP

f RO

, a

f

Sample Thickness

Surface Treatment Influence


Str

ess

Ma

x-

Me

an

Strain

Mean Modified

Max Modified

Min Modified

Ma

x-

Me

an

Neuber-Hyperbola

Max

Min

Mean

Ma

x-

Me

an

FEMFAT PLAST with Neuber Hyperbola


The directions of the principal stresses

may change permanently.

Therefore classic criteria like

Maximum Principal Stress

Von Mises Stress

Octahedral Shear Stress

etc.

are not applicable for

multiaxial fatigue analysis.

Critical Plane Criterion

Ex

tern

al F

orc

e F

1(t

)

External Force F2(t)

dA

Internal Reaction

Force dF(t)

Internal Reaction

Force dFShear(t)

Internal Reaction

Force dFnormal(t)

Multiaxial Fatigue Analysis

ECS / Disclosure or duplication without consent is prohibitedAuthor: Gaier 17Date:17.05.10

Transformation of stress tensors

into several material planes

Filtering of interesting planes

Generation of the load histories

of the stress components

Rainflow cycle counting of equivalent

stress history in all selected planes

Damage analysis

(Influence Parameter Method)

The cutting plane with maximum damage is

assumed to be the critical plane for fatigue failure

)(

)(

)(

zzzzyyzxxz

yzzyyyyxxy

xzzxyyxxxx

nnne

nnne

nnne

Critical Plane Criterion in FEMFAT MAX

n


Selection of Cutting Planes

Biaxial Stress State Triaxial Stress State

Components Surface n1n2 ni

nN

ni ... Cutting Planes Normal Vectors, i=1-N


Loop over surface nodes

Does the node lie on an

inwarding notch?

NO YES

plane-normal-

vectors:

Plain stress

nS u r f a c e

plane-normal-

vectors:

3D - stress

nS u r f a c e

nS u r f a c e

User Definition

Cutting Plane Filter in FEMFAT MAX


Rainflow

time

Rainflow Counting of Closed Hysteresis Loops


Total Damage:

D = d i = d1 + d2 + d3 + ... + dn

- +MEAN

A3 M3 n3A2 M2 n2

A1 M1 n1

di = ni

Ni

A1

n1

N (log)N1 N2 N3

A2A3

n2 n3

S/N1S/N2

S/N3

Analysed S/N Curves at a

FE-Node by FEMFAT

Linear Damage Accumulation by Palmgren Miner


A

+ M- M

a e crit

a endu

Criteria ( m=const)

for critical

loading point:

Mina endu

a e crit

HAIGH diagram and loading points

are calculated for all cutting planes

Critical Cutting Plane Criteria

n


Signed Equivalent Stress (similar Mises)

- Problem

n

e

t

Material ductility:

= 1.73 ductile (e.g. steel)

~ 1.4 semi-ductile (aluminum)

= 1 brittle (grey cast iron)

2

2

2

fl

fl

nne sign

Unreasonable

Results!


Two Solutions Developed by ECS

Critical Component Method

High end solution for accurate fatigue life results of arbitrarily non-proportional loaded components

But high computation effort

Scaled Normal Stress Method

Fast solution for accurate fatigue life results of arbitrarily non-proportional loaded components

But no consideration of shear Haigh-diagram

Author: 24Date:


Sn,d(t) = Sn(t) d

Plane

n

Sn(t)

n ... Normal Vector of Plane

Sn(t) ... Stress Vector

d ... Unit Vector for Stress Projection

Sn,d(t) ... Stress Component in Direction d

d

.Sn,d(t) Stress component Sn,d(t)

in direction d is used for rainflow-

counting and damage analysis:

Stress component with maximum

damage is assumed to be critical

for fatigue failure

Critical Plane Critical ComponentCriterion

..

Sn(t)

Nn(t)

Tn(t)

Tn,d(t)

Nn,d(t)



Cutting Plane

nSn,d

Nn,d

Tn,d

.

n ... Cutting Planes Normal Vector

Sn,d ... Stress Component in Direction dNn,d ... Normal Stress

Tn,d ... Shear Stress

= 0 ... pure Tensile Load

= 90 ... pure Shear Load

= 180 ... pure Compressive

Load

.



1

R1

0

100

200

300

400

500

600

700

800

900

1000

1100

1200

1300

1400

1500

1600

En

du

ran

ce

Lim

it [Mp

a]

Mean Stress [Mpa]

Po

lar A

ng

le [d

eg

]

Generalized Haigh-Diagram Ck45

-850 8500

90

0

Critical Component Method:

Haigh Diagram for Steel

Smooth transition between tension/compression and

torsion Haigh-diagram

(Haigh-surface)


Advantages:

- Independent from coordinate system

- Normal and shear stress and all their combinations are taken into account

- Applicable for non-proportional stochastic loading

- No discontinuities in stress histories, Rainflow-counting is problem-free

- Applicable for ductile, semi-ductile and brittle materials

- Tension/compression and torsion Haigh-diagram can be defined independently

from each other

- Smooth transition between tension/compression and torsion Haigh-diagram

(Haigh-surface)- Generally applicable for bi- and tri-axial stress states

- Physical interpretation possible as critical component of stress vector

Disadvantage:

- High computation effort

Critical Component

Use Group with Critical Areas


Principal stresses with :

Calculation of stress ratio V :

3

1V

1

3V

321

31for

13for

11 V

Fast Solution: Scaled Normal Stress in Critical

Plane

V can be used to identify

the loading type!


1V

0V

1V

Mohrs circle of stress:

Torsion loading:

Uniaxial tensile loading:

Hydrostatic loading:

13for

03for

13

13

321for

Scaled Normal Stress in Critical Plane


Scaled normal stress Signed Equivalent stress

The critical plane procedure and Rainflow counting is performed with scaled normal stress There are no unphysical discontinuities Negative damaging effect of torsion load is considered by scaling up the stress tensor by

factor f > 1

For brittle materials k = 1 f = 1 Normal Stress Hypothesis Magnitude of hydrostatic stress is scaled down which correlates with distortion energy

criterion

Generally applicable for bi- and tri-axial stress states Applicable for finite and infinite life domain

Stress tensor is scaled with f depending of V :

Vkf )1(1Scale factorfl

flk


material ratio


Combined in-phase loading acc. Dietmann:

Combined in-phase loading acc.

Gough-Pollard and Scaled Normal Stress:

fl

flk1

2

fl

a

k

fl

a

fl

a

brittle

ductile

fl

a

121

22

fl

a

fl

a

fl

a kk



Results

Damage Values

Endurance Safety Factors

Life

Specimen Material Data

FV=

Channel 1

FT=

Channel 2

FL=

Channel 3

Data Processing in FEMFAT ChannelMAX


FE

Modal Stresses

12

n

Component Modes

12

n

MBS

and

(E)HD

(Co - Simulation)

qn(t)

q2(t)

q1(t)

Modal

Coordinates Channel 1

Channel 2

FEMFAT

1q1(t)

2q2(t)

qn(t) n

Channel n

Additional

Load Cases

(Bolts,...)

Fatigue

Lifetime prediction of dynamic

loaded parts considering

dynamic effects due to natural

vibrations

Fatigue Analysis based on Modal Stresses

FE + MBS + FEMFAT


0

10

20

30

40

50

60

70

80

90

0 180 360 540 720

Combustion

Pressure +

Mass Forces

Transient Load Condition

in Time

Results

Damage Values

Endurance Safety Factors

Life

One Stress Result for

Each Time Step

Specimen Material Data

Data Processing in Transient MAX


Flexible

No superposition

No linearity between time steps

required

Fully automated input/output file

handling

High disk space efficiency

Low disk access rate entails low

network load

FEMFAT MAX Transient -Benefits


Sequence of stress results Engine bulkhead and bearing

cap or crankshaft with stress

result each n crankangle

Load application point and

boundary conditions are

altering with time

Sequence of stress results

TRANS MAX

One stress result for each

channel (e.g. for unit load)

One load history for each

channel

Chassis parts like:

Knuckles, subframes,

H-Arms,...

Body in White

Crankshaft with modal

approach

Direction of Principle Stresses

are permanently altering

Direction and location of forces

and boundary conditions are

constant

Existing Load Histories

More than one channel, which

are generally not in phase

CHANNEL

MAX

Two stress results, which

can be:

Upper and lower stress

or

Amplitude and mean stress

Load spectra if neccessary

Con rod with the two

dominating load cases ignition

and intertial force

Engine bulkhead and bearing

cap (assambly and ignition)

Shafts with torgue history (only

one channel)

Direction of principle stresses

are constant

2 Load Conditions

BASIC

What to ImportExamplesWhen to useModule

FEMFAT Modules Which to use for your Application


Parallel Damage Analysis by Group Segmentation

Example: Dividing FE-Structure into 3 groups with 10% relative

nodal filter limit for ChannelMAX analysis:

Working for

Multi-processor systems Multi-core processor systems All FEMFAT modules Linux, Unix, Windows

Optimized for:

ChannelMAX Consideration of nodal filter Base material nodes


FEMFAT Output: Equivalent Stress History

Equiv. Stress History


Damage History

FEMFAT Output: Damage History


VISUALIZER: Show Stress and Damage Histories

of Nodes From HISTORY Group

Zoom


Description of the Critical Load Case

MAX

MIN

FEMFAT analysis

Nastran analysiswith a new load card

What is the representative as

the most damaging loading?

Critical load case

Specify critical point

for FEMFAT

Visualize

Displacements

and stresses(e.g. with I-DEAS)

+

Stress Data

Load history

C1

C2

C3


Multiaxial fatigue prediction of a McPherson strut

Suspension Analysis

ADAMS model ABAQUS model


Suspension Analysis

Cracks during

testing

19 Load channels Contact / friction Channel splitting for press fit

Damage from FEMFAT MAX + WELD analysis


Swivel Hub, made from AlSi7Mg ta

Suspension Components

Forces at the Tire

F xF y

F z

BMW Benchmark:

Aluminium Axle Component


-10

-5

0

5

10

15

0 10 20 30

F X

F Y

F Z

Const

Calibra

tion Fa

ctor

s

Time (short part)

TEST: 2420 Periods

FEMFAT: 3020 Periods

TEST: 2160 Periods

FEMFAT: 3690 Periods

BMW Munich decided

to buy FEMFAT

after the benchmark

Von Mises Stress and

Histories

Damage Distribution

FEMFAT MAX Benchmark

Aluminum Axle Component


FEMFAT Result

Damage Distribution

Comparison FEMFAT MAX to Test-Results


Spare-Wheel Carrier: Durability Analysis Result

Test: 12 h

Simulation: 7,1 h

Stress Factor 1,07

Dynamic effects due to

natural vibrations

Good accordance between

real and virtual test rig

Amount of data similar to a

common FE modal

analysis


rpm sensitive fatigue analysis

endurance safety distribution

identification of resonances

Campbell diagram:

boundary conditions: (constant moment,

constant rpm)

modally based fatigue lifetime prediction with

FEMFAT-MAX considers

dynamic effects like

resonance excitations!

reasonable simulation time

Fatigue Results for V6-crankshaft

7 Christian Gaier Multi Axial Fatigue Analysis With the Fe Post Processor Femfat Utmis 2010

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Transcript of 7 Christian Gaier Multi Axial Fatigue Analysis With the Fe Post Processor Femfat Utmis 2010