7 christian gaier multi axial fatigue analysis with the fe post processor femfat utmis 2010
DESCRIPTION
multi axial fatigueTRANSCRIPT
-
Multi-axial Fatigue Analysis with the FE Post-processor
FEMFAT
Christian GaierUTMIS Spring Meeting, rebro, 25-26 May 2010
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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
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ECS / Disclosure or duplication without consent is prohibitedAuthor: Gaier 3
Magna Global Presence*
Global Facilities 333 | 25 Countries | ~ 71,000 People | $23.7 Billion2008 Sales
CANADIAN COMPANY FOUNDED IN 1957
* As of June 2009
NORTH AMERICA
FACILITIES | 127
EMPLOYEES | 25,700
US + CANADA
NORTH AMERICA
FACILITIES | 33
EMPLOYEES | 11,275
MEXICO + SOUTH AMERICA
EASTERN EUROPE FACILITIES | 25
TOTAL EMPLOYEES | 5,800
WESTERN EUROPE FACILITIES | 107
TOTAL EMPLOYEES | 23,300
EASTERN + WESTERN EUROPE
NORTH AMERICA
FACILITIES | 3
EMPLOYEES | 50
AFRICA
NORTH AMERICA
FACILITIES | 38
EMPLOYEES | 4,575
ASIA
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ECS / Disclosure or duplication without consent is prohibited
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
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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
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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
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ECS / Disclosure or duplication without consent is prohibited
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
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ECS / Disclosure or duplication without consent is prohibited
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
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ECS / Disclosure or duplication without consent is prohibited 9
Str
ess A
mp
litu
de S/N1
Load CyclesS/N material
S/N1
Load CyclesS/N material
S/N2
Load CyclesS/N material
Local component S/N curve for each FE-node
(synthetic S/N curves)
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ECS / Disclosure or duplication without consent is prohibited 10
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
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ECS / Disclosure or duplication without consent is prohibited 11
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
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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
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ECS / Disclosure or duplication without consent is prohibitedAuthor: FEMFAT Support 13Date:20.02.08
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
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ECS / Disclosure or duplication without consent is prohibitedAuthor: FEMFAT Support 14Date:20.02.08
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
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ECS / Disclosure or duplication without consent is prohibitedAuthor: FEMFAT Support 15Date:20.02.08
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
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ECS / Disclosure or duplication without consent is prohibited 16
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
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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
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Selection of Cutting Planes
Biaxial Stress State Triaxial Stress State
Components Surface n1n2 ni
nN
ni ... Cutting Planes Normal Vectors, i=1-N
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ECS / Disclosure or duplication without consent is prohibited 19
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
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ECS / Disclosure or duplication without consent is prohibited
Rainflow
time
Rainflow Counting of Closed Hysteresis Loops
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ECS / Disclosure or duplication without consent is prohibitedAuthor: FEMFAT Support 21Date:20.02.08
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
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ECS / Disclosure or duplication without consent is prohibited 22
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
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ECS / Disclosure or duplication without consent is prohibited 23
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!
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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:
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ECS / Disclosure or duplication without consent is prohibited 25
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)
Critical Component Method
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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
.
Critical Component Method
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ECS / Disclosure or duplication without consent is prohibited 27
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)
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ECS / Disclosure or duplication without consent is prohibited 28
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
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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!
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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
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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
Scaled Normal Stress in Critical Plane
material ratio
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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
Scaled Normal Stress in Critical Plane
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ECS / Disclosure or duplication without consent is prohibited 33
Results
Damage Values
Endurance Safety Factors
Life
Specimen Material Data
FV=
Channel 1
FT=
Channel 2
FL=
Channel 3
Data Processing in FEMFAT ChannelMAX
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ECS / Disclosure or duplication without consent is prohibited 34
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
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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
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ECS / Disclosure or duplication without consent is prohibited 36
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
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ECS / Disclosure or duplication without consent is prohibited 37
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
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ECS / Disclosure or duplication without consent is prohibited 38
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
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ECS / Disclosure or duplication without consent is prohibited 39
FEMFAT Output: Equivalent Stress History
Equiv. Stress History
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ECS / Disclosure or duplication without consent is prohibited 40
Damage History
FEMFAT Output: Damage History
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ECS / Disclosure or duplication without consent is prohibited 41
VISUALIZER: Show Stress and Damage Histories
of Nodes From HISTORY Group
Zoom
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ECS / Disclosure or duplication without consent is prohibited 42
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
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Multiaxial fatigue prediction of a McPherson strut
Suspension Analysis
ADAMS model ABAQUS model
-
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Suspension Analysis
Cracks during
testing
19 Load channels Contact / friction Channel splitting for press fit
Damage from FEMFAT MAX + WELD analysis
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Swivel Hub, made from AlSi7Mg ta
Suspension Components
Forces at the Tire
F xF y
F z
BMW Benchmark:
Aluminium Axle Component
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ECS / Disclosure or duplication without consent is prohibited 46
-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
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ECS / Disclosure or duplication without consent is prohibited 47
FEMFAT Result
Damage Distribution
Comparison FEMFAT MAX to Test-Results
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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
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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
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