3a john draper fe safe from safe technology utmis 2010
DESCRIPTION
Use of FE-safeTRANSCRIPT
fe-safe™ from Safe Technology
John Draper
fe-safe: what we do
fe-safe
The leading suite of software for fatigue design
Sold world wide to companies that design everything from
mobile phones to heavy engineering structures,
heart valves to engines
nuclear plant to wind turbines
fe-safe: what we do
fe-safe
The leading suite of software for fatigue design
Sold world wide to companies that design everything from
mobile phones to heavy engineering structures,
heart valves to engines
nuclear plant to wind turbines
High temperature fatigue of engines
High temperature fatigue of enginesFatigue of welded joints - VerityTM
Developed and patented by the Battelle
Institute. Licensed to Safe Technology
- world-wide agreement in place
- we take 40% of the software revenue
A large Joint Industry Panel (JIP) has guided
the research and validated the method.
The developer has received many awards -
Society of Automotive Engineers Henry Ford II
medal
Time Magazine 2005 maths innovator.
The potential market for the VerityTM method
is vast - for example -Very small components - drive shafts, bicycle
parts
Exhaust systems
Soldered joints and printed
circuit boards
High temperature fatigue of enginesFatigue of welded joints - VerityTM
Developed and patented by the Battelle
Institute. Licensed to Safe Technology
- world-wide agreement in place
- we take 40% of the software revenue
A large Joint Industry Panel (JIP) has guided
the research and validated the method.
The developer has received many awards -
Society of Automotive Engineers Henry Ford II
medal
Time Magazine 2005 maths innovator.
The potential market for the VerityTM method
is vast - for example -Very small components - drive shafts, bicycle
parts
Exhaust systems
Soldered joints and printed
circuit boards
Car bodies and car assembly plant
“This will save millions of dollars” - Ford
Fatigue of welded joints - VerityTM
Car bodies and car assembly plant
“This will save millions of dollars” - Ford
Fatigue of trucks and off-highway vehicles
Fatigue of pressure vessels
Fatigue of pressure vesselsFatigue of medical equipment
Medical equipment -
X-ray treatment and mobile
MRI scanners
Arterial stents
Fatigue of medical equipment
Medical equipment -
X-ray treatment and mobile
MRI scanners
Arterial stents
Fatigue of welded joints - VerityTMFatigue of medical equipment
Pressure vesselsMedical equipment -
X-ray treatment and mobile
MRI scanners
Arterial stents
Fatigue of welded joints - VerityTM…and fatigue of….
Pressure vesselsMedical equipment -
X-ray treatment and
mobile MRI scanners
Arterial stents
Safe Technology Limited
• Headquarters in Sheffield UK
• Safe Technology US is a wholly-owned subsidiary based in
Michigan with an office in Los Angeles
• World-wide distributor network includes ANSYS re-sellers
• fe-safe is sold worldwide by Dassault Systemes Simulia Corp
• Revenue growth is typically 30% per year
12
INTERFACES
Input/output
ABAQUS .fil
ABAQUS .odb
NASTRAN f06
NASTRAN op2
ANSYS .rst
I-DEAS .unv
Pro/M s01..., d01
General .csv
Output
Hypermesh .hmres
PATRAN
FEMVIEW
CADFIX
FEMAP
Redesign
Design
FEAABAQUS, ANSYS
I-DEAS,
NASTRAN, Pro/E
Stress
resultsfe-safe
fefe-safe durability analysis from FEA
Loading
Lifecontours
Mean stress
Stress
amplitude
Haigh Diagram
Stress
amplitude
N cycles
S-N curve
ampP (sf-sm)/E 2.00E+05 ampE ampP amp amp/Sao
0.000328 0.001855 1.25113 0.006059 0.313619 0.0019 0.000947 0.002848 1.194403
0.000328 0.001793 1.209275 0.005813 0.313619 0.001823 0.000947 0.00277 1.162002
0.000328 0.001731 1.16742 0.005567 0.313619 0.001746 0.000947 0.002693 1.129602
0.000328 0.001669 1.125565 0.00532 0.313619 0.001669 0.000947 0.002616 1.097201
0.000328 0.001607 1.08371 0.005074 0.313619 0.001591 0.000947 0.002539 1.064801
0.000328 0.001545 1.041855 0.004828 0.313619 0.001514 0.000947 0.002461 1.0324
0.000328 0.001483 1 0.004581 0.313619 0.001437 0.000947 0.002384 1
0.000328 0.001421 0.958145 0.004335 0.313619 0.00136 0.000947 0.002307 0.9676
0.000328 0.001359 0.91629 0.004089 0.313619 0.001282 0.000947 0.00223 0.935199
0.000328 0.001297 0.874435 0.003842 0.313619 0.001205 0.000947 0.002152 0.902799
0.000328 0.001235 0.83258 0.003596 0.313619 0.001128 0.000947 0.002075 0.870398
0.000328 0.001173 0.790725 0.00335 0.313619 0.001051 0.000947 0.001998 0.837998
0.000328 0.001111 0.74887 0.003103 0.313619 0.000973 0.000947 0.001921 0.805597
0.000328 0.001048 0.707015 0.002857 0.313619 0.000896 0.000947 0.001843 0.773197
0.000328 0.000986 0.665161 0.002611 0.313619 0.000819 0.000947 0.001766 0.740796
Location of max stress.
Calculate stress amplitude and
mean stress
Durability by design?
Dana Automotive Systems Group Case Study
Part of an automotive driveshaft assembly joint.
Cracks did not start from the maximum stress location.
This was corroborated by lab tests on actual specimens
fe-safe life contours Stress contours
Max principal stress
Shortest life
De
elastic-plasticstrain
Fatigue calculations using local strains
Same stress, same life
For crack initiation, life is determined by surface stresses and strains
Distance, r
rc
Whether the crack will propagate or not is defined by the
stress some distance below the surface.
This „critical distance‟ is a material property obtained from
DKth
“Notch sensitivity”
This stress determines if the crack will initiate
This stress determines if the crack will
propagate to failure
Will the crack grow ? - Critical distance methods
s
Distance, r
rc
Whether the crack will propagate or not is defined by the
stress some distance below the surface.
This „critical distance‟ is a material property
“Notch sensitivity”
This stress determines if the crack will initiate
This stress determines if the crack will
propagate to failure
High strength steel – critical distance is small (say 0.1mm)
Very „notch sensitive‟.
Cracks will usually propagate to failure
Critical distance methods
s
Distance, r
“Notch sensitivity”
This stress determines if the crack will initiate
This stress determines if the crack will
propagate to failure
High strength steel – critical distance is small (say 0.1mm)
Very „notch sensitive‟.
Cracks will usually propagate to failure
Grey iron – critical distance is large (say 2 mm)
Very „notch insensitive‟.
Cracks will often not propagate to failure
Critical distance methods
s
So now we can include…..the stress gradient „size effect‟ in fatigue
Shorter life to failure
…but same life to crack initiation.
So now we can include…..the difference between axial and bending
Axial loading gives
shorter life to failure
…but same life to crack initiation.
HF Moore - 1927
Crack initiation fatigue lives were related to the amount of
plasticity in notches
Plasticity
What do we mean by „plasticity‟ ?
Plasticity
Modern fatigue analysis is the study of the effects of small amounts of
inelasticity
Battelle 1947. Fatigue manual for US Navy
0
50
100
150
200
250
300
350
400
0 0.002 0.004 0.006 0.008
Strain
Str
ess:
MP
a0
50
100
150
200
250
300
350
400
0 0.002 0.004 0.006 0.008
Strain
Str
ess:
MP
a
SAE1030 steel
‘Yield stress’ =
0.2% proof stress
from tensile test
‘Yield stress’ =
0.2% proof stress
from tensile test
Cyclic test
Onset of plasticity
in fatigue
“we should look at that portion of the
stress-strain diagram between the
beginning of the tiniest permanent
deformation and the yield strength”
Plasticity
Fatigue analysis methods
What causes fatigue cracking ?
Plasticity is necessary to initiate fatigue cracks.
Tresca and von Mises are methods of calculating when a material
will „yield‟.
Tresca and von Mises are both based on shear stresses.
Therefore – shear stresses initiate fatigue cracks
(this theory is from around 1900)
Findley, 1959
Biaxial fatigue
Findley, 1959 - combine shear and normal stresses
Biaxial fatigue
Principal stresses may change orientation
Biaxial fatigue
Biaxial fatigue
Principal stresses may change orientation
Biaxial fatigue
Principal stresses may change orientation
Biaxial fatigue
Critical plane analysis searches for the most damaged plane
Fatigue analysis methods
1. If we use elastic FEA, we need a fatigue-based
plasticity correction to calculate elastic-plastic
stress and strain.
765
Life (cycles)
Str
ess m
ax/m
in (
MP
a)
-100
0
100
200
300
400
101010
SAE10302. Calculate combinations of shear stress-strain and
normal stress-strain.
3. Perform critical plane searching to find the
direction of crack initiation.
Metal fatigue - 1927
The endurance limit amplitude for a mixture of large and small
cycles is much lower than the constant amplitude endurance
limit.
Fatigue analysis methods
e
Constant amplitude
endurance limit
De
2
Endurance 2Nf
e
damaging
Endurance 2Nf
De
2
e
damaging less damaging
Endurance 2Nf
De
2
e
damaging less damaging non- damaging
Endurance 2Nf
De
2
Fatigue analysis methods
1. Calculate elastic-plastic stress and strain from elastic
FEA stresses.
2. Calculate combinations of shear stress-strain and
normal stress-strain.
3. Perform critical plane searching to find the direction
of crack initiation.
4. Modify the endurance limit to allow for the interaction
between large and small cycles.
5. If we are prepared to accept cracks, we use „critical
distance‟ methods to increase the allowable stresses.
765
Life (cycles)
Str
ess m
ax/m
in (
MP
a)
-100
0
100
200
300
400
101010
SAE1030
rc
Dso
rc
Dso
Local strain analysis allows for changes in mean stress caused by local plasticity
Elastic strains „pull‟ notch strains close to zero when load is removed
Tensile residual stress
Biaxial fatigue
(2 ) (2 )2
f
f f fb cN N
E
sDe e
Strain-life for uniaxial stress
max 1.65 (2 ) 1.75 (2 )2 2
fNf f f
b cN NE
sD Dee
Kandil-Brown-Miller „shear + normal‟
Combined shear and
normal strainUses uniaxial materials properties so
no extra materials data is needed.
1.0E-04
1.0E-03
1.0E-02
1.0E-01
1.0E+00
1.00E+00 1.00E+01 1.00E+02 1.00E+03 1.00E+04 1.00E+05 1.00E+06 1.00E+07 1.00E+08
Endurance 2Nf
2
eD
0
100
200
300
400
500
600
0 0.005 0.01 0.015 0.02 0.025 0.03
Strain
Str
ess (
MP
a)
Cyclic stress-strain curve
Used for calculating mean stresses. Used
for converting elastic FEA stresses into
elastic-plastic stress and strain.
Corrected for the effect of biaxial stresses.
Elastic-plastic strain-life curve
Used for calculating cycle-by-cycle fatigue
damage.
Corrected for the effect of biaxial stresses
to give a Brown-Miller analysis.
Materials data – effect of temperature
1.0E-04
1.0E-03
1.0E-02
1.0E-01
1.0E+00
1.00E+00 1.00E+01 1.00E+02 1.00E+03 1.00E+04 1.00E+05 1.00E+06 1.00E+07 1.00E+08
Endurance 2Nf
2
eD
0
100
200
300
400
500
600
0 0.005 0.01 0.015 0.02 0.025 0.03
Strain
Str
ess (
MP
a)
Cyclic stress-strain curve
Used for calculating mean stresses. Used
for converting elastic FEA stresses into
elastic-plastic stress and strain.
Corrected for the effect of biaxial stresses.
Elastic-plastic strain-life curve
Used for calculating cycle-by-cycle fatigue
damage.
Corrected for the effect of biaxial stresses
to give a Brown-Miller analysis.
Materials data – effect of temperature
Other environmental effects may include strain rate effects, strain ageing,
oxidation, stress relaxation and creep.
Forming and assembly stresses
Sheet Metal Forming Simulation
PunchBlank Holder
Die
Forming and assembly stresses
Fatigue life contours for a Ford oil-pan
(a) excluding and (b) including effects of
forming process
(a) (b)
Forming and assembly stresses
Assembly stresses, residual stresses etc, can be included.
Mean stress
Stress
amplitude
Haigh Diagram
Stress
amplitude
N cycles
S-N curve
ampP (sf-sm)/E 2.00E+05 ampE ampP amp amp/Sao
0.000328 0.001855 1.25113 0.006059 0.313619 0.0019 0.000947 0.002848 1.194403
0.000328 0.001793 1.209275 0.005813 0.313619 0.001823 0.000947 0.00277 1.162002
0.000328 0.001731 1.16742 0.005567 0.313619 0.001746 0.000947 0.002693 1.129602
0.000328 0.001669 1.125565 0.00532 0.313619 0.001669 0.000947 0.002616 1.097201
0.000328 0.001607 1.08371 0.005074 0.313619 0.001591 0.000947 0.002539 1.064801
0.000328 0.001545 1.041855 0.004828 0.313619 0.001514 0.000947 0.002461 1.0324
0.000328 0.001483 1 0.004581 0.313619 0.001437 0.000947 0.002384 1
0.000328 0.001421 0.958145 0.004335 0.313619 0.00136 0.000947 0.002307 0.9676
0.000328 0.001359 0.91629 0.004089 0.313619 0.001282 0.000947 0.00223 0.935199
0.000328 0.001297 0.874435 0.003842 0.313619 0.001205 0.000947 0.002152 0.902799
0.000328 0.001235 0.83258 0.003596 0.313619 0.001128 0.000947 0.002075 0.870398
0.000328 0.001173 0.790725 0.00335 0.313619 0.001051 0.000947 0.001998 0.837998
0.000328 0.001111 0.74887 0.003103 0.313619 0.000973 0.000947 0.001921 0.805597
0.000328 0.001048 0.707015 0.002857 0.313619 0.000896 0.000947 0.001843 0.773197
0.000328 0.000986 0.665161 0.002611 0.313619 0.000819 0.000947 0.001766 0.740796
Location of max stress.
Calculate stress amplitude and
mean stress
Durability by design?
Duty cycle
Stress
Material
data
Fatigue
analysisLife
Durability by design
All stresses and
temperatures
Define failure criteria –
based on risk
Duty cycles
Not just the
„most severe‟
Life
contours
1.0E-04
1.0E-03
1.0E-02
1.0E-01
1.0E+00
1.00E+00 1.00E+01 1.00E+02 1.00E+03 1.00E+04 1.00E+05 1.00E+06 1.00E+07 1.00E+08
Endurance 2Nf
2
eD
1.0E-04
1.0E-03
1.0E-02
1.0E-01
1.0E+00
1.00E+00 1.00E+01 1.00E+02 1.00E+03 1.00E+04 1.00E+05 1.00E+06 1.00E+07 1.00E+08
Endurance 2Nf
1.0E-04
1.0E-03
1.0E-02
1.0E-01
1.0E+00
1.00E+00 1.00E+01 1.00E+02 1.00E+03 1.00E+04 1.00E+05 1.00E+06 1.00E+07 1.00E+08
Endurance 2Nf
2
eD
0
100
200
300
400
500
600
0 0.005 0.01 0.015 0.02 0.025 0.03
Strain
Str
ess (
MP
a)
Strain-based,
high temp.
Biaxial, strain-based,
critical plane, critical
distance
INTERFACES
Input/output
ABAQUS .fil
ABAQUS .odb
NASTRAN f06
NASTRAN op2
ANSYS .rst
I-DEAS .unv
Pro/M s01..., d01
General .csv
Output
Hypermesh .hmres
PATRAN
FEMVIEW
CADFIX
FEMAP
fefe-safe durability analysis from FEA
Redesign
Design
FEAABAQUS, ANSYS
I-DEAS,
NASTRAN, Pro/E
Stress
resultsfe-safe
Loading
Lifecontours
Modern fatigue analysis is the study of the effects of small amounts of
inelasticity
Battelle 1947. Fatigue manual for US Navy
0
50
100
150
200
250
300
350
400
0 0.002 0.004 0.006 0.008
Strain
Str
ess:
MP
a0
50
100
150
200
250
300
350
400
0 0.002 0.004 0.006 0.008
Strain
Str
ess:
MP
a
SAE1030 steel
‘Yield stress’ =
0.2% proof stress
from tensile test
‘Yield stress’ =
0.2% proof stress
from tensile test
Cyclic test
Onset of plasticity
in fatigue
“we should look at that portion of the
stress-strain diagram between the
beginning of the tiniest permanent
deformation and the yield strength”
Plasticity
s
e
Elastic FEA
Amplitude is smaller
Mean stress is lower
s
e
S-N curves with elastic FEA
765
Life (cycles)
Str
es
s m
ax
/min
(M
Pa
)
Cycles at R=0. Elastic FEA (grey) and actual (black)
-100
0
100
200
300
400
101010
20
14
-
T6Strain
Str
ess
as
eas
as
2014-T6
S-N curves with elastic FEA
765
Life (cycles)
Str
es
s m
ax
/min
(M
Pa
)
Cycles at R=0. Elastic FEA (grey) and actual (black)
-100
0
100
200
300
400
101010
SAE1030
20
14
-
T6Strain
Str
ess
as
eas
asS-N curves with elastic FEA
Even for high cycle fatigue, mean stresses will be wrong unless we do a plasticity correction.
Without a plasticity correction, we are limited to „infinite life‟ design at mean stresses close to zero.
765
Life (cycles)
Str
ess m
ax/m
in (
MP
a)
-100
0
100
200
300
400
101010
SAE1030
S-N curves with elastic FEA
Changes in mean stress caused by local plasticity
S-N curves with elastic FEA
S-N curves with elastic FEA
Strain
Str
es
s
ms
ems
as
eas
as
Plasticity reduces the mean stress
We may try to adjust the Goodman diagram to
compensate for the error in calculating mean
stresses
S-N curves with elastic FEA
Sa
Sm
00 UTS
local
notched
local - elastic
Strain
Str
es
s
ms
ems
as
eas
as
SS
tK
S-N curves with elastic FEA
0
50
100
150
200
0 100 200 300 400 500 600
Mean stress (MPa)
Str
ess a
mp
litu
de M
Pa Local ,e e
a ms s
Notched ,a mS S
Local ,a ms s
‘Notched – brittle’
‘Notched – ductile’
MANTEN steel
SS
tK
S-N curves with elastic FEA
0
50
100
150
0 100 200 300 400 500 600 700
Mean stress (MPa)
Str
ess a
mp
litu
de M
Pa
Local ,e ea ms s
Notched ,a mS S
Local ,a ms s
‘Notched – brittle’
‘Notched – ductile’
SS
tK
SAE1045 steel
S-N curves with elastic FEA
0
50
100
150
200
0 100 200 300 400 500 600
Mean stress (MPa)
Str
ess a
mp
litu
de M
Pa Local ,e e
a ms s
Notched ,a mS S
Local ,a ms s
‘Notched – brittle’
‘Notched – ductile’
The FKM mean stress correction diagram is an empirical estimate of this
plasticity effect
But the for complex loading the mean stresses will be wrong because
plasticity is being ignored.
FKM Guidelines Figure 4.3.3
S-N curves with elastic FEA
The FKM mean stress correction diagram is an empirical estimate of this
plasticity effect
But the for complex loading the mean stresses will be wrong because
plasticity is being ignored.
FKM Guidelines Figure 4.3.3
S-N curves with elastic FEA
• there is some yielding, even for high cycle fatigue
• there is even more yielding if the mean stresses are not zero
• yielding changes the mean stresses from cycle to cycle
Therefore the statement …...
“for high cycle fatigue there is no difference between the S-N curve and strain-life
approaches to fatigue” …...is not true
An essential feature of fatigue analysis from elastic FEA is the plasticity correction
S-N curves with elastic FEA
RESULTS
• fatigue lives and crack sites
• how much the stresses must be changed to
achieve the design life
• probability of failure at design life
• probability of survival at specified lives -
to predict warranty claims 99.7
99.8
99.9
100
1 10 100 1000 10000 100000 1000000
Miles
Su
rviv
al (%
)
User profile 1
User profile 2
• which loads need to be included during lab testing
• fatigue lives and crack sites
• how much the stresses must be changed to
achieve the design life
• probability of failure at design life
• probability of survival at specified lives -
to predict warranty claims 99.7
99.8
99.9
100
1 10 100 1000 10000 100000 1000000
Miles
Su
rviv
al (%
)
User profile 1
User profile 2
• which loads need to be included during lab testing
RESULTS
fe-safe has two methods
FRF - fatigue reserve factor
From a standard or user-defined mean stress
curve.
Applies only to infinite life design.
FOS – factor of strength for specified life or lives
An iterative process -
Scales the elastic FEA stresses
Recalculates the plasticity for the whole stress history
Recalculates the life
Repeats until it finds the scale factor to give the required life
Applies for finite and infinite life
Stress amplitude
Mean stress
RESULTS
• fatigue lives and crack sites
• how much the stresses must be changed to
achieve the design life
• probability of failure at design life
• probability of survival at specified lives -
to predict warranty claims 99.7
99.8
99.9
100
1 10 100 1000 10000 100000 1000000
Miles
Su
rviv
al (%
)
User profile 1
User profile 2
• which loads need to be included during lab testing
fe-safe combines material and load variability
Probability of survival
Uses Weibull distribution of
fatigue strength and Gaussian
variability in load values
Endurance
De
2
Loading
• Dang Van diagram
• max stress at each node
• max stress / yield stress
• max stress / UTS
• Haigh diagram, Smith diagram
• Time histories of stress tensor, principal stress/strain ...
RESULTS
Examples of fe-safe analysis
3 unit load linear elastic
FE analyses
Forged aluminium alloy suspension component
fatigue life contoursTest life : 41000 miles (long cracks)
fe-safe : 27000 miles (crack initiation)
Forged aluminium alloy suspension component
BEARING STEEL CHARACHTERISTICS
MECHANICAL
• High Hardness (HRC 58-65)
• Very High Tensile Strength (>300 ksi)
• Excellent Wear Resistance
• Excellent Rolling Contact Fatigue Endurance
Bearing-grade steel fatigue
FE METHODS
TESTING
METALLURGIC STUDY
ANALYTICAL FATIGUE ASSESSMENT
FKM-Guideline fe-safe
Bearing-grade steel fatigue
fe-safe detects contact and uses more complex analysis methods
Bearing-grade steel fatigue
Inputs for FEA/fe-safeTM analysis
• Life Theory
Brown-Miller strain-life criteria used. Trials made with
other criteria, such as Principal Stress, BM Combined,
Mises, and Principal Strain.
• Surface Effect
Default method in fe-safeTM worked well with Ra
surface finish as manufactured on the real parts.
• Material Strain-Life Properties
SAE52100 in fe-safeTM database utilized with some
modification per INA USA 52100 test data.
Tensile Test Sample with Bearing Steel
Bearing-grade steel fatigue
fe-safeTM result
Results: Weibull plot of real test data at
20KN load. L50 (test) ≈ 110K cycles.
From FEA/fe-safeTM with Brown-Miller
strain-life criteria and Morrow mean
stress correction, L50 (analysis) ≈ 92K
cycles.
Analysis results well within Weibull
confidence bands at L50.
Note wide range of real results, inherent
to bearing grade steel. (52100)
Weibull Plot of Tripod Roller Test at 20KN
Bearing-grade steel fatigue
Results: Weibull plot of real test data at
21KN load. L50 (test) ≈ 55K cycles.
From FEA/fe-safeTM with Brown-Miller
strain-life criteria and Morrow mean stress
correction, L50 (analysis) ≈ 58K cycles.
Analysis results well within Weibull
confidence bands at L50.
Note wide range of real results, inherent to
bearing grade steel. (52100)
Weibull Plot of Tripod Roller Test at 21KN
fe-safeTM result
Bearing-grade steel fatigue
Comparison of fe-safe and the „S-N + Haigh‟ method
„S-N +Haigh‟ fe-safe
Actual crack site
Fatigue life contours
fe-safe™ User‟s Group Meeting
October 14, 2008
Slide 93
• ASME B&PV (Section VIII div. 2) code design analysis procedures date to the 1960‟s
– Based on plate and shell theory (2D elastic)
– Stresses are decomposed into various classes (primary, secondary, local, thermal, membrane, bending)
– Stresses resolved on Stress Classification Lines (SCL) or “cut-lines” by linearization (analyst chooses cut-lines)
• Choosing SCL‟s and classifying stresses can be difficult and time consuming
Comparison of fe-safe and ASME B&PV
fe-safe™ User‟s Group Meeting
October 14, 2008
Slide 94
Piping Test Section
Comparison of fe-safe and ASME B&PV
fe-safe™ User‟s Group Meeting
October 14, 2008
Slide 95
0
100
200
300
400
500
600
0 20 40 60 80 100 120 140 160 180 200
Time (seconds)
Bu
lk W
ate
r T
em
pe
ratu
re (
F)
0
50
100
150
200
250
300
Test
Secti
on
Flo
w R
ate
(g
pm
)
Pre
ssu
re*1
0
(psi)
Temperature
Pressure
Flow Rate
Comparison of fe-safe and ASME B&PV
Temperature, Pressure and Flow Rate Time Histories
fe-safe™ User‟s Group Meeting
October 14, 2008
Slide 96
Cracked Spacer Ring
Comparison of fe-safe and ASME B&PV
fe-safe™ User‟s Group Meeting
October 14, 2008
Slide 97
Observations
fe-safe™ compares well with the ASME B&PV code fatigue
procedure without need of SCL‟s
…. it just works automatically
Comparison of fe-safe and ASME B&PV
Mike Otto
October 14, 2008
Fatigue Life of a Supercharger Torsion Isolator Spring
One Option: Single Spring Isolator (SSI)
SSI comprised of three “simple” parts.
Hubs are press fit to the drive shafts. The spring is captured within an internal pocket.
The spring winds and unwinds to “absorb” engine speed variation.
Spring rate is selected to isolate the supercharger from the engine‟s torsional vibrations.
Gear
Rear Hub
Spring
Front Hub
SSI comprised of three “simple” parts.
Hubs are press fit to the drive shafts. The spring is captured within an internal pocket.
The spring winds and unwinds to “absorb” engine speed variation.
Spring rate is selected to isolate the supercharger from the engine‟s torsional vibrations.
Gear
Rear Hub
Spring
Front Hub
Fatigue Life of a Supercharger Torsion Isolator Spring
Vehicle Load Signature
• The torque signature represents engine acceleration.
• High sampling frequency is required to capture “peaks” in signal.
“As Measured” Torque Signature
Fatigue Life of a Supercharger Torsion Isolator Spring
fe-safe life contours
Residual Stress: +103 MPa; fe-safe life = 67.5K cycles
Single part failed at
60K cycles.
Crack
developed
here.
Fatigue Life of a Supercharger Torsion Isolator Spring
Problem: Crack at root of
valve pocket radius
“ABAQUS and fe-safe
used to accurately predict
location and time to crack
initiation”
fe-safe fatigue contours
Crack initiation site
Federal Mogul - Modern diesel piston
Allows analysis of the surface nodes – for faster analysis
Allows stress gradient/critical distance correction from surface nodes
Allow faster fatigue solvers for surface nodes
Inner and outer surfaces indentified
fe-safe - identification of surfaces
Identifies all surfaces in a model or assembly
User can define hot-spot criteria – e.g. FOS < 1.2
„What –if‟ investigations can be applied to hotspots
Stress gradient/critical distance corrections can be applied to hot-spots
fe-safe - identification of hotspots
Identifies the fatigue „hotspots‟
Surface node
Arrow length is proportional to fatigue damage
Can be displayed for whole model or for hot-spots
fe-safe – damage vector plotting
Shows direction of crack initiation
Example from a casting simulation from Magma Abaqus fe-safe
fe-safe – property mapping
Varies the materials properties at each node
Node 1:: Material 1
Node 2 :: Material 2
Mapping model eqn
ID for each property
Node 1:: Material 1
Node 2 :: Material 2
Mapping model eqn
ID for each property
Casting simulation (Finite Difference
model)
Contour plot
of material
properties(Finite Element
model)
A property
mapping file
is generated
fe-safe uses the
mapped nodal
properties for
the fatigue life
analysis
fe-safe – wide choice of algorithms
Strain-life and stress-life
Picture
Automatic detection and analysis of surface contact
Sub-surface crack initiation…..etc
fe-safe can select the algorithm automatically, and
change algorithm in an assembly of different materials
• Network licence, WAN licencing, world-wide licencing
• Distributed processing – validated on a network of over 100
machines
• Multi-processor support – threaded code (no extra costs)
• Batch operation – with parameter modification for parametric
studies
• Save standard analyses as templates
• Can be launched from other applications (Isight, Workbench)
• Windows, Linux, Unix PCs, HP, Sun, IBM-AIX, SGI
• Includes signal processing and fatigue from strain gauges
fe-safe – system features
fe-safe FEA model files -
• Multiple FEA files can be concatenated on input
• More than 1 TerraByte of concatenated files can be input
• No limit to the number of steps and increments (validated for 220
000 steps/increments)
• No limit to the number of load cases that can be superimposed
• Can read integration point, nodal averaged or nodal data
• Can read integration point data and generate nodal averaged or
nodal data
fe-safe – system features
fe-safe plug-in algorithm allows users to write their own fatigue
algorithm
• Located in a dll
• Called for each node
• fe-safe generates the stress tensor sequence
• Supports stress, strain, temperature, time-dependency and
property mapping
• Users may add extra parameters to the materials data base
• Plug-in can be called once to initialise and read in data from
the screen or batch file if required. A GUI is auto-generated.
• Looks exactly like a native fe-safe algorithm
fe-safe – system features
Superimposed load histories
Loading
Single load history
Signal
Summary of Tests - DEF STAN 00-35
0.00001
0.0001
0.001
0.01
0.1
1 10 100 1000 10000
Hz
g2 /H
zPSD
Rainflow
cycles
Modal superimposition – steady
state and random dynamic
+
+
Sequencies of FEA solutions
Complex loading sequences
can be defined easily
Unit load stresses x load histories
superimposed
N repeats
FEA transient
analysis
- non-proportional
N2 repeats
Damage per block
0
5
10
15
20
25
30
35
40
45
1 2 3 4 5 6 7 8
Block
Da
ma
ge
(%
)
Damage for N repeats of each loading block
fe-safe – where does the damage come from?
fe-safe – is a complete system, with few add-ons
Thermo-mechanical fatigue (/TMF)
and creep-fatigue (/TurboLife)
(example – turbine blade)
Fatigue of welded joints using
the Verity method from Battelle.
Includes high temperature fatigue.
The Verity method has been adopted
by the ASME B&PV Design code
Section 8 Div II.
fe-safe – add-ons
fe-safe/composites with Helius:fatigueTM
fe-safe – add-ons
INTERFACES
Input/output
ABAQUS .fil
ABAQUS .odb
NASTRAN f06
NASTRAN op2
ANSYS .rst
I-DEAS .unv
Pro/M s01..., d01
General .csv
Output
Hypermesh .hmres
PATRAN
FEMVIEW
CADFIX
FEMAP
fefe-safe durability analysis from FEA
Redesign
Design
FEAABAQUS, ANSYS
I-DEAS,
NASTRAN, Pro/E
Stress
resultsfe-safe
Loading
Lifecontours
Maximum FEA file size is 1 Terra-byte
Key features
FAST
COMPREHENSIVE
ACCURATE
EASY TO USE
Complex loading
Safety factors
Probability analysis
Multiaxial fatigue
Cast iron analysis
Virtual strain gauges
High temperature fatigue
Welded joints
fe-safe/Rotate
fe-safe/TMF
fe-safe/TurboLife
VerityTM
module in fe-safe
fe-safe/composites with
Helius:fatigueTM
Redesign
Design
FEAABAQUS, ANSYS
I-DEAS,
NASTRAN, Pro/E
Stress
resultsfe-safe
Loading
LifecontoursWidely validated - Widely used
Selected by some hundreds of
leading engineering companies