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7/25/2019 12 AUDI Haffner Engl
1/23
P. Haffner N/EL-331.Mai 2001
FatigueFatigue lifelife predictionprediction of MIG -of MIG -WeldedWeldedAluminiumAluminium StructuresStructures
1. Virtual fatigue life prediction in developement of Aluminium Space Frames
5. Summary
Analysis methods and its influence in car frame concept developement
Difficulties in usage of virtual fatigue life prediction methods
3. One step testing in correlation to FEMFAT WELD analysis
T-joint specimen
H-specimen
Peeling-specimen
4. FEMFAT WELD damage analysis in correlation to real car frame testing
Longitudinal Side Vertical testing in relation to the Audi A2
2. Main tasks for fatigue life analysis in the Aluminum Space Frame
Material combinations and joining techniques
7/25/2019 12 AUDI Haffner Engl
2/23
P. Haffner N/EL-331.Mai 2001
FatigueFatigue lifelife predictionprediction of MIG -of MIG -WeldedWeldedAluminiumAluminium StructuresStructures
Virtual fatigue life prediction in developement of Aluminium Space Frames
Analysis methods and its influence in car frame concept developement
Prediction poignancy of FE - Methods is improving steadily
Predictions from crash-, dynamics- and stress analysis have become a major influence on the
construction of modern car frames
The bandwidth between optimised function compliance and structural reserves is getting smaller
Predictions of fatigue life for the complete car frame come mostly from real car testings, like actual
driving tests or testing rigs
Aim:Integration of the virtual fatigue life prediction methods into the early developement process
7/25/2019 12 AUDI Haffner Engl
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P. Haffner N/EL-331.Mai 2001
FatigueFatigue lifelife predictionprediction of MIG -of MIG -WeldedWeldedAluminiumAluminium StructuresStructures
Difficulties in usage of virtual fatigue life prediction methods:
Bg effort required to create accurate FE - models and the emulation of joining techniques
Emulation of the boundary conditions
- Modelling of the interface areas to the axis system
- Transmission of the load- time dependencies from wheel to frame
- Definition of the load input locations in the Space Frame model
Virtual fatigue life prediction in developement of Aluminium Space Frames
- Definition of the bearing block location in the Space Frame model
7/25/2019 12 AUDI Haffner Engl
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7/25/2019 12 AUDI Haffner Engl
5/23
P. Haffner N/EL-331.Mai 2001
FatigueFatigue lifelife predictionprediction of MIG -of MIG -WeldedWeldedAluminiumAluminium StructuresStructures
Connection to the longitutinal beam
Example: Shock absorber connection area, Audi A2 (current state)Main tasks for fatigue life analysis in the Aluminium Space Frame
Casting parts
MIG welding
7/25/2019 12 AUDI Haffner Engl
6/23
P. Haffner N/EL-331.Mai 2001
FatigueFatigue lifelife predictionprediction of MIG -of MIG -WeldedWeldedAluminiumAluminium StructuresStructures
One step testing in correlation to FEMFAT WELD analysis
Fatigue testing on T-joint-specimen
T - joint
7/25/2019 12 AUDI Haffner Engl
7/23
P. Haffner N/EL-331.Mai 2001
FatigueFatigue lifelife predictionprediction of MIG -of MIG -WeldedWeldedAluminiumAluminium StructuresStructures
Profile cross sections used in the testings
One step testing in correlation to FEMFAT WELD analysis T - joint
7/25/2019 12 AUDI Haffner Engl
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P. Haffner N/EL-331.Mai 2001
FatigueFatigue lifelife predictionprediction of MIG -of MIG -WeldedWeldedAluminiumAluminium StructuresStructures
F
clamped boundarys
Welding area
a
b
a
b
FE - Model and weld definition
Element edge length 5mm
R = 1 mm
aT-joint weld
bbutt weld
One step testing in correlation to FEMFAT WELD analysis T - joint
Edge Element thickness increased
for profile P2
7/25/2019 12 AUDI Haffner Engl
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P. Haffner N/EL-331.Mai 2001
FatigueFatigue lifelife predictionprediction of MIG -of MIG -WeldedWeldedAluminiumAluminium StructuresStructures
0
5
10
15
20
25
30
35
40
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170
Knotennummern
V
onMisesSpannunegen[M
Pa]
.
P2
P3
Profilform : P2
Profilform : P3
Nodal stresses v. Mises
Results of NASTRAN stress analysis
Bending stress amplitude = 40 MPa
T - jointOne step testing in correlation to FEMFAT WELD analysis
7/25/2019 12 AUDI Haffner Engl
10/23
P. Haffner N/EL-331.Mai 2001
FatigueFatigue lifelife predictionprediction of MIG -of MIG -WeldedWeldedAluminiumAluminium StructuresStructures
FEMFAT WELD damage plot Crack initiation area in testingOne step testing in correlation to FEMFAT WELD analysis
Bending stress amplitude = 40 MPa
Cycles to Failure = 900
Maximum damage = 1.0
Model : R = 1 mm Profil P3
Standard element edge length 5mm
Stress ratio = -1
T - joint
7/25/2019 12 AUDI Haffner Engl
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P. Haffner N/EL-331.Mai 2001
FatigueFatigue lifelife predictionprediction of MIG -of MIG -WeldedWeldedAluminiumAluminium StructuresStructures
Testing results in correlation to FEMFAT WELD Damage analysisOne step testing in correlation to FEMFAT WELD analysis
Aluminium T-Sto Verbindung
1
10
100
1,00E+01 1,00E+02 1,00E+03 1,00E+04 1,00E+05 1,00E+06 1,00E+07
Anrischwingspielzahl Na
Biege
nennspannungsamplitude
s
[MPa]
P3
P2
Versuchsergebnisse P2, P3
FEMFAT-Ergebnisse
testing results P2, P3
FEMFAT WELD results
cycles to failure
bend
ingstressamplitude
[MPa]
Aluminium t-joint specimen
T - joint
7/25/2019 12 AUDI Haffner Engl
12/23
P. Haffner N/EL-331.Mai 2001
FatigueFatigue lifelife predictionprediction of MIG -of MIG -WeldedWeldedAluminiumAluminium StructuresStructures
H - specimenOne step testing in correlation to FEMFAT WELD analysis
7/25/2019 12 AUDI Haffner Engl
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P. Haffner N/EL-331.Mai 2001
FatigueFatigue lifelife predictionprediction of MIG -of MIG -WeldedWeldedAluminiumAluminium StructuresStructures
Load application
Overlap weldMIG 3x50 mm
H - specimenOne step testing in correlation to FEMFAT WELD analysis
clamped boundary on bottom side
7/25/2019 12 AUDI Haffner Engl
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P. Haffner N/EL-331.Mai 2001
FatigueFatigue lifelife predictionprediction of MIG -of MIG -WeldedWeldedAluminiumAluminium StructuresStructures
H - specimenOne step testing in correlation to FEMFAT WELD analysis
H-Specimen: Overlap MIG Weld 3x50mm
Material: A6009
Comparison of Mean Stress infuence
1,00E+04
1,00E+05
1,00E+02 1,00E+03 1,00E+04 1,00E+05 1,00E+06
Cycles
LoadAmplitude
(N)
r = -1
r = 0.1
testing (r = 0.1)
k = 4.06
k = 4.00
k = 4.04
cycles to failure
loadamplitude
[N]
Testing results in correlation to FEMFAT WELD damage analysis
7/25/2019 12 AUDI Haffner Engl
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P. Haffner N/EL-331.Mai 2001
FatigueFatigue lifelife predictionprediction of MIG -of MIG -WeldedWeldedAluminiumAluminium StructuresStructures
Overlap weld
Load application
clamped boundary
Peeling - specimenOne step testing in FEMFAT WELD analysis
7/25/2019 12 AUDI Haffner Engl
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P. Haffner N/EL-331.Mai 2001
FatigueFatigue lifelife predictionprediction of MIG -of MIG -WeldedWeldedAluminiumAluminium StructuresStructures
Peeling - specimenOne step testing in FEMFAT WELD analysis
Peeling specimen: Overlap MIG Weld
Material: AlMgSiMn
Comparison of Mean Stress influence
1,00E+02
1,00E+03
1,00E+04
1,00E+02 1,00E+03 1,00E+04 1,00E+05 1,00E+06
Cycles
LoadAmplitude
(N)
r = -1
r = 0.1
k = 4.62
k = 4.45
loadamplitude
[N]
cycles to failure
Results from FEMFAT WELD damage analysis
7/25/2019 12 AUDI Haffner Engl
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P. Haffner N/EL-331.Mai 2001
FatigueFatigue lifelife predictionprediction of MIG -of MIG -WeldedWeldedAluminiumAluminium StructuresStructures
6 Hydrolic cylinders
Car frame clamped
Springs/damper as
rigid beams
Testing VA, HA
Driving measurement
Forces, Moments on the wheel
Fk(t), M k (t), k=x,y,z
Testing rig configuration
Longitudinal Side Vertical testing (LSV)
Car frame testing
7/25/2019 12 AUDI Haffner Engl
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P. Haffner N/EL-331.Mai 2001
FatigueFatigue lifelife predictionprediction of MIG -of MIG -WeldedWeldedAluminiumAluminium StructuresStructures
Overlap weld
T-joint weld
Car frame interface
areas
FZ, MZ
FX, MX
FY, MY
Load- time
dependencies
in wheel mid-point
FEMFAT WELD damage analysis in correlation to real car frame testing Audi A2(early state of
developement)
7/25/2019 12 AUDI Haffner Engl
19/23
P. Haffner N/EL-331.Mai 2001
FatigueFatigue lifelife predictionprediction of MIG -of MIG -WeldedWeldedAluminiumAluminium StructuresStructures
Overlap weld
T-joint weld
Car frame interface
areas
FZ, MZ
FX, MX
FY, MY
Load- time
dependencies
in wheel mid-pointCrack prediction from FEMFAT WELD
FEMFAT WELD damage analysis in correlation to real car frame testing Audi A2(early state of
developement)
7/25/2019 12 AUDI Haffner Engl
20/23
P. Haffner N/EL-331.Mai 2001
FatigueFatigue lifelife predictionprediction of MIG -of MIG -WeldedWeldedAluminiumAluminium StructuresStructures
Crack predicton from FEMFAT WELD
FEMFAT WELDFEMFAT WELD damagedamagePlotPlot
Fatigue life prediction < 200 km EVP
ca. 4000 km normal driving
FEMFAT WELD damage analysis in correlation to testing reults
FEMFAT WELD damage analysis in correlation to real car frame testing
cracks on MIG- welds
Testing resultsTesting results
Fatigue life ca. 8000 km EVP
ca. 160000 km normal driving
Audi A2(early state of
developement)
F iF ti liflif di idi ti f MIGf MIG W ld dW ld d Al i iAl i i SSt t
7/25/2019 12 AUDI Haffner Engl
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P. Haffner N/EL-331.Mai 2001
FatigueFatigue lifelife predictionprediction of MIG -of MIG -WeldedWeldedAluminiumAluminium StructuresStructures
Shock absorber connection area optimised for fatigue Audi A2(current state)
The optimisation in the welding areas is done by the classic stress analysis
Real testings were nessecary for cross validation
The FEMFAT WELD prediction poingnancy was comparable to a vertical load stressanalysis at the shock absorber connection
F tiF ti liflif di tidi ti f MIGf MIG W ld dW ld d Al i iAl i i St tSt t
7/25/2019 12 AUDI Haffner Engl
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P. Haffner N/EL-331.Mai 2001
FatigueFatigue lifelife predictionprediction of MIG -of MIG -WeldedWeldedAluminiumAluminium StructuresStructures
Summary
One step testing
Damage locations are correctly identified
Fatigue life prediction until crack initiation is on the conservative side
Predictions with mean stress influence lead, in some cases, to disproportional results
This effect is more noticable under peeling conditions than under shear tension
Car frame testing
The location of first crack initiation can be identified with relatively high confidence
Other real crack locations are also able to be predicted using FEMFAT WELD
However, not all cracks can be identified
There are also cracks identified with FEMFAT WELD, that are not problematic in real testings
Absolute fatigue life predictions with FEMFAT WELD for particular weldings are extremly conservative
F tiFatig e liflife di tiprediction f MIGof MIG W ld dWelded Al i iAl mini m St tStr ct res
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P. Haffner N/EL-331.Mai 2001
FatigueFatigue lifelife predictionprediction of MIG -of MIG -WeldedWeldedAluminiumAluminium StructuresStructures
For the FEMFAT WELD tool to be as powerful as crash simulation
in the Space frame concept developement, it is required to get the
prediction much closer to the real fatigue life time
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