German Wind Energy Research - stahlbau.uni-hannover.de
Transcript of German Wind Energy Research - stahlbau.uni-hannover.de
© ForWind
Rasmus Eichstädt
Prof. Peter Schaumann
Lyngby, 26.06.2017
Wind Energy Science Conference
WESC 2017
Fatigue of very large high-strength bolting
assemblies in wind turbines
Rasmus Eichstädt -
Fatigue of very large high-strength bolting assemblies in wind turbines
Outline
© DOTI/alpha ventus
High-strength bolts in wind turbines
Experimental fatigue assessment
Test results on HV-bolt sets M36 and M64
Validation of normative S-N curves
Analytical fatigue assessment
Conclusions
Rasmus Eichstädt -
Fatigue of very large high-strength bolting assemblies in wind turbines
© DOTI/alpha ventus
High-strength bolts in wind turbines
Experimental fatigue assessment
Test results on HV-bolt sets M36 and M64
Validation of normative S-N curves
Analytical fatigue assessment
Conclusions
Outline
Rasmus Eichstädt -
Fatigue of very large high-strength bolting assemblies in wind turbines
M36 M48 M64 M72
Bolted ring-flange connections in wind turbines
© DOTI/alpha ventus
Up to 200 high-strength bolt assemblies (System HV) per connection
High loads with large number of load cycles
© SENVION
Rasmus Eichstädt -
Fatigue of very large high-strength bolting assemblies in wind turbines
Preloading and hot-dip galvanizing
Nominal preload Fp,C* = 0.7 ∙ Rp0.2 ∙ Asp
High mean stress affects the fatigue
strength of bolts
Limited validation of fatigue
characteristics and normative S-N
curves for large bolt diameters
Preloading for limitation of fatigue loadss [N/mm²]
e [%]
Rupture
0.2
Rp,0.2
Rm
A
Rolled notch
N = 300.000
Hot-dip galvanizing for corrosion protection
Lower fatigue strength as uncoated
structural components
Fatigue cracks initiated at shrinkage
cracks in the zinc layer
Source: Simonsen (2015)
Rasmus Eichstädt -
Fatigue of very large high-strength bolting assemblies in wind turbines
© DOTI/alpha ventus
High-strength bolts in wind turbines
Experimental fatigue assessment
Test results on HV-bolt sets M36 and M64
Validation of normative S-N curves
Analytical fatigue assessment
Conclusions
Outline
Rasmus Eichstädt -
Fatigue of very large high-strength bolting assemblies in wind turbines
Test series for 3 boundary layer conditions:
Black bolts (B)
Normal temperature hot-dip galvanized (NT)
High temperature hot-dip galvanized (HT)
only M36
M36 and M64 HV-bolt sets (10.9), rolled before
head treatment
Fatigue tests with constant stress amplitudes
and high mean stress
Assessment of the “size effect”
M64
NT HT
NT B
B
Fatigue tests on large-size HV-bolt sets
Influence of hot-dip galvanizing
M36
Sa
S
t
1 load cycle
SmSm = 0.7 ∙ Rp0.2 = 630 N/mm2
Rasmus Eichstädt -
Fatigue of very large high-strength bolting assemblies in wind turbines
Photo
: A
lexander
Raba
1.1 m
Photo
: M
att
hia
s D
örin
g
2.1 m
M36 - tests M64 - tests
Mean load 515 kN
Testing frequency ca. 50 Hz
Over 100 specimens
Mean load 1680 kN
Testing frequency 2-4 Hz
18 specimens
High frequency pulsator Servo-hydraulic testing machine
Max:
1 MN
Max:
10 MN
Fatigue tests on large-size HV-bolt sets
Rasmus Eichstädt -
Fatigue of very large high-strength bolting assemblies in wind turbines
40
60
80
100
150
20
1.0E+04 1.0E+05 1.0E+06 1.0E+07
No
min
al str
ess a
mp
litu
de
Sa
[N/m
m²]
Load cycles N [-]
50% Survival probability
Rupture
Run-out
Mean stress Sm = 0.7 ∙ Rp0.2 = 630 N/mm²
NTB HT
Black
NT-galvanized
HT-galvanized
Decrease of fatigue strength in accordance with guideline VDI 2230
Fatigue tests on HV-bolt sets M36
approx.
- 20 %
Rasmus Eichstädt -
Fatigue of very large high-strength bolting assemblies in wind turbines
10
20
40
60
100
200
1.0E+04 1.0E+05 1.0E+06 1.0E+07
No
min
al str
ess a
mplit
ud
eS
a[N
/mm
²]
Load cycles N [-]
Ps = 50 %
Ps = 10 %
Ps = 90 %
Mean stress Sm = 0.7 ∙ Rp0.2 = 630 N/mm²
Black bolts
M36
M64
Run-outs
Survival probabilities:
Results in comparison to M36 bolts
Transition region
to endurance limitHCF - Range
5∙105
M36 M64
BB
Fatigue tests on HV-bolt sets M64
Rasmus Eichstädt -
Fatigue of very large high-strength bolting assemblies in wind turbines
10
20
40
60
100
200
1.0E+04 1.0E+05 1.0E+06 1.0E+07
No
min
al str
ess a
mp
litu
de
Sa
[N/m
m²]
Load cycles N [-]
Ps = 50 %
Ps = 10 %
Ps = 90 %
HCF - RangeTransition region
to endurance limit
Mean stress Sm = 0.7 ∙ Rp0.2 = 630 N/mm²
M36
M64
Run-outs
Survival probabilities:
NT-galvanized bolts
5∙105
M36 M64
NTNT
Fatigue tests on HV-bolt sets M64
Results in comparison to M36 bolts
Rasmus Eichstädt -
Fatigue of very large high-strength bolting assemblies in wind turbines
10
20
40
60
100
200
1,0E+04 1,0E+05 1,0E+06 1,0E+07
No
min
al str
ess a
mp
litu
de
Sa
[N/m
m²]
Load cycles N [-]
Rupture M36
Rupture M64
Rupture M48 (Marten)EC3
FAT 50
M36M48M64
Run-outs
c
c
c
M36 : 0,96 S
M48 : 0,89 S
M64 : 0,83 S
Size reduction:
Hot-dip galvanized bolts
Fatigue tests on large-size HV-bolt sets
Comparison to S-N curves from Eurocode 3
M36 M64
NTNT HT
M48
(Marten)
NT
0,25
c,red c
30S S
Rasmus Eichstädt -
Fatigue of very large high-strength bolting assemblies in wind turbines
20
40
60
100
200
ΔS (N = 2∙106) = 51,9 N/mm²
ΔSc (FAT 50, M36) = 47,8 N/mm²
1,0E+04 1,0E+05 1,0E+06 1,0E+07
No
min
al str
ess r
an
ge
ΔS
[N
/mm
²]
Load cycles N [-]
Rupture
Run-out
Ps,50%
Ps,95%
EC3 – FAT 50
(w/o reduction)
M36 HV-bolts
(tZn NT)
Regression w/
fixed slope m = 3
12 M36 M48 M64 7235
40
45
50
55
Ch
ar.
fa
tig
ue
str
en
gth
ΔS
C(N
= 2
∙10
6)
[N/m
m²]
Bolt diameter [mm]
EC 3 FAT 50
Test result
Size reduction of EC3 FAT 50
Fatigue tests on large-size HV-bolt sets
Evaluation of FAT-class and size-reduction acc. to Eurocode 3
Rasmus Eichstädt -
Fatigue of very large high-strength bolting assemblies in wind turbines
20
40
60
100
200
ΔS (N = 2∙106) = 48,4 N/mm²
ΔSc (FAT 50, M36) = 44,5 N/mm²
1,0E+04 1,0E+05 1,0E+06 1,0E+07
No
min
al str
ess r
an
ge
ΔS
[N
/mm
²]
Load cycles N [-]
Rupture
Run-out
Ps,50%
Ps,95%
EC3 – FAT 50
(w/o reduction)
M48 HV-bolts
(tZn NT)
Regression w/
fixed slope m = 3
12 M36 M48 M64 72
w/o upper HCF test level
35
40
45
50
55
Ch
ar.
fa
tig
ue
str
en
gth
ΔS
C(N
= 2
∙10
6)
[N/m
m²]
Bolt diameter [mm]
EC 3 FAT 50
Test result
Size reduction of EC3 FAT 50
Fatigue tests on large-size HV-bolt sets
Evaluation of FAT-class and size-reduction acc. to Eurocode 3
( )
Rasmus Eichstädt -
Fatigue of very large high-strength bolting assemblies in wind turbines
20
40
60
100
200
ΔS (N = 2∙106) = 48,0 N/mm²
ΔSc (FAT 50, M36) = 41,4 N/mm²
1,0E+04 1,0E+05 1,0E+06 1,0E+07
No
min
al str
ess r
an
ge
ΔS
[N
/mm
²]
Load cycles N [-]
Rupture
Ps,50%
Ps,95%
EC3 – FAT 50
(w/o reduction)
M64 HV-bolts
(tZn NT)
Regression w/
fixed slope m = 3
12 M36 M48 M64 72
w/o upper HCF test level
35
40
45
50
55
Ch
ar.
fa
tig
ue
str
en
gth
ΔS
C(N
= 2
∙10
6)
[N/m
m²]
Bolt diameter [mm]
EC 3 FAT 50
Test result
Size reduction of EC3 FAT 50
Fatigue tests on large-size HV-bolt sets
Evaluation of FAT-class and size-reduction acc. to Eurocode 3
( )
Rasmus Eichstädt -
Fatigue of very large high-strength bolting assemblies in wind turbines
M36 M64
Black bolts
Fatigue tests on large-size HV-bolt sets
Comparison to S-N curves from Eurocode 3
10
20
40
60
100
200
1,0E+04 1,0E+05 1,0E+06 1,0E+07
No
min
al str
ess a
mp
litu
de
Sa
[N/m
m²]
Load cycles N [-]
Rupture M36
Rupture M64
EC3
FAT 71
EC3
FAT 50
M36M64
M36M64
Run-outs
c
c
M36 : 0,96 S
M64 : 0,83 S
Size reduction:
0,25
c,red c
30S S
BB
Rasmus Eichstädt -
Fatigue of very large high-strength bolting assemblies in wind turbines
© DOTI/alpha ventus
High-strength bolts in wind turbines
Experimental fatigue assessment
Test results on HV-bolt sets M36 and M64
Validation of normative S-N curves
Analytical fatigue assessment
Conclusions
Outline
Rasmus Eichstädt -
Fatigue of very large high-strength bolting assemblies in wind turbines
e1,max
Fatigue calculation with local concept (strain-life)
-500
0
500
1000
1500
0,00 0,01 0,02 0,03
Loca
l str
ess σ
[N
/mm
²]
Local strain ε [-]
Local hysteresis
100
1.000
10.000
100.000
1,0E+00 1,0E+02 1,0E+04 1,0E+06 1,0E+08P
SW
T[N
/mm
²]
Load cycle number until initial crack Ni [-]
Damage parameter S-N curve (PSWT)
N(PSWT) / N(Sa, Sm)
s s e ( )SWT a m aP E
FE -Model
Nominal loading
32CrB4
Non-linear material implementation
Preloading:
monotonic material law
Cyclic loading:
cyclic stabilized material law
Base material fatigue
strain-life curve
Rasmus Eichstädt -
Fatigue of very large high-strength bolting assemblies in wind turbines
20
40
60
80
100
200
1,0E+03 1,0E+04 1,0E+05 1,0E+06 1,0E+07
No
min
al str
ess a
mp
litu
de
Sₐ
[N
/mm
²]
Load cycles N [-]
Initial crack (w/o relax.)
Initial crack (with relax.)
Rupture (with relax.)
Analytical:
Test
M36
(Ps,50%)
Fatigue calculation with local concept
Sm = 0.7 ∙ Rp0.2 B
Initial crack
Initial crack
with cyclic
relaxation
Crack
propagation
until rupture
(additional)
Local str
ess σ
Local strain ε
Rasmus Eichstädt -
Fatigue of very large high-strength bolting assemblies in wind turbines
20
40
60
80
100
200
1,0E+03 1,0E+04 1,0E+05 1,0E+06 1,0E+07
No
min
al str
ess a
mp
litu
de
Sₐ
[N
/mm
²]
Load cycles N [-]
Initial crack (w/o relax.)
Initial crack (with relax.)
Rupture (with relax.)
Analytical:
Test
M36
(Ps,50%)
Sm = 0.7 ∙ Rp0.2
Fatigue calculation with local concept
Effect of hot-dip
galvanizing is not
covered in analytical
approach!
NT
Rasmus Eichstädt -
Fatigue of very large high-strength bolting assemblies in wind turbines
© DOTI/alpha ventus
High-strength bolts in wind turbines
Experimental fatigue assessment
Test results on HV-bolt sets M36 and M64
Validation of normative S-N curves
Analytical fatigue assessment
Conclusions
Outline
Rasmus Eichstädt -
Fatigue of very large high-strength bolting assemblies in wind turbines
Fatigue capacity of high-strength, large-size bolts significantly
affected by hot-dip galvanizing
EC 3 fatigue class FAT50 confirmed for bolts up to diameter M64
Size reduction necessary, better fatigue classification of uncoated
bolts must be seen critically
Analytical calculations with local concept show good approximation
to experimental results for bolts w/o boundary layer influence
Conclusions
Rasmus Eichstädt -
Fatigue of very large high-strength bolting assemblies in wind turbines
Thank you!
Funding:
Research partner: