Post on 02-May-2017
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Retrofit Engineering for Urban Infrastructures, Lecture #3
Chitoshi Miki
Fatigue Strengthof Welded Joints
Department of Civil EngineeringTokyo Institute of Technology
22
ContentsEffects of Residual Welding Stresseson Fatigue Crack Growth Rate
Size EffectsFull Size Fatigue Tests of Truss Chords
Fatigue Strength of Large-Size Gusset Jointsof 800MPa Class Steels
High Strength Steels
Longitudinal Welded Joints Containing Blowholes
Butt-Welded Joints Containing Various Embedded Defects
Effects of Weld Defects on Fatigue Strengths
33
Effects of Residual Welding Stresseson Fatigue Crack Growth Rate
Topic 1
44
Fatigue Crack Propagation Rate, da/dN
Fatigue LifeCrack Initiation Life, Ni
Crack Propagation Life, Np
Evaluation of Np
ΔK-da/dN Relationship
Affected by Residual Welding Stresses?
Experimental Investigations
55
Specimen ASpecimen B : One Longitudinal WeldingSpecimen C : Two Longitudinal Welding
I: A Crack on Base Metal
II: A Crack on Weld Metal
Specimens
800Mpa Class Steels
66
Measurements of Residual Stress
Location of Strain Gauges
2
77
Change of Residual StressDue to Crack Propagation
Half Length of Fatigue Crack (mm)
Stre
ss
(MPa
)
88
Change of Residual Stress DistributionDue to Crack Propagation
L
B-I Type Specimen
Wel
ding
L=60 mm
Stre
ss
L=0 mm
99
Change of Residual Stress DistributionDue to Crack Propagation
C-I Type Specimen
L
Wel
ding
Wel
dingSt
ress
Wide Tensile Region
1010
ΔK-da/dN Relationship (1)
L
A-I Type SpecimenNo Weld-Beads
ΔK
da/d
N
( ) 675.25.113 1071.2]/[1054.6]/[ −− ×−∆×= mmNKcyclemmdNda
Equation 1
1111
ΔK-da/dN Relationship (2)
da/d
N
ΔK
( ) 895.25.113 1037.9]/[1082.3]/[ −− ×−∆×= mmNKcyclemmdNda
A-I
OthersNo Significant Differences Between The Other Typesof Specimens
Equation 2
1212
Estimation of Fatigue Crack Propagation Life, Np
( ) 895.25.113 1037.9]/[1082.3]/[ −− ×−∆×= mmNKcyclemmdNda
( ) 675.25.113 1071.2]/[1054.6]/[ −− ×−∆×= mmNKcyclemmdNda
Penny-ShapedFatigue Crack
(Radius:a)
Welded Joint Model
Equation 2
Equation 1
3
1313
Estimation of Fatigue Crack Propagation Life, Np
Equation 1, ai=0.1
Equation 1, ai=1.0 Equation 2, ai=0.1
Equation 2, ai=1.0
Np
Δσ
1414
Effects of Weld Defects on Fatigue StrengthsLongitudinal Welded Joints
Containing Blowholes
Topic 2
1515
Welded Joint Specimen
Small Specimen
Specimens 1616
Residual Stress Distributionin The Welded Joint Specimen
1717
Classification of Blowhole Sizes
No Blowholes
Small Blowholes b < 1mm
1 mm < b < 2mmMedium Blowholes
b: Blowhole Length
Large Blowholes b > 2mm
Base on Radiographic Examination
1818
Large Blowholes
Small Blowholes
Category A
Category B
Fatigue Test Results
4
1919
Fatigue Cracks Originated From Blowholes
Radiograph Radiograph
Crack Crack Crack
2020
Fracture Surfaces with Beach Marks
2121
Fatigue CrackPropagationfrom Blowholes
2222
Fatigue CrackPropagation Ratefrom Blowholes
( ) 0.3131097.2 KdNda
∆×= −
( ) 0.3131090.0 KdNda
∆×= −
( ) 80.313 1034.81073.1 −− ×−∆×= KdNda
2323
Topic 2
Effects of Weld Defects on Fatigue StrengthsButt-Welded Joints
Containing Various Embedded Defects
2424
•Butt welded joint with V-groove
Incomplete Penetration (IP)
Lack of Fusion (LOF)
Blowhole(BH)
Slag Inclusion(SI)
Crack(CR)
Various Embedded Weld Defects
5
2525
Specimen PreparationSpecimen PreparationCutting lines
Z
X
Y
Weld defects
Specimen
Specimen
Specimen
JIS SM490A: 150 specimensJIS SM570Q: 27 specimens
JIS SM570Q567567497497DWDW--Z100Z100532532343343SM490SM490
TS(MPaTS(MPa))YP(MPaYP(MPa))
614614534534DWDW--6060660660588588SM570SM570--QQ
TS(MPaTS(MPa))YP(MPaYP(MPa))
JIS SM490A
← Detected by RT
2626
Specimen ConfigurationSpecimen Configuration
25
As-welded condition
0
500
7Root gap
R100
100 300
0
170100
4
30°
99 0
Weld bead
Uniformed section
30 °
Weld detail,V-groove
25
7
2727
Fatigue TestFatigue Test
Testing machineTesting machine–– Capacity: 300 kNCapacity: 300 kN
Testing conditionsTesting conditions–– Constant amplitudeConstant amplitude–– Stress ratio R=0Stress ratio R=0–– Maximum stress:Maximum stress:
100 100 -- 350 MPa350 MPa
Specimen
2828
Fatigue Test ResultsEvaluation : defect length “2c” is used.
Single defect Multi defects
RS(Real size
measured on failure
surface)
Length 2cX
Z
2c1 2c2
RT(Xray)
WES 2805Real Size
S
S0 = 0.25 x min (c1,c2)S ≤ S0 → 2c = 2c1 + 2c2+S S > S0 → cracks are isolated
Depth 2a
2929
Fatigue Test Result, CR Type DefectFatigue Test Result, CR Type Defect(SM490A)(SM490A)
104 105 106 10760708090
100
200
300
400
Fatigue Life (cycles)
Stre
ss R
ange
(MPa
)
209
9
67
911
132328
26
40
40
15
15
15
10
210
24
29
53
CJSSC-class => D
2
B A
RTRTToeToe
RSRSDefectDefect
lengthlengthinitiationinitiation
3030
Fatigue Test Result, IP Type DefectFatigue Test Result, IP Type Defect(SM490A)(SM490A)
104 105 106 10760708090
100
200
300
400
Fatigue Life (cycles)
Stre
ss R
ange
(MPa
)
611
8.513
22
34.5
34.5 2440
30
30
30
297 15
40
2
40
2
2
2 8
21
21.5
CJSSC-class =>D
1026 2025
AB
RTRTToeToe
RSRSDefectDefect
lengthlengthinitiationinitiation
6
3131
Fatigue Test Result, LOF Type DefectFatigue Test Result, LOF Type Defect(SM490A)(SM490A)
104 105 106 10760708090
100
200
300
400
Fatigue Life (cycles)
Stre
ss R
ange
(MPa
)
109
6
9.5 4 4
12
127.5
8
9 6.5
11.3
8.52
11.3
6.53
4.510.5
CJSSC-class =>D AB
RTRTToeToe
RSRSDefectDefect
lengthlengthinitiationinitiation
3232
Fatigue Test Result, SI Type DefectFatigue Test Result, SI Type Defect(SM490A)(SM490A)
104 105 106 10760708090
100
200
300
400
Fatigue Life (cycles)
Stre
ss R
ange
(MPa
)
8.55
15
1521
2324.5 16.2
7
3219
19
21
21
2121
13 18
21
216
121325
CJSSC-class => D
19
19
8
B A
RTRTToeToe
RSRSDefectDefect
lengthlengthinitiationinitiation
3333
Fatigue Test Result, BH Type Fatigue Test Result, BH Type Defect(SM490A)Defect(SM490A)
104 105 106 10760708090
100
200
300
400
Fatigue Life (cycles)
Stre
ss R
ange
(MPa
)
10 55
14
14
2
2
162 4
4
3
12511
2
2 311
CJSSC-class => D B A
RTRTToeToe
RSRSDefectDefect
lengthlengthinitiationinitiation
3434
High Strength SteelsFatigue Strength of Large-Size Gusset Joints
of 800MPa Class Steels
Topic 3
3535
Types of Gusset JointsTypes of Gusset Joints3636
SpecimensSpecimens
In-Plane Gusset
Out-of-Plane Gusset
7
3737
Welding Details of SpecimensWelding Details of Specimens
In-PlaneGusset
Out-of-PlaneGusset
3838
The Used SteelsThe Used Steels
HT80, SM570Q
3939
Stress Distribution at the End of Stress Distribution at the End of the Inthe In--Plane GussetsPlane Gussets
4040Stress Distribution at the End of Stress Distribution at the End of the Outthe Out--ofof--Plane GussetsPlane Gussets
4141
Fatigue Test Results Fatigue Test Results 4242
Fatigue Test Results Fatigue Test Results
In-PlaneIn-Plane
Effects of FinishingIn-Plane : Lower
8
4343
Fatigue Crack in InFatigue Crack in In--Plane Gusset Joints Plane Gusset Joints
Fatigue Strength:Category B
4444
Fatigue Crack in InFatigue Crack in In--Plane Gusset Joints Plane Gusset Joints
Fatigue Strength:Category A
4545
Fatigue Crack in InFatigue Crack in In--Plane Gusset Joints Plane Gusset Joints
Fatigue Strength:Category C and D
4646
Fatigue Crack in OutFatigue Crack in Out--ofof--Plane Gusset Joints Plane Gusset Joints
Fatigue Strength:Category D
From Root
4747
Fatigue Strength:Category C
Fatigue Crack in OutFatigue Crack in Out--ofof--Plane Gusset Joints Plane Gusset Joints
The Unfused Partof the Root
4848
Fatigue Strength:Category E
Fatigue Crack in OutFatigue Crack in Out--ofof--Plane Gusset Joints Plane Gusset Joints
This Type was not usedin the Honshu-Shikoku BridgeProject
9
4949
Size EffectsFull Size Fatigue Tests of Truss Chords
Topic 4
5050
Importance of Size Effects
Welded joint specimen
Large scaled specimen
Real scale floor beam of the Seto Bridge
5151
Girder specimen at Lehigh University in the US
5252
Full scale box section girder specimen of the Kurushima Bridge
5353
Full Size Fatigue Tests of Truss Chords
Minato Ohashi
Constructed in 1974(235m+510m+235m)
Outside: Partially Penetrated Groove WeldsInside: Fillet Welds
The Corner Joints of Truss Chords
5454
The Full Size Specimen of Truss Chords
4 Point Bending Tests
10
5555
The Full Size Specimen of Truss Chords5656
The Used Steels
600MPa Class SteelsThickness = 40, 60mm
5757
The Welding Condition of The Corner Joints5858
Fatigue Cracks in The Corner Joints (4 Types)
Fatigue Crack from Blowhole
Fatigue Crack from Stop-and-Startof Fillet Welding
5959
Type 1 Fatigue Crack Originated from a Blowhole 6060
Type 2 The Fatigue Crack Originated fromStop-and-Start Positions
Crack
A Stop-and-Start Position
11
6161
Type 2 The Fatigue Crack Originated fromStop-and-Start Positions
6262
Type 3 Collective Fatigue CracksAt the Roots of Fillet Welds
6363
Type 4 Fatigue CracksAlong the Fillet Weld-Beads
6464
Fatigue Test Results
Size Effects
6565
Consideration of Size Effects
Change of Fatigue Design Code Joint Type
Code Class Fatigue strengthat 2 million cycles (MPa)
Old code '60 D 120Current code '92 F 65
Sleeper pad Joint Type
Code Class Fatigue strengthat 2 million cycles (MPa)
Old code '60 D 100Current code '92 F 65
Out-plane gusset (t=20mm)
Joint Type
Code Class Fatigue strengthat 2 million cycles (MPa)
Old code '60 B 150Current code '92 C 125
Longitudinal welding
Joint Type
Code Class Fatigue strengthat 2 million cycles (MPa)
Old code '60 C 126Current code '92 F 65
In-plane gusset (t=20mm)
Joint Type
Code Class Fatigue strengthat 2 million cycles (MPa)
Old code '60 D 100Current code '92 E 80
Cruciform weld
6666
References1. Chitoshi Miki, Fumio Nishino, Yasuaki Hirabayashi, Koei Takena:
Influence of Residual Welding Stress on Fatigue Crack Growth Rate,Proc. of JSCE, No.330, 1983.2.
2. Chitoshi Miki, Fumio Nishino, Yasuaki Hirabayashi, Hiroyuki Ohga:Fatigue Strength of Longitudinal Welded Joints Containing Blowholes,Proc. of JSCE, No.325, 1982.9.
3. Chitoshi Miki, Fauzri Fahimuddin, Kengo Anami: Fatigue Strength of Butt-Welded Joints Containing Various Embedded Defects, Structural Eng./Earthquake Eng., JSCE, oNo.668/I-54, 2001.1.
4. Hirosuke Shimokawa, Koei Takena, Fumio Itoh, Chitoshi Miki:Fatigue Strength of Large Gusset Joints of 800MPa Class Steels,Proc. of JSCE, Vol.2, No.1, 1985.4.
5. Hirosuke Shimokawa, Koei Takena, Makoto Fukazawa, Chitoshi Miki:A Fatigue Test on the Full-Size Truss Chord,Proc. of JSCE, No.344/I-1, 1984.4.