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Fatigue strength of non-load-carrying cruciform welded joints by a test maintaining maximum stress at yield strength
Enaineerina _ _ Fracture Mechanics Vol. 49, No. 4, no. 639-645, 1994
Pergamon
Copyright 0 1994 El&ier Science Ltd Printed in Great Britain. All rights reserved 0013-7944/94 $7.00 + 0.00
0013-7944(94)00122-7
TECHNICAL
NOTE
FATIGUE STRENGTH OF NON-LOAD-CARRYING CRUCIFORM WELDED JOINTS BY A TEST MAINTAINING MAXIMUM STRESS AT YIELD STRENGTH AKIHIKO
OHTAt,
TNational
KAZUYOSHI
MATSUOKAf,
NAOYUKI
SUZUKIt
and YOSHIO
MAEDAt
Research Institute for Metals, 2-3-12, Nakameguro, Meguro-ku, Tokyo 153, Japan, fShip Research Institute, 6-38-1, Shinkawa, Mitaka-shi, Tokyo 181, Japan
Abstract-The fatigue strength
of transverse non-load-carrying cruciform welded joints of SMSOB steel has been investigated by R = 0 test and omrr = oy test which simulates the tensile residual stress exists in real welded structures. The plate thickness was 20 mm and 40 mm. The residual stress, or, at the weld toe was about 40% of the yield strength for 20 mm thick joints and 100% of the yield strength for 40 mm thick joints. The fatigue strength for 20 mm thick joints by R = 0 test was superior to that for other occurred from the low maximum stress condition of conditions. The superior properties omar = o, + Au < oy. The coincidence of the fatigue properties for other conditions occurred from the unique maximum stress condition of rr,,, = by due to shakedown.
NOMENCLATURE Number of cycles to failure Stress ratio Maximum stress Minimum stress Residual stress Yield strength Stress range at the constant amplitude
test
INTRODUCTION THE FATIGUEstrength obtained on large sized welded beams is quite different from that on small width welded specimens at R = - 1 and R = 0 tests [I] as shown in Fig. 1. The difference occurs from the tensile residual stress [2,3]. That is, in welded beams, the tensile residual stress reaches to the yield strength of material, oy , and the fatigue strength becomes unique at various stress ratio [4]. While, in small width specimens, the residual stress is normally small, and the fatigue strength decreases with the increase of stress ratio, R (51. The design of welded structures against fatigue has to reflect the S-N cure for welded structures. In order to overcome the difference of fatigue strength between beams and small width specimens, a new testing method using small width welded specimens has been proposed [S]. In this method, the maximum applied at by. while the minimum applied stress, omln, is changed with A,o as o,,, = ay - Au; Fig. 2(a). stress, omaxr is maintained This stress condition modifies the real stress condition in welded structures. The results from this test method using small width specimens coincided with the results of large welded joint specimens which contained high tensile residual stresses of yield strength magnitude [6]. It has been pointed out [7,8] that the increase of the plate thickness brings no influence on the fatigue strength of as-welded joints when the specimens contain high tensile residual stress and satisfy the condition of or + Au 2 oy, though it exerts a harmful influence when the specimens contain low residual stress and satisfy the condition of o, + Au < by. However, there is a question [9] about the O,~~ = oy test. That is, the difference in the stress distribution along the plate thickness between the real stress of structural members and welded specimens under the e,,, = by test may induce the discrepancy in the fatigue strength, because the real stress distribution in welded structural members shows a steep gradient, while it shows rather flat in specimens under the amrx = o, test. In this note, the o,,, = uy test is applied to show that the difference in stress distribution between test conditions does not induce any change on the fatigue strength by using welded specimens in which the tensile residual stress around the weld toe reached to uy as in real structural members.
EXPERIMENTAL
DETAILS
The material used in this experiment was JIS SMSOB mild steels for welded structures. The plate thickness was 20 mm and 40 mm. The chemical composition and tensile properties of the steels are given in Tables I and 2, respectively. The
640
Technical Note
3 soE x _ 2. _
-c\
In RI-f -Small ==z 80%
Specimen Curves Confidence Interval
El Full Size Spmimen Data Points
Fig. I. Difference in fatigue strength between small specimens and fuli size specimens.
R=O
/
00’
~~ 0
O;nin’O
Time
Fig. 2. Stress patterns used in fatigue tests. (a) urnax= uY; (b) R = 0.
non-load-carrying cruciform welded joints were made by a manual arc welding with covered electrode. The welding conditions are given in Table 3. Figure 3 shows the macrostructures of specimens. The transverse fatigue specimens of 50 mm width were machined from the welded plates as shown in Fig. 4. All tests were conducted under uniaxial loading on electrohydradic Fatigue testing machines in laboratory air at room temperature. The test frequency was between 10 and 30 Hz. The stress patterns are shown in Fig. 2.
RESULTS AND DISCUSSION The residual stress distributions per~ndicular to the weld line along the plate thickness were calculated for bead welds as the sum of the inherent stress due to the shrinkage force vertical to the weld line and the stress due to the deformation by the shrinkage [7]. The result of calculation is shown in Fig. 5. The residual stress is tensile around the surface of plates, and compressive in the middle part of plates. The maximum value of o, for the 40 mm thick specimen is the yield strength of material, oY_ While, it is about 40% of ey for the 20 mm thick specimen. The fatigue crack always initiated at the weld toe due to the strain concentration. The fracture appearance for cmHx= rr, tests is similar to that for R = 0 tests except for the longer shear lip created during the final part of the test. The S-N plots are shown in Fig. 6. On 40 mm thick specimens, the results for both test conditions of Q,., = oYand R = 0 are on a unique line. In the case of 40 mm thick specimen, the tensile residual stress at the weld toe is by. That is, the imaginary maximum stress even for R = 0 test satisfied the condition of 20, > do + o, 2 o,,. In the case of G,, = cfz test, the imaginary maximum stress is always 20,. By the shakedown, the maximum stress, however, became to be uY. Thts is the reason for the coincidence of the fatigue strength of R = 0 and nmax= by tests.
Table 1. Chemical composition of SMSOB steels
Material SM5OB
Thickness _______._____ Mn I (mm) C Si 20 40
0.166 0.179
0.33 0.33
1.45 1.48
Chemical composition _______..___..______._-__-_._~____.__ P S Ni Cr MO V 0.021 0.022
O.Oll 0.012
0.01 0.01
0.01 0.01
0.01 0.01
0.026 0.027
_--__ 0
N 0.0035 0.0045 0.0035 0.0048
._ ._..__.___ C,, 0.43 0.45
Pc, 0.25 0.27
Technical Note
Fig. 3. ~~crostru~t~~~s of specmens. (a) I = 20 mm; (b) I = 40 mm
641
Technical
643
Note Table 3. Welding Process Plate thickness, f (mm) Rib plate thickness, f, (mm) leg length, I (mm) Weld length (mm) Welding rod Position Current (A) Speed (mm/set) Arc voltage (V) Heat input (MJ/m)
Table 2. Mechanical
properties
of SMSOB steel
Thickness
Yield strength
Tensile strength
I (mm)
0, (MW
on W’A)
6 (%)
397 364
534 526
31 35
20 40
Elongation
Preheating Re-drying of rod Interpass temperature (C) Number of passes tPosition
conditions
Manual arc welding with covered electrode 40 20 9
40
II 500 Low hydrogen type, JIS D5016 4 mm dia. Flat 180 2.5-3.7 2.74.2 23-26 0.99-1.76 1.16-1.36.t I.0881.41t None 350°C 1 hr 60-l 50°C 9
3x4
4x4
at weld toe.
On 20 mm thick specimens, solid triangles for R = 0 test is higher than open triangles for o,,, = uy test in the lower stress range region. The coincidence of the results between R = 0 and u,, = oy tests in the higher stress range region means that the imaginary maximum stress defined as Aa + o, is larger than uy The imaginary maximum stress of Au + ur 2 uy shakedowns to the maximum stress of uy , and gave the same fatigue strength for both of the R = 0 and the urnaX= uy tests. The difference in the fatigue strength between test conditions increased with the decrease of the stress range in the lower stress range region in which Au + ur < uy. As stated above, the difference in the imaginary stress distribution along the plate thickness between the umal = uy test and the R = 0 test does not induce any change in the fatigue strength of welded joints when the imaginary maximum stress S-N curve satisfies the condition of Au + e,z TV, and the results for the u,,, = uy test give the stress ratio independent expecting in the fatigue design code m which the tensile residual stress at the fatigue critical area is considered to be uy It is also realized that the relief of residual stress by a post weld heat treatment is not necessary for the cr_ = a, test even when the specimens contain high tensile residual stress of the yield strength magnitude, because the imagmary maximum stress of 2a, shakedowns to uy. The coincidence of the fatigue strength for 40 mm and 20 mm thick specimens for the condition of Au + cr, 2 uy is similarly observed on transverse butt-welded specimens for different plate thickness [lo] and transverse non-load-carrying cruciform welded joints without toe ground treatment [7,8]. That is, the increase of the fatigue strength with the decrease of plate thickness at the R = 0 test probably occurred from the difference of residual stress in specimens. However, the tensile residual stress in real welded members approaches uy as in the case of 40 mm thick specimen in this experiment. This suggests that the fatigue strengths for thicker welded members satisfying the condition of u, 2 uy may not decrease with the increase of the plate thickness even at R = 0 loading. It is proposed [I l] to correct the S-N curve by the modified Goodman relation considering the existence of tensile residual stress of the yield strength magnitude. The correction is performed by the following equation. &,
&,= us - Au,
(I)
where Au, is the fatigue strength at R = 0,cBis the tensile strength. Two dots-dash line is the corrected one for the tests at R = 0.This line is far below the experimental data for the condition of Au + g,z uy. As the correction is not necessary for the experimental data for the condition of Au + u, 2 uy, the correction shall induce an over conservative line.
CONCLUSIONS The urnax = uy and R = 0 tests were performed on transverse non-load-carrying cruciform welded joint specimens of JIS SMSOB steel. The following conclusions were obtained. (I) The residual stress around the surface of joints calculated from the inherent stress by the shrinkage force and the deformation by the shrinkage was tensile. The values of the residual stresses were the yield strength for 40mm thick specimen and about 40% of the yield strength for 20mm thick specimen. (2) The fatigue strength for the condition of Au + u, 2 or became unique due to the shakedown of the imaginary maximum stress as to be uy. The fatigue strength for the lower stress range tests on 20 mm thick specimen (Aa + ur < uy) was higher than that for Aa + u, 2 uy condition. (3) It is concluded that the urnax= uy test even on specimens containing high tensile residual stress of the yield strength magnitude gives the S-N curve expecting in the fatigue design code in which the tensile residual stress of welded members is considered to be uy.
644
Technical
Fig. 4. Specimen
Note
configurations
500 t=ZOmm -@Y
OY
2 5 --&
b
3 L
0
f
3 0 t
0:
-500
0
10 Distance from
Fig. 5. Residual
-500 surface
stress distributions.
of
(a)
plate,
t = 40 mm; (b) I = 20 mm.
Plate thickness, t Test condition 20mm 20mm _.*.-fR=O @~,=o)
2oL ’ 104
__*__
’ ’ ’ i””
IO5
Number
I 0 x( mm]
‘1
__+_
’ ’ ’ “l”’
of Cycles
106
to
Failure,
Fig. 6. S-N diagram
“\
’ ’ ’ Nf
““l’107
Technical
Note
645
(4) There is a possibility that the decrease of the fatigue strength with the increase of plate thickness at R = 0 test occurred from the increase of tensile residual stress at the toe of weld in the specimen. (5) The correction of S-N curve by the modified Goodman relation gave an over conservative estimation even for the results of R = 0. The correction was not necessary for the experimental data satisfying the condition of Au + cr, 2 oy.
REFERENCES [I] D. Erickson and D. Kostesa, Assessing transverse fillet weld fatigue behavior in aluminium from full-size and small-specimen data. ASTM STP 1058, 3436 (1990). [2] T. R. Gurney and S. J. Maddox, A re-analysis of fatigue data for welded joints in steel. Welding Res. fnr. 3, 1-54 (1973). [3] T. R. Gurney, Fatigue design rules for welded steel joints. Welding Inst. Res. Bull. 17, 115-124 (1976). [4] J. W. Fisher, Fatigue strength of welded A514 steel beams. Proc. Conf. Fatigue of Welded Structures, The Welding Institute, 1, 1355148 (1971). [S] A. Ohta, Y. Maeda, T. Mawari, S. Nishijima and H. Nakamura, Fatigue strength evaluation of welded joints considering high tensile residual stresses. Inf. J. Fatigue 8, 147-150 (1986). [6] H. Nakamura, S. Nishijima, A. Ohta, Y. Maeda, K. Uchino, T. Kohno, K. Toyomasu and I. Soya. A method for obtaining conservative S-N data for welded structures. J. Test. Eual. 16, 280-285 (1988). [7] K. Matsuoka, I. Takahashi, T. Yoshii, H. Iidaka and E. Fujii, Influence of plate thickness and heat input on fatigue strength of non-load-carrying fillet weld joints. J. Sot. Naval Architects Jpn 168, 509-519 (1990) [in Japanese]. [8] K. Matsuoka, I Takahashi, T. Yoshii and E. Fujii, Influence of residual stress on fatigue strength of non-load-carrying fillet weld joints. Q. J. Jpn Weld. Sot. 9, 3642 (1991) [in Japanese]. [9] Steel manufacture in Japan, problems and questions on eman = cy test and its Interlaboratory Testing Program. IIW-XIII-WG-I-38-1992, l-8 (1992). [IO] A. Ohta, T. Mawari and N. Suzuki, Evaluation of effect of plate thickness on fatigue strength of butt welded joints by a test maintaining maximum stress at yield strength. Engng. Frucfure Mech. 37, 987-993 (1990). [I l] B. F. Langer, Design of pressure vessels for low-cycle fatigue. Trans. ASME Ser. D, 84, 389402 (1962). (Received I7 October 1993)
Pergamon
Copyright 0 1994 El&ier Science Ltd Printed in Great Britain. All rights reserved 0013-7944/94 $7.00 + 0.00
0013-7944(94)00122-7
TECHNICAL
NOTE
FATIGUE STRENGTH OF NON-LOAD-CARRYING CRUCIFORM WELDED JOINTS BY A TEST MAINTAINING MAXIMUM STRESS AT YIELD STRENGTH AKIHIKO
OHTAt,
TNational
KAZUYOSHI
MATSUOKAf,
NAOYUKI
SUZUKIt
and YOSHIO
MAEDAt
Research Institute for Metals, 2-3-12, Nakameguro, Meguro-ku, Tokyo 153, Japan, fShip Research Institute, 6-38-1, Shinkawa, Mitaka-shi, Tokyo 181, Japan
Abstract-The fatigue strength
of transverse non-load-carrying cruciform welded joints of SMSOB steel has been investigated by R = 0 test and omrr = oy test which simulates the tensile residual stress exists in real welded structures. The plate thickness was 20 mm and 40 mm. The residual stress, or, at the weld toe was about 40% of the yield strength for 20 mm thick joints and 100% of the yield strength for 40 mm thick joints. The fatigue strength for 20 mm thick joints by R = 0 test was superior to that for other occurred from the low maximum stress condition of conditions. The superior properties omar = o, + Au < oy. The coincidence of the fatigue properties for other conditions occurred from the unique maximum stress condition of rr,,, = by due to shakedown.
NOMENCLATURE Number of cycles to failure Stress ratio Maximum stress Minimum stress Residual stress Yield strength Stress range at the constant amplitude
test
INTRODUCTION THE FATIGUEstrength obtained on large sized welded beams is quite different from that on small width welded specimens at R = - 1 and R = 0 tests [I] as shown in Fig. 1. The difference occurs from the tensile residual stress [2,3]. That is, in welded beams, the tensile residual stress reaches to the yield strength of material, oy , and the fatigue strength becomes unique at various stress ratio [4]. While, in small width specimens, the residual stress is normally small, and the fatigue strength decreases with the increase of stress ratio, R (51. The design of welded structures against fatigue has to reflect the S-N cure for welded structures. In order to overcome the difference of fatigue strength between beams and small width specimens, a new testing method using small width welded specimens has been proposed [S]. In this method, the maximum applied at by. while the minimum applied stress, omln, is changed with A,o as o,,, = ay - Au; Fig. 2(a). stress, omaxr is maintained This stress condition modifies the real stress condition in welded structures. The results from this test method using small width specimens coincided with the results of large welded joint specimens which contained high tensile residual stresses of yield strength magnitude [6]. It has been pointed out [7,8] that the increase of the plate thickness brings no influence on the fatigue strength of as-welded joints when the specimens contain high tensile residual stress and satisfy the condition of or + Au 2 oy, though it exerts a harmful influence when the specimens contain low residual stress and satisfy the condition of o, + Au < by. However, there is a question [9] about the O,~~ = oy test. That is, the difference in the stress distribution along the plate thickness between the real stress of structural members and welded specimens under the e,,, = by test may induce the discrepancy in the fatigue strength, because the real stress distribution in welded structural members shows a steep gradient, while it shows rather flat in specimens under the amrx = o, test. In this note, the o,,, = uy test is applied to show that the difference in stress distribution between test conditions does not induce any change on the fatigue strength by using welded specimens in which the tensile residual stress around the weld toe reached to uy as in real structural members.
EXPERIMENTAL
DETAILS
The material used in this experiment was JIS SMSOB mild steels for welded structures. The plate thickness was 20 mm and 40 mm. The chemical composition and tensile properties of the steels are given in Tables I and 2, respectively. The
640
Technical Note
3 soE x _ 2. _
-c\
In RI-f -Small ==z 80%
Specimen Curves Confidence Interval
El Full Size Spmimen Data Points
Fig. I. Difference in fatigue strength between small specimens and fuli size specimens.
R=O
/
00’
~~ 0
O;nin’O
Time
Fig. 2. Stress patterns used in fatigue tests. (a) urnax= uY; (b) R = 0.
non-load-carrying cruciform welded joints were made by a manual arc welding with covered electrode. The welding conditions are given in Table 3. Figure 3 shows the macrostructures of specimens. The transverse fatigue specimens of 50 mm width were machined from the welded plates as shown in Fig. 4. All tests were conducted under uniaxial loading on electrohydradic Fatigue testing machines in laboratory air at room temperature. The test frequency was between 10 and 30 Hz. The stress patterns are shown in Fig. 2.
RESULTS AND DISCUSSION The residual stress distributions per~ndicular to the weld line along the plate thickness were calculated for bead welds as the sum of the inherent stress due to the shrinkage force vertical to the weld line and the stress due to the deformation by the shrinkage [7]. The result of calculation is shown in Fig. 5. The residual stress is tensile around the surface of plates, and compressive in the middle part of plates. The maximum value of o, for the 40 mm thick specimen is the yield strength of material, oY_ While, it is about 40% of ey for the 20 mm thick specimen. The fatigue crack always initiated at the weld toe due to the strain concentration. The fracture appearance for cmHx= rr, tests is similar to that for R = 0 tests except for the longer shear lip created during the final part of the test. The S-N plots are shown in Fig. 6. On 40 mm thick specimens, the results for both test conditions of Q,., = oYand R = 0 are on a unique line. In the case of 40 mm thick specimen, the tensile residual stress at the weld toe is by. That is, the imaginary maximum stress even for R = 0 test satisfied the condition of 20, > do + o, 2 o,,. In the case of G,, = cfz test, the imaginary maximum stress is always 20,. By the shakedown, the maximum stress, however, became to be uY. Thts is the reason for the coincidence of the fatigue strength of R = 0 and nmax= by tests.
Table 1. Chemical composition of SMSOB steels
Material SM5OB
Thickness _______._____ Mn I (mm) C Si 20 40
0.166 0.179
0.33 0.33
1.45 1.48
Chemical composition _______..___..______._-__-_._~____.__ P S Ni Cr MO V 0.021 0.022
O.Oll 0.012
0.01 0.01
0.01 0.01
0.01 0.01
0.026 0.027
_--__ 0
N 0.0035 0.0045 0.0035 0.0048
._ ._..__.___ C,, 0.43 0.45
Pc, 0.25 0.27
Technical Note
Fig. 3. ~~crostru~t~~~s of specmens. (a) I = 20 mm; (b) I = 40 mm
641
Technical
643
Note Table 3. Welding Process Plate thickness, f (mm) Rib plate thickness, f, (mm) leg length, I (mm) Weld length (mm) Welding rod Position Current (A) Speed (mm/set) Arc voltage (V) Heat input (MJ/m)
Table 2. Mechanical
properties
of SMSOB steel
Thickness
Yield strength
Tensile strength
I (mm)
0, (MW
on W’A)
6 (%)
397 364
534 526
31 35
20 40
Elongation
Preheating Re-drying of rod Interpass temperature (C) Number of passes tPosition
conditions
Manual arc welding with covered electrode 40 20 9
40
II 500 Low hydrogen type, JIS D5016 4 mm dia. Flat 180 2.5-3.7 2.74.2 23-26 0.99-1.76 1.16-1.36.t I.0881.41t None 350°C 1 hr 60-l 50°C 9
3x4
4x4
at weld toe.
On 20 mm thick specimens, solid triangles for R = 0 test is higher than open triangles for o,,, = uy test in the lower stress range region. The coincidence of the results between R = 0 and u,, = oy tests in the higher stress range region means that the imaginary maximum stress defined as Aa + o, is larger than uy The imaginary maximum stress of Au + ur 2 uy shakedowns to the maximum stress of uy , and gave the same fatigue strength for both of the R = 0 and the urnaX= uy tests. The difference in the fatigue strength between test conditions increased with the decrease of the stress range in the lower stress range region in which Au + ur < uy. As stated above, the difference in the imaginary stress distribution along the plate thickness between the umal = uy test and the R = 0 test does not induce any change in the fatigue strength of welded joints when the imaginary maximum stress S-N curve satisfies the condition of Au + e,z TV, and the results for the u,,, = uy test give the stress ratio independent expecting in the fatigue design code m which the tensile residual stress at the fatigue critical area is considered to be uy It is also realized that the relief of residual stress by a post weld heat treatment is not necessary for the cr_ = a, test even when the specimens contain high tensile residual stress of the yield strength magnitude, because the imagmary maximum stress of 2a, shakedowns to uy. The coincidence of the fatigue strength for 40 mm and 20 mm thick specimens for the condition of Au + cr, 2 uy is similarly observed on transverse butt-welded specimens for different plate thickness [lo] and transverse non-load-carrying cruciform welded joints without toe ground treatment [7,8]. That is, the increase of the fatigue strength with the decrease of plate thickness at the R = 0 test probably occurred from the difference of residual stress in specimens. However, the tensile residual stress in real welded members approaches uy as in the case of 40 mm thick specimen in this experiment. This suggests that the fatigue strengths for thicker welded members satisfying the condition of u, 2 uy may not decrease with the increase of the plate thickness even at R = 0 loading. It is proposed [I l] to correct the S-N curve by the modified Goodman relation considering the existence of tensile residual stress of the yield strength magnitude. The correction is performed by the following equation. &,
&,= us - Au,
(I)
where Au, is the fatigue strength at R = 0,cBis the tensile strength. Two dots-dash line is the corrected one for the tests at R = 0.This line is far below the experimental data for the condition of Au + g,z uy. As the correction is not necessary for the experimental data for the condition of Au + u, 2 uy, the correction shall induce an over conservative line.
CONCLUSIONS The urnax = uy and R = 0 tests were performed on transverse non-load-carrying cruciform welded joint specimens of JIS SMSOB steel. The following conclusions were obtained. (I) The residual stress around the surface of joints calculated from the inherent stress by the shrinkage force and the deformation by the shrinkage was tensile. The values of the residual stresses were the yield strength for 40mm thick specimen and about 40% of the yield strength for 20mm thick specimen. (2) The fatigue strength for the condition of Au + u, 2 or became unique due to the shakedown of the imaginary maximum stress as to be uy. The fatigue strength for the lower stress range tests on 20 mm thick specimen (Aa + ur < uy) was higher than that for Aa + u, 2 uy condition. (3) It is concluded that the urnax= uy test even on specimens containing high tensile residual stress of the yield strength magnitude gives the S-N curve expecting in the fatigue design code in which the tensile residual stress of welded members is considered to be uy.
644
Technical
Fig. 4. Specimen
Note
configurations
500 t=ZOmm -@Y
OY
2 5 --&
b
3 L
0
f
3 0 t
0:
-500
0
10 Distance from
Fig. 5. Residual
-500 surface
stress distributions.
of
(a)
plate,
t = 40 mm; (b) I = 20 mm.
Plate thickness, t Test condition 20mm 20mm _.*.-fR=O @~,=o)
2oL ’ 104
__*__
’ ’ ’ i””
IO5
Number
I 0 x( mm]
‘1
__+_
’ ’ ’ “l”’
of Cycles
106
to
Failure,
Fig. 6. S-N diagram
“\
’ ’ ’ Nf
““l’107
Technical
Note
645
(4) There is a possibility that the decrease of the fatigue strength with the increase of plate thickness at R = 0 test occurred from the increase of tensile residual stress at the toe of weld in the specimen. (5) The correction of S-N curve by the modified Goodman relation gave an over conservative estimation even for the results of R = 0. The correction was not necessary for the experimental data satisfying the condition of Au + cr, 2 oy.
REFERENCES [I] D. Erickson and D. Kostesa, Assessing transverse fillet weld fatigue behavior in aluminium from full-size and small-specimen data. ASTM STP 1058, 3436 (1990). [2] T. R. Gurney and S. J. Maddox, A re-analysis of fatigue data for welded joints in steel. Welding Res. fnr. 3, 1-54 (1973). [3] T. R. Gurney, Fatigue design rules for welded steel joints. Welding Inst. Res. Bull. 17, 115-124 (1976). [4] J. W. Fisher, Fatigue strength of welded A514 steel beams. Proc. Conf. Fatigue of Welded Structures, The Welding Institute, 1, 1355148 (1971). [S] A. Ohta, Y. Maeda, T. Mawari, S. Nishijima and H. Nakamura, Fatigue strength evaluation of welded joints considering high tensile residual stresses. Inf. J. Fatigue 8, 147-150 (1986). [6] H. Nakamura, S. Nishijima, A. Ohta, Y. Maeda, K. Uchino, T. Kohno, K. Toyomasu and I. Soya. A method for obtaining conservative S-N data for welded structures. J. Test. Eual. 16, 280-285 (1988). [7] K. Matsuoka, I. Takahashi, T. Yoshii, H. Iidaka and E. Fujii, Influence of plate thickness and heat input on fatigue strength of non-load-carrying fillet weld joints. J. Sot. Naval Architects Jpn 168, 509-519 (1990) [in Japanese]. [8] K. Matsuoka, I Takahashi, T. Yoshii and E. Fujii, Influence of residual stress on fatigue strength of non-load-carrying fillet weld joints. Q. J. Jpn Weld. Sot. 9, 3642 (1991) [in Japanese]. [9] Steel manufacture in Japan, problems and questions on eman = cy test and its Interlaboratory Testing Program. IIW-XIII-WG-I-38-1992, l-8 (1992). [IO] A. Ohta, T. Mawari and N. Suzuki, Evaluation of effect of plate thickness on fatigue strength of butt welded joints by a test maintaining maximum stress at yield strength. Engng. Frucfure Mech. 37, 987-993 (1990). [I l] B. F. Langer, Design of pressure vessels for low-cycle fatigue. Trans. ASME Ser. D, 84, 389402 (1962). (Received I7 October 1993)