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C. Mani et al.
11.6.1 Quantitative Fatigue Analysis
Quantitative analysis is used to determine the slope and intercept for S-N data and also
the 95% survival probability as well as the Eurocode3 design curve parameters [16].
Basic formula used to describe the fatigue performance of material is represented by
S
m N = C
(11.1)
S—Nominal stress amplitude, and N is the number of cycles to failure. The slope
and intercept m and C can be determined by using regression analysis. Logarithm
can be taken for Eq. (11.1) to determine the unknown values.
log N = log C − m log S
(11.2)
Further, 95% survival probability has been evaluated using Eq. (11.3) where σ is
the standard error for the experimental data.
log N = log C − 1.645σ − m log S
(11.3)
Fatigue life of steel structural component especially welded steel components
is affected by major influencing factors such as geometry discontinuity, material
property and fabrication, environment, residual stress and stress range. Eurocode3
takes into consideration of the above parameters and provides the endurance limit
with the require safety margin. It uses limit state method which mainly considers
constant amplitude stress range and number of cycles to failure for designing the
curve [17]. If the number of cycles N ≤ 5 × 10
6 , fatigue strength design curve in
terms of stress range, and stress amplitude is given as follows:
σ
m
R N = σ
m
C 2 × 10
6
(11.4)
where m = 3 and σ C is the stress amplitude if N = 2 × 10
6
Similarly if the number of cycles is 5 × 10
6
≤ N ≤ 10
8 , then
σ
m
R N = σ
m
C 5 × 10
6
(11.5)
m = 5, and σ C is the stress amplitude when N = 10
8 .
Experimental conditions and results and quantitative analysis results are summarized in Table 11.3. In Table 11.3, σ C = 90 MPa when N = 2 × 10
6 . Table 11.4
shows the comparison of results using different analyses.
C. Mani et al.
11.6.1 Quantitative Fatigue Analysis
Quantitative analysis is used to determine the slope and intercept for S-N data and also
the 95% survival probability as well as the Eurocode3 design curve parameters [16].
Basic formula used to describe the fatigue performance of material is represented by
S
m N = C
(11.1)
S—Nominal stress amplitude, and N is the number of cycles to failure. The slope
and intercept m and C can be determined by using regression analysis. Logarithm
can be taken for Eq. (11.1) to determine the unknown values.
log N = log C − m log S
(11.2)
Further, 95% survival probability has been evaluated using Eq. (11.3) where σ is
the standard error for the experimental data.
log N = log C − 1.645σ − m log S
(11.3)
Fatigue life of steel structural component especially welded steel components
is affected by major influencing factors such as geometry discontinuity, material
property and fabrication, environment, residual stress and stress range. Eurocode3
takes into consideration of the above parameters and provides the endurance limit
with the require safety margin. It uses limit state method which mainly considers
constant amplitude stress range and number of cycles to failure for designing the
curve [17]. If the number of cycles N ≤ 5 × 10
6 , fatigue strength design curve in
terms of stress range, and stress amplitude is given as follows:
σ
m
R N = σ
m
C 2 × 10
6
(11.4)
where m = 3 and σ C is the stress amplitude if N = 2 × 10
6
Similarly if the number of cycles is 5 × 10
6
≤ N ≤ 10
8 , then
σ
m
R N = σ
m
C 5 × 10
6
(11.5)
m = 5, and σ C is the stress amplitude when N = 10
8 .
Experimental conditions and results and quantitative analysis results are summarized in Table 11.3. In Table 11.3, σ C = 90 MPa when N = 2 × 10
6 . Table 11.4
shows the comparison of results using different analyses.