Issue 58

S. Çal ı ş kan et al.ii, Frattura ed Integrità Strutturale, 25 (2021) 344-364; DOI: 10.3221/IGF-ESIS.58.25



1/



n

   

   



 i x n 1

i





(17)

        1 αГ 1 



(18)

1/2

 

  

  

  

2

2

 2

   

 

(19)

Г 1



Figure 8: Weibull distribution of staircase data based on Newton Rapson technique.

Mean value and standard deviation can be estimated 584.13 and 23.64 based on Weibull distribution. JSME Method Another method used as a standard that is JSME (Japan Society of Mechanical Engineers) requiring 14 specimens for analysis and constructs whole of the SN curve. Eight of them are used in linear region and six specimens are enough to determine fatigue limit of data set. First stress point is taken as highest non-failed (run-out) point in data set. Rest of them is constructed up-and-down method based on previous test result by a certain stress increment. Stress increment for staircase sequence is estimated by assuming standard deviation equals to stress increment. Linear region is associated with following parameters:     log α β * N S (20)                8 1 8 2 1 *(log log ( ) i i i i i S S N N S S ,        8 1 1 log log 8 i i N N and    8 1 1 8 i i S S (21)

Mean and standard deviation can be estimated with given equations:

   7 2 1 6 j

S

S

(22)

j

 8

1 1 ( log(





2

  S

    





s

N

(23)

log

i

i



6



i

1

After calculation, mean and standard deviation were calculated as 583.3 and 26.01 respectively.

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