Wire Ropes Under Tensile Load - Wire Ropes: Tension, Endurance, Reliability - page 164

Then, with ( 2.104 ) the mean number of load cycles is

N 50k ¼ 5 ; 820 ; 000 :

Example 2.16: Number of load cycles Z, load collective

Data:
The data from Example 2.15 are valid again. The lower force remains constant
S lower = 30 kN. The load collective for the force range is given by

0 : 20 : 3 : 5 Part of the number of cycles w i

1 : 8 : 6 Relative force range q i

Results:
The three specific force ranges q i 2Sa = d 2 ¼ q i 125 are

125 100 75

and according to Eq. ( 2.110 ) the numbers of load cycles N 1 are

680 ; 000 1 ; 640 ; 000 5 ; 090 ; 000

The last number of load cycles—greater than 2 9 10 6 —has to be corrected. For
that, using the Eq. ( 2.111 ), the limit range of the specific tensile force is

2S aD1 = d 2 ¼ 97 : 5 N/mm 2 :

Then, according to Eq. ( 2.104 ) the corrected number of load cycles is

N 1K ¼ 10 ; 200 ; 000 :

The common number of load cycles Z 1 , at which with a certainty of 95 % at
most 1 % of the wire ropes are broken, is according to Eq. ( 2.106 )

1

Z 1 ¼ ¼ 1 ; 900 ; 000 :

0 : 2
680 ; 000 þ

0 : 3
1 ; 640 ; 000 þ

0 : 5
10 ; 200 ; 000