View
2
Download
0
Category
Preview:
DESCRIPTION
fati
Citation preview
1. Fatigue
Given the following 1) 2 standard deviation S-N curve,
with equations for the two parts of the curve (for S in MPa) N = 428.8 x 109 S-3 (for N < 107) and N = 525.2 x 1012 S-5 (for N 107),
2) sequential stress ranges and numbers of cycles in the table below:
Numbers of cycles / year
Stress range MPa
0.6x106 30 x106
60 25
Cycles and stress ranges
a) Calculate the fatigue damage and fatigue life using the S-N curves and Miners rule in full.
b) If both stresses are superimposed throughout every year and a peak of 60MPa stress is always accompanied by a peak in the 25MPa stress, recalculate the fatigue life using the bilinear curve.
c) Approximately calculate the fatigue damage using the 3rd/5th power weighted stress method.
Class "F2"=
1 .105 1 .106 1 .107 1 .108 1 .10910
100
Cycles to failure
Stre
ss ra
nge
(M
Pa)
Recommended