Page 212 - Biaxial Multiaxial Fatigue and Fracture

I96 I: LAGODA ET AL.

1 o7

1 o6

1 o5

1 o5 1 o6 1 o7

Fig5 Comparison of the calculated fatigue life with experimental data for constant amplitude
torsion
A further verification was performed for variable-amplitude tension-compression. The re-
sults of fatigue life calculations Nb,eal under uniaxial variable-amplitude tension-compression
according to Palmgren-Miner (PM) and Serensen-Kogayev (SK) hypothesis and for various
coefficients a are shown in Table 3. The table also contains the relative mean error of the cal-
culated fatigue lives according to the following equation

Fatigue damage accumulation according to the Palmgren-Miner hypothesis leads to unreal-
istic estimation of the fatigue life. The mean relative error is 942%. Taking account of the am-
plitudes of the considered energy parameter below the fatigue limit (a = 0.25) gives the mean
error 240%. The Serensen-Kogayev hypothesis gives a realistic estimation of the fatigue life.