Page 203 - Biaxial Multiaxial Fatigue and Fracture

Estimation of the Fatigue Life of High Strength Steel Under ... 187

O2
w =A.
a 2E
Figure 2 shows a part of variable-amplitude histories of stress, strain and energy parameters
calculated by Eqs (3) and (6). It can be seen that the energy parameter W(t) (Fig.2d) is a sto-
chastic process with the zero expected value when the stress and strain are centred processes.
Those properties are not observed in energy W(t) (Fig.2~).

1
Ea E
Fig. 1. Interpretation of amplitude of strain energy density parameter W, = 0.50,~~

HOW SIMPLE LOADING INFLUENCES THE FATIGUE LIFE

When the full section specimens are subjected to torsion, the shear stress gradient occurs and
the fatigue strength of the material is greater than in the case of pure shearing with no stress
gradient and damage accumulated in all the bar section. Let us take into account influence of