The influence of alternate block loading on the fatigue lifetime

The paper presents the results of fatigue tests of cylinder specimens made of duralumin PA6 under alternate block loading for bending and torsion. Each block contains n and n cycles with sinusoidal course. Based on the fatigue curves amplitudes suitable for 105, 3·105 and 106 number of cycles to failure were determined. The loading was applied in alternate two-amplitudes blocks by 104, 3·104 or 105 each one (10% of the fatigue life for the given loading level) until failure of the specimen (fig.1).