FATIGUE CRACK GROWTH IN AlCu4Mg1 UNDER NON-PROPORTIONAL BENDING WITH TORSION LOADING

摘要

The paper presents the experimental results of fatigue crack growth on AlCu4Mg1 aluminium alloy under proportional and non-proportional bending with torsion obtained at Opole University of Technology. Specimens with square sections and stress concentrations in the form of external one-sided sharp notches were used. The tests were performed in the high cycle fatigue regime for the stress ratio R = -1 and phase shift between bending and torsion loading equal to Φ = 0; 45° and 90°. Three paths of loading were used: line, ellipse and circle. The fatigue crack growth was cyclically measured with use of the optical microscope (magnification of 25 times), strain gauges and computer allow to register signals of loading. In the tested specimens, it was possible to observe growth of cracks conforming with mixed mode I + III. The crack growths were non-uniform at both sides of the specimen surface, however the difference between crack lengths was rather small. In the biaxial tests, influence of bending was six times greater because of the notches in the bending plane. The test results were described by the stress intensity factor range, ΔK.