Abstract
In this paper analysis of short cracks observed on surfaces of specimens subjected to axial, torsional, synchronous in-phase and out-of-phase as well as a number of asynchronous loadings was performed. The tests were conducted on PA38-T6 aluminum alloy, E235 non-alloy steel and 1.4301 austenitic stainless steel thin-walled specimens, in strain-control mode. It was concluded that for PA38-T6 aluminum alloy and E235 steel, fatigue cracks initiated and propagated on the plane of maximum shear strain, regardless of the loading case. Fatigue cracks observed on the surface of 1.4301 steel specimens developed predominantly on the levels of maximum normal strain. For this material, the surface condition resulting from the machining had a significant impact on the cracks growth. In the case of non-proportional loadings, at high levels of strain, cracks often propagated along the machining marks.
Highlights
Short cracks are defined as measuring less than 1 mm in length [1, 2]
Their analysis is important because the process of initiation and growth of short cracks constitutes the majority of fatigue life of the specimens
Typical short cracks observed on the surfaces of specimens made of PA38-T6 aluminum alloy were presented in Fig. 1 for all the applied loading cases
Summary
Short cracks are defined as measuring less than 1 mm in length [1, 2]. Their analysis is important because the process of initiation and growth of short cracks constitutes the majority of fatigue life of the specimens. The observations made during the research show that the occurrence of macro-cracks takes place in just the last few loading cycles. In this paper an analysis of short cracks observed on the surface of specimens made of PA38 aluminum alloy, E235 steel and 1.4301 steel has been performed. The subjects of the analysis were: a) determination of damage mechanism based on crack direction observation, and b) correlation of damage mechanism with multiaxial fatigue models, especially for the asynchronous loadings
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