Fatigue Strength of Screwed Fastenings in Thin Sheet Components

The paper is concerned with the analysis of the behaviour of screwed fastenings subjected to repeated loading that can lead to fatigue. Earlier experiments have shown that, in the process of repeated loading, considerable discrepancies in the behaviour of identical fastenings can be observed which cannot always be accounted for in terms of loading data alone. It is postulated that these discrepancies are due to the different character of the development of plastic deformations in the process of loading which determines whether the failure observed is caused by
-high-cyclic fatigue
-low-cyclic fatigue
-an increase of plastic deformations
This relation also has significant consequences for the experimental establishment of the design strength of a fastening, because it determines whether the approach ‘from above’ (reduction of the ultimate strength) or ‘from below’ (limitation of the plastic allowable deformation) should be chosen. The theoretical interpretation is verified by the author’s experiments.

M. Strnad