Fatigue behavior of bolted boreholes under various preloads

Abstract

Abstract Bolted joints are one of the most used joining technologies in engineering. It is possible to join different kind of materials and to transmit heavy loads. Nevertheless, they are vulnerable to fatigue cracks. The present research investigates the dependency between the preload of the bolt and the initiation of a fatigue crack in the bolted sheet. Therefore, a representative bolt connection with a bolt of size M22 was selected in combination with a 5 mm thick sheet made of steel S355MC (1.0976). The bolted sheet was loaded by a fluctuating tension load and a load ratio of 0.1. The test results show a strong correlation of the preload and the number of load cycles to crack for preloads from 0 kN to 30 kN. The load cycles to crack are increased by about factor 20 by using a preload in contrast to the sheet without any preload. For higher preloads, the load cycles to crack does not change considerably. However, the crack initiation location changes by increasing the preload. For small preloads, the crack starts at the bolt hole, and for high preloads, the crack starts at the fretting zone.