Loosening Behavior of Ripped Nuts Based on the Fastener Tightening Strategy and Plate Hardness

Abstract

Within the scope of this study, loosening behavior under vibration was investigated depending on the plate hardness, clamp length and tightening strategy of M8x1.25 10.9 quality nuts with rip form under flange. Two different plate hardness were used and two different types of tightening strategy, i.e. application of torque to either from bolt head or nut, were carried out by using bolts with 29 mm and 40 mm clamp length. During tightening, the effects created by rips on the plate were examined. A parametric study was also carried out to understand loosening behavior of fasteners depending on the plate hardness. Based on the experimental study, it was shown that plate hardness, clamp length and tightening strategy played a key role on the loosening behavior of fasteners. To decrease the loosening rate of the assembly on softer plate, nut with rip form should be tightened from the bolt element. However, for harder plates the selection of tightening strategy was less significant compared to that of softer plate.