Evaluation of Loosening Proof Performance of Plain Washer and Flange Nut by Three-Dimensional Finite Element Analysis

• Published in: Nihon Kikai Gakkai ronbunshū. A Vol. 18; no. 9; pp. 1292 - 1295
• Main Authors: Izumi, Satoshi, Kimura, Masatake, Sakai, Shinsuke
• Format: Journal Article
• Language: Japanese
• Published: 01.09.2006
• ISSN: 0387-5008

Threaded fasteners are widely used in mechanical structures since the disassembly for maintenance is easy and low cost. However vibration-induced loosening due to dynamic loading has remained to be problematic. Various kinds of anti-loosening components such as spring washer, flange nut and double nut have been proposed and used in order to prevent loosening. In this paper we have evaluated the loosening proof performance of plain washer and flange nut under the condition of shear loading by three-dimensional finite element analysis. As for the loosening induced by bearing-surface slip, it is found that both plain washer and flange nut show no loosening proof performance. As for the loosening induced by micro bearing-surface slip, the plain washer shows lower critical loosening load and higher loosening rate, as compared with conventional nut. Although the critical load of flange nut is similar with that of conventional nut, the loosening rate is smaller. Therefore, it can be concluded that plain washer and flange nut show negative and positive loosening proof performance, respectively. It is also found that critical slip width Scr is not suitable for the evaluation of the loosening under force-controlled loading condition. In order to evaluate the loosening proof performance, critical loosening load and loosening rate must be investigated from the viewpoints of both bearing-surface slip and micro bearing-surface slip.