Protective Approach against Looseness of Screw Fastening due to Impingement of Stress Wave

Abstract

Experience has shown that loosening occurs, when stress wave and vibration are emitted to the screw fastening system, even if the tightening is sufficient. In order to clarify the cause of the looseness, the stress wave emitted from bolt shank which constitutes the screw fastening system is made to impinge to engagement conjunction of screw thread, and the problem of the loseness has been studied experimentally. It was proven that seperating the engagement of screw thread of the bolt and nut by the stress wave was one of the causes of the loseness. This paper studies the looseness by emitting stress wave from both of the bolt and the nut. Noticing that soft materials have buffer effect for the impact, the prevention of the looseness is studied by using the soft washer in the screw fastening system.