The New Jersey Institute of Technology's
Electronic Theses & Dissertations Project

Title:	Destructive disassembly of bolts and screws using impact
Author:	Pak, Kyung Geun
View Online:	njit-etd2002-051 (xi, 85 pages ~ 5.4 MB pdf)
Department:	Department of Mechanical Engineering
Degree:	Doctor of Philosophy
Program:	Mechanical Engineering
Document Type:	Dissertation
Advisory Committee:	Sodhi, R. S. (Committee chair) Caudill, Reggie J. (Committee member) Chen, Rong-Yaw (Committee member) Das, Sanchoy K. (Committee member) Singh, Pushpendra (Committee member)
Date:	2002-05
Keywords:	Destructive disassembly Mechanical impact Stress wave Elastic wave
Availability:	Unrestricted
Abstract:	Disassembly, the process of separating parts or components at the end of their useful life is complex due to a variety of fastener shapes and variability in their damage during use. As a natural solution, mechanical impact has been suggested as a cost-effective method for destructive disassembly of joining elements. The objective of this research is to improve the efficiency of impact disassembly process by studying the characteristics of elastic waves caused by impact. This research presents a new method for increasing the shear stress applied on the bolt head without increasing the energy input invested on launching striker. The equations are developed for the elastic waves in one-dimensional bar that transfers the impact energy to a protruded bolt head mounted on an infinite elastic medium or structure. These equations represent the stress wave for each period when the stress wave caused by impact travels back and forth between the struck end and the other end that is in contact with the bolt head mounted on an elastic body. The equations determine the impact load exerted on the bolt head and also the impact force generated to shear-off the bolt head. Since these equations are developed based on the assumption that the stress waves reflect at the bolt-contacting surface with a constant ratio, the reflection characteristics significantly affect the precision of the analysis. The reflection characteristics from a bolt head are found to be more complex than expected, and they affected the experimental result deviate from the analytical result.