The generation mechanisms of acoustic emission in metal cutting
type: CreativeWork
description: The objective of the present thesis is the investigation of the generation mechanism of the ultrasonic vibrations, commonly called acoustic emissions (AE), detected during the course of metal cutting, since, although quite a lot of research effort has been put into the use of AE to monitor metal cutting condition, the mechanism by which AE is generated is still not fully understood. If chip generation is continuous, without built-up edge, and a sharp tool is used, continuous type AE is normally assumed. Most published models relate the energy of AE to the total cutting power, but this can be shown to be rather incorrect. Consequently, as continuous-type AE is mostly generated due to plastic deformation, and as dislocation motion is the main mechanism of plastic deformation of metals, a relationship between AE and dislocation motion is developed for the typical plastic deformation regimes encountered in metal cutting (due to the high temperatures, flow stress decreases with temperature in the so-called diffusion controlled regime, and due to the high strain rates, opposing viscous damping becomes the dominant mechanism governing dislocation movement). Although viscous damping governs the mechanics of deformation in metal cutting, it is proposed that AE is generated due to the interaction between dislocations and obstacles, since as a dislocation approaches an obstacle, strain energy is stored, which is rapidly released as soon as the dislocation surmounts the obstacle, resulting in the emission of an AE event. The detected AE is a result of many consequential likewise events. Consequently, a qualitative original model of AE generation is developed, in which the energetic level of AE is predicted to increase with strain and strain rate, but decrease with temperature, and the frequency content of AE is predicted to increase with strain rate, decrease with temperature, and remain unchanged with strain. In order to access the validity of the above-mentioned model, two se…
abstract: The objective of the present thesis is the investigation of the generation mechanism of the ultrasonic vibrations, commonly called acoustic emissions (AE), detected during the course of metal cutting, since, although quite a lot of research effort has been put into the use of AE to monitor metal cutting condition, the mechanism by which AE is generated is still not fully understood. If chip generation is continuous, without built-up edge, and a sharp tool is used, continuous type AE is normally assumed. Most published models relate the energy of AE to the total cutting power, but this can be shown to be rather incorrect. Consequently, as continuous-type AE is mostly generated due to plastic deformation, and as dislocation motion is the main mechanism of plastic deformation of metals, a relationship between AE and dislocation motion is developed for the typical plastic deformation regimes encountered in metal cutting (due to the high temperatures, flow stress decreases with temperature in the so-called diffusion controlled regime, and due to the high strain rates, opposing viscous damping becomes the dominant mechanism governing dislocation movement). Although viscous damping governs the mechanics of deformation in metal cutting, it is proposed that AE is generated due to the interaction between dislocations and obstacles, since as a dislocation approaches an obstacle, strain energy is stored, which is rapidly released as soon as the dislocation surmounts the obstacle, resulting in the emission of an AE event. The detected AE is a result of many consequential likewise events. Consequently, a qualitative original model of AE generation is developed, in which the energetic level of AE is predicted to increase with strain and strain rate, but decrease with temperature, and the frequency content of AE is predicted to increase with strain rate, decrease with temperature, and remain unchanged with strain. In order to access the validity of the above-mentioned model, two se…
author: de Melo Martins Araújo, António João
language: eng
date published: 2006
date modified: 2026-07-24T04:38:46Z
provider: University of South Wales
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of South Wales