International Journal of Machine Tools & Manufacture 42 (2002) 157–165
Review
A brief review: acoustic emission method for tool wear monitoring
during turning
Xiaoli Li
*
School of Electric Engineering, Yanshuan University, Qinhuandao, 066004, P.R. China
Received 27 March 2001; received in revised form 28 June 2001; accepted 12 July 2001
Abstract
Research during the past several years has established the effectiveness of acoustic emission (AE)-based sensing methodologies
for machine condition analysis and process monitoring. AE has been proposed and evaluated for a variety of sensing tasks as well
as for use as a technique for quantitative studies of manufacturing processes. This paper reviews briefly the research on AE sensing
of tool wear condition in turning. The main contents included are:
1. The AE generation in metal cutting processes, AE signal classification, and AE signal correction.
2. AE signal processing with various methodologies, including time series analysis, FFT, wavelet transform, etc.
3. Estimation of tool wear condition, including pattern classification, GMDH methodology, fuzzy classifier, neural network, and
sensor and data fusion.
A review of AE-based tool wear monitoring in turning is an important step for improving and developing new tool wear monitor-
ing methodology. 2001 Elsevier Science Ltd. All rights reserved.
Keywords: Acoustic emission; Tool wear monitoring; Turning
1. Introduction
‘Acoustic emission (AE) is the class of phenomena
whereby transient elastic waves are generated by the
rapid release of energy from a localized source or
sources within a material, or the transient elastic wave(s)
so generated’ (ANSI/ASTM E 610-77). Clearly, an AE
is a sound wave or, more properly, a stress wave that
travels through a material as the result of some sudden
release of strain energy. In recent years, AE instruments
and systems have been developed for the monitoring and
nondestructive testing of the structural integrity and gen-
eral quality of a variety of materials, manufacturing pro-
cesses, and some important devices.
Applications of AE for nondestructive testing are
found in numerous industries, including refineries, pipe-
* Present address: Institute for Production and Machine Tools,
Hannover University, Schlosswender Str. 5, 30159 Hannover, Ger-
many. Fax: +49-511-762-5115.
E-mail address: lixiaoliFhit@yahoo.com (X. Li).
0890-6955/02/$ - see front matter 2001 Elsevier Science Ltd. All rights reserved.
PII: S0890-6955(01)00108-0
lines, power generation (nuclear or other), aircraft, off-
shore oil platforms, paper mills and structures (bridges,
cranes, etc.). AE products are also used for quality con-
trol in manufacturing operations and in research appli-
cations, and have important applications involving com-
posite structures such as fiberglass, reinforced plastics
and advanced aerospace materials.
Tool wear is a complex phenomenon occurring in dif-
ferent and varied ways in metal cutting processes. Gen-
erally, worn tools adversely affect the surface finish of
the workpiece and therefore there is a need to develop
tool wear condition monitoring systems which alert the
operator to the state of tool, thereby avoiding undesirable
consequences. Various methods for tool wear monitoring
have been proposed in the past, even though none of
these methods was universally successful due to the
complex nature of the machining processes. These
methods have been classified into direct (optical, radio-
active and electrical resistance, etc.) and indirect (AE,
spindle motor current, cutting force, vibration, etc.) sens-
ing methods according to the sensors used. Recent