Acoustic emission (Акустическая эмиссия) , Post-graduate (аспирант))
Acoustic emission (Акустическая эмиссия) , Post-graduate (аспирант))
Moscow State Technical University
named after Bauman
Essay
Acoustic Emission
Post-graduate Golenkov
N.S.
English Teacher Kislova
V.M.
Moscow
2001
The appearance of new technologies as well as the
perfection of traditional ones is mostly based on the results of research in
the fields of solid physics, quantum mechanics, physical chemistry and other
fundamental disciplines. That is why perspective methods of technological
diagnostic must have an advanced trend of development comparing to the
development of new structure and shape forming methods.
Intensification of science research in the fields of
emission methods analysis reflects the above-mentioned matters. Emission
diagnostics methods are based on the effect of radiation of elastic deformation
waves, electrons and electromagnetic waves by studied object. Object condition
is identified registration and analysis of radiation parameters based on the
condition change can be made. The above methods represent so called inner
energy methods and have a number of advantages allied with anomalies of
material structure.
Amongst diagnostic methods the most widely spread in
field of machinery construction is an acoustic emission method based on
generation of elastic deformation waves in solid body caused by defect
development, phase transformation and other elapsing processes. Analysis of all
parameters allows to make judgement, regarding damage dynamics of material. It
is used effectively for undamaging control while testing and using articles.
It is necessary to mention that an acoustic emission
method is one of the newest and most prospective diagnostic methods. It is
physical nature causes expanding fields of application for the method in
technology.
First works by acoustic emission method appeared in
70s. This works fulfilled in the late 70s and early 80s are characterized by
fairly narrow range of technological tasks, connected mostly with tool wear
control.
Sources of an acoustic emission are divided into internal
and external. First ones are sources located on object’s surface. For example,
acoustic emission caused by friction, blow, turbulent fluid and gas streams.
Processes of local dynamic redistribution of tension fields in material apply to internal sources
of acoustic emission. For example, acts of plastic deformation, micro- and
macro destruction and phase transformation. Analyzing the cut zone from these
positions can make a conclusion about existence in this zone whole number of
acoustic emission sources of different power and spectral density. Acoustic
emission parameters depend on a way plastic deformation, destruction and
friction processes go. It is possible to carry out acoustic emission
diagnostic. Beside, frequency range of registration of acoustic emission
parameters usually estimates in tens, hundreds and thousands kilohertz and is
well protected from noises, which accompany work of technological equipment
units.
In many aspects the acoustic emission method reminds
those of low-frequency acoustic spectrometry, although in other aspects it is
completely different. Acoustic emission methods are a clear shown wave process
accompanied by variable space-time localization of elastic energy.
The increase of mechanical processing efficiency is
tied with search and realization of new speeding-up methods of technological
preparation for shape forming processes. Methods of rational carving conditions
determination are being developed as one of the most important tendencies in
practical use of emissive technological diagnostic means.
An important direction in the practical use of
progressive technology diagnostic methods for carving process is the quality
analysis of surface detail layer during the processing. The quality of a
surface processed is formed as a result of friction, plastic deformation and
the destruction of ingot material in carving zone. This is the reason why
emissive process parameters must contain information regarding surface’s
condition. It is possible to use acoustic emission method to identify the
moment of contact between a tool and an ingot.
Thus, as shown by preliminary analysis, the acoustic
emission method has great technological potential, which needs to be yet
studied. The lack of knowledge regarding method’s opportunities constrains its
effective use in theory and practice of mechanical carving of materials.