Acoustic emission (Акустическая эмиссия)

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.