Acoustic emission(Акустическая эмиссия)

Moscow StateTechnical University named after BaumanEssayAcoustic EmissionPost-graduate GolenkovN.S.EnglishTeacher Kislova V.M.Moscow2001The appearance ofnew technologies as well as the perfection of traditional ones is mostly basedon the results of research in the fields of solid physics, quantum mechanics,physical chemistry and other fundamental disciplines.That is why perspective methods oftechnological diagnostic must have an advanced trend of development comparingto the development of new structure and shape forming methods.

Intensification ofscience research in the fields of emission methods analysis reflects theabove-mentioned matters. Emission diagnostics methods are based on the effectof radiation of elastic deformation waves, electrons and electromagnetic wavesby studied object.Object condition is identified registration and analysis ofradiation parameters based on the condition change can be made. The abovemethods represent so called inner energy methods and have a number ofadvantages allied with anomalies of material structure.

Amongst diagnosticmethods the most widely spread in field of machinery construction is anacoustic emission method based on generation of elastic deformation waves insolid body caused by defect development, phase transformation and otherelapsing processes.Analysis of all parameters allows to make judgement,regarding damage dynamics of material. It is used effectively for undamagingcontrol while testing and using articles.It is necessary tomention that an acoustic emission method is one of the newest and mostprospective diagnostic methods.

It is physical nature causes expanding fieldsof application for the method in technology.First works byacoustic emission method appeared in 70s. This works fulfilled in the late 70sand early 80s are characterized by fairly narrow range of technological tasks,connected mostly with tool wear control.Sources of anacoustic emission are divided into internal and external.First ones aresources located on object s surface.

For example, acoustic emission caused byfriction, blow, turbulent fluid and gas streams. Processes of local dynamicredistribution of tension fields in material apply to internal sources ofacoustic emission.For example, acts of plastic deformation, micro- and macrodestruction and phase transformation. Analyzing the cut zone from thesepositions can make a conclusion about existence in this zone whole number ofacoustic emission sources of different power and spectral density.

Acousticemission parameters depend on a way plastic deformation, destruction andfriction processes go. It is possible to carry out acoustic emissiondiagnostic.Beside, frequency range of registration of acoustic emissionparameters usually estimates in tens, hundreds and thousands kilohertz and iswell protected from noises, which accompany work of technological equipmentunits.In many aspectsthe acoustic emission method reminds those of low-frequency acousticspectrometry, although in other aspects it is completely different.

Acousticemission methods are a clear shown wave process accompanied by variablespace-time localization of elastic energy.The increase ofmechanical processing efficiency is tied with search and realization of newspeeding-up methods of technological preparation for shape forming processes.Methods of rational carving conditions determination are being developed as oneof the most important tendencies in practical use of emissive technologicaldiagnostic means.An importantdirection in the practical use of progressive technology diagnostic methods forcarving process is the quality analysis of surface detail layer during theprocessing. The quality of a surface processed is formed as a result offriction, plastic deformation and the destruction of ingot material in carvingzone.

This is the reason why emissive process parameters must containinformation regarding surface s condition.It is possible to use acousticemission method to identify the moment of contact between a tool and an ingot.Thus, as shown bypreliminary analysis, the acoustic emission method has great technologicalpotential, which needs to be yet studied. The lack of knowledge regardingmethod s opportunities constrains its effective use in theory and practice ofmechanical carving of materials.