MoscowState Technical University named after Bauman
EssayAcoustic Emission
Post-graduate Golenkov N.S.
English Teacher Kislova V.M.
Moscow
2001
Theappearance of new technologies as well as the perfection of traditional ones ismostly based on the results of research in the fields of solid physics, quantummechanics, 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.
Intensificationof science 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.
Amongstdiagnostic methods the most widely spread in field of machinery construction isan acoustic 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.
Itis necessary to mention that an acoustic emission method is one of the newestand most prospective diagnostic methods. It is physical nature causes expandingfields of application for the method in technology.
Firstworks by acoustic emission method appeared in 70s. This works fulfilled in thelate 70s and early 80s are characterized by fairly narrow range oftechnological tasks, connected mostly with tool wear control.
Sourcesof an acoustic 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 dynamic redistribution of tension fields in material apply tointernal sources of acoustic emission. For example, acts of plasticdeformation, micro- and macro destruction and phase transformation. Analyzingthe cut zone from these positions can make a conclusion about existence in thiszone whole number of acoustic emission sources of different power and spectraldensity. Acoustic emission parameters depend on a way plastic deformation,destruction and friction processes go. It is possible to carry out acousticemission diagnostic. Beside, frequency range of registration of acousticemission parameters usually estimates in tens, hundreds and thousands kilohertzand is well protected from noises, which accompany work of technologicalequipment units.
Inmany aspects the 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.
Theincrease of mechanical processing efficiency is tied with search andrealization of new speeding-up methods of technological preparation for shapeforming processes. Methods of rational carving conditions determination arebeing developed as one of the most important tendencies in practical use ofemissive technological diagnostic means.
Animportant direction in the practical use of progressive technology diagnosticmethods for carving process is the quality analysis of surface detail layerduring the processing. The quality of a surface processed is formed as a resultof friction, plastic deformation and the destruction of ingot material incarving zone. 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 by preliminary analysis, the acoustic emission method has greattechnological potential, which needs to be yet studied. The lack of knowledgeregarding method’s opportunities constrains its effective use in theory andpractice of mechanical carving of materials.