DEVELOPMENT OF INSTRUMENTS FOR NDT OF RAIL-TRACKS WITH USE OF CONTACTLESS ELECTROMAGNETIC ACOUSTIC EMISSION TRANSDUCERS(EMATs)

摘要

Currently for examination of railway metals used are ultrasonic and magnetic instruments. It necessary to underline that magnetic testing method provides detection of defects located in subsurface area of railhead (up to 8mm) only, while ultrasonic testing (UT) have wider scope of applications, but to realize those better opportunities it is required to use liquid couplants. The most promising method in this area of application appears to be electromagnetic-acoustic method when use is made of ElectroMagnetic Acoustic transducers (EMAT).The practical results of EMATs' preliminary trials showed that this type of transducers become equal to those widely used for contactless UT of various items. At the ScientificProduction Enterprise "VIGOR" developed are methods and design of EMATs to excite andregister ultrasonic waves of various types implemented in the processes of rail-tracks examination. The EMATs provide reliable radiation and registration of acoustic signals at angles of 0, 40 and 60 as well as Relay waves. The noise-to-signal ratio for developed transducers is approximately the same as for piezoelectric ones and this make it possible to provide examination sensitivity (in case when EMATs are used) practically the same as achieved for modern contact methods.The EMA NDT testing method is new and efficient in the field of rail-tracks flaw detection,but at the same time it have wide range of applications, i.e. in the process of: -) output railtracks'quality control conducted by the manufacturers; -) output / input used rail-tracks'quality control conducted by the rails-welding facilities; -) examination of continuously welded rails after welding works and in the process of rail-tracks' diagnostics carried out with the help of fast, mobile testing devices. Beside mentioned above, the EMA method can be used in other branches of industry, for example, in oil and gas industry; air, sea and automobile transportation; at heavy duty production, etc.