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국일현,박춘득,구자호 한국방사선산업학회 2015 방사선산업학회지 Vol.9 No.2
The iridium disc, generally used in industrial radiography, is examined to find thefracture morphology and fine particles remaining on the shear blank surface. Randomly selected1,200 discs were observed under a scanning electron microscope tilted more than 45°. Fracturesurfaces are classified into three groups: (1) surface fall-out, (2) fracture on the edge and (3)multi-step brittle fracture, which shows the mutual relationship between the fracture morphologyand remaining particles. Fracture particles were removed by cleaning the discs in a ultrasonicbath with acetone and collected at the bottom. Removed number of the particles were countedfor each different group of fracture surfaces. Followings are conclusions: (1) About 80.5% ofdiscs (966/1,200), have sound plastic shear surfaces with particles remained. (2) About 2% discsaccompany surface fall-out’s having large particles tens of μm, which is stable not to be pulledout even after the considerably long time of ultrasonic cleaning. (3) About 5% discs contain thefractures on the edge and the particles are removed thoroughly within 30 minutes. (4) 234 discsout of 1,200 discs have multi-step fracture surfaces whose particles never removed in a shortperiod of time but come out very slowly. Such a disc having multiple-step fracture is attributedto the promate cause to the ‘leaker’. It is noted here that the discs having mutiple-step fracturesshould be treated separately with special care, and it is need to study how to treat them.