Study of Cold Worked Austenitic Stainless Steel - Using LCR Waves

摘要

Ultrasonic nondestructive testing and evaluation plays a major role in the presentrnday condition monitoring and life assessment of components and structures inrnvarious industries, during pre-service and in-service inspections. While bulk wavesrnare useful for characterising the volumetric properties, surface waves are used forrnevaluating the surface and sub-surface properties of the materials. In the recentrnpast, Bray and Junghans[1] have successfully demonstrated the potentialrnapplications of critically refracted longitudinal (L_(CR)) ultrasonic waves. L_(CR) wavesrntravel just below the surface of the material and have the properties of bothrnsurface and bulk waves. L_(CR) waves are found to have several advantages overrnconventional Rayleigh surface waves and bulk waves for specific applications. Inrnthe present work, perspex wedges have been designed to generate and detect L_(CR)rnwaves with probes of frequency 2 MHz. One wedge-probe assembly for generating andrnanother for detecting L_(CR) waves have been used in this study. The transmitterreceiverrnprobe assembly thus fabricated has been used for studying austeniticrnstainless steel (AISI type 304) specimens cold worked in the range 0 to 50%.rnPrecise transit time measurements and velocity calculations of L_(CR) waves were madernin different specimens. The results were compared with the results of earlierrnmeasurements made with bulk waves. It is observed that L_(CR) wave velocityrnmeasurements have practical advantage for assessment of the percentage cold workingrnin austenitic stainless steel.