| 摘要 |
A method of examining a ductile iron casting to determine a percent of nodularity present in the casting uses an electromagnetic acoustic transducer (EMAT) system to determine a time-of-flight of an ultrasonic shear wave pulse transmitted through the casting at a selected location, from which a velocity of sound in the casting can be determined. The ultrasonic shear wave pulse created and sent through the casting experiences several internal reflections within the casting, and the absolute delay time for both second, TDELAY1, and third, TDELAY2, multiple reflections are used to determine the time, TDELTA, required for the ultrasonic pulse to travel through twice the thickness, t, of the casting at said location. The velocity, VSHEAR, of the ultrasonic shear wave pulse through the casting is calculated from TDELTA and a measurement of the thickness, t, of the casting at the location being inspected. The percent of nodularity of the casting is determined from a pre-established relationship between the calculated shear wave velocity, VSHEAR, and the percent of nodularity for ductile cast iron.
|
