24 - Determination of Ductile Iron Nodularity Using Critically-Refracted Longitudinal Ultrasonic Wav

Abstract:

Determination of Ductile Iron Nodularity Using Critically-Refracted Longitudinal Ultrasonic Waves

Ultrasonic velocity measurements on castings, especially automotive safety parts, are used routinely to ensure conformance of castings to minimum nodularity requirements. Separately cast test specimens are sometimes monitored to detect departures (in the form of nodularity, carbide, or other quality-related concerns) from normal melting and treating processes. Conventional ultrasonic techniques require two parallel (or nearly so) surfaces for probe placement, a situation not always possible or convenient. The critically refracted longitudinal (Led wave technique requires only one free surface on the specimen for probe placement, as it does not transmit through the cross section but, rather, along its surface. It may be used on castings or separately cast test specimens.