Determination of Sheet Steel Formability Using Wide Band Electromagnetic-Acoustic Transducers

An electromagnetic-acoustic transducer (EMAT) system was used in conjunction with a "sampled" CW signal-processing method to generate, receive, and process longitudinal and shear waves in thin steel sheets. Using the system, swept-frequency measurements were made up to 7.5 MHz. To relate the measurements to sheet steel formability, a dimensionless frequency ratio, K, was computed from the resonant frequencies. From theoretical considerations, K should be related to a measure of steel sheet formability, r . This parameter is traditionally measured by plastically deforming uniaxial tension specimens. Good correlation was found between K and r for a set of steel sheet representative of those typically used to produce automobile body parts.