Inversion of data from Laser Ultrasonic Characterization of Hot-Rolled Steel Strip

volker, arno; TNO; Netherlands

Duijster, A.; TNO; Netherlands
Volker, A.; TNO; Netherlands
Duijster, A.; TNO; Netherlands
Krix, D.; Salzgitter Mannesmann Forschung GmbH; Germany
Schmidt, R.; Arcelor-Mittal Eisenhüttenstadt; Germany
van den Berg, F.D.; Tata Steel; Netherlands

ID: ECNDT-0302-2018
Download: PDF
Session: Acoustic Emission 2 / Laser UT 1
Room: J1
Date: 2018-06-14
Time: 09:40 - 10:00

Grain size and texture are important properties of sheet metal because they greatly influence the mechanical properties. Laser ultrasonic measurements offer the potential to monitor the product uniformity inline. The grain size is known to affect ultrasonic attenuation by scattering on grain boundaries, and texture influences the velocity of the propagated waves in different directions. Measuring the attenuation inline poses some challenges because of the thin sheet thickness and relatively small grains. A new approach is proposed by measuring the full ultrasonic wave field along a line at the surface of the sample using non-contact laser-based generation and detection methods. Analysis of multiple wavefronts in the data leads to information about the texture of a sample. The data is also analysed by double Fourier transform in the wavenumber-frequency domain, where specific parts of the observed dispersion curves can be associated with pure compressional and shear waves. The energy distribution as function of mode number is used to characterize different samples in the rolling and transverse direction. The method is applied to various steel grades from different manufacturers, and influences of grain size and/or texture variations are shown.