Zero-group-velocity modes in textured steel plates: experiments and elastic modeling
Zero-group-velocity (ZGV) resonances are investigated as a non-contact ultrasonic probe of elastic anisotropy in textured steel plates. Directional laser-ultrasonic measurements were performed on 70% cold-rolled Ti-stabilized interstitial-free steel plates in the full-hard and recrystallized condition. Experimental results were compared with predictions based on effective elastic stiffness tensors derived from X-ray diffraction measurements. Classical Voigt-Reuss-Hill estimates and microstructure-resolved finite-element homogenization reproduce the measured angular dependence of the ZGV frequencies well for both states, with the finite-element KUBC/SUBC bounds considerably narrower than the classical Voigt-Reuss bounds. For the full-hard state, agreement with the texture-based model is obtained only after a recovery treatment. This indicates that dislocations present in the full-hard material contribute to its elastic response, an interpretation that is further supported by theoretical estimations. An identifiability analysis shows that the directional ZGV measurements provide access to at least three independently observable combinations of the stiffness tensor components, and concluding suggestions for application in recrystallization monitoring are provided.