Contactless Mode-Selective Resonance Ultrasound Spectroscopy: Electromagnetic Acoustic Resonance
Abstract
We describe a novel method for measuring elastic constants and internal friction in electrically conductive solids: electromagnetic acoustic resonance (EMAR). Contactless coupling based on the Lorentz-force mechanism is achieved by permanent magnets to supply the static magnetic field and a solenoidal coil surrounding a rectangular-parallelepiped specimen. Because the direction and symmetry of the Lorentz forces can be easily changed by changing the geometrical configuration of the static field and the coil, we can select a single vibration group of interest, filtering out the other vibration groups. In principle, seven vibration groups can be independently excited among eight possible vibration groups of a rectangular-parallelepiped specimen. This provides a big advantage in mode identification. The EMAR method is much less sensitive than the RUS method to the initial (guessed) Cij for the inverse calculation. For a copper monocrystal, we reached the same Cij with 100%-varied guessed values. For silicon-carbide-fiber-reinforced titanium-alloy composites, we could vary the guessed values up to 20%. We used a free-decay method to measure internal friction Qij(exp -1). The contactless EMAR method enables one to measure intrinsic internal friction, free from energy loss into transducers and grips.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 04, 2001
- Accession Number
- ADP011285
Entities
People
- Hassel Ledbetter
- Hirotsugu Ogi
Organizations
- Osaka University