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Techniques of Acoustic Resonance Spectroscopy

IP.com Disclosure Number: IPCOM000062749D
Original Publication Date: 1986-Nov-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 1 page(s) / 13K

Publishing Venue

IBM

Related People

Crawforth, L: AUTHOR [+3]

Abstract

The technique of acoustic resonance spectroscopy (ARS) as excited by scanning the frequency of modulation of a magnetic field acting on a sample is not limited to ferromagnetic samples nor to magnetic excitations. This immediately opens up many other fields of applications of ARS for automated manufacturing applications (e.g. material control or process monitoring) invol products containing metal, semiconductor, or ceramic parts. We show here the signals that can be observed in examples of each of these materials, and excited by purely magnetic modulations or by other means. The electronic detection scheme has previously been described as electrically-conductive ceramic material for the case of application of ARS to investigate ferromagnetic samples.

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Techniques of Acoustic Resonance Spectroscopy

The technique of acoustic resonance spectroscopy (ARS) as excited by scanning the frequency of modulation of a magnetic field acting on a sample is not limited to ferromagnetic samples nor to magnetic excitations. This immediately opens up many other fields of applications of ARS for automated manufacturing applications (e.g. material control or process monitoring) invol products containing metal, semiconductor, or ceramic parts. We show here the signals that can be observed in examples of each of these materials, and excited by purely magnetic modulations or by other means. The electronic detection scheme has previously been described as electrically-conductive ceramic material for the case of application of ARS to investigate ferromagnetic samples.

A further example of ferromagnetic samples is the ARS signals for printhead cups used for making printers. In fact, the cups look superficially the same, but it is known that they perform very differently. Using the excitation scheme, we have shown that ARS has very adequate sensitivity to distinguish high porosity cups from low porosity cups.

NON-FERROMAGNETIC METAL PART - To show that ARS is not limited to ferromagnetic products, we experimented with a brass piece. For excitation, we now rely on the interaction of an ac eddy current in the sample (induced by an ac coil placed near it) with a dc applied magnetic field. Thus, an acoustic excitation due to the ac Lorentz force at the same frequency as the ac in the coil is produced. By scanning the frequency of the ac in the coil, we can perform ARS due to Lorentz excitation. The Lorentz excitation becomes zero when there is no magnetic...