Method using ultrasound for detecting materials on metal surfaces

• US 6,286,370 B1
• Filed: 02/03/1999
• Issued: 09/11/2001
• Est. Priority Date: 02/03/1999
• Status: Expired due to Term

• Current Assignee: Sinha, Naveen Neil
• Original Assignee: Sinha, Naveen Neil
• Inventors: Sinha, Naveen Neil
• Primary Examiner(s): Williams, Hezron
• Assistant Examiner(s): MILLER, ROSE MARY
• Application Number:
  US09/244,245
• Time in Patent Office: 951 Days
• Field of Search: 735/79, 735/83, 736/02, 736/30, 736/45, 736/46, 736/48, 736/59, 736/49, 736/22, 736/25, 736/27, 736/28, 376/249
• US Class Current: 73/579
• CPC Class Codes: G01N 2291/023 Solids
• CPC Class Codes: G01N 2291/0231 Composite or layered materials
• CPC Class Codes: G01N 2291/0251 Solidification, icing, curing composites, polymerisation
• CPC Class Codes: G01N 2291/0421 Longitudinal waves
• CPC Class Codes: G01N 2291/0422 Shear waves, transverse waves, horizontally polarised waves
• CPC Class Codes: G01N 2291/102 one emitter, one receiver
• CPC Class Codes: G01N 2291/2694 Wings or other aircraft parts
• CPC Class Codes: G01N 29/032 by measuring attenuation of acoustic waves
• CPC Class Codes: G01N 29/11 by measuring attenuation of acoustic waves
• CPC Class Codes: G01N 29/348 with frequency characteristics, e.g. single frequency signals, chirp signals measuring frequency of mechanical vibrations or acoustic waves in general G01H1/06, G01H3/04; measuring frequency or analysing frequency spectra G01R23/00
• CPC Class Codes: G01N 5/02 by absorbing or adsorbing components of a material and determining change of weight of the adsorbent, e.g. determining moisture content absorption bulbs B01D53/00

Abstract

A method using ultrasound for detecting the presence of coatings on metal surfaces is described. The characteristics of resonant sound waves established within a metal plate are altered by the acoustic impedance of any coatings present on the surface of the metal in the vicinity of the waves. The amplitude and width of the resonant features are most directly affected and can readily be detected. For example, a reduction of approximately a factor of ten in resonance amplitude has been observed when ice is permitted to coat the surface of the plate. A resonant ultrasound condition is impressed on the plate using a transducer attached thereto on the side of the plate opposite to the coating. A receiving transducer is located next to the resonance inducing transducer. Thus, ice can be detected on the surface of an airplane wing surface using transducers located within the wing'"'"'s interior. Thin deposits of materials may be detected on the interior surface of a pipe using separated transducers located on the exterior thereof.

Claims

1. A method for detecting materials on metal surfaces, which comprises the steps of:

(a) applying sinusoidal vibrational excitation normal to the surface of the metal opposite the surface thereof to be investigated for deposits over a range of frequencies such that the wavelength of the sound waves induced in the metal is less than the thickness of the metal, and within which a standing-wave pattern is established;

(b) measuring the amplitude and/or the peak width of at least one feature in the standing-wave pattern in approximately the region wherein the sinusoidal vibrational excitation is applied to the metal surface; and

(c) comparing the measured amplitude and/or the measured peak width of the at least one feature in the standing-wave pattern with the amplitude and/or peak width of the corresponding feature in the standing-wave pattern of the uncoated metal, whereby the presence of materials on the metal surface is detected.

2. The method for detecting materials on metal surfaces as described in claim 1, wherein the range of operation of the transducers is between 1 and 4.5 MHz.

3. The method for detecting materials deposited on metal surfaces as described in claim 1, wherein the material is water or ice and the metal surface is an airplane wing.

4. A method for detecting the deposition of ice on the surface of an airplane wing, which comprises the steps of:

(a) applying sinusoidal vibrational excitation normal to the metal surface of the wing opposite the surface thereof to be investigated for ice deposit over a range of frequencies such that the wavelength of the sound waves induced in the metal wing surface is less than the thickness of the metal of the wing, and within which a standing-wave pattern is established;

(b) measuring the amplitude and/or the peak width of at least one feature in the standing-wave pattern in the region wherein the sinusoidal vibrational excitation is applied to the metal wing surface; and

(c) comparing the measured amplitude and/or the measured peak width of the at least one feature in the standing-wave pattern with the amplitude and/or the peak width of the corresponding feature in the standing-wave pattern of the uncoated metal wing surface, whereby the presence of ice on the metal wing surface is detected.

5. A method for determining the thickness of materials on the inside surface of a metal pipe, which comprises the steps of:

(a) applying sinusoidal vibrational excitation having a chosen frequency normal to the outside surface of the metal pipe using a first transducer, such that the wavelength of sound waves induced in the metal pipe is less than the thickness of the metal and within which a standing-wave pattern is established;

(b) measuring the amplitude of vibrational excitation in the vicinity of the first transducer using a second transducer located on the outside surface of the metal pipe as the first transducer; and

(c) comparing the measured amplitude with the corresponding amplitude of the uncoated metal pipe, whereby the presence of materials on the inside surface of the metal pipe is determined.