Transducer for measuring acoustic emission events

• US 6,041,656 A
• Filed: 10/23/1997
• Issued: 03/28/2000
• Est. Priority Date: 10/31/1995
• Status: Expired due to Term

• Current Assignee: Score Atlanta, Inc.
• Original Assignee: Dunegan Engineering Consultants, Inc.
• Inventors: Dunegan, Harold L.
• Primary Examiner(s): Williams, Hezron
• Assistant Examiner(s): MILLER, ROSE MARY
• Application Number:
  US08/956,804
• Time in Patent Office: 887 Days
• Field of Search: 73/587, 73/110 V, 73/649, 73/652, 73/654, 73/763, 73/774, 73/778, 73/514.01, 73/514.16, 73/514.29, 73/514.34, 73/526, 73/602, 310/328, 310/329, 310/336, 310/369
• US Class Current: 73/587
• CPC Class Codes: G01H 1/00 Measuring characteristics of vibrations in solids by using direct conduction to the detector G01H9/00, G01H11/00 take precedence
• CPC Class Codes: G01H 1/12 of longitudinal or not specified vibrations
• CPC Class Codes: G01N 2291/014 Resonance or resonant frequency
• CPC Class Codes: G01N 2291/02854 Length, thickness
• CPC Class Codes: G01N 2291/0289 Internal structure, e.g. defects, grain size, texture
• CPC Class Codes: G01N 2291/0422 Shear waves, transverse waves, horizontally polarised waves
• CPC Class Codes: G01N 2291/0423 Surface waves, e.g. Rayleigh waves, Love waves
• CPC Class Codes: G01N 2291/0427 Flexural waves, plate waves, e.g. Lamb waves, tuning fork, cantilever
• CPC Class Codes: G01N 2291/0428 Mode conversion
• CPC Class Codes: G01N 2291/2632 flat
• CPC Class Codes: G01N 29/14 using acoustic emission techniques echo of particles G01N29/046; measuring mechanical vibrations or acoustic waves in solids in general G01H1/00
• CPC Class Codes: G01N 29/2437 Piezoelectric probes
• 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 29/36 Detecting the response signal , e.g. electronic circuits specially adapted therefor
• CPC Class Codes: G01N 29/40 by amplitude filtering, e.g. by applying a threshold or by gain control
• CPC Class Codes: G01N 29/42 by frequency filtering or by tuning to resonant frequency
• CPC Class Codes: G10K 11/004 Mounting transducers, e.g. provided with mechanical moving or orienting device mountings specially adapted to a particular sound-producing device, see the preceding groups G10K1/00 - G10K9/00, e.g. G10K1/26, G10K1/28, G10K9/22; arrangements of sonic watch equipment on submarines B63G8/39; buoys B63B22/00

Abstract

An apparatus for detecting and measuring cracks in plate-like Structures using acoustic emission technique is disclosed. A transducer coupled with the structure is equally sensitive to in-plane and out-of-plane acoustic emission signals. A splitter receives the output signal of the transducer and divides the acoustic emission signal into a high-frequency signal and a low-frequency signal. A circuit generates a high-frequency peak amplitude and a low-frequency amplitude from there high-frequency and low-frequency signals. A computer computes the ratio of the high-frequency peak amplitude to the low-frequency peak amplitude.

Claims

1. An apparatus for detecting acoustic emission signals from a crack in a structure, comprising:

a transducer coupled with said structure and configured to sense acoustic emission signal in said structure, said transducer being equally sensitive to in-plane and out-of-plane acoustic emission signals;

a splitter which receives said signal from said transducer and divides said signal into a high-frequency signal and a low-frequency signal; and

a circuit which generates a high-frequency peak amplitude and a low-frequency peak amplitude from said high-frequency and low-frequency signals.

2. The apparatus of claim 1, wherein said circuit comprises

an amplifier which amplifies said high-frequency signal and said low-frequency signal;

a high-pass filter which filters said high-frequency signal;

a bandpass filter which filters said low-frequency signal;

a high-frequency peak detector circuit which generates said high-frequency peak amplitude; and

a low-frequency peak detector circuit which generates said low-frequency peak amplitude.

3. An apparatus for detecting acoustic emission signals from a crack in a structure, comprising:

a transducer coupled with said structure and configured to sense acoustic emission signal in said structure, said transducer being equally sensitive to in-plane and out-of-plane acoustic emission signals;

a splitter which receives said signal from said transducer and divides said signal into a high-frequency signal and a low-frequency signal; and

a circuit which generates a high-frequency peak amplitude and a low-frequency peak amplitude from said high-frequency and low-frequency signals, and

wherein said transducer includes a piezoelectric crystal having a hole housed in a metal case and a ball bearing bonded to said crystal adjacent said hole.

4. The apparatus of claim 3, wherein said crystal is circular cylindrical of 0.5 inch in diameter, 0.15 inch in thickness, and polarized in the thickness expander mode, said hole is 0.1 inch in diameter, and said ball bearing is 0.1 inch in diameter and 0.125 inch flat.

5. An apparatus for detecting acoustic emission signals from a crack in a structure, comprising:

a sensing means for receiving acoustic emission signal from said structure;

a means of splitting said signal into a high-frequency signal and a low-frequency signal; and

a means of producing a high-frequency peak amplitude from said high-frequency signal and a low-frequency peak amplitude from said low-frequency signal.

6. An apparatus for detecting acoustic emission signals from a crack in a structure, comprising:

a transducer coupled with said structure and configured to sense acoustic emission signal in said structure, said transducer being equally sensitive to in-plane and out-of-plane acoustic emission signals;

a splitter which receives said signal from said transducer and divides said signal into a high-frequency signal and a low-frequency signal;

a circuit which generates a high-frequency peak amplitude and a low-frequency peak amplitude from said high-frequency and low-frequency signals; and

a computer which receives said high-frequency peak amplitude and said low-frequency peak amplitude and computes the ratio of said high-frequency peak amplitude to said low-frequency peak amplitude.

7. An apparatus for detecting acoustic emission signals from a crack in a structure, comprising:

a sensing means for receiving acoustic emission signal from said structure;

a means of splitting said signal into a high-frequency signal and a low-frequency signal;

a means of producing a high-frequency peak amplitude from said high-frequency signal and a low-frequency peak amplitude from said low-frequency signal; and

a means for computing the ratio of said high-frequency peak amplitude to said low-frequency peak amplitude.