Remote self-powered structure monitor

• US 6,076,405 A
• Filed: 07/24/1996
• Issued: 06/20/2000
• Est. Priority Date: 08/31/1994
• Status: Expired due to Fees

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Schoess, Jeffrey N.
• Primary Examiner(s): MOLLER, RICHARD ALAN
• Application Number:
  US08/690,263
• Time in Patent Office: 1,427 Days
• Field of Search: 73/587, 73/583, 73/801, 73/802, 340/665, 340/870.16, 364/508, 310/328
• US Class Current: 73/587
• CPC Class Codes: G01H 1/003 of rotating machines G01H1/10 takes precedence
• CPC Class Codes: G01H 11/08 using piezoelectric devices
• CPC Class Codes: G01M 5/0033 by determining damage, crack or wear
• CPC Class Codes: G01M 5/0066 by exciting or detecting vibration or acceleration vibration testing of structures G01M7/00
• CPC Class Codes: G01N 2291/014 Resonance or resonant frequency
• CPC Class Codes: G01N 2291/0289 Internal structure, e.g. defects, grain size, texture
• CPC Class Codes: G01N 2291/101 one transducer
• CPC Class Codes: G01N 2291/2693 Rotor or turbine parts
• 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 29/42 by frequency filtering or by tuning to resonant frequency
• CPC Class Codes: G01N 29/46 by spectral analysis, e.g. Fourier analysis or wavelet analysis spectral signal processing per se G06F17/14

Abstract

An acoustic rotor monitor that is an autonomous self-powered measurement instrument which can detect embedded and hidden fatigue cracks in remotely inaccessible devices such as helicopter rotor system components. A predictive maintenance-related problem for rotor craft is the detection of fatigue cracks as a continuous real-time monitoring process under dynamic rotor system loading conditions. The rotor monitor focuses on the embedding an acoustic emission-based smart sensor directly into the rotor system to measure the high frequency stress waves indicating that a structural crack has propagated as a "self-powered" measurement without reducing structural integrity.

Claims

1. A remote structure monitor, for detecting structural crack beginnings and growth in a rotating metal structure, comprising:

a piezo-electric acoustic emission sensor on the rotating metal structure for detecting non repetitive high frequency acoustic emission events of 1 to 10 MHz from stress wave acoustic emission energy that comes from said structural crack beginnings and growth and for converting the acoustic emission energy into electrical signals;

a signal processor, connected to said piezo acoustic emission sensor for receiving the electrical signals prom said emission sensor, said piezo-electric acoustic emission sensor being formed from a plurality of piezo-electric layers and a plurality of elastomeric layers situated between the plurality of piezo-electric layers, such that the piezo-electric and elastomeric layers are stacked on one another alternately in that one elastomeric layer is situated between adjacent piezo-electric layers to form a layered sensor;

a power storage device being positioned on said layered sensor to provide an inertial load, wherein said sensor outputs the electrical power signals due to compression, stretching and/or bending of the plurality of piezo-electric layers, caused by the vibration of said rotating metal structure and enhanced by said inertial load.

2. The structure monitor in claim 1, wherein said piezo-electric transducer is flexible and conformable to the structure being monitored.

3. The remote structure monitor in claim 1, wherein the monitor is used to detect structural defects or cracks in rotating metal structures in aircraft airframe structures.

4. The remote structure monitor in claim 3, wherein the monitor is used to detect structural defects or cracks in the rotating structures of rotating wing aircraft.

5. The monitor of claim 1, wherein said sensor comprising an acoustic emission energy PVDF piezoelectric transducer mounted on a metal rotating structure to be monitored for detecting said structural crack beginnings and growth in a structure using non repetitive high frequency acoustic emission of 1 to 10 MHz, stress wave acoustic emission energy.

6. The monitor of claim 5, wherein said signal processor comprising a radio frequency telemetry circuit connected to said transducer and said power storage device to transmit data from said signal conditioner identifying crack propagation and transmit power to said power storage device.