Method and apparatus for acoustic emission monitoring

• US 4,910,718 A
• Filed: 10/05/1988
• Issued: 03/20/1990
• Est. Priority Date: 10/05/1988
• Status: Expired due to Term

• Current Assignee: Vought Aircraft Industries, Inc. (Triumph Group, Inc.)
• Original Assignee: Grumman Aerospace Corporation (Northrop Grumman Corporation)
• Inventors: Horn, Michael
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): Pihulic, Daniel T.
• Application Number:
  US07/253,644
• Time in Patent Office: 531 Days
• Field of Search: 367/124, 367/127, 367/129, 367/118, 367/907, 73/572, 73/583
• US Class Current: 367/124
• CPC Class Codes: G01N 2291/106 one or more transducer arrays
• CPC Class Codes: G01N 2291/2694 Wings or other aircraft 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: G01S 3/8083 determining direction of source
• CPC Class Codes: G01S 5/20 Position of source determined by a plurality of spaced direction-finders
• CPC Class Codes: G01V 1/001 Acoustic presence detection
• CPC Class Codes: Y10S 367/907 Coordinate determination

Abstract

In order to locate a source of acoustic emissions, two multi-element transducers are employed. The elements of each transducer are subjected to an impinging acoustic wave at different moment in time depending upon the angle of the wave. Outputs from the elements of each transducer are compared with a look-up table to determine the angle. Then, another look-up table is used to determine the X-Y intersection of impinging wave angles from both transducers which locates the source.

Claims

1. A system for monitoring acoustic emissions from a source, the system comprising:

a first single transducer array which includes at least three transducer elements mounted adjacent one another in a single package and having acoustically exposed surfaces in the same plane;

first threshold detecting means for sensing when each respective element receives an impinging acoustic wave from the source;

first means connected at its input to the threshold detecting means for measuring the time of arrival of the sensed acoustic wave at each element;

first means connected at its input to the measuring means for storing data representing the sequence and time periods during which the individual elements are affected by the wave;

first memory means for storing a first look-up table, the first memory means comparing the stored data with the contents of the first look-up table for determining a corresponding angular direction of the wave relative to the first transducer array;

a second single transducer array which includes at least three transducer elements mounted adjacent one another in a single package and having acoustically exposed surfaces in the same plane;

second threshold detecting means for sensing when each respective second transducer element receives an impinging acoustic wave from the source;

second means connected at its input to the second threshold detecting means for measuring the time of arrival of the sensed acoustic wave at each element of the second transducer array;

second means connected at its input to the second measuring means for storing data representing the sequence and time periods during which the individual elements are affected by the wave; and

second memory means for storing a second look-up table, the second memory means comparing the stored data of the second storing means with the contents of the second look-up table for determining the angular direction of the wave relative to the second transducer array;

third memory means for storing a third look-up table for comparing the first and second directions obtained from the first and second memory means with the contents of the third look-up table, the third memory means determining the X-Y intersection of the first and second waves incident to the transducer arrays thereby establishing the location of the source.

2. A method for monitoring acoustic emissions from a source, the method comprising the steps:

positioning a first single multi-element transducer array within a zone to be monitored, multi-elements mounted adjacent one another in a single package and having acoustically exposed surfaces in the same plane;

sensing when each respective element receives an impinging acoustic wave from the source;

measuring the time of arrival of the sensed acoustic wave at each element;

storing data representing the sequence and time periods during which the individual elements are affected by the wave;

storing a first look-up table for comparing the stored data with the contents of the first look-up table for determining the angular direction of the wave relative to the first transducer array;

positioning a second single multi-element transducer array within a zone to be monitored, multi-elements mounted adjacent one another in a single package and having acoustically exposed surfaces in the same plane;

sensing when each respective element of the second transducer array receives an impinging acoustic wave from the source;

measuring the time of arrival of the sensed acoustic wave at each element of the second transducer array;

storing data representing the sequence and time periods during which the individual elements of the second transducer array are affected by the wave;

storing a second look-up table for comparing the stored data with the contents of the second look-up table for determining the angular direction of the wave relative to the second transducer array;

storing third look-up table for comparing the first and second angular directions obtained from the waves relative to the first and second transducer arrays with the contents of the third look-up table for determining the X-Y intersection of the first and second incident to the transducer arrays thereby establishing the location of the source.

3. The method set forth in claim 2 together with the step of comparing the derived X-Y intersection with a preselected boundary;

and

rejecting any derived X-Y intersection outside the boundary.