Acoustic emissions simulator

• US 4,018,084 A
• Filed: 05/13/1976
• Issued: 04/19/1977
• Est. Priority Date: 05/13/1976
• Status: Expired due to Term

• Current Assignee: Lockheed Aircraft Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Aircraft Corporation (Martin Marietta Corporation)
• Inventors: Hsu, Nelson N.
• Primary Examiner(s): Gill, James J.
• Assistant Examiner(s): Ciarlante, Anthony V.
• Application Number:
  US05/686,071
• Time in Patent Office: 341 Days
• Field of Search: 73/71.5 R, 73/552, 73/69, 73/1 DV
• US Class Current: 73/801
• 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 29/30 Arrangements for calibrating or comparing, e.g. with standard objects

Abstract

This device generates a simulated acoustic emission signal and simultaneously introduces the signal into a test article. The device provides a means for positioning precision brittle tubes or rods against the test article in a controlled fashion. A simulated signal, a stress pulse, is introduced into the test article at a point source when sufficient force is applied to break the tubes or rod against the test article. The stress pulse is generated by the rapid release of elastic energy within the test article itself therefore it very closely simulates the acoustic emission signal generated by a flaw in the material.

Claims

1. An instrument adapted to generate a stress pulse on a localized area of a metal specimen simulating the acoustic emission which emanates from an actual crack in said specimen comprising:

an outer cylindrical tube tapered at its forward end;

a core mounted for limited sliding movement in said tube;

a gripping element carried by said core at its forward end adjacent said tapered tube end and adapted to secure a frangible element when said core moves toward said tapered tube end and to release said frangible element when said core moves toward the aft end of said tube, whereby said frangible element is moved a predetermined distance toward and extended a predetermined distance beyond said tapered tube end; and

an angularly adjustable support carried by said tube for abutment against said specimen to dispose said frangible element when extended as aforesaid at a preselected angle relative to the surface of said specimen whereby a force applied thereon moves the frangible element against said specimen until it breaks.

2. The instrument of claim 1 wherein said tapered tube end includes a thickened wall on the side thereof remote from said specimen when said support abuts the specimen as aforesaid.

3. The instrument of claim 1 including a shield carried by said tapered tube end overlying the frangible element when extended as aforesaid.

4. The instrument of claim 1 wherein said core terminates beyond the aft end of said tube and includes a compression spring disposed between said core and said tapered tube end and operative to control the limited sliding movement of the tube as aforesaid.

5. The instrument of claim 1 wherein said core includes a center tube terminating at its aft end in a relatively large inner and outer diameter portion constituting a container for the storage of multiple said frangible elements and terminating at its forward end in a relatively small inner and outer diameter portion forming a passage sized to accommodate only one said frangible element at a time, the internal surfaces of said diameter portions merging in a smooth, uninterrupted transition surface whereby a single said frangible element moves from said container into said small diameter portion when said instrument is disposed in an upright position.

6. The instrument of claim 1 wherein said support includes a sleeve slidably mounted on said outer tube and an anvil pivotally secured to said sleeve, said anvil having an outer surface adapted to contact said specimen.

7. The instrument of claim 6 wherein said outer tube includes calibrations inscribed thereon adapted for coaction with said sleeve to indicate the angle of inclination of said outer tube to said specimen.