METHOD AND APPARATUS FOR NON-DESTRUCTIVE TESTING

• US 3,782,177 A
• Filed: 04/20/1972
• Issued: 01/01/1974
• Est. Priority Date: 04/20/1972
• Status: Expired due to Term

• Current Assignee: James M. Hoop
• Original Assignee: James M. Hoop
• Inventors: Hoop, James M.
• Primary Examiner(s): Queisser, Richard C.
• Assistant Examiner(s): Beauchamp, John P.
• Application Number:
  US05/246,056
• Time in Patent Office: 621 Days
• Field of Search: 73/67.5R,67.6,67.7,67.8R,67.8S,67.9,71.5U 340/12SD 179/113
• US Class Current: 73/643
• CPC Class Codes: G01N 2291/0289 Internal structure, e.g. defects, grain size, texture
• CPC Class Codes: G01N 2291/0423 Surface waves, e.g. Rayleigh waves, Love waves
• CPC Class Codes: G01N 29/2418 using optoacoustic interaction with the material, e.g. laser radiation, photoacoustics photoacoustic cells G01N21/1702; measuring characteristics of vibrations by using radiation-sensitive means G01H9/00; acousto-optical conversion techniques for short-range imaging G01S15/8965; sound-producing devices using laser bundle G10K15/046
• CPC Class Codes: G01N 29/343 pulse waves, e.g. particular sequence of pulses, bursts

Abstract

A high voltage is applied to an arc gap adjacent to a test specimen to develop a succession of high-frequency arc discharges. Those high frequency arc discharges generate pulses of ultrasonic energy within the test specimen without requiring the arc discharges to contact that test specimen and without requiring a coupling medium between those arc discharges and that test specimen. Those pulses can be used for detection of flaws, for measurement of certain properties of the test specimen, and for measurement of stresses within that test specimen.

Claims

1. A generator of energy which can be used in non-destructive testing of a test specimen and which comprises means defining a spark gap, and a source of high voltage energy which is connected to said means to develop a succession of spark discharges across said spark gap, said means being mounted relative to said test specimen so said succession of spark discharges applies a beam of energy to said test specimen which can interact with said test specimen to provide a detectable result, said means comprising a plurality of conductors which have conical tips and which are inclined relative to said test specimen to enable said tips to define an arc gap closely adjacent to said test specimen.

2. A generator of energy which can be used in non-destructive testing of a test specimen and which comprises means defining a spark gap, and a source of high voltage energy which is connected to said means tO develop a succession of spark discharges across said spark gap, said means being mounted relative to said test specimen so said succession of spark discharges applies a beam of energy to said test specimen which can interact with said test specimen to provide a detectable result, said means comprising a plurality of conductors of spark-resistant material and a support of transparent dielectric material for said conductors which holds said conductors at a predetermined distance from each other, wherein said support of transparent dielectric material has a chamber of hemispherical form therein, wherein said chamber has one side thereof open and directed toward said test specimen, wherein said conductors have sharp tips which extend into said hemispherical chamber and which are spaced apart a small fraction of an inch, wherein said source of high voltage energy develops said succession of spark discharges at a high frequency rate, whereby said beam of energy is a beam of ultrasonic energy, wherein said conductors are inclined relative to said test specimen to enable said tips to define an arc gap closely adjacent to said test specimen, wherein said source of high voltage energy supplies short pulses of energy in the nanosecond range, and wherein a passage for purging gas extends through said support of dielectric material to said chamber.