Flaw detection system using acoustic doppler effect

• US 6,854,333 B2
• Filed: 01/26/2001
• Issued: 02/15/2005
• Est. Priority Date: 02/24/1998
• Status: Expired due to Fees

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Wooh, Shi-Chang
• Primary Examiner(s): Williams, Hezron
• Assistant Examiner(s): SAINT SURIN, JACQUES M
• Application Number:
  US09/770,319
• Publication Number:
  US 20010020390A1
• Time in Patent Office: 1,481 Days
• Field of Search: 736/43, 736/44, 735/96, 736/57, 735/97, 735/98, 735/99, 736/00, 736/02, 738/66, 356/445, 356/450
• US Class Current: 73/643
• CPC Class Codes: B61K 9/10 for detecting cracks in rails or welds thereof
• CPC Class Codes: G01N 2291/017 Doppler techniques
• CPC Class Codes: G01N 2291/101 one transducer
• CPC Class Codes: G01N 2291/102 one emitter, one receiver
• CPC Class Codes: G01N 2291/2623 Rails; Railroads
• CPC Class Codes: G01N 29/2412 using the magnetostrictive properties of the material to be examined, e.g. electromagnetic acoustic transducers [EMAT]; investigating the presence of flaws using eddy currents G01N27/90, magnetostrictive transducers B06B1/08, measuring magnetostrictive properties G01R33/18
• 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 29/265 by moving the sensor relative to a stationary material
• 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

Abstract

A flaw detection system using acoustic Doppler effect for detecting flaws in a medium wherein there is relative motion between the medium and system includes a transducer, spaced from the medium to be inspected, for introducing to and sensing from the medium an acoustic signal that propagates in the medium at a predetermined frequency; and a detector, responsive to the sensed propagating acoustic signal, for detecting in the sensed acoustic signal the Doppler shifted frequency representative of a flaw in the medium.

Claims

1. A flaw detection system using acoustic Doppler effect for detecting flaws in a medium wherein there is relative motion between the medium and system comprising:

air-coupled transducer means, spaced from the medium to be inspected, which transmit optical energy for introducing to and receiving from the medium an acoustic signal that propagates in said medium at a predetermined frequency; and

means, responsive to the received propagating acoustic signal, for detecting in the received acoustic signal the Doppler shifted frequency representative of a flaw in the medium.

2. The flaw detection system using acoustic Doppler effect of claim 1 in which said transducer means includes a laser for transmitting said optical energy.

3. A flaw detection system using acoustic Doppler effect for detecting flaws in a medium wherein there is relative motion between the medium and system comprising:

air-coupled transducer means, spaced from the medium to be inspected, for introducing to and sensing from the medium an acoustic signal that propagates in said medium at a predetermined frequency said transducer means including an acoustic receiver for sensing the acoustic signal propagating in the medium and a transmitter that transmits optical energy.

4. A flaw detection system using acoustic Doppler effect for detecting flaws in a medium wherein there is relative motion between the medium and system comprising:

air-coupled transducer means, spaced from the medium to be inspected, for inducing an acoustic signal to propagate in the medium at a predetermined frequency and receiving the propagating acoustic signal in the medium; and

said transducer means including a transmitter and a receiver and said transmitter including a laser for locally heating the medium to generate acoustic signals; and

means, responsive to the received propagating acoustic signal, for distinguishing the Doppler shifted frequency representative of a flaw in the medium.

5. A flaw detection system using acoustic Doppler effect for detecting flaws in a medium wherein there is relative motion between the medium and system comprising:

an air-coupled transducer, spaced from the medium to be inspected, that transmits optical energy for introducing to and receiving from the medium an acoustic signal that propagates in said medium at a predetermined frequency; and

a detector, responsive to the received propagating acoustic signal, that detects in the received acoustic signal the Doppler shifted frequency representative of a flaw in the medium.

6. The flaw detection system using acoustic Doppler effect of claim 5 in which said transducer includes a laser that transmits said optical energy.

7. A flaw detection system using acoustic Doppler effect for detecting flaws in a medium wherein there is relative motion between the medium and system, comprising:

an air-coupled transducer, spaced from the medium to be inspected, that introduces to and senses from the medium an acoustic signal that propagates in said medium at a predetermined frequency, said transducer including an acoustic receiver that senses the acoustic signal propagating in the medium and a transmitter that transmits optical energy.

8. A flaw detection system using acoustic Doppler effect for detecting flaws in a medium wherein there is relative motion between the medium and system, comprising:

an air-coupled transducer, spaced from the medium to be inspected, that induces an acoustic signal to propagate in the medium at a predetermined frequency and receives the propagating acoustic signal in the medium, said transducer including a transmitter and a receiver, said transmitter including a laser that locally beats the medium to generate acoustic signals; and

means, responsive to the received propagating acoustic signal, for distinguishing the Doppler shifted frequency representative of a flaw in the medium.