Flaw detection system using acoustic doppler effect

• US 6,715,354 B2
• Filed: 02/24/1998
• Issued: 04/06/2004
• 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): MOLLER, RICHARD ALAN
• Application Number:
  US09/028,536
• Publication Number:
  US 20010015104A1
• Time in Patent Office: 2,233 Days
• Field of Search: 735/96, 735/97, 735/98, 736/18, 736/32, 736/33, 736/35, 736/36, 736/59, 736/43, 736/53, 735/99, 736/00, 736/02, 736/55, 736/57, 356/345, 356/352, 356/357, 356/358, 356/445
• US Class Current: 73/598
• 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 for detecting flaws in a medium using acoustic Doppler effect resulting from relative motion between the medium and the system comprising:

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; and

means, 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.

2. The flaw detection system using acoustic Doppler effect of claim 1 in which said transducer means includes a separate transmitter and receiver.

3. The flaw detection system using acoustic Doppler effect of claim 1 in which said transducer means is an ultrasonic transducer and said acoustic signal is an ultrasonic signal.

4. The flaw detection system using acoustic Doppler effect of claim 1 in which said transducer transmits an acoustic signal for propagation in said medium.

5. The flaw detection system using acoustic Doppler effect of claim 1 in which said transducer includes an acoustic receiver.

6. The flaw detection system using acoustic Doppler effect of claim 1 in which said means for detecting includes a spectrum analyzer for distinguishing the Doppler effect frequency.

7. The flaw detection system using acoustic Doppler effect of claim 6 in which said means for detecting includes a thresholding circuit for identifying a preselected level as a flaw.

8. The flaw detection system using acoustic Doppler effect of claim 1 in which said means for detecting includes a bandpass filter and a peak detector for distinguishing the Doppler effect frequency.

9. The flaw detection system using acoustic Doppler effect of claim 8 in which said means for detecting includes a thresholding circuit for identifying a preselected level as a flaw.

10. The flaw detection system using acoustic Doppler effect of claim 1 in which said means for detecting includes an A/D converter and a digital filter for distinguishing the Doppler effect frequency, and a thresholding circuit for identifying a preselected level as a flaw.

11. The flaw detection system using acoustic Doppler effect of claim 1 in which said medium is a railroad rail.

12. The flaw detection system using acoustic Doppler effect of claim 1 in which said transducer means transmits to the surface of the medium and receives from the surface of the medium an acoustic signal and the flaws detected are surface flaws.

13. The flaw detection system using acoustic Doppler effect of claim 1 in which said transducer means induces an acoustic signal internally in the medium and the flaws detected are internal flaws.

14. A flaw detection system for detecting flaws in a medium using acoustic Doppler effect resulting from relative motion between the medium and the system comprising:

acoustic transducer means, spaced from the medium to be inspected, for transmitting an acoustic signal to and receiving the reflected acoustic signal at a predetermined frequency from the surface of the medium to be inspected; and

means, responsive to the reflected acoustic signal, for distinguishing the Doppler shifted frequency in the reflected acoustic signal from the predetermined frequency of the transmitted acoustic signal representative of a surface flaw in the medium.

15. A flaw detection system for detecting flaws in a medium using acoustic Doppler effect resulting from relative motion between the medium and the system comprising:

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

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