Detecting abnormality

• US 3,940,952 A
• Filed: 10/23/1973
• Issued: 03/02/1976
• Est. Priority Date: 10/23/1973
• Status: Expired due to Term

• Current Assignee: Battelle Memorial Institute
• Original Assignee: Battelle Memorial Institute
• Inventors: Mitchell, Drury K.
• Primary Examiner(s): Queisser, Richard C.
• Assistant Examiner(s): Kreitman, Stephen A.
• Application Number:
  US05/408,292
• Time in Patent Office: 861 Days
• Field of Search: 73/67.7, 73/67.8 R, 73/67.8 S, 73/67.9, 73/71.5 US, 73/67.2, 310/8, 310/8.2, 310/8.3, 310/8.7
• US Class Current: 73/629
• CPC Class Codes: G01N 2291/044 Internal reflections (echoes), e.g. on walls or defects
• CPC Class Codes: G01N 29/0645 Display representation or displayed parameters, e.g. A-, B- or C-Scan
• CPC Class Codes: G01N 29/07 by measuring propagation velocity or propagation time of acoustic waves
• CPC Class Codes: G01N 29/11 by measuring attenuation of acoustic waves
• CPC Class Codes: G01N 29/449 Statistical methods not provided for in G01N29/4409, e.g. averaging, smoothing and interpolation

Abstract

Apparatus for detecting an abnormality such as a discontinuity in a predetermined region of a material by directing an elastic mechanical wave, such as an ultrasonic or other acoustic wave, in a series of pulses to portions of the region and providing response to the wave pulses reflected therefrom. The amplitudes of pulses reflected from a normal portion of the region may approximate the amplitudes of pulses reflected from a portion where an abnormality is present and thus make it difficult to distinguish between such portions.

The directed wave is varied, as by rotating a transducer having an irregular cross-sectional radiation pattern, to provide randomlike variations in the shapes of successive pulses where reflected from a normal portion, differing detectably from any variations caused in the pulses where reflected from an abnormal portion.

Means responsive to a plurality of successive reflected pulses are provided for effectively superimposing them, either electrically or in an overlaid visual display, the types of wave shapes of the superimposed pulses being indicative selectively of a normal or an abnormal portion of the region.

Claims

1. In apparatus for detecting a selected type of abnormality in a predetermined region comprising transmitter means for directing an elastic mechanical wave in a series of pulses to portions of the region and receiver means for providing response to the wave pulses reflected therefrom, wherein the amplitudes of pulses reflected from a portion of the region where such type of abnormality is absent (a normal portion) may approximate the amplitudes of pulses reflected from a portion where such type of abnormality is present (an abnormal portion) and thus make it difficult to distinguish between normal and abnormal portions, the improvement comprising

in the transmitter means, mechanical wave radiating means providing an irregular cross-sectional radiation pattern,

means for providing relative transverse repetitive motion between the radiating means and a given portion of the region while a series of pulses are directed to the same portion of the region, superimposed on any scanning movement from portion to portion of the region, to provide randomlike variations in the shapes of successive pulses where reflected from a normal portion of the region differing detectably from any variations caused in successive pulses where reflected from an abnormal portion, and

means responsive to a plurality of successive reflected pulses for effectively superimposing them, the types of wave shapes of the superimposed pulses being indicative selectively of a normal or an abnormal portion of the region.

2. Apparatus as in claim 1, wherein the radiating means comprises means for radiating an acoustic wave to the region.

3. Apparatus as in claim 1, wherein the receiver means includes means for converting the reflected wave pulses to electrical pulses.

4. Apparatus as in claim 1, wherein the motion-providing means comprises means for rotating the radiating means.

5. Apparatus as in claim 1, wherein the radiating means comprises a transducer that converts a first electrical pulse to a mechanical pulse, then receives the reflected mechanical pulse and converts it to an electrical pulse, then converts a second electrical pulse, and so on, alternatively transmitting and receiving, whereby the motion-providing means varies not only the directed wave but also the receiving conversion characteristics and thus provides randomlike variations also in the reception of the reflected pulses.

6. Apparatus as in claim 1, wherein the effectively superimposing means comprises means for providing an overlaid visual display of the shapes of the successive reflected pulses.

7. Apparatus as in claim 6, wherein the display means comprises means for providing a graph of amplitude as a function of depth in a portion of the region, so that the randomlike variations cause apparent motion in the graph that is discriminably different for normal and abnormal portions of the region;

the apparent motion for a normal portion of the region being substantial and erratic in both the amplitude direction and the depth direction; and

the apparent motion for an abnormal portion being substantial but cyclic in the amplitude direction, providing the maximum obtainable amplitude, and insubstantial in the depth direction.

8. Apparatus as in claim 3, wherein the effectively superimposing means comprises means for combining the converted successive reflected pulses electrically.

9. Apparatus as in claim 8, wherein the effectively superimposing means comprises also means responsive to the electrically combined pulses for indicating the location of an abnormal portion of the region.

10. Apparatus as in claim 8, wherein the combining means comprises means responsive to the randomlike variations to cause substantial and erratic variations in both the amplitude and the time of the peaks of the combined pulses for a normal portion of the region, and to cause substantial but cyclic variations in the amplitude, providing the maximum obtainable amplitude, and only insubstantial variations in the time of the peaks of the combined pulses for an abnormal region.

11. Apparatus as in claim 10, wherein the effectively superimposing means comprises also means responsive to the amplitude and the time of the peaks of the combined pulses for indicating the location of an abnormal portion of the region.