Ultrasonic signal processing system including a flaw gate

• US 4,803,638 A
• Filed: 06/26/1986
• Issued: 02/07/1989
• Est. Priority Date: 06/26/1986
• Status: Expired due to Fees

• Current Assignee: Westinghouse Electric Corporation (Paramount Global (f/k/a ViacomCBS Inc.))
• Original Assignee: Westinghouse Electric Corporation (Paramount Global (f/k/a ViacomCBS Inc.))
• Inventors: Michaels, Thomas E., Nottingham, Lawrence D., Michaels, Jennifer E.
• Primary Examiner(s): Lall, Parshotam S.
• Assistant Examiner(s): Ramirez, Ellis B.
• Application Number:
  US06/878,817
• Time in Patent Office: 957 Days
• Field of Search: 364/507, 364/502, 73/607, 73/611, 73/612, 73/615, 73/628, 73/596, 128/660
• US Class Current: 702/36
• CPC Class Codes: G01N 2291/02854 Length, thickness
• CPC Class Codes: G01N 2291/2693 Rotor or turbine parts
• CPC Class Codes: G01N 29/22 Details , e.g. general constructional or apparatus details
• CPC Class Codes: G01N 29/38 by time filtering, e.g. using time gates
• CPC Class Codes: G01N 29/4454 Signal recognition, e.g. specific values or portions, signal events, signatures
• CPC Class Codes: G01N 29/4463 Signal correction, e.g. distance amplitude correction [DAC], distance gain size [DGS], noise filtering

Abstract

An ultrasonic signal processing system that includes flaw gates that process signals from an inspection transducer is disclosed. The flaw gates operate in pairs where each pair is dedicated to a time window corresponding to, for example, flaw depth or transducer angle. The time window for a pair of flaw gates is indicated by a channel code produced by a timing control unit. One flaw gate in each pair processes incoming digitized transducer signals during a scan to produce reflector indications while the other gate in each pair transfers data from a previous different position scan to a main computer. The main computer determines flaw locations from the reflector indications and transducer positions provided by the flaw gate. The flaw gates each adjust reflector indication location signals for changes in distance between an immersed ultrasonic wave inspection transducer and the surface of the material being inspected as well as record the location of the inspection transducer at the time of each indication detection. The flaw gates produce the indication by comparing the digitized transducer signal waveform with a threshold curve where an indication is an excursion of the signal waveform above the threshold. The flaw gates each contain a comparator that indicates when the window is open and activates a waveform memory that automatically stores the digitized transducer signals during the window.

Claims

1. An ultrasonic signal processing system for an ultrasonic transducer, comprising:

transducer control and signal digitizing means for controlling transmit signal production, digitizing reflection signals and indicating transducer position; and

flaw indication processing means for storing the digitized reflection signals as a reflection waveform, comparing the reflection waveform to a threshold waveform, producing and storing flaw indications when the reflection waveform exceeds the threshold waveform, and storing the transducer position in association with the flaw indications.

2. An ultrasonic signal processing system for an ultrasonic transducer, comprising:

transducer control and signal digitizing means for controlling transmit signal production, digitizing reflection signals and indicating transducer position; and

flaw indication processing means for storing the digitized reflection signals as a reflection waveform, comparing the reflection waveform to a threshold waveform, producing and storing flaw indications when the reflection waveform exceeds the threshold waveform, storing the transducer position in association with the flaw indications, storing a transit time offset curve including a ranging offset and adjusting the start of the threshold waveform comparison before comparison by the ranging offset that is a function of transducer position.

3. An ultrasonic signal processing system for an ultrasonic transducer, comprising:

transducer control and signal digitizing means for controlling transmit signal production, digitizing reflection signals, indicating transducer position, and producing a window indicator designating a window during which said flaw indication processing means is to be activated; and

flaw indication processing means for storing the digitized reflection signals as a reflection waveform, comparing the reflection waveform to a threshold waveform, producing and storing flaw indications when the reflection waveform exceeds the threshold waveform, and storing the transducer position in association with the flaw indications, said flaw indication processing means comprising;

waveform window detection means for detecting the window indicator;

a waveform memory unit operatively connected to said transducer control and signal digitizing means and said waveform window detection means, and storing the digitized reflection signals during the window;

a position latch operatively connected to said transducer control and signal digitizing means and storing the transducer position;

a storage memory storing the threshold waveform, the flaw indications and the position;

a processor, operatively connected to said waveform detection means, said waveform memory unit, said position latch and said storage memory, performing the comparison and storing the flaw indications in said storage memory.

4. A system as recited in claim 3, wherein said window is a time/depth window.

5. A system as recited in claim 3, wherein said waveform window detection means comprises:

a channel latch, operatively connected to said processor and loaded with a channel code by said processor; and

a comparator operatively connected to said channel latch and to said transducer control and signal digitizing means, and comparing the window indicator to the channel code and activating said waveform memory unit when coincidence occurs.

6. A system as recited in claim 5, wherein said transducer control and signal digitizing means produces a write signal when a reflection signal sample is available for storage and said waveform memory unit comprises:

a waveform memory operatively connected to said transducer control and signal digitizing means and storing the reflection signal sample when the write signal is received; and

an address counter operatively connected to said waveform memory, said comparator and said transducer control and signal digitizing means, designating the location at which the reflection signal sample is stored and being incremented by the write signal in accordance with the activation by said comparator.

7. A system as recited in claim 3, further comprising:

data access means, operatively connected to said processor and said storage memory, for disabling said processor and retrieving the reflector indications and the position from said storage memory.

8. An ultrasonic signal processing system, comprising:

a control processor;

a timing control unit connected to said control processor and producing timing control signals including window signals;

a pulse control unit connected to and controlled by said timing control unit;

an inspection transducer connected to and controlled by said pulse control unit and producing a received signal;

a resolver coupled to said inspection transducer and producing a position of said inspection transducer;

an analog multiplexer connected to said timing control unit and said inspection transducer, and attenuating the received signal in dependence on the window signals;

a digitizer connected to said analog multiplexer and digitizing the attenuated received signal; and

plural flaw gates, connected to said digitizer, said timing control unit and said resolver, each storing and processing, in dependence on one of the window signals, the digitized attenuated received signals by shifting a threshold waveform in dependence on a ranging offset and comparing the stored digitized attenuated received signals to the shifted threshold waveform and producing flaw indications when the digitized received signals exceed the threshold waveform, and storing the position, said control processor retrieving the flaw indications and corresponding position at the end of a scan by said inspection transducer and determining flaw locations from the positions and flaw indications.

9. A method of processing transducer signals to determine flaw indications, said method comprising the steps of:

(a) storing the transducer signals as a sample waveform;

(b) shifting a threshold waveform in dependence on a ranging offset; and

(c) comparing the threshold and sample waveforms and storing peak amplitude and peak amplitude time of excursions of the sample waveform above the threshold waveform as flaw indications.

10. A method as recited in claim 9, wherein step (a) is performed during a time window corresponding to the depth of the indications.

11. A method as recited in claim 9, wherein step (c) includes storing a rising crossing time of the excursion and a falling crossing time of the excursion.

12. A method of determining flaw indications in a material being inspected using an inspection transducer and a ranging transducer, comprising the steps of:

(a) obtaining a ranging offset of the material from the ranging transducer at a position;

(b) activating the inspection transducer to produce an inspection signal at the position;

(c) sampling the returned inspection signal during a sample window to produce a digital return signal sample waveform;

(d) shifting a digital return signal sample waveform using the ranging offset;

(e) comparing a threshold waveform to the shifted return signal sample waveform;

(f) storing the peak amplitude and peak time of excursions of the shifted return signal sample waveform above the threshold waveform;

(g) repeating steps (b)-(f) at different positions; and

(h) transferring the peak amplitudes, peak times and positions to a flaw location determination device.

13. An ultrasonic signal processing system for an ultrasonic transducer, comprising:

transducer control and signal digitizing means for controlling transmit signal production, digitizing reflection signals and indicating transducer position; and

flaw indication processing means for storing the digitized reflection signals as a reflection waveform, comparing the reflection waveform to a threshold waveform, and producing and storing flaw indications when the reflection waveform exceeds the threshold waveform.