SU723450A1 - Method of decreasing dead zone of echo pulse ultrasonic flaw detectors - Google Patents

Description

(54) METHOD OF REDUCING THE DEAD ZONE

ECHO-PULSE ULTRASONIC DEFECTOSCOPES

 The invention relates to instrumentation and can be used to control materials and products by ultrasonic echo pulse method.

A known method of reducing the dead zone of an echo-pulse ultrasonic flaw detector, which consists in exciting a combined piezo transducer with short electric radio pulses, removing electric radio pulses in a reception mode and achieving the duration of an excitation radio pulse 1 using various means.

The disadvantages of this method are: the impossibility of excitation of the piezoelectric transducer by pulses, the duration of which is less than the duration of the half period of its own resonant oscillations; reducing the sensitivity of the piezoelectric transducer due to the incomplete use of its resonant properties; limiting the dead zone of an echo flaw detector operating in the combined piezoelectric transducer mode and masking the reflected echo signal. The distribution of which is less than the intensity of the excitation radio pulse, which limits the scope of ultrasonic flaw detectors when testing thin-walled products

The purpose of the invention is to expand about; 7 parts of the use of echo-pulse ultrasonic flaw detectors.

This is achieved by the fact that a piezoelectric transducer excites a radio pulse, the filling frequency, which is an odd number of times less than its own resonant frequency, and radio pulses with a filling frequency equal to its own resonant frequency are removed from the piezoelectric transducer.

The drawing shows a structural diagram of the implementation of this method

The method is as follows.

Claims (1)

Piezo transducer 1 excites a generator of 2 radio pulses with a filling frequency, which is, for example, 3 times less than its own resonant frequency fpgj of a piezo transducer 1. In the reception mode, radio pulses are reflected from the same piezo transducer 1 reflected from the bottom of the product under test or from defects, but with a filling frequency equal to the resonant frequency fp of the piezoelectric transducer. Then the electrical signals from the piezoelectric transducer 1 are filtered using a narrow-band filter 3, tuned to the frequency and fed to the input-amplifier 4 of the flaw detector. At the same time, the excitation radio pulse with a filling frequency of which f does not pass to the input of amplifier 4, and as a result, the effect of masking reflected echo pulses, the propagation time of which is less than the duration of the exciting radio pulse, is excluded. The implementation of the proposed method makes it possible in principle to reduce the dead zone of the flaw detectors and reveal defects located at depths of the order of 0.15-0.3 mm from the surface of the input of ultrasonic vibrations. The method for reducing the dead zone of an echo-pulse ultrasonic flaw detector, which consists in exciting a combined electric piezo transducer with short electric radio pulses and removing electric radio pulses from it in a reception mode, characterized in that, in order to expand the field of application, the piezo transducer excites a pulse. of which the odd number of times is less than its own resonant frequency, and radio pulses are removed from the piezotransducer olneni equal to its own resonant frequency. Sources of information taken into account during the examination 1. Schreiber DS Ultrasonic flaw detection. M., Metallurgists, 1965 / (prototype).