SU461348A1 - The method of quality control of the surface layer of materials - Google Patents

Description

one

This invention relates to ultrasonic flaw detection of materials and products.

The method of quality control of the surface layer of materials is known, which implies that an ultrasonic wave is excited in the layer and its reflection is received from defects, the disadvantage of which is a narrowed field of application due to the difficulties of excitation of waves in materials with a low ultrasonic propagation velocity,

The described method differs from the known method in that it excites surface-longitudinal waves in the surface layer of the material being monitored and, by the presence of their reflections, judges the surface layer, and in turn excites surface-type Rele waves, The difference between the propagation times of the pulses of the surface and surface-longitudinal waves and along it, as well as the known velocities of the surface-longitudinal and surface waves, is determined by determining the location of the defect. This broadens the field of application and simplifies the process of detecting defects in materials with low ultrasound velocity, for example in plastics.

FIG. 1 shows a device for implementing the proposed method; in fig. 2 - type of pulses on the oscilloscope screen.

The device contains a pulse generator 1, an amplifier 2 connected to the generator 1, an indicator 3 (oscilloscope) connected to the amplifier 2, a receiving-studying converter 4 connected to the generator 1 and the amplifier 2, an immersion liquid 5 and a test sample 6. On the oscilloscope screen The number 7 shows the probe pulse, 8 - the pulse of surface-longitudinal waves, reflected from de), and 9 - the pulses of surface waves, reflected from the same defect.

From the piezoelectric transducer 4 at an angle a, an ultrasonic wave is directed into the liquid 5, which falls on the interface of the liquid 5 - a controlled sample 6 and is transformed into a longitudinal and transverse waves. With a smooth rotation of the transducer 4, an angle a is selected such that the longitudinal waves in the controlled material are reflected and the maximum conversion of the longitudinal waves propagating in the liquid 5 into surface-longitudinal waves occurs. Surface-longitudinal waves propagating in the surface layer of the test sample 6 are reflected from the defects in this layer and returned to the transducer 4. This moment is detected by the appearance of a pulse on the display of the indicator 3, and by observation it is judged

the existence of defects. In order to determine the location of the defect by smooth rotation of the transducer near the axis located at the boundary of the sample and liquid under test, surface-longitudinal waves and surface waves of the Rele type are excited in turn. The distance from the place of incidence of the ultrasonic central beam to the defect a is found from the formula:

CiCzf

but

2 / Ci-C2

e Ci - the speed of the surface-longitudinal

waves;

Cz is the speed of the surface waves (Ci and Cz are known for the product under control),

The i-difference between the propagation time of the surface wave pulse (see pulse 9 in Fig. 2) and the pulse propagation time of surface-longitudinal waves (see pulse 8) from the transducer to the defect, which is measured by any known method.

Subject matter

1. A method of controlling the quality of the surface layer of materials, which consists in exciting an ultrasonic wave in the layer and producing reception of its reflection from defects, characterized in that, in order to broaden the field of application and simplify the process of detecting defects in materials with a low ultrasound velocity, for example, in plastics, surface-longitudinal waves are excited in the surface layer of the material being monitored, and judging by the presence of their reflections, the surface layer is defective.

2. Method 1), characterized in that the surface-longitudinal and top-of-the-other waves of the Rehle type are excited in turn, measure the difference between the propagation times of the surface and surface-longitudinal-wave pulses and over it, as well as by the known speeds of the surface-longitudinal and surface waves, locate the defect.

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