SU1644022A1 - Method and device for flaw detection using acoustic emission signals - Google Patents

Abstract

The invention relates to non-destructive testing and can be used in determining the coordinates of developing defects of various products. The purpose of the invention is to increase the reliability of control by eliminating extreme acoustic emission events on piezoelectric transducers 1, 2 and 3 located at the vertices of the triangle, with the times of propagation of control ultrasonic signals between them. This comparison is carried out in comparison unit 8 in accordance with the algorithm stored in memory blocks 4 and 10. 2 sec. f-ly, 1 ill., 1 tab. § (L

Description

The invention relates to the field of non-destructive testing and can be used in determining the coordinates of the developing defects of various products.

The purpose of the invention is to increase the reliability of control by eliminating false acoustic emission events.

The drawing shows a block diagram of a device for monitoring product defects by acoustic emission signals.

The device for monitoring product defects contains three receiving-amplifying channels, each of which consists of series-connected piezoelectric transducers 1-3 and driver amplifiers connected to the outputs of the latter by measuring 7 of the arrival time difference (RTD) of acoustic emission signals and the comparison unit 8, the input of which is connected to the output of the RVP meter 7, the calculator 9, the information input connected to the output of the RVP meter 7, and the recording resolution input - with the output of the comparison unit 8, the first memory block 10, the output Inonii to a second input of the comparator 8 are connected in series generator 11 clock pulses (GTI), the counter 12 and the second block memory 13. The output of the latter is connected by a common line to the control input of the meter 7 of the RVP and the input of the first memory block 10, the second output of the comparison block 8 is connected to the second input of the counter. The transducers are located on the surface of the controlled product at the vertices of the triangle.

The device works as follows.

The signals from the acoustic emission source at the site of the developing defect are taken by a group of transducers 1-3, converted into electrical signals, amplified, filtered, and if their values exceed the threshold level, converted to. logical impulses in amplifier x -formers 4-6. Then, in the RVP meter 7, pulses with a duration equal to the RVP between the respective converters are formed in each channel, which are then supplied, for example, in a digital code to the information input of the calculator 9 and the comparison unit 8. The second input of the latter is supplied with information recorded in the cells of the first block 10 memories. Previously, before the control, time was measured - | the passage of acoustic waves between transducers 1-3. If the distances between the transducers are 1 and 2-a, 1, 3-3, 2-3-s, and the speed of propagation of acoustic waves, v, then the signal transit times are equal to a / v, b / v, and c / v, respectively.

 In the first line of the first block of memory 10, the values are successively entered: 0, a / v, b / v; in the second line - a / v, 0, c / v; in the third line - b / v, c / v, 0 (see table).

Designations adopted in the table:

i - line number;

j is the element number in the line;

a is the distance between transducers 1 and 2;

B is the distance between converters 1 and 3;

c is the distance between transducers 2 and 3;

v is the speed of propagation of acoustic waves in the material of the controlled product.

After measuring all three RVP with the meter 7 from the second output of the comparison unit 8, the starting address of the cells of the second memory block 13 is set at the second input of the counter 12 and the clock pulse generator 11 starts working, changing the code at the output of the counter 12. Depending on this code from the output of the second block 13 memory through the main line to. the control input of the meter 7 RVP and the input of the first memory block 0 receive codes that set the value of A, | at the second input of the block 8 for comparison of the RTD of one of the receiving-amplifying channels and at the second input of the comparison block 8; - an element of the i-th row of the column of the first memory block 10. Thus, if one submits alternately to the first input of the RTU comparison unit 8 from the first, second and third receiving and amplifying channels and simultaneously to the second inputs of the comparison unit 8, the first row elements of the first memory block 10, then similarly three RTDs and second row elements and then Since the three RTDs and elements of the third row can be compared in block 8 of the comparison, all possible RTDs and weed out false events.

If, for example, it turns out that the RVP of the first channel is not greater than the value of the first cell of any row, the RVP of the second channel is not greater than the value of the second cell of the same line, and the RVP of the third channel is not greater than the value of the third cell, then the input of the recording resolution of the transmitter 9 from the first the output of the comparator unit 8 receives a signal to enable the recording of information on this acoustic emission event. If at least one element A in the line is less than the corresponding RVP, then the second input of the counter receives the e comparison block the address of the next line and the comparison of the cells of this line with the RWP continues. Consequently, if the RTD condition is satisfied element by element three times in a line, where k is the number of the receiving-amplifying channel, a resolution signal appears on the calculator 9. Then the source location can be found by dividing the entire control zone into sectors or using a computing device known triangulation formulas.

Claims (2)

Invention Formula 5. A method for monitoring product defects by acoustic emission signals, which means that three piezotransducers are placed at the corners of the triangle on the surface of the tested product, they receive signals of acoustic emission events, measure the differences in arrival times of these signals on piezoelectric transducers, r 5 0 five 0 five Second, the location of defects is determined, characterized in that, in order to increase reliability, the transit time of acoustic signals between each pair of piezo transducers is preliminarily measured, and after measuring the differences in arrival times of acoustic emission signals, acoustic emission events for which at least one time difference are rejected arrival, is not equal to zero, more than the time of passage of the acoustic signal between the corresponding piezoelectric transducers. 2. A device for monitoring product defects by acoustic emission signals, comprising three channels, each of which contains a serially connected transducer and a booster amplifier, as well as a series-connected meter of the difference in the time of arrival of acoustic emission signals and a calculator that are serially connected to the first memory block and block comparison, and the second memory block, the output of the amplifier —former of each fecal is connected to the corresponding input of the meter of the difference between the arrival times of the signals emissive, and the transducers are located at the corners of a triangle, characterized in that it is provided with series-connected clock pulses and a counter, the second input of which is connected to the first output of the reference unit, and the output of the counter is connected to the input of the second memory unit with the control input of the meter of differences in the arrival times of acoustic emission signals and with the input of the first memory block, the second input of the comparator unit is connected to the output of the meter of the time difference pr stroke acoustic emission signals and the second output of comparing unit - to the input resolution calculator. Editor V.Danko Compiled by G. Maximochkin Tehred L. Oliynyk Proofreader O. Tsiple Order 1236 Circulation 400 VNIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moscow, Zh-35, Raushsk nab. 4/5 Subscription