RU2557679C1 - Method for automated ultrasonic inspection of flat articles - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: method includes scanning flat articles with an ultrasonic transducer in two mutually perpendicular directions: back-and-forth across and discrete rectilinear along the inspected article. A thick-walled inspected article is scanned with multiple ultrasonic transducers mounted in a single acoustic unit in one row equidistant from each other and fitted with separate clamps to the surface of the inspected article which provide them with three degrees of freedom when scanning, wherein scanning of the acoustic unit along the inspected article is carried out with alternating odd short and even long steps, after which the actual longitudinal coordinates of the detected defects are determined as the sum of current coordinates of the first transducer and the distance between the centres of the first transducer and the transducer which detected the defect.

EFFECT: more reliable inspection, avoiding a dead inspection zone, rejection of flat articles and missing defects.

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Description

The invention relates to the field of ultrasonic quality control of workpieces and semi-finished products, in particular automated ultrasonic control of large-sized flat products, and can be widely used in mechanical engineering and other industries.

The known method [1] of shadow ultrasonic testing of products, which consists in installing two pairs of transducers relative to the product according to scheme X, emitting ultrasonic vibrations into the product, receiving past vibrations, adjusting the transducers to the maximum amplitude of the transmitted signal, recording the time of detection of a defect by one pair of transducers , then moving the product to another pair of transducers, they record the time of detection of the defect and determine the depth of effect. Receiving transducers are installed on opposite sides of the product, the converters are tuned by turning the receiving transducer of the second pair relative to the normal to the surface of the product and moving it relative to the radiating transducer of the first pair until the maximum amplitude of the signal reflected from the surface is received, while the receiving transducer of the second pair receives oscillations emitted by the transducer the first pair and reflected from the surface of the product.

The specified method has several serious disadvantages:

- the implementation of the method for automated ultrasonic testing requires a complex equipment design;

- when automating shadow ultrasonic testing, the dimensions of the equipment increase at least two times in comparison with the dimensions of the controlled object due to the need to use the roller table;

- unreasonably high material and financial costs for the implementation of the method in the automated ultrasonic control of large sheets and flat products.

There is also known a method [2] of automated ultrasonic inspection of sheets, including scanning by an ultrasonic transducer in two mutually perpendicular directions: reciprocating across the sheet and discrete rectilinear along it, emitting and receiving ultrasonic vibrations along the sheet, reading the current coordinates across and along it using sensors paths, recording the current coordinates of the detected defects across the sheet and the actual coordinates along the sheet as the sum of the current coordinates for the path sensor in this direction and the distance from the transducer to the defect, the formation of control signals for scanning the transducer during the initial detection of defects to reduce the scanning step along the sheet by an amount smaller than the distance from the transducer to the defect, re-detection of a previously detected defect during reverse transverse scanning, comparison of parameters and coordinates one and the same defect obtained during primary and secondary detection, if they coincide, the defect parameters and the coordinates nayutsya you end to control simultaneously a signal is generated for marking a defect location on the sheet surface, and the scanning step along the sheet returns to the previous value, after its closure control results are printed on a printer in the form defectogram and control protocol.

The method [2] of automated ultrasonic inspection of sheets has clear advantages over the method [1] of shadow ultrasonic inspection of products. It is intended for automated ultrasonic testing of sheets that, during the monitoring process, maintain a state of rest and do not require mechanisms for moving them like roller tables, and the transducer is scanned by moving them along one of the surfaces in two mutually perpendicular directions: across and along the controlled object, except Moreover, by changing the magnitude of the scan step when a defect is detected, the reliability of the control increases.

However, along with the available advantages, the method [2] has its drawbacks:

- designed for ultrasonic quality control of sheets;

- control is carried out by one ultrasonic transducer, which reduces the performance of the control of flat products;

- radiation and reception of ultrasonic vibrations is carried out along the sheet by Lamb waves.

Despite the disadvantages, the method [2] of automated ultrasonic inspection of sheets is the closest analogue of the present invention and therefore is taken as a prototype.

The task of the invention is to remedy these disadvantages of the analogue and prototype, which is achieved by the following technical solutions:

- control is carried out by several ultrasonic transducers installed in a single acoustic unit in one row at an equal distance from each other;

- the transducers are equipped with individual clamps to the surface of the monitored flat product, providing the transducers with three degrees of freedom when scanning the acoustic unit;

- scanning ultrasonic transducers along a flat product is carried out with a variable step: each odd step is short, and each even step is long to the total total length of all transducers;

- the coordinates along the flat product of each detected defect are determined as the sum of the current coordinate of the first transducer and the distance between its center and the center of the transducer that detected the defect.

The proposed method is illustrated in graphic materials.

Figure 1 presents a diagram of the proposed control method, where: 1 - controlled flat product, such as a stove; 2 - block of ultrasonic transducers P1, P2, ..., Pn; 3 - the scanning path of the block of ultrasonic transducers P1, P2, ..., Pn on the surface of the monitored flat product 1; c is the length of the short step, d is the length of the long step; 4 - path sensor (encoder) across a flat product 1, reading the current coordinates of block 2; 5 is a path sensor (encoder) that reads the current coordinates of block 2 along the flat product 1. Moreover, each of the ultrasonic transducers P1, P2, ..., Pn is connected to its channel of multichannel flaw detection equipment (not shown in Fig. 1), made on the basis of technological computer.

Figure 2 presents the remote element I of figure 1, where 2 is an acoustic unit, P1, P2, ..., Pn are ultrasonic transducers installed in block 2, a is the length of the ultrasonic transducers, b is the distance between two adjacent transducers in block 2 .

The method is implemented as follows.

Before conducting automated ultrasonic testing in manual mode, the sensitivity of a multichannel ultrasonic flaw detector (not shown in Fig. 1), made on the basis of a technological computer, is adjusted on samples of the KSO-2 type according to GOST 21397-81. To do this, samples with flat-bottomed artificial reflectors of the required normative documentation of the diameter are taken, at different depths depending on the thickness of the monitored flat product 1. The transducers P1, P2, ..., Pn are connected to the flaw detector, they are taken out from block 2, and the sensitivity of the corresponding flaw detector channel is adjusted and return back to block 2.

Tuning of flaw detection equipment is carried out using two strobe ASD. One of them is installed in the control zone, and it is triggered when its level is exceeded by the amplitude of the echo signal from the defect, the second is installed in the zone of the bottom echo signal, and it is triggered by a rapid decrease in the bottom echo signal below the second strobe of the ASD. Registration of a defect is carried out by the operation of two ASD gates or by the operation of one ASD gate in the zone of the bottom echo pulse. This setting eliminates the registration of defects from random single signals in the control zone, on the one hand. On the other hand, the registration of a defect during the operation of the ASD in the zone of the bottom echo signal ensures the detection of a defect over the entire thickness of the monitored flat product in the near and far uncontrolled “dead” zones by the echo method.

To conduct ultrasonic testing, block 2 of ultrasonic transducers P1, P2, ..., Pn is installed on the surface of a flat product 1 (Fig. 1) in the zone of the beginning of control and they scan the surface of a flat product 1 along path 3. Scanning of transducers P1, P2, ..., Pn across the flat product 1 are driven back and forth, reading the current coordinates by the path sensor 4 (encoder), and along the flat product 1 - discretely alternately alternating odd short and even long steps c and d (figure 1), reading the current coordinates of the sensor com 5 way (encoder). At the same time, having scanned the transducers from left to right across the flat product, block 2 is moved one short step along the flat product 1 in order to check the missing gaps between the transducers during the reverse run from right to left, after which block 2 is moved to the entire total length of the transducers P1, P2, ... , Pn. The next odd step is short again. The length of the short and long steps is determined respectively from the ratios (figure 1, figure 2):

, $$d=n(a+b)$$

, $$c=\frac{a+b}{2}$$

, $$d=n(a+b)$$

,

where a is the length of the transducer;

b is the distance between adjacent transducers;

c is the length of the short step;

d is the length of the long step;

n is the number of converters in block 2.

As a result of scanning block 2 along trajectory 3, the entire surface of the flat product 1 is completely scanned by transducers P1, P2, ..., Pn. At the same time, during the scanning process, ultrasonic transducers P1, P2, ..., Pn emit ultrasonic vibrations along the normal to its surface into the metal of the flat product 1. Ultrasonic vibrations, propagating along the depth of the metal of the flat product 1, are reflected from its opposite surface and from defects of a metallurgical nature and in the form of delaminations, if any. The reflected echo signals are returned to the transducers P1, P2, ..., Pn, converted into electrical signals in the form of pulses and fed to the inputs of the receiving channels of the flaw detection equipment. Flaw detection equipment receives echo signals in the form of electrical impulses, analyzes them, determines the presence of defects, their parameters: equivalent value, occurrence depth, coordinates, remembers them and after the end of control documents its results on the printer in the form of a protocol and defectograms. Since each transducer П1, П2, ..., Пn is individually pressed to the surface of the monitored flat product 1, their acoustic axes, in the presence of warping (waviness), deviate little from the perpendicular to the surface of the section where one or another of the transducers П1, П2, ..., Pn, and the gap between the working surface of the transducer and the surface of the flat product 1 at each point is minimal. As a result, the reliability of the control increases in the presence of the warping (surface curvature) of the monitored flat product, and the "dead" zone that is not controlled by the echo method decreases.

Thus, the proposed method of automated ultrasonic testing due to the variable step of scanning the transducers along a flat product, three degrees of freedom and individual pressure of the transducers to the surface of the controlled flat product, determining the actual longitudinal coordinates of the detected defects as the sum of the current longitudinal coordinate of the first transducer and the distance between the centers of the transducer P1 and the transducer, which detected a defect, increases the reliability of control, using Luciano "dead zone" control perebrakovku flat products and skipping defects.

Information sources

1. USSR author's certificate No. 1045121 "Method for shadow ultrasonic testing of products", cl. G01N claimed 06/21/1982.

2. RF patent No. 2376596 "Method for automated ultrasonic inspection of sheets", cl. G01N, priority dated 02.29.2008.

Claims (1)

A method for automated ultrasonic testing of flat products based on their scanning by an ultrasonic transducer in two mutually perpendicular directions: reciprocating transverse and discrete linear along the controlled product, emitting into it and receiving ultrasonic vibrations, reading the current coordinates of the ultrasonic transducer of ultrasonic vibrations along and across the controlled product using track sensors, registering the current coordinates of the detected defects, remember determining defect parameters before the end of the inspection and printing the results of the inspection after it is completed in the form of a protocol and a defectogram, characterized in that the scanning of a thick-walled controlled product, for example a plate, is carried out by several ultrasonic transducers installed in a single acoustic unit in one row at an equal distance from each other and equipped with individual clamps to the surface of the controlled product, providing them with three degrees of freedom during scanning, while scanning acoustics a unit along the controlled product is carried out alternately - alternating odd short and even long steps, and the length of the short and long steps is determined respectively from the ratios:
$$c=\frac{a+b}{2}$$

, $$d=n(a+b)$$

,
where a is the length of the transducer;
b is the distance between adjacent transducers;
c is the length of the short step;
d is the length of the long step;
n is the number of converters in the block,
after which the actual longitudinal coordinates of the detected defects are determined as the sum of the current coordinates of the first transducer and the distance between the centers of the first transducer and the transducer that detected the defect.

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