RU2256173C1 - Method for ultrasound control of quality of welded seams in thin-walled products - Google Patents

Abstract

FIELD: acoustic methods of non-destructive control.

SUBSTANCE: method includes mounting a piezo-converter at an angle to product in such a way, that only transverse waves are transferred through product. In each control point full realization of reflected ultrasound signal is fixed, smoothing and separation of contour line of this realization is performed and after scanning whole section of welded seam section image is built. Bounds area with presence of pores are determined by calculation of centers of gravity of images of external and internal surfaces of product. Search for maximums of amplitude of signals in this area is performed. On basis of coordinates of gravity centers of images, containing maximums of signals, coordinates and size of pores are determined.

EFFECT: higher precision, broader functional capabilities.

2 dwg

Description

The invention relates to acoustic methods of non-destructive testing and can be used to determine the quality of the welds of the fuel elements VVER-1000, VVER-440.

A known method of ultrasonic testing of welds (“Defectoscopy”, 1979, No. 10, p.7), which consists in moving the ultrasonic finder over the weld, at the same time sounding it and judging by the presence of the reflected signal on the quality of the weld. The disadvantage of this method is the impossibility of detecting defects of the “time” type.

The closest in technical essence and the achieved result is a method of controlling welds according to A.S. No. 920520, MKI G 01 N 29/04 (prototype), which consists in moving an ultrasonic finder focused on the inner wall of the product across the weld normally to its surface, at the same time it also sounds in the number and shape of the extrema of the obtained dependence of the reflected bottom signals determine the quality of the weld. The disadvantage of this method is the inability to detect defects of the “pore” type, since the amplitude of the signals reflected sometimes does not exceed the amplitude of the intrinsic noise of the ultrasonic tract.

An object of the invention is to identify defects of the “pore” type in thin-walled products with a wall thickness of less than 1 mm.

The problem is solved in that the piezoelectric transducer is installed at an angle to the product so that only transverse waves propagate in the product, at each control point the full realization of the reflected ultrasonic signal is recorded, the envelope of this implementation is smoothed and selected, and after scanning the entire section of the weld, a section image is built , determine the boundaries of the pore presence region by calculating the centers of gravity of the images of the external and internal surfaces of the product, search for amplitudes maxima Udy signals in this field and coordinates of the center of gravity of the image containing the signal maxima, and determine the coordinates of pore sizes.

The specified set of features is new, not known from the prior art and allows us to solve the problem, since the dead zone from the outer surface of the product decreases, the useful signal from the pores is detected against the background of the intrinsic noise of the ultrasonic tract and the coordinates of the pores are determined.

The invention is illustrated graphic materials.

Figure 1 presents the control circuit with recording the full implementation of the reflected ultrasonic signal.

Figure 2 presents an example of recording one section of a weld.

The method is implemented as follows.

The piezoelectric transducer is installed at an angle to the product so that only transverse waves propagate in the product, the piezoelectric transducer is moved over the weld with the simultaneous emission and reception of ultrasonic signals, at each control point, the complete implementation of the reflected ultrasonic signal and the position coordinate of the piezoelectric transducer (scan step number) are recorded.

Next, for each implementation of the reflected ultrasonic signal, linear smoothing and envelope extraction are performed according to the formula

,

,

- n-е отсчеты соответственно огибающей, наблюдаемого сигнала и сигнала, сопряженного ему и определяемому дискретным преобразованием Гильберта.where e [n], s [n], and

- nth samples, respectively, of the envelope, of the observed signal, and of the signal conjugated to it and determined by the discrete Hilbert transform.

,

,

where h [n] is the impulse response of the Hilbert transform defined by the expression

The resulting envelope of this implementation and the scanning step (coordinate of the position of the piezoelectric transducer) are stored.

After the entire section of the weld is scanned by the piezoelectric transducer (one scan line), a two-dimensional data array s (m, n) is obtained, where m is the coordinate of the position of the finder, n is the time in one implementation, and the amplitudes of the reflected signal.

After obtaining a similar record of one section of the weld, the boundaries of the region containing the pores are selected as the center of gravity, respectively, of the image obtained for the external and internal surfaces of the product. Then, in this area, a search is made for the maxima of the signal amplitude, and the coordinates of the pores are determined by the coordinates of the center of gravity of the images containing the maxima of the signals, the pore sizes are determined by the sizes of these images.

After deciding on the quality of one section of the weld, the piezoelectric transducer moves along the seam and scans and analyzes the next section of the weld (next control line).

For example, a focused piezoelectric transducer with an operating frequency of f = 30 MHz, a plate diameter of D = 6 mm, and a focal length of Fc = 19 mm is used. The transducer is installed at an angle of 30 °, while in the material of the product (zirconium) the input angle of ultrasonic vibrations α is ~ 49 °, the diameter of the ultrasonic spot in the product is d ~ 0.15 mm. The piezoelectric transducer is installed at the starting point of scanning one section of the weld, then radiation is received, ultrasonic pulses are received and the full realization of the reflected signal is recorded. The implementation contains all the information about the passage of ultrasonic pulses at a given point of scanning (a signal from the outer surface of the product, a signal from the inner surface of the product and signals from inhomogeneities in the weld) (Fig. 1). Then this implementation is converted to digital form and linear smoothing and envelope extraction are performed according to formulas 1-3. The envelope of the implementation is stored together with the position coordinate of the piezoelectric transducer for further construction of the recording of one section of the weld. After this, the piezoelectric transducer moves a predetermined step across the weld and again radiation and reception of ultrasonic pulses occur, the envelope of the implementation is highlighted and stored.

After all points of a given section of the weld are scanned in a similar manner (one control line), a record is created of this section of the weld according to the envelope of the implementation. In this case, an image is obtained (Fig. 2), in which the time samples in each implementation are plotted along the horizontal axis, the position coordinates of the piezoelectric transducer are plotted, and the signal amplitude at each point is represented by the image brightness. Next, the centers of gravity of the images obtained for the outer and inner surfaces of the product are calculated, and the pore region is determined. After that, an analysis of the brightness of the image in the pore region is carried out (search for signal peaks in the pore region) and the centers of gravity of all images containing the maxima are calculated. The coordinates of these centers of gravity are taken as the coordinates of the pores, pore sizes are determined by the size of these images.

Thus, the use of this invention allows to qualitatively identify pores in thin-walled products.

Claims (1)

The method of ultrasonic quality control of welds in thin-walled products, including moving the piezoelectric transducers over the weld with the simultaneous emission and reception of ultrasonic signals, characterized in that the piezoelectric transducer is installed at an angle to the product, at each control point, the complete realization of the reflected ultrasonic signal is recorded, smoothing and selection are performed the envelope of this implementation and after scanning the entire section of the weld, an image of the section is built, the boundaries of the zone on ichiya then calculating the centers of gravity of images external and internal surfaces of the article is searched maximums signal amplitude in this area and coordinates of the center of gravity of the image containing the signal maxima, and determine the coordinates of pore sizes.

Images