RU2088897C1 - Converter for thermal test flaw detector - Google Patents

Abstract

FIELD: nondestructive testing. SUBSTANCE: converter has sensitive unit in the form of matrix made from circular ferrite cores with rectangular hysteresis loop enveloped by winding closed through photo- or thermosensitive element, temperature- sensitive resistor, photodiode, photoresistor or other elements. Sensitive elements are organized into matrix and are integrally made. recording and reading of changes of resistance of sensitive elements is realized by three-coordinate select system. Relief of thermal field or distribution of radiation flow are transformed into visual image on screen of videocontrol device. EFFECT: improved functional reliability. 2 cl 3 dwg

Description

 The invention relates to non-destructive testing and can be used for inspection of metallic and non-metallic products.

A device for thermal non-destructive testing, comprising a receiver of infrared radiation, a scanning device, an electrochemical recording apparatus, which allows to obtain a visual image of the relief of a thermal field [1]
The disadvantage of this device is the presence of a mechanical scanning system, significantly reducing the reliability of the flaw detector.

A device for thermal non-destructive testing, comprising a thermal imager and allowing to obtain an image of the relief of a thermal field directly on a television screen [2]
The disadvantage of this device is the impossibility of contact thermal control and, as a consequence, the impossibility of control in hard-to-reach places.

 Closest to the proposed one is a magnetic field transducer to a flaw detector containing a series-connected matrix of ferrite ring cores with a rectangular hysteresis loop stitched with vertical, horizontal and diagonal address buses, each core having a winding and an element that closes the winding, the output of which is connected to the input of the unit selection, a scan unit, the first output of which is connected to the address buses, the second output is connected to the clock input of the video monitoring device and, a third output connected to a control input of the selection unit [3] Since the ferrite core signal depends on the ambient temperature, the flaw would be used for thermal control, but has low sensitivity, which does not allow it to control non-ferrous products.

 The aim of the invention is to increase the sensitivity of non-destructive contact control of heated products.

 The goal is achieved in that in the converter to a flaw detector containing a series-connected matrix of ferrite ring cores with a rectangular hysteresis loop stitched with vertical, horizontal and diagonal address buses, each core is equipped with a winding and an element that closes the winding, an amplifier, a signal selection unit, a video control a block and a scanner, the first output of which is connected to the address buses, the second output of which is connected to the clock input of the video monitoring device, and the third the output of which is connected to the control input of the selection block, the winding is closed by a photo- or heat-sensitive element.

 A distinctive feature of this invention is that the sensitive node is made of cores with a rectangular hysteresis loop, each of which contains a winding closed through a photosensitive or heat-sensitive element.

 The magnetization reversal of the selected core is performed by current pulses, in the presence of an external magnetic field this leads to a partial magnetization reversal of the core. In this case, the core operates on a linear portion of the hysteresis loop and the residual induction depends on the strength of the external magnetic field. During magnetization reversal, an EMF of electromagnetic induction proportional to the residual core induction is induced in the read winding. The magnitude of the EMF in the read winding also depends on the core temperature.

где Β_(B) температурный коэффициент остаточной индукции.According to the formula

where Β _{(B) is the} temperature coefficient of residual induction.

где R(Φ) динамическое сопротивление сердечника;
F₀ мдс, соответствующая некоторому расчетному полю НО;
i ток записи.The dynamics of the magnetization reversal of the core by current pulses is described by the equation:

where R (Φ) is the dynamic resistance of the core;
F ₀ mds corresponding to some calculated field BUT;
i write current.

и с учетом обратного спада магнитного потока

где R(Φ) и F₀, меняющиеся в широких пределах в зависимости как от состояния сердечника, так и от разброса магнитных параметров различных экземпляров, прямо влияют на точность записи при использовании импульсов тока. При записи импульсами напряжения влияние этих отклонений минимально.After integrating this equation, it turns out

and taking into account the reverse recession of the magnetic flux

where R (Φ) and F ₀ , varying widely depending both on the state of the core and on the spread of the magnetic parameters of various specimens, directly affect the recording accuracy when using current pulses. When recording voltage pulses, the influence of these deviations is minimal.

Recording the residual flux using voltage pulses is the most accurate recording method, since in this case the influence of the spread in the magnetic parameters of the cores can be minimized. If the flux in the core is at some initial level Φ _nach , then the change in flux DF when exposed to a voltage pulse l (t) during time t _app. .

где W_зап число витков обмотки записи;
i ток записи;
r полное сопротивление цепи записи.

where W _{app the} number of turns of the winding record;
i write current;
r impedance of the write circuit.

Погрешности, обусловленные падением напряжения на активном сопротивлении и обратимой составляющей, могут быть значительно снижены.After the end of the pulse, a flow change ΔΦ _arr passes and, therefore, the irreversible component of the flow change is written as follows:

Errors caused by the voltage drop across the active resistance and the reversible component can be significantly reduced.

Учитывая, что l=U-ir
получается

В этой формуле

и R′(Φ)=W $\genfrac{}{}{0ex}{}{\text{2}}{\text{зап}}$ •R(Φ) сопротивление короткозамкнутого витка и динамическое сопротивление, соответственно приведенные к обмотке записи; R_к//R′(Φ) величина сопротивлений при их параллельности включения.However, recording the coincidence of current pulses is extremely convenient for elements organized in a matrix, while each of the currents cannot change the magnetic state of the core. When a short-circuited winding is introduced, covering the core, a recording mode is created that is equivalent to the recording mode by voltage pulses, but the matrix selection method is preserved by matching the coordinate currents. When writing to a separate core, the expression is obtained:

Given that l = U-ir
it turns out

In this formula

and R ′ (Φ) = W $\genfrac{}{}{0ex}{}{\text{2}}{\text{app}}$ • R (Φ) short-circuit resistance and dynamic resistance, respectively reduced to the recording winding; R _to // R ′ (Φ) is the value of the resistances with their parallel inclusion.

Как видно из этого выражения, при постоянстве U и R величина напряжения записи, а значит и остаточная индукция сердечника, зависят только от сопротивления короткозамкнутого витка. Если в цепь короткозамкнутого витка включить фото- или термочувствительный прибор, проводимость которого зависит от интенсивности теплового поля, или потока излучения, то величина напряжения записи l, а следовательно и остаточная индукция сердечника, зависят от интенсивности внешнего теплового поля или потока излучения.Since the power source must be a current generator, the condition U >> l is satisfied, therefore i = U / R. The accuracy of maintaining a write voltage constant with any core parameters R (Φ) and F ₀ is higher, the higher the write current i = U / R of its component F ₀ / W _app and the lower the reduced resistance of the short-circuited loop of the reduced core dynamic resistance R ′ (Φ). In the limit, the relation

As can be seen from this expression, with constant U and R, the magnitude of the write voltage, and hence the residual induction of the core, depends only on the resistance of the short-circuited loop. If a photosensitive or thermosensitive device is included in the circuit of a closed loop, the conductivity of which depends on the intensity of the thermal field or radiation flux, then the value of the recording voltage l, and therefore the residual induction of the core, depend on the intensity of the external thermal field or radiation flux.

 In this case, the core covered by a coil closed through a photosensitive or heat-sensitive element is a converter of the intensity of the thermal field or radiation flux to the level of residual induction, which in turn is converted to the EMF level in the read winding and is characterized by a higher sensitivity and a wide range of perceived thermal fields in comparison with the prototype, as well as sensitivity to the flow of light radiation. Such a relationship of the photo- or thermosensitive element with a ferrite ring core is unknown and is not described in the literature.

позволяет с высокой точностью поддерживать значение l постоянным, однако координатная запись устанавливает жесткие соотношения между U/R и F₀/W_зап. Если обозначить
(i/2)/(F₀/W_зап)=k и i U/R.As noted above, compliance with the conditions U / R >> F ₀ / W _app and

allows you to maintain the value of l constant with high accuracy, but the coordinate record establishes tough relations between U / R and F ₀ / W _app . If designated
(i / 2) / (F ₀ / W _app ) = k and i U / R.

Таким образом, в случае координатной записи приходится считаться с возможными изменениями значения как в процессе записи, так и при переходе от одного экземпляра сердечника к другому. Указанное ограничение легко понять, если учесть, что U/R есть полный ток записи, а F₀/W_зап, то его часть, которая затрачивается на преодоление порога перемагничивания. Естественно, что при координатной записи превышение полного тока над пороговым не может быть большим. Улучшение соотношения может быть получено,

, если воспользоваться не двухкоординатной, а трехкоординатной записью. Третий ток удобно подавать в диагонали матриц. Так как условие записи координатной k<1,2k>1 и соответственно k выбирается обычно в пределах 0,65-0,75, а при трехкоординатной записи остается справедливым k=0,65-0,75, но здесь уже
k=(i/3)/(F₀/W_зап).then

Thus, in the case of coordinate recording, one has to reckon with possible changes in the value both during the recording process and during the transition from one core instance to another. This limitation is easy to understand, given that U / R is the total write current, and F ₀ / W _app , then its part, which is spent on overcoming the magnetization reversal threshold. Naturally, in coordinate recording, the excess of the total current over the threshold cannot be large. An improvement in the ratio can be obtained,

if you use not a two-coordinate, but a three-coordinate record. The third current is conveniently supplied in the diagonal of the matrices. Since the condition for writing the coordinate k <1.2k> 1 and, accordingly, k is usually chosen in the range of 0.65-0.75, and for three-coordinate recording, k = 0.65-0.75 remains valid, but here
k = (i / 3) / (F ₀ / W _app ).

, выражение величины напряжения для двух- и трехкоординатной записи соответственно примет вид:

Из этих выражений следует, что при координатной записи изменять приложенное напряжение l можно, меняя лишь сопротивление

, причем в отличие от записи в отдельный элемент этого нельзя сделать, меняя U или R. Величина сопротивления

определяется проводимостью фото- или термочувствительного элемента и зависит от интенсивности внешнего теплового поля или потока излучения. Таким образом, включение в цепь короткозамкнутой обмотки фото- или термочувствительного элемента придает аналоговому матричному устройству новое свойство возможность преобразования неоднородности теплового поля на поверхности объекта контроля или интенсивности потока излучения в соответствующие уровни остаточной индукции сердечников, которые при опросе сердечников матрицы преобразуются в соответствующие значения ЭДС в обмотке считывания.Further, in the same manner as above, it turns out
U / R = 3k (F ₀ / W _zap ) (1.95-2.25) • (F ₀ / W _zap )
The improvement in the ratio between U / R and F ₀ / W _app occurred due to the large excess of the total recording current over the threshold when using three coordinates instead of two. Since for coordinate recording, the condition

, the expression of the magnitude of the voltage for two- and three-coordinate recording, respectively, will take the form:

From these expressions it follows that with coordinate recording, the applied voltage l can be changed by changing only the resistance

, and in contrast to writing to a separate element, this cannot be done by changing U or R. The resistance value

it is determined by the conductivity of the photo- or thermosensitive element and depends on the intensity of the external thermal field or radiation flux. Thus, the inclusion of a photosensitive or heat-sensitive element in the short-circuited winding circuit gives the analog matrix device a new property: the ability to convert the inhomogeneity of the thermal field on the surface of the test object or the intensity of the radiation flux into the corresponding levels of residual induction of the cores, which, upon interrogation of the cores of the matrix, are converted to the corresponding EMF values in read winding.

 The presence of each ring core with a rectangular hysteresis loop of a winding closed through a corresponding photosensitive or thermosensitive element, a thermistor, a photoresistor, a photodiode, or others gives the converter a new quality, the ability to detect inhomogeneity of the thermal field or radiation flux, which could not be carried out by an analog converter. These qualities are provided by increasing the sensitivity and ability to perceive the intensity of the heat or light flux. All this is manifested in the ability to control products of complex shape in hard-to-reach places and to obtain an image of the relief of a thermal field or radiation flux directly on a television screen, which is a significant difference and can be recognized by the invention.

 Figure 1 presents a block diagram of a thermal field transducer, which shows the source of the thermal field 1, the object of control 2, the matrix sensitive node 3, amplifier 4, the amplitude and time selection block 5, the video control unit 6 and the scan unit 7.

 In FIG. 2 is a diagram explaining the principle of organizing a photosensitive assembly, which shows a ferrite core 8, a winding 9, a photosensitive element 10, vertical coordinate buses 11, horizontal coordinate buses 12, diagonal coordinate buses 13.

 Figure 3 shows the arrangement of the matrix of ferrite cores and the matrix of photosensitive elements, here are shown the matrix of cores 14, the matrix of photosensitive elements 15 and the interface zone of the matrices 16.

 The magnetically sensitive transducer assembly is an M + N matrix of ferrite ring cores with a rectangular hysteresis loop, where M is the number of elements in a row, N in a matrix column. Each core is covered by a winding closed through a photosensitive or thermosensitive element - a thermistor, a photoresistor, a photodiode, or other photosensitive elements, which can be made in the form of a matrix in the integral design, which ensures a minimum variation in parameters and a high packing density of elements. The matrix of cores 14 forms a second matrix and is located above the matrix 15 of magnetically sensitive elements and its dimensions can be much larger than the matrix of magnetically sensitive elements, since this does not affect the resolution.

 The connection between the matrices is carried out through the interface zone 16, while the ends of the windings are directly connected to the terminals of the sensitive elements or the communication is carried out by an intra-complex interface, which is widely used in microprocessor technology. The entire magnetically sensitive assembly is filled with transparent polyurethane or special rubber, which ensures sealing and mechanical strength.

 Ferrite cores are pierced by three coordinate buses 11, 12, 13 and a read winding, which, in order not to obscure the drawing, is not shown in FIG. 2. The read winding penetrates half of the windings of each row and each column of the matrix in one direction, and the second half in the opposite, this firmware allows you to compensate for interference from the cores through which the current flows only one coordinate 5.

 The read winding is connected to the input of the differential amplifier4, since the signal at the output of the matrix is bipolar in accordance with the firmware of the read winding. The amplitude selector 5 is designed to highlight the signal against the background of interference.

 The scan unit 7 is designed to generate control pulses supplied to the coordinate buses of the matrix, to the control input of the video control unit 6 and to the second input of the amplitude and time selection unit 5.

 The converter operates as follows.

 The source of the thermal field 1 heats the control object 2, at the locations of the defects a heterogeneity of the thermal field occurs, which acts on the matrix photosensitive or heat-sensitive element 3 and changes the conductivity of the photosensitive or heat-sensitive elements 10. Switching the cores by current pulses leads to residual induction strongly depends on the scatter of the parameters of the cores themselves, the presence of a short-circuited winding 9 allows the core to be switched by voltage pulses, while the residual induction It depends only on the short-circuited winding resistance, and inclusion in the short circuit coil or photo- sensing element 10 provides the dependence of the remanence flux intensity or field relief heat.

 When the current pulses supplied by the scan unit 7 to the coordinate buses 11, 12, 13 coincide, the core switches from one state of remanent magnetization to another. In this case, an EMF of electromagnetic induction is induced in the read winding. The amplitude of the pulses is determined by the value of the residual induction, and hence the intensity of the defect scattering field.

 The scanner 7 alternately magnetizes the cores 8 line by line. The output signal of the photosensitive node 3 is fed to the input of a differential amplifier 4, which can amplify the voltage of both polarities, then the signal is transmitted through the amplitude time selection block 5, in which all are cut off at the selected level in amplitude and the useful signal is separated from interference that does not coincide in time with a useful signal, enters the video control unit 6. Temporary selection is made by gating pulses supplied to the second input of the selection block 5 from the second output of the scanner.

 The signals from the third output of the scanner 7 provide the movement of the beam on the screen of the video control unit 6 in synchronization with the polling of the elements of the photosensitive unit 3. The signal supplied to the first input of the video control unit modulates the brightness of the light spot on the screen, resulting in a visual image corresponding to the relief of the thermal field on surface of the control object or radiation flux intensity.

 The use of a three-coordinate interrogation system provides a total error of not more than 1%. The scan unit generates pulses, with a frequency of interrogation of the matrix elements necessary for temporary selection, it has three decoders whose outputs are connected to the corresponding coordinate bus systems - vertical, horizontal and diagonal. The diagonal coordinate is aligned with vertical and horizontal. For example, to select the first matrix element, row 1, column 1, diagonal 4 are selected.

 The application of the proposed thermal field transducer to the flaw detector will allow, in comparison with the prototype, to control metallic and non-metallic products, to obtain a visual image of the relief of the thermal field or the intensity of the radiation flux.

Claims (2)

 1. The transmitter to the flaw detector for thermal control, containing a series-connected matrix of ferrite ring cores with a rectangular hysteresis loop, stitched with vertical, horizontal and diagonal address buses, each core is equipped with a winding and an element that closes the winding, amplifier, signal selection unit, video control unit and a scanner, the first output of which is connected to the address buses, the second output of which is connected to the sync input of the video monitoring device, and the third you the course of which is connected to the control input of the selection block, characterized in that, in order to increase the sensitivity of non-destructive contact control of heated products, the winding is closed by a photo- or heat-sensitive element.  2. The Converter according to claim 1, characterized in that the element closing the winding is made in the form of photoresistors or a photodiode.

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