SU1573415A1 - Method of eddy-current inspection - Google Patents

Abstract

The invention relates to non-destructive testing and can be used to determine the surface quality of electrically conductive products. An increase in the confidence of the control is achieved by suppressing the influence of the interfering factor on the result of the control. Preliminary, using control samples, the lines of the influence of the interfering factor in the coordinates are obtained; the resonant frequency F is the maximum amplitude of the U _M signal. Then, the intersection point K of the straight lines P1, P2, P3 of the approximating lines of the influence of the interfering parameter is determined. The eddy current transducer included in the oscillator circuit of the oscillator is installed on the surface of the tested product, the parameters F and U _M are determined, the differences FF _* 00K and U _M are calculated - U _{M *} 00K, where F _* 00K and U _{M *} 00K are the coordinates of K. In relation to the differences obtained, a controlled parameter of the product is judged. 3 il.

Description

The code of the signal DSL, A Figure 3

And chafing refers to unscheduled. - to a new one, and it can be used to divide the quality of the surface of the TPR;

The purpose of the invention is to increase the reliability of KOPT1-MS, which is achieved by suppressing the leading factor of the pe-result control.

FIG. 1 shows the structure of the device for implementing the eddy current testing method; in fig. 2 shows voltage diagrams explaining the operation algorithm of the device; in fig. 3 - dependencies explaining the essence of the eddy current testing method.

An apparatus for carrying out the method comprises a hollow metal case 1 located therein and connected to a sequentially controlled high-frequency generator 2, an attenuator 3 and a detector 4 connected in parallel to an oscillating circuit 5, made in the form of a coaxial line segment and inductance coil (not shown) and a negative active resistance circuit 6 is connected between the common wire and the detector 4 input. Between the detector 4 output and the controlled input of the high-frequency generator 2 are connected in series Inonii analog-to-digital converter (ASCHT) 7, a microcomputer 8 and the digital-to-analog converter (LDA) 9 connected to the output control input of the generator 2. The micro-computer 8 includes a display 10.

The method is carried out as follows.

High-frequency generator 2 generates electromagnetic oscillations in the high-frequency region (0.03-1.5 GHz). The frequency of oscillations of the generator 2 may vary depending on the signal at its controllable input. The oscillations from the output of the high-frequency generator 2 through the attenuator 3 are fed to the inputs of the detector 4 and the oscillating circuit 5, associated with the negative resistance circuit 6, playing the role of the multiplier of the oscillating circuit 5. The magnitude of the signal on the oscillating circuit 5 depends on its quality factor and the degree of frequency detuning of the oscillator 2 and the oscillating circuit 5, varies depending on the signal at the controlled input of the oscillator 2 high

frequencies and is rectified by the detector 4, the A / D converter 7 converts the signal from the output of the detector 4 into a digital code and enters it into the operational memory of the microcomputer 8 for further processing. The eddy current transducer is connected to a parallel oscillating circuit 5, excited by a high-frequency current from generator 2, compensates for the own active resistance of the circuit and the active resistance of the eddy current transducer using a negative resistance circuit 6 and measures the signal at the output of the oscillating circuit 5 with a detector 4 and ADC 7.

The procedure for implementing the method is determined by the microcomputer operating program 8. In FIG. Figure 2 shows the time diagram of the operation of the microcomputer, the change in the signal from the NAL output, according to which the frequency of the excitation current changes, and the change in the signal from the output of the detector 4. At the time t, the frequency of the device generator 2 is reset to the left slope oscillatory circuit. This state corresponds to the signal A, ADC 7 and the signal U (detector 4. At time t. Microcomputer 8 generates the initial value of the digital code of the discrete sequence and outputs this code to the DAC 9. This state corresponds to the signal A2 of the DAC 9. According to the given code changes the frequency of the high-frequency generator 2, -a signal of the detector 4 takes the value U2. At time t3, the signal from the detector 4 is input to the ADC 7, converted into a digital code and entered into the microcomputer memory 8. At the time t4, a comparison of the entered sig occurs U2 with the previously entered signal code U,. If the numeric value of the new code is greater than the previous one, the microcomputer generates the next value of the digital code of the discrete sequence for input into the DAC 9. Processes that occur at times t4, t ,, t4, repeat If the new code of the signal U4 from the output of the detector 4 becomes less than the previous code, this is a sign that a resonance is reached. At the next time instant t

G,

micro-CFM 8 -1POMSH1 a previous signal amplitude code „and the corresponding frequency code А„ ,, calculates a monitored surface quality parameter from a previously established functional relationship using the resonant frequency f found in digital codes and the maximum signal amplitude U.

The required functional dependencies are obtained as follows. The eddy current transducer is installed on the surface of the control sample with a known value of the monitored parameter. The suppressed parameter is changed, the values of digital codes characterizing the maximum amplitude U m of the signal and the resonant frequency f of the oscillating circuit 5 are determined for different values of the suppressed parameter. In the orthogonal coordinate system composed of the indicated digital codes, the influence lines of the suppressed parameter for products with different value of the controlled parameter within the specified limits. The line segments of the effect of the suppressed parameter are approximated by straight lines and the point K of their intersection is found. Coordinates f K and itk intersection points are found and memorized. Regarding the coordinates of the intersection point, the increments of the corresponding digital codes are found, and the functional dependence for calculating the control parameter is set as a load of the digital code increment max. Of the amplitude of the signal on the oscillatory circuit to the increment of the corresponding digital code of the discrete sequence characterizing the resonant frequency .

The implementation of the method in relation to the solution of the problem of suppressing the influence of the gap h between the eddy current transducer and the controlled product when measuring the thickness of the vacuum-plasma

a ferromagnetic base coating is indicated on the fn.W. Here, P, P ,,, - are the influence lines of the change in the generalized gap parameter Ј 2h / D, D is the diameter of the transducer within 0-0.25 for coating thicknesses of 3.2, 5.1 and 8.1 µm, respectively; K - the point of intersection of the lines of influence of the gap.

As follows from the consideration of FIG. 3, the measured value of the coating thickness is defined as the tangent of the angle about and practically does not depend on the change y in the range of 0-0.2.

Claims (1)

Invention Formula The eddy current control method, which consists in including an eddy current transducer into a parallel oscillatory circuit and excites it with a current monotonically varying in frequency, compensates for its own active resistance of the circuit and The impedance introduced into the eddy current transducer records the amplitude-frequency characteristics of the oscillating circuit and determines the resonant frequency and the second informative parameter at the time of resonance, characterized in that, in order to increase the reliability of the control, the second informative parameter is chosen as the maximum signal amplitude obtained on the contour at the moment of resonance, using the control samples, the dependences in the coordinates of the resonance frequency - „are maximum am The signal plots U, at constant values of the measured parameter of the control object and a variable interfering parameter, determine the point K of the influence lines of the interfering parameter with the coordinates fK, U MK, get for the controlled object the differences of the values f-fK and UMK-UM and relation is judged on the controlled parameter of the control object. Sensor signal