SU1046669A1 - Method of measuring mechanical stresses in ferromagnetic articles - Google Patents

Abstract

-one. METHOD FOR MEASUREMENT OF MECHANICAL STRESS IN ferromagnetic articles comprising the article of controlled variable magnetization, a magnetic field parallel to its surface, a periodic change in direction the floor and vschelenie -measurement signal proportional to the magnitude of the envelope of the amplitude-modulated magnetic flux in the article by the sensor, wherein that, with. In order to increase accuracy, the magnitude of the signal proportional to the carrier of the amplitude-modulated magnetic flux in the product is additionally measured and measured, the value of the reference voltage is determined, and the magnitude of the mechanical stresses in the product is determined from the ratio SG-KUC 1). (Г К Oc-magnitude of mechanical loadings, -the coefficient of proportionality; -the increase in the envelope of the signal; the value of the carrier signal, Oo, the magnitude of the reference voltage. 2 .. Method POP.1, differ from ay-g and u with. The fact that the magnitude of the reference voltage is determined from the measurement results of the envelope and carrier signals for two values of the gap between the measuring transducer and the product from the ratio

Description

The invention relates to magnetometry and can be used to control products made of ferromagnetic materials, for example, using patch magnetoelastic converters. There is a known method for measuring mechanical stresses, which includes magnetization of a controlled product parallel to its surface in mutually perpendicular directions and measuring the difference in magnetic fluxes in these directions, according to which mechanical stress is measured. The disadvantage of this method is the dependence of measurement results . from the size of the gap between the surface transducer and the controlled object, which reduces the accuracy of the measurements. . - There is also known a method for measuring mechanical stresses in ferromagnetic products, including magnetization of a controlled product by an alternating magnetic field parallel to its surface, periodically changing the field direction, extraction and measuring the signal proportional to the magnitude of the amplitude modulated magnetic flux in the field, using a measuring transducer, the magnitude of this signal is used to judge the mechanical value. stress 2.. . The disadvantage of this method is also the dependence of the magnitude of the low-frequency signal on the gap between the transducer and the product under test, which reduces the accuracy of the measurement of mechanical stresses. The purpose of the invention is to improve the accuracy of measurement. -. . This goal is achieved by the fact that according to the method, the measurement of mechanical stresses in ferromagnetic products, including the magnetization of a controlled product with a variable field parallel to its surface, is a perydral change in the direction of the field, the selection: e and the measurement of a signal proportional to the envelope magnitude-modulated magnetic flux in the product, an additional and are extracted. The magnitude of the signal proportional to the carrier magnitude of the modulated magnetic flux in the product is measured, the value of the reference voltage is determined, and the value of the mechanical voltage is determined. the stresses in the product are determined from the ratio G - KUn, the proportionality factor f, Uj, is the magnitude of the envelope signal, Ug is the magnitude of the carrier signal; and is the value of the reference ip. In addition, the magnitude of the reference voltage is determined from the results of measuring the envelope and carrier signals at two values of the gap between the measuring transducer and the product from the ratio About nti Tsn-Tsn 1.41 ,, || ,,one . where rc, rc and (Jg, ljl are, respectively, the magnitude of the bend, carrier and carrier signals at two X gap values. Figure 1 shows the time diagrams of the amplitude-modulated output signal of the ACUT measuring transducer, constant voltage (Jg, proportional to the carrier amplitude modulated (AM output signal, and variable (low frequency) voltage -Un proportional to the AM envelope of the output signal for three values of the value of mechanical stresses (Y: (D 0.6-6 and (-Oi ((J -2); on f.2 time diagrams of output U | ibix signal of a constant voltage UQ proportional to the carrier LM of the output signal, alternating (low-frequency) voltage (Jv, proportional envelope AM of the output signal ,, and magnitude (J. at a constant value of mechanical stresses for two the values of the gap and: And A - A, j (u2.ui) The method is carried out as follows: The surface-mounted transducer is installed above the surface of the test item. An alternating current is supplied to the magnetizing winding of the converter and the direction of the magnetization reversal is periodically changed. From the OUTPUT signal of the converter, the low frequency and high frequency signals are extracted and measured. The measurement of low-frequency and high-frequency signals is preliminarily carried out at: two values of the gap between the transducer and the product, and the magnitude of the reference voltage is determined by the formula (.2). Magnitude mechanical ex. for arbitrary size of the gap is determined from the formula (.1). Thus, for example, mechanical stress was measured in a steel sample with three firing values L: o; 0.2 and 0.4 mm. The results of the measurements are presented in Tables 1 and 2. Table 1 shows the results of measuring an alternating voltage, proportional to the low-frequency signal Uy, with a difference between the transducer and the sample,

values of mechanical stresses. The results obtained are presented

for the three values of the gap between prev-in table 2, the developer and the sample,

Table 1

Table 2

From the presented results, one can see that when the clearance is changed from 0 to 0.4 mm, the magnitude of the variable voltage U / V decreases by more than. twice for all mechanical stress values, i.e. There is a significant dependence of U, on the gap between the transducer and the product. Poethoglu, in accordance with the proposed method, measures the values of the constant voltage U-, proportional to the high-frequency signal Up, at different gaps. The following values are obtained for U-: for a gap of O mm 3.92. B, for 0.2 mm 3.5 V and for 0.4 MT / f - 3.2 V. In accordance with formula (2), the magnitude of the reference voltage Uo is determined from the value of m 0, and U- for two values of the gap: Оn 0.4 gdm at the value of mechanical stresses of 60 MP, a. For the magnitude of the reference voltage I get the value of 4.74 in. Taking into account the obtained value of the reference voltage, the measurement results are recalculated in accordance with formula (1), i.e. the values of the ratio of the form of the REL are determined, which is proportional to the ratio of the type 0c. The value of the ratio of pensions (| and) is determined on the magnitude of the mechanical stresses for the three values of the gap The coefficient of proportionality K is determined experimentally and depends both on the material and edel, and on the parameters of the measuring circuit. As follows from the predicted results, the magnitude of the ratio U is proportional to the magnitude of the mechanical stresses. An additional measurement of the constant voltage C, proportional to the value of high. the frequency signal allows to significantly reduce the influence of the gap on the measurement results of mechanical stresses. Thus, the deviation of the value of -fi from the average value when the gap changes from 0 to 0.4 mm does not exceed 5% at all levels of mechanical stresses, which is comparable with the measurement error of the values of the variable Ur and the constant voltage U-. Thus, the application of the proposed method makes it possible to reduce the effect of the gap between the transducer and the product being monitored on the measurement results of mechanical stresses, and thereby increase their accuracy by more than an order of magnitude.

Claims (2)

1. METHOD FOR MEASURING MECHANICAL STRESSES IN FERROMAGNETIC PRODUCTS, including magnetization of the controlled product to variables. a magnetic field parallel to its surface, periodically changing the direction of the field, isolating and measuring a signal proportional to the envelope of the amplitude-modulated magnetic flux in the product using a measuring transducer, characterized in that, p. In order to improve accuracy, they additionally isolate and measure the signal proportional to the carrier of the amplitude-modulated magnetic flux in the product, determine the value of the reference stress, and the value of the mechanical stresses in the product is determined from the relation θ '- the value of mechanical stresses) K is the coefficient of proportionality; value of the envelope of the signal; magnitude la, magnitude of life. The method according to claim 1, with i. The fact that · the magnitude of the reference where θβ of the carrier signal supporting I differentiate-S 2 .. u and th voltage are determined by the results of the measurement of the envelope and insignificant. signal at two values of the gap between the measuring transducer and the product from the ratio; , .1 1,1 '• - ^ϋ ° · ^{υ & υβ} (Ш- (« I Ч ^н Ίβ, in ~ the values ^{of the} envelope and the carrier signal, respectively, for two values of the gap. where U * _h , C *>