CS256183B1 - Method of ferromagnetic materials' stresses measuring and device for realization of this method - Google Patents

Abstract

Contactless measurement methods of ferromagnetic materials uses magnetoelastic phenomenon while determining the ratio total permeabilft of measured material pFi two different intensity values exciting magnetic pole. solution concerns the issue of contactless measurement the tension of the ferromagnetic material, forces acting on ferromagnetic material and the moment of force acting on the ferromagnetic material. Device and method of measurement of ferromagnetic materials can be used for pressure and tensile measurements forces, moment of force, torque, positioning and steel cover reinforcements in non-ferromagnetic materials searching for inhomogeneities, internal stresses, and cracks in ferromagnetic materials a monitoring of steel constriction dynamics.

Description

The invention provides a method for measuring the state of stress of ferromagnetic materials and an apparatus for carrying out this method.

The problem of noncontact measurement of structural steels is not yet satisfactorily solved. Most of the known methods use sensors which must be in direct contact with the measured element. In the case of ferromagnetic materials, it is possible to utilize a change in their magnetic properties under mechanical stress. On this principle are based sensors using magnetoelastic, magnetoanisotropic and inverse Wiedemann effect. All the above-mentioned types of sensors have their own magnetic circuit, made of a special alloy and are contact, i. j. they must be a mechanical part of the measured element. The measured material itself has been used as a ferromagnetic core of the sensor so far in only one case in the construction of a dynamometer designed for measuring tensile forces in steel wires and ropes. The actual sensor, consisting of the excitation and sensing coils, is freely slid onto the measured element, with which it is not in contact at all. The dynamometer measures the absolute change in the reversible permeability of the measured wire or rope, which is proportional to the applied force. The disadvantage of this method, apart from the necessity to use a large excitation power, is to measure the corresponding calibration curve which, together with the known material temperature, for each measured element beforehand, either under laboratory conditions or in the tensioning process. evaluation of all other stress measurements of this element.

The above-mentioned drawbacks are eliminated by the invention, which is based on the fact that the measurement is carried out non-contact by means of a magnetic pole, which is created around the measured element by an excitation current I1 and the corresponding output voltage Ui is measured. by changing the intensity of the excitation current to a value of intensity h, the corresponding value of the output voltage U2 is measured, finally the output voltage ratio is determined and its magnitude and the magneto-elastic characteristic of the same type of material are determined. The magneto-elastic characteristic is determined in the laboratory conditions by determining the dependence of the corresponding value of the output pumped element, the magnitude of the force applied to the applied force or the moment of force, whereby the ratio U1 and U2 is the field current by the field current with the intensity l1 and from the measured element creates a magnetic ria with the corresponding value of the output net field by changing the field current intensity to the value of I2 and measure the voltage U2, then change the magnitude and magnitude of the moment of the type of material by gradually increasing the pH after the addition of the material to the measured element.

The apparatus for implementing the described method comprises a sensor consisting of an excitation solenoid and a sensing coil with a parallel connected resistor, wherein the exciting solenoid is connected to a power source and a sensing coil to an integrator input whose output is connected to inputs of two sampling amplifiers. the inputs of the differential amplifier, the output of which is coupled to the input of another sampling amplifier, the output of which is connected to a voltmeter.

Said method for measuring the state of stress of ferromagnetic materials and the apparatus for carrying it out have the advantage that, by using a low and constant rate of magnetization of the measured material, losses for its heating by eddy currents are avoided. The use of a pulse source and a triangular excitation current waveform will substantially reduce the dissipated power and reduce the required excitation power to one third of the method used hitherto. Determining the ratio of the corresponding output voltages at two different excitation current values makes it possible to determine the magnitude of the measured element according to the average magnetoelastic characteristic of the material without having to pre-measure a particular sample of the measured element. . o prestressed concrete rope. The temperature compensation of the sensor eliminates the zero point shift of the magnetoelastic characteristic when the temperature of the measured element changes. With the same device and sensors it is possible to measure contact and tensile forces, moment of force, position and cover of reinforcement, to find inhomogeneities, internal stresses and cracks in ferromagnetic materials and to monitor the dynamics of ferromagnetic elements stress.

The method and apparatus according to the invention can be used, in particular, in determining the stresses of ferromagnetic construction materials and in tests in construction and mechanical engineering in particular.

The figure shows a diagram of a device for measuring the stress of ferromagnetic materials.

The apparatus for measuring the state of ferromagnetic materials comprises a sensor 1 consisting of an excitation solenoid 2 and a sensing coil 3 with a parallel resistor 4, wherein the excitation solenoid 2 is connected to a current source 5 and a sensing coil 3 to an integrator 6 input. the outputs of which are connected to the inputs of the differential amplifier 9, the output of which is connected to the input of the sampling amplifier 10, its output voltage being measured by a voltmeter 11.

The excitation solenoid 2 of the beverage per current source 5 creates a magnetic field with intensity H (t) in the vicinity of the sample to be measured. A voltage proportional to the time derivative of the magnetic flux ácii (ί) across the sensor coil surface is induced in the sensor coil 3. At the output of the integrator 6, a voltage proportional to the instantaneous value of the magnetic induction B (t) in the measured pattern is obtained. The sampling amplifiers 7 and 8 memorize the maximum and minimum values of the magnetic induction and the differential amplifier 9 makes a difference, proportional to the total permeability of the sample to be measured, which is rewritten into the sampling amplifier 10 and measured with a voltmeter 11. and sensor.

β

Example:

Sample: pre-tensioned rope L _p 15.5 / / 1620 MPa

S == 141.5 raiu ²

Measuring sensor: cylindrical, inside diameter

17 mm

Excitation currents: Ji = 1.25 A, Jz = 1.75 A Measuring procedure:

The sample of the cable with the sensor was clamped in the measuring press with an accuracy reading of 1%. The force was gradually increased until the sample was torn. At the selected force values, the output voltages of the instrument U1 and U2 were read (Table 1 and the ratio Uz / Ui - 1 was determined). The calibration curve obtained is thus applied to the attached diagram, where T is the stress.

100 * <U2 / U1-1>

σι Ο) Μ 00 00 (Ο Η * Ο ο 1 → Η * ►— · ΓΌ • • • • • » • • • « (Ο σι > - * <1 ω <ο σι »-Λ J ω (Ο σι (Ο (Ο it (Ο (Ο (Ο it (Ο (Ο CD (Ο (Ο

Τ / ΜΡα /

00:00

100. 00

200. 00

300. 00

400. 00

500.00

500. 00

700. 00

800. 00

900. 00

100000

1100. 00

1200. 00

1300. 00

1400. 00

1500. 00

1600. 00

Magneto-elastic characteristics of the rope Lp 15.5 / 1 620 MPa

FpkN) T (MPa) U2 (A) Ui (A) U2 / U1-1 0.00 0.00 9.9450 9.3830 0.05990 25.00 176.68 9.8100 9.2100 0.06515 30.00 212.01 9.7800 9.1730 0.06617 40.00 282.69 9.7180 9.0960 0.06838 50.00 353,36 9.6540 9.0150 0.07088 60.00 424.03 9.5860 8.9310 0.07334 70.00 494.70 9,5160 8.8450 * 0.0758 * 6 80.00 565.37 9.4430 8.7580 0.07821 90.00 636.04 9.3710 8.6700 0.08085 100.00 706.71 9.2930 8.5730 0.08398 110.00 777.39 9.2160 8.4830 0.08641 120.00 848.06 9.1390 8.3860 0.08979 130.00 918.73 9.0590 8.2930 0.09237 140.00 989.40 8,981 * 0 8.2020 0.09498 150.00 1,060.07 8.8990 8.1010 0.09851 160.00 1,130.74 8.8190 8.0040 * 0,101 * 82 170.00 1 201,41 8.7370 7.9050 * 0.10525 180.00 1,272.08 8.6560 7.8120 0.10804 190.00 1 342,76 8.5800 7.7200 0.11140 200.00 1,413.43 8.5040 7.6350 0.11382 202.00 1 427,56 8.4950 7.6200 0.11483 204.00 1,441.70 8.4830 7.6070 0.11516 206.00 1 455,83 8.4710 7.5880 0.11637 208.00 1 469,96 8.4580 7.5740 0.11672 210.00 1,484.10 8.4470 7.5630 0.11688 212.00 1 498.23 8.4330 7.5430 0.11799 214.00 1,512.37 8.4150 7.5200 0.11902 216.00 1,526.50 8.3930 7.4920 * 0.12026 218.00 1,540.64 8.3650 7.4620 * 0.121 * 01 220.00 1,554.77 8.3360 7.4250 * 0.12269 222.00 1 568.90 8.3080 7.3960! 0.12331 224.00 1,583.04 8.2830 7.3680 0.12419 226.00 1,597.17 8.2600 7.3420 0.12503 228.00 1 611.31 8.2360 7.3170 0.12560 230.00 1,625.44 8.2150 7.2960 0.12596 232.00 11,639.58 8.1930 7.2740 0.12634 234.00 1,653.71 8.1700 7.2480 0.12721

R-Ttfji -; J ''. , β τ »

Claims (3)

SUBJECT A method for measuring the state of stress of ferromagnetic materials, characterized in that the measurement is carried out contactlessly by means of a magnetic field which is generated in the vicinity of the measured element by an excitation current l i and the corresponding value of the first output deposition Ui is measured. by varying the excitation current intensity to a value of I2 and measuring the corresponding value of the second output voltage Už, the output voltage ratio and the magneto-elastic characteristic of the same type of material determines the magnitude of the measured element's stress, the force acting on the measured element and the torque per measured element. 2. Method according to claim 1, characterized in that the magnetoelastic characteristic is determined by determining the ratio of the output stresses to the stresses of the material to be measured by gradually increasing the stresses. BACKGROUND OF THE INVENTION of the material to be measured by gradually increasing the stress of the test element by increasing the shear force and the moment of force, wherein at each selected stress value a magnetic field is generated in the vicinity of the measured element. and the corresponding value of the second output voltage Uz2 is measured and the dependence of the ratio of the output voltages U1 and U2 is determined by the magnitude of the stress of the measured element, the magnitude of the force absorbed by the measured element and the magnitude of the moment element. Device according to claim 1 or 2, characterized in that the sensor (1) is formed by an excitation solenoid (2) and a sensing coil (3) with a parallel resistor (4) connected to the resistor (4), where the excitation solenoid (2) is connected. to a current source (5) and a sensing and coil (3) to an integrator (6) input whose output is connected to the inputs of the sampling amplifiers (7, 8), their outputs being connected to the inputs of the differential amplifier (9) it is connected to the input of a sample amplifier (10), the output of which is connected to a voltmeter (11).