SU785643A1 - Apparatus for measuring mechanical stress in ferro-magnetic-material objects - Google Patents

Description

The invention relates to devices for non-destructive testing of objects made of ferromagnetic materials and can be used to measure mechanical stresses in 5 elements of machines and structures.

A device for measuring mechanical stresses is known, using an eddy current transducer extended 1Q in the direction of one axis of the coil and included in the bridge measurement circuit [1].

The magnetic flux emitted by the transducer closes through the air, 15 which does not allow creating a sufficiently strong magnetic field, which explains the low sensitivity of devices using transducers of this type. 20

Closest to the invention is a device for measuring mechanical stresses in objects made of ferromagnetic materials, containing an eddy current transducer 25: in the form of a coil with a ferromagnetic core extended in the direction of the same axis and a mechanical stress measuring unit, the output of which is connected to a frequency meter [2]. thirty

However, due to the inconsistency of the gap between the core and the surface of the control object, the measurement results are accompanied by significant errors.

The aim of the invention is to improve the accuracy and sensitivity of measurements of mechanical stresses.

This goal is achieved by the fact that the device is equipped with an additional coil located on the core of the transducer, and a unit for setting the calibration value, magnetic resistance of the air gap between the core of the transducer and the surface of the control object, made in the form of an oscillator with a phase-shifting frequency-dependent feedback circuit, in the circuit of which an additional inductance coil, and the unit for measuring mechanical stresses is made in the form of a self-oscillator, in a setting oscillatory to ntur which included pickup coil.

In FIG. 1 shows the proposed device, a General view; figure 2 is the same, a schematic diagram.

The device contains a converter 1, which is a 'Ш-о <·' * different ferrite core with the measuring and additional coils 2 and 3 located on the middle core of the core in the direction of the same axis, block 4 for setting the calibration value of the magnetic resistance of the gap, including an oscillator 5, in the parallel oscillatory circuit of which is included a coil 3, amplifiers 6 and 7 and a phase-forming frequency-dependent feedback circuit 8, a unit 9 for measuring the magnitude of mechanical stresses, including a second circuit generator in which the oscillation circuit included measuring frequency coil 2 and 10.

The frequency-dependent feedback circuit 8 provides, in a certain range of changes in the magnetic resistance of the air gap, the operation of the self-oscillator 5 at a frequency higher than the resonant frequency of the oscillatory circuit of this generator, which allows you to tune out from the influence of the electrical and magnetic properties of the control object 11 when setting the air gap at which the device was calibrated .

The magnetic resistance of the gap at which the device was calibrated corresponds to a certain frequency f of the unit .4 installation. By adjusting the position of the transducer 1 relative to the surface to be monitored, the frequency of the unit 4 is set equal to £. After establishing the required clearance, the device is switched to the measurement of mechanical stress.

The frequency of operation of the measuring unit 9, in the oscillatory circuit of which the measuring coil 2 is re-extended

$ 1 braveovatel, determined by the parameters of the measuring coil, depending on the electrical and magnetic properties of the test object, determined by mechanical stresses.

The measurement result is recorded by the frequency meter.

Claims (1)

Claim A device for measuring mechanical stresses in objects made of ferromagnetic materials, containing an eddy current transducer in the form of a coil with a ferromagnetic core extended in the direction of one axis and a unit for measuring mechanical stresses, the output of which is connected to a frequency meter, characterized in that, in order to increase the measurement accuracy and sensitivity of the device it. equipped with an additional coil located on the transducer core and a unit for setting the calibration value of the magnetic resistance of the air gap between the transducer core and the surface of the control object, made _x in the form of a self-oscillator with a phase-shifting frequency-dependent feedback circuit, in the circuit of which an additional inductor is included, and the unit for measuring mechanical stresses is made in the form of a self-oscillator, in the master oscillatory circuit of which a measuring coil is included ka.