SU1668854A1 - Non-magnetic material article thickness measuring method - Google Patents

Abstract

The invention relates to a measurement technique and can be used to measure the thickness of products or walls of products made from non-magnetic materials, including polymers and composites based on them. The purpose of the invention is to improve the measurement accuracy. According to the proposed method, an electromagnet and an oscillating ferromagnetic body are installed on opposite sides of the monitored product and the frequency of its resonance is determined. Preliminary measurements are made of the resonance frequency of a ferromagnetic body without affecting the magnetic field, and judging by the difference in resonance frequencies, the thickness of the product is judged. 1 hp ff, 2 ill.

Description

The invention relates to a measuring technique and can be used to measure the wall thickness of products and parts made of non-magnetic materials, including polymers and composites based on them.

The purpose of the invention is to improve the measurement accuracy and expand the thickness measurement range. °

FIG. 1 shows a diagram of an apparatus for implementing the method; in FIG. 2 - dependence of thickness variation on resonance frequency.

On the outer wall of the product 1 in the place of measurements there is a measuring unit containing a ferromagnetic body in the form of an elastic rod 2 with a spherical tip 3.

The elastic rod 2 is rigidly fixed at the point of suspension in the housing 4. The measuring unit also has two driver coils 5 connected to the generator 6. In addition, the sensor 2 attached to the oscilloscope 8 is fixed to the rod 2.

An electromagnet 9 with a grounded magnetic conductor is placed close to the product wall.

The method is carried out as follows.

Prior to placing the measuring unit Near the product wall, the resonance frequency of the ferromagnetic body is experimentally determined. For this, the oscillation frequency is selected by the oscillator 6, so that on the oscilloscope 8 screen the oscillation amplitude of the ferromagnetic tip 3, sensed by the sensor 7, is maximum. In this case, for each construction of the measuring unit that implements the method, the frequency of free resonant oscillations is constant and practically does not depend on external conditions:

Yo

Ov

Os 00 00

ate

N

.

where fpea frequency of the resonant oscillations of the system;

k is the rigidity of the oscillatory system;

m is the mass of the oscillating body.

Next, the measuring unit is brought to the outer wall of the product in such a way that between them there is some air gap 6 allowing the ferromagnetic spherical tip 3 to freely oscillate.

An electromagnet 9 is placed on the opposite side of the product and a direct current is applied to its winding. As a result, a magnetic flux occurs, which changes the oscillation frequency of the ferromagnetic core 3. The resonance frequency of the ferromagnetic tip 3 is again determined under the conditions of the magnetic field generated by the electromagnet 9. The difference between the resonant oscillation frequencies of the ferromagnetic tip 3 before and after - according to the calibration dependence, the electromagnet 9 determines the thickness L.

The thickness L consists of g - the wall thickness of the product id - the air gap, which is constant for each design that implements the method. Thus, (5

It is also possible to estimate the measured wall thickness of a material from the change in the amplitude of oscillations A of a ferromagnetic tip at resonance at a fixed frequency.

To extend the measurement range, the magnitude of the magnetic field generated by the electromagnet is changed.

Claims (2)

1. A method of measuring the thickness of articles made of non-magnetic materials, which consists in placing a DC electromagnet and a ferromagnetic body on opposite sides of a product under test, exerts a constant magnetic field on the ferromagnetic body and, based on the results of this action, the thickness of the product differing from By the fact that, in order to increase the measurement accuracy, the ferromagnetic body is made in the form of an elastic rod with a spherical tip, oscillations are assigned to it and their resonance frequency is first determined and in the absence of a magnetic field, then with its effect and the difference in resonant frequencies, the thickness of the product is judged. 2. A method according to claim 1, distinguished by the fact that, in order to expand the measurement range, the magnitude of the magnetic field generated by the electromagnet is changed. eight 7 6 5 4 3 2 1 fab 90 M f2 "J M US tf" 7 Rig. 2