SU123744A1 - Method and device for measuring hardness - Google Patents

Description

Methods for measuring the hardness in which scratches are applied to the surface of the test sample by means of an indenter are known.

A feature of the proposed method is that the hardness is determined by the amount of force required to apply a scratch, a known and constant depth to the sample. When such a scratch is applied, a constant speed of movement of the indenter is maintained. By this method, it is not necessary to measure the size of the scratch.

In a device designed to carry out this method, an indenter mounted near the tip and a mechanically associated stop are applied. The latter, made mobile in height, rests on the surface of the sample and limits the depth of the tip of the indenter.

Such an embodiment of the device maintains a constant depth of the indenter in the sample surface.

The device uses a hydraulic mechanism that ensures uniform movement of the stage with the indenter. In addition, it is equipped with an electric differential capacitive sensor. The movable electrode of this sensor is a flat spring with an indenter attached to it.

The drawing shows a block diagram of the proposed device.

The physical meaning of the described method of measuring hardness lies in the fact that the hardness value is the amount of work of the scratch force per unit volume described by the submerged part of the indenter:

s LР1Р, о

H - r - h - h MM -,

where: H is the hardness value, 1 is the scratch length in mm, P is the scratch force in g, is the area of the projection of the indenter on the surface, perpenVV 1yu

No. 123744-2 -

dicular to scratch, L is the work of force P in section 1, V is the volume described by the submerged part of the indenter in mm.

When carrying out the proposed method, an emphasis 3 and an indenter 4 are supplied with a microscope-interferometer 2 to the surface of the test sample mounted on the object slide 1. The sample is illuminated by the illuminator 5. Then the stop 3 with the indenter 4 is lowered by means of an eccentric elevator 6 onto the sample surface. By means of the screw pair 7, the stop is moved relative to the indenter so that the required depth of its immersion is ensured. The control of the latter is carried out by scratching the reference sample and measuring by means of an optical micrometer and an interferometer.

Thereafter, the table / s is moved to the left by means of the hydraulic mechanism 8 and the scratching is performed.

The plate 9 bends in proportion to the tangential forces of the scratch, changing the gaps of the capacitor of the differential capacitive sensor connected to the circuit of the measuring bridge, fed from the transformer TR, installed at the output of the repeater-generator 10 of the audio frequency. The signals from the bridge diagonal are amplified by the amplifier // and the indicator 12 and the oscilloscope 13 are supplied.

In this way, scratch forces of a very small size (on the order of one milligram) can be measured, and, therefore, the indenter can be omitted by a very small amount. Charging (lifting the working load 14} of the hydraulic mechanism I, designed to evenly move the table /, can be carried out manually or by means of an electric drive 15 with a gearbox 16. During the scratching process, when the subject table / moves, the spring plate 9 of the sensor bends accordingly the tangential force The scratched ratio of the sensor capacitances disrupts the balancing of the bridge. Accordingly, the indicator arrow 12 or the oscilloscope bar 13 is deflected. The main part of the meter hydrochloric circuit devices are shoulders Z, Z-2/3 and Z izmeritelpogo bridge. Sootnoschenie shoulder varies according to the change of the tangential force scarring.

The number 17 in the diagram indicates the power supply unit, which is produced from the lighting network through a stabilized rectifier, and the number 18 denotes the automatic control unit for the electric drive and sigilization.

Subject invention

; 1. A method for measuring hardness based on the principle of applying scratches on the surfaces of a test specimen using an indenter, characterized in that the hardness is determined by the amount of force required to apply a known and constant depth of scratches on the sample while maintaining a constant speed of movement of the indenter.

2. A device for desensitization of a method according to claim 1, characterized in that, in order to maintain a constant depth of the indenter into the sample surface, a mobile stop mounted along the tip of the indenter and mechanically connected with it is used, and limiting the immersion depth of the indenter.

3. In the device according to claim 2, use a hydraulic mechanism to ensure uniform movement of the stage of the device with the indenter fixed on it.

4. In the device according to claim 1, the use of an electric differential capacitive sensor, the moving spring of which is a flat spring with a fixed indenter.