SU914980A1 - Optical dilatometer - Google Patents

Description

The invention relates to measurement technology and can be used to study the thermal expansion of solids.

Known dilatometer designed to determine the average coefficient of linear expansion, consisting of a heating unit, a microscope-comparator unit backlight, and in the cavity of the heating unit performed consistently located nests, which are installed in the cage samples [ί].

The disadvantage of such a dilatometer is the limited scope of its application, since in the temperature range 20-300K the design of the heating unit with the samples does not allow for its effective cooling and reliable heat protection.

Closest to the proposed is a dilatometer containing a sealed casing, on the cover of which

There is a porthole in the cavity of which a cooled screen is placed, a cylindrical cartridge ^ in the cells of which samples are set with reference marks on them, a meter of small size [2].

The disadvantages of the known device is the limited scope, since it is impossible to determine the coefficient of thermal expansion in vacuum conditions or in the environment of various test Gases due to the fact that samples are cooled directly by vapor of a cryogenic liquid, and this does not allow for vacuum in the volume of the cartridge.

The purpose of the invention is the provision

the possibility of measuring the temperature coefficient of linear expansion *

rhenium in vacuum conditions or in various gaseous media.

3 914980

This goal is achieved by the fact that a dilatometer containing a hermetic casing, on the lid of which a window is located, in the cavity of which a cooled screen is placed, a cylindrical cartridge ^ in the cells of which samples are installed with reference marks on them, the meter of small quantities additionally contains a device , 10 for introducing rotation into a vacuum, associated with a device for introducing rotation to a rack with brackets located in the same plane with it, two light guides, one ends of which 15 are rigidly connected with brackets st Menus and are arranged with their ends against the reference marks of the sample, and the other ends of their ends in contact with the plane illyumina- _m torus.

In addition, pins of highly heat-conducting material are installed in the cells of the cassette, the samples are made in the form of hollow cylinders and 25 are installed coaxially with pins with a gap.

The meter of small linear quantities is rigidly connected to the flat porthole, and on the porthole there is a ₃₀ zero mark passing through the centers of the ends of the optical fibers, and the spring-loaded stand is made of a material with a temperature coefficient of linear expansion close to zero, for example, Invar, and is equipped with an adjusting screw.

The drawing shows the proposed optical dilatometer, a general view. ⁴⁰

The device consists of an airtight casing 4 fitted with a pump-out pipe 1 and a removable lid 2 with a flat window 3, in the cavity of which a cooled ⁴³ screen 5 is placed in the form of an annular cylindrical bath communicated with the cooling and thermoregulation inlets 6 of a cassette 7 with the reference marks 9 placed on them; input 10 of rotation into the vacuum connected with the introduction of rotation of the stand 11 with the brackets 12, two light guides 13, one of the ends of which is rigidly 55 Connected with the brackets 12 and located with their ends against benchmarks 9, θ, other ends

their ends contact with the plane of the porthole 3.

In the cells of the cassette pins 14 are installed, and samples 8 are made in the form of hollow cylinders and mounted coaxially with pins with a gap. The rack 11 is spring-loaded spring 15 and rests on the adjusting screw 16. On the cover 2 is installed measuring optical tube 17, rigidly connected with the flat window 3.

To reduce the measurement error, the rack 11 and the brackets 12 are made of a material with a temperature coefficient of linear expansion close to zero, for example, Invar. On the plane of the porthole 3 marked zero mark passing through the centers of the ends of the optical fibers 13

The cassette 7 is cooled by gaseous refrigerant, which is fed through the inlets 6. The adjustable refrigerant flow allows you to maintain the required temperature of the cassette 7. Grooves are made on the inner surface of the cassette 7 so that the ends of samples 8 with reference marks 9 are viewed through them.

The measurement of the thermal linear expansion coefficient is carried out in a stationary mode as follows.

The adjusting screw 16 lower reference point 9 of sample 8 is visually combined with a zero mark on the window 3. The distance between the ends of the optical fibers 13, facing the sample 8, corresponds to the distance between the reference marks 9.

If the sample is in normal conditions (Τ = 3θΟΚ, Р-1 atm), both reference marks will coincide with the zero mark of the porthole 3. The change in the length of the sample 8 with a step change in temperature is displayed at the end of the light guide 13 as the distance between the displaced upper reference mark 9 and zero mark on porthole 3 and measured by measuring tube 17..

Further, by rotating the rack 11 with a runner, input 10 power, you can set up each sample in turn and at the same time repeat the specified cycle of operations.

Evacuation or flooding of various gases into the airtight cavity

the casing 4 through the pipe 1 allows

test samples 8 in a vacuum or

in the environment of various gases. Availability shty5 914980 6

Ray 14, located inside samples 8, reduces the time it takes to cool down the latter. The cassette 7 is protected from external heat shields by a cooled screen 5, made in the form of an annular cylindrical bath with a liquid refrigerant.

The application of the proposed optical dilatometer allows you to measure the temperature coefficient of linear expansion in vacuum or in an environment of various gases with high accuracy and minimal cost.

Claims (3)

Claim 1. Optical dilatometer containing a hermetic casing, on the lid of which there is a flat porthole. In the cavity of which a cooled screen is placed, a cylindrical cassette, in the cells of which there are specimens with reference marks on them, a measuring device, The fact that, in order to ensure the possibility of measuring the temperature coefficient of linear expansion in various gaseous media or in vacuum, it additionally contains a device for transmitting rotation into a vacuum and the associated spring th rack mounting brackets located with it in the same plane fibers, one ends of which are rigidly connected to the rack brackets and located with their ends opposite to the reference marks of the sample, while the other ends are connected with the ends of the porthole with their ends. 2. Dilatometer according to claim 1, which is based on the fact that, in order to shorten the time for determining the temperature coefficient of linear expansion, in the cells of the cassette pins are installed of high conductivity material, arranged along the axis of the samples, made in the form of hollow 15 cylinders. 3. Dilatometer according to claims 1 and 2, which is characterized by the fact that, in order to increase accuracy, the measuring device is rigidly connected with a flat 20 with an illuminator, a zero mark is applied on the illuminator passing through the centers of the ends of the optical fibers, and the spring-loaded stand is made of a material with a temperature coefficient 25 linear expansion close to zero / and equipped with an adjusting screw.