The method for determining the coefficient of thermal expansion of solids

 

(57) Abstract:

(57) the Invention relates to the field of thermophysical measurements and is intended to define thermal expansion coefficient of solid phone Task: getting the true crown-rump length of material at a given temperature and shorter duration tests. The inventive sample continuous section of material with a known density and specific heat capacity at a given initial temperature is subjected to adiabatic compression (tension) is known voltage, measure the resulting temperature change of the sample and calculate thermal expansion coefficient according to the formula. Technical result: improving the performance of the tests when determining KTR solids, the ability to create dilatometric without a measure of the elongation of the sample. table 1.

The invention relates to the field of thermophysical measurements and can be used in experimental determination of the coefficient of thermal expansion of a solid phone

Known methods of determining the coefficient of thermal expansion (CTE) [1] is that the sample is heated (cooled) by a given value of temperature/Voand KTR is calculated by the formula:

< / BR>
This method is adopted for the prototype.

It should be noted that all the variety of existing methods for determining the CTE is the difference or the method of measuring the elongation of a test specimen, either way its heat.

For example, there is an absolute way to determine KTR [2] in which to measure the elongation of the sample is used in the interferometer. The main disadvantage of this method should be considered a necessary step of heating the sample in increments of not less than 5oC K, i.e., at such a significant amount that when calculating the CTD occurs the problem of allocating the found values to a certain temperature. It should be noted and low performance measurements in this method, associated with the necessity of long-keeping model if any change of its temperature in order to achieve its homogeneity volume of the sample. These shortcomings anlauttabelle fatal, because the attempt to reduce the step size of the temperature changes in the experiments leads to a significant drop in accuracy (see Mazurin, O. V. and other Thermal expansion of the glass. L. Nauka, 1969, S. 7).

There are Springe differential expansion of the standard and sample at the same temperature. (see Amatuni, A. N. Methods and devices for determining the temperature coefficients of linear expansion of the materials. M. Of standards, 1972). The measurement of the difference of the progress of the sample and the reference is a photovoltaic device. Knowing thermal expansion of the Etalon, calculate the CTE of the sample.

Some constructive improvements of this method, however, does not allow to get rid of the above shortcomings, are fully characterized and differential methods of determining CTD.

The task, which is aimed by the invention, obtaining the true value of the CTE of the material at a given temperature and a significant reduction in time to conduct the related tests.

The solution to this problem is possible when using effect related thermoelastic solid phone Its essence lies in the fact that during the adiabatic change of the internal energy of a rigid body, by performing external work, the temperature is changing (see Goldenblatt I. I. Nonlinear problems of elasticity theory. M. Nauka, 1969, S. 169-173.

In the particular case, when the body is subjected to uniaxial compression or tension, change>Thethe coefficient of linear thermal expansion, K-1;

Tothe initial sample temperature, K;

the density of the sample, kg/m3;

Cspecific heat, j/kgK;

s1voltage, H/m2;

=T-Tothe adiabatic temperature increment, K.

The above formula allows us to Express the coefficient of thermal expansion through measurable in the experience of the parameters as

< / BR>
The invention consists in the fact that the sample constant cross-section (prism, cylinder, etc.,) with known density and specific heat capacity at a given initial temperature is affected by adiabatic compression (tension) is known voltage, measure the resulting impact of the temperature change of the sample and calculate thermal expansion coefficient in the above formula.

In the study of materials related to the declared object not found objects with attributes identical to the characteristics of the proposed technical solution, based on which a conclusion is made about its compliance with the criterion of "inventive step". As well as not found solutions that would contain the full set of features offer the population KTR solids has the following advantages over the prototype. Because the definition of the coefficient of thermal expansion of the proposed method was accompanied by a very small deviation from the initial temperature (at least in the 50oC100 times less than in protivopostavljaemyh ways), the calculated value of KTR is really true, attributed to the initial temperature of the experience. Due ecogarantie method can be effectively used when the radiation KTR In his area of significant changes, for example, in the area of phase transitions.

In addition, if contrasted how the duration of a single experience is on the order of hours, which is associated with the requirement of homogeneity of the sample temperature, to experiment the proposed method is not more than 2 to 3 seconds, i.e. about 1000 times less.

To check the possibility of determining the coefficient of thermal expansion of solids of the proposed method and compare the obtained results with the available reference data were tested samples of aluminum and organic glass (copolymer of PMMA brand 2-55). Samples of aluminum with dimensions h,5x1,8 mm, and samples of organic glass with dimensions HH,1 mm was subjected to tensile PR heat transfer of the sample with the surrounding air is negligible, that allows us to consider the conditions of the experiment are very close to adiabatic. As temperature sensors were used film Nickel resistance thermometers included in the pavement measuring circuit so that its output has formed an electrical signal proportional to the temperature difference between the sample and the environment.

The following table presents the results of these experiments, from which it follows that the values of the coefficient of thermal expansion are in satisfactory agreement with the reference data (see Tables of physical quantities. Under. Ed. by Acad. And. Of K. Kikoin. M Atomizdat, 1976. - 1008 S. Gudimov M. M. Petrov B. C. Organic glass. M. Chemistry, 1981. - 216 C.)

These examples suggest the feasibility of the method of determining the CTE of solids, in which this option could actually be considered a true value relating to virtually point temperature and not the temperature interval.

In addition, the proposed method of determining KTR very productive, since the time of the experiment is determined solely by the mechanical speed of the loading system and the inertia of t is camping in that affect the pattern of constant cross-section with known density and specific heat capacity at a given initial temperature, measure the temperature change before and after exposure to determine the coefficient of thermal expansion, wherein the effect on the sample is carried out by adiabatic compression (tension) is known voltage, and thermal expansion coefficient is determined by the formula

< / BR>
where the density is kg/m3;

Cspecific heat, DN/kg;

T initial sample temperature, K;

s axial stress in the sample, n/m2;

q adiabatic temperature increment sample K.

 

Same patents:

The invention relates to measurement techniques, in particular to methods and devices for determining the deformation of the airframe

The invention relates to the study of physical-mechanical properties of rolled metals, namely the anisotropy of plasticity and viscosity, which causes formation during welding of layered cracks

FIELD: testing engineering.

SUBSTANCE: device comprises high-frequency generator and inductor connected in series, device for control of heating, system for air supply, device for external cooling, measuring system, unit of contact temperature gauges, and device for bottom clamping connected with the end section of the blade. The device is provided with a means for axial loading, device for top clamping connected with the shelf of the end section of the blade, device for control of axial loading, first dynamometer, device for applying torque, which has the second dynamometer, device for information input, load-bearing frame, contactless temperature gauge, generator of nonstandard signals, oil pumping system, and device for internal cooling.

EFFECT: enhanced reliability of testing.

7 cl, 1 dwg

FIELD: measuring technique.

SUBSTANCE: method comprises heating the heat-shield structure from one side up to a high temperature, cooling the structure, applying marker dots on the section of the outer surface under study, cutting the axisymmetric specimens of the heat-shield structure, applying marker dots on the side of the specimen at a given distance from the inner surface, cutting the specimen over the planes perpendicular to its longitudinal axis and passing through the marker dots into pieces, subsequent heating of the pieces in the atmosphere of an inert gas, recording the change of weight of the pieces, recording the temperature of the beginning of the decrease of weight of each piece, and judging on the spatial temperature distribution from data obtained.

EFFECT: expanded functional capabilities.

5 dwg

FIELD: physics.

SUBSTANCE: stone sample saturated with water is frozen to a specified temperature. The sample is unfrozen and deformation is measured. Before freezing, the threshold load which accounts for long-term compression strength of the sample is measured using a nondestructive method. After several thermal cycles, residual deformation of the unfrozen sample is measured in the direction perpendicular the previous compression. A least residual deformation is achieved through periodical compression of the sample in the current direction from zero to a load which exceeds the threshold by not more than a third. The number of thermal cycles required for reducing long-term strength to the required value is determined by repeating these operations.

EFFECT: reduced labour input and increased efficiency.

1 tbl

FIELD: physics.

SUBSTANCE: method of determining heat resistance of bentonite clay is characterised by that, a nomograph which reflects dependency of temperature of the second endothermal effect and heat resistance of bentonite clay from contained structural iron is constructed first. For this purpose samples of bentonite clay from known deposits are analysed. The samples are tested in a derivatograph. Derivatograms with differential thermo-weighted (DTW) and differential thermal (DT) curves are obtained, from which temperature of the second endothermal effect is determined depending on structural iron contained in the samples. Heat resistance of the samples is determined depending on structural iron contained in the samples. From the said two curves, the said nomogram is constructed, which is then used for subsequent determination of heat resistance of the analysed bentonite clay; a wet ground up sample is tested in a derivatograph by heating followed by drying. Derivatograms with differential thermo-weighted and differential thermal curves are obtained, from which temperature of the second endothermal effect is determined and heat resistance of the analysed bentonite clay is determined from the said nomogram.

EFFECT: cutting on time and simplification of the process of determining heat resistance.

2 dwg

FIELD: physics.

SUBSTANCE: device has a cylindrical housing, a horizontal partition wall and sensors for monitoring and controlling tests. Inside the cylindrical housing, which has a flat bottom and an air-tight cover which is fixed by bolts and nuts in the top part, there is a drum which is mounted on the cover inside the housing. The horizontal partition wall is placed in the bottom part of the drum and is in form of a perforated disc whose perforations are in form of calibrated orifices lying on a circle, having along their edge calibrated channels for passage of heating medium. Inside the drum there is an additional horizontal partition wall with calibrated orifices which are exactly as those in the perforated disc. Sample pipes are fitted in the perforations of the disc and are fixed on the cover of the housing, and there are vertical partition walls between the pipes. Pipes with a smaller diameter are fitted inside each sample pipe and are fixed in a dispensing receiver and have in their top part connecting pipes for outlet of cooling medium and discharge pipes with calibrated devices on them. In the bottom part of the housing under the perforated disc there is a pipe with a diffusion nozzle connected to a cylindrical diffuser and a connecting pipe for inlet of heating medium and a system of chambers with a connecting pipe at the bottom for outlet of the heating medium.

EFFECT: high quality and accuracy of tests and efficiency thereof.

3 dwg

FIELD: transport.

SUBSTANCE: invention relates to space hardware testing, namely to installations for simulation of spacecraft components operation modes. Installation for vacuum thermocycling of photoconverter panels includes vacuum chamber consisting of two communicating compartments. In one compartment, two cryopanels are installed in parallel with possibility to place tested panel between them. In the second compartment there is thermal panel made as assembly of filament lamps. The cryopanels and thermal panel are positioned vertically, and thermal panel compartment is placed over cryopanel compartment. The cryopanels are installed with possibility of additional placement of thermal panel between them. The thermal panel is provided with reciprocating mechanism of vertical action and thermal insulation at the side facing cryopanel.

EFFECT: higher accuracy of thermal simulation of outer space conditions.

3 cl, 4 dwg

FIELD: testing equipment.

SUBSTANCE: device comprises a body with a flange joint and tested samples in the form of tubes. Tested samples in the amount of two arranged coaxially one inside the other to form a circular gap between them, are fixed inside separate parts of the body, placed on a header of hot water and a header of drainage of a mixture of hot and cold water. Headers by means of pipelines are connected to a heater and a refrigerator. The outer surface of the outer tube and the inner surface of the central tube are coated with a layer of insulation. In the upper part of the body there is a nozzle and a valve for supply and control of cooling water flow.

EFFECT: elimination of medium working pressure impact at process of crack formation, providing for pure crack formation only due to pulsation of medium temperature, which results in getting absolutely accurate testing results.

1 dwg

FIELD: test equipment.

SUBSTANCE: stand includes base, coaxial sample grips mounted on the base, sample loading device connected to the grips, mechanical sample processing device and platform for processing devise movement against grip axes. Additionally the stand features aggregate for grip turning around grip axis, consisting of drive with two gear wheels bearing the grips, on the drive shaft.

EFFECT: extended functionality of stand due to test performance at changing directions of mechanical processing against radial directions of sample.

1 dwg

FIELD: testing equipment.

SUBSTANCE: invention relates to testing equipment, to tests of mostly samples of rocks. The bench comprises a base, sample grips installed on it coaxially, a device to load a sample with an axial mechanical load, a mechanism for interaction with the sample, a platform for movement of the mechanism along the axis of the grips, a platform for movement of the mechanism in the vertical direction perpendicularly to the axis of the grips and a platform for movement of the mechanism in the horizontal direction perpendicularly to the axis of the grips. The mechanism for interaction with the sample is made as milling.

EFFECT: expansion of functional capabilities of a bench by provision of research with gradual removal of material sample without removal of mechanical load.

1 dwg

FIELD: test equipment.

SUBSTANCE: device includes gas generator and operation part with structural material sample, connected in series. Gas generator features removable mixing head. Cylindrical combustion chamber of the gas generator features ignition device and orifice plate. Operation part includes interconnected clamping flange with central hole and flange holding a sample. Central longitudinal axes of flange and sample are coincident. Internal cylindrical surface of clamping flange forms an annular slot with the sample surface, the slot joins a cavity ending with output nozzle through end outlet holes in the flange around sample.

EFFECT: possible maintenance of required pressure-heat loading modes for samples, modelling natural thermal stress state of structural materials of various aggregates operating in alternate heat modes.

1 dwg

Up!