SU1635099A1 - Method of complex measurement of thermophysical characteristics of materials - Google Patents

Abstract

The invention relates to experimental thermophysics and can be used to determine the thermal and thermal diffusivity of materials by a non-destructive method. The purpose of the invention is to increase accuracy. A linear heat source is installed on the flat surface of the studied material. After applying the heat pulse, the temperature is measured at three points located perpendicular to the linear heat source. Moreover, the temperature measurement is carried out at the moment when the maximum temperature reaches 1 point at the midpoint. Yo

Description

The invention relates to experimental thermophysics and can be used to determine the thermal and thermal diffusivity of materials by a non-destructive method.

The purpose of the invention is to improve accuracy.

The drawing is a diagram for the implementation of the proposed method.

On a flat surface of a semi-infinite thermally set material, a pulsed heat source 1 and a temperature sensor are installed with three thermocouples 2 arranged perpendicular to the linear heat source on the surface of the material under study 3.

After applying the heat pulse to the heat source, a tracking system (not shown) connected to the three thermocouples is put into operation, and the time at which the temperature at the additional point (T2) reaches its maximum value is recorded. At this moment, the temperature is measured at the first (Ti) and third) points and these values are already used to calculate the thermal and thermal diffusivity.

The formulas for calculating these characteristics are obtained from solving the heat conduction equation under the action of a pulsed linear heat source on the surface of a material that is semi-thermally limited:

(bf

T lt-. 0: (2)

About CJ

ate about

| Yu Yu

, ET fQd (t) npMx O, Z 0; ten ,

31 i

Tjx

at: 0

where T is the temperature; X, Z, Y - coordinates; t- time;

AD - coefficients of thermal diffusivity and thermal conductivity;

Q is the amount of heat released per unit length of the linear heat source per unit time;

d (t) is a unit of time (delta function).

The solution of the system of equations (1) - (4) For the body surface () has the form

T (X-) (-Ta ® From here at the time of measurement (g Gism) of temperatures, provided that the maximum temperature is reached in J2

T2 max, (6)

get

Ti exp (

TGATiem

.-Xl.v 4a giam

tQf HZ h.

12 2tgAgizmeHr1

-g Qg X§h

 3-2lAgismHr (.

Using expression (7) to calculate the Ti / T2 ratios; Ti / Tz and T2 / Tz. dependencies are obtained for calculating a and A of the material under study

x3-x2

4 Tysm In ()

(eight)

T2

exp (x2

4agism

) W

(A 170;

W

a 5.8 10

-5M2,

with

0

m K

When the maximum temperature is reached at the XC point, the calculated thermal diffusivity is 5.8228 xU m / s. For the points in time before and after reaching the maximum temperature at point X2, the calculated values of thermal diffusivity are respectively

5,843 10 5m2 / si5,945.

The presence of the optimal time for temperature measurement (at T2 max), corresponding to the minimum value of the error in determining the desired characteristics, is associated with the greatest thermal response of the zone of the material under investigation, in which the measuring points of the material temperature are located.

The use of this invention improves the accuracy of determining the thermal and thermal diffusivity of materials 5 by a non-destructive method.

Claims (1)

Claims An integrated method for determining the thermophysical characteristics of materials, including heating a flat surface of the material with a linear pulsed heat source of constant power, measuring at a given time point the temperature at two points located perpendicular to the linear pulsed heat source, and with the subsequent calculation of the desired characteristics, e different in that. that, in order to increase accuracy, the temperature is measured at an additional point located between the two first points, the temperature Q of which is recorded at the moment when the maximum temperature is reached at the additional point, and the desired characteristics are determined by the formulas:  x5-x five but 4 Tysm In () where Xi, X2, Xs are the coordinates of the location of thermocouples on the surface of the material. Formula (9) is obtained from the second equation (7). To confirm the positive effect of using the invention, a parametric calculation of the thermal state of the material under investigation is carried out for given values of thermal conductivity and thermal diffusivity of the material. 0 five A 0 / (2l: giem T2) exp (-X2 / 4a gizm), where AD is, respectively, thermal diffusivity and thermal conductivity of the material under study; X1, X2, Xs are the coordinates of the points at which temperature is measured; T1.T2, Tz - measured temperature values at points X1, X2.Hs; measure the time to reach the maximum temperature at the additional point X2; Q is the amount of heat released per unit length of the linear heat source.