RU-2848986-C9 - METHOD FOR DETERMINING THE SPREAD OF THE TEMPERATURE FIELD IN A MATERIAL WHEN ITS SURFACE IS HEATED

Abstract

FIELD: thermophysical measurements. SUBSTANCE: invention relates to measurements using a non-contact method for temperature field propagation in materials when their surface is heated by infrared rays and can be used in the study of the thermophysical properties of isotropic and anisotropic materials, in particular those of plant origin. The essence of the claimed method is that the experimental sample of the material under study is first divided into two parts in a plane perpendicular to the heating surface by infrared heating, followed by joining the parts of the sample at the division surfaces by compressing the parts of the sample. After that, the surface of the sample being studied, perpendicular to the plane of its division, is subjected to infrared heating, and at the end of the exposure , the divided sample of the material being studied is released from compression, separated into its constituent parts, and thermal imaging scanning of the sample's division surfaces is performed using a thermal imager (e.g., model Testo 882), visualization of the spatial shape of the temperature field distribution and its quantitative analysis are performed in the MathCad environment using the testo IRSoft software. EFFECT: expansion of the research capabilities of the method, namely, the ability to obtain contactless thermograms of the temperature field distribution in the volume of material under the heated surface of both isotropic and anisotropic materials. 1 cl, 10 dwg

Inventors

• ZAVALIJ ALEKSEJ ALEKSEEVICH
• Lago Lyudmila Anatolevna
• Volozhaninov Sergej Sergeevich
• Rutenko Vladimir Stepanovich

Dates

Publication Date

20260506

Application Date

20250324

Claims (1)

1. A method for determining the propagation of a temperature field in a material upon heating its surface, comprising heating the surface of a sample of the material being tested with infrared radiation, measuring the parameters of the temperature field remotely with a thermal imager, characterized in that the sample of the material being tested is, prior to infrared heating, divided into two parts in a plane perpendicular to the heating surface, followed by joining the parts of the sample by the surfaces of dissection by compressing the parts of the sample, after which the surface of the sample being tested, perpendicular to the plane of its dissection, is subjected to infrared heating, upon completion of the exposure, the dissected sample of the material being tested is released from compression, separated into its component parts and thermal imaging scanning of the surfaces of dissection of the sample is performed, visualization of the spatial form of propagation of the temperature field and its quantitative analysis is performed in the MathCad environment.

Description

The proposed invention relates to thermophysical measurements, namely measurements using a contactless method of temperature field propagation in materials when their surface is heated by infrared rays, and can be used in studying the thermophysical properties of isotropic and anisotropic materials, in particular those of plant origin. A method for measuring the spatial distribution of temperature and a device for implementing it are known (patent RU, No. 2194956, IPC G01K 7/00, 2002), which consists (the first version) of placing a plurality of temperature-sensitive sensors connected in parallel by a two-wire line at controlled points, supplying an alternating voltage signal to one of the line inputs and recording the input alternating current iin(t), while quartz piezoelectric resonance sensors with different resonant frequencies ω are used as temperature-sensitive sensors.p1, ωp2,…ωpi,… ωpN, and as an alternating voltage signal supplied to one of the inputs of the two-wire line, a signal with a spectrum covering the frequency range of quartz piezoelectric resonant sensors is used, after recording the input alternating current iin(t) calculate its amplitude spectrum S(ω), determine the resonant frequencies of quartz piezoelectric resonance sensors ωp1, ωp2,…ωpi,…ωpNby the position of the maxima of the amplitude spectrum S(ω), then by the previously experimentally found or theoretically known dependences of the resonant frequency of quartz piezoelectric resonant sensors on the temperature ωri(t) the desired temperature is determined at the controlled points, (the second variant of the method) consists of placing a plurality of temperature-sensitive sensors at the controlled points, and a signal with frequency modulation in the range of resonant frequencies of quartz piezoelectric resonance sensors is used as an alternating voltage signal supplied to one of the inputs of the two-wire line, the device for measuring the spatial distribution of temperature contains a plurality of temperature-sensitive sensors connected in parallel by a two-wire line connected to a recorder, which is connected to an alternating voltage source, quartz piezoelectric resonance sensors with different resonant frequencies ω are used as temperature-sensitive sensorsp1,ωp2,… ωri,…ωpN, the recorder contains a series-connected matching circuit, an alternating current amplitude recorder, a spectrum analyzer, a processing and indication unit, and a signal generator with a spectrum covering the frequencies of quartz piezoelectric resonance sensors is used as a source of alternating voltage. The disadvantage of this method is the need to introduce temperature-sensitive sensors into the test sample of material, i.e., to carry out destructive testing. Also known is a method for identifying hidden subsurface objects in the soil (RU Patent No. 2395074 C2, IPC G01N 25/18, 2006), which consists of applying heat from an infrared heating source to the soil surface, measuring the radiation temperature on the soil surface, calculating a mathematical model of the direct heat conductivity problem based on the finite difference method, while measuring the radiation temperature at all points of the spatial grid of the probed (investigated) surface during heating of the soil for 90 seconds and subsequent cooling for 90 seconds, and using a one-dimensional intermediate grid function of the heating source on the soil surface to reconstruct the temperature field by the heating depth. The disadvantage of this method is the low accuracy of measuring thermophysical parameters (thermal diffusivity, thermal conductivity), and it also requires a lot of time to calculate the required values of thermophysical parameters, The method for measuring the spatial distribution of thermophysical parameters of isotropic materials was chosen as a prototype (RU patent No. 2544890, IPC G01N 25/18, 2015), including thermal action from an infrared heating source over the entire visible surface of the isotropic material under study, measuring the radiation temperature at all points of the spatial grid of the surface of the isotropic material under study by a thermal imaging receiver, calculating a mathematical model of the direct problem of heat conductivity based on the finite difference method, while uniformly heating the surface of the isotropic material under study from the infrared heating source, using several reference materials to estimate the unknown parameters of the mathematical model, placing an infrared heating source in front of the thermal imaging receiver at a given distance from each other and at a height from the isotropic material under study/reference material so that the thermal radiation reflected from the surface of the isotropic material from the infrared heating source does not enter the lens of the thermal imaging receiver, moving the infrared heating source and the thermal imaging receiver along the surface of the isotropic material the test/reference ma