METHOD FOR DETERMINING THERMAL CONDUCTIVITY OF OPTICALLY TRANSPARENT MATERIALS Russian patent published in 2020 - IPC G01N25/18 G01J5/60 

FIELD: test technology.

SUBSTANCE: invention relates to thermal tests, namely to measurement of thermophysical properties of materials, in particular to thermal non-destructive testing of objects, and can be used for technical diagnostics of structures using methods based on creation of heat fields by point heating. Method of determining thermal diffusivity of optically transparent materials involves thermal stepped action from a heating source on the surface of the analyzed article and subsequent analysis of the non-stationary thermal picture. Heat heating is generated by an external "point" energy source localized to a target of the size of about 1 mm² from optically opaque material, which is formed on the surface of the sample, and recording, using a thermal imager, an evolution of temperature distribution on the article surface created in a defect-free controlled article as a system of concentric circular isotherms, which position in time is determined by averaging information from a large number of pixels of a thermal imager array, which is fixed relative to the center of the heating spot image. Point energy source used is laser with visible wavelength of 445 nm and power of up to 30 W and controlled duration, and an opaque "target" is created on the surface of the optically transparent samples, for example, using a thermal paste or a heat-conducting adhesive, placing a flat lead disc with diameter of 0.5–1.5 mm, a thickness of <0.5 mm or carbonization, or destruction of point of sample heating with short pulse of high power laser or contact of heated rod with diameter of up to 0.5 mm with material surface.

EFFECT: providing an non-sampling express analysis and determining a thermal diffusivity coefficient in objects which are transparent in the optical range and are opaque in the infrared and have at least one flat area with dimensions in the lateral direction of not less than 10 mm, as well as possibility of applying the approach to measurement of thermal diffusivity in large objects directly at the location of their location without cutting samples from them and with one-sided access to them.

3 cl, 4 dwg, 1 tbl