Patent ID: 6517238
Filing Date: 2003-02-11
Classification: G01N

Abstract:
A system for determining thermal diffusivity in a material sample, comprising:a heat source having an average direction of heat flow directed toward a plurality of infrared receptors associate with an infrared camera; where said infrared receptors are directed in approximate opposition to said average direction of heat flow from said heat source; a sample located between said heat source and said infrared camera such that said sample intercepts a heat flow from said heat source, said sample having a back side and a front side with said back side facing said heat source and said front side facing said infrared camera, said sample defining an orientation of an orthogonal coordinate system having axes x, y and z, such that an x-y plane of said coordinate system is perpendicular to said average direction of said heat flow from said heat source when said heat source is energized and where said z axis is essentially parallel to said average direction of heat flow; a heat insulating shield positioned to cover a portion of said back side of said sample where said heat shield is sized to cover all of said sample located behind said heat shield providing a shielded sample portion and where an interface edge of said shield defines an interface between said shielded sample portion of said sample and an unshielded sample portion which comprises the remainder of said sample in said x-y plane where said interface edge extends across said sample along a linear axial projection effectively bisecting said sample along an axial line; and a computer coupled to said infrared camera, said computer having a plurality of software capable of data acquisition and data processing where said computer receives and records temperature changes with time as sensed by said infrared receptors after a pulse of heat has been emitted from said heat source and compares said recorded temperatures within an equation: T&it;(x,L,t)=aX&it;â€ƒ&it;L&af;[1+2&it;&Sum;m=1âˆž&it;Xm&it;â€ƒ&it;Ï€&it;â€ƒ&it;a&it;sin&it;â€ƒ&it;m&it;â€ƒ&it;Ï€&it;â€ƒ&it;aX&it;cos&it;â€ƒ&it;m&it;â€ƒ&it;Ï€&it;â€ƒ&it;xX&it;exp&it;(-m2&it;Ï€2X2&it;Î±x&it;t)]&it;&AutoLeftMatch;[1+2&it;&Sum;n=1âˆž&it;(-1)n&it;exp&it;(-n2&it;Ï€2L2&it;Î±z&it;t)]when said interface is oriented along a designated y axis partly covering said sample and where T is temperature; x is a point along said x axis; L is a sample thickness measured along said z axis; t is time; X is a width of said sample as measured along said x axis; &agr;x and &agr;z are a lateral (along said x-axis) and a normal (along said z-axis) thermal diffusivity, respectively; and m and n correspond to a number of terms used in a respective summation where said equation is numerically solved for said lateral and said normal diffusivities.