Transient thermal method and means for nondestructively testing a sample

Claim 3

The method according to claim 1 wherein the generation and transmission of said transient-function heat flux and the measurement of said surface thermal impedance comprises generating an impulse-function heat flux, transmitting said heat flux into said sample, generating synchronously with said impulse-function heat flux sine- and cosine-function signals, multiplying said generated sine-function signal and said measured transient surface temperature to obtain a first output signal, multiplying said generated cosine-function signal and said measured transient surface temperature to obtain a second output signal, and integrating said first and second output signals, which first and second integrated output signals provide a measure of the complex values of the surface thermal impedance of said sample.

Claim 4

The method according to cLaim 1 wherein the generation and transmission of said transient-function heat flux and the measurement of said surface thermal impedance comprises generating a step-function heat flux, transmitting said heat flux into said sample, differentiating said measured transient surface temperature, generating synchronously with said transient-function heat flux sine- and cosine-function signals, multiplying said generated sine-function signal and said measured differentiated transient surface temperature to obtain a first output signal, multiplying said generated cosine-function signal and said measured differentiated transient surface temperature to obtain a second output signal, and integrating said first and second output signals, which integrated signals are a measure of the complex values of the surface thermal impedance of said sample.

Claim 5

The method according to claim 1 wherein said surface thermal impedance measurement comprises measuring the value of said transient-function heat flux applied to the surface of said sample, generating synchronously with said transient-heat flux sine- and cosine-function signals, multiplying and integrating said cosine-function signal and said measured transient-function heat flux to provide a first output signal, multiplying and integrating said cosine-function signal and said measured transient surface temperature to provide a second output signal, multiplying and integrating said sine-function signal and said measured transient-function heat flux to provide a third output signal, multiplying and integrating said sine-function signal and said measured transient surface temperature to provide a fourth output signal, squaring said first, second, third and fourth output signals, summing said first and third squared output signals, summing said second and fourth squared output signals, dividing the summed second and fourth squared output signals by the summed first and third squared output signals to provide a first-ratio measure, measuring the square root value of said first-ratio measure, dividing said third output signal by said first output signal to provide a second-ratio measure thereof, dividing said fourth output signal by said second output signal to provide a third-ratio measure thereof, measuring the arc tangent of each said second and third-ratio measures, the subtracting the third-ratio measure arc-tangent value from the second-ratio measure arc-tangent value to provide a measure of the phase angle of the surface thermal impedance of said sample, said square root value of said first-ratio measure being a measure of the amplitude of the surface thermal impedance of said sample.

Claim 8

The method according to claim 5 wherein exciting said transducer to transmit a transient-function heat flux into the surface of said sample and the measurement of said input thermal impedance of said transducer comprises exciting said transducer to transmit an impulse-function heat flux into the surface of said sample, generating synchronously with said impulse-function flux generation sine- and cosine-function signals, multiplying said sine-function signal and said measured transducer transient surface temperature to provide a first output signal, multiplying said cosine-function signal and said measured transducer transient surface temperature to provide a secoNd output signal, and integrating said first and second output signals, which integrated first and second output signals provide a measure of the complex values of the surface thermal impedance of said sample.

Claim 9

The method according to claim 5 wherein exciting said transducer to transmit a transient-function heat flux into the surface of said sample and the measurement of said input thermal impedance of said transducer comprises exciting said transducer to transmit a step-function heat flux into the surface of said sample, generating synchronously with said step-function heat flux generation sine- and cosine-function signals, differentiating said measured transducer transient surface temperature, multiplying said sine-function signal and said differentiated measured transducer transient surface temperature to provide a first output signal, multiplying said cosine-function signal and said differentiated measured transducer transient surface temperature to provide a second output signal, and integrating said first and second output signals, which integrated first and second output signals provide a measure of the complex values of the surface thermal impedance of said sample.

Claim 10

The method according to claim 5 wherein said thermal transducer is mounted engaging the surface of said sample in intimate contact therewith to optimize thermal coupling between said sample and said transducer.

Claim 11

The method according to claim 5 wherein said transducer input thermal impedance measurement comprises measuring the excitation power applied to said transducer to transmit said transient heat flux to said sample, generating synchronously with said transient heat flux sine- and cosine-function signals, multiplying and integrating said cosine-function signal and said measured transducer excitation power to provide a first output signal, multiplying and integrating said cosine-function signal and said measured transducer transient surface temperature to provide a second output signal, multiplying and integrating and sine-function signal and said measured transducer exciting power to provide a third output signal, multiplying and integrating said sine-function signal and said measured transducer transient surface temperature to provide a fourth output signal, squaring said first, second, third and fourth output signals, summing said first and third squared output signals, summing said second and fourth squared output signals, dividing the summed second and fourth squared output signals by the summed first and third squared output signals to provide a first-ratio measure, measuring the square root value of said first-ratio measure, dividing said third output signal by said first output signal to provide a second-ratio measure thereof, dividing said fourth output signal by said second output signal to provide a third-ratio measure thereof, measuring the arc tangent of each said second and third-ratio measures, and subtracting the third-ratio measure arc-tangent value from the second-ratio measure arc-tangent value to provide a measure of the phase angle of the input thermal impedance of said transducer, said square root value of said first-ratio measure being a measure of the amplitude of the input thermal impedance of said transducer.

Claim 16

The apparatus according to claim 11 wherein said transient heat flux means generate and transmit an impulse-fraction heat flux into said sample, and said surface thermal impedance measuring means comprise means for generating sine- and cosine-functions synchronously with said impulse-function heat flux means, means for multiplying each of said sine- and cosine-functions with said measured transient surface temperature to provide first and second output signals, and means for integrating said first and second output signals, which integrated first and second output signals provide a measure of the complex values of the surface thermal impedance of said sample.

Claim 17

The apparatus according to claim 11 wherein said transient-function heat flux means generate and transmit a step-function heat flux into said sample and wherein said surface thermal impedance measuring means comprise means for generating cosine-and sine-functions synchronously with said step-function heat-flux means, a differentiator connected to differentiate the measured transient surface temperature, means for multiplying each of said generated sine- and cosine-functions with said differentiated measured transient surface temperature to provide first and second output signals, and an integrator connected to integrate said first and second output signals, which integrated first and second output signals are a measure of the complex values of the surface thermal impedance of said sample.

Claim 20

The apparatus according to claim 14 wherein said transducer comprises a layer of material having a high-frequency thermal response to provide optimal thermal equilibrium between said material and said sample surface a minimal time after application of said transient-function heat flux.

Claim 21

The apparatus according to claim 14 wherein said transducer is mounted contiguous to said surface of said sample and comprises a thin layer of electrically conductive material, and an electrical insulator between said conductive layer and said sample surface.

Claim 22

The apparatus according to claim 16 wherein said transducer exciting means comprise means for applying a transient-function signal across said electrically conductive material to pass a transient-function current therethrough.

Claim 23

The apparatus according to claim 16 further including evacuative means engaging said transducer and said sample to provide positive engagement with said transducer and said surface of said sample.

Claim 24

The apparatus according to claim 14 wherein said transducer comprises a thermally-responsive-image-generating material, and a high-frequency-thermally-responsive material mounted between said image-generating material and said surface of said sample contiguous to said image-generating material and proximate said sample surface.

Claim 25

The apparatus according to claim 19 wherein said high-frequency-thermal material is electrically conductive and said transducer exciting means comprise thermally-transparent means electrically insulating said high-frequency-thermal material from said sample surface, and means for generating a transient-function current flow uniformly through said high-frequency-thermal material.

Claim 30

The apparatus according to claim 22 wherein said material exciting means comprise said high-frequency-thermally-responsive material being electrically conductive, means for generating a transient-function current uniformly through said high-frequency-thermally-responsive material, and means interposed of said high-frequency-thermally-responsive material and said sample surface to effect electrical isolation therebetween.