Patent US4928254A successfully refreshed from Google Patents.
US4928254A
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Laser flash thermal conductivity apparatus and method
Assignee: Dow Chemical Co
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Filing: 1988-04-28
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Granted: 1990-05-22
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Expires: 2008-04-28
Abstract
Abstract A sequence of temporally-spaced radiant energy pulses are applied to the front surface of the sample and the heat rise caused by each thermal pulse is measured at the second surface using a suitable thermocouple or infrared sensor. The temperature rise data for each pulse is digitized and stored in a two-state memory device such as a random access memory. The data from each successive pulse is coadded and statistically processed by averaging to derive a set of favored values indicative of the temperature of the sample as a function of time. The favored values data is further processed using a least squares curve fitting algorithm to determine a numerical value indicative of the diffusivity of the sample.
Inventors
- 👤 Arne K. Knudsen
- 👤 Scott H. Delzer
- 👤 Charles A. Langhoff
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 15:18
CPC Classifications
G; G01; G01N; G01N21/00; G01N21/62; G01N21/71; G01N25/00; G01N25/18
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
146 words
A method of ascertaining the thermal diffusivity of a sample comprising: applying a plurality of discrete temporally-spaced radiant energy pulses to a first portion of said sample, each of said radiant energy pulses having a peak power below the level at which damage to said sample occurs, each of said radiant energy pulses causing a discrete temperature rise pulse to propagate through said sample to a second portion of said sample; sensing said temperature rise pulses at said second portion and electrically recording said sensed temperature rise pulses as data in a two-state memory device wherein each discrete temperature rise pulse corresponds to a discrete datum; statistically processing said data to derive a set of favored values indicative of the temperature of said second portion as a function of time; and further processing said set of favored values to determined the thermal diffusivity of said sample.
Claim 2
Independent Claim
146 words
A method of ascertaining the thermal diffusivity of a sample comprising: applying a plurality of discrete temporally-spaced radiant energy pulses to a first portion of said sample, each of said radiant energy pulses having a peak power below the level at which damage to said sample occurs, each of said radiant energy pulses causing a discrete temperature rise pulse to propagate through said sample to a second portion of said sample; sensing said temperature rise pulses at said second portion and electrically recording said sensed temperature rise pulses as data in a two-state memory device wherein each discrete temperature rise pulse corresponds to a discrete datum; statistically processing said data to derive a set of favored values indicative of the temperature of said second portion as a function of time; and further processing said set of favored values to determined the thermal diffusivity of said sample.
Claim 3
Dependent Claim
17 words
The method of claim 1 wherein said step of statistically processing said data comprises averaging said data.
Claim 4
Dependent Claim
29 words
The method of claim 1 wherein said step of further processing said set of favored values comprises operating on said favored values using a least squares curve fitting algorithm.
Claim 5
Dependent Claim
59 words
The method of claim 3 wherein said curve fitting algorithm is selected to fit said set of favored values to the following equation: f(x)=c+b(1-2exp(-ax)+2exp(-4ax)) where c is the baseline of a curve defined by said set of favored values, wherein b is the amplitude of said curve and wherein a is related to the thermal diffusivity of said sample.
Claim 6
Dependent Claim
52 words
The method of claim 3 wherein said curve fitting algorithm is selected to fit said set of favored values to the following equation: ##EQU4## where T m is the maximum temperature, α is the diffusivity, n is the index, t is the time, L is the thickness and T is the temperature.
Claim 7
Dependent Claim
17 words
The method of claim 1 wherein said radiant energy pulses have a peak power below one joule.
Claim 8
Dependent Claim
47 words
The method of claim 1 further comprising applying an opaque coating to said sample prior to said step of applying a plurality of temporally-spaced radiant energy pulses and wherein said radiant energy pulses have a peak power below the level at which damage to said coating occurs.
Claim 9
Independent Claim
178 words
An apparatus for ascertaining the thermal diffusivity of a sample comprising: a support stand; a laser means disposed on said support stand for applying a plurality of discrete temporally-spaced radiant energy pulses to a first portion of said sample, each of said pulses having a peak power below the level at which damage to said sample occurs, each of said pulses causing a discrete temperature rise pulse to propagate through said sample to a second portion of said sample; a means for sensing said temperature rise pulses at said second portion disposed on said support stand; a means coupled to said sensing means for electrically recording each of said sensed temperature rise pulses as data in a two-state memory device wherein each discrete temperature rise pulse corresponds to a discrete datum; means coupled to said recording means for statistically processing said data to derive a set of favored values indicative of the temperature of said second portion as a function of time and for further processing said set of favored values to determined the diffusivity of said sample.
Claim 10
Independent Claim
178 words
An apparatus for ascertaining the thermal diffusivity of a sample comprising: a support stand; a laser means disposed on said support stand for applying a plurality of discrete temporally-spaced radiant energy pulses to a first portion of said sample, each of said pulses having a peak power below the level at which damage to said sample occurs, each of said pulses causing a discrete temperature rise pulse to propagate through said sample to a second portion of said sample; a means for sensing said temperature rise pulses at said second portion disposed on said support stand; a means coupled to said sensing means for electrically recording each of said sensed temperature rise pulses as data in a two-state memory device wherein each discrete temperature rise pulse corresponds to a discrete datum; means coupled to said recording means for statistically processing said data to derive a set of favored values indicative of the temperature of said second portion as a function of time and for further processing said set of favored values to determined the diffusivity of said sample.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-05-21 | 1993-11-20 | 1994-05-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-05-21 | 1997-11-20 | 1998-05-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-05-21 | 2001-11-20 | 2002-05-22 | $7700.00 | Window Closed / Lapsed |