METHOD FOR MEASURING THICKNESS BY PULSED INFRARED THERMAL WAVE TECHNOLOGY

• US 20140153608A1
• Filed: 06/14/2011
• Published: 06/05/2014
• Est. Priority Date: 06/09/2011
• Status: Active Grant

• Current Assignee: Capital Normal University (Beijing Education Commission), Beijing Waiteksin Advanced Technology Co., Ltd., Chongqing Normal University
• Original Assignee: Capital Normal University (Beijing Education Commission), Beijing Waitenksin Advanced Technology Company Limited, Chongqing Normal University
• Inventors: Wang, Xun, Zeng, Zhi, Tao, Ning, Feng, Lichun
• Granted Patent: US 9,464,891 B2
• Time in Patent Office: Days
• US Class Current: 374/5
• CPC Class Codes: G01B 21/085 using thermal means
• CPC Class Codes: G01N 25/72 Investigating presence of flaws

Abstract

A method for measuring thickness or defect depth by pulsed infrared thermal wave technology is described. The method includes heating a measured object by pulsed heating devices, and at the same time, obtaining a thermal image sequence on the surface of the measured object by an infrared thermography device, and storing the thermal image sequence in a general-purpose memory. The method also includes multiplying a temperature-time curve at every point of the thermal image sequence by a corresponding time, thereby obtaining a new curve. The method also includes calculating a first-order differential and obtaining a peak time thereof. The method also includes use of one or more formulas to thereby determine the thickness or the defect depth of the measured object.

Claims

1. A method for measuring thickness by using pulsed infrared thermal wave technology, comprising:

(1) heating a measured object by a pulsed heating device, and at the same time, obtaining a thermal image sequence on the surface of the measured object by an infrared thermal imager, and storing the thermal image sequence in a general-purpose memory;

(2) multiplying a temperature-time curve of each pixel in the thermal image sequence by √

{square root over (t)} of corresponding time t, thereby obtaining a new curve f;

(3) calculating a first-order differential for the f to obtain a f′

, and obtaining a peak time t_apst of the f′

;

(4) calculating L=√

{square root over (2α

t_apst)} by a formula

2. The method for measuring thickness or defect depth by using pulsed infrared thermal wave technology according to claim 1, wherein the thermal diffusivity coefficient α

is known.

3. The method for measuring thickness or defect depth by using pulsed infrared thermal wave technology according to claim 1, wherein the thermal diffusivity coefficient α

is unknown, a sample which has the same material property as the measured object and which has a known thickness or a known defect depth L is selected as a standard sample, the standard sample is measured according to the steps (1)-(3) of claim 1 to obtain the t_apst of the standard sample, and thus a linear relationship between t_apst and L² of the standard sample is obtained, and a value L of the measured object is calculated according to the linear relationship and the value t_apst of the measured object.

4. The method for measuring thickness by using pulsed infrared thermal wave technology according to claim 1, wherein the pulsed heating device is a high-energy flash lamp.