Method and apparatus for the portable identification of material thickness and defects using spatially controlled heat application

US6000844A · kind A · utility

Assignee

• The United States of America as represented by the Administrator of the National Aeronautics and Space Administration · US

Inventors

• K. Elliott Cramer · Newport News, US
• William P. Winfree · Williamsburg, US

Key dates

• Filing date: Mar 4, 1997
• Grant date: Dec 14, 1999
• Expiry date: Mar 4, 2017

Classification

• Technology area (CPC G): Physics
• CPC primary: G01N25/72
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

A method and a portable apparatus for the nondestructive identification of defects in structures. The apparatus comprises a heat source (20) and a thermal imager (30) that move at a constant speed past a test surface (10) of a structure. The thermal imager (30) is off set at a predetermined distance from the heat source (10). The heat source (10) induces a constant surface temperature. The imager (20) follows the heat source (10) and produces a video image of the thermal characteristics of the test surface. Material defects produce deviations from the constant surface temperature that move at the inverse of the constant speed. Thermal noise produces deviations that move at random speed. Computer averaging of the digitized thermal image data with respect to the constant speed minimizes noise and improves the signal of valid defects. The motion of thermographic equipment coupled with the high signal to noise ratio render it suitable for portable, on site analysis.