System for monitoring surface stress and other conditions in structures

• US 5,814,816 A
• Filed: 08/27/1996
• Issued: 09/29/1998
• Est. Priority Date: 08/27/1996
• Status: Expired due to Term

• Current Assignee: United States Department Of Health And Human Services (Government of the United States of America)
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Nadolink, Richard H.
• Primary Examiner(s): Hannaher, Constantine
• Application Number:
  US08/716,665
• Time in Patent Office: 763 Days
• Field of Search: 250/341.4, 250/341.1, 250/340, 250/341.8, 356/35.5
• US Class Current: 250/341.4
• CPC Class Codes: G01L 1/248 using infrared G01L1/241, G01L1/242 take precedence
• CPC Class Codes: G01L 5/0047 measuring forces due to residual stresses

Abstract

A system for monitoring a structure is built on a printed circuit board (PCB) mounted at the surface of the structure. A piece of single crystal silicon is mounted on the PCB and is in contact with the structure. An infrared source directly illuminates the silicon while an infrared detector is focused thereon to monitor isochromatic fringe patterns projected from the silicon as a direct indication of stress at the surface. One or more other sensors are coupled to the PCB for collecting data indicative of other physical conditions experienced by the structure. A wireless system communicates with each such sensor so that the data so collected can be received at a remote location.

Claims

1. A system for monitoring a structure, comprising:

a printed circuit board mounted at the surface of the structure;

a piece of single crystal silicon mounted on said printed circuit board, said piece of single crystal silicon being in contact with the structure;

an infrared source for directly illuminating said piece of single crystal silicon with radiation having a wavelength in the range of 800-1100 nanometers;

an infrared detector focused on said piece of single crystal silicon for monitoring isochromatic fringe patterns projected from said piece of single crystal silicon as a result of illuminating said piece of single crystal silicon with said radiation, wherein said isochromatic fringe patterns are a direct indication of an amount of stress at the surface of the structure;

at least one sensor coupled to said printed circuit board, each said at least one sensor being capable of collecting data indicative of a physical condition experienced by the structure; and

monitoring means in communication with each said at least one sensor for receiving said data.

2. A system as in claim 1 further comprising a mirror mounted between said piece of single crystal silicon and said printed circuit board.

3. A system as in claim 1 wherein said piece of single crystal silicon is flush with a surface of the structure.

4. A system as in claim 1 wherein said infrared source illuminates said piece of single crystal silicon from a first angle with respect to a line normal to said piece of single crystal silicon.

5. A system as in claim 4 wherein said infrared detector is focused on said piece of single crystal silicon from a second angle with respect to said line, said first angle and said second angle being equal in magnitude.

6. A system as in claim 5 wherein said infrared source and said infrared detector lie on opposing sides of said line in a plane normal to said piece of single crystal silicon.

7. A system as in claim 1 wherein said monitoring means comprises:

a transmitter mounted on said printed circuit board and in communication with each said at least one sensor, said transmitter transmitting said data; and

a receiver remotely located with respect to the structure for receiving said data from said transmitter.

8. A system as in claim 7 wherein said transmitter is of the type which communicates employing a modulated infrared beam.

9. A system as in claim 1 further comprising a power supply mounted on said printed circuit board and coupled to each said at least one sensor for supplying power thereto.

10. A system as in claim 9 wherein said power supply is solar powered.

11. A system for monitoring a structure exposed to a fluid flow, comprising:

a printed circuit board embedded in the structure;

a mirror-backed single crystal silicon semiconductor wafer mounted on said printed circuit board such that said wafer is in contact with the structure and flush with the surface of the structure;

an infrared source for directly illuminating said wafer through the fluid flow with radiation having a wavelength in the range of 800-1100 nanometers;

an infrared detector focused through the fluid flow on said wafer for monitoring isochromatic fringe patterns projected from said wafer as a result of illuminating said wafer with said radiation, wherein said isochromatic fringe patterns are a direct indication of an amount of stress at the surface of the structure;

at least one sensor coupled to said printed circuit board, each said at least one sensor being capable of collecting data indicative of a physical condition experienced by the structure; and

monitoring means in communication with each said at least one sensor for receiving said data.

12. A system as in claim 11 wherein said infrared source illuminates said wafer from a first angle with respect to a line normal to said wafer.

13. A system as in claim 12 wherein said infrared detector is focused on said wafer from a second angle with respect to said line, said first angle and said second angle being equal in magnitude.

14. A system as in claim 13 wherein said infrared source and said infrared detector lie on opposing sides of said line in a plane normal to said wafer.

15. A system as in claim 11 wherein said monitoring means comprises:

a transmitter mounted on said printed circuit board and in communication with each said at least one sensor, said transmitter transmitting said data through the fluid flow; and

a receiver remotely located with respect to the structure for receiving said data from said transmitter.

16. A system as in claim 15 wherein said transmitter is of the type which communicates employing a modulated infrared beam.

17. A system as in claim 11 further comprising a power supply mounted on said printed circuit board and coupled to each said at least one sensor for supplying power thereto.

18. A system as in claim 17 wherein said power supply is solar powered.