Relaxation modulus sensor, structure incorporating same, and method for use of same

• US 7,581,450 B2
• Filed: 10/31/2006
• Issued: 09/01/2009
• Est. Priority Date: 10/31/2006
• Status: Active Grant

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: Alliant Techsystems Incorporated (Northrop Grumman Corporation)
• Inventors: Graham, Robert, Pearson, Lee H., Johnson, Mont A., Shipley, John L.
• Primary Examiner(s): Caputo; Lisa M
• Assistant Examiner(s): ROY, PUNAM P
• Application Number:
  US11/555,029
• Publication Number:
  US 20080110274A1
• Time in Patent Office: 1,036 Days
• Field of Search: 737/68, 737/75, 738/03, 738/02
• US Class Current: 73/768
• CPC Class Codes: G01B 7/16 for measuring the deformation in a solid, e.g. by resistance strain gauge

Abstract

A sensor for measuring material properties such as the relaxation modulus of a material in situ and a method of measuring material properties of a material are disclosed. The sensor may be substantially embedded in the material, and includes a deformable driver. When actuated, the deformable driver may create a stress in the adjacent material. The movement or deformation of the driver may be measured with a sensing device, for example a strain gage mounted on a surface thereof. The stress in the adjacent material may be measured with a second sensing device, for example a pressure sensor. The measured movement and stress over a predetermined period of time may he used to determine the relaxation modulus of the material.

Claims

1. A sensor for measuring relaxation modulus in a test material, comprising:

a frame having an opening therethrough embedded in the test material;

a driver mounted within the opening of the frame embedded in the test material, the driver comprising one of an electric motor, an electric solenoid, a hydraulic solenoid, a hydraulic cylinder, and a gas operated cylinder;

a first sensing device in communication with the driver; and

a second sensing device disposed within a gap between the driver and the frame embedded in the test material.

2. The sensor of claim 1, wherein an edge of the driver is attached to an inside edge of the frame.

3. The sensor of claim 1, wherein the first sensing device is configured to measure a stimulus of the driver.

4. The sensor of claim 1, wherein the first sensing device comprises a strain gage.

5. The sensor of claim 4, wherein the strain gage comprises a foil type gage or a thin film strain gage.

6. A sensor for measuring relaxation modulus in a test material, comprising:

a frame having an opening therethrough;

a driver mounted within the opening of the frame, wherein the driver comprises a smart material;

a first sensing device in communication with the driver; and

a second sensing device disposed within a gap between the driver and the frame.

7. The sensor of claim 6, wherein the smart material is one of a shape memory alloy, an electrostrictive material and a magnetostrictive material.

8. The sensor of claim 6, further comprising a second driver mounted within the opening of the frame.

9. The sensor of claim 8, wherein the second sensing device is disposed between the driver and the second driver.

10. A sensor for measuring relaxation modulus in a test material, comprising:

a frame having an opening therethrough;

a driver mounted within the opening of the frame, the driver comprising a plurality of twisted shape metal alloy wires;

a first sensing device in communication with the driver; and

a second sensing device disposed within a gap between the driver and the frame.

11. A sensor for measuring relaxation modulus in a test material, comprising:

a frame having an opening therethrough;

a driver mounted within the opening of the frame, the driver comprising one of an electric motor, an electric solenoid, a hydraulic solenoid, a hydraulic cylinder, and a gas operated cylinder;

a first sensing device in communication with the driver; and

a second sensing device disposed within a gap between the driver and the frame, the second sensing device comprising a pressure sensor.

12. The sensor of claim 11, wherein the pressure sensor comprises a fiber optic pressure sensor.

13. A method for measuring relaxation modulus in a test material comprising:

providing a sensor comprising at least one driver including a movable element;

embedding the sensor in the test material;

actuating the at least one driver including the movable element with as a stimulus to create a stress in the test material, wherein creating the stress in the material comprises applying a force in one of tension, compression, torsion, and a combination thereof to the test material; and

sensing the stress in the test material.

14. The method of claim 13, wherein the stimulus comprises electricity or hydraulic pressure.

15. The method of claim 13, wherein sensing the stress in the test material comprises sensing the stress over a predetermined period of time.

16. The method of claim 13, wherein sensing the stress in the test material comprises measuring the pressure in the test material with a pressure sensor.

17. A method for measuring relaxation modulus in a test material comprising:

providing a sensor comprising at least one deformable driver;

embedding the sensor in the test material;

actuating the at least one deformable driver with a stimulus to create a stress in the test material,

wherein creating the stress in the test material comprises applying a force in one of tension, compression and torsion to the test material;

and

sensing the stress in the test material.

18. The method of claim 17, further comprising sensing a deformation of the at least one deformable driver with a strain gage thereon.

19. The method of claim 17, wherein providing the sensor comprising the at least one deformable driver comprises forming a deformable driver of a smart material.

20. The method of claim 17, wherein providing the sensor comprises providing a frame having an opening therethrough, and disposing the at least one deformable driver within the opening.

21. The method of claim 17, wherein embedding the sensor in the test material comprises embedding the sensor with the at least one deformable driver in a first deformed position, and actuating the at least one deformable driver comprises deforming the at least one deformable driver to a second, different deformed position.

22. The method of claim 17, wherein providing the sensor comprising the least one deformable driver comprises providing the sensor comprising two deformable drivers.

23. The method of claim 22, wherein actuating the at least one deformable driver comprises actuating the two deformable drivers.

24. A sensor for measuring relaxation modulus in a test material, comprising:

a frame having an opening therethrough;

a driver located in the frame comprising a movable element embedded in the test material for deforming the test material, the driver comprising one of an electric motor, an electric solenoid, a hydraulic solenoid, a hydraulic cylinder, a gas operated cylinder, and a plurality of twisted shape metal alloy wires;

a first sensing device in communication with the test material embedded in the test material; and

a second sensing device embedded in the test material.

25. The sensor of claim 24, wherein the first sensing device comprises a strain gage.

26. The sensor of claim 24, wherein the second sensing device comprises a pressure sensor.

27. A rocket motor, comprising:

a propellant;

a liner at least partially surrounding the propellant; and

a sensor substantially embedded in the liner, the sensor comprising;

a frame having an opening therethrough;

a driver mounted within the opening of the frame;

a first sensing device in communication with the driver; and

a second sensing device disposed within a gap formed between the driver and the frame.