Strain measurement device, a solid rocket motor including same, and related methods
A strain measurement device includes a reference material, and a displacement sensor configured to detect relative changes in distance between the sensor and the reference material. At least one of the displacement sensor and the reference material is coupled with a pre-cured elastomeric material. The displacement sensor generates a data signal to a processor that is configured to determine a strain of another elastomeric material based at least in part on the data signal received from the sensor. A displacement sensor and a reference material may be positioned within an elastomeric material within a casing of a solid rocket motor for determining strain experienced by the elastomeric material, such as the propellant of the solid rocket motor. A method includes installing a sensor of an elastomeric material. Another method includes determining strain of an elastomeric material of a solid rocket motor.
1. An apparatus, comprising:
a pre-cured elastomeric material;
another elastomeric material; and
a strain measurement device, comprising:
a reference material;
a displacement sensor, wherein at least one of the displacement sensor and the reference material is coupled with the pre-cured elastomeric material, and the another elastomeric material is formed around the pre-cured elastomeric material such that the displacement sensor and the reference material have an initial distance therebetween, the displacement sensor configured to generate a data signal responsive to detecting changes in distance between the displacement sensor and the reference material; and
a processor operably coupled with the displacement sensor, the processor configured to receive the data signal and determine a strain of the another elastomeric material based, at least in part, on the data signal received from the displacement sensor.
2. The apparatus of claim 1 , wherein the displacement sensor is a Hall-effect sensor, and the reference material is a magnet.
3. The apparatus of claim 1 , wherein the displacement sensor is an Eddy-current sensor, and the reference material is selected from the group consisting of a metal and a metal alloy.
4. The apparatus of claim 1 , wherein the displacement sensor and the reference material are coupled to opposing ends of the pre-cured elastomeric material.
5. The apparatus of claim 4 , wherein the displacement sensor and the reference material are at least partially embedded within the pre-cured elastomeric material.
6. The apparatus of claim 1 , further comprising a plurality of displacement sensors coupled to the pre-cured elastomeric material.
7. The apparatus of claim 6 , wherein the displacement sensors of the plurality are oriented relative to the reference material to determine strain of the another elastomeric material along a plurality of different axes.
8. A method for installing a strain measurement device in an elastomeric material, the method comprising:
forming a strain measurement device by coupling a displacement sensor and a reference material to a pre-cured elastomeric material at an initial distance, the displacement sensor configured to generate a data signal in response to detecting changes in distance between the displacement sensor and the reference material from the initial distance;
forming a second elastomeric material around the pre-cured elastomeric material after the displacement sensor and the reference material have been coupled to the pre-cured elastomeric material; and
operably coupling a processor with the displacement sensor, the processor configured to determine a strain of the second elastomeric material based, at least in part, on the data signal received from the displacement sensor.
9. The method of claim 8 , wherein forming the second elastomeric material around the pre-cured elastomeric material includes:
positioning the pre-cured elastomeric material within a cavity of a solid rocket motor; and
casting a propellant within the cavity.
10. The method of claim 9 , further comprising forming the pre-cured elastomeric material from propellant.
11. The method of claim 8 , wherein coupling the displacement sensor and the reference material to the pre-cured elastomeric material includes coupling the displacement sensor and the reference material after curing the pre-cured elastomeric material.
12. The method of claim 8 , wherein coupling the displacement sensor and the reference material to the pre-cured elastomeric material includes:
introducing a viscous elastomeric material around at least a portion of the displacement sensor and the reference material; and
curing the elastomeric material to form the pre-cured elastomeric material.
13. The method of claim 12 , wherein introducing the viscous elastomeric material around at least a portion of the displacement sensor and the reference material includes:
positioning the displacement sensor and the reference material within a mold cavity of a mold having a shape that is complementary to a desired shape for the pre-cured elastomeric material; and
introducing the viscous elastomeric material into the mold cavity.
14. The method of claim 13 , further comprising maintaining the displacement sensor and the reference material in position with a plurality of magnets positioned near an outer surface of the mold, corresponding to opposite positions of the displacement sensor and the reference material.
15. The apparatus of claim 1 , further comprising a solid rocket motor comprising:
a casing defining a cavity configured to house a propellant; and
a liner coupled with the casing and configured to couple with the propellant, wherein at least one of the displacement sensor and the reference material is positioned within the casing, wherein the displacement sensor and the reference material are initially positioned at a predefined relative distance, and wherein the data signal represents a relative distance between the displacement sensor and the reference material.
16. The apparatus of claim 15 , wherein at least one of the displacement sensor and the reference material is positioned within the liner.
17. The apparatus of claim 15 , further comprising the propellant cast within the cavity.
18. The apparatus of claim 17 , wherein at least one of the displacement sensor and the reference material is positioned within the propellant.
19. The apparatus of claim 18 , wherein the liner comprises a flap and a flap bulb proximate a frontal portion of the casing, and wherein at least one of the displacement sensor and the reference material is positioned within the propellant proximate the flap bulb.
20. The apparatus of claim 18 , wherein both the displacement sensor and the reference material are coupled to the pre-cured elastomeric material that is embedded within the propellant.
21. The apparatus of claim 20 , wherein the pre-cured elastomeric material comprises a substantially similar chemical composition as the propellant.
22. The apparatus of claim 15 , wherein the other of the displacement sensor and the reference material is positioned at a fixed location of an outer surface of the casing.
23. The apparatus of claim 15 , further comprising a plurality of displacement sensors configured to generate separate data signals, wherein the processor is configured to determine the strain experienced by the another elastomeric material along a plurality of directions responsive to the separate data signals.
24. The apparatus of claim 15 , wherein the displacement sensors of the plurality are at least substantially parallel in their axial directions, and wherein the processor is configured to determine the strain by triangulation of the separate data signals.