Compressed symbology strain gage

• US 6,934,013 B2
• Filed: 08/20/2002
• Issued: 08/23/2005
• Est. Priority Date: 08/20/2002
• Status: Expired due to Term

• Current Assignee: SMA Incorporated, University of South Carolina
• Original Assignee: University of South Carolina
• Inventors: Ranson, William, Vachon, Reginald
• Primary Examiner(s): Toatley, Jr., Gregory J.
• Assistant Examiner(s): LAUCHMAN, LAYLA G
• Application Number:
  US10/223,680
• Publication Number:
  US 20040036853A1
• Time in Patent Office: 1,099 Days
• Field of Search: 356 32- 355, 356/11, 737/60, 737/94, 737/99, 738/00, 73/11, 702/42
• US Class Current: 356/32
• CPC Class Codes: G01B 11/16 for measuring the deformation in a solid, e.g. optical strain gauge
• CPC Class Codes: G01N 2203/0647 Image analysis

Abstract

A compressed symbology strain gage includes a target in the form of a symbolic strain rosette (“SSR”), the target being associated with a body for which strain is to be measured and being adapted to emit a detectable physical quantity; a sensor compatible with and adapted to pre-process the detectable physical quantity emitted by the target and output data representing the physical quantity adapted to receive signals from the target and provide output signals based thereon; a computer program or programs for analyzing the signals data output by the sensor to define the SSR; and for calculating the strain directly on the body based on the pre-processed and analyzed data. The SSR can be defined either a priori by manufacture or a posteriori by identification. A method of measuring strain on an object using the compressed symbology strain gage includes the steps of associating a SSR with an object in such a way that deformation of the SSR and deformation under load of the object bear a one-to-one relationship; identifying the changes in the SSR as a function of time and change in the load applied to the object; and translating the changes in the SSR into strain.

Claims

1. A compressed symbology strain gage comprising:

a target comprising a symbolic strain rosette in the form of a compressed symbol that is defined in terms of the end points of three intersecting line segments that define a strain rosette, the target being associated with a body for which at least one of strain and fatigue damage is to be measured and emitting a detectable physical quantity;

sensor means for pre-processing the detectable physical quantity emitted by the target and output data representing the physical quantity, the sensor means being compatible with the detectable physical quantity;

means for analyzing the data output by the sensor means to define the symbolic strain rosette; and

means for measuring the strain on the body directly based on the pre-processed and analyzed data.

5. The compressed symbology strain gage of claim 1, wherein the symbolic strain rosette is defined a priori by manufacture.

6. The compressed symbology strain gage of claim 5, wherein the symbolic strain rosette a strain rosette contained in a two dimensional bar code.

7. The compressed symbology strain gage of claim 6, wherein the two dimensional bar code is a Data Matrix symbol.

8. The compressed symbology strain gage of claim 1, wherein the target is identified in a pre-existing pattern that defines the symbolic strain rosette.

9. The compressed symbology strain gage of claim 1, further comprising means for utilizing the strain measurement to provide information on at least one of fatigue damage and strain hysteresis for materials of known and unknown mechanical properties.

10. The compressed symbology strain gage of claim 1, further comprising means for utilizing the strain measurement to provide advance notice of an approaching failure point for materials of known mechanical properties.

11. The compressed symbology strain gage of claim 1, further comprising means for utilizing the strain measurement to extrapolate a failure point for a material of unknown mechanical properties.

12. The compressed symbology strain gage of claim 1, further comprising means for utilizing the strain measurement based on collected damage accumulation data.

2. A method of measuring at least one of strain and fatigue damage on an object directly, comprising the steps of:

associating a symbolic strain rosette with an object in such a way that deformation of the symbolic strain rosette and deformation under load of the object bear a one-to-one relationship, wherein the symbolic strain rosette is in the form of a compressed symbol that is defined in terms of the end points of three intersecting line segments that define a strain rosette;

identifying the changes in the symbolic strain rosette as a function of time and change in the load applied to the object; and

translating the changes in the symbolic strain rosette into a direct measurement of strain.

3. The method of claim 2, wherein the symbolic strain rosette is defined a priori by manufacture and the associating step comprises applying the symbolic strain rosette to the object.

4. The method of claim 2, wherein the associating step comprises identifying the symbolic strain rosette a priori.

13. The method of claim 2, further comprising the step of utilizing the strain measurement to provide information on at least one of fatigue damage and strain hysteresis for materials of known and unknown mechanical properties.

14. The method of claim 2, further comprising the step of utilizing the strain measurement to provide advance notice of an approaching failure point for materials of known mechanical properties.

15. The method of claim 2, further comprising the step of utilizing the strain measurement to extrapolate a failure point for a material of unknown mechanical properties.

16. The method of claim 2, further comprising the step of utilizing the strain measurement based on collected damage accumulation data.