Optical linear strain gage

• US 20060173638A1
• Filed: 02/03/2005
• Published: 08/03/2006
• Est. Priority Date: 02/03/2005
• Status: Active Grant

• Current Assignee: GE Infrastructure Technology, LLC (General Electric Company)
• Original Assignee: Direct Measurements, Inc.
• Inventors: Hovis, Gregory, Vachon, Reginald I.
• Granted Patent: US 7,477,995 B2
• Time in Patent Office: Days
• US Class Current: 702/42
• CPC Class Codes: G01D 5/34707 Scales; Discs, e.g. fixation, fabrication, compensation
• CPC Class Codes: G01L 1/24 by measuring variations of optical properties of material when it is stressed, e.g. by photoelastic stress analysis using infrared, visible light, ultraviolet
• CPC Class Codes: G01M 11/08 Testing mechanical properties G01M11/005 takes precedence
• CPC Class Codes: G01M 5/0025 of elongated objects, e.g. pipes, masts, towers or railways G01M5/0058 takes precedence
• CPC Class Codes: G01M 5/0033 by determining damage, crack or wear
• CPC Class Codes: G01M 5/0091 by using electromagnetic excitation or detection

Abstract

An optical linear strain gage includes a target, a sensor, and a computer, wherein the target contains a gage length defined by end points. The target can be a one-dimensional barcode, the gage length defined between, and perpendicular to, two chosen parallel lines of the barcode. The target, including a gage length, is associated with an object such that deformation of the gage length and deformation of the object are the same; target can emit or reflect a detectable physical quantity. The sensor is compatible with and pre-processes the physical quantity from the target and provides data to the computer. The computer analyzes the data output and calculates the strain directly on the body based on the pre-processed and analyzed data. Measuring strain on an object using the strain gage includes identifying the changes in the gage length as a function of time and load applied and calculating strain.

Claims

1. An optical strain gage comprising:

a target containing a pair of end points or a pair of end lines, and a gage length defined by the end points or end lines, the target being adapted for association with a body for which at least one of strain and fatigue damage 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;

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

means for calculating at least one of the strain and the fatigue damage directly on the body based on the pre-processed and analyzed data.

2. The optical strain gage of claim 1, wherein the gage length is defined by a pair of end points.

3. The optical strain gage of claim 1, wherein the gage length is defined by a pair of end lines, the gage length being perpendicular to the end lines.

4. The optical strain gage of claim 1, wherein the target comprises a set of parallel lines, and wherein two of the parallel lines are chosen as the end lines, the gage length being perpendicular to the end lines.

5. The optical strain gage of claim 1, wherein the target comprises a set of parallel lines in the form of a one-dimensional barcode, and wherein two of the parallel lines are chosen as the end lines, the gage length being perpendicular to the end lines.

6. The optical strain gage of claim 5, wherein the one-dimensional barcode is based on the Code 39 barcode standard, and includes start and stop characters and a sequential string of a plurality of intermediate characters that hold the actual coded information, each character being defined by a total of nine bars and spaces.

7. The optical strain gage of claim 6, wherein the start and stop character of the one-dimensional barcode is the character “

*”

(asterisk), the ratio of wide bars to narrow bars is 2;

1, the one-dimensional barcode includes a perimeter incorporating a conventional barcode quiet zone.

8. The optical strain gage of claim 6, wherein the one-dimensional barcode includes human-readable encoded information not required by the Code 39 barcode standard.

9. The optical strain gage of claim 5, wherein the one-dimensional barcode is based on one of the Code 39, CODABAR, Code 128, Code 25, Code 93, EAN 128, EAN 13, EAN 8, MSI, JAN 13, JAN 8, Plessey, Telepen, UPCA, UPC C, Data Matrix, PDF 417, MICRO PDF 417, RSS Expanded, and RSS Limited barcode standards.

10. An optical strain gage comprising:

a target comprising a one-dimensional barcode, the target being adapted for association with a body for which at least one of strain and fatigue damage 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;

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

means for calculating at least one of the strain and the fatigue damage directly on the body based on the pre-processed and analyzed data.

11. The optical strain gage of claim 10, wherein two of the parallel lines of the barcode are chosen as the end lines defining a gage length perpendicular to the end lines.

12. The optical strain gage of claim 10, wherein the one-dimensional barcode is based on one of the Code 39, CODABAR, Code 128, Code 25, Code 93, EAN 128, EAN 13, EAN 8, MSI, JAN 13, JAN 8, Plessey, Telepen, UPCA, UPC C, Data Matrix, PDF 417, MICRO PDF 417, RSS Expanded, and RSS Limited barcode standards.

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

associating a gage length with an object in such a way that deformation of the gage length and deformation under load of the object bear a one-to-one relationship;

identifying the changes in the gage length, as a function of time and change in the load applied to the object; and

translating the changes in the gage length into at least one of strain and fatigue damage.