EP1153264A1 - Jauges de contrainte actives pour evaluation des degats d'origine sismique - Google Patents

Jauges de contrainte actives pour evaluation des degats d'origine sismique

Info

Publication number
EP1153264A1
EP1153264A1 EP00906994A EP00906994A EP1153264A1 EP 1153264 A1 EP1153264 A1 EP 1153264A1 EP 00906994 A EP00906994 A EP 00906994A EP 00906994 A EP00906994 A EP 00906994A EP 1153264 A1 EP1153264 A1 EP 1153264A1
Authority
EP
European Patent Office
Prior art keywords
housing
optical waveguide
optical
waveguide sensor
sensor according
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP00906994A
Other languages
German (de)
English (en)
Inventor
Otto J. Gregory
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Rhode Island Board of Education
Original Assignee
Rhode Island Board of Education
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Rhode Island Board of Education filed Critical Rhode Island Board of Education
Publication of EP1153264A1 publication Critical patent/EP1153264A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/16—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge
    • G01B11/18—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge using photoelastic elements

Definitions

  • This invention relates generally to optical waveguide sensors and more specifically to temperature insensitive optical waveguide sensors which can monitor strain in excess of 2000 ⁇ .
  • Optical fiber based sensors have been applied to many of applications including displacement (position), temperature, pressure, sound, and strain.
  • optical sensor data collection can generally be divided into two basic categories: phase- modulated and intensity-modulated.
  • Intensity modulated sensors are usually associated with displacement or some other physical perturbation that interacts with the sensor. The perturbation causes a change in received light intensity and the intensity is related to the monitored parameter.
  • Phase-modulated sensors compare the phase of light in a sensing path to the phase in a reference. Phase difference can be measured with extreme sensitivity, but frequently requires sophisticated electronics for signal processing.
  • phase modulated sensors have been used to measure temperature, thus they need to be calibrated for temperature when used in a strain application.
  • Application of this type of optical sensor includes in situ monitoring of thin film deposition thickness.
  • Phase- modulated sensors are generally more accurate than intensity-modulated sensors. However, they are usually more expensive and extremely sensitive to environmental effects, such as temperature.
  • the optical waveguide sensor of the invention overcomes the drawbacks of the aforementioned prior art strain gages Brief Summary of the Invention
  • the invention comprises an optical waveguide sensor, which comprises a housing having an interior and exterior surface. At least two layers are applied to the exterior surface of the housing.
  • the first layer comprises a low refractive index material and the second layer comprises a highly reflective material.
  • First and second optical fibers are in communication with the housing. A beam of light of known intensity is passed through the first optical fiber through the housing and received by the second optical fiber. The beam is attenuated according to how many 'bounces' or reflections it experiences as it passes through the housing which is determined by the conformation of the housing. The conformation of the housing is directly related to the bending strain that the housing experiences.
  • the optical waveguide sensor comprises a flexible, hollow, glass tube with an absorptive layer of polyimide deposited on the outside followed by the deposition of a layer of high optical reflection, such as aluminum.
  • the parameter that is monitored is the intensity of the exiting light after the beam has passed through the sensor tube.
  • the beam is attenuated according to how many 'bounces' or reflections it experiences which in turn is a function of the radius of curvature of the hollow tube sensor.
  • the radius of the curvature of the tube is directly related to the bending strain that the tube experiences and so applied strain can be 5 inferred by monitoring the exit light beam intensity.
  • the stability, ruggedness and simplicity of the present invention facilitate its use for remote sensing applications. Since optical fiber technology can be used to both send and receive the light signals, instantaneous strain can be monitored and relayed immediately or stored for later retrieval via a transmission link.
  • the optical waveguide of the invention has a gage factor of about 500 for strains in excess of 2000 ⁇ .
  • the housing is comprised of a hollow, glass wave-guide of dimensions of about 0.5 mm ID x 0.8 mm OD x 100 mm long.
  • the geometry of the housing of the optical waveguide sensor is compatible with
  • the housing is a glass tube having a small diameter.
  • the small diameter glass tubes act as the substrate for multiple thin film layers
  • the optical wave guide sensor of the invention which comprises a glass tube coated with the thin film layers responds to bending strain by attenuating the optical intensity of the excitation signal and exhibits little or no hysteresis.
  • optical waveguide sensors of the invention have a large gage factor of about
  • the sensors are temperature insensitive, i.e. the sensors do not respond to temperature changes over the normal range of outdoor temperatures (-20 to 50 °C), inexpensive to manufacture, not affected by electromagnetic fields, chemically inert to environmental conditions such as moisture and acid rain thereby making it possible to embed the sensors in a concrete structure with no fear of chemical reaction with the concrete and
  • Fig. 1 is a schematic of an embodiment of the optical waveguide sensor of the invention.
  • Fig. 2 is a schematic of the layout used for testing an embodiment of the optical waveguide sensor.
  • Fig. 3 is a graph illustrating the strain response of optical waveguide sensors comprised of uncoated, aluminum coated, polyimide coated, and polyimide plus aluminum coated capillaries.
  • Fig. 4 is a graph illustrating the strain response of an optical waveguide sensor comprised of an ITO and aluminum coated capillary.
  • Fig. 5 is a table of gage factors for the various types of sensors shown in Figs. 3 and 4. Description of the Preferred Embodiment s)
  • a housing 12 has an interior surface 14 and an exterior surface 16.
  • the exterior surface 16 is comprised of at least one layer of low index of refraction material 24 and at least one layer of highly reflective material 26.
  • the housing 12 , and layers 28 and30 have very small coefficients of expansion, e.g. 9> ⁇ 10 "6 in/in °C.
  • the basic dimensions of the sensor 10 in the direction of strain do not change over the temperature ranges typically encountered environmentally.
  • the housing 12 is in communication with a first optical fiber 28 and a second optical fiber 30.
  • Means for detecting (not shown) the change in the intensity of light when light is passed through the housing 12, reflected and refracted within the housing 12 and received by the second optical fiber 30, is in communication with the second optical fiber 30.
  • the low index of refraction material of the first layer 24 is polyimide and the highly reflective material of the second layer 26 is aluminum.
  • the invention comprises a robust waveguide strain sensor capable of monitoring strain of up to about at least 2000 ⁇ .
  • the active strain elements for the sensors comprise hollow glass tubes onto which thin film, optically active materials are deposited.
  • 10cm long, hollow glass wave guides were obtained from commercial suppliers.
  • the tube type sizes evaluated were; plain glass tubes, 5mm ID with 0.20mm wall thickness (Fisher Scientific, Pittsburgh PA) and -16 - 35 ⁇ m polyimide coated glass tubes with wall thickness, 0.09mm, 0.175mm, 0.1075mm and tube inside diameters of 0.32mm, 0.45mm, and 0.53mm respectively (Alltech Company, Deerfield, NY).
  • the tubes were cleaned with a commercial ammonia based glass cleaner and then with acetone, methanol and deionized water rinses followed by blow drying in filtered 5 nitrogen gas. Subsequent to cleaning they were placed in an ozone plasma chamber for two hours to remove any residual organic surface contaminants.
  • Three different thin film coatings were evaluated for the optically sensitive layer; polyimide, indium tin oxide and zinc oxide in thicknesses of 0.1 to 40 ⁇ m.
  • Other coatings believed suitable for purposes of the invention include silicon and germanium.
  • Polyimide coatings were 'standard' films provided by gas chromatography supply houses for column capillaries. The latter two materials were deposited by RF reactive sputtering. After applying the active coating, a reflective outer layer of aluminum ( ⁇ 0.5 ⁇ m) was deposited, also by reactive sputtering. Other reflective layers believed to be suitable include silver, platinum, and palladium.
  • the ends of the source and detector fibers 28 and 30 respectively were prepared, using standard industry techniques, to produce a flat surface normal to the fiber and sensor axis.
  • the main components of the experimental apparatus were 1) a HeNe laser light source 40 emitting light energy in a range of 632 to 633 nm, 2) a
  • the laser light was directed to the reference diode detector 44 via a beam splitter 52 in the optical path.
  • the reference signal was electronically divided into the sensor output signal to further reduce random noise.
  • Commercial multimode optical fibers were used to bring the light source to the sensor input and carry the light exiting the sensor to the output detector. Strain was induced using the four point bending apparatus ASTM C-
  • Equation (1) gives a measurement of strain based on the geometry of the four- point bending device.
  • the quantity ⁇ can be measured directly or can be determined accurately by constructing a calibration curve of ⁇ versus inner pin displacement. Over the range of bending necessary to attain 2000 ⁇ , ⁇ is linear with displacement and so can be directly inferred from the linear displacement of the inner pins.
  • the smart optical strain sensor employs a hollow glass waveguide support with the active sensing material located between the glass outer wall and the reflective
  • gage factor (aluminum) over coating.
  • gage factor or response to strain was calculated as follows:
  • ⁇ I is the change in intensity as measured by the light detector diode at two strain levels
  • ⁇ is the change in strain
  • I 0 is the intensity in the unstrained condition. Since the intensity versus strain response was found to be essentially linear over the strain ranges tested, the gage factor was calculated by dividing the slope of the I versus ⁇ curve by the I-axis intercept of the straight line that best fit the data. In practice the parameter measured is the output voltage of the amplifier used to measure the response, to intensity changes, of the sensor output detector diodes. That voltage was divided by the output of the reference diode amplifier and the ratio of the two voltages plotted as a function of strain. When an ITO layer is added to the sensor construction, the gage factor is reduced but the range increases significantly.
  • the particular structure, used for the response curve in Figure 4 was formed by sputtering 0.9 ⁇ m of ITO followed by 0.5 ⁇ m of aluminum onto the polyimide coated 0.53mmm ID tubes.
  • the gage factor for that sensor configuration was 410.
  • the change in signal when going from unstrained to 2000 ⁇ was extrapolated to be 90% (reduction). This is in contrast to the typical 50% signal reduction observed over the same strain range for the various specimens without ITO active layer (Figure 3).
  • the associated gage factors for the configurations presented in Figures 3 and 4 are summarized in the table of Figure 5.
  • Cyclic straining of the sensor was done to test the reproducibility of the optical sensors. In four cycles from zero to maximum strain, for identical thin film structures fabricated on tubes of the same ID, the strain gages had reproducibility better than 1%.
  • the optical strain waveguide sensors are based on the loss of light that occurs when the laser beam hits the inner wall of the waveguide, traverses the wall (and any coatings thereon), reflects from the mirrored outer layer (aluminum) and traverses the coatings and wall of the waveguide once more.
  • aluminum mirrored outer layer
  • the optical strain waveguide sensors occur at each subsequent interface as well with an reflection/transmission ratio that depends, according to Fresnel and Snell Laws, upon indices of refraction of each material in the stack.
  • d is the outer diameter of the tube
  • ⁇ is the strain
  • L is the gage length
  • a sensor which has an ID of 0.53 ⁇ 0.012 mm a wall thickness of 0.085+0.012mm and a polyimide layer 24 ⁇ 4 ⁇ m thick, is a convenient match for the multi-mode fibers that are currently used. With this particular capillary, strain in excess of 5000 ⁇ can easily be attained. Smaller, thinner walled polyimide coated capillary tubes are available should measurements at even higher strains be required.
  • the addition of absorptive layers and the tailoring of their thickness can be used to expand the dynamic range of the optical sensors design and end use, tailored for a specific dynamic range. Ideally the maximum strain should result in a reduction of intensity to a few percent of the initial value.
  • the waveguide sensor of the invention is a robust, chemically and thermally stable waveguide. The sensor can survive strain in excess of 2000 ⁇ and is readily incorporated into optical fiber data collection systems. The optical properties of the active coatings on the sensor can be optimized to give the maximum dynamic range for a specific maximum strain criterion. Polyimide-coated capillaries can be strained at least to 5000 ⁇ and are supplied with better tolerance control.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Length Measuring Devices By Optical Means (AREA)
  • Optical Transform (AREA)
  • Testing Resistance To Weather, Investigating Materials By Mechanical Methods (AREA)
  • Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)

Abstract

Cette invention concerne un capteur à guide d'onde optique (10) comprenant un boîtier (12) qui présente une surface extérieure (16) et une surface intérieure (14). La surface extérieure (16) est recouverte d'au moins deux couches, la première renfermant un matériau à faible indice de réfraction (24), la seconde un matériau fortement réfléchissant (26). Le boîtier est en communication avec la première (28) et la seconde (30) fibre optique.
EP00906994A 1999-01-26 2000-01-25 Jauges de contrainte actives pour evaluation des degats d'origine sismique Withdrawn EP1153264A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US11730199P 1999-01-26 1999-01-26
US117301P 1999-01-26
PCT/US2000/001613 WO2000043729A1 (fr) 1999-01-26 2000-01-25 Jauges de contrainte actives pour evaluation des degats d'origine sismique

Publications (1)

Publication Number Publication Date
EP1153264A1 true EP1153264A1 (fr) 2001-11-14

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP00906994A Withdrawn EP1153264A1 (fr) 1999-01-26 2000-01-25 Jauges de contrainte actives pour evaluation des degats d'origine sismique

Country Status (6)

Country Link
EP (1) EP1153264A1 (fr)
JP (1) JP2002535636A (fr)
CN (1) CN1345412A (fr)
AU (1) AU754096C (fr)
CA (1) CA2360802A1 (fr)
WO (1) WO2000043729A1 (fr)

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7317514B2 (en) 2005-02-03 2008-01-08 International Business Machines Corporation System and method for optimizing heat management
CN102323245B (zh) * 2011-05-19 2013-04-17 大连理工大学 多路同轴可调节光纤生化传感器
WO2013022866A1 (fr) * 2011-08-09 2013-02-14 Shell Oil Company Procédé et appareil permettant de mesurer des paramètres sismiques d'un vibrateur sismique
CN112162312B (zh) * 2020-10-01 2021-07-30 中国海洋大学 用于极浅海域地层横波速度结构探测的光纤多道地震系统
CN119469634B (zh) * 2024-11-18 2025-10-10 重庆交通大学 基于自适应化的抗震断层穿越系统及其方法
CN119289865B (zh) * 2024-12-12 2025-02-25 常州远基精工科技有限公司 一种涡轮壳加工用检测装置

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4756606A (en) * 1986-06-05 1988-07-12 American Telephone And Telegraph Company, At&T Bell Laboratories Apparatus comprising a monolithic nonlinear Fabry-Perot etalon, and method for producing same
JPH02296110A (ja) * 1989-05-11 1990-12-06 Osuto:Kk 変位センサ
JPH0862074A (ja) * 1994-08-25 1996-03-08 Hitachi Ltd 光式力センサ

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO0043729A1 *

Also Published As

Publication number Publication date
AU2856500A (en) 2000-08-07
CN1345412A (zh) 2002-04-17
JP2002535636A (ja) 2002-10-22
AU754096B2 (en) 2002-11-07
AU754096C (en) 2003-12-18
CA2360802A1 (fr) 2000-07-27
WO2000043729A1 (fr) 2000-07-27

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