The following matlab project contains the source code and matlab examples used for optical strain measurement by digital image analysis. It is another type of transducer which is used in various places in analytics of stress and. In this article, we will focus on intrinsic fiber optic strain sensors, where the fiber itself is the sensor. An example of straingauge reading under an optical microscope. Optical strain measurement is a strain measurement method based on digital image processing. Probing the ultimate limit of fiberoptic strain sensing. The information contained herein is believed to be accurate and reliable.
Following are the two type of optical strain gauges, martens optical gauge tuckerman optical gauge martens optical gauge in martens optical gauge a single mirror system is to be used. The fo strain gauge suite consisted of the traditional linear, singleaxis distributed strain gauge arrangement and a newly developed fo rosettestyle, multiaxis strain gauge arrangement. Optical strain gauge optical strain gauge sirohi, rajpal s chau, fook s. Fiber optic sensor for strain measurements, and particularly fbg fibre bragg. A strain gauge also spelled strain gage is a device used to measure strain on an object. Gravitationalwave, longbaseline interferometers are the most sensitive strain detectors developed to date, with impressively low detection limits on the order of 10. No part of this instruction manual may be reproduced, by any means, without the written consent of geokon, inc. Since there are no epoxies holding the fiber to the carrier, long term stability is ensured by design.
Optical strain gauge micron optics fiber sensor tiltul linksyouwanttoremember cimg6345 optical strain gauge micron optics. Strain gages are the most common sensing element to measure surface strain. Glass scale can be read optically by means of a light source,an optical system and photocells. However, if the sample is very small, stripeshaped or very compliant, this may alter the testing geometry and hence influence the measurement significantly. The force and moment free body diagram of the slope beam. It is designed to measure, condition rectify and filter, and display the feedback signal derived from ac bridge strain gauge systems. Strain gauges are used either to obtain information from which stresses internal forces in bodies can be calculated or to act as indicating elements on devices for measuring such quantities as force, pressure, and acceleration. Strain gauge sheet metal electrical resistance and. An optical strain gage incorporates an optical waveguide or fiber that includes a sensing section with a fiber bragg grating, which serves for detecting a strain in a strainable member on which the strain gage is mounted.
This is the strain that we typically measure with a bonded resistance strain gage. The sibased optical microring resonator was employed as the sensing element, which was embedded on the microcantilevers. Concrete cylinder compression load test tests were carried out on a fp4000 strain gauge embed. Other types of optical fiber sensors use the fiber itself to transmit light, not. Optical fiber sensor for monitoring the strain of concrete. The bar was then subjected to incremental loads and the strain values recorded at each increment. At locations displaced away from the fiber bragg grating section, on both sides thereof, the optical waveguide is covered by two fastening elements, which secure the optical. This paper presents a strain gauge using the mechanicaloptical coupling method. The entire strain gage package is typically covered with a protective material. The model fp4000 fiber optic strain gauge is designed to. Optical gage definition of optical gage by merriamwebster. The strain gauges have a very low coefficient of thermal expansion and can be used to measure both mechanical and thermomechanical strains in a variety of. Ospa fiber optic strain sensor, probe and transducer. The design of the optical strain gauge is based on the speckle shift.
Optical strain sensor fundamentals strain gage hbm. Our product line encompasses a complete range of instruments, from simple strain viewers polariscopes and polarimeters to specialized online and offline equipment for measuring stress and other optical properties in a wide range of materials. In this application note, we will be more specific and define the term strain to mean deformation per unit length or fractional change in length and give it the symbol. The optical strain gauge consists of a silica core and cladding that channel the light in the fiber and an outer coating usually plastic for protection. Osa strain gauge using sibased optical microring resonator. Sensors designed to easily retrieve static and dynamic strain measurements for. When the specimen elongates the measuring knife edge will. Long measuring grids are recommended where there is an inhomogeneous. Two fp4000 strain gauges were mounted onto oppo site faces of a 1. Figure 5 shows the optical gauge data plotted alongside the data from a resistance strain gauge taken at the same time. The armored cable is compatible with connector protection fittings see below that protect splice free series connections to strain, temperature, acceleration and other types of optical sensors.
The nominal rated resistance is stated on each strain gauge package including the resistance tolerance per package. Strainoptics polarimeters, polariscopes measure stress in. These sensors are very sensitive with a gauge factor as high as 170 and a flat frequency. Electrical strain gauges optical fiber strain gauges that are based on fiber bragg gratings fbgs operate on very different principles than those that govern traditional electrical strain gauges. Common strain gauges often have a large thermal output as shown in figure 1. Pdf sensors for monitoring creep strain in highpressure steam pipes and other power plant. Optical gage definition is a gage as a micrometer comparator that makes no direct contact with the object measured but measures an optical image of it. The os3100 optical strain gage is designed to make fiber handling easy and sensor installation fast and repeatable. Traditionally, precise strain measurements during uniaxial tensile testing can be performed by clamping a strain gauge to the sample. Thermal apparentstrain sensitivity of surfaceadhered, fiberoptic strain gauges tomas valis, dayle hogg, and raymond m. As shown in fig 1, the sensor is placed at the end of the fiber which is sheathed for robustness and the other end is fitted with an optical coupler for connection to a signal analyzer.
Pdf in recent years, the field of structure monitoring has been making increasing use of systems based on fiberoptic technologies. The method is a noncontact measurement technique, which alleviates the need for modifying the parts for leadwire routing and sensor attachment as required in traditional strain gage instrumentation. The paper presents a technique that could be used to measure 1 inplane displacement, 2 the velocity of a solid body using a principle similar to that used in lda, and 3 strain at a point. Pdf optical strain measurement techniques to assist in life. Optical strain measurement by digital image analysis. This way, the free fiber with fbg is located at the down side of the sensor pad. Interfacial characterization of soilembedded optical. The strain gauge measuring grid length dependents on aim of measurement, as the result of a measurement using strain gauges will be the mean strain underneath the measuring grid. The singlemode optical fiber is embedded in the cement mortar ring as strain gauge, after that, poured the cement mortar ring into concrete cylinder. The pullout force was applied by an electric motor at the displacement rate of 0.
The experimental results show that applying external strain triggers a clear redshift of the output resonant spectrum of the structure. Learn the existing types of stress, their origin and states, or how to determine stress from measured. Black1, david zare1, levy oblea1, yonglae park1, behzad moslehi1, and craig neslen2 1intelligent fiber optic systems corporation ifos 2363 calle del mundo, santa clara, ca 950541008 2afrlrxlp, 2230 10th street building 655, wright patterson afb, oh 454337817 abstract. Strain gages structure of strain gages there are many types of strain gages. Optical sensors and interferometers are widely used for highsensitivity strain measurements. Other types of strain gages are acoustic, capacitive, inductive, mechanical, optical, piezoresistive, and semiconductive. Opticalfiber strain gauges with asymmetric etched structures have been analyzed, fabricated, and tested. Optical strain gage os3150 key features rugged, permanent weldable package. Optical gauge lineup and benefit 03 06 08 10 12 14 16 18 20 22 24 mapping stage c8126 series optical nanogauge thickness measurement system c27 supported optical microgauge thickness measurement system c11011 supported optional products 23 optional products optical gauge series excels at defocus and angular dependence.
Strain may be either tensile positive or compressive negative. The force is applied on the free end of the beam by means of placing scale calibration weights on a support made and positioned on the free end. Us3517999a us3517999da us3517999a us 3517999 a us3517999 a us 3517999a us 3517999d a us3517999d a us 3517999da us 3517999 a us3517999 a us 3517999a authority us united states prior art keywords body light strain gauge photocell optical strain prior art date 19660107 legal status the legal status is an assumption and is not a legal conclusion. What follows is a detailed description of the construction, application, and measurement of 196 fo rose tte strain gauges that measured multiaxis strain. In this clip we will discuss that how does a strain gauge works. Pdf on may 1, 1979, john m webster and others published a new optical strain gauge find, read and cite all the research you need on researchgate.
Distributed strain sensing from different optical fiber. This makes the ospa strain gauge completely immune to any electromagnetic interference. Ruge in 1938, the most common type of strain gauge consists of an insulating flexible backing which supports a metallic foil pattern. Among strain gages, an electric resistance wire strain gage has the advantages of lower cost and being an established product.
Pdf analysis of the accuracy of fibreoptic strain gauges. In order to monitor the strain of concrete which caused by freezethaw ft cycles, a novel type of white light interferometer wli sensor is designed and tested. The gauge is attached to the object by a suitable adhesive, such as cyanoacrylate. We have used sofo fibreoptic strain gauges to perform measurements to check the overall. Acoustic strain gage article about acoustic strain gage. The pivoted knife edge carries a mirror and the other end of this arm is fastened to specimen.
Lets briefly learn about stress and strain and strain gages. Strain gauge, device for measuring the changes in distances between points in solid bodies that occur when the body is deformed. It is completely insensitive to transverse strains and temperatures and its microminiature size makes the ospa fiber optic sensor ideal for spaceconstrained applications such. Polymer optical fiber strain gauge for humanrobot interaction forces assessment on an active knee orthosis.
It comprises of an aluminum beam with one end fixed on a support and the other end free. Optical strain measurement by digital image analysis in. Optical strain measurement system development ntrs nasa. An instrument used for measuring structural strains. The curves can be seen to enter the nonlinear region of strain, and their slopes agree to within 6 percent. Its stainless steel carrier holds the fbg in tension and protects the fiber during installation.
Photoelasticity at work in strainoptics sv2000 strain viewer. Stress analysis by using strain gages theory page 3 15 3 gage size should be as small as possible to adequately estimate the strain at a point. Hbm strain gauges are available with 120 ohm, 350 ohm, 700 ohm or 1,000 ohm resistance. A new method for mounting fiber optical strain gages to structures will be. These optical strain gauges are installed across sections of welded steam pipe and other plant. The clamp was used to connect the free end of the optical. Optical strain measuring techniques for high temperature. Optical engineering ebooks advanced search home proceedings volume 3407 article. Ntis rc ac41l1e so1 cscl 143 unclas opt 1c al sis 11 ti r e asu bx n c 6335 00s79t8 john 2. On the gage factor for optical fiber grating strain gages richard j.
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