Fiber optic sensor for strain measurements, and particularly fbg fibre bragg grating sensors, has been. Many specifications are identical for one strain gauge series. Sensors that are commonly employed for shm are resistance strain gauges, fiber optic sensors, piezoelectric sensors, eddy current sensors, and microelectromechanical systems mems sensors. Roman ruzek, martin kadlec, konstantinos tserpes, evanggelos karachalios. Osa practical fiberoptic bragg grating strain gauge system. Measurement is based on grating wavelength changing linearly with strain. Readouts capable of dynamic measurements up to hz are also available. Agreement between the two gauges is very good, with the final offset strain values of the optical and resistance gauges within 2 microstrain of each other. Strain gauge preparation by sticking a short length of adhesive tape along the upper face of the gauge it may be picked up from a flat clean surface. Strain monitoring in stiffened composite panels using embedded fibre optical and strain gauge sensors. There are different type series within each strain gauge series. Jun 25, 2008 traditionally, precise strain measurements during uniaxial tensile testing can be performed by clamping a strain gauge to the sample. Ospa fiber optic strain sensor, probe and transducer. Optical strain measurement is a strain measurement method based on digital image processing.
Holding both ends of the tape, orientate the gauge in the desired location and stick the end of the tape furthermost from the tags to the specimen. This gauge consists of two fibers for transmitting a beam from a light source and for receiving a reflectingback beam, and in between them a concave mirror with a hole is settled. A fine wire resistance strain gauge is stretched around the insulated pins. In the general purpose strain gauge section you will find the strain gauge patterns next to the part numbers so that you will be able to see the geometry of the strain gauge. 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. The attributes of each sensor configuration are discussed. How many sensors can be integrated into one single fiber. Semiconductor optical amplifier soafiber ring laser and. We have used sofo fibreoptic strain gauges to perform measurements to check the overall relative deformation of a real reinforced concrete structure. Other types of optical fiber sensors use the fiber itself to transmit light, not. Unlike conventional strain gages that only measure strain at a discrete point.
Thus, in order to use it to determine strain, compensation has to be made for temperature effects. Highly precise, multiplexable and electromagnetic interference immune, optical fiber grating strain gages can be key elements in structural health monitoring systems 1, 2. Ospa fiber optic strain gauge fiber optical sensors for. A novel optical gauge for measuring coil strain during. Optical strain sensors, namely those based on fiber bragg grating fbg technology, have been gaining increased attention particularly in the field of infrastructure monitoring over the past decades. However, if the sample is very small, stripeshaped or very compliant, this may alter the testing geometry and hence influence the measurement significantly. Strain gages structure of strain gages there are many types of strain gages.
Aug 04, 2016 optical strain gauge micron optics fiber sensor tiltul linksyouwanttoremember cimg6345 optical strain gauge micron optics. However, it will also change resistance when subject to a temperature change. Overview of fiber optic sensor technologies for strain. Among them, a universal strain gage has a structure such that a gridshaped sensing element of thin metallic resistive foil 3 to 6m thick is put on a base of thin plastic film 15 to 16 m thick and is laminated with a thin film. Fiber optic sensing can be employed to measure strain along an optical fiber. It was inserted in the spacepropagating region as well as a quarterwave plate. A fibre optic fo strain gage consists of an optical fibre with a fibre bragg. 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. Compared to traditional electrical strain gauges, optical strain gauges. Therefore, if we replace r4 in figure 3 with an active strain gauge, any changes in the strain gauge resistance will unbalance the bridge and produce a nonzero output voltage. The propagating light is split at the active part into a transmitted part and in a reflected part. Comparisons to values derived from a semiconductor electrical strain gauges are also made. 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.
Optical strain measurement by digital image analysis in. Development of an optical strain measurement method using digital image correlation. Optical strain measurement by digital image analysis file. On the gage factor for optical fiber grating strain gages richard j.
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. Pdf measuring range other ranges available on request. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. The electrical resistance strain gauge is a resistance element which changes resistance when subject to strain. Stress is defined as the objects internal resisting forces, and.
Analyzing more than one active strain gauge in the bridge. Nov 26, 2001 here, instead of a conventional strain gauge made of a metal wire, we propose an optical fiber gauge. Optical strain sensor fundamentals strain gauge hbm. It is another type of transducer which is used in various places in analytics of stress and strain. The dependence of the beat frequency shift on the pressure is shown in figure 6.
Fiber optic rosette strain gauge development and application on a largescale composite structure jason p. They are attached to the unit under test and so experience the same strain as the unit. Balanced constant current excitation for dynamic strain. Optical strain gauges also called fiber optical strain sensors or fos, optical strain sensors or fiber bragg grating sensors are used to measure strain, but can easily be integrated into different types of transducers, such as in temperature, acceleration or displacement. The goal of such diagnostics is to detect, identify, locate and assess the defects that may affect the safety or performance of a structure. The measurements group acquired jp technologies and blh, two respected names in strain gauge manufacturing, to support their growing global demand for strain gauges and instrumentation. The bar was then subjected to incremental loads and the strain values recorded at each increment. Strain can be measured using various types of devices classified depending upon their.
Miao luo shanghai institute of applied mathematics and mechanics shanghai 200072, china dwayne d. The center frequency of the reflected light shifts with the introduced strain andor temperature, so the fbg sensor performs as long term stabil, calibration free optical strain gage. Composite test sample with strain gauges and optical fibre. This makes the ospa strain gauge completely immune to any electromagnetic interference. Strain gage dimensions strain gage dimensions gage length is an important consideration in strain gage selection, and is usually the. The results from the optical strain sensor showed good consistency with contact measurements made by using both a foil strain gauge and a whittemore gauge. Nonmetallic optical strain gage os3200 micron optics.
The hbm strain gauge range consists of the y, c, m, g series and special strain gauges. Owing to the excellent characteristics of fiber optical sensors, several. One solution is to use an ac signal to excite the bridge, as shown in figure 1. Measurements will be made with a strain gage rosette in this experiment to obtain the principal stresses and strains on a cantilevered beam. Concrete cylinder compression load test tests were carried out on a fp4000 strain gauge embed ded inside a concrete cylinder 6 diameter. Such systems are especially useful in tests were both strain gages and fbgs are used.
Static and dynamic behavior of the optical strain gauge is investigated and its performance is compared to similar optical sensing systems either directly surface mounted on the structure or embedded into composite laminates. Optical strain measuring techniques for high temperature. Three axis strain and temperature fiber optic grating sensor. Optical strain gauges can come in handy, though, where electrical ones wont work, for example due to environmental conditions. 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. Optical strain measurement by digital image analysis. From the measured electrical resistance of the strain gauge, the amount of induced. With each sensor, micron optics provides a sensor information sheet listing the gage factor and calibration coefficients needed to convert wavelength information into engineering units. Semiconductor strain gage integrated planer multielement strain gage example. A quarter bridge setup for high precision stress measurements should consist of one strain gauge attached to a compensation object which has the same material as the test surface. There may be other strain gauges in the bridge, as precision resistors for temperature compensation. If this is your first time to visit or if you have not completed hp support registration, please continue by clicking on the button below. If the nominal resistance of the strain gauge is designated as rg, then the strain induced change in resistance.
Strain gauge seminar report, ppt, pdf for mechanical. Determining aerodynamic loads based on optical deformation. The os3100 optical strain gage is designed to make fiber handling easy and sensor installation fast and repeatable. An instrument used for measuring structural strains. They are designed to be both linear and to have negligible effect on the unit they are attached to. Strain gauge and rosettes introduction a strain gauge is a device which is used to measure strain deformation on an object subjected to forces. Ruge in 1938, the most common type of strain gauge consists of an insulating flexible backing which supports a metallic foil pattern. In a basic experimental arrangement of the fbg strain sensor, the. It has a high spatial resolution and is well suited to capture true peak strain in high strain gradient areas. Experiments were conducted on a compressed concrete beam and a real prestressed concrete member during the manufacturing process. An optical strain gauge for measuring the strain in a structural member includes a mechanical grating device fixedly attached to the structural member for modulating an incident beam of light by diffraction. Where multiple gauges are to be monitored the field sens multichannel, signal conditioner is recommended.
Separate search groups with parentheses and booleans. The strain gauge uses a fiberoptic bragg grating sensor to measure strain and a passive, wavelength demodulation system to determine the wavelength of the narrowband, backreflected spectrum from the grating sensor. The following matlab project contains the source code and matlab examples used for optical strain measurement by digital image analysis. Short history of optical fibers the history of optical fibers reaches back to the 1960ties. When external forces are applied to a stationary object, stress and strain are the result. Development of an optical strain measurement method using. Optical strain gauge optical strain gauge sirohi, rajpal s chau, fook s.
In this clip we will discuss that how does a strain gauge works. 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. The change in resistance measured by a single strain gauge is extremely small, around 0. Strainoptics polarimeters, polariscopes measure stress in. Explore strain gauge with free download of seminar report and ppt in pdf and doc format. Acoustic strain gage article about acoustic strain gage by. Dimensions listed for gage length as measured inside the grid endloops and grid width refer to active grid dimensions. Optical fiber strain gauge using a mirror with a pinhole. The scale of the optical strain gauge can be significantly changed up or down, from satellite ground target application to microscopic displacement sensing, and still preserve its fundamental advantages. What results is a dc output proportional to the strain on the bridge.
The optical fiber strain measurements show good agreement with strain gauge measurements. In experimental stress analysis, we apply a given load and then measure the strain on individual. The electricalresistance strain gage is the most widely used device for strain measurement, its operation is based on the principle that electrical resistance of a conductor changes when its subjected to mechanical deformation. Since there are no epoxies holding the fiber to the carrier, long term stability is ensured by design. A strain gauge also spelled strain gage is a device used to measure strain on an object. Traditionally, precise strain measurements during uniaxial tensile testing can be performed by clamping a strain gauge to the sample. They were situated at widely separated places in the usa and. Pdf analysis of the accuracy of fibreoptic strain gauges. Optical sensor developments for measuring the surface. A fiberoptic strain gauge system for use in structural monitoring and smartstructure applications is described. The fundamental structure of a strain gage consists of a. Fbg sensor was embedded into the structure of composite specimen. Its stainless steel carrier holds the fbg in tension and protects the fiber during installation.
Furthermore, the strain gauge detected a quench and from the measurement the temperature attained by the coil is deduced. Unbonded strain gauges consists of frames p and q carrying rigidly fixed insulated pins. Most of these methods track two fiducial marks, with one at. Finite element analysis fea was used to model the coil and excellent agreement was found with measurement. These precision strain gauges can be used for experimental stress analysis monitoring industrial equipment or various scientific applications. Vishay have been associated with intertechnology inc.
Multiple optical strain gages can be arranged in close proximity at 0, 45 and 90 degrees for strain rosette measurements. Three axis strain and temperature fiber optic grating sensor article pdf available in proceedings of spie the international society for optical engineering 2718 january 1996 with 158 reads. The fiberoptic strain gauge system permits the measurement of. Displacementstrain measurements using an optical microscope and digital image correlation dongsheng zhang shanghai university department of mechanics shanghai 200444, china email. Embedded fibre optical and strain gauge sensors roman ruzek, martin kadlec, konstantinos tserpes, evanggelos karachalios to cite this version. In addition the compensation strain gauge and the strain gauge which is applied to the test surface should be of the same lot. Attachment of the strain gauge also includes strain distortions around edges, where the strains are transmitted from the test sample to the gauge 3. Strain monitoring in stiffened composite panels using. The ad8221 gains the signal and an ad630ar synchronously demodulates the waveform. Unbonded strain gauge is used in places where the gauge is to be detached and used again and again. Fiber optic rosette strain gauge development and application. Introduction to strain gauges and their usage strain gauge applications strain gauges are used to determine or verify component or structure stresses, or by manufacturers of load cells, pressure and torque transducers, etc.
Strain gauge, device for measuring the changes in distances between points in solid bodies that occur when the body is deformed. Modern stress and strain analysis a state of the art guide to measurement techniques. The curves can be seen to enter the nonlinear region of strain, and their slopes agree to within 6 percent. Pdf distributed strain sensing from different optical fiber. Displacementstrain measurements using an optical microscope. The geokon fiber optic strain gauges are designed for use in environments where it may be difficult to use conventional types of strain gauges because of space considerations, high levels of electrical interference or where intrinsic safety is an issue. May 25, 2017 the optical strain gauge may be envisioned as a competitive alternative to using a bonded strain gauge in many of its traditional applications. Keep it simple dont use too many different parameters. Juarez langley research center, hampton, virginia mark c.
An active strain gauge is on the material and can be deformed by stress. These two frames can move relative with respect to each other. The output is just an average strain or displacement over the gauge length of the specimen. Introduction there are various cabling and hookup schemes used for strain gage measure ments ranging from a simple twowire connection, to as many as eleven wires.
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