Thermal apparent strain sensitivity of surfaceadhered, fiberoptic strain gauges tomas valis, dayle hogg, and raymond m. When the specimen elongates the measuring knife edge will. Our 3d digital image correlation 3d dic and photogrammetry instruments measure material properties, structural response, and product quality in automotive, aerospace, biomechanics, microelectronics, civil structures and defense fields. While electronic strain gauges are a mature technology, optical strain gauges continue to develop capabilities in defect detection on large buildings and structures, fea model validation, and structural health monitoring of composite materials. The range of strain gauge resistance is from 30 to 3k ohms. Modulus of elasticity slope of the initial linear portion of the stress strain diagram. Strain gauge type ls31 is a resistive gauge, welded onto side a of a sample structure, fs62 is an optical gauge, welded onto the same side. The time delay of the signals received back is then analyzed to calculate the strain in the structure. Us3462223a us3462223da us3462223a us 3462223 a us3462223 a us 3462223a us 3462223d a us3462223d a us 3462223da us 3462223 a us3462223 a us 3462223a authority us. Optical strain gauge sg with extended temperature range special features optical strain gauge based on fiber bragg grating installation as for electrical strain gauges, or as for ol can be used in extended temperature range from 40c to 100c suited for high strain applications 2% deformation measurement on curved surfaces. Strain gage beam typical strain gage values here are some typical values for resistance, strain gage factor, and strain, along with the predicted values of change in resistance.
In principle, dic compares a series of greyscale images of a sample at different stages of deformation, tracks pixels movement in the region of interest roi 2 and calculates displacement and strain by the use of correlation algorithm. As a baseline reference, the price of a common general purpose axial strain gauge cea. Waterproof strain gauges wfseries have a preattached vinyl lead wire and eliminate the need for moistureproof coating. Pdf optical strain measurement techniques to assist in life. Bridge completions resincored solder lead free solder 80 sg installation case 81 amplifier systems 82 software 84 optical strain gauges 86 seminars 87 literature 88. To avoid surface contamination, do not touch the microcapillary of the fiber optic strain gauge with your hands. Such systems are especially useful in tests were both strain gages and fbgs are used. The invention is characterized characterized in that the optical waveguide 5 outside the fiber bragg grating portion 10 on. A strain gage cannot measure the stresses directly. It is very difficult to strain gage tight locations reliably. Volume 121, issue 18, october 2010, pages 16351641. This article shows the influence of a plane strain test specimen geometry on the measurable strain field and the influence of free edge effects over the stress computation. Pdf on may 1, 1979, john m webster published a new optical strain gauge find, read and cite all the research you need on researchgate.
Many specifications are identical for one strain gauge series. Optical strain gauge micron opticsfiber sensor tiltul linksyouwanttoremembercimg6345 optical strain gauge micron optics. Strain monitoring in stiffened composite panels using. Spie 3407, international conference on applied optical metrology, 29 september 1998. We have used sofo fibre optic strain gauges to perform. Comparisons are also carried out between the proposed optical strain gauge and traditional strain gauges such as electronic strain gauge, compressometer and demec mechanical strain gauge, which further confirm the accuracy, convenience and. The the invention relates to a strain gauge comprising at least one optical waveguide 5, which is on a thin pad 1 is attached.
The pivoted knife edge carries a mirror and the other end of this arm is fastened to specimen. Data from the strain gauges were recorded, stored and evaluated using a bmc messsysteme gmbh equipment 8. Bridge completions, resincored solder, lead free solder 91 optical strain gauges 92 customerspecificstrain gauges 93 seminars 94. This way, the free fiber with fbg is located at the down side of the sensor pad. Connect the lead wires of the strain gage to the binding posts of the flexor as shown in figure 1.
Strain gauge sheet metal electrical resistance and. R, and a second gauge is placed transverse to the applied strain. 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. Besides the electrical strain gage, the measurement principle of fiber braggbased sensors has recently become established. The modulus of elasticity may also be characterized as the stiffness or. Characterisation of an optical strain gauge for pantograph applications. Strain gauge measurement units can also be used for measuring a pipelines operational parameters for instance, the pressure of the transported medium, and for preventing. Buffered fibre sensor with a free fibre length around the fbg for direct fixation of the.
Following are the requirements of strain gauge so that it gives the accurate measure of strain extremely small size and negligible mass simple and easy attachment to the specimen under test good. Distributed strain sensing from different optical fiber. Where multiple gauges are to be monitored the field sens multichannel, signal conditioner is recommended. Controlling edgelift reduces optical distortion and the. These optical strain gauges are installed across sections of welded steam pipe and. Only two masks are needed for the strain gauge fabrication, an anchor mask and a structure mask. When a strain gauge is stretched, its resistance changes according to the following formula. The main purpose of a strain gauge is to indirectly determine stress and its variation with time, quantitatively. In 1969, first gradient index fibers were manufactured by the cooperation of nippon sheet glass co. Strain gages on composites temperature compensation. Opti 222 mechanical design in optical engineering 21. By using two strain gauges in the bridge, the effect of temperature can be avoided. In this work a singleended polarimetric strain sensor has been used for strain measurements.
Introduction 6 strain gauges from hbm strain gauge series the hbm strain gauge range consists of the y, c, m, g series and special strain gauges. Free space optical coupling to fiber bragg grating sensors. The two dimensional state of stress existing on a 2d surface can be expressed in terms of three cartesian strains. Which strain gauge is the right one for your application. 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. Strain test compare strain gage response to free space coupled fbg sensor optical spectra comparison of fbg and strain gauges reflection measurement fusion splice ase mmf beam splitter osa smf water angle smf polished mmf grating connector smf input light reflected light the reflection of unembedded fbg was measured using free space coupling. The electrical strain gauge was replaced by the fibre optic strain gauge in the second version of the flow sensor. This dual gauge model has a 16inch 406 mm base and is specifically designed for measuring edgelift edge curl in heattreated flat glass a requirement of en 18632 and en121502, but can also be used as a flatbottom rollwave gauge. Pdf an introduction to measurements using strain gages. Strain gauges are important geotechnical tools that measure strain in underground cavities, tunnels, buildings, concrete, masonry dams, bridges, embedment in soilconcrete. Moire interferometry reveals planar displacement fields on a parts surface, which is caused by. Strain gauges are widely used for many applications, and in particular are perfect for making geotechnical measurements and determining mechanical loads on structures. We have used sofo fibreoptic strain gauges to perform.
An optical signal generated from a source such as a laser is input into one end of the optical fiber. An introduction to measurements using strain gages. Glass scale can be read optically by means of a light source,an optical system and. Pdf sensors for monitoring creep strain in highpressure steam pipes and other power. In a fiber optic strain gauge the sensor measures the strain by shifting the light frequency of the light reflected down the fiber from the bragg grating, which is embedded inside the fiber itself.
A strain gauge is a device used to measure the strain on a free surface of a structure. Foundation monitoring resistive versus fiberoptical strain. After the optical strain gauge is set up, the axial concrete strain as well as the stress strain curve is plotted in real time when the concrete sample under testing is loaded. Fiber optic sensor for strain measurements, and particularly fbg fibre bragg.
The fseries standard strain gauges are using lead free solder and are intended for general use. Like for electrical foil gages, the optical strain gage is also sensitive to. The test set includes the extensometer with digital gauge resolution 0. The strains converted from rayleigh frequency shift measurements agree reasonably well with readings by one of the four hoop strain gauge. The optical response of the strain gauge at 10 and 1550 nm wavelength. The world leader in nondestructive optical stress inspection. Transducers definition of transducers classification. Stress, strain, and strain gages, page 2 strain gage the principle discussed above, namely that a wires resistance increases with strain, is key to understanding how a strain gage works.
Jan 19, 2021 strain measurement devices is dedicated to development and research ensuring continuous improvements to our sensors and manufacturing processes. Characterisation of an optical strain gauge for pantograph. Compared to traditional electrical strain gauges, optical strain gauges. In this case, the optical waveguide contains 5 at least one section 10 with a fiber bragg grating 6, which serves to detect strain. The optical measurements show good agreement with conventional strain. Strain gauge is used to measure deflection, stress, pressure, etc. Materials material gage factor, g tcr 105 ni80 cr20 2. Optical strain gauges are available on the marked since one year and are proofed in many applications. Therefore, the strain has little effect on the second gauge, called the dummy gauge. A model for using dielectric elastomer sensors for contraction sensing within a mckibben muscle described the. Optical strain gauges are used to measure strains in concrete structure, concrete dams, rock, steel structures etc.
The concrete elasticity modulus is then determined from the curve. Trilion quality systems develops precision 3d optical measurement and inspection testing devices. The gauge microcapillary must be free of grease, dust, etc. A strain gauge also spelled strain gage is a device used to measure strain on an object. The resistance of the sensing element changes with applied strain. There are 92 suppliers who sells optical strain gauge on, mainly located in asia.
There are different type series within each strain gauge series. Strain gauges from hbm optical weldable strain sensors from hbm fibersensing. Monitoring pipeline integrity with fiber optic strain sensor. 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 model fp4000 fiber optic strain gauge is designed to. Ultimate strength the maximum stress the material can withstand based on the original area. A new method for mounting fiber optical strain gages to structures will be. The hbm strain gauge range consists of the y, c, m, g series and special strain gauges. Transverse sensitivity the transverse sensitivity is the ratio of the sensitivity of a strain gauge transverse to. A strain gauge is a device used to measure the strain on a free surface of a.
Strain gage adhesives and cements general information and selection guide because a strain gage can perform no better than the adhesive with which it is bonded to the test member, the adhesive is a vitally important component in every strain gage installation. For the most part, strain gage applications are limited for the strain measurements on free surfaces of a body. G for semiconductor materials 5070 x that of metals. Introduction 6 strain gauges and accessories strain gauge series the hbm strain gauge range consists of the y, c, g, v series and special strain gauges. Although there is no single adhesive ideally suited to all. The strain gauge selection considerations are gauges length and width, the configuration of the solder tab, availability, carrier material, number of gauges, and arrangement of gauges in gauge pattern. Foundation monitoring resistive versus fiberoptical. Strain gauge lvdt thermocouple thermistor digital transducersthese transducers convert the input quantity into an electrical output which is in the form of pulses.
Strain gauges for stress analysis catalogue pdf hbm. Applications the model fp4000 fiber optic strain gauge is designed to measure strain in or on tunnel linings bracing. Mar 03, 2021 the optical strain gauge is a versatile alternative to conventional electronic strain gauges. The signal is reflected at reflective markers at predetermined positions in the optical fiber. First applications in experimental mechanics have shown that this technology offers a lot of potential. These are the different types of strain gauge installations varying according to the connection technique and the installation surface properties. Change in stress is determined by multiplying the measured strain by the modulus of elasticity. An intrinsic gradedindex multimode optical fibre straingauge.
The price per strain gauge varies depending on the rarity of gauge and the ordered quantity. Strain sensorembedded soft pneumatic actuators for extension. Optical strain gauge 1998 sirohi publications spie. Optical strain sensor fundamentals strain gage hbm. Fibre bragg sensors compared with electrical strain gauges. Practical strain gage measurements omega engineering. Applied sciences free fulltext fiber optic sensing for. The strain gauges were placed at different positions on the bays and omega stringers at the foot and the top of stringers, as shown in figure 3 and figure 4. Adjust the free end of the beam so that motion is not impeded by the sides of the flexor. The experimental strain field distribution is measured over the whole deformable zone of a plane strain test specimen by an optical strain gauge. Strain gauges are procured in hundreds of different configurations depending on the application backing material, gage length, pattern type, resistance value, etc. Readouts capable of dynamic measurements up to hz are also available.
The gauge is attached to the object by a suitable adhesive, such as cyanoacrylate. Short history of optical fibers the history of optical fibers reaches back to the 1960ties. On the reverse of the same sample we have two bondable glued strain gauges, ly41 is resistive, and fbg is optical. Pdf analysis of the accuracy of fibreoptic strain gauges. Our product line encompasses a complete range of instruments, from simple strain viewers and roller wave gauges to specialized, softwarebased, online measurement systems. Ruge in 1938, the most common type of strain gauge consists of an insulating flexible backing which supports a metallic foil pattern. The strain gage was invented by ed simmons at caltech in 1936. The specifications for the strain gauges are based on the reference temperature of 23c 73. The companys engineering and development staff supports product design, shorten development cycles, and provide productionengineered solutions.
Furthermore, bonding a gage to a small feature could alter its. A stepbystep guide to strain gauge installation bestech. As a baseline reference, the price of a common general purpose axial strain gauge cea xx w250a350 is used. Pdf in recent years, the field of structure monitoring has been. Connect leads numbered 1, 2, and 3 of the flexor to the input cable of the 2311. Strain measurement with fiber bragg grating sensors. Moire interferometry reveals planar displacement fields on a parts surface, which is caused by external loading or other source deformation. Glass scale can be read optically by means of a light source,an optical system and photocells. We offer a wide range of foil strain gauges and optical strain gauges that can be installed using the abovementioned techniques. Strain gage adhesives and cements thermo fisher scientific. Digital image correlation trilion quality systems gom. Moire interferometry strain gauges moire interferometry is an optical technique that uses coherent laser light to produce a high contrast, twobeam optical interference pattern. Optical strain gauge download pdf info publication number us3462223a. Dic is a noncontact optical technique for measuring strains.
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