There are many types of strain gauges. mechanical, optical, acoustical, pneumatic or electrical. Considering the mounting, strain gauges can be either bonded or unbonded and based on the construction, we can have foil, semiconductor, and photoelectric strain gauges. There are several types of strain gauges based on the principle of their working viz. namely, bonded and unbonded gauges depending on the method of fabrication. c. Laser. Model EDS-11V/Hermetically Sealed Vibrating Wire Strain Gage It is suitable for embedment in soil or concrete or for surface mounting by welding on steel structures. Strain gauges. Both gauges are bonded to the same test specimen, but only one is placed in a position and orientation so as to be exposed to physical strain (the active gauge). In case of an emergency, the strain gauges can generate a warning so maintenance can be done early to minimize the impact on rail traffic. Along with the construction of transducers, a bonded metal wire strain gauge is used for stress analysis. a. Bonded wire strain gauges are used on the surfaces of different structures. Unbonded Strain Gauges These strain gauges are not directly bonded (that is, pasted) onto the surface of the structure under study. A brief history of the Strain Gauge 1856 Lord Kelvin first reported on a relationship between strain and the resistance of wire conductors. Two resistive films are bonded to the PZT stack, as shown in Figure 6.5.The length change of the piezoelectric stack alters the resistance of the strain gauge. The value will be printed on each pack of precision strain gauges. The general construction of a bonded wire type strain gauge is shown in Figure 16. 3. Earlier wire types of strain gauges were used commonly, which are now being replaced by the metal foil types of gauges as shown in the figure below. In such cases, dummy gauge is used in the place of R 2 in the quarter bridge strain gauge circuit which acts as a temperature compensation device. It consists of a very thin foil bonded to an insulating backing, and the foil is etched so that it looks like a long piece of wire that has been zig-zagged (early strain gauges were actually made out of thin wire). Explain the construction of wire wound strain gauges. A second temperature effect occurs if the thermal coefficient of expansion of the strain gauge wire is The grid of fine resistance wire is cemented to carrier. Considering the mounting, strain gauges can be either bonded or unbonded and based on the construction, we can have foil, semiconductor, and photoelectric strain gauges. The metals can be easily cut into the zigzag foils for the formation of the strain gauges. 1.1) 1- Wrap-around wire strain gauge It were wound with fine copper wire on a thin paper tube, which was then flattened and stuck to a metal surface. Bonded wire strain gauge. (0.025 mm) thickness, bonded directly to the strained surface by a thin layer of epoxy resin. A resistance wire strain gauge has a wire of diameter 0.25mm or less. Wire wound gauges are made of round wire of copper-nickel, chrome-nickel, or nickel-iron alloys about 0.0064 cm diameter. 1.1) 1- Wrap-around wire strain gauge It were wound with fine copper wire on a thin paper tube, which was then flattened and stuck to a metal surface. Bonded foil strain gauges can be as small as 16 mm2 and have strain sensitivity or gauge factor of 2. b) iron aluminum alloy. It is used for high resistance Chapter One The Strain Gauge Strain gauges measure axial tension or compression with no impact on the rails. ... we need to mount bonded strain gauge on the specim. This is the reason why they are referred to as bonded gauges. Bonded Foil strain gauges The first bonded, metallic wire-type strain gauge was developed in 1938. Q. As the bonded strain gauges are well bonded on to the specimen, the entire strain being experienced by the specimen is transferred to the strain gauge. First, there is the fact that the resistance of most wires changes with temperature. Q2) Optical sensors used for the displacement measurement works on the principal that. Encardio-rite primarily deals with six different types of strain gauges: Model EDS-11V/Hermetically Sealed Vibrating Wire Strain … Bonded foil strain gauges (BFSG) are metal based foil elements that are incorporated into a flexible electrically insulating material which can then be bonded to a surface with adhesives. For example, photoelectric gauges use light. These gauges rely on direct pasting or bonding on the surface of object under measurement. Testing was being done to validate the design of a lighter horse shoe intended to reduce the stress and cracking of the horse’s foot while training and racing Explain with diagrams, the bonded and unbonded type of strain gauges… The strain gauges should have a high value of gauge factor, The resistance of the strain gauge should be as high as possible since this minimizes the effects of undesirable variations of resistance in the measurement circuit. Bonded Foil Strain gauges The first bonded, metallic wire-type strain gauge was developed in 1938. Commonly used elements for wire strain gauges are _____ ... A fine wire resistance strain gauge is stretched around the insulated pins. A wire gauge was mounted and bonded between two thin pieces of paper. It is used for high resistance Resistance Wire Strain gauges,with gage length greater than the maximum size of the Coarse Aggregate,typically 50 to 75 mm. 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