We will introduce considerations that affect the accuracy of this measurement and suggest procedures for. Strain gauges wheatstone bridge teaching experiment. In experimental stress analysis, we apply a given load and then measure the strain on individual. Pdf strain gauges are used to measure the strain of a material.
A strain gage sometimes referred to as a strain gauge is a sensor whose resistance varies with applied force. When load is acted on a material, elongation or compression is happened. Stress analysis by using strain gages introduction a state of strain in 3d the 3d strain tensor may be characterized by its. It is ideal for groups of two or more students to do experiments and for classroom demonstrations. During that experiment, the wood sensor operated at the same time. Wheatstone bridge circuit theory, example and applications. A strain gage wheatstone bridge is configured with 1, 2 or 4 gages according to the measuring purpose. Strain rosettes are three strain gages positioned in a rosettelike layout. Am5400 experimental stress analysis lab course material, iit madras. The fundamental structure of a strain gage consists of a. To measure load tensilecompressive using load cell on a tutor. The change in resistance measured by a single strain gauge is extremely small, around 0.
The factor k, also known as the gage factor, is a characteristic of the strain gage and has been checked experimentally 2. Building an analog circuit to obtain deflection measurements using a strain gage in this experiment, you will build an analog circuit for using a 120. The exact value is specified on each strain gage package. It contains everything needed to show students how resistance strain gauges work on three different structures. The strain gauge module consists of a cantilever beam which is fixed on a rigid body. The wheatstone bridge is used for measuring the very low resistance values precisely. Strain gauge trainer description the compact strain gauge trainer. Gages will be used to measure the strains on a soda can to calculate its internal pressure, and measure the strains on a cantilever beam to calculating poissons ratio and youngs modulus for the material. To measure torque of a rotating shaft using torsion meterstrain gauge torque transducer. A strain gauge is basically used to measure the strain in a work piece. Ruge in 1938, the most common type of strain gauge consists of an insulating flexible backing which supports a metallic foil pattern. The gunt fl100 measurement amplifier reads the wheatstone bridge and outputs the strain as. Esa is the analysis of the mechanical stress state in materials, which is performed though experiments using strain gauge measurements.
To measure the speed of a motor shaft with the help of noncontact type pickups magnetic or. Strain gauge is a passive transducer that converts a mechanical elongation or displacement produced due to a force into its corresponding change in resistance r, inductance l, or capacitance c. Part a 1 calibration of pressure gauge 1 2 calibration of thermocouple 5 3 calibration of lvdt 4 calibration of load cell 17 5 determination of modulus of elasticity of a mild steel specimen using strain gauges 21 part b 6 measurement of thread parameters using optical projector toolmaker. The gauge factor for many gauges is about 2, however, each gauge may have a slightly different gauge factor and it is therefore important to note this factor in your notes during the experiment. Ae 3610 transient stress measurements in thinwall pressure vessel 5. It contains everything needed to show students how resistance strain gauges work on three diff erent structures. Tagarielli, strain measurements with resistance strain gauges, lab handout, imperial college london, date unknown. Four strain gauges are placed on the surface of the beam. The compact strain gauge trainer fits on a bench or desktop. Strain gage dimensions strain gage dimensions gage length is an important consideration in strain gage selection, and is usually the. Dimensions listed for gage length as measured inside the grid endloops and grid width refer to active grid dimensions. In general, the gage factor for metal strain gages is about 2.
Strain gauge project introduction the strain gauge was implemented by edward e. Strain gages structure of strain gages there are many types of strain gages. Conclusions glossary bibliography summary electrical resistance strain gages are sensors fabricated from thin foil or wiretype conductors that respond to variations in their length. This catalog presents the full range of tml standard strain gauges and associated. Due to the fractional measurement of resistance, wheatstone bridges are mostly used in strain gauge and thermometer measurements. Static strain measurement cantilever beam objectives. The bonded foil strain gauge is one of the most important transducers in the realm of engineering. Criteria, procedures, recommendations for technical questions, contact document number. Strain gauge and rosettes introduction a strain gauge is a device which is used to measure strain deformation on an object subjected to forces. Measurements will be made with a strain gage rosette in this experiment to obtain the principal stresses and strains on a cantilevered beam. Use strain gauges to measure the strain in a loaded steel cantilever.
The accuracy of these models can be verified through testing. If a metal piece is subjected to a tensile stress, the metal length will increase and thus will increase the electrical. Stress analysis by using strain gages theory page 6 15. A strain gauge also spelled strain gage is a device used to measure strain on an object. However, it is very difficult to measure the dimensions like. The metallic strain gage consists of a very fine wire or, more commonly, metallic foil arranged in a grid pattern. The most widely used strain gage is the bonded metallic strain gage. Below, the wheatstone bridge circuit will only be considered with respect to its application in. The gauge is attached to the object by a suitable adhesive. In this laboratory experiment, you are required to find poissons ratio and youngs modulus for the.
The purpose of this experiment is to acquaint you with the wheatstone bridge circuitry used in strain measurement and with commercial strain measuring equipment. Therefore by measuring three linearly independent strain in three direction, the components of the plain stress state at the point where strain rosette is located can be calculated. One way of validating a math model is to use a strain gage measurement system to measure the strain at the. Laboratory 3 strain gage sensors national instruments. Comparing strain gage measurements to force calculations. It consists of an insulating flexible backing which supports a metallic foil pattern. If the nominal resistance of the strain gauge is designated as rg, then the strain induced change in resistance. The electrical resistance strain gage discussed in this chapter is basically a piece of very thin foil or fine wire which exhibits a change in resistance propor. Two strain gauges are placed over the beam and two are beneath the beam. The strain gauge metal is attached firmly to a strong flexible insulating transparent sheet. 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. Measuring strain with strain gages national instruments.
It is ideal for groups of two or more students to do experiments. Ae 2610 tensile testing and strain gauges 5 r r r s r s g g d. A strain gage s electrical resistance varies in proportion to the amount of strain in the device. January 27, 2016 comparing strain gage measurements to force calculations in a simple cantilever beam 4 p a g e mqp, hazel figure 1 stress strain graph showing elastic and plastic region davis stress when a body is loaded with a force, the material must compensate for this load by altering the shape of.
In this lab, you will make measurements of mechanical strain in small aluminum beams as you bend them. K is a constant known as the gauge factor and is the relative strain. Learn the existing types of stress, their origin and states, or how to determine stress from measured strains by reading about it below. Beams strain measurements using strain rosettes in. Page 1 19 me 410 mechanical engineering laboratory experiment 5. To measure staticdynamic pressure of fluid in pipe. A d9 connector connects the strain gauges with the signal conditioning unit. The service temperature of a strain gauge depends on the. To measure torque of a rotating shaft using torsion meter strain gauge torque transducer. This is about the resistance measurement using a wheatstone bridge for precise measurement.
It is often easy to measure the parameters like length, displacement, weight etc that can be felt easily by some senses. For varied strain gage bridge formation systems, refer to bridge. This experiment includes techniques for installing and using foil strain gages. By adjusting the weight mounting point, three different beam lengths will be tested in this experiment. A strain gauge is a sensor used to measure the strain of an object. In this experiment, you will use a beam with four strain gauges preattached and wired to form a four active leg wheatstone bridge. Scribd is the worlds largest social reading and publishing site.
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