The voltage change was then used to find the strain incurred on the strain gauge. Comparing strain gage measurements to force calculations in a. What is the change in gauge resistance when a 1 kg load is suspended from the beam. Static strain measurement cantilever beam objectives. I am currently investigating the loadcarrying mechanism of a driven pile hollow bar and trying to install strain gauge on the pile for measurement of stress distribution. Strain gages structure of strain gages there are many types of strain gages.
Installing a strain gauge is much easier than it looks. Bonded foil strain gages strain gage arrangements the strain gage is one of the important electrical measurement technique applied to the measurement of mechanical quantities. Strain gauge project introduction the strain gauge was implemented by edward e. Beams strain measurements using strain rosettes in.
The metallic strain gauge consists of a very fine wire or, more commonly, metallic foil arranged in a grid pattern. Test your final strain gage with an ohm meter and verify that you read approximately 120 ohms. 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. Strain gauges are used as sensors in many systems to measure forces, moments. If the nominal resistance of the strain gauge is designated as rg, then the straininduced change in resistance. A strain gauge is a sensor with a variable resistance. There are three steps in obtaining experimental strain measurements using a strain gage. The gauge is attached to the object by a suitable adhesive.
In this experiment single active gages are used in the bridge circuit shown. Replace the potentiometer with the second strain gage and replace the rb resister with the potentiometer. Strain gages are used to measure linear strains that occur at surface points of an object when it responds to some actuating load, as shown in figure 1. Each of these configurations is designed with a specific task in mind. Stress analysis by using strain gages introduction a state of strain in 3d the 3d strain tensor may be characterized by its. Singlesupply strain gauge in a bridge configuration. Measurement and metrology lab strain gauge experiment. You will then observe the voltage output from your. Two strain gauges are placed over the beam and two are beneath the beam. It is commonly known that the strain gage transforms strain applied into a proportional change of resistance. All the theories related t o design a strain gauge. Learn about the use of resistance strain gages and wheatstone bridges learn to use a static strain indicator practice the application of uncertainty analysis to a physical situation. Laboratory 3 strain gage sensors national instruments. The strain gauge is bonded to a thin backing carrier, which is attached directly to the load cell enabling the strain of the load cell to be experienced by the strain gauge.
The change in resistance measured by a single strain gauge is extremely small, around 0. The wheatstone bridge is also well suited for the measurement of small changes of a resistance and is, therefore, also suitable for measuring the resistance change in a strain gage sg. Strain gage in this laboratory we design our first electronic device, an electronic weight scale. 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. Also explore the seminar topics paper on strain gauge with abstract or synopsis, documentation on advantages and disadvantages, base paper presentation slides for ieee final year mechanical engineering me or production automobile students for the year 2019 2020. 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 experimental stress analysis, we apply a given load and then measure the strain on individual. 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. The factor k, also known as the gage factor, is a characteristic of the strain gage and has been checked experimentally 2. The change in resistance across the strain gauge was found by measuring the voltage across the strain gauge using a wheatstone bridge and amplifier circuit connected to the strain gauge. Strain gauge and rosettes introduction a strain gauge is a device which is used to measure strain deformation on an object subjected to forces. Choosing a backup generator plus 3 legal house connection options transfer switch and more duration. Figure 1 shows a strain gage with two electrical leads on the right side. Measurement of strain due to bending and axial loads aluminum specimens were statically loaded for analysis in the measurements laboratory of w.
Now adjust the potentiometer until you get zero volts at the center point. It consists of an insulating flexible backing which supports a metallic foil pattern. Theory of using strain gauge and wheatstone bridge to get internal pressure in this section we will find out what the relation between mechanical properties of a can with the. 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. For varied strain gage bridge formation systems, refer to bridge. To measure the speed of a motor shaft with the help of noncontact type pickups magnetic or photoelectric.
Woolrich laboratories at the university of texas at austin. With the cantilever beam unloaded, measure and note the resistance of one of the gauges using a digital multimeter in resistance mode. An investigation of the relationship between internal. Figure 2 normalized strain gauge factors in tonnesm. Some suggestions for cleaning are to sand the surface off with a fine grit sandpaper, rinsing it with a degreasing agent, rinsing it. A strain gauge also spelled strain gage is a device used to measure strain on an object.
The purpose of this experiment is to understand the characteristics of a strain gauge transducer. Before beginning the structural test, you will first bond the prewired linear strain gauge to the specimen. Comparing strain gage measurements to force calculations. Solder the red wire to one strain gage tab and solder the black and white wires to the other strain gage tab. Ae 2610 tensile testing and strain gauges 5 r r r s r s g g d. A strain gauge transducer is shown in figure below. As their name indicates, they are used for the measurement of strain. 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. 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. Electrical resistance strain gages are sensors made of thin foil or wiretype conductors that respond to variations in length with variations in electrical resistance. January 27, 2016 comparing strain gage measurements to force calculations in a simple cantilever beam 5 p a g e mqp, hazel eq 3 where the stress vector is now equal to the normal and sheer stress components. Lateral strain data is displayed here for the dynamic experiments. This circuit is a halfbridge strain gauge circuit and should have twice the sensitivity as the quarterbridge.
Page 1 19 me 410 mechanical engineering laboratory experiment 5. The strain of a body is always caused by an external influence or internal effect such as force. Strain gauge transducer strain is defined as the deformation that occurs when a force is applied to a stationary object. 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. This causes the solder to cool too quickly and form a bead shape on the strain gauge leads rather than coating the surface. Calculating principal strains using a rectangular strain gage rosette strain gage rosettes are used often in engineering practice to determine strain states at specific points on a structure.
The compact strain gauge trainer fits on a bench or desktop. In this experiment the strain gage will be utilized. When load is acted on a material, elongation or compression is happened. Axial strain data is displayed here for the dynamic experiments. Below, the wheatstone bridge circuit will only be considered with respect to its application in. Nov 30, 2016 measurement and metrology lab strain gauge experiment. In our lab, the resistance of the strain gauge is measured by the vishay 7000.
Strain rosettes are three strain gages positioned in a rosettelike layout. The grid pattern maximizes the amount of metallic wire or foil subject to strain in the parallel direction figure 2. Background to strain gauge and extensometer calibrations. Figure 1 illustrates three commonly used strain gage rosette configurations. Strain can be measured using various types of devices classified depending upon their. Switch back to the series ix software and click on the play button. A typical strain gauge is made up of very fine wire, or foil, set up in a grid pattern in a way that produces a linear change in resistance when strain is applied along one axis. One way of validating a math model is to use a strain gage measurement system to measure the strain at the. 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 gauge, device for measuring the changes in distances between points in solid bodies that occur when the body is deformed. In this laboratory experiment, you are required to find poissons ratio and youngs modulus for the aluminum bar supplied with two strain gauges to test specimen in the appropriate configuration and. This article presents an application of strain gauges in measurements of strain which occurs in charge air cooler during the thermal cycle test. Measurement of strain due to bending and axial loads.
Click on windowsshow diagram to display your block diagram. You specify the filename for two types of files the. The resistance changes in the strain gauges are very small, therefore the gauges are connected in a wheatstone bridge circuit see figure 2. The gauge on top of the beam is in tension, the gauge underneath the beam is in compression, hence strain causes equal and opposite resistance changes in the gauges. Foil strain gauges when attached to a specimen, produce very small changes in resistance. Four strain gauges are placed on the surface of the beam. The birdman contest is an annual event held on lake biwa near kyoto, japan. You will input the gauge factor into the vishay system which will output the strain directly for later data analysis.
A strain gauge is a sensor used to measure the strain of an object. The exact value is specified on each strain gage package. Stress analysis by using strain gages theory page 6 15. A d9 connector connects the strain gauges with the signal conditioning unit. Me 302l cee 370l materials mechanics laboratory manual. The strain gauge amplifier is a purpose designed hybrid, low noise, low drift, linear dc amplifier in a 24 pin dil package, specifically configured for resistive bridge measurement and in particular the strain gauges detailed earlier in this data sheet. Lastly, section 5 draws the conclusion of our experiment. Example strain gauges bonded in to an specimen, gives out electr ical out put by changing its resistance when material is strained. Press the bal button on strain indicator twice to balance the bridges when unloaded, wait for the device to perform autobalancing then press record to save the values.
The purpose of this experiment is to acquaint you with the wheatstone bridge circuitry used in strain measurement and with commercial strain measuring equipment. A strain gauge is a device that measures change in electrical resistance when a force is applied. The strain gauge changes differ in tension load cells vs. The configuration file for this experiment is beam. Introduction it is very important that resistance strain gages be mounted on the structure on which measurements are to be made in such a manner that the gages are strained in. Ruge in 1938, the most common type of strain gauge consists of an insulating flexible backing which supports a metallic foil pattern. Clean the surface of the object where you want to attach it. Learn the existing types of stress, their origin and states, or how to determine stress from measured strains by reading about it below. A cantilever beam was loaded at the tip, and data was recorded from basemounted strain gages. Stress analysis by using strain gages page 2 7 procedure 1. Experimental stress analysis esa is the analysis of the mechanical stress state in materials, which is performed though experiments using strain gauge measurements. Tips and tricks for using strain gauges tips and tricks for using strain gauges be it strain gauge sg selection, installation or interpretation of the results there are some aspects to be taken into account when taking measurements using strain gauges. A strain gage wheatstone bridge is configured with 1, 2 or 4 gages according to the measuring purpose.
We will also use an instrumentation amplifier to gain up the signal. Assemble the wheatstone bridge circuit as shown in figure 2. Explore strain gauge with free download of seminar report and ppt in pdf and doc format. Its resistance varies with the applied force and it. The fundamental structure of a strain gage consists of a. Labview strain gage sensor integration on material in. This is probably the most difficult step because the soda in the can keeps the strain gauge cold.
In this contest cleverly designed humanpowered airplanes and gliders fly several hundred meters across the lake. To measure torque of a rotating shaft using torsion meter strain gauge torque transducer. The accuracy of these models can be verified through testing. Measurements will be made with a strain gage rosette in this experiment to obtain the principal stresses and strains on a cantilevered beam. Strain gauge seminar report, ppt, pdf for mechanical. Pdf strain gauges are used to measure the strain of a material. 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 most widely used gauge, however, is the bonded metallic strain gauge. The objective of this experiment is to study the stress and strain relationships of. Esa is the analysis of the mechanical stress state in materials, which is performed though experiments using strain gauge measurements. Solder the wires to the terminals on the strain gauge. Using strain gages to do experimental stress analysis duration. Pdf application of strain gauges in measurements of.
You will use the vishay 7000 acquisition system to record the reading from the strain gauge. The power supply provides the energy to drive the transducers, exam ple differential transformer, which is a transducer used to measure displacement required an ac voltage supply to excite the coil. It is ideal for groups of two or more students to do experiments and for classroom demonstrations. 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. If the nominal resistance of the strain gauge is designated as rg, then the strain induced change in resistance. In general, the gage factor for metal strain gages is about 2. Experiment 5 physics 250 wheatstone bridge apparatus power supply precision multimeter precision resistors wheatstone bridge temperature bath strain gauge introduction during this laboratory period you will study the wheatstone bridge, a special technique used in highprecision electrical dc measurements. For some applications 2 or 4 active gages are used in a bridge. This experiment includes techniques for installing and using foil strain gages.