Measurement of mechanical strain stress using a strain. The strain gauge is one of the most important tools of the electrical measurement technique applied to the measurement of mechanical quantities. For information concerning the special two gage package or for questions about the tie bar strain gage, contact a ppe customer service representative at 8003210562. As their name indicates they are used for the measurement of strain. Strain gauge theory types, formulas and applications. Principle of strain gages the strain gage is tightly bonded to a measuring object so that the sensing element metallic resistive foil may elongate or contract according to the strain borne by the measuring object. Many specifications are identical for one strain gauge series. Axial and bending strain are the most common see figure 2. Shearing strain is also directly measurable, but not as easily as normal strain. From the strain equations at the end of this application note, you can see that the. Still another type of device, the photoelectric gage, uses a combination of mechanical, optical, and electrical amplifications to measure strain.
The most commonly used strain gauge is an electrical resistance strain gauge. It is another type of transducer which is used in various places in analytics of stress and strain. 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. Axial strain measures how a material stretches or compresses as a result of a linear force in the horizontal direction. Pdf strain gauge principle, types, features and applications. The values for tension and compression are specified separately. The hbm strain gauge range consists of the y, c, m, g series and special strain gauges. A strain gauge is a device which is used to measure dimensional change on the surface of a structural member under test. The strain gauge is a practical way of implementing the use of resistance pickup for mechanical strain, and an example is discussed in the companion website chapter 4. The commonly used electrical strain gauge is the bonded resistance type. The ppe tie bar strain gage also comes in a special two gage package that allows you to check both sides of your press at the same time. Two strain gauges, s a and s t, are affixed glued to the.
The characteristics of foil types strain gauges are similar to those of wire. 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. Mechanical strain gauges are among the most straightforward in the way of making and measuring. Electrical resistance strain gauges are the most frequently used devices in experimental stress analysis today. Mechanical strain an overview sciencedirect topics. Capacitance and inductance types are used in special types of applications. Wilson introduction a strain sensitive material is one whose electrical resistance is proportional to the instantaneous spatialaverage strain over its surface. Mechanical strain gauge it is made up of two separate plastic layers. There are several strain gauge types based on the principle of their working viz. When bearing mechanical elongation or contraction, most metals undergo a change in electric resistance.
The measurement range of such diaphragm vacuum gauges extends from 1 mbar 0. For example, if strain gage gauge factor k 2, the initial resistivity specified in the data sheet measured after the installation of the strain gauge to an object ro 200. These devices can detect gauge pressure if the low pressure port is left open to the atmosphere or differential pressure if connected to two process pressures. Then, after the installation of the strain gauge to the object in the mechanical testing of the object measured the electrical resistance of the strain gauge. As the force applied to the load cell increases, the electrical signal changes proportionally. Basic principle of strain gauge when stress is applied to the metal conductor, its resistance changes owing to change in length and crosssectional area of the conductor. Photoelectric strain gauge was also introduced which uses a light beam to produce electric current corresponding to deformation. Units may be mounted upon or incorporated in mechanical elements whose. Strain gauge seminar report, ppt, pdf for mechanical. Take a look at the past, present, and future of strain gauges. As their name indicates, they are used for the measurement of strain. Strain gages are used to measure linear strains that occur at surface points of an object when it responds to. It is often easy to measure the parameters like length, displacement, weight etc that can be felt easily by some senses. The four different types of strain are axial, bending, shear, and torsional.
The fundamental structure of a strain gage consists of a gridshaped sensing element of thin metallic resistive foil 3 to 6 microns thick that is sandwiched between a base of thin plastic film 1216 micron thick and a covering or lamination of thin film. 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. Strain gauge advantages and disadvantages, application what is strain gauge a strain gauge is an example of passive transducer that converts a mechanical displacement into a change of resistance. Aircraft component testing is one area of application, tiny. Another type of strain, called shearing strain, is a measure of angular distortion. Strain gage technical data strain gage measurement the most universal measuring device for the electrical measurement of mechanical quantities is the strain gage. Strain gauges 32 34 1 2 124 3, 4 2 meas exc g g meas meas exc vrr vrrrr. The transducers that convert the mechanical input signals of the physical quantity into electrical output signals are called as electrical transducers. Strain gauges are frequently used in mechanical engineering research and development to measure the stresses. There are different types of strain measuring techniques, they are 1. The bottom layer has a ruled scale on it and the top layer has a red arrow or pointer. Strain gauges give indication of strain at only one point.
In this clip we will discuss that how does a strain gauge works. Strain gauge advantages and disadvantages, application. The input given to the electrical transducers can be in the form of the displacement, strain, velocity, temperature, flow etc and the output obtained from them can be in the form of current. It is a thin, waferlike device which can be attached to a variety of materials by a suitable adhesive to measure the applied strain. The maximum values for electrical strain gauges are specified as absolute strain in the strain gauge pdf catalog. It still delivers a valid measured value in the plastic deformation zone. There are different type series within each strain gauge series. Strain gauges if a strip of conductive metal is stretched, it will become skinnier and longer, both. Strain gage type gages with flexible backing, such as polyimide, are most resistant to handling damage. Adhesives and strain gauge installation two basic types of adhesive are recommended.
If the nominal resistance of the strain gauge is designated as rg, then the strain induced change in resistance. A strain gauge is an electrical transducer which is used for measuring mechanical surface strain. Measuring strain with strain gages national instruments. Strain gauges metal that changes resistance when stressed piezo electric materials that generate a current when deformed lvdt load cell table force spring or piston lvdt outer platform strain gauge bridge rr gf rr l l rrgf. As a technical term strain consists of tensile and compressive strain, distinguished by a positive or negative sign. Electrical strain gauges are a type of strain gauge. The relation between stress and the strain initiated in a material by an applied force is expressed as follows based on. The method of measurement consists of measuring the elongation of the blades and reading this value on a scale magnified times, transmitted by means of mechanical levers. If we had a thick book sitting on a table top and we applied a force parallel to. Explore strain gauge with free download of seminar report and ppt in pdf and doc format. Earlier, mechanical type of device such as extensometer or extension meter was used to measure strain by measuring change in length. The most common types of load cell used are hydraulic, pneumatic, and strain gauge.
Demountable mechanical strain gauge developed at the bcca british cement and concrete association introduction the demountable mechanical strain gauge demec was developed at the cement and concrete association to enable strain measurements to be made at different parts of a structure using a single instrument. This type of gauge is frequently employed as a sensor in transducers to measure load, torque, pressure and acceleration. Strain gages and rosettes study notes for mechanical. Beyond the usual elements of good strain gage practice, attention to a few special considerations will help assure successful installations by avoiding thermal and mechanical damage to the strain gage sensor. However, it is very difficult to measure the dimensions like force, stress and strain that cannot be really sensed directly by any instrument. Strain gauges types electrical measurements questions. It converts a force such as tension, compression, pressure, or torque into an electrical signal that can be measured and standardized. There are various types of strain measuring methods, which may roughly be classified into mechanical, optical, and electrical methods. Types of strain gages include foil strain gage, wire strain gage. 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. Various means like mechanical, optical, acoustical, pneumatic or electrical can be used to measure deformation strain of an object. 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.
The metallic foil type strain gage consists of a grid of wire filament a resistor of approximately 0. Each strain gauge series is available with different bonding adhesives. Foil strain gauge semiconductor strain gauge photoelectric strain gauge 10. Electrical resistance strain gages are sensors made of thin foil or wire type conductors that respond to variations in length with variations in electrical resistance. Strain gauges may be purchased as complete units, with both strain gauge elements and bridge resistors in one housing, sealed and encapsulated for protection from the elements, and equipped with mechanical fastening points for attachment to a machine or structure. Apparentstrain correction for combined thermal and. Several types of strain gages depend for their operation on the proportional variance of electrical resistance to strain. Bonded foil strain gages the first bonded, metallic wire type strain gage was developed in 1938. For these tests, high strains between 1% and 10% are possible with hbms foil strain gauges.