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- strain gauges and measurement.pdf
- Manual on Experimental Methods for Mechanical Testing of Composites
- Manual on Experimental Methods for Mechanical Testing of Composites
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strain gauges and measurement.pdf
The main purpose of a strain gauge is to indirectly determine stress and its variation with time, quantitatively. Change in stress is determined by multiplying the measured strain by the modulus of elasticity. We have covered its working principles, characteristics, features, as well as, application areas. Strain GaugeStrain Gage measures the strain amount of contraction as well as expansion caused by external forces on any object. The strain gauge was invented in by Edward E.
Simmons and Arthur C. Any basic strain gauge consists of an insulating flexible backing that supports a metallic foil pattern. The gauge is attached to the object under stress using an adhesive.
The deformation in the object causes the foil to get distorted as well which ultimately changes the electrical resistivity of the foil. This change in resistivity is measured by a Wheatstone bridge which is related to strain by a quantity called Gauge Factor.
Encardio-rite primarily deals with five different types of strain gauges. The model EDSV strain meter is suitable for embedment in soil or concrete or surface mounting by welding on steel structures. It provides significant quantitative data on the magnitude and distribution of compressive and tensile strain and its variations with time. The Encardio-rite strain meter incorporates the latest vibrating wire technology to provide the remote digital readout of compressive and tensile strain in dams, bridges, underground cavities, tunnels , mines, steel structures and other areas of strain gauge application where strain measurement is required.
This results in the effect of oxidation, moisture, environmental conditions and any ingress of water being completely eliminated. The Encardio-rite vibrating wire strain meter basically consists of a magnetic, high tensile strength stretched wire, one end of which is anchored and the other end is displaced proportionally to the variation in strain.
Any change in the strain directly affects the tension of the wire, resulting in a corresponding change in the frequency of vibration of the wire. The resonant frequency, with which the wire vibrates, is read by the readout unit. The strain is proportional to the square of the frequency and the readout unit is able to display this directly in strains.
Model EDSV-AW basically consists of two end pieces joined by a tube that encloses a length of magnetic, high tensile strength stretched wire. An extra waterproofing is provided on the strain gage by a heat-shrinkable tube to prevent the ingress of water. The tube is flattened in the middle to accommodate a sensor assembly in the constriction.
The sensor forms an integral part with the strain gage. The strain gage is better suited for locations subjected to dripping or running water or which may submerge in water. To mount the strain gage, two annular mounting blocks are accurately positioned and aligned with the help of a mounting jig and dummy gage and welded to the structure.
The dummy gauge is then finally replaced by the actual strain gage and clamped in position by a pair of set screws on each block. Groutable reinforced bar annular mounting blocks are available for surface mounting the strain gage to a concrete structure.
Model EDSV-E vibrating wire strain gage is designed to measure strain in underground cavities, tunnels, buildings, concrete and masonry dams etc. The strain gage is suitable for embedding in soil or concrete. The embedment strain gage is similar to the arc weldable strain gage except for the fact that mounting blocks are replaced with stainless steel flanges.
A stainless steel foil tab fixed to each end block enables the gage to be spot-welded or fixed in place by epoxy. The gage is pre-tensioned by a small compression spring. Initial tension can be set during installation, allowing for maximum range in tension or compression as required. The garage is designed to be used only for flat surfaces. A strain gauge depends on the electrical resistivity of any conductor. The resistance in any conducting device is dependent on its length as well as the cross-section area.
Whenever an external force changes the physical parameters of an object, its electrical resistivity also changes. A strain gauge measures this deformity by using the Gauge Factor formula. Whenever the external compressive or expansion force is increased or decreased on any object, its electrical resistivity also increases or decreases proportionally. The Gauge Factor of a Strain Gauge is the sensitivity coefficient of strain gauges and, is given by the formula:.
The gauge factor for common metallic foil is usually a little over 2. The output voltage of the Wheatstone Bridge, SV is given by the formula:. Here are all the characteristics of Strain Gauge that are needed for the accurate functioning of the instrument. In such cases, the error depends on the gauge length and the gauge width. The gauge size for a mechanical strain gauge is calculated by the distance between the two knife-edges in contact with the specimen and by the width of the moveable knife edge.
Sensitivity can be defined as the smallest value of strain which is readable on the strain gauge scale. The choice of a gauge is highly dependent upon the degree of sensitivity required, and quite often the selection of a gauge with a very high sensitivity increases the complexity of the measuring method. The next characteristic of the strain gauge is its range. The range represents the maximum strain which can be recorded without resetting or replacing the strain gauges.
Also, the range and sensitivity are interrelated since a highly-sensitive gauge responds to small strains with indicator deflections and the range is usually limited to the full-scale deflection of the indicator. In a mechanical strain gage, inaccuracies may result from lost motion such as backlash gear train, friction, temperature changes, and wear in the mechanism, slippage, or flexure or deflection of the components. The scope of strain gauges in real life is unlimited. It can be used to test deformity in multiple structures such as high-rise buildings, underground metro corridors, bridges, dams, deep vacations, railway lines, etc.
Strain gauges are fixed to the structural load-bearing components to measure stresses along load paths for wing deflection or deformation in an aeroplane. The strain gauges are wired into the Wheatstone Bridge circuits and its application areas include onboard signal conditioning units, excitation power supplies, and the telemetry necessary to read in site measurements.
Instrumentation of bridges is done to verify design parameters, evaluate the performance of new technologies used in the construction of bridges, to verify and control the construction process and for subsequent performance monitoring. Well-instrumented bridges can alert responsible authorities about approaching failure so as to initiate preventive measures.
Choosing proper sensor types, technology, a measurement range and their location on the bridge is very important to optimize costs and to extract full benefits of instrumentation.
It becomes necessary to monitor the bridges regularly for any kind of deformation as it might lead to fatal accidents. This calls for application of strain gauge in the engineering field. Strain gauge technology is used in the real-time monitoring of huge bridges, making the inspections precise. The bridge is installed with many measurement channels that sense wind speed and strain on its cables. Strain Gauges have a long history in the safety of rails.
It is used to measure stress and strain on rails. Strain gauges measure axial tension or compression with no impact on the rails. 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.
Strain gauges can measure the torque applied by a motor, turbine, or engine to fans, generators, wheels, or propellers. You will find such types of equipment in power plants, ships, refineries, automobiles and industries. Strain Gauges are pretty reliable and widely used sensing elements applied in the field of Geotechnical Instrumentation. However, there are very minor limitations that you can mention when it comes to drawbacks.
Each Model of Strain Gauge offers limitations in terms of fatigue, temperature, amount of strain, and the measurement environment.
However, with the complete range from Encardio-rite, you can easily examine the strain gauge features and specification and use it as per your preference. The main advantages of mechanical strain gauges are the ease with which they can be used, their relatively low cost and the fact that they are reusable. Electrical resistance strain gauges overcome most of the disadvantages of mechanical gauges. The main advantage of a four-wire ohm circuit is that the lead wires do not affect the values because the voltage is detected directly across the strain gauge element.
It is a measure of internal pressure on an object whenever an external force acts on it. The larger the force or the smaller the area over which it acts, the more likely the material is going to deform. The strain is a unitless quantity since the values in the numerator and denominator always have the same units. The amount of deformation that occurs in an object is known as strain. There can be different types of strain.
This was all about strain gauges and, if you have any further queries, do let us know in the comments below. Your email address will not be published. Save my name, email, and website in this browser for the next time I comment. What Is A Strain Gauge? Strain Gauge Working Principle Hermetically Sealed Vibrating Wire The Encardio-rite vibrating wire strain meter basically consists of a magnetic, high tensile strength stretched wire, one end of which is anchored and the other end is displaced proportionally to the variation in strain.
Characteristics of Vibrating Wire Sister Bar Strain Meter Suitable for long-term installation Easy to install and waterproof Reliable and precise measurement possible Fully encapsulated for protection against handling and installation damage Rugged construction Applications of Vibrating Wire Sister Bar Strain Meter Suitable for measurement of strain in reinforced concrete structures Strain measurement in concrete piles and cast in place concrete piles.
How does a Strain Gauge Work? What is the working Principle of Strain Gauge? Characteristics of Strain Gauge Here are all the characteristics of Strain Gauge that are needed for the accurate functioning of the instrument. Gauge Sensitivity Sensitivity can be defined as the smallest value of strain which is readable on the strain gauge scale. Range The next characteristic of the strain gauge is its range.
Accuracy In a mechanical strain gage, inaccuracies may result from lost motion such as backlash gear train, friction, temperature changes, and wear in the mechanism, slippage, or flexure or deflection of the components. Cable Bridges Instrumentation of bridges is done to verify design parameters, evaluate the performance of new technologies used in the construction of bridges, to verify and control the construction process and for subsequent performance monitoring.
Rail Monitoring Strain Gauges have a long history in the safety of rails. Torque and Power Measurements in Rotating Equipment Strain gauges can measure the torque applied by a motor, turbine, or engine to fans, generators, wheels, or propellers. Limitations of Strain Gauge Strain Gauges are pretty reliable and widely used sensing elements applied in the field of Geotechnical Instrumentation.
What are the types of Strain Gauges? What is Stress? Leave a Reply Cancel reply Your email address will not be published.
Manual on Experimental Methods for Mechanical Testing of Composites
The Tensile stress is like pulling the material on each side or might one side as figures shown below,. The Compressive stress is like pushing the material on each side or might one side as figures shown below,. The figure is shown below,. They have the tendency to hold the deformation that occurs in the plastic region. A material is brittle if, when subjected to stress, it breaks without significant plastic deformation. Brittle materials absorb relatively little energy prior to fracture, even those of high strength.
Strain gauges may be used in "smart bridge" technology to detect structural problems early. Strain gauge technology has practically unlimited uses in the field. It can be used to test vehicles, ship hulls, dams, and oil drilling platforms. A simple civil engineering application using strain gauge technology is to install strain gauges on structural components in a bridge or building to measure stress and compare them to analytical models and stress calculations. Field-testing needs differ from laboratory testing needs because of complex shapes, geometry, access, and environment. In many instances new testing devices have to be designed and manufactured to match the required application.
Materials testing, dynamic material response and fluid-structure interaction.
Manual on Experimental Methods for Mechanical Testing of Composites
Every component in a linear motion system experiences some form of loading due to applied forces or motion. Strain is the deformation or displacement of material that results from an applied stress. The most common way to analyze the relationship between stress and strain for a particular material is with a stress-strain diagram.
Techni Measure Online Store offers the facility to purchase some of our most popular strain gauges an accessories with next working day delivery and credit card payments. Strain gauges are used to determine or verify component or structure stresses, or by manufacturers of load cells, pressure and torque transducers, etc. Stress itself cannot be directly measured but strain can, and for many materials within their elastic limit, there is a linear relationship between stress and strain. Thus, if strain can be measured, stress can be calculated.
The main purpose of a strain gauge is to indirectly determine stress and its variation with time, quantitatively. Change in stress is determined by multiplying the measured strain by the modulus of elasticity. We have covered its working principles, characteristics, features, as well as, application areas. Strain GaugeStrain Gage measures the strain amount of contraction as well as expansion caused by external forces on any object.
The backing material performs Bonded Strain Gauges These gauges are directly bonded that is pasted on the surface of the structure under study.
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A strain gauge also spelled strain gage is a device used to measure strain on an object. Invented by Edward E. Simmons and Arthur C. Ruge in , the most common type of strain gauge consists of an insulating flexible backing which supports a metallic foil pattern. The gauge is attached to the object by a suitable adhesive, such as cyanoacrylate.
A strain gauge was invented by Edward E. Simmons and Arthur C. Ruge, in
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Strain Gauge Types – Encardio-rite Models
Peer review under responsibility of Karabuk University. The purpose of this study is to quantitatively compare the strain measurement techniques. The volume change of the cement paste is measured by the amount of water displaced by the submerged sample. Strain measurements are restricted because of necessity to the accessible surfaces of the structural parts and can consequently only give information about the stress state at the component's surface. General descriptions of the various techniques and specifics such as gauge lengths and sensitivities are noted. Stresses are calculated by measuring strains in a minimum of two directions, and a general max-imum of nine directions. Whereas uniaxial and planar stress states can be analyzed relatively simply using strain measurement techniques, in particular using strain gauges.
Трепет ожидания, волны, сносившие его то влево, то вправо, закрытые глаза, почти беззвучное движение губ в молитве. Он попытался вернуться назад, но совладать с мощным потоком было невозможно - все равно как плыть против сильного течения могучей реки.
Католицизм здесь посильнее, чем в самом Ватикане. - У нас, конечно, не все его тело, - добавил лейтенант. - Solo el escroto. Беккер даже прервал свое занятие и посмотрел на лейтенанта.
Хейл выжидал. Стояла полная тишина, и он внимательно прислушался. Ничего.
- Я должен найти его партнера, прежде чем он узнает о смерти Танкадо. Вот почему я тебя вызвал. Мне нужна твоя помощь. Сьюзан плохо его понимала.