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Twenty years of monitoring pipelines in landslides
Published in Jan Rybář, Josef Stemberk, Peter Wagner, Landslides, 2018
Michal Bukovanský, Graeme Major
The strain gage installations provided useful results within a short time. They enabled NWP to closely monitor the strain (and stress) changes in the pipeline caused by the landslide deformations, and to implement early mitigation to prevent pipeline rupture (Bukovansky et al. 1985). NWP required advice from their geotechnical consultants less frequently, since the monitoring was performed by their own staff, who also decided on mitigation requirements using suitable criteria. Additional strain gages were installed in 1984. The strain gage monitoring system helped to reduce the rate of pipeline failures significantly. It also proved to be reliable over an extended period of time. Many strain gages installed in 1983 are still functional without maintenance or with only minor repairs.
Computer-Based Instrumentation: Sensors for In-Line Measurements
Published in Gauri S. Mittal, Computerized Control Systems in the Food Industry, 2018
The strain gauge measures force indirectly by measuring the deflection (strain) it produces in a calibrated carrier. Advantages are good frequency response, fast output, good resolution and accuracy, and low impedance. Kinds of strain gauges include resistance type, semiconductor type, and piezoelectric type. The resistance strain gauge is a resistor whose resistance changes with applied strain caused by applied force. Unbonded gauges are of a wire stretched between two points. Widely used bonded gauges are made of a grid of very fine wire or foil bonded to the backing or carrier matrix. These are low in cost, can be made with a short length of wire or foil, are only moderately affected by temperature changes, have small physical size and low mass, and have fairly high sensitivity to strain. These foil-type gauges are produced by photo-etching techniques. They have a large ratio of surface to cross-sectional area, which permits the gauge to follow the specimen temperature and facilitates the dissipation of self-induced heat. They are more stable under high temperature and prolonged loading. The gauge resistances range from 30 to 3000 ohms, with 120 and 350 ohms being the most commonly used.
Chapter 18 Pressure Measurement
Published in B H Brown, R H Smallwood, D C Barber, P V Lawford, D R Hose, Medical Physics and Biomedical Engineering, 2017
The most common type of pressure transducer consists of a diaphragm, one side of which is open to the atmosphere and the other connected to the pressure which is to be measured. Pressure causes a proportional displacement of the diaphragm which can be measured in many ways. The most common method is to use strain gauges (see section 20.2.2). A strain gauge is a device which measures deformation or strain. A single crystal of silicon with a small amount of impurity will have an electrical resistance which changes with strain. If a silicon strain gauge is attached to the diaphragm of the pressure transducer then its resistance will change with the pressure applied to the diaphragm. Unfortunately the resistance of the silicon will also change with temperature, but the effect of this change may be eliminated by attaching four strain gauges to the diaphragm (figure 18.3).
Efficiency of image correlation photogrammetry technique in measuring strain
Published in Australian Journal of Structural Engineering, 2018
A. Al-Mosawe, H. Agha, L. Al-Hadeethi, R. Al-Mahaidi
Strain gauges are electrical devices that can measure strain at a specific location. A strain gauge consists of metal foils or wires that are arranged in a pattern that allows it to elongate until it reaches its elastic limit (Smith 2005). Gauges are connected to a transducer that provides electrical resistance. This technique was developed in the 1950s by Lord Kelvin, who first observed the electrical resistance in metal cords, and this observation paved the way for the invention of strain gauges (Smith 2005). Different types of strain gauges have been developed and are used widely in several applications, such as aircraft manufacture and other engineering industries. Strain gauges measure the elongation or shortening of the patterns of the gauge, and by monitoring the changes in electrical resistance, the strain can be derived accurately. However, the strain gauge technique has some limitations. For example, gauges need to be calibrated before use, they cannot be used at high temperatures as the glue loses its strength, and it is time-consuming to monitor strains for large-scale structural elements.
Experimental investigation on a flapping beam with smart material actuation for underwater application
Published in Mechanics of Advanced Materials and Structures, 2021
Ganesh Govindarajan, R. Sharma
Herein, a simple beam of length of 300 mm, width of 60 mm, and thickness of 3 mm is tested in a glass flume facility present at Department of Ocean Engineering, IIT Madras, India. Material of the beam: stainless steel. Dimension of the flume is: 20 m × 0.6 m × 1.1 m (Length × Breadth × Depth) and it is filled with water and provides the flapping beam sufficient space to move without being affected by the boundaries on both the sides. The beam is also located at mid-depth in the glass flume tank to avoid any interference from the free surface and the bottom of the tank. The experimental setup consists of the power amplifier, function generator, and beam with smart material. Function generator creates the signal to undulate the MFC in the desired forms such as square, sinusoidal, ramp-like waves, etc. Power amplifier increases the signal voltage by 20 times so that high voltage required for efficiently driving the MFC actuators can be achieved. Function generator can create the signal within ±5 V limit. Our experiments focus on the propulsive characteristics of an undulating beam for different operational depths. Herein, the variations of thrust and efficiency with respect to the input voltages and actuation frequency are studied and analyzed in detail and the depth of submergence ‘h’ is defined to be the distance from the undisturbed free surface to the top of the beam. The schematic of submerged beam depths is shown in Figure 1. Image of the experimental setup with focus on uni-morph beam and supporting structure is shown in Figure 2. Deformation of the beam is recorded using a strain gauge. A strain gauge is a device that is used to measure the strain and force on an object. As the beam gets deformed with the smart material, it causes its electrical resistance to change. The underwater dynamics of a MFC unimorph cantilever beam is modeled using the theory of linear bending vibration. As shown in Figure 2, unimorph MFC is fixed with a clamp at the tip of a horizontally located stainless steel beam and strain gauge is attached at head, which functions as a transducer cantilever.