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The role of geotechnics in surface mining operations and post-mining site development
Published in R. N. Chowdhury, Geomechanics and Water Engineering in Environmental Management, 2017
A rod extensometer is a simple instrument for precise measurement of the dilation of a tension crack between three pegs installed in a triangular layout around the tension crack. The peg is a 29 mm diameter steel rod of 2.0 m length grouted in a 47 mm borehole using a base pin grout. One of the pegs is threaded to couple a threaded universal jointed rod and the other pegs have a pin point welded at the end. The extensometer consists of several sections of hollow steel rod screwed together to any desired length and having a screwed universal jointed rod at one end and an index rod carrying a dial gauge at the other. The last index rod is telescopic and rests on the pin point welded on the peg. The range of extensometer is between 0.5 m to 6 m, with an accuracy of 0.1 mm and can give the extension measurements directly. Figure 3 shows a surface extensometer together with the layout of measuring stations to monitor the growth of a tension crack associated with a surface mining excavation.
Measurement of Strain
Published in John Bird, Newnes Engineering Science Pocket Book, 2012
This may be used in conjunction with a Hounsfield Tensometer (which is a universal portable testing machine capable of applying tensile or compressive forces to metals, plastics, textiles, timber, paper and so on), or with any other testing machine. The extensometer is a precision instrument for measuring the extension of a test specimen over a 50 mm gauge length, while the test specimen is loaded in the testing machine. The instrument can be attached to round specimens of material of up to 25 mm in diameter or rectangular sections of material of up to 25 mm square at precisely 50 mm gauge length without prior marking of the specimen. Figure 26.3 shows a typical Hounsfield extensometer viewed from two different elevations.
Traditional and Advanced Characterization Techniques for Reinforced Polymer Composites
Published in Shishir Sinha, G. L. Devnani, Natural Fiber Composites, 2022
Amit Pandey, G. L. Devnani, Dhanajay Singh
The specimen is mounted first in the grips of the testing machine (Figure 7.2) to determine the elastic modulus of the specimen. A universal testing machine requires a constant rate of movement. The machine consists of one grip that is in stationary mode and a second grip with a movable mode. A load-indicating mechanism capable of indicating the tensile load is used with good accuracy. An extensometer is also used to find out the distance between the two points placed within the gauge length of the test sample when the sample is stretched.
Influence of Deposition Positions on Fretting Behaviors of DLC Coating on Ti-6Al-4V
Published in Tribology Transactions, 2019
Hao-Hao Ding, Vincent Fridrici, Gaëtan Bouvard, Jean Geringer, Julien Fontaine, Philippe Kapsa
Fretting wear tests were conducted using a tension–compression hydraulic machine and a home-made fretting wear setup with a cylinder-on-flat contact. A schematic outline of the fretting wear test rig is shown in Fig. 5a. The flat moved up and down with a controlled displacement and rubbed against the stationary cylinder under a given normal force. The normal force was applied with a screw. The oscillating motion was applied with a hydraulic actuator with a sine wave. The extensometer was a commercially available sensor with an accuracy of 0.1 µm, nonlinearity of 0.15%, and hysteresis of less than 0.1%. The displacement δ, normal force P, and tangential force Q were recorded during the test, which enabled us to calculate the friction coefficient (Fridrici, et al. (36)). The geometry of the flat and cylinder samples is shown in Fig. 5b. The diameter of the cylinder was 20 mm, and the contact width was 5 mm.
Numerical and experimental study of multimode failure phenomena in GFRP laminates of different lay-ups
Published in International Journal of Crashworthiness, 2018
Amit Kumar Gupta, R. Velmurugan, Makarand Joshi
All mechanical properties of GFRP were found out as per ASTM standards. Testing was done to find out properties: tensile strength and modulus, compressive strength, shear strength and modulus. Specimens used for tensile testing is of dimension 250 × 15 × 1 mm3 as per ASTM standard D3039. Extensometer was attached to the test specimen to measure strain data which is later on used to calculate the modulus of material. Samples for compressive strength determination were rectangular strips of dimension 140 × 10 × 2 mm3 as per ASTM standard D3410. Similarly, shear strength and shear modulus were found out by making specimens of dimension 120 × 30 × 5 mm3 as per ASTM standard D3251. Interlaminar shear strength of composites was obtained by short beam shear test as per ASTM D2344. Specimens of dimensions 36 mm × 12 mm × 6 mm were subjected to three-point bending.
Plastic hinge integration methods for cyclic analysis of polymer concrete-filled fiber reinforced polymer tube beams
Published in Mechanics of Advanced Materials and Structures, 2020
Vahid Toufigh, Hamid Saadatmanesh, Ali Arzeytoon
Compressive stress-strain behavior of unconfined/confined polymer and cement concrete are determined according to ASTM C39 [19] using MTS 311 with the capacity of 890 kN (200 kip). An extensometer is attached to the specimens for measuring their strain values. The tests have been conducted under a displacement control with 0.025 mm/sec (0.001 in/sec) rate.