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A Schmidt hammer, [1] also known as a Swiss hammer or a rebound hammer or concrete hammer test, is a device to measure the elastic properties or strength of concrete or rock [2], mainly surface hardness and penetration resistance. It was invented by Ernst Heinrich Wilhelm Schmidt, a Swiss engineer. [3]
These secondary cracks can grow to as long as 10-15 times the length of the original cracks in simple (uniaxial) compression. However, if a transverse compressive load is applied. The growth is limited to a few integer multiples of the original crack's length. [9] A secondary crack growing from the tip of a preexisting crack shear band formation
A dead-blow hammer is a specialized mallet helpful in minimizing damage to the struck surface and in controlling striking force, with minimal rebound from the struck surface. The minimal rebound is helpful in avoiding accidental damage to precision work, especially in tight locations and in applications such as maintenance work on hydraulic ...
The portion of the beam that is in tension may crack. The size and length of cracks is dependent on the magnitude of the bending moment and the design of the reinforcing in the beam at the point under consideration. Reinforced concrete beams are designed to crack in tension rather than in compression.
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The specimen is placed on the work table and a notch is created exactly at the centre. The crack should be generated such that the defect length is about half the depth. The load applied on the specimen is generally a three-point bending load. A type of strain gauge called a crack-mouth clip gage is used to measure the crack opening. [3]
The energy transferred to the material can be inferred by comparing the difference in the height of the hammer before and after the fracture (energy absorbed by the fracture event). The notch in the sample affects the results of the impact test, [ 6 ] thus it is necessary for the notch to be of regular dimensions and geometry.
A procedure for ultrasonic testing is outlined in ASTM C597 - 09. [9]In India, till 2018 ultrasonic testing was conducted according to IS 13311-1992.From 2018, procedure and specification for Ultrasonic pulse velocity test is outlined in IS 516 Part 5:Non destructive testing of concrete Section 1:Ultrasonic Pulse Velocity Testing.