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BACKGROUND
Shear stress is defined as the shear force which acts on a particular area and it is responsible for causing a deformation of material through motion along the plane or a no. of planes operating parallel to the applied stress. Shear stress eventuates in either solid or a liquid; it acts as a parallel force to the surface in solid materials whereas, it is related to fluid viscosity in liquid.
Along with a bending moment, shear stress always comes to act when a beam is loaded.1 However, the effect of shear stress is negligible in comparison to bending stress. But in design calculation, the shear stress sometimes shows the utmost importance as it is responsible for the breakdown of an object. This test is known as a double shear test because the sample is operated under load from both sides until it shears.
Universal Testing Machine is used for determining tensile, compression, bending, and shear stress. UTM is divided into a screw type, and hydraulic type where the hydraulic one is easier to operate and they have a testing and control unit which is connected through a hydraulic pipe.2
The chief objective of this experiment is to perform a double shear test in the universal testing machine.
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REQUIREMENTS
Materials: Universal Testing Machine
Shear test attachments
Specimens
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PROCEDURE
First of all, insert the sample in a position in such a way that one end of the attachment is gripped in the upper portion while the other end is gripped in the lower division. Then, switch ON the main switch of UTM and so that the drag indicator comes in contact with the leading indicator. Now select the suitable range of loads corresponding to the weight in pendulum and balance it with the help of small balancing weights. The pump is operated through motors which are connected to buttons. Now slowly progress the head-control level in left direction until the specimen shears. Then, note down the load at which the sample shears to determine the shear strength of a material.
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CONCLUSION
The process of finding double shearing strength of a material through Universal Testing Machine is discussed. Shears strength varies from one material to another material depending upon its mechanical properties.
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REFERENCES
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H. Neuber, “Theory of Stress Concentration for Shear-Strained Prismatical Bodies With Arbitrary Nonlinear Stress-Strain Law,” Technical university, Munich, Grermany, Munich, 2003.
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J. Amsler. US Patent US1865070A, 1929.
