# engr 244 lab 3.docx - Objective The objective of this...

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Objective:The objective of this experiment is to determine the shear modulus of steel, aluminum, and brass using the torsion testing machine.Introduction:The torsion test is a test that takes a rod of a certain material and applies a twisting motion at both ends in opposite directions. It is used to determine the shear modulus, also known as the modulus of rigidity, which tells us how elastic a material is when under shearing stress. This test allows engineers to make informed decision when deciding what kind of materials to use when designing a building. In this experiment, three specimens (steel, aluminum, and brass) will have a torque applied at each end in opposite direction for a certain amount of time. From this test, thetorque, the time when the torques was applied, and the angle in degrees will be recorded. With this information the polar moment of inertia and the shear modulus can be calculated using the following formulas:J=(π D4)32Where, J is the polar moment of inertia [mm4]D is the average diameter of the specimen [mm]G=TLθJWhere, G is the shear modulus [GPa]T is the torque [N-m]L is the gauge length [mm]θ is the angle of twist [rad]J is the polar moment of inertia [mm4]