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Unformatted text preview: ME313 LABORATORY EXPERIMENTS BEAM BENDING EXPERIMENTSOBJECTIVE: The objective of these experiments is to measure the surface stresses and deflections of beams and compare them with theoretical values. BACKGROUND: A beam is a long structural member, which is subjected to loads perpendicular to its long dimension. The beam bends under the applied load. The applied load is supported by the stresses that develop in the beam as a result of bending. Consider a beam, which is supported at its ends by rollers and subject to a single point downward load at its midlength. As a result of the bending, fibers on the top surface are compressed and those on the bottom surface are extended. There is a linear variation of strain from the top to the bottom surface. Assuming a linear elastic behavior of the material, the stress also varies linearly from a compressive stress on the top surface to a tensile stress on the bottom surface. The magnitude of axial stress (σx) at any point along the beam depends on the bending moment (M) at that point, the distance (y) of the point from the neutral axis and the moment of inertia (I) of the crosssection about the neutral axis. For a rectangular cross section beam, the magnitude of axial stress at the surface is, IMcx=σwhere c is half the height of the beam. The downward deflection of points along the length of the beam varies from no deflection at the points of support to a maximum at midspan. The magnitude of the maximum deflection δis a function of the applied load (P), the length of the beam between the supports (L), the Young's Modulus (E) of the material and moment of inertia (I) of the cross section....
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This lab report was uploaded on 04/09/2008 for the course ENGR 3323 taught by Professor Lee during the Spring '08 term at LeTourneau.
 Spring '08
 Lee
 Stress

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