young'smodulus - 2 Youngs Modulus 1. Purpose To study the...

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2 Page 1 1. Purpose To study the changes in length of a wire under load. To measure Young’ s modulus, and to investigate the inelastic region. 2. Theory All materials are deformed to a greater or lesser extent by the application of stress. (Stress being deFned as force per unit area). If the deformation (change of shape) disappears as the stress is removed the material is said to be ‘elastic’. If the deformation is proportional to the magnitude of the applied stress, as is commonly true for most materials at sufFciently small stresses, the material is said to obey Hooke’s law (Robert Hooke 1635 to 1703). Many materials, which behave elastically at reasonably small stresses, show inelastic behaviour if the stress exceeds a certain limiting value known then as the “elastic limit”. A material subjected to a stress exceeding the elastic limit will not return to its original shape when stress is removed but is permanently deformed. The behaviour of any particular material under stress depends on a number of factors of which the type of bonding force between the atoms or molecules of the solid material is probably the most important. ±or metals these forces are strong (metals tend to be hard materials) but because of the non directional nature of this force, considerable inelastic or plastic, deformation is possible, the planes of atoms slipping over one another. ±urther discussion of material properties and interatomic bonding will be found in elementary books on solids.
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This note was uploaded on 09/20/2011 for the course SCIENCE PHY1321 taught by Professor Andraj during the Spring '08 term at University of Ottawa.

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young'smodulus - 2 Youngs Modulus 1. Purpose To study the...

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