Shear Modulus - The bigger the shear modulus the more rigid...

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SHEAR MODULUS The shear modulus is the elastic modulus we use for the deformation which takes place when a force is applied parallel to one face of the object while the opposite face is held fixed by another equal force. When an object like a block of height L and cross section A experiences a force F parallel to one face, the sheared face will move a distance x . The shear stress is defined as the magnitude of the force per unit cross-sectional area of the face being sheared ( F/A ). The shear strain is defined as x/L . The shear modulus S is defined as the ratio of the stress to the strain. ) ( x A L F L x A F strain stress Pascals are units = = S shear shear
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Unformatted text preview: The bigger the shear modulus the more rigid is the material since for the same change in horizontal distance (strain) you will need a bigger force (stress). This is why the shear modulus is sometimes called the modulus of rigidity. To a first approximation there is no change in volume in this deformation. The planes of atoms merely slide sideways over one another. That is why the area A (which determines the number of atomic bonds) is important in defining the stress and not just F . Note that in the diagram, since the block is not moving, there is a force F to the left on the bottom face which is not shown....
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This note was uploaded on 02/03/2011 for the course CE 573 taught by Professor Various during the Spring '11 term at American University of Science & Tech.

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