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Unformatted text preview: EAS 209 – Spring 2008 Instructor: Human/Mosqueda 1/15/2008 1 Lecture 03 Lecture 3 – Normal Stress and Shear Stress So far we have discussed the effects of normal stresses produced by axial loads acting on prismatic bars. The stresses are called normal stresses because they act in a direction perpendicular to the surface of the material. We will now consider another kind of stress, shear stress , which acts tangential to the surface of the material. EAS 209 – Spring 2008 Instructor: Human/Mosqueda 1/15/2008 2 Lecture 03 Shearing Stresses Forces P and P’ are applied transversely to the member The corresponding internal force is called a shear force The shear force normalized by the area is the shear stress: A P = τ Shear stress distribution Average shear stress, A P ave = τ We use ave τ even though the stress distribution is not uniform At edge = τ max τ EAS 209 – Spring 2008 Instructor: Human/Mosqueda 1/15/2008 3 Lecture 03 Shearing Stresses in Bolts Shear failure results in failure of the bolt Double Shear (two shear surfaces) bolt bolt A F A P 2 ave = = τ Single Shear (one shear surface) bolt bolt A F A P = = ave τ Shear force across bolt EAS 209 – Spring 2008 Instructor: Human/Mosqueda 1/15/2008 4 Lecture 03 Bearing Stress in Connections • Bolts, rivets, and pins create stresses on the points of contact or bearing surfaces of the members they connect. • These are called bearing stresses, σ b . b b A P = σ where A b = bearing area (projected area) =bolt dia. x thickness of plate = d x t ¡ A bearing failure is failure of the material being connected (not the bolt), and is characterized by elongation of the bolt hole EAS 209 – Spring 2008...
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 Spring '08
 Force, Shear Stress

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