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Unformatted text preview: 1 Combined Stresses and Mohr’s Circle Material in this lecture was taken from chapter 4 of Mot , Machine Elements in Mechanical Design, 2003 General Case of Combined Stresses ¡ Two-dimensional stress condition Mot , Machine Elements in Mechanical Design, 2003 General Case of Combined Stresses con’t ¡ The normal stresses, σ x and σ y , could be due to a direct tensile force or to bending. If the normal stresses were compressive (negative), the vectors would be pointing in the opposite sense, into the stress element. ¡ The shear stress could be due to direct shear, torsional shear, or vertical shear stress. The double-subscript notation helps to orient the direction of shear stresses. For example, τ xy indicates the shear stress acting on the element face that is perpendicular to the x- axis and parallel to the y-axis. 2 General Case of Combined Stresses con’t ¡ A positive shear stress is one that tends to rotate the stress element clockwise ¡ In the first figure, τ xy is positive and τ yx is negative. Their magnitudes must be equal to maintain the element in equilibrium. ¡ With the stress element defined, the objectives of the remaining analysis are to determine the maximum normal stress, and the planes on which these stresses occur....
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This document was uploaded on 11/21/2011.
- Fall '09