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Unformatted text preview: 1 Combined Stresses and Mohrs Circle Material in this lecture was taken from chapter 4 of Mot , Machine Elements in Mechanical Design, 2003 General Case of Combined Stresses Twodimensional stress condition Mot , Machine Elements in Mechanical Design, 2003 General Case of Combined Stresses cont The normal stresses, x and 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 doublesubscript notation helps to orient the direction of shear stresses. For example, xy indicates the shear stress acting on the element face that is perpendicular to the x axis and parallel to the yaxis. 2 General Case of Combined Stresses cont A positive shear stress is one that tends to rotate the stress element clockwise In the first figure, xy is positive and 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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 Fall '09

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