How do you test a structure for Von Mises stress?


Quick Answer

To test a structure using the Von Mises criterion, it is important to know the material's yield strength and the normal stresses acting on the structure. Once these values are determined, calculate the Von Mises stress using the Von Mises expression, and compare it against the value of the yield strength.

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Full Answer

  1. Determine the yield strength

    Find the yield strength of the structure's material by locating the point on a stress-strain diagram where plastic deformation begins. The value of the yield strength for many materials is available online.

  2. Find the principal stresses

    Find the normal stresses acting on the structure along the x, y and z-axes, and use these values to determine the principal stresses. These principal stresses are labelled sigma-1, sigma-2 and sigma-3.

  3. Calculate the Von Mises stress

    Use the values of the principal stresses to find the Von Mises stress. The expression for this is: sigma-v = sqrt[((sigma-1 - sigma-2)^2 + (sigma-2 - sigma-3)^2 + (sigma-3 - sigma-1)^2) / 2]

  4. Compare the values

    Compare the value of the Von Mises stress to the value of the material's yield strength. The structure is a failure if the Von Mises stress is greater than the yield strength, and is safe if it is under the yield strength.

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