Determination of overall factor of safety of a design involves repeated calculation of factor of safety at critical points in the design. For a given stress state at a point, the factor of safety is calculated by first finding the principal stresses and then comparing them with the maximum safe stress that can be applied without causing failure of the material according to an appropriate failure theory. In this paper, we suggest quick and ready-to-use expressions and graphs for calculating factor of safety for biaxial stress states for a number of commonly-used failure theories. These graphs can be directly used as design charts for computing factor of safety in engineering design activities.

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