Investigation of proportional and non-proportional loadings using Mohr's circle

Abstract

For time varying loads, proportional loading refers to the cases where the principal stresses maintain constant directions and constant ratios of their values; otherwise it is non-proportional. Non-proportional loadings are especially important in the design and analysis of automotive components such as crankshafts and connecting rods. It is important to understand how external bending and torsion loads combine to form various mixes of normal and shear stresses. In particular, the principal stresses play an important role in predicting material failure under static and dynamic loads. Mohr's circle is an invaluable tool in its ability to determine the principal stresses and the associated principal directions. The features of proportional and nonproportional loadings have been exemplified in this paper by studying the stresses in a shaft under combined bending and torsion using Mohr's circle. © 2012 American Society for Engineering Education.