Abstract
Most of the design codes use certain equivalent values to predict multiaxial fatigue life, like von Mises and Tresca equivalent stresses and strains, because of their simplicity and easiness to use. However, von Mises equivalent stress and strain have no negative values so that they have a difficulty to express stress and strain ranges. The Tresca equivalent values, on the other hand, have negative values but they also have a difficulty to put a sign to the shear stress and strain under multiaxial loading. A clear procedure for calculating the stress and strain is needed for the multiaxial fatigue design for structural components. This paper proposes a method for determining the principal stress and strain ranges under proportional and nonproportional loading in triaxial stress and strain states introducing an angle rotation of the maximum principal stress and strain.
