Visualisation of a Cauchy stress tensor σ in the Haight-Westergaard stress space

In continuum mechanics, Haigh–Westergaard stress space, or simply stress space is a 3-dimensional space in which the three spatial axes represent the three principal stresses of a body subject to stress. This space is named after Bernard Haigh and Harold M. Westergaard.

In mathematical terms, H-W space can also be interpreted (understood) as a set of numerical markers of stress tensors orbits (with respect to proper rotations group – special orthogonal group SO3); every point of H-W space represents one orbit.^[1]

Functions of the principal stresses, such as the yield function, can be represented by surfaces in 'stress space. In particular, the surface represented by von Mises yield function is a right circular cylinder, equiaxial to each of the three stress axes.

In 2-dimensional models, stress space reduces to a plane and the von Mises yield surface reduces to an ellipse.

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