A new theory for the prediction of multiaxial strength of anistropic elasto
plastic materials is proposed. The resulting failure envelope, in a multidi
mensional stress space, is piecewise smooth. Each facet of the envelope is
expected to represent the locus of failure data by a particular anisotropic
elastic deformation mode called a Kelvin mode. It is shown that the Kelvin
mode theory alone provides an incomplete description of the failure of som
e materials, but that this weakness can be addressed by the introduction of
a set of complementary modes. A revised theory which combines both Kelvin
and complementary modes is developed and illustrated by an applied example.
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