During the creep process, formation and growth of cavities occurs. In the tertiary creep stage this phenomenon occurs at an accelerated rate, depending strongly on the mean stress. However, various constitutive creep laws such as θ projection take into account only the deviatoric part of the stress tensor. Therefore, a modified θ projection concept is proposed by introducing a thermodynamlcally sound term whlch accounts for mean stress in the θ4 rate parameter.
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