\[\dot f = \sum_{i,j=1}^3 \frac{\partial f}{\partial \sigma_{ij}} \dot{\sigma_{ij}} + \sum_{i,j=1}^3 \frac{\partial f}{\partial \sigma_{ij}} \dot{\sigma_{ij}} - \frac{d\sigma_{Y\alpha}}{d\overline{\varepsilon^p}} \dot{\overline{\varepsilon^p}} = 0\]