Hu–Washizu principle

In continuum mechanics, and in particular in finite element analysis, the Hu–Washizu principle is a variational principle which says that the action

${\displaystyle \int _{V^{e}}\left[{\frac {1}{2}}\varepsilon ^{T}C\varepsilon -\sigma ^{T}\varepsilon +\sigma ^{T}(\nabla u)-{\bar {p}}^{T}u\right]dV-\int _{S_{\sigma }^{e}}{\bar {T}}^{T}u\ dS}$

is stationary, where ${\displaystyle C}$ is the elastic stiffness tensor. The Hu–Washizu principle is used to develop mixed finite element methods.[1] The principle is named after Hu Haichang and Kyūichirō Washizu.