# 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

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

is stationary, where $C$ 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 K. Washizu.

## References

1. ^ Jihuan, He (June 1997). "Equivalent theorem of Hellinger-Reissner and Hu-Washizu variational principles". Journal of Shanghai University (Shanghai University Press) 1 (1). ISSN 1007-6417. Retrieved 2009-09-22.