Internal Forces

The internal force vector is given by:(1)

f^{int} = \int_{Ω e} B^{t} σ d Ω^{e}

$f^{int} = \int_{Ω e} B^{t} σ d Ω^{e}$

In elasticity it becomes:(2)

f^{int} = \int_{Ω e} B^{t} C B v d Ω^{e}

$f^{int} = \int_{Ω e} B^{t} C B v d Ω^{e}$

It can be written as:(3)

f^{int} = f^{int}^{0} + f^{{int}^{h g r}}

$f^{int} = f^{int}^{0} + f^{{int}^{h g r}}$

with the constant part $f^{int}^{0}$ $f^{int}^{0}$ being computed with one-point quadrature and the non constant part or hourglass part $f^{{int}^{h g r}}$ $f^{{int}^{h g r}}$ being computed by perturbation stabilization (I_shell = 1, 2 ,3 ...) or by physical stabilization (I_shell = 22).