A truss element for modelling reversible softening in living tissues

We resort to non-linear viscoelasticity to develop a truss element able to model reversible softening in lung epithelial tissues undergoing transient stretch. Such a Maxwell truss element is built by resorting to a three-noded element whose mid-node is kinematically constrained to remain on the line connecting the end-nodes. The whole mechanical system undergoes an additive decomposition of the strains along the truss direction where the total contribution of the mid-node is accounted for by using a null-space projection and static condensation techniques. Assembling of such line-elements in 3D networks allows us to model extended regions of living tissues as well as their anisotropies.

► Two noded Maxwell truss element that can handle non-linear viscosity and elasticity.
► Arbitrary elastic and viscous laws can be inserted in an independent manner.
► The method is based on null-space projection and static condensation.
► The element can qualitatively model reversible softening and fluidisation.