Mixed-displacement finite-element analysis with particular application using plane-stress triangles

Abstract

Finite elements which have different displacement functions for each boundary are termed ‘mixed-displacement’ elements. The mixed-displacement approach to finite elements is applied to plane-stress problems in which mixed-strain triangles are formed from the linear-strain triangle. It is shown that by using these triangles in conjunction with existing linear- and constant-strain triangles, higher strain-energy content is produced with fewer active degrees of freedom than are otherwise necessary. A basic triangular grid is first assumed and any number of additional midside nodes can be inserted in regions of high strain gradients. Reference to three-dimensional isoparametric elements is given.