Common stress recovery methods usually cannot introduce the stress boundary
conditions. The general mixed finite element method can only solve the whole model
and its calculation requires large memory resources. A stress recovery method using
generalized mixed elements in a local model is proposed in this paper. The elements
surrounding some nodes where stress results are required are selected to
construct a local noncompatible generalized mixed element model, which is
used to introduce the stress boundary conditions in the local model. For the
problem of composite structures, the modified generalized mixed variational
principle is used to obtain the solution equation of out-plane stress, and then
the local models for the linear system of in-plane stress are constructed
according to different material layers. The continuous results of in-plane stress in
each layer of material can be obtained, and the discontinuity of in-plane
stress at the interface of each material layer is ensured at the same time.
Numerical examples show that this method can obtain objective and more
accurate stress results. Compared with the mixed finite element method
for whole model, the present method greatly improves the computational
efficiency.
Keywords
displacement finite element, stress recovery, composite
laminates, generalized mixed variational principle, local
model