An efficient axisymmetric hybrid-stress-displacement formulation for compressible/nearly incompressible material

Based on Spilker's concept, an efficient four-noded quadrilateral hybrid-st ress-displacement axisymmetric element is developed for mechanical, thermal and body force loads. The present finite element has several advantages co mpared to the familiar displacement formulation for examining the structura l behaviour of compressible/nearly incompressible solid rocket motor propel lant and insulation materials, under various loading environments. Several structural problems are solved to demonstrate the efficiency of the present method, by comparing the results with those obtained from the existing ana lytical and other finite element solutions based on displacement formulatio n, using the MARC software package. The Hermann element in MARC has mean pr essure as one of the nodal degrees of freedom with the other two degrees of freedom tied at the interface. The present element has only two degrees of freedom per node and there is no necessity of tying. Also, the present ele ment gives accurate results even with a coarse mesh compared to MARC. (C) 2 001 Elsevier Science Ltd. All rights reserved.