Selected problems concerning the analysis of thin-walled structures with the use of finite element method

Abstract

The aim of the paper was presentation and comparison of numerical methods applied in thin-walled structures analysis, with special attention paid to possibility of usage the Finite Element Method (FEM), especially in nonlinear analysis. There were presented basic differences between classical approach to modelling and analyzing thin-walled structures, and these performed with FEM methods using. The biggest emphasis was placed on the analysis of semimonocoąues, in which the loss in the shell 's stability is possible in the range of operational load activity. According to this, many nonlinear terms like global and local buckling, contact problems, significant deformations and shifts, are present. Worth emphasizing is the fact, that tension field, is something that was described long time ago. First paper s about this phenomenon were published in the last century. Although it is a common effect that takes place in semimonocoques, there are not many publications that analyze and examine this phenomenon. In this paper, an analysis of two-sided, thin-walled spar, which has undergone the flexion by the shearing force in the plane of the panel, was presented. The spar was designed as a classic semimonocoque, in which load transmission function is separated. It was assumed that, for the sake of small thickness, shell elements transmit mainly tangential loads, normal loads, when normal loads are transmitted by framework elements. Riveted joints are used to join elements of framework and shell. There are presented and compared results of analysis for models with various complexities. Firstly, results of analysis of classical model of semimonocoques were presented. It means that framework elements were modelled as rod elements transmitted only normal loads, but shell elements were modelled as disc semimonocoque elements, in this case transmitted only tangential loads. Area of section of rod elements was adequately increased, in order to consideration mating width, coming from partial transmission of normal loads by the shell elements. Results obtained for intermediate models were also presented, as well as for complex shell model, which allows on advanced nonlinear analysis of tension field, which consider contact between framework and shell elements. Applications of formulated models to thin-walled structure, especially aircraft ones and further possibilities of presented method of analysis were discussed