Local Buckling Deformation Research Articles

A method for modeling the local and global buckling of delaminated composite plates

An analytical methodology is presented for predicting the buckling initiation of delaminated composite plates. Both global and local sublaminate buckling deformation modes are predicted for rectangular plates of any thickness. The global behavior of the delamination zone is accounted for by summing the individual stiffness contributions of each sublaminate constituting the delamination zone. This allows for the delamination zone to be treated as a single plate when performing global buckling predictions. Local buckling predictions are obtained by modeling a sublaminate adjacent to the surface as a separate elliptical plate. These analytical predictions compare closely with the results of detailed finite element models investigating several cases of delaminated plates. The methodology presented is found to be accurate for the cases considered and versatile as it can accommodate plates of any aspect ratio and having arbitrarily sized and located delaminations.

Mode interaction analysis of stiffened shells using “locally buckled” elements

A novel methodology for the analysis of local and overall instabilities in stiffened plates and shells is proposed. The method consists of embedding the local buckling deformation—the buckling mode together with the associated second order fields—in an appropriate shell element. The local buckling deformation is controlled by a relatively small number of degrees of freedom which also allow for amplitude modulation. Examples of stringer-stiffened plates and shells subjected to axial compression are presented. Excellent agreement is found to exist between the results given by the method and those obtained from full blown nonlinear analysis and experiments. It is shown that the proposed technique offers a simple and considerably less expensive approach to mode interaction problems than conventional nonlinear finite element analysis. Imperfection-sensitivity under coincident buckling of axially compressed stringer-stiffened cylindrical shells is explored and it is shown that there can be an erosion of 50% of the load carrying capacity under imperfections of the kind unavoidable in practice.

A special beam element for the analysis of thin‐walled structural components

AbstractA new beam element is described which is capable of depicting the non‐linear elastic mode interaction of overall bending/buckling with local buckling in thin‐walled beam‐columns. In addition to being capable of describing overall biaxial bending and twisting, the element has shape functions which contain implictly the relevant local buckling deformation. The mode interaction occurs by virtue of the non‐linear coupling of the overall and local buckling deformation. The local and post‐local buckling displacement fields are computed a priori in an efficient manner using the finite strip technique. The modulation of the local buckling amplitudes is also accounted for in the element. In general, the beam element incorporates three companion local modes, all of which may become important in the process of interaction. Examples are presented which illustrate the efficacy of the element for problems involving interaction of local and flexural buckling modes and the combined interaction of local, flexural and flexural‐‐torsional modes.

A versatile model for interactive buckling of columns and beam-columns

A new formulation has been developed to study the interactive buckling of thin-walled columns having arbitrary cross-sections. The emphasis in this paper is, however, on columns with a single axis of symmetry. The formulation is designed to take into account the simultaneous interaction of the purely flexural and flexural-torsional overall modes of buckling with local buckling. The local buckling deformations are described in terms of a primary local mode together with two secondary local modes of the same wavelength. The latter are triggered by the interaction of bending in two perpendicular planes with the primary local mode. The three eigenmodes and the six second-order in-plane displacement fields are all computed using a finite-strip technique. The modulation of the amplitudes of the local modes and the overall displacements are described in terms of a one-dimensional finite element model. Thus a new beam element which has embedded in it the local buckling information is developed. It appears that the present analytical model is very versatile being applicable to members of arbitrary cross-section and end conditions. For columns with a single axis of symmetry, it is seen that there exists a non-linear coupling between the purely flexural and the flexural-torsional modes of buckling via local buckling deformation. Typical examples of channel section columns are presented. It is shown that the channel section columns of commonly used proportions arc highly imperfection sensitive in the context of combined interaction of the enumerated modes of buckling. This sensitivity remains even for columns with well separated overall and local critical stresses—a feature which is in stark contrast with the behavior of the Tvergaard panel.