In recent years, flexible materials with very high performance are widely used and large deformation analyses of these materials have attracted considerable attention. However, there is not sufficient analysis for problems of practical interest such as large deformation of a cable within a channel (or a pipe), or of a drill within a hole in rock engineering and petroleum production, or of a catheter within a blood vessel, and so on. When a lightweight, flexible material must be pushed through the narrow space, it is possible for the materials to buckle since the leading edge of the material strikes an obstacle (or a barrier) and cannot proceed any further. The postbuckled configuration, namely large deformation, will be thus of great concern in handling these flexible materials. This paper deals with the postbuckling behavior of a flexible elastic beam contained within rigid, parallel walls with friction under the action of axial compressive forces at each end. Different contact stages between the beam and the walls are modelled using the nonlinear deformation theory. The theory of the elastica is applied and exact analytical solutions for large deformation are derived in terms of elliptic integrals, and then nondimensionalized. As an example of such results, the sequence of large deformation are illustrated through which the postbuckled beam passes. In this study, some experiments of flexible elastic beams were presented and the experimental results were compared with the theoretical formulas. As a result, the relation between the applied axial force and the beam length, obtained from the experiments, is similar to that predicted by the analytical theory. Moreover, it is made clear that the existence of friction between the beam and the wall causes a nonuniform buckled configuration. The analysis presented in this paper would have application to the design of machinery for handling flexible elastic materials such as sheets, tapes, films, papers, cloths and so on. In addition, designers of machines such as drill or tubing strings, sewing machines and medical instruments should find the results useful and easy to apply.
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