Kink instability of a highly deformable elastic cylinder

TL;DR

This paper investigates the kink instability in highly deformable elastic cylinders, revealing how critical curvature depends on geometry and how localized curvature leads to kinking, with experimental validation across different cylinder types.

Contribution

It provides a detailed analysis of the conditions and mechanisms leading to kink formation in elastic cylinders, including experimental insights into the effects of geometry and material properties.

Findings

Critical radius increases linearly with diameter

Kinking occurs due to extreme curvature localization

Experiments show kinking and ovalization in annular cylinders

Abstract

When a soft elastic cylinder is bent beyond a critical radius of curvature, a sharp fold in the form of a kink appears at its inner side while the outer side remains smooth. The critical radius increases linearly with the diameter of the cylinder while remaining independent of its elastic modulus, although, its maximum deflection at the location of the kink depends on both the diameter and the modulus of the cylinders. Experiments are done also with annular cylinders of varying wall thickness which exhibits both the kinking and the ovalization of the cross-section. The kinking phenomenon appears to occur by extreme localization of curvature at the inner side of a post-buckled cylinder.