The elastic rod

Abstract

The form of an elastic rod in equilibrium subject to a buckling by the action of two opposite forces at its ends is explicitly calculated and drawn. The full expression for the radius of curvature in the equation of the beam is considered. It is known that the differential equation describing the form of the rod, written in terms of the arc length and the angle that forms the tangent line to the curve with the horizontal axis of coordinates, is exactly the same one finds in describing the dynamics of great amplitude oscillations of a simple pendulum. This equation is solved exactly in terms of Jacobi's elliptic functions. The solutions are drawn by using in iterated form the addition formulas of those functions. Useful relations among the physical constants of the system and the geometric parameters of the rod are also obtained.