## Experiments on snap buckling, hysteresis and loop formation in twisted rods

V.G.A. Goss, G.H.M. van der Heijden, J.M.T. Thompson & S. Neukirch

We give results of large deflection experiments involving the bending and
twisting of 1 mm diameter nickel-titanium alloy rods, up to 2 m in length.
These results are compared to calculations based on the Cosserat theory of
rods. Details of this theory, formulated as a boundary value problem are
presented. The mathematical boundary conditions model the experimental setup.
The rods are clamped in aligned chucks and the experiments are carried out
under rigid loading conditions. An experiment proceeds by either twisting
the ends of the rod and then adjusting the amount of slack, or fixing the
slack and varying the amount of twist. In this way commonly encountered
phenomena such as snap-buckling, the formation of loops, and buckling into
and out of planar configurations are investigated. The effect of gravity
is discussed.
keywords: twisted rods, rod experiments, snap buckling, loop formation,
snarling, hockling, welded boundary conditions

*Experimental Mechanics* **45**, 101-111 (2005)