On the changes in the dimensions of a steel wire when twisted, and on the pressure of distortional waves in steel

Abstract

In the Proceedings of the Royal Society there is an account of some experiments which I made to show that wires when twisted lengthen by an amount proportional to the square of the angle of twist, a result expected from an analysis of the strains in a finite pure shear. In those experiments it was necessary to put considerable loads on the wires. I have now succeeded in measuring the change in the diameter of a wire when twisted, as well as the longitudinal extension, and have found that the change, a contraction, is also proportional to the square of the angle of twist. It has been now found that the changes is sensibly the same for large loads and for the smallest load which could be used, when the wire was sufficiently straightened before being twisted, so that apparently the only function of the load is to straighten the wire.