MEASUREMENT OF PLASTICITY 1

ABSTRACT The object of this investigation was to devise a rational method and primary standard for measuring plasticity. Various methods suggested in the past were critically examined and found wanting. An apparatus was developed to measure the stress‐strain relations of clays in shear and a few typical clays have been examined by this method. A definition is proposed for the unit of plasticity as follows: Index of plasticity = Total deformation at fracture in shear / Average stress beyond proportional limit The effect of addition of sand and powdered graphite has been noted and throws some light on the nature of plastic deformation.