ABSTRACT
Prandtl, Dehlinger and Yamaguchi foreshadowed the concept of a crystal dislocation as the mechanism of plastic deformation. This chapter provides a number of investigations, experimental and theoretical, which came tantalizingly close to the basic idea of a crystal dislocation, so that, by 1907, dislocations had been observed in the bulk of a crystal, their elastic theory was fully developed, their relation to crystal growth and etching had been studied in detail, and there were speculations on their mobility. It considers the climate of thought at the time the classical papers were being written, adding a little to the personal accounts of Orowan and Taylor. While Taylor’s considerations were purely mechanical, those of Orowan stemmed from the thermodynamic arguments of Becker. Orowan’s assumption that the motion of a dislocation would require thermal activation is compatible with this estimated flow stress, which is much higher than the stresses which are applied in practice.
