Despite all the efforts that have been put toward the study of plastic deformations in the past 81 years, there is currently no generally accepted theory explaining all aspects of it; finding a theory of work hardening is now as hopeless as ever, and research is aimed at establishing a model instead [1].

Eighty Years of Dislocation Theory and Work Hardening

Submitted by Kamyar M Davoudi on Sat, 02/08/2014 - 07:50

work hardening

dislocation theory

On February 7, 1934, two consecutive papers by Sir Geoffrey Ingram Taylor were received and so the dislocation theory was born and the first attempt at describing work hardening was made. Before that date, it was known that there was a big gap between the ideal and the experimentally observed shear strength. While according to the calculations, the shear strength had to be of the order of one tenth (or with finer models one thirtieth) of the shear modulus, the measured shear strength was several orders of magnitude smaller. This large discrepancy brought about Geoffrey I.Taylor, Egon Orowan and Michael Polyani to independently postulate the existence of dislocations. Papers by Orowan and Polyani were published consecutively in one volume of Zeitschrift für Physik.

Dislocation Climb in Two-Dimensional Discrete Dislocation Dynamics

Submitted by Kamyar M Davoudi on Fri, 12/14/2012 - 15:14

discrete dislocation dynamics

In this paper, dislocation climb is incorporated in a two-dimensional discrete dislocation dynamics model. Calculations are carried out for polycrystalline thin films, passivated on one or both surfaces. Climb allows dislocations to escape from dislocation pile-ups and reduces the strain-hardening rate, especially for fully passivated films. Within the framework of this model, climb modifies the dislocation structures that develop during plastic deformation and results in the formation of pile-ups on slip planes that do not contain any dislocation sources.

Some books on Fracture Mechanics

Submitted by Kamyar M Davoudi on Sun, 03/07/2010 - 06:26

Fracture Mechanics, Fundamentals and Applications, T.L. Anderson, CRC Press, 3rd Ed., 2004.

This book is in line with what Zhigang is teaching in class. Because Kejie and Widusha have already recommended this book, I would like to introduce you some other books as well as a different approach to cracks and Fracture Mechanics.

Decomposition of the displacement gradient into elastic and plastic parts

Submitted by Kamyar M Davoudi on Thu, 10/16/2008 - 21:38

We know that total strain is the symmetric part of the displacement gradient. Total strain can be represented by the sum of the elastic and plastic (eigen) strains. Let consider a dislocation in an arbitrary solid. Suppose we computed the displacement filed, therefore the total strain can be obtained immediately. What are the criteria for the decomposition of the total strain into elastic and plastic parts?

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