Defect and Diffusion Forum Vol. 294

Abstract: A pseudopotential approach has been used to study the variation of the vacancy formation energy as a function of the parameter of Ashcroft's empty core model potential (AECMP) and nine different exchange and correlation functions (ECF) for some trivalent fcc metals, viz. Al, La, Sc, γ-Ce, Pr and Yb. The criterion used is that should be greater than the Bohr radius ( ). There is a systematic increase in the fitted value of in going from one ECF to another, as follows: KK < Sham < GV < Kle < Harr < VS < Tay < Hub < MD and it is difficult to assign a particular value of for all ECFs for a particular trivalent fcc metal. The inherent simplicity of AECMP makes it difficult to have a universal parameter for all types of atomic property calculations.

Abstract: In the present work, an experimental study of the influence of tribological parameters upon the mechanical wear behavior of unalloyed and high-alloy steels is proposed, in order to monitor the residual stress evolution as a function of the friction coefficient. For both types of steel, the tests are carried out on specimens polished mechanically or chemically. The dry friction tests were performed on a ball-on-plate testing machine in order to determine the cyclical friction coefficient and the residual stresses developed during the slip of the tempered steel wiper on the specimen. Using the data analysis technique, the correspondence factorial analysis method describes more quickly a large data source by exploiting sophisticated descriptive statistics. The data will are then subjected to a factorial treatment using the metric of Chi-squared (2c) to preserve the probabilistic nature of the problem. This method is considered to be very useful and very precise for determining the residual stress under the cyclical loading caused by dry mechanical friction.