Papers by Keyword: Peierls Stress

Abstract: The calculation of generalized stacking fault energy for covalent materials exists several relaxation methods. And the modification factor of the restoring force should be different for different relaxation. In order to study the impact of generalized stacking fault energy on the mechanical properties of dislocations, the dislocation energy, Peierls barrier and Peierls stress of shuffle dislocation in zigzag single-walled carbon nanotube (SWCNT) under different modification factors are studied by the improved Peierls-Nabarro (P-N) theory. It is found that the misfit energies decreased, and the strain and total energies increased with increasing of the modification factor Δ. With the modification factor Δ of the restoring force changes from -0.2 to 0.5, the dislocation energy changes from 17.4eV to 19.3eV. The Peierls barriers E_p and σ_p Peierls stresses increased first and then decreased and the results are not as same as we thought. The impact of generalized stacking fault energy on mechanical properties of dislocations is not so simple as we thought and need to be further studied.

Abstract: The paper discusses issues related to the damage accumulation and cracking in steels. Special attention is paid to the selection of appropriate methods in the modeling of progressive damage development. In special cases, the accumulation of damage and crack propagation may lead to the brutal destruction of machine parts. In addition, some attention was drawn to the conditions that can lead to this brutal destruction.

Abstract: Peierls stresses P of a variety of pure crystals, bcc metals, NaCl type crystals, elemental and compound tetrahedrally coordinated crystals, intermetallic compounds and ceramic crystals, have been estimated from the critical resolved shear stress (c) vs. temperature curves. For high P crystals where CRSS data are available only at high temperatures, P has been estimated from the critical temperature T0 at which steep temperature dependence of c vanishes: T0 is related to the kink-pair formation energy which is a function of P, material parameters and dislocation character controlling the deformation. The estimated p/G values are semi-log plotted against h/b value, where G is the shear modulus, h the slip plane spacing and b the Burgers vector. Two facts should be noted. First, P/G values for a group of crystals with the same crystal structure are within a range of a factor of 10. Second, most of the data points lie in between the classical Peierls-Nabarro relation and the Huntington’s modified relation. These facts indicates that Peierls stress is primarily determined by the crystal structure.

Abstract: The applications of ab initio calculations for deformation mechanisms of Mg-based alloys are discussed. First, Peierls stress of pure magnesium is calculated from generalized stacking fault (GSF) energies obtained by ab initio calculations. Second, materials design is applied to develop new Mg-based alloys exhibiting high strength. The atomic size factors of some Mg-based solid solutions are calculated by ab initio calculations as a first step of searching most effective solute element for the solid-solution strengthening.