Theory of regular arrays of defects: The void lattice
Defects in crystals may form a regular array, rather than a random distribution. The lattice of voids produced in irradiated molybdenum is a remarkable example of this. We give a general method of calculating the energy per defect in the array which exploits the periodicity of the defect lattice. The existence of the void lattice depends on the elastic interaction between voids. The present approach can treat both arbitrarily anisotropic elastic continua and discrete lattices, and is readily extended to discuss the stability of the defect lattice. The results predict that a void lattice should occur in molybdenum, and compare a number of models for the void. Stability against shear of the void lattice is not discussed in the present paper. The ratio of the void lattice spacing to void radius predicted is 2.2 to 4.5 and is smaller than the value of about 10 observed. The results are in general agreement with the more approximate Malen-Bullough treatment.
The energy of helium filled platelets and bubbles in molybdenum
Abstract Theoretical models are developed to describe the observed behaviour of helium platelets in molybdenum, which grow and then collapse into clusters of bubbles. Firstly a fully dynamic simulation of helium in a two-dimensional structure is performed. Then simplified models of platelets and bubbles filled with helium are discussed, the calculated energies of which indicate that platelets should be higher in energy for 3 He/vacancy. A cluster of several bubbles is shown, under conditions of high internal pressure, to be of lower energy than a single large bubble due to the elastic interaction between bubbles on the assumption that this is approximately the same in magnitude as for the void lattice.
Finite Difference Modeling on the Temperature Field of Substrate in Friction Surfacing
Friction surfacing is an advanced process of great potential, especially in the field of repair and reclamation of worn and damaged components. As a kind of thermal processing technology, the temperature profile and changes of the substrate in friction surfacing are important factors to get coatings of high quality. In this paper, the temperature field of the substrate during the process is simulated by finite difference method. The results are consistent with experiments, reappearing the temperature change of the substrate during friction surfacing, allowing further study on figuration and quality of coatings.