Accession Number : ADP003104

Title :   Applying Molecular Dynamics to Fracture,

Corporate Author : LAWRENCE LIVERMORE NATIONAL LAB CA

Personal Author(s) : Hoover,W. G.

Report Date : OCT 1983

Pagination or Media Count : 10

Abstract : The stress and strain fields of continuum fracture mechanics include unrealistic divergences at crack tips. These divergences can be avoided by using a detailed atomistic description. Such a description automatically characterizes the crack-propagation process. With current computing capabilities there is no difficulty in treating three-dimensional crystal lattices with complicated interparticle forces. In real metals the presence of lattice defects, including the crack tip itself, and the dependence of the forces on these defects preclude quantitative agreement with experiment, so that the computer simulations can be expected to provide understanding of experimental trends rather than replication of experimental results. The experiments described by using shadow patterns to measure the strength of strain fields near moving crack tips, contained interesting time dependent fluctuations. We have made an attempt to understand the structure of the rapidly moving cracks and to simulate the shadow patterns numerically. The particle trajectories are generated using molecular dynamics, and then shadow patterns are developed and compared with experimental results. This work will be described at length in a forthcoming thesis. Here we only outline the methods used, results obtained, and the problems remaining.

Descriptors :   *Metals, *Fracture(Mechanics), *Dynamics, *Equations of motion, Mechanical properties, Stress strain relations, *Strain(Mechanics), Computerized simulation, Crystal lattices, Three dimensional, Defects(Materials), Front ends and surfaces, Patterns, Shadows, Two dimensional, Molecule molecule interactions, Particle trajectories, Cracks, Crack propagation, Stress concentration, Sound waves, Boundaries, Stability, Dynamic loads, Tensile stress, Plastic flow, Computations, Symposia

Distribution Statement : APPROVED FOR PUBLIC RELEASE