Accession Number : ADP003109

Title :   Some Theoretical Results on the Dependence of Dynamic Stress Intensity Factor on Crack Tip Speed,

Corporate Author : BROWN UNIV PROVIDENCE RI DIV OF ENGINEERING

Personal Author(s) : Freund,L. B.

Report Date : OCT 1983

Pagination or Media Count : 8

Abstract : Two specific topics are discussed under this common heading. The first is concerned with elastic-plastic crack growth and, in particular, with developing theoretical models to explain the dependence of dynamic fracture toughness on crack tip speed observed for 4340 steel and other high strength, low ductility materials which fail in a locally ductile manner. The second topic is concerned with limitations on the use of crack tip singular fields to describe actual stresses in elastic brittle materials during dynamic fracture. The problem discussed is the steady-state growth of a crack in the antiplane shear mode under small scale yielding conditions. Inertial resistance of the material is taken into account explicitly but, for steady state growth, the deformation is time independent as viewed by an observer fixed at the moving crack tip. Results are considered for two material models, elastic-ideally plastic and elastic-viscoplastic. According to the small scale yielding hypothesis, the (possibly nonlinear) crack tip stress and deformation fields are controlled by the surrounding elastic field. The commonly used measure of this surrounding field, for any given crack tip speed v, is the linear elastic stress intensity factor K. For present purposes, the value of the stress intensity factor is assumed to be known in terms of the body geometry and applied loads from a suitable elastic crack problem.

Descriptors :   *Steel, *Stress concentration, *Cracks, *Fracture(Mechanics), *Dynamic loads, Crack propagation, Time dependence, Ductility, High strength, Elastic properties, Shear properties, Plastic deformation, Steady state, Brittleness, Velocity, Front ends and surfaces, Stress analysis, Strain(Mechanics), Polymers, Metals, Ceramic materials, Silicon nitrides, Bifurcation(Mathematics), Equations, Models, Theory, Symposia

Distribution Statement : APPROVED FOR PUBLIC RELEASE