Accession Number : ADP003107

Title :   Dynamic Crack Growth Criteria in Structural Metals,

Corporate Author : CALIFORNIA INST OF TECH PASADENA

Personal Author(s) : Rosakis,A. J. ; Duffy,J. ; Freund,L. B.

Report Date : OCT 1983

Pagination or Media Count : 19

Abstract : Analytical difficulties associated with the dynamic crack propagation problem have limited the available dynamic solutions to idealized situations. The major limitations introduced by these analytical solutions make both numerical methods and direct experimental observations necessary for the complete understanding of the dynamic fracture process. A principal purpose of experimental studies is to observe directly the instantaneous stress intensity factor as a function of crack speed, and to determine whether or not the observed variation constitutes a material characteristic. The present paper provides a description of dynamic crack propagation experiments on double cantilever beam specimens of a high strength steel. Measurements of the crack tip deformation field and of crack speed during propagation have been made using the optical method of caustics in reflection. A principal advantage of a measurement made directly at the crack tip is that the interpretation of data does not rely on a complete transient stress analysis of the entire specimen. The inherent time dependence of crack propagation experiments requires that many sequential measurements of field quantities be made in an extremely short time and in a way that does not interfere with the process to be observed. Furthermore, the area over which the field quantities are to be measured advances along with the crack tip, and often in a nonuniform way. The method of caustics is attractive for meeting these experimental requirements. (Author)

Descriptors :   *Metals, *Steel, *Crack propagation, *Dynamics, *Fracture(Mechanics), *Numerical analysis, Caustics, Reflection, Optics, Stress concentration, Front ends and surfaces, Cracks, Velocity, High strength, Deformation, Time dependence, Equations, Geometry, Modulus of elasticity, Poisson ratio, Test methods, Cantilever beams, Beams(Structural), Static loads, Experimental data, Graphs, Symposia

Distribution Statement : APPROVED FOR PUBLIC RELEASE