Accession Number : AD0698474

Title :   FUNDAMENTAL STUDIES OF FRACTURE.

Descriptive Note : Final rept. 7 May 65-6 May 69,

Corporate Author : COLUMBIA UNIV NEW YORK HENRY KRUMB SCHOOL OF MINES

Personal Author(s) : Gensamer,Maxwell ; Li,James C. M.

Report Date : DEC 1969

Pagination or Media Count : 10

Abstract : The investingation of fracture focused on elucidating the mechanisms by which strain becomes so concentrated that the work of deformation, limited to a small volume becomes little. The research concerned primarily with engineering materials consisted of the following phases: (1) A theoretical study of the elastic contribution to the surface energy controlling final separation of the material embrittled by plastic deformation. (2) An experimental study of how to reveal the plastic zone and measure its size in materials of interest. (3) A study of strain hardening, which controls the plastic zone size, by studying the effects of prior strain on the operation of latent slip systems. (4) A study of strain hardening by calculating the stress at a point due to pile-up complete dislocation loops. (5) A study of the process of fracture in fatigue, both experimental by optical and electron microscopy, and theoretical by applying dislocation dynamics. (6) An experimental and theoretical study of plastic zone strain distribution, controlling fracture toughness, and propagation velocity controlling crack speed, in iron and an iron-silicon alloy. (7) A similar study of brass, involving stacking-fault energy as a variable. (8) A study of creep, relating to the slow growth of cracks preceeding rapid crack propagation, by applying the theory of thermally and stress activated rate processes to dislocation movements. (Author)

Descriptors :   (*FRACTURE(MECHANICS), *STRAIN(MECHANICS)), BRITTLENESS, DEFORMATION, STRAIN HARDENING, EMBRITTLEMENT, STRESSES, DISLOCATIONS, FATIGUE(MECHANICS), IRON ALLOYS, SILICON ALLOYS, CRACK PROPAGATION, BRASS

Subject Categories : Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE