Accession Number : AD0674747

Title :   DIRECT BASAL-PLANE SHEAR IN SINGLE CRYSTAL GRAPHITE.

Descriptive Note : Research Communication no. 68,

Corporate Author : DOUGLAS AIRCRAFT CO INC HUNTINGTON BEACH CALIF ADVANCED RESEARCH LABS

Personal Author(s) : Soule,D. E. ; Nezbeda,C. W.

Report Date : JUL 1968

Pagination or Media Count : 78

Abstract : The paper consists of an analysis of the overall stress-strain behavior of single crystals and, to a lesser extent, of pyrolytic graphite. In the order of increasing applied stress are presented the shear modulus G, the low critical resolved shear stress sigma sub c, the observations of creep and extreme glissile slip, and finally shear fracture and the effect of cyclic shearing on shear strength sigma sub s. The type and effect of bulk lattice imperfections, such as twins and delamination voids, are investigated. Correlations are made between the change in the observed G and the concentration of dislocations and bulk lattice imperfections. The average dislocation line segment length l and density N sub D are calculated from the observed sigma sub c and change in G. Attempts to circumvent the influence of dislocations by pinning or frequency damping are considered. One of these, the pinning of dislocations by boron ions, is observed here directly to be very effective in increasing G, approaching asymptotically the intrinsic lattice value G sub o. (Author)

Descriptors :   (*SINGLE CRYSTALS, SHEAR STRESSES), (*GRAPHITE, SINGLE CRYSTALS), STRESSES, STRAIN(MECHANICS), CREEP, DISLOCATIONS, CRYSTAL DEFECTS, BORON, DOPING

Subject Categories : Ceramics, Refractories and Glass
      Crystallography

Distribution Statement : APPROVED FOR PUBLIC RELEASE