Abstract :
Internal fracture patterns developed in silicon
carbide cylindrical targets as a result of dynamic
indentation (63-500 m/s) by tungsten carbide spheres
are defined. Microscopy of recovered and sectioned
targets delineate into three regions, each associated
with distinct cracking modes, i.e., shallow cone macrocracking
at and near the impact surface, steep interior
cone macrocracks that radiate into the target from the
impact region and local grain-scale microcracking
directly underneath the impact region. The observed
fracture patterns are found to maintain a noticeable
degree of self-similarity upto the impact velocity of
500 m/s. Linear elastic analysis of the full (surface and
interior) stress field developed under static (Hertz) contact
loading delineate the target into four regions, based
on the number of principal stresses that are tensile
(none, 1, 2 or all 3). A strong correlation is found
between the principal stress conditions within each
region and the forms of cracking, their locations and
orientations present therein. This correlation has a number
of implications, including non-interaction of crack
systems, which are discussed. Illustrative linear elastic
fracturemechanics analyses are performed for threeregions, and calculated and observed macrocrack
lengths are found to be in reasonable agreement
