EFFECT OF MICROPOROSITY ON ELASTIC MODULUS AND YIELD CURVE OF POLYCRYSTALLINE GRAPHITE

The parameters defining the non-linearity of the stress-strain curves of graphite under compression are related to the increase in elastic modulus with temperature. Both are shown to be a result of widespread microporosity due to cooling stresses. The analysis is based on a theory of displacements at slit cracks under shear due to the spread of plastic deformation from the tips. Other mechanical properties such as thermal cycling strain, the stress-dependence of thermal creep and the fracture strength are all embraced in the argument. Other materials such as β-eucryptite and cast-iron with similar yield curves and micro-fissure populations are considered. © 1969.