Abstract
Completely random polycrystalline aggregates, the grain shape and crystalline orientations of which are uncorrelated, are considered. Our recently constructed formal upper and lower bounds are applied to evaluate the elastic moduli of the aggregates of tetragonal crystals (classes 4/mmm, 42m, 4mm and 422). Numerical results for a number of practical crystals are presented, which indicate that the shape-independent bounds are very close to the much simpler bounds for the subclass of idealistic spherical cell polycrystals. The bounds appear tight, giving useful estimations on the elastic moduli of the aggregates.