Authors: B X Huang A Chanda R W Steinbrech J Malzbender
Publish Date: 2011/11/11
Volume: 47, Issue: 6, Pages: 2695-2699
Abstract
The temperaturedependent fracture toughness of brittle ceramics can be conveniently assessed from bending tests of specimens with defined cracks introduced by indentation However the validity of this indentation strength in bending method ISM depends critically on the correct consideration of the residual stress induced by the indentation process The ISM has been applied to La058Sr04Co02Fe08O3δ LSCF and for comparison on Ba05Sr05Co02Fe08O3δ BSCF perovskite LSCF with rhombohedral phase exhibits ferroelastic behavior at ambient temperature whereas BSCF deforms linearelastically Preindented specimens of both perovskites were fractured at room temperature in biaxial bending some of them after an additional annealing step The fracture toughness values of BSCF match reasonably well when determined with equations which consider the presence or absence of residual indentation stress Interestingly annealing has little influence on the apparent toughness results obtained for rhombohedral LSCF which appears to be related with stress relaxation by ferroelastic deformation
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