Notched tensile creep testing of ceramics

The use of axisymmetric tensile creep specimens containing semicircular notches is shown to provide important data which complement results of the common smooth tensile creep test. The notch provides a stress and strain concentration which can represent the non-uniform state of actual components in service. Finite element analysis confirms that the initial concentration of stress redistributes during creep to yield a more uniformly loaded cross-section. Additionally, it is shown that the stress follows a highly non-proportional loading path during creep. The first experiments of notched tensile creep of a ceramic (silicon nitride) are examined in the light of finite element simulations of the transient deformation. The implications of notched tensile creep are discussed as an important test for the evaluation of constitutive models.