Tensión de fractura de materiales cerámicos mediante ensayos Small Punch

Abstract

Ceramic fracture is brittle, so the fracture stress values of nominally identical pieces and subjected to the same mechanical stresses are highly variable. Due to this behavior, it is necessary to carry out tests on a large number of specimens to differentiate between materials with systematic variations of the microstructure. Standard tests (3 or 4 points bending) require a large volume of material that is often not available. In addition, many ceramic components are manufactured in the form of small thin disks and the processing of specimens for bending can significantly modify their mechanical response. One solution to this problem is the use of the components themselves as miniature test specimens such as the Small Punch Test (SPT). In this work, the characterization of the fracture stress of advanced ceramic materials by means of SPT is analyzed. To ensure the validity of this test, three materials with very different elastic parameters (PZT, alumina and silicon nitride) have been chosen, which implies analyzing the influence of different punch-surface interactions of the material. For each material, series of discs of two different thicknesses have been characterized and an extensive fractographic analysis campaign has been carried out in order to identify the critical defects and, thereby, ensure the validity of the method. The corresponding Weibull distributions have been obtained, the effective volumes have been determined and the relationships between the Weibull parameters of the distributions obtained have been established.