DIRECT MEASUREMENTS OF DISPLACEMENTS IN THE INNER ROLLER SPAN OF 4-POINT-BENDING CREEP TESTS

Creep tests on ceramic materials are often performed in four-point-bending. With conventional procedures of evaluating such tests a number of assumptions must be made to allow the calculation of the displacements in the inner roller span-the range of the constant bending moment-from displacement measurements containing the part between the outer and the inner rollers where the bending moment changes linearly from zero to its maximum value. A test apparatus is described that allows direct measurements in the interesting part of the bending specimen. Creep curves obtained with different methods are compared.