QUANTITATIVE MEASUREMENTS OF YOUNGS MODULUS USING THE MINIATURIZED DISK-BEND TEST

The miniaturized disk-bend test (MDBT) has been used to evaluate the y ield stress and fracture toughness of thin disk-shaped samples 3 mm in diameter. Two experimental configurations may be employed: loading ap plied by a solid ball (ball-on-ring mode) or by a hollow cylinder (rin g-on-ring mode). Literature values of the yield stress of ordered inte rmetallic compounds and the fracture toughness of several ceramics hav e been successfully reproduced by the MDBT technique. In this paper, w e show how the ring-on-ring mode can be used to measure Young's moduli for hot-pressed NiAl samples of varying porosity and thickness in the range 200 mu m less than or equal to t less than or equal to 600 mu m . The key to this method lies in the derivation of an equation allowin g the determination of Young's modulus from the measured load-displace ment curves even for thicknesses where a state of plane stress may not necessarily exist.