Abstract
To re-examine the stress-strain diagram of dental casting alloy, that is, type 1 and type 4 gold alloy, Ag-Pd-Au alloy, and Co-Cr alloy, tensile test of the cast specimens was performed. The strain evaluated by a video extensometer and that estimated from the movement of the actuator of the test machine were compared. As a result, the former was effective in evaluating strain, while the latter should not be used because the shape to the yield point of the diagram. The elastic moduli evaluated by a video extensometer were significantly larger than those estimated from movement of the actuator, mainly owing to sliding between the grip wedge / specimen during the early stage of the tensile test. Furthermore, continuation of the sliding affects the stress-strain diagram and elongation. In conclusion, the extensometer was thought to be indispensable for working out the stress-strain diabram of dental materials.
