2003 年 3 巻 2 号 p. 65-70
Shadow optical method of Caustics has been applied in order to measure thermal stress distribution around a cylindrical heater inserted in a thin disk of acrylic. Caustics pattern has circular shape centered to the heater. Caustics pattern appears at certain stress value and then increases in diameter (Caustics Size). As soon as heating process goes to its steady state, Caustics pattern movement tends to slow and finally stops. A strong relation between Caustics pattern size and position of the highest value of the radial thermal stress has been observed. By this experiment a theoretical Caustics pattern size equation has also been successfully obtained. The comparison between the behavior of Caustics pattern movement and the thermal stress distribution and its behavior during heating process engages us to conclude that Caustics experiment method could be used to measure radial thermal stress gradient.
