Abstract
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 a circular shape centered to the heater. Caustics pattern appears at a certain stress value then increases in diameter (Caustics Size). As soon as heating process goes to its steady state, Caustics pattern movement goes slowly then stops. A strong relation between Caustics pattern size and position of the highest value of the radial thermal stress has been founded. Also theoretical Caustics pattern size equation has successfully obtained. The comparing between the behavior of Caustics pattern movement and thermal stress distribution as well its behavior during heating process engages us to conclude that Caustics experiment method could be used to measure thermal stress gradient.
