Local Heating and Local Transformation of a Shape Memory Alloy Foil by Laser Irradiation

Abstract

A novel way of actuating Shape Memory Alloy (SMA) is reported in this paper. Though conventional SMA actuation can get only one deformation pattern because of using whole heating like Joule heating, proposal method achieves various deformation patterns. Laser irradiation can heat any local area on SMA and deform only the heated area. And controlling this heated area size (by changing Laser irradiation parameter(s)) provides multiple transformation patterns. This increases SMA actuator degree of freedom and expands its application range. This report shows the temperature distribution on SMA foil heated by laser beam. The temperature extends radially from the irradiation center. Transformation area (over 50 degrees Celsius which represents transformation temperature) expands as the laser irradiation power increases, and does not depend on laser irradiation spot diameter. To demonstrate local transformation rectangle SMA foil memorized roll shape was used in this paper. The foil keeps flat shape by external tension and making protrusion(s) when a laser beam(s) is/are irradiated, and the transformation needs 2 seconds in average. This protrusion can be made at any locations (minimum space is 9mm between two protrusions). Protrusion size is controlled by laser irradiation power and external tension.