Improving heat sinking in ambient environment for the shape memory alloy (SMA)

摘要

SMA has been used as an actuator alongside with certain heat sinking mechanism which makes the structure of the actuator as a whole, bulky and heavy in nature. This paper describes the effort taken in speeding up the rate of heat transfer of the SMA in ambient environment by introducing a simple, new heat sink, consisting of a combination of an outer metal tube and silicone grease as cooling medium. The SMA wire of diameter 0.3 mm is first coated with a layer of silicone grease, and is inserted into the outer metal tube making sure that the silicone coated SMA does not inhibit the mobility of the outer metal tube. An experimental setting, with the task of using the SMA to vertically haul up a 3kg weight was set up. PWM (pulse width modulation) control was applied to the SMA and by using a position sensor, the rise and fall of weight can be easily monitored, therefore the response speed of the actuator can be observed. Meanwhile a temperature sensor, a thermocouple type-K, was used to monitor the temperature of the SMA for temperature control. Simulation results of the rate of heat transfer based on the heat transfer equation are also presented to validate the effectiveness of this proposed heat sink.