Abstract
The aim of this research is to realize an ultrasonic motor at cryogenic environment. Because the driving temperature decreases from room temperature to an ultralow temperature, a thermal stress is generated. By the thermal stress, changes in pre-load are caused, and the performance of the motor decreases. The ultrasonic motor for cryogenic temperature needs to be designed to reduce the thermal stress. In this research, bolt-clamped Langevin-type transducers (BLTs) suitable for cryogenic temperature have been used. The diameter and the length of the BLT are 20 and 16mm, respectively. BLTs are mainly made of SUS304, Ti, and invar, which have different thermal expansion coefficients. The performance of BLTs has been evaluated by measuring vibration velocity at 300K. Additionally, thermal stress of BLTs has been evaluated when the temperature falls from 300K to 4.5K. The vibration velocity and thermal stress of BLTs has been compared.
