Development of Extensometer for Use at Cryogenic Temperatures

Abstract

An extensometer capable of use for tensile tests down to 4K was designed and constructed, in which the elongation of specimen was measured as bending strain of U-shaped thin beam by resistance strain gauges. As the gauge factor was temperature-dependent, a resistance thermometer was also installed on this device to measure the temperature while testing. The calibration was performed at low temperatures by using a simple apparatus in which a displacement was applied by a precision micrometer. The performance characteristics are summarized as follows: (1) The sensitivity increases monotonically by 6% of its room temperature value of 524μ strain/mm as the temperature is lowered to 4K. (2) The deviations from the linear relation of output strain vs. displacement are within 5μm in the displacement range up to 5mm. (3) The zero-drift is observed in the whole temperature range tested, but its rate to the temperature variation does not exceed the amount of 0.9μm/K.