Cryogenic Materials Characterization and Thermal Contact Optimization

Abstract

The design of technology that operates at cryogenic temperatures requires an extensive knowledge of the behavior of the materials comprising the design. This work utilized a test facility that allows for the precise measurement of material properties at these cryogenic temperatures. The material of interest was Oxygen Free High Conductivity (OFHC) copper as it is a very common material choice for designs at these temperatures. The two material properties that were investigated and characterized were thermal bulk conductivity and thermal contact resistance. The purpose of these tests was to investigate some of the primary and secondary factors that affect these material properties that have been under-represented in the literature. The thermal bulk conductivity testing focused on the impact that the source of purchase had on the overall conductivity of the sample; samples purchased from different commercial vendors undergo different amounts of work hardening due to differences in manufacturing practices and the level of work hardening directly effects conductivity. The thermal contact resistance testing focused on the impact of contact interface pressure of gold-plated samples. An additional component of this contact resistance testing was investigating the effect of mating and de-mating cycles across this pressure range. The results from this material characterization were then inserted into a newly created thermal simulation framework. The thermal simulation framework was utilized to design and thermally optimize a common component found in these cryogenic technologies, a bolted joint. The successful optimization of this joint indicates that the process of material property characterization followed by the use of this thermal analysis framework could be used to aid in the design of additional cryogenic technologies in the future.