Instrumented Cylindrical Punch Indentation of Solid Nitrogen at 30-40 K.

In support of NASA's Triton Hopper project, mechanical response data for solid nitrogen are needed for concept validation and development. Available mechanical properties data is sparse with only three known indentation measurements existing between 30 and 40 K. To generate more data, a custom instrumented hardness tester was developed to interface with a cryostat. The system was used to conduct cylindrical punch indentation testing at Triton-relevant thermodynamic conditions. Pressure versus displacement curves and hardness values were obtained. In the experiments the hardness ranged between about 2 kg/mm2 and 0.5 kg/mm2 in the aforementioned temperature range. A suspected brittle fracture is observed at lower temperatures in the range.