Development of a controlled-atmosphere, rapid-cooling cryogenic chamber for tribological and mechanical testing

Mechanical testing of seals, bearing materials, and mechanisms in cryogenic environments is a rapidly growing field of research, as it promises improvements in equipment performance and reliability for applications such as space exploration, liquid hydrocarbon storage, and superconducting devices. Cooling of test equipment is usually performed within a well-insulated test chamber, via direct or indirect evaporation of liquid cryogen. State-of-the-art equipment is frequently insufficient for rigorous testing, being expensive and cumbersome, cooling slowly, struggling to replicate relevant environmental conditions, and/or failing to reach the temperature of the cryogen. Herein, we employ a rapid prototyping approach using polymer 3D printing to iteratively refine cryogen-based cooling of a tribometer. The final design greatly exceeds the minimum temperature of state-of-the-art equipment, cooling a chamber to liquid nitrogen temperatures (-196 °C) while maintaining dry test conditions. When modified for use on a cryogenic tensile tester, the design cools to -150 °C in 149 s, significantly improving upon state-of-the-art performance. By utilizing this 3D-printed equipment, we find that components produced via Fused Deposition Modeling with unmodified, commodity polylactic acid have favorable mechanical properties in a cryogenic environment: tensile strength of 110 MPa, elongation at break of 10%, and specific wear of 5.6 × 10^-5 mm³/Nm against stainless steel. By leveraging 3D printing for rapid manufacture of production-quality parts, highly refined cooling chamber designs have been experimentally developed for both a tribometer and a load frame in rapid succession, enabling significant improvements in cryogenic test capabilities.