Cryogenic Pressure Box Fabrication (CPBF)

The CPBF was an engineering service to develop specialty test hardware for composite test sections subjected to LH2 and LOX temperatures under structural loading conditions at NASA Langley Research Center (LaRC).  Sierra Lobo was contracted to develop the infrastructure for the NASA Langley Colts facility to test high Technology Readiness Level (TRL) mutli-purpose composite structural cryogenic tank sections, under flight load conditions. Architecture designed or specified included, hydraulic actuators that were utilized to pull on the test sections to simulate flight loading and cryogenic LN2, LHe, and helium gas storage and specialty heat exchangers for loading the test specimen under simulated LH2 and LOX tank inertial conditions. 

The most complicated of these systems designed and fabricated by Sierra Lobo was a pressure chamber with an integral vacuum jacket and the load transition section.  The test article geometry dictated that this chamber, which exposed the test article to the pressure and temperature load, be a box configuration.  The box geometry constraint was such that thermal stresses in the box created a finite fatigue life.  This box was designed using Sinda G and Fluent for the temperature profile and results were input into an ABAQUS Finite Element Model.  The resulting pressure and thermal stresses were compared to the design criteria of Appendix 4 and 5 of Section VIII, Division 2.  The subsequent fatigue life for each component was interpreted from the welded structure fatigue life methodology given in CEN pr EN 13445 (similar to API 579, International Institute of Welding, BS 7608 and other fatigue rules).