High ambient pressure testing apparatus and demonstration of use for material testing

Abstract

This thesis describes the work involved in designing and fabricating a high-ambient pressure chamber for material testing. Using SolidWorks CAD software, an SAE AISI 4340 steel chamber was designed with a simulated design pressure of 60,000 psi and a proof pressure of 30,000 psi. Supporting air, electrical, and sensing systems were also designed for remote operations. A proof-pressure test was performed where the system reached 30,000 psi and pressure was maintained for 30 minutes with no sign of deformation or failing. Following proof pressure testing, the dive of the DeepSea Challenger to Challenger Deep in the Mariana trench was simulated. Four each of two copper alloys and two aluminum alloys were pressurized in the chamber to 15,400 psi and dimensional measurements, microhardness, and surface images were compared between pretest and posttest data collection. Analysis of the data indicated that there were statistically significant changes in microhardness averages for the copper alloys at an alpha level of 0.1 for both alloys and an alpha level of 0.05 for one. The aluminum alloys had no statistically significant changes in microhardness average but did have a significant change in variance at an alpha level of 0.1 for both alloys and 0.05 for one. The variance showed a narrowing of distribution around the pretest average data. Imaging showed changes in topography at magnification greater than 2000x for the aluminum alloys indicative of a possible change in structure which would likely have a corresponding change in material properties but further research is required to confirm and quantify these changes.