Failure Analyses of Beryllium Copper Bourdon Tubes

摘要

High strength beryllium-copper, UNS C17200, were extruded to form 1.2-inch diameter Bourdon tubes with a wall thickness of 0.0065 inches. One end of the Bourdon tube was soldered to a brass socket for end support, the other end was silver brazed to a ferromagnetic cylindrical rod to form an LVDT transducer. These Bourdon-tube transducers were used to monitor gasoline pump pressure to prevent gasoline tank leakage required by the government. Many Bourdon tubes failed unexpectedly after six month in service. Cracks and holes were found to penetrate through the wall thickness of Bourdon tubes near the brass socket. Microstructure analyses, microhardness measurements, SEM fractographical studies, and x-ray microanalyses were conducted for failure analyses. Finite element analysis was also employed to identify the maximum stress level and location on the tubes. Stress corrosion was found to be responsible for the failures. Alternative solutions to prevent similar failures will be provided.