Failure Behavior of Pressurized Spherical Tanks Depending on Manufacturing Method

There are numerous applications of pressure vessels in aerospace field for storing liquid or gaseous media. Generally the metallic vessels have been manufactured by welding two hemispheres, which are machined or spin-formed. In this study, the solid state bonding method was utilized with blow forming to manufacture aerospace titanium tanks. This solid state joining technology replaced the welding process and without any secondary material or liquid phases in bonding process, homogeneous microstructure was obtained at bonding interface. Using this method, a titanium tank of a space vehicle was manufactured and during a hydraulic pressurizing test, the strain and acoustic emission signals are observed to investigate the effect of solid state bonding method on the failure mode and performance of the tank.. This result was compared with the one made by conventional method of spin forming and welding. The result shows that the pressurization rate and the acoustic emission signal increasing rate provide a similar tendency for a vessel of integrity, while the signal increasing rate is much higher than the pressurization rate for a vessel with welding defects. It is clear that the failure mode of the solid state bonded tank is different from the welded tank due to the completely united interface by diffusion process.