Effects of Hemispherical End-caps Geometric Optimization on Fatigue Life of Ceramic External Pressure Housing

At present, underwater gliders are not yet able to form effective observations throughout the hadal zones due to the limitations of traditional metal properties. Ceramic materials have excellent compressive strength, modulus of elasticity and low density, which can provide new solutions. However, pressure housing made of ceramic materials also has problems such as a short fatigue life. The material and geometric discontinuities between the end-cap and ceramic housing produce tensile stress on the bearing surface and cause fatigue failure under cyclic pressure. Based on this, the optimization of hemispherical TC4 end-cap geometry was focused. Utilizing the response surface method (RSM) of ANSYS workbench optimization module, and three optimization variables of mid-radius Rm of the hemisphere end-cap, B and H of rigid support were analyzed to obtain the minimum tensile stress Tstress of silicon carbide ceramic pressure housing. The radial and axial deformation curves of the pressure housing, as well as the variable sensitivity curve were obtained. Optimization results showed that Tstress was reduced by 17.4%, and the Sf is increased from 2.49 to 3.01. All three parameters had effects on the fatigue life of the ceramic pressure housing, the Rm was most obvious. This method provides a methodological guide for designing the end-cap of a ceramic pressure housing.