Pressure-resistant and waterproof shell structure design for deep-sea magnetic sensing equipment

Aiming at the non-magnetic, lightweight and pressure-resistant requirements of 3000 m deep-sea magnetic sensing equipment, this study proposes a double-shell structure composed of 7075 aluminum alloy and S-glass fiber/epoxy composite with cross ribs. Numerical simulation results show that the yield strength margin (45.1% for Shell 1 and 32.9% for Shell 2) and the maximum deformation (less than 0.25%) of metal components could meet the design requirements of 3000 m underwater operation. For the composite components, the local normal compressive stress of the cross ribs exceeds the transverse compressive strength, causing matrix cracking and reducing local stiffness, thereby transferring load to the undamaged regions. Therefore, in this study, the regions exceeding the allowable strength are subjected to stiffness reduction and recalculated. After load redistribution, the stresses in all fiber directions in both the damaged and undamaged regions do not reach the failure threshold of the maximum stress criterion. The redistributed stress does not exceed the allowable strength, and the damage remained stable without further propagation, thereby satisfying the design requirements.