Crack propagation test and structural analysis to predict fracture behavior of aluminum alloy tanks

Abstract

Physics model-based quantitative safety analysis method should be established both for meeting the strict flight safety requirement and maximize the mission flexibility of the flagship liquid rockets. Isogrid tank destruction model of the crack propagation triggered by the pre-generated longitudinal slit hole has been developed, based on the dynamic explicit FEM analysis and the crack propagation test methods for the model validation. The crack propagation test method for the flat panel with and without rib structures was proposed and demonstrated to obtain the valid data for the investigation of the destruction mechanisms and the model validations. From the test and computed results, it was found that the reason why the crack propagation direction changes when the rib angle is different is that the smaller the rib angle, the stronger the asymmetry of the shear stress distribution based on the crack propagation direction. As a result, the principal stress direction near the crack tip is inclined with respect to the load direction, and the propagation direction of the crack traveling perpendicular to the principal stress direction changes. The calculated crack propagation path and propagation velocity are in good agreement with the experimental data, indicating that it is an effective test method for identifying the parameters of the material model.

Keywords

• crack propagation
• aluminum alloy
• isogrid structure
• dynamic finite element method
• liquid rocket
• flight safety
• propellant tank
• rupture behavior prediction technology