Anisotropy Effect of the Mechanical Metal Properties on the Assessment of the Load-Carrying Ability of the Launch Vehicle Oxidant Tank

The paper presents the results of the calculated estimate of the critical pressure level in the oxidant tank of the launch vehicle using generalized diagrams of elastic-plastic deformation of the aluminum alloy AMg6. These diagrams consider the anisotropy of the physical and mechanical properties of the material. The calculation of the stress-strain state is performed using the simplified calculation scheme for the specified structural element of the tank depending on the internal pressure in the axisymmetric statement considering the elastic-plastic deformations. The calculation analysis is based on the mixed scheme of the finite element method, which provides the continuous approximation of displacements and stresses. It allows one to determine the stress-strain state of the tank element with high accuracy. It is implied that the maximum values of stresses and strains occur in the area of the fillet region connecting the ring with the cylindrical shell of the tank. Complying with the obtained data, the calculation of the stress-strain state of the tank element using generalized deformation diagrams, taking into account the anisotropy of physical and mechanical properties and the nature of the load of aluminum alloy AMg6, leads to a more conservative estimate of the critical pressure level as compared with the standard calculation based on the uniaxial tensile diagram.