Clarification of the plastic deformations zone borders for the fuel tank diaphragm

A relevant area of theoretical and practical research in the field of rocket science is ensuring the uninterrupted and reliable operation for liquid rocket engines. Reliable operation and engine start in zero gravity is impossible without guaranteed separation of the liquid and gas phases in the fuel tank. This problem is solved by the introduction of metallic reversible diaphragm separators. The eversion process research for the metal diaphragm separators allows you to design them for fuel tanks of various sizes and shapes according to the specified parameters of the displacement of the component. This is an actual object of research. The known mathematical dependencies do not have sufficient accuracy and correspondence to experimental results. To improve the quality of design when using any deformation-energy approach, it is necessary to increase the accuracy of determining the boundaries for plastic deformation zone of diaphragms at various stages of eversion. Clarification of the boundaries for this zone is possible using modern computer modeling tools. The article provides a descriptions and simulation result for metal diaphragms with different geometric parameters, loaded with uniform pressure, taking into account the plastic material properties in the MSC NASTRAN software package. As a result of the work, a refined zone of plastic deformation for fuel tanks metal eversible diaphragms was determined. We have introduced new angles to describe this zone. The dependences for these angles on the angle of the torus region, independent of the geometric parameters of the diaphragm, were obtained. We also identified the conditions under which the use of the energy principle equation is inappropriate due to the presence of membrane stresses.