Akimov D. Stress-strain state of complicated configuration shell structures at extreme external environments

The object of research is the processes of deformation and destruction of shell structures with technological features of a geometric shape. The subject of the study is the stress-strain state of shell structures of complex geometry with combined external loading in conditions close to operational ones. The purpose of the work is the development of methods for analyzing the stress-strain state of shell structures of complex configuration with static combined loading and an experimental study of the ability of products to perceive the given external force effects. Research methods: the finite element method, an experimental method for the study of full-scale structures-witnesses. The visualization of the deformation process and the comparison of calculations with the results of static tests showed a qualitative and quantitative convergence, confirming the accuracy of the proposed mathematical model of the study and the results of numerical analysis. Results obtained: an approach has been created to determine the stress-strain state of shell structures of complex configuration based on the Tymoshenko-Mindlin theory. A mathematical model for the deformation of the inter-step compartment and the fuel tanks is proposed, which takes into account the change in the mechanical characteristics of the material as a result of the transition to the plastic state under the action of load factors. The technique of experimental determination of destructive deformations of rocket-space equipment structures using witness fragments has been improved, which allows predicting the stress-strain state of shell structures made of composite materials using computational methods without carrying out expensive and long-term experimental testing. Directed tests of real structures of rocket technology were carried out for specified types of combined external loading. New mechanical effects due to the peculiarities of the geometrical shape of the structure, material properties and the nature of the load have been discovered. The scientific novelty lies in the fact that, based on the analysis of the visualization of the deformation and stresses fields along the surface of the shells of complex shape and a targeted experimental study, the zones of the most likely destruction of structures are identified. The described approaches allow to predict with a high degree of probability a static destructive loads of shells of rotation of complex configuration under conditions close to operational ones. Research results drawn on in practice of the Yuzhnoye State Design Office. The field of application is rocket and space technology.