Application of numerical methods for the analysis of the methodology for calculating external load when a helicopter crashes

The paper considers helicopter crash on deck structures of a nuclear vessel. The vertical fall of the helicopter as the most dangerous one is accepted as a design accident when evaluating the strength of the structures of the objects. Calculation of crash parameters during the fall is performed using two procedures: engineering methodology and finite element method. The engineering technique is based on the solution of the Taylor problem of the impact of a rigid-plastic body on a rigid barrier, taking into account the propagation of shock waves in the body. The main assumptions of the engineering methodology, which determine the accuracy of the results obtained with its help, are noted. More reliable results of the analysis are obtained using the finite element method and explicit schemes of integration of nonlinear equations of dynamics. A detailed beam-shell finite element model of the helicopter with real distribution of mass and stiffness characteristics of the fuselage was used. Time dependences of the collapsing helicopter velocity, contact impact force and potential energy of deformable structures were obtained by two procedures. The finite element method additionally gave the deformation patterns of the deck and fuselage force structures. The results of work have shown qualitative and quantitative estimation of errors of engineering methodology and limits of its applicability.