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Rail vehicles generate huge longitudinal impact loads in collisions. If unreasonable matching exists between the compressive strength of the intermediate coupler and the structural strength of the car body, the risk of car body structure damage and train derailment will increase. Herein, a four-stage rigid–flexible coupling finite element model of the coupler is established considering the coupler buckling load. The influence of the coupler buckling load on the train longitudinal–vertical–horizontal buckling behavior was studied, and the mechanism of the train horizontal buckling instability in train collisions was revealed. Analysis results show that an intermediate coupler should be designed to ensure that the actual buckling load is less than the compressive load when the car body structure begins to deform plastically. The actual buckling load of the coupler and the asymmetry of the structural strength of the car body in the lateral direction are two important influencing factors for the lateral buckling of a train collision. If the strength of the two sides of the car body structure in the lateral direction is asymmetrical, the deformation on the weaker side will be larger, and the end of the car body will begin to deflect under the action of the coupler force, which in turn causes the train to undergo sawtooth buckling. [ABSTRACT FROM AUTHOR]

Abstract Rail vehicles generate huge longitudinal impact loads in collisions. If unreasonable matching exists between the compressive strength of the intermediate coupler and the structural strength of the car body, the risk of car body structure damage and train derailment will increase. Herein, a four-stage rigid–flexible coupling finite element model of the coupler is established considering the coupler buckling load. The influence of the coupler buckling load on the train longitudinal–vertical–horizontal buckling behavior was studied, and the mechanism of the train horizontal buckling instability in train collisions was revealed. Analysis results show that an intermediate coupler should be designed to ensure that the actual buckling load is less than the compressive load when the car body structure begins to deform plastically. The actual buckling load of the coupler and the asymmetry of the structural strength of the car body in the lateral direction are two important influencing factors for the lateral buckling of a train collision. If the strength of the two sides of the car body structure in the lateral direction is asymmetrical, the deformation on the weaker side will be larger, and the end of the car body will begin to deflect under the action of the coupler force, which in turn causes the train to undergo sawtooth buckling.

Abstract The suggested before energy barrier criterion for design buckling pressure is extended to the case of clamped shallow spherical caps. It is developed for shells with geometrical imperfections and a new adjusted formula is obtained for design buckling load of imperfect structures. The method is applied to shells with elastic-perfectly plastic material. It is validated by experimental data and proved by numerical analysis based on finite element method. Calculation results were obtained and analysed for different values of shell geometrical parameter. A simple formula for design buckling pressure is suggested and validated. [ABSTRACT FROM AUTHOR]

Energy perturbation is applied as a measure in the stability analysis of a spherical shell subjected to uniform external pressure. The energy barrier (buckling energy) is calculated using asymptotic method, which allows to estimate sensitivity of the structure to the perturbation. It is possible to define the level of external pressure separating areas of small and extensive sensitivity of the structure to the perturbations. This pressure level can be recommended as a design buckling load for spherical caps. The obtained result corrects NASA SP-8032 recommendations which are over-conservative. The asymptotic approach is validated using ANSYS software package. In addition, the influence of boundary conditions on buckling load is estimated using the software. [ABSTRACT FROM AUTHOR]

The asymptotic method for spherical shells at large deflections was developed in the case of composite shell subject to external pressure. Reissner's equations describing axially symmetric deformation of deep shells with arbitrary deflections and rotation angles were considered as initial ones. They were significantly simplified and asymptotic formulae for deformation energy, external pressure and stresses depending on deflection amplitude were obtained. The energy barrier criterion was applied for the composite shell for estimation of the shell metastability. Formula for design buckling pressure was derived for composite shells. It improves the significantly more conservative NASA SP-8032 recommendations. The full inversion of the shell was studied as well. Asymptotic formulae were obtained for evaluation of stresses and load deflection dependencies. They can be useful for design of diaphragms for positive expulsion propellant spherical tanks of launch vehicles and for other applications. [ABSTRACT FROM AUTHOR]