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In this paper, the authors elaborate how numerical techniques developed from the direct method can be used to predict the load-bearing capacity of the aluminum casting beam structure which is presently used in the Chinese high-speed train CRH5A. The numerical method introduced in this paper is formulated based on the Melan's static theorem; thus, it determines the strength of the cast aluminum beam under both monotonic and cyclic loads without following the entire load profile. In addition to constructing the plastic and shakedown limits of the component, the proposed approach is also employed to study how stiffeners' thickness on the key areas influences the feasible load domains. Based on the intensive sensitivity analysis, an optimal thickness has been determined which gives the highest strength-to-weight ratio. To this end, the paper confirms that the direct method is a viable means for designing structures used in the rolling stock.

Simulating three-dimensional acoustic problems with traditional finite element models (FEMs) may result in a large dispersion error that is difficult to manage. To control dispersion error caused by “overly stiff” features of FEM, a face-based smoothed FEM (FS-FEM) model was used to analyze the sound field of a high-speed train. Based on the acoustic Galerkin method’s weak form, smooth regions were reconstructed within the original finite element area, and numerical simulations were performed in MATLAB. Modal analysis of a test example revealed that results obtained using FS-FEM are more accurate than those obtained using the traditional FEM. Finally, it was used to calculate the sound field of China Railway High-speed 380B (CRH380B) high-speed trains in time and frequency domains, achieving higher accuracy than the traditional approach. Results were more akin to the realistic solution, which demonstrated the performance of the FS-FEM.

Structural optimal design is traditionally performed according to the elastic limit rule which makes the structure overweighted or strength over conservative to an extent. Shakedown theory is implemented in the present study in order to measure load-capacity performance of structure. It can determine the strength of a structure under arbitrary varying loads without loading history where failure form of incremental collapse, ratcheting and alternate plasticity will be avoided. The current research subsequently provides a parameter optimal design scheme with respect to maximum structure strength and strength-to-weight performance in the framework of shakedown which makes the optimal structure design in a relatively practical way. With this motivation, the formula of proposed shakedown limited parameter optimization problem is derived and solved based on genetic-gradient coupling algorithm. The present coupling algorithm is essentially solve a double-loop problem where the inner loop adopt interior point method to solve shakedown problem under a given parameter combination while the outer loop use genetic algorithm to find the optimal parameters based on a given shakedown fitness. In addition, external database technique is applied to accelerate computation and prevent unexpected interrupt. Subsequently, a test example which is a optimal parameter design problem of plate with a circular hole is presented to demonstrate the accuracy and effectiveness of the proposed method and algorithm. In addition, the proposed method is also utilized to determine the optimal load-bearing capacity of a airtight module to be used in a manned spacecraft. Moreover, optimal shakedown load design results of the manned airtight module as well as optimal strength-to-weight efficiency design results are given in the end. This study confirmed that genetic-gradient coupling algorithm is a effective means for determine the optimal parameter in accordance to the shakedown load domain.