In this paper, an analytical approach for global buckling of ring-stiffened sandwich cylindrical shells is presented with layerwise theory (LWT). Appropriate displacement functions are assumed according to the boundary conditions and the deformation characteristics of the inner and outer shells. The strain energies of the inner and outer shells and the ribs and the work done by external forces are derived with the help of classical laminate theory. Furthermore, the Rayleigh–Ritz method is employed to obtain the critical buckling load of ring-stiffened sandwich cylindrical shells. The ribband width has a great influence on the precision of calculation of the critical buckling load, and a formula for calculating this width is obtained by data fitting. To confirm the accuracy of the proposed formulation, a numerical simulation is carried out by using Abaqus FEM software. The results show that the proposed approach has high accuracy in predicting the global buckling behavior of ring-stiffened sandwich cylindrical shells. Finally, the effects on the buckling performance of ring-stiffened sandwich cylindrical shells caused by changing the inner and outer shell thicknesses and the rib height, thickness, and spacing are explored.
The genetic programming approach is proposed to predict temper embrittlement of rotor steel (30Cr2MoV). Two independent data sets are obtained experimentally: training data and verifying data. Peak current density of reactivation, temperature of electrolyte, the general chemical composition parameter (J-factor), chemical composition of Cr and S, hardness and the grain size parameter of the material are used as independent variables, while fracture appearance transition temperature as dependent variable. On the basis of training data, the best model was obtained by genetic programming, and the accuracy of it is verified with the verifying data. The prediction error of the model is within the scatter of ±20 C. The results suggest that, the prediction model obtained by genetic programming is feasible and effective.
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