Wujiu Pan

Purpose: The purpose of this study is to analyze the vibration behavior of a cylindrical shell model with bolted ends under different influence factors, and to provide a reliable theoretical prediction for the study of bolted casing. Design/methodology/approach: Based on love theory, the vibration differential equation of laminated cylindrical shell is derived by using orthogonal polynomials as axial modal functions, combined with the boundary conditions of bolted joints and Lagrange equation, and the theoretical model of laminated cylindrical shell connected by bolts at both ends is established. By comparing the theoretical model with the finite element analysis results, the accuracy of the model established in this paper is verified. The influence of the number of bolts on the natural frequency and mode shape of the cylindrical shell and the influence of the axial, torsional, tangential and radial connection stiffness on the natural frequency of the cylindrical shell are analysed in detail. Findings: The different number of bolts has a great influence on the natural frequency and mode shape of cylindrical shell. The axial connection stiffness, tangential connection stiffness and radial connection stiffness have significant effects on the natural frequency of cylindrical shells, while the torsional connection stiffness has little effect on the natural frequency. Originality/value: The research content of this paper provides a key theoretical tool and prediction model for the safety design of aero-engine casing system. At the same time, the model established in this paper can be used as the theoretical basis of engine health management system (EHM), and an accurate vibration database under the health reference state is established according to the calculated natural frequency and vibration mode.

As the core structural component of aircraft engines, engine casings endure complex multiple mechanical loads. Accurate prediction of their dynamic characteristics is crucial for ensuring engine safety and reliability. Typically featuring cylindrical or conical shell geometries, the natural frequency represents a vital property of conical shells during free vibration, playing a significant role in assessing structural safety and preventing resonance. This paper establishes a free vibration prediction model for a three-layer thin-walled conical shell based on the Love first-order approximate shell theory, followed by detailed analysis. Using Lagrange polynomials as axial modal functions, the vibration differential equations under this theory are formulated and solved via the Rayleigh-Ritz method. The variation of the cone shell’s natural frequencies under different boundary conditions is examined. The accuracy of the proposed model is validated by comparing results with simulation data, and the differences in outcomes under various operating conditions are explored. The study demonstrates that the established prediction model effectively provides reference for the design and optimization of aeroengine cone shells, while also offering theoretical support for the application of multi-layer composite structures.

1. In practice, achieving perfectly symmetrical rotor support and connection in all directions is virtually impossible due to various factors such as manufacturing, installation, and operational co...

Compared with constant operating conditions, the vibration signals of rolling bearings under variable load conditions are more susceptible to the influence of load fluctuations, resulting in complex and weakened fault characteristics, making it difficult for traditional models to extract effective features and possess sufficient generalization ability, thereby affecting the accuracy of diagnosis. To address these issues, this paper proposes a wide kernel convolutional neural network (WLGCNN) for fault diagnosis under different load conditions. This model uses a first‐layer wide convolution kernel to capture the fault influence time‐series patterns within the rotation period, and the subsequent part uses 1 × 1 convolution to complete channel feature fusion and nonlinear transformation. Combined with data preprocessing strategies such as signal segmentation and Z‐score normalization, the sample data are effectively purified and the feature recognition ability is improved. Experiments are conducted using the standard dataset of rolling bearing faults provided by Case Western Reserve University (CWRU) and the Mechanical Fault Prevention Technology (MFPT) dataset. Ablation experiments and cross‐load comparison experiments verify that the model constructed in this paper has high diagnostic accuracy and excellent generalization performance.

Purpose: Aero-engine casings commonly use composite cylindrical shell structures with excellent properties such as corrosion resistance and fatigue resistance. Still, their vibration behavior is relatively complex and may cause fatigue vibration damage, so it is essential to analyze the vibration characteristics of composite cylindrical shells. The purpose of this paper is to analyze the vibration characteristics of multilayer composite cylindrical shells subjected to external pressures and having different interlayer thickness ratios and provide some theoretical basis for the fatigue damage prediction of cylindrical shell casing to ensure the safety and stability of the engine during flight.Design/methodology/approach: Firstly, the vibration differential equation with external pressure is established based on Soedel theory considering nonlinear effects, while four symmetric boundary conditions are chosen to constrain the cylindrical shell. Then the Rayleigh–Ritz method, which is more efficient and accurate in calculating large structural systems, is applied to solve the problem, and the theoretical model of three-layer cylindrical shell under external pressure is established. The accuracy of the model is verified by comparing the data with the specialized literature. Subsequently, the effects of different external pressures and different thickness-to-diameter ratios, different length-to-diameter ratios and different interlayer thickness percentages on the natural frequency of multilayer composite cylindrical shells were investigated by control variable analysis.Findings: The conclusions obtained show that the external pressure increases the natural frequency of the cylindrical shell and that the frequency characteristics of the cylindrical shell vary for different boundary conditions. The effect of length-to-diameter ratio, thickness-to-diameter ratio and the percentage of the thickness of the intermediate layer on the natural frequency of the cylindrical shell are significantly increased under external pressure. Because the presence of external pressure increases the frequency of the cylindrical shell by about 70%, it has almost no effect on the frequency at the minimum number of circumferential waves, and the effect on the frequency at the maximum number of circumferential waves is reduced to about 50%. The frequencies in the SL-SL boundary condition are all in perfect agreement with the S-S boundary condition under the influence of different influencing factors.Originality/value: In this paper, the effect of external pressure and the natural properties of the cylindrical shell under external pressure on the cylindrical shell’s frequency is considered, emphasizing the effect of different layer thickness ratios on the frequency. This paper aims to summarize the changing law between the natural frequency of the cylindrical shell itself and different design parameters during the flight pressure process. Reliable theoretical predictions are provided for analyzing the vibrational behavior of shells subjected to external pressures in aerospace, as well as a database for the practical production of cylindrical shells.