Browsing by Author "Wang, Luyao"

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Open Access
Application of data-driven and physics-driven models in predicting vibratory responses of nonlinear dynamic systems
(Faculty of Graduate Studies and Research, University of Regina, 2024-06) Wang, Luyao; Dai, Liming; Mehrandezh, Mehran; Aroonwilas, Adisorn; Chen, Zengtao
The investigation of chaotic vibrations is essential for understanding the vibro-responses of engineering structures subjected to external excitations. This understanding is crucial for developing advanced strategies to control chaotic structural instability and sensitivity. Traditional methods for investigating chaotic vibration behavior rely on physics-based model establishment, where physical models are mathematically analyzed through complex calculations of differential equations. Although the development of analytical and numerical theories is relatively mature, the costly human labor required for feature engineering and high demands for expert knowledge in mathematical and physical domains limit its application in engineering fields to a certain extent. Therefore, this research aims to establish an innovative approach for predicting the chaotic responses of nonlinear models in the engineering field by proposing data-driven models to accomplish supervised learning regression tasks. The application of these proposed data-driven models in predicting chaotic responses of various nonlinear system models is conducted in a completely data-driven and non-intrusive manner. This thesis implements prediction tasks for chaotic vibrations of different types of nonlinear dynamic systems based on both physics-driven and data-driven models. These nonlinear systems serve as fundamental reference models and are widely applied in various engineering fields. Specifically, the physics-based investigations in this work focus on comparing the advantages of the developed P-T method over the 4th-order Runge-Kutta method in terms of accuracy and reliability. Additionally, studies on chaotic vibration prediction based on data-driven models are also carried out in this thesis. Three hybrid neural networks are proposed, and their architectures are thoroughly explained. The effectiveness and robustness of these models are sequentially enhanced. Specifically, their ability to handle chaotic sequences has evolved from considering temporal correlations to considering spatiotemporal correlations, and their capability to manage the length of inputs and outputs has progressed from fixed to variable. Besides the inherent advantages of data-driven investigation compared to physics-driven methods, the superior performance of the proposed data-driven models over conventional benchmarks in terms of training time and testing loss is quantitatively demonstrated. The continuous development of measuring equipment has facilitated easier access to substantial high-quality data. Thus, the findings of this research provide new insights into the investigation of chaotic responses and are valuable for analyzing and understanding chaotic vibrations with greater efficiency. The optimized results obtained in this research are expected to offer practically sound guidance for optimizing engineering structural design and enhancing performance when considering chaotic or nonlinear vibrations.
Open Access
Sound Radiation Responses and Acoustic Behvior of Sandwich Panel
(Faculty of Graduate Studies and Research, University of Regina, 2019-03) Wang, Luyao; Dai, Liming; Henni, Amr; Mehrandezh, Mehran; Mobed, Nader
Sandwich structures with decent sound insulation and absorption properties have been widely used in the engineering fields such as aerospace engineering, marine engineering and civil and construction engineering. Investigations on the acoustic behavior of sandwich structures is of practical importance, not only for engineers but to researchers in the field. A numerical study of the vibro-acoustic and sound transmission loss (STL) of an aluminum honeycomb core sandwich panel with fabric-reinforced graphite (FRG) composite face sheets is performed in the present research. The honeycomb sandwich structure, faced with an FRG composite face sheet, has acoustic advantages over other types of sandwich structures commonly used in the field. The effects of different boundary conditions and geometric properties of the FRG faced honeycomb structure on the stiffness of the structure are evaluated. The effects of the stiffness on the acoustic performance of the structure are investigated. Truss core sandwich panels filled with sound absorbing materials are also studied numerically for the panels’ vibration responses and STL behavior. The performances of a polyurethane (PUF)-foam-filled truss core sandwich panel and a wood-board-filled truss core sandwich panel are compared. The wood based sandwich panel shows advantages with compatible acoustic performance and environmental-friendly characteristics over the PUF foam panel. The acoustic behavior of the wood-based porous media, with varying airflow properties, are investigated. The most significant factor affecting the vibro-acoustic responses of the panel are identified. The wood-based-porous-medium-filled truss core sandwich panel with various face sheet materials are analyzed. A truss core 2 sandwich panel is designed with the optimal combination of wood-board and face sheet materials. Numerical models, based on the sandwich theory, are established based on the assumption the sandwich core is an orthotropic structural layer. The radiated sound power from the panel is quantified with the Rayleigh integral method. A random diffuse field is used as an incident sound source and is derived with the finite element method using ACTRAN. The numerical results generated with the implementation of the models are validated with experimental data available in the literature. The findings provide guidance for selecting and designing honeycomb core and truss core sandwich panels with decent acoustic properties for engineering applications. The developed approach presents practical significance for quantitatively evaluating and designing sandwich panels with high efficiency and effectiveness, when the acoustic and vibrational performance of the panels need to be considered.