Qingtao Gong

Cylinder–plate combined structures (CPCS) are widely used in aerospace, marine engineering, and offshore platform systems. During service, they are frequently subjected to stochastic excitations induced by turbulent boundary layers, acoustic loads, hydrodynamic disturbances, and broadband operational vibrations. Excessive random vibration responses may significantly reduce structural reliability, accelerate fatigue damage, and compromise operational safety. To address these engineering challenges, a unified stochastic dynamic analysis and vibration suppression framework is established for functionally graded graphene platelet-reinforced composites (FG-GPLRC) CPCS equipped with distributed dynamic vibration absorbers (DVAs). Adopting the First-order Shear Deformation Theory (FSDT), a comprehensive energy functional for the CPCS is established, in which the penalty method is implemented to impose boundary conditions and ensure interface continuity. Subsequently, the Pseudo-excitation Method (PEM) is utilized to convert the stochastic vibration analysis into an equivalent deterministic harmonic problem, and the governing equations are spatially discretized by combining the spectral geometric method (SGM) with the Ritz variational procedure, enabling efficient evaluation of power spectral density (PSD) and root-mean-square (RMS) responses. The reliability of the proposed model is verified through a series of numerical validation comparisons. On this basis, comprehensive parametric investigations are conducted to assess how material properties, structural geometries, and critical DVA parameters influence system behavior. The results demonstrate that the incorporation of distributed DVAs can achieve superior vibration suppression performance. This study provides an efficient and reliable theoretical framework for stochastic vibration analysis and damping design of advanced composite plate–shell coupled structures operating in complex random environments, offering important theoretical support for dynamic optimization design in aerospace and marine engineering applications.

This paper seeks to establish a generalized numerical model to examine the free vibration behavior of functionally graded porous (FGP) elliptical shells and panels with various boundary types. The model is built on first-order shear deformation theory (FSDT) to express structural displacements. A segmentation technique is used to maintain continuity between shell elements, and virtual spring boundary techniques are employed to simulate arbitrary boundaries. Variable-coefficient Jacobi polynomials are introduced as admissible functions for displacement. Finally, the Ritz variational method, combined with the least-squares weighted residual method (LSWRM), is used for constructing the energy functional and solving the energy equations. Validation of the numerical model against finite element and literature results confirms its reliability and convergence properties. This study also explores the effects of geometric parameters and boundary conditions on FG elliptical shells and panels, providing a theoretical basis for future research.

Under shut-in conditions in deepwater drilling, the gas invading the bottomhole ascends along the wellbore and accumulates at the wellhead, forming a high-pressure trap, challenging wellbore pressure prediction and control. The accurate prediction of bottomhole pressure is essential for well control during shut-in conditions. In this study, a new bottomhole pressure prediction model that considers wellbore storage effects was developed to address gas invasion issues during shut-in conditions in deepwater drilling. This model incorporates factors such as the wellbore elasticity, fluid compressibility, and drilling fluid filtration loss. The calculated values show good agreement with experimental values, with the average absolute and relative errors of 2.095 × 10⁻² MPa and 3.71%, respectively. Meanwhile, the results indicate that the bottomhole pressure initially increases logarithmically over time and then transitions to a linear increase, and the residual flow and gas ascent significantly influence the bottomhole pressure. Finally, the effects of various parameters on the bottomhole pressure were evaluated. Larger initial pressure differential, exposed thickness, and formation permeability accelerate the increase in bottomhole pressure during residual flow stage, while smaller filter cake permeability and drilling fluid viscosity quicken its increase during gas ascent stage. Drilling fluid density affects the initial pressure and the residual flow duration. The findings of this study would provide theoretical support for well control operations in deepwater drilling.

This study introduces a novel analytical framework for investigating the vibration characteristics of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) elliptical cylindrical shells under arbitrary boundary conditions. Unlike previous studies that focused on simplified geometries or specific boundary conditions, this work combines the least-squares weighted residual method (LSWRM) with an adapted variational principle, addressing high-order vibration errors and ensuring continuity across structural segments. The material properties are modeled using an extended rule of mixtures, capturing the effects of carbon nanotube volume fractions and distribution types on structural dynamics. Additionally, virtual boundary techniques are employed to generalize elastic boundary conditions, enabling the analysis of complex boundary-constrained structures. Numerical validation against existing methods confirms the high accuracy of the proposed framework. Furthermore, the influence of geometric parameters, material characteristics, and boundary stiffness on vibration behavior is comprehensively explored, offering a robust and versatile tool for designing advanced FG-CNTRC structures. This innovative approach provides significant insights into the optimization of nanoscale reinforced composites, making it a valuable reference for engineers and researchers in aerospace, marine, and construction industries.

As oil and gas exploration gradually advances into deep waters, the combined effects of various types of gas kick and the accurate calculation of the gas-kick volume have gained increasing attention. This study focused on gas kicks from permeable gas-bearing formations, considering the mass transfer of gas in the filtration region of the drilling fluids and revealed the mechanisms of seepage-driven and diffusion-driven gas kicks. Based on seepage mechanics and diffusion theory, a comprehensive model for calculating gas-kick volume was established, considering the synergistic effect of gas-concentration-diffusion and negative-differential-pressure, as well as mass transfer in both the filtrate zone and the filter-cake zone. The new model showed high calculation accuracy. The sensitivity analysis showed that both the seepage-driven and diffusion-driven gas-kick volumes in the wellbore increased with increasing formation porosity and open-hole length, while the thickness of the filter cake had a strong inhibitory effect on both. Additionally, a “seepage–diffusion ratio” was introduced to reveal the gas-kick evolution pattern under a seepage–diffusion mechanism. Under specific case conditions, when the seepage–diffusion ratio was less than approximately 1%, diffusion-driven gas kick contributed more than seepage-driven gas kick; when the seepage–diffusion ratio exceeded 1%, seepage-driven gas kick contributed more than diffusion-driven gas kick. The research can provide crucial parameters for wellbore multiphase flow calculation and wellbore pressure prediction.

A composite anti-disturbance stabilisation control scheme is presented for the ship-borne platform system with completely unknown disturbances. The completely unknown disturbances consist of external time-varying disturbances and norm-bounded unmodelled dynamics. The composite anti-disturbance control scheme is built through integrating the nonlinear disturbance observer and the robustifying term with the vectorial backstepping technique. The nonlinear disturbance observer is designed to provide the on-line estimations of external time-varying disturbances such that the disturbance compensation term is introduced into the control design. The robustifying term with the adaptive law is employed to attenuate norm-bounded unmodelled dynamics. On the basis of the vectorial backstepping technique, the composite anti-disturbance control law is derived. The composite anti-disturbance control structure consists of the outer layer with the nonlinear disturbance observer for external time-varying disturbance cancellation as well as the inner layer with the vectorial backstepping control together with the robustifying term for unmodelled dynamic attenuation. By means of the Lyapunov stability theory, it is proven that the composite anti-disturbance stabilisation controller can achieve the disturbance rejection and attenuation simultaneously. It is verified by illustrative simulations that the composite anti-disturbance stabilisation control scheme can effectively stabilise the ship-borne stabilisation platform.

Hydroacoustic radiation from submarine power compartments has been the focus of research for many years. In this work, a ring-stiffened conical shell with bases is employed as the target model. The self-factors of viscoelastic damping, such as the damping thickness and damping location, are selected to study their effect on the underwater acoustic radiation, which will give a better understanding of the optimal scheme for applying damping. Firstly, based on a combination of finite element method (FEM) and boundary element method (BEM), the underwater vibration and acoustic radiation of the whole structure are analyzed. Secondly, taking a clamped-free sandwich beam as an example, through comparison with the published numerical data, the present damping application method and mesh density are verified. Finally, the influence of viscoelastic damping parameters on acoustic radiation is studied. The results show that the viscoelastic damping thickness has a significant influence on the amplitude of radiated noise but does not change the distribution of the acoustic field. Furthermore, the damping on the web may achieve the best vibration damping effect in this work.

With the increasing scale, complexity and diversity of supporting equipment of offshore platform, the low-frequency vibration of equipment such as dynamic positioning system and the main engine is difficult to attenuate in the propagation process of the platform structure, which causes a local resonance of platform, aggravates the fatigue damage of structure and causes discomfort to the human body. Dynamic vibration absorption is widely used in the low-frequency vibration control of offshore platforms; however, there is little research about the multiline spectrum vibration control method in the local resonance region of platforms. In the current research, we first take the stiffened plate under multipoint excitation as the research object, and the effectiveness of the optimal homology design method of dynamic vibration absorption is verified. Subsequently, the low-frequency multiline spectrum vibration control method about the local resonance region of the offshore platform is proposed. Finally, a large offshore platform is chosen as the research object and the measured load of the main engine is taken as the input to calculate the vibration response of the platform. The effect of distributed dynamic vibration absorption of the resonance area verifies the effectiveness of the vibration control method presented in the article and provides a basis for the engineering application. Graphical abstract

The transient impact load during the launch of a rocket at sea threatens the safety of the launcher and the deck structure of the launch platform. In view of the impact resistance of the offshore rocket launcher system, this paper takes the real-scale rocket launcher system as the research object and establishes the analysis model of the fiber-reinforced composite rocket launcher based on the finite element method. Then, we explore the factors of the thickness by finite element simulation method and the angle and the position of IM7 fiber-reinforced composite, which influence the impact resistance property of the rocket launcher. The results show that the fiber-reinforced composite rocket launcher can effectively reduce the impact response of the structure and improve the impact resistance of the structure. The best laying scheme is to lay four layers of IM7 fiber material on both sides of the panels of the fixed bracket and the webs of the erector, respectively, with a single layer thickness of 0.75 mm and a laying angle of [90°/∓45°/90°].