Journal of Sound and Vibration最新文献

Previous studies have paid little attention to the dynamic modeling of multi-fault systems with both bearing defect and cracked rotor. In the current research, a double-disc rotor model with a breathing crack and fault bearing was established using the finite element method (FEM). The dual-impulse phenomenon associated with inner race defect was addressed as a time-varying external excitation. The effects of varying crack depths and inner race spall lengths were further investigated. The maximum error between simulation and experiment was found to be less than 5% for the dual-impulse time spacing. The calculated results indicate that the inner race defect causes a slight increase in the rotational frequency f_rotor and 2f_rotor, followed by a decrease in the 3f_rotor at low speeds, as observed using Fast Fourier Transform (FFT) and Short-Time Fourier Transform (STFT). The influence of changes in crack depth is greater than the bearing defect in the system, a finding that is also confirmed at 1/2 critical speed. The phenomenon of frequency modulation observed in the simulation was also verified experimentally. The ball passing frequency on inner raceway f_BPFI, f_rotor and mixed frequency components can be used to distinguish whether there is inner race defect.

Rotor failures due to cracked blades are frequently observed in rotating machinery. The identification of cracking state of rotating blade based on vibration characteristics has garnered a lot of attention. However, nonlinear characteristics and vibration combining in radial, bending and torsional directions of a rotating blade induced by the crack breathing is yet not clear. This paper proposes a radial-bending-torsional dynamic model of rotating blade with breathing crack. A time-varying integration method is proposed for determining the crack state based on the strain energy release rate. The crack breathing behavior is described by Boolean operation and the numerical integration are applied to open or close the crack. The model is validated through modal analysis, vibration responses and contact state of crack surface. Frequency veering is changed between the 2nd flap and 1st edgewise frequency due to the existence of crack. Strong nonlinear behaviors are found in the radial and torsional vibrations because of the crack breathing. Nonlinearities are also found in the combined vibrations between the radial-bending and the bending-torsional directions. Radial and torsional vibration amplitude levels can be used as an indication of blade crack failure, but the applicability depends on the absolute response decided by the aerodynamic excitation and resonant vibration. These findings can serve as guidance in crack identification and cracking state monitoring of rotating blades.

The Council of European Aerospace Societies (CEAS) Aeroacoustics Specialists Committee (ASC) supports and promotes the interests of the scientific and industrial aeroacoustics community on a European scale and European aeronautics activities internationally. In this context, “aeroacoustics” encompasses all aerospace acoustics and related areas. Each year the committee highlights some of the research and development projects in Europe.

This paper is a report on highlights of aeroacoustics research in Europe in 2023, compiled from information provided to the ASC of the CEAS. In addition, during 2023, a number of research programmes involving aeroacoustics were funded by the European Commission. Some of the highlights from these programmes are also summarized in this article, as well as highlights from other projects funded by national governments and industry.

Contributions are gathered in sections by topic, and a section covering relevant European scientific events in 2023 is also included. Enquiries concerning all contributions should be addressed to the authors who are given at the end of each subsection.

We propose a data-driven technique for discovering the equation of motion of the dynamical system with rigid impact. The method first discovers a dynamical system close to impact by the Fourier series with a high rate of convergence, known as the double-even extended series. Then, we use the system to construct an impact mapping, which maps the data close to impact to an estimated impact instant. By minimizing the error of impact mapping, we find the location of impact surface and energy lost during impact that generally satisfies the data close to impact. Finally, we discover the equation of motion without impact by the double-even extended series The analyzed data can be collected at equal time intervals with measurement error, and there is no need to deliberately collect data at the impact instant. The technique is able to capture the impact characteristic when there is a lack of knowledge about the critical changes of the dynamics at the impact instant and the non-linear dynamical behaviors without impact. We test the identification ability of the new technique using impact dynamical systems connected with cubic damping term and strong non-linear damping, respectively. The identified systems accurately capture impact dynamics such as the long-time prediction with impact, multistable dynamical phenomenon, and chattering dynamics.

Nonlinear energy sink (NES) is widely applied in engineering field due to the advantages of light weight, high robustness, unidirectional energy transfer, rapid and broadband vibration isolation. In this paper, nonlinear energy sink is utilized to suppress vibration of the variable thickness porous sandwich conical shells for the first time, and the high-dimensional nonlinear flutter suppression characteristics of the system of simply supported variable stiffness truncated porous sandwich conical shell coupled NES under aerodynamic force and thermal stress are investigated. By applying the first-order shear deformation theory (FSDT), Hamilton's principle and Galerkin technique, the high-dimensional nonlinear ordinary differential flutter suppression equations of the system appended with NES are established. The accuracy of the theoretical approach is ensured by the comparison of frequency results, while the NES dissipated kinetic energy ratio and the comparison of NES performance with other suppression systems are presented to prove the effectiveness of NES on nonlinear flutter suppression. The time history diagrams and limit cycle oscillation (LCO) amplitude curves, which reflect the high-dimensional nonlinear flutter suppression effect of NES, are obtained by employing the Runge-Kutta method. The effects of aerodynamic pressure, the parameters and positions of single NES, and the positions of parallel NES and series NES on the high-dimensional nonlinear flutter suppression characteristics of the system attached with NES are discussed in depth. Finally, the optimal high-dimensional nonlinear flutter suppression scheme is arrived.

This work presents a multi-scale analytical and computational approach designed to predict the hygro-thermo-mechanical vibrational response of laminated composite structures reinforced with multi-walled carbon nanotubes (MWCNTs). Employing the modified Halpin-Tsai model, this study estimates the elastic properties of the MWCNT-enhanced epoxy matrix, incorporating the impacts of MWCNT agglomeration, orientation, waviness, and size-dependent characteristics. Additionally, the Chamis micromechanical model is utilized to ascertain the independent elastic constants of the nanocomposite lamina, considering environmental variables such as temperature and humidity. Subsequent analysis involves the determination of natural frequencies for both pristine and MWCNT-integrated laminated composite structures via the Finite Element Method (FEM), addressing various design-related parameters. This investigation further explores the macroscopic influences of MWCNT incorporation, boundary condition and layup scheme, along with the temperature, moisture content, and the nanoscopic impact of MWCNTs on the natural frequencies of laminated composite plates. The obtained results of the proposed multiscale modeling are compared with experimental and theoretical observations. It has been demonstrated that while the incorporation of carbon nanotubes (CNTs) can enhance the mechanical properties of nanocomposite laminae, the natural frequencies of these nanocomposite plates are adversely affected by variations in temperature and moisture content. Furthermore, the findings indicate that the microstructural characteristics of CNTs play a crucial role in determining the efficacy of the reinforcement phenomenon. The developed multi-scale methodological framework offers significant potential for the design and optimization of MWCNT-based composite structures across diverse industries, including automotive and aerospace sectors.

In view of the poor solution accuracy of the traditional Green's function-based load reconstruction method, this paper proposes a load reconstruction method based on an iterative solution strategy. Using Green's function matrix as the gradient information of the load and dynamic response, the load history is continuously updated to minimize the residual difference between the measured response and the reference model response to obtain a reconstruction result closer to the real load history. In addition, this paper derives a Green's function matrix based on the acceleration response time series, which extends the application scope of the traditional Green's function-based load reconstruction method. Furthermore, considering the influence of uncertainty factors such as measurement noise and model error on the reconstruction results, this paper proposes a probabilistic regularized load reconstruction method based on an iterative strategy by using probability theory to describe the uncertainty. The influence of uncertainty factors is considered both in the selection of regularization parameters and in the load reconstruction process. The effectiveness of the proposed method is verified by an example of a 35-rod truss, and the effects of model error and measurement noise on the reconstruction results are discussed. Compared with the traditional method, the proposed method can achieve more accurate and robust load reconstruction results, and the effect of uncertainty on the load reconstruction results can be quantified in the framework of probability theory.