This paper develops a universal numerical model for analyzing the vibration characteristics of a rotating bidirectional functionally graded porous cantilever beam with axially varying cross-sections. The model is formulated based on the theories of Euler–Bernoulli beam and multi-body dynamics by employing Hamilton’s principle in conjunction with isogeometric analysis (IGA) and Lagrange multiplier and Newmark-[Formula: see text] methods. The proposed model incorporates three types of axially varying cross-sections, two types of porosity distributions and two types of boundary conditions. Then, the convergence, accuracy, reliability and stability of the proposed model are verified gradually through convergence analysis and model verification. Finally, the vibration characteristic analysis of the rotating bidirectional functionally graded porous cantilever beam with axially varying cross-sections is realized by analyzing the influences of geometric parameters, material parameters, external load working conditions, and boundary conditions on the natural frequency and the root mean square (RMS) of acceleration systematically. The above investigation can offer the theoretical basis for evaluating the vibration behaviors of a rotating bidirectional functionally graded porous cantilever beam with axially varying cross-sections.

The International Civil Aviation Organization (ICAO) sets strict limits for aircraft ramp noise, a key source of which is Auxiliary Power Unit (APU) inlet noise. This paper presents a systematic and computationally efficient design methodology for APU inlet mufflers. The high-frequency noise necessitates validating a single-degree-of-freedom liner impedance model up to 10,000 Hz. The core innovation overcomes prohibitive full-passage simulation costs (days) by optimally selecting attenuation center frequencies from the source spectrum and implementing an axially segmented design. This approach enables efficient, targeted optimization (minutes per case) and leverages acoustic mode scattering at segment interfaces to enhance overall attenuation. The design is verified via high-fidelity, full-flow-path simulation. Experimental validation under various operating conditions shows good agreement with predictions, achieving approximately 9 dB reduction in overall A-weighted Sound Power Level (OASPL) with consistent performance. The results demonstrate the feasibility and effectiveness of the proposed rapid, precise, and efficient design framework.

The current work uses numerical simulation methods to evaluate the leakage and flow heat transfer of labyrinth seals while accounting for rub-groove wear. Firstly, an experimental system for investigating the leakage characteristics of labyrinth seals was established to verify that the computational accuracy of the numerical method used is suitable for this study. Secondly, in order to assess the influence of the clearance on the leakage and heat transfer coefficient distribution for the labyrinth seal with rub-groove wear, airflow velocity near the seal tooth tips is computed under different clearances. The estimated averaged heat transfer coefficient over the rotor surface reduces as the clearance decreases, owing to the lower speed vortices filled in the rub-groove. Finally, the geometric parameters of rub-groove wear (groove width and depth) are thoroughly examined in relation to flow leakage and local heat transfer coefficient distributions of the rotor for the labyrinth seal with rub-groove wear.

Aircraft surfaces often feature various geometric discontinuities, such as small cavities, slot cavities, and protrusion envelopes. The airflow interacting with these structures can generate aerodynamic noise through coupled flow-structure interactions, adversely affecting cabin acoustics and community environments. This study investigates the noise characteristics and noise-reduction strategies for these typical configurations. Findings reveal that the dominant noise source for “closed-type” shallow circular cavities originates from flow separation at the lip region and the cavity rear; for “open-type” circular cavities, self-sustained oscillation modes at the lip are predominant, with cavity internal acoustic modes playing a secondary role. In deep circular cavities, the noise-generation mechanism gradually evolves toward internal cavity modes. To mitigate the prominent tonal peaks of circular cavities, reducing energy injection or alleviating post-wall flow impingement can suppress peak noise levels by over 10 dB. Noise from protrusion envelopes is primarily caused by flow separation, exhibiting broadband characteristics. For square and rectangular protrusion envelopes, shape optimization reduces drag by more than 80

To address the characteristics of engine fan noise sources and their propagation mechanisms, this study employs a finite element method for solving time-linearized Euler equations to predict acoustic propagation in engine nacelles. The numerical approach was validated using NASA’s JT15D inlet model, demonstrating prediction errors below 3 dB. A full-scale segmented nacelle acoustic liner test article was designed and manufactured, incorporating spatial layout optimization that accounts for modal scattering and reflection effects. An experimental platform utilizing rotating modal generation technology was established to simulate realistic engine fan noise under laboratory conditions. Test results show that the peak-to-peak noise reduction of the segmented liner reaches 16.4 dB under design conditions (1,250 Hz, 15th-order mode), with a minimum 5.6 dB reduction observed across 0°–90° polar angles at 4 m radius. The axial segmentation strategy effectively enhances higher-order modal scattering absorption, providing insights for nacelle liner design and validation.

Achieving both low-frequency vibration isolation and high load-bearing capacity remains a significant challenge in traditional vibration isolator design, particularly for multi-directional applications. The research presents a novel metamaterial vibration isolator inspired by the Dougong structure in traditional Chinese architecture. The Dougong structure exhibits exceptional integrated performance in both load-bearing capacity and vibration damping. By leveraging its unique deformation mechanisms, the proposed design successfully achieves simultaneous multi-directional vibration isolation and structural load-bearing. The key innovation lies in the Quasi-Zero Stiffness response achieved through controlled deformation of the Gong element, which enables broadband low-frequency vibration isolation while maintaining mechanical stability. Numerical simulation and experimental results confirm that this structure has effective low-wideband vibration isolation characteristics. This research establishes a novel paradigm for the design of multifunctional vibration isolation metamaterials, thereby advancing the development of multi-directional vibration isolators with enhanced load-bearing capabilities.

The use of composite materials in aerospace and other fields is more and more widespread. The structural response and fatigue characteristics of composite materials under vibration load are more concerned. In this paper, the vibration fatigue test is carried out with the typical composite structure as the research object, and two failure modes and vibration fatigue S–N curves of the typical composite structure are obtained. It can provide technical support for anti-vibration fatigue design of structure.

Rainbow trapping effect, essential for flexural wave energy localization in elastic metamaterials, is typically constrained to a single mechanism with low efficiency. This study proposes a sinusoidal-profile nonuniform metamaterial beam to achieve multipathway rainbow trapping via both band gaps and interface states. A theoretical model based on Timoshenko beam theory is developed and solved using the differential quadrature method (DQM), which accurately predicts the evolution of the first band gap in periodic nonuniform beams. The results are systematically verified by comparison with finite element simulations. Leveraging the band gap characteristics, a nonuniform metamaterial beam is designed to achieve rainbow trapping. Excitation with eight frequency-matched segments results in distinct flexural wave energy concentration due to the band gap effect. Furthermore, a mirror-symmetric supercell composed of unit cells with opposite geometric parameters reveals two distinct interface states. These states enable strong flexural wave localization at the corresponding interface positions when excited at the respective interface state frequencies. By combining band gap and interface state effects, an optimized metamaterial beam simultaneously achieves two independent rainbow trapping mechanisms. This study demonstrates multipath regulation beyond single-mechanism designs, providing a basis for developing high-performance elastic wave localizers, filters, and smart metamaterials.

IntroductionCompressor blades in aero-engines are subjected to complex thermo-mechanical-vibration interactions under service conditions, with foreign object damage (FOD) further exacerbating fatigue failure risks. To accurately evaluate the high-cycle fatigue performance of blades under combined thermo-mechanical fatigue (TMF) and FOD in operational scenarios, this study developed a multi-physical coupled test system to simulate realistic service environments for rotating components.MethodsA multi-physical coupled test platform was constructed to synchronously simulate thermo-mechanical-vibration interactions. The system achieves centrifugal load and temperature control with an error margin within 1%, while providing high-frequency vibration loading at 1,600 Hz with large displacement, accurately replicating the dynamic stress states of blades during operation. Experiments were conducted on GH4169G compressor blades with prefabricated FOD, systematically investigating synergistic fatigue effects under combined thermal, centrifugal, and vibrational loads.ResultsExperimental results indicate that under combined thermo-mechanical-vibration fatigue loading, low-cycle centrifugal load exerts the most significant influence on fatigue performance, followed by thermal load, with high-cycle vibration load having a relatively lesser effect. Foreign object damage markedly reduces fatigue strength, while an increase in the low-cycle load ratio moderately enhances both fatigue limit and fatigue life. The data further reveal interactive mechanisms of crack initiation and propagation under coupled loading conditions.DiscussionHe proposed multi-physical coupled testing methodology provides direct technical support for experimental evaluation, strength assessment, damage-tolerant design, and condition-based maintenance of aero-engine compressor blades. The findings emphasize the critical need to consider the coupling effects of low-cycle mechanical loads and FOD in fatigue design, offering experimental foundations for future fatigue resistance optimization and life prediction models. This approach can also be extended to multi-axial fatigue reliability studies of other rotating components.

To elucidate the damping mechanism of platform dry friction dampers for turbine blades and optimize their design parameters, this study establishes a two-dimensional global-local unified sliding dry friction damping model. This model comprehensively accounts for the blade's bending-torsion coupling vibration characteristics and the dual-state behavior of the damper, encompassing both stick and slip phases. An iterative solution strategy combining finite element methods with in-house developed programs is employed to simulate the vibration response of turbine blades equipped with dampers under multiple loading conditions. The influence of normal pressure and dimensionless normal pressure on the blade's vibration characteristics, equivalent stiffness, and equivalent damping is systematically analyzed. To validate the reliability of the simulation results, a dedicated test platform capable of independently simulating centrifugal force effects was constructed, and modal tests as well as vibration response tests were conducted. The results demonstrate that the proposed model accurately describes the nonlinear energy dissipation behavior of dry friction damping, providing a reliable theoretical basis for blade vibration response analysis. Dimensionless normal pressure is identified as a key parameter influencing vibration reduction effectiveness. The resonant amplitude of the blade exhibits a non-monotonic trend, initially decreasing and then increasing with rising dimensionless normal pressure. The optimal dimensionless normal pressure range is found to be 20-30, within which the blade vibration amplitude can be reduced by more than 50%. Experimental verification confirms that the vibration reduction and energy dissipation mechanism of the damping block aligns closely with simulation results, achieving a maximum vibration reduction of 72.6%. Moreover, the optimal dimensionless normal pressure values correspond well with simulation predictions. Based on the optimal dimensionless normal pressure, a forward design method for platform dampers is proposed, which can provide theoretical support and engineering guidance for the optimal design of vibration reduction structures in aero-engine turbine blades.

The damage monitoring methods in aircraft strength tests are based on manual inspection, and nondestructive testing and health monitoring are used to monitor the status of the test process. These methods have the disadvantages of low monitoring efficiency and high sensor installation requirements. Structural damage or damage precursors have a short-term impulsive behavior, and thus, this paper proposes an acoustic-based monitoring method, which combines microphone arrays and acoustic imaging algorithms for abnormal sound localization. Experimental validation and application are carried out on the composite material tensile fracture test and full-scale load carrying capacity test, and the conventional beamforming with diagonal removal (CBF-DR) algorithm and the orthogonal matching pursuit with singular value decomposition (OMP-SVD) algorithm are studied. The experimental results show the proposed acoustic-based method can monitor the short-term impulsive sound that characterizes the fracture and tearing, accurately capturing the structural response in the complex reverberant aircraft strength test environment. The OMP-SVD algorithm is rarely affected by the main lobe width and side lobe levels in different frequency ranges compared with the CBF-DR algorithm. It has better localization performance for multiple and reflected abnormal sound sources with different intensities.

A method of sealing system design as part of the secondary air system for aircraft engines is proposed in this paper. It allows for the computation of the seal leakage flow rate, depending on the thermal state of the rotor and stator, and combines accounts of pressure loss, heat transfer, stress, and deformation conditions using the ther-mal-fluid-structural coupling method. As calculation examples were chosen for the HPC aft hub sealing system in the secondary air system of the NK-93 engine, the wall temperatures of the high-pressure system components predicted by the simulation are compared to those retrieved from a thermal model of the real engine, and the results are discussed with different radial clearances of the HPC aft hub seal influencing the leakage performance and flow direction of other neighbor seals in HPT.

Ultrasonic fatigue testing is an important method for studying the long-life fatigue properties of materials, and the analysis of specimen resonance frequency is a prerequisite for conducting ultrasonic fatigue tests. Based on the geometric characteristics of ultrasonic fatigue specimens, the electromechanical analogy method was employed to derive the impedance expressions for both uniform cross-section cylinders and tapered transition sections. An equivalent circuit model for the ultrasonic fatigue specimen was established, presenting the frequency equation of the specimen and solving for its theoretical resonance frequency. The results show that the electromechanical analogy model has high accuracy in predicting the resonance frequency of ultrasonic fatigue specimens, with a relative frequency deviation within 2 %. Additionally, approximating the arc transition segment with a catenary is feasible. Both geometric and material parameters significantly affect the specimen frequency, with the radius of the small-diameter cylindrical segment having the greatest impact. The electromechanical analogy method provides an effective approach for frequency analysis of ultrasonic fatigue specimens, supporting the highprecision design of ultrasonic fatigue tests.

To address the very high cycle fatigue（VHCF）issue of GH4169 nickel-based superalloy，which is widely utilized in aero-engines，a fatigue specimen subjected to 20 kHz ultrahigh frequency vibration is designed and tested utilizing a piezoelectric ultrasonic fatigue testing system. At room temperature，the P-S-N curves for VHCF of GH4169 nickel-based superalloy are obtained under various survival probabilities of 5%，50%，and 95%. The experimental findings reveal that the GH4169 material’s curve exhibits a downward trend when the fatigue life attains 107 cycles，indicating the absence of a fatigue limit and the persistence of fatigue failure. Fracture analysis results indicate that the majority of VHCF cracks initiate from the surface or subsurface of the specimen，with both single-source and multi-source cracking observed. The cracking modes encompass surface sliding cracking and non-metallic inclusion-induced sliding cracking.

To gain a more comprehensive understanding of the rub-impact dynamics and failure mechanism between the high-speed rotor blade and static casing of an aero-engine, numerical simulations of the rubbing process and response characteristics of the rotor-disc-casing coupling system are conducted. These simulations are based on the harmonic equilibrium method, combining implicit-explicit analytical approaches from both theoretical and finite-element analysis perspectives. The simulation results are subsequently validated through comparison with experimental findings. Building upon this foundation, the factors influencing the rubbing response are further analysed, including variations in clearances between the rotor and stator, different stiffness ratios, and diverse rotational speeds. The conclusions drawn and the proposed methodology contribute to an enhanced understanding of the physical phenomena and principles of blade-casing rub-impact, thereby providing a valuable reference for the fault diagnosis of rubbing phenomena in engineering applications.

To fulfill the requirements for researching and validating the acoustic characteristics of aviation acoustic liners across a wide frequency range, a flow tube acoustic test bench was developed, employing the three-dimensional straightforward method (3D-SFM) and the pipe acoustic mode decoupling approach. In a grazing flow environment with a maximum Mach number of 0.14, the acoustic performances of single- and double-degree-of-freedom acoustic liners, including acoustic impedance and sound transmission loss, were tested. The maximum test frequency could reach 10 kHz, covering the main noise frequency bands of aeroengines and auxiliary power units. The experimental results demonstrate that the 3D-SFM can effectively educe the acoustic impedance of the acoustic liner in a multi-modal sound field. Furthermore, based on spanwise mode decomposition and the Prony method, the optimization principle and methodology were proposed to optimize acoustic impedance under multiple spanwise modes and scattering modes. The final acoustic impedance outcomes exhibited excellent consistency with the prediction of liner's impedance model. Sound transmission loss was capable of reflecting the variation law of the noise reduction capability of single/double-degree-of-freedom acoustic liners under different Mach numbers of grazing flow, as well as the advantages of double-degree-of-freedom acoustic liners in broadband noise reduction.

The articulated multi-link system is the primary mounting configuration for aircraft turbofan engines, consisting of multiple spherical hinge joints and links. As a critical structural interface, its dynamic characteristics directly influence engine-to-cabin vibration/noise transmission. To mitigate this transmission, optimization of the mounting system’s vibration isolation performance is essential. This study investigates a turbofan engine mount. The system was modeled using multi-body dynamics, with spherical hinge joints represented via Hertz contact and Coulomb friction models. First, a parametric sensitivity analysis was conducted on system vibration transmissibility across the engine operational frequency range to identify dominant influential parameters. Second, the MIGA algorithm was applied to optimize the main sensitive parameters across the engine operational frequency spectrum. After optimization, the isolation efficiency of the mounting system was significantly improved in all directions across the frequency range. Under random excitation, the system’s global vibration isolation performance metrics were well maintained across the entire operational frequency spectrum. Innovation Highlights: (1) The study achieves enhanced isolation efficiency and robustness through optimized system design. (2) It explicitly incorporates nonlinear contact interactions and frictional effects in spherical hinge joints. (3) It quantifies broadband vibration transmissibility using auto-power spectrum analysis. This study’s conclusions pave the way for the practical implementation of optimized parameter design methodologies in turbofan engine mounts.

This study presents a level set-based topology optimization method for finite phononic crystals. To minimize the wave transmission on the boundary of the output domain, the adjoint method is employed to derive the topological derivatives. The boundary element method is then utilized to efficiently solve both the original and adjoint elastic dynamic problems, allowing for effective handling of boundary conditions. The boundaries of the material region are described by the zero-contour line of the level set function. Within a finite periodic unit, the optimization is performed, and numerical examples are provided for different frequency ranges. The results show that the proposed method can significantly reduce the wave transmission at a specific frequency and exhibit good vibration isolation performance. The vibration isolation effect can be increased by increasing the number of optimized layers, but the attenuation band gap is not necessarily enlarged. A parameter is also investigated for its influence on structural complexity, demonstrating that appropriate adjustment can balance geometric complexity and engineering feasibility. This method provides an effective means for the optimal design of phononic crystals and has the potential to be extended to a wider range of elastic metamaterial design problems.

The modal damping ratio is a critical factor influencing vibration fatigue characteristics. Its determination plays a significant role in structural vibration fatigue analysis and simulation, and provides direct insights into the mechanism of vibration fatigue damage in metallic materials. This study selected 2024-O aluminum alloy, a typical aviation metallic material, and conducted extensive component-level vibration fatigue tests and simulation analyses. A novel method for obtaining the modal damping ratio during vibration fatigue processes was proposed, based on finite element analysis (FEA). This method is suitable for capturing the evolution of modal damping ratios in component-level structural vibration fatigue. The results demonstrate that the proposed approach can accurately determine the modal damping ratio throughout the vibration fatigue process without interrupting the tests, thereby laying a foundational basis for further elucidating the mechanism of vibration fatigue damage in metallic materials.