Mechanical vibration devices such as AcceleDent have been marketed as non-invasive adjuncts capable of accelerating orthodontic tooth movement. The proposed mechanism involves the stimulation of cellular activity and bone remodeling. The aim of this study was to determine whether the use of AcceleDent, in combination with clear aligner therapy, produces a measurable increase in the surface temperature of intraoral tissues. Twenty-two adult patients (mean age: 39 ± 15 years) undergoing orthodontic treatment with clear aligners (Invisalign) participated in this crossover study. Infrared thermography (A35, FLIR, Wilsonville, USA) was used to record temperature measurements of gingival and dental surfaces. Each participant underwent two experimental conditions on separate days: (1) wearing the AcceleDent device while active (vibrating) and (2) wearing the same device inactive (non-vibrating). After a 20-minute thermal acclimatization period, the device was applied for 20min before imaging. No statistically significant differences were observed in surface temperature between the vibrating and non-vibrating conditions (Gingiva: p = 0.69; Tooth: p = 0.76). Likewise, no significant differences were detected at baseline between the two sessions (Gingiva: p = 0.35; Tooth: p = 0.57). The use of AcceleDent vibration during clear aligner therapy does not result in an increase in the surface temperature of gingival or dental tissues, as measured by infrared thermography. This study provides evidence that AcceleDent vibration does not produce thermal changes in intraoral tissues, suggesting it is thermally safe for use alongside clear aligners. Infrared thermography may serve as a non-invasive tool to monitor physiological effects of orthodontic devices.

This study presents experimental investigation of vibration-induced fatigue characteristics on cellulose nanocrystals (CNCs) reinforced glass fiber reinforced polymer (GFRP) laminated composite sandwich beam with 3D printed honeycomb core. These types of lightweight composite structures are extensively used in aerospace, civil, and automobile applications. The incorporation of biodegradable and sustainable CNC introduces a novel reinforcement strategy that not only enhances the mechanical strength and vibration tolerance of advanced polymer composites but also promotes an eco-efficient alternative to conventional synthetic nanofillers. The GFRP laminates were fabricated using the hand lay-up technique, and polylactic acid (PLA) honeycomb core was additively manufactured using 3D printing. The material properties of the CNC/GFRP laminate and the core were theoretically estimated using the Halpin–Tsai model and the alternative dynamic method (ADM) approach, respectively. Then, numerical free and forced vibration analysis were conducted to evaluate the fundamental frequency on the sandwich beam and the results were validated by experiments and literature. Further, experimental vibration fatigue analysis using an electrodynamic shaker revealed that CNC reinforcement significantly improves stiffness and fatigue tolerance. It reflected in the findings, where the CNC reinforced GFRP sandwich beam exhibits lower frequency and damping ratio reduction rate of 4.13% and 25.27%, respectively, than the GFRP sandwich beam.

Research on the dynamic characteristics of roadbeds has primarily focused on traffic loads and foundation treatment responses during the operation and maintenance phase. However, there remains a lack of in-depth exploration into vibration compaction during the construction phase, particularly the differences in stress paths under roller dynamic loading. Laboratory dynamic triaxial tests are limited by low-frequency loading, making it difficult to simulate real-world roadbed compaction conditions. Therefore, this study employs discrete element numerical simulation technology to construct a numerical model for subgrade compaction under roller dynamic loading. It aims to reveal the macro- and micro-scale evolution patterns of soil under compaction conditions, thoroughly analyze the influence of factors such as roller frequency and vibratory force on subgrades with varying rock content in soil–stone mixed fill, and provide a theoretical foundation for intelligent compaction (IC) of soil–stone mixed subgrades in subsequent research.

The environmental adaptability of outdoor power connectors exerts a crucial influence on the reliability of electrical systems. In this work, the current-carrying performance degradation of commercial power connectors under forced mechanical vibration conditions is investigated comprehensively. The variations in the instantaneous electrical contact resistance (ECR) of power connectors are accurately recorded in real time, and then effects of vibration amplitude, frequency, and load current on the ECR are interpreted explicitly. Furthermore, multi-cycle swept-sine vibration tests are carried out, and the open circuit failure of power connectors is reproduced. The continuous carrying of a heavy current combined with the mechanical fretting between socket and plug results in surface coating wear, debris melting, and the formation of copper oxide. The observed surface morphology and element contents support the presented failure mechanisms of power connectors under external vibrations.

Utilizing optic fiber interferometry in forced vibration experimentation for educational purposes

Critical flutter wind velocity of flexible photovoltaic support structure with large tilt angle based on sectional forced and free vibration wind tunnel tests

The relevance of this study is due to the critical dependence of the domestic marine engine industry on imported torsional vibration damping technologies, exacerbated by the cessation of supplies and maintenance of foreign spring and silicone dampers. The creation of domestic dampers is of particular importance in the light of the tasks of technological sovereignty of the Russian state. Comparative laboratory tests of spring and silicone dampers were carried out to quantify the effectiveness of damping torsional vibrations. A silicone damper and a prototype of a spring damper developed on the basis of the author's creation methodology using reverse engineering technology of a serial sample of a spring damper model D90/37 from Geislinger are being investigated. The criterion of effectiveness was a decrease in the amplitude of torsional vibrations, estimated by the magnitude of stresses in the shafts of the laboratory stand, depending on the frequency of forced vibrations and the frequency of rotation of the stand. It was found that in the range of stand rotation frequencies up to 250 min–1, the efficiency of the dampers is comparable (voltage reduction by 2.3-3.5 times for non-resonant and up to 9.7 times for resonant vibrations). At a frequency of over 250 min–1, the prototype spring damper is more efficient, reducing the voltage amplitudes by 1.8 times compared to 1.4 times for a silicone damper. The most dangerous defects were identified: for the prototype spring damper, the leaf springs were blocked, leading to a 4-fold increase in stresses; for the silicone one, the flywheel mass was blocked, causing a 2.8-fold increase in stresses. The obtained results can be used in the creation of domestic analogues of dampers and the development of a technique for non-selective diagnostics of their technical condition.

ABSTRACT This article presents a comparative study of the computational characteristics of Finite Element Analysis (FEA) and Isogeometric Analysis (IGA) in studying large elastic deformations and large‐amplitude vibrations of shell‐type structures. A geometrically nonlinear seven‐parameter shell model is employed in a Lagrangian description in which the shell deformation is represented in mid‐surface. Using a curvilinear coordinate system suitable for various geometries, the kinematic and kinetic of the problem are established, and Hamilton's principle is applied to derive the governing equations. The strain–displacement relationships and consequently, the remaining variational formulations are expressed in a matrix‐vector form, allowing for direct implementation in both FEA and IGA. This efficient formulation enables a fair and consistent comparison between the two methods. Several numerical examples are examined, including the well‐known static benchmark problems and their corresponding forced vibration analyses. The primary contribution of this article is the demonstration of the computational efficiency of isogeometric analysis in challenging case studies of geometrically nonlinear shells. Additional novel contributions include deriving a unified formulation for seven‐parameter FEA and IGA shell models as well as analyzing the large‐amplitude free and forced vibrations of shells.

Abstract A numerical simulation has been carried out to evaluate the effect of Rayleigh damping on the efficiency of passive suppression of free and forced harmonic vibrations of a thin plate using piezoelectric element connected to a passive electric circuit of different configurations. The solution is constructed using a finite element algorithm, which is developed in the context of the proposed mathematical formulation. It has been found that the efficiency of the considered method of vibration damping decreases with increasing contribution of another dissipative mechanism existing in the system.

Structural changes within materials often indicate potential damage caused by design flaws, fabrication errors, overloading, natural events, or aging. Cracks, a common type of defect resulting from fatigue or mechanical stress, can propagate under cyclic loading and lead to structural failure if undetected. Monitoring natural frequency variations provides a reliable, non-destructive method for detecting such defects. This study investigates the influence of crack size on the natural frequencies of a cantilever beam using analytical, numerical, and experimental approaches. Analytical modeling is based on Euler–Bernoulli beam theory, numerical simulations are carried out in COMSOL Multiphysics, and experimental validation is performed using a copper cantilever beam subjected to both free and forced vibration tests. Results show that increasing crack size reduces the natural frequency due to local stiffness degradation. The close agreement among analytical, simulation, and experimental findings demonstrates the effectiveness of frequency-based monitoring as a practical tool for structural health assessment.

Abstract To address the future demand for higher-precision angular vibration detection and measurement, this paper proposes a multi-channel series magnetohydrodynamics micro angular vibration sensor. The focus lies on analyzing the sensor’s output characteristics and resolving the issue where existing models fail to accurately describe low-frequency behavior. From the perspective of initial prototype development, this paper presents an analytical method for estimating magnetic induction intensity in the sensitive region through theoretical analysis. Additionally, for axially structured magnetohydrodynamics micro angular vibration sensors, an accurate mathematical model for analytical calculations is established using the complex amplitude method and separation of variables. Finite element analysis was employed to verify the sensor’s magnetic field distribution and fluid flow characteristics, while practical tests were conducted to examine its scale factor and phase difference. These two approaches collectively validate the accuracy of the theoretical analysis. Experimental results demonstrate that the proposed analytical calculation method for magnetic induction intensity in the sensitive region offers guiding significance for engineering design. Furthermore, the analytical model of frequency response exhibits a high degree of fitting across the full frequency range, enabling accurate description of the output frequency characteristics of axially structured sensors with broad applicability.

We discuss flow-induced vibrations of an equilateral triangular prism confined to travel on a circular path when placed in the concave or convex orientations with respect to the flow. In each orientation, we consider three different initial angles for the prism. In Case 1, one side of the prism sees the flow first; in Case 2, one sharp edge sees the flow first; and in Case 3, one side of the prism is parallel to the incoming flow. We show that the response of the structure as well as the observed wake depend heavily on both the orientation and the initial angle of the prism. Case 1 exhibits vortex-induced vibration (VIV) in the concave orientation and galloping in the convex orientation. Case 2 does not oscillate in the concave orientation; however, oscillates about a mean deflection after a critical reduced velocity in the convex orientation. Case 3 exhibits small-amplitude oscillations in the concave orientation about a mean deflection, while in the convex orientation, exhibits VIV at low reduced velocities, followed by an asymmetric response with VIV features in a half-cycle and galloping features in the other half, and divergence at higher reduced velocities. These different types of responses are accompanied by a myriad of vortex patterns in the wake, from two single vortices shed in the wake in each cycle of oscillations to two vortex pairs, two sets of co-rotating vortices, and a combination of single vortices and vortex pairs depending on the prism’s orientation and its initial angle.

In this paper, the discharge structure of an Ar/SF6 inductively coupled plasma (ICP) at the low pressure is investigated by the fluid simulation at the quasi- cold ions approximation. The structure is found to be hierarchal and in this simulated hierarchy, the stratification, the parabola profile in the stratified core, the double layer, and the coagulated profile in the core center are examined. This fluid simulation version and a quasi- fluid simulation of an Ar/CF4 ICP given by the HPEM code, cooperatively enlighten the discharge structure of highly electronegative ICPs and meanwhile suggest the potential applications of them. It is found that when the ions are cold the hierarchy is predicted and when the ions are thermalized the simple discharge structure appears. In the simulated hierarchy, the double layer formed at the interface of halo and core is given by the ionic and acoustic vibrations. The main characteristic of self-coagulation is exhibited, i.e., the bigger is the coagulated volume, the denser is the coagulated mass. This provides insights for creating possibly the free nuclear fusion by means of self-coagulation, and this type of nuclear fusion without the inertial and magnetic constrictions is achieved by means of the compressible heating scheme. The self-coagulation turns the discharging and collisional plasmas into the collisionless and astrophysical plasmas, in which the double layer and ionization instability occur.

This study employs direct numerical simulation to investigate the two-degree-of-freedom vortex-induced vibration (VIV) of a circular cylinder via the immersed boundary method. The wake structure characteristics and hydrodynamic coefficients of VIV are compared with those of forced vibration under the identical cross-flow and in-line amplitudes as well as the same phase difference between the cross-flow and in-line vibrations, to validate the similarity between the forced vibration and VIV. The results demonstrate that the characteristics of forced vibration align closely with those of VIV at the same Reynolds number when the amplitudes and phase difference are consistent. In addition, the effect of phase difference is further examined in the forced vibration. When the dimensionless cross-flow amplitude exceeds 0.59, varying the phase difference leads to the alteration of vortex shedding mode. Four vortex shedding modes are identified: 2S (two single vortices are released per shedding cycle), 2P (two pairs of counter-rotating vortices are released from the upper and lower sides of the cylinder per shedding cycle), P+S (a single vortex and a pair of counter-rotating vortices are released from the cylinder per shedding cycle), and P+S− (two pairs of counter-rotating vortices are released from the upper and lower sides of the cylinder per shedding cycle, and the secondary vortex on one side is weaker than the other side and dissipates within the subsequent 1–2 cycles, which is a newly observed mode). The existence of P+S− mode is further verified using dynamic mode decomposition method. The curve of the mean energy transfer coefficient of VIV coincides with that of forced vibration, providing further evidence that the forced vibration can be effectively used to predict VIV.

Abstract This study aims to provide a semi‐analytical solution for the geometrically nonlinear vibrations of two identical, homogeneous, isotropic beams, clamped at their ends, coupled by several double spring‐mass systems, and subjected to harmonic excitation forces. The analysis is conducted within the framework of Euler‐Bernoulli beam theory and Von Kármán's geometric nonlinearity assumption. After solving the linear formulation using the iterative Newton‐Raphson method, the nonlinear formulation is obtained by applying an approach based on Hamilton's principle combined with a multimodal method for nonlinear vibrations with large displacements. This approach has been successfully used in previous studies for continuous beams, plates, and nanostructures. Although nonlinear vibrations of coupled beams have received limited attention in the literature due to their complexity, this work represents the first application of this methodology to such coupled systems. New findings were obtained by applying this approach to analyze the nonlinear behavior of coupled beams. The results indicate that, at a dimensionless amplitude of 1, the frequency ratio increases by 4.23% for a system with a single double spring‐mass, and by 3.96% for a system with three double spring‐mass. Finally, an in‐depth parametric study was performed to evaluate the influence of the number of coupling systems, the spring stiffness constants, and the mass connecting the double spring in the free vibration case, as well as the influence of the intensity of concentrated or distributed harmonic forces in the forced vibration case. This research provides new insights for the design of coupled beam systems and also contributes novel quantitative results to the literature, which can serve as a solid reference for future studies.

An efficient domain decomposition approach for the free and forced vibration analysis of plate assemblies

Free and forced vibration analysis of tri-directional functionally graded porous doubly-curved nanoshells integrated with magneto-electro-elastic layers

Development of industry-applicable two-phase flow identification and classification approach based on flow-induced vibration force signals

Low-quality fine-grained coal cannot be effectively separated in a conventional gas–solid fluidized bed. To enhance the density stratification and separation of low-quality fine-grained coal, this paper introduces a vibration force field to create a vibrating airflow composite force field. By investigating the force characteristics and sorting behavior of particles within this vibrating airflow composite force field, we reveal the mechanical properties of both high-density and low-density particles. An energy dissipation model for the vibrational energy among particles in the bed is established, clarifying how vibration acceleration varies between the front and rear sections of the bed. The experimental results indicate that acceleration at the feeding end is significantly greater than that at the discharging end. This higher acceleration at the feeding end facilitates the stratification and segregation of selected particles, while acceleration at the discharging end provides the necessary energy for the transport of gangue. The acceleration curve for low-density particles exhibits greater fluctuations compared to that for high-density particles; additionally, the forces acting on these particles along the y-axis direction promote density segregation. The forces tend to decrease gradually along the z-axis direction, which aids in particle migration and movement. The particle-sorting effectiveness within this vibrating airflow composite force field initially increases with rising vibration frequencies and gas velocities before subsequently decreasing. Under a frequency of 30 Hz and a gas velocity of 35 cm/s, the ash content and yield of the clean coal product from the bed are 7.1% and 52.6%, respectively, achieving the maximum degree of ash separation.

Abstract The study aims to develop a predictive model for crack propagation in a blade's plate. The finite element method is employed to simulate the blade's entire structure. ANSYS software is utilized to model the plate and determine its natural frequencies under cyclic loading. The results obtained through the finite element method are compared with data from the literature to confirm the validity of the proposed model. Both natural and forced vibrations of the blade's plate, including double-edge cracks, are analyzed. Various crack sizes and locations are modeled to investigate their impact on the blade's behavior. The proposed model effectively identifies the crack in the plate that forms earlier and achieves a high accuracy in predicting the crack's size and location under cyclic loading.