Vibration Of System Research Articles

A compliant helical structure to amplify inertia for nonlinear vibration absorption

The vibration absorption is a passive approach for vibration control by attaching a secondary vibration system to realize the energy transfer and dissipation. To generate a sufficient inertial force, vibration absorbers need to introduce large additional mass, and thus the engineering applications are limited. In this study, a novel compliant structure is proposed with the inertial amplified through a helical movement, and the structure is adopted for nonlinear vibration absorption. The dynamic equations of the absorber are established based on the Lagrange equation, characterizing the nonlinear characteristics arising from the large deformation of the structure and the nonlinear kinetic relationship between the translation and the rotation. Amplitude-frequency responses of the absorber under different excitations are solved using the harmonic balance method and the arc-length continuation method. A rotation-inertial dominant absorber (RIDA) and a translation-inertial dominant absorber (TIDA) are fabricated with the same helical structure while different mass distributions and experiments are performed to validate the nonlinear characteristics and vibration absorption effects. It is observed that both RIDA and TIDA demonstrate effective vibration absorption performances., RIDA introduces smaller additional mass than TIDA. The proposed helical structure absorbers exhibit combined nonlinearities of softening stiffness and displacement-dependent inertia and damping, demonstrating resonance shifting and jump phenomena. With an increasing excitation amplitude, the vibration absorption efficiency decreases and then increases.

Attenuation of Sommerfeld effect in a four DOF vibration system driven by a non-ideal induction motor

Attenuation of Sommerfeld effect in a four DOF vibration system driven by a non-ideal induction motor

Design and Experimental Research of a Non-Destructive Detection Device for High-Precision Cylindrical Roller Dynamic Unbalance

Due to their small size and light mass, small precision cylindrical rollers present challenges in dynamic unbalance detection, including difficulties in measurement and the risk of surface damage. This paper proposes a non-destructive detection device for assessing the dynamic unbalance of small precision cylindrical rollers. The device utilizes an air flotation support method combined with resonance amplification to indirectly measure the dynamic unbalance. A dynamic model of the air flotation tooling-cylindrical roller vibration system was developed to explore the relationship between the vibration parameters of the air flotation tooling and the dynamic unbalance of the cylindrical roller. Modal analysis and harmonic response analysis were performed, revealing that the amplitude of the vibration system at resonance could be detected using the sensor. Additionally, modal testing was conducted to determine the natural frequency of the system. A non-destructive detection platform was constructed for testing the dynamic unbalance of cylindrical rollers. Microscopic observation of the roller surface before and after testing confirmed that the device successfully performs non-destructive detection of dynamic unbalance.

Piezoelectric Ultrasonic Local Resonant Ultra-Precision Grinding for Hard-Brittle Materials.

Hard-brittle materials are widely used in the optics, electronics, and aviation industries, but their high hardness and brittleness make it challenging for traditional processing methods to achieve high efficiency and superior surface quality. This study aims to investigate the application of ultrasonic local resonant grinding to sapphire to improve the efficiency and meet the requirements for the optical window in the surface roughness of the material. The resonant frequency of a piezoelectric ultrasonic vibration system and the vibration amplitude of a grinding head's working face were simulated and tested, respectively. The results of ultrasonic grinding experiments showed that the local resonant system reduced the surface roughness parameter (Ra) of sapphire to 14 nm and improved its surface flatness to 44.2 nm, thus meeting the requirements for the ultra-precision grinding of sapphire. Compared with a conventional resonant system, the surface roughness of the sapphire ground with the local resonant system was reduced by 90.79%, its surface flatness was improved by 81.58%, and the material removal rate was increased by 31.35%. These experimental results showed that ultrasonic local resonant grinding has better effects than those of conventional ultrasonic grinding in improving surface quality and increasing the material removal rate.

Active Vibration Control and Parameter Optimization of Genetic Algorithm for Partially Damped Composites Beams.

The paper partially covered Active Constrained Layer Damping (ACLD) cantilever beams' dynamic modeling, active vibration control, and parameter optimization techniques as the main topic of this research. The dynamic model of the viscoelastic sandwich beam is created by merging the finite element approach with the Golla Hughes McTavish (GHM) model. The governing equation is constructed based on Hamilton's principle. After the joint reduction of physical space and state space, the model is modified to comply with the demands of active control. The control parameters are optimized based on the Kalman filter and genetic algorithm. The effect of various ACLD coverage architectures and excitation signals on the system's vibration is investigated. According to the research, the genetic algorithm's optimization iteration can quickly find the best solution while achieving accurate model tracking, increasing the effectiveness and precision of active control. The Kalman filter can effectively suppress the impact of vibration and noise exposure to random excitation on the system.

Research on a novel non-uniform and asymmetric ultrasonic vibration system

Abstract A new type of non-uniform and asymmetric ultrasonic vibration system is proposed and applied to the turning process. The research results show that the design theory of the non-uniform and non-symmetric ultrasonic vibration system is accurate and reliable.The theoretical design frequency and modal simulation frequency error of Ultrasonic Vibration Turning System (UVTS) is only 2.5%. The designed non-uniform and non-symmetric ultrasonic vibration system has excellent vibration performance and stability, and the established simulation model can predict surface microtexture accurately. The vibration mode output by the non-uniform and non-symmetric ultrasonic vibration system is longitudinal-bending vibration, and the actual vibration performance is excellent. Compared with conventional cutting, the addition of longitudinal-bending ultrasonic vibration under the same conditions can give the machined surface a microscopic textured structure, reduce surface roughness and water contact angle, and improve surface wettability.The minimum surface roughness obtained in the experiment is 1.005 μm.The orthogonal experiment results show that there is a correlation between the machining parameters, surface micro-structure parameters, surface wettability, and surface roughness.

Vibration suppression in SDOF systems coupled to a nonlinear energy sink under colored noise

This study analyzes the stochastic vibration suppression and optimization of the single-degree-of-freedom (SDOF) system equipped with the cubic stiffness nonlinear energy sink (NES) under colored noise excitation. Two theoretical methods are proposed: an integrated method (denoted as EL-ELM) that combines evolutionary Lyapunov theory with the equivalent linearization method, and the other is an empirical formula. Using EL-ELM, the coupled nonlinear system is simplified to an equivalent linear stochastic system, allowing for a theoretical analysis of the impact of NES structural parameters on suppression performance and the precise determination of optimal parameter configurations for the best suppression effects. Subsequently, based on the results from the EL-ELM and the response data, an empirical formula has been developed that clearly describes the comprehensive laws governing the optimal NES parameters as they vary with vibration system parameters and stochastic excitation. Through error analysis and comparison of the two methods, it is found that the empirical formula significantly outperforms EL-ELM in terms of accuracy and computational cost, but it is contingent on solid prior knowledge. This study explores the influence of NES structural parameters on the system’s dynamic response and energy, further validating the effectiveness of the proposed methods in identifying optimal structural parameters. The phenomenon of targeted energy transfer (TET) under different NES structural parameters is also explained. The methodologies introduced in this study have strengthened the theory of vibration suppression. Specifically, the empirical formula excels in accuracy and computational efficiency by effectively using prior knowledge. The EL-ELM method, owing to its theoretical insights, is vital for analyzing complex stochastic nonlinear models. Combining these approaches offers guidance for advancing vibration control in theoretical and practical domains.

Structural Damage Detection under Ambient Excitation Using Symbolic Three-Order Square Matrix Formed by Specific-Interval-Sampled Time-Domain Signals.

In the structural health monitoring of vibration systems, varying excitation always affects the accuracy of damage identification. The proposed symbolic three-order square matrix damage detection method with the matrix norm as a damage indicator can solve the difficult problem of damage identification under ambient excitation. The new sampling pattern extracts data from signals in the time domain at specific intervals based on the structural properties with the help of the autocorrelation coefficient. Then, the data extracted are converted into symbols and arranged into a three-order square matrix, and the Frobenius norm of the matrix is used for structural damage identification as a reliable damage indicator. In this process, the transmissibility function is employed to eliminate the effects of varying excitation. First, the method was verified by a cracked simply supported beam-a simulated Abaqus model. Then, a wooden truss bridge in the laboratory and an actual engineering scenario under ambient excitation together demonstrated the effectiveness and accuracy of the damage identification method and proved the proposed method to be robust to different types of damage under ambient excitation. Compared with other related methods, this method is more intuitive and efficient.

Investigations on piezo actuator-based non-resonant type workpiece vibratory system for vibration-assisted micro-milling

Investigations on piezo actuator-based non-resonant type workpiece vibratory system for vibration-assisted micro-milling

A distributed parameter model of the cavity-loaded piston transducer

Abstract Adding a cylindrical liquid cavity at the radiation surface of a piston transducer can introduce the liquid cavity resonance into the vibration system, thereby extending the operating bandwidth of the transducer. However, recent studies have shown that effective coupling of the liquid cavity resonance with the self-resonance of the piston transducer presents difficulties, resulting in significant fluctuations in the transmitting voltage response (TVR) within the operating frequency band. The physical mechanism behind this phenomenon remains unclear to date. In this paper, a distributed parameter model (DPM) for the cavity-loaded piston transducer is proposed. The admittance, amplitude and phase of the vibration velocity and TVR of the transducer are calculated using both DPM and finite element method (FEM). The results from DPM and FEM exhibit good agreement, indicating that the DPM can accurately describe the vibration characteristics of the transducer. Finally, two physical analogies of the transducer are proposed and explanations for the large fluctuations in TVR are given. This study reveals the modal coupling mechanism of the cavity-loaded piston transducer, and provides theoretical support for the analysis and designs of such transducers.

Experiment on the vortex-induced vibration of an S-shaped flexible riser coupled with an oscillating platform

This paper reports the experimental results of the vortex-induced vibration (VIV) of an S-shaped flexible riser hanged underneath a two-degree-of-freedom (2-DOF) oscillating cylindrical platform. A buoyancy module of approximately triple the riser diameter was mounted on the one-third of the riser length measured from its base to produce the S-shaped configuration. The VIV response of the flexible riser filled with two typical fluid media, including water and helium, was tested in the depth-averaged reduced velocity (U¯r) range of 9.32–26.41. The experimental results indicate that the change of internal fluid medium alters the spatial distribution of dominant frequency and excited modal order. The mode competition is enhanced when the internal fluid shifts from water to helium, and the critical U¯r for mode transition becomes higher. Based on the coincidence of dominant frequency, four types of coupling response are identified, and two characteristic lengths are quantified. The dominant role of the vibration system is determined by the occurrence time percentages of coupling lengths and dominant frequencies. The vibration of water-filled riser is dominated by itself, and the influence of buoyancy module is negligible. In contrast, the in-plane response of helium-filled riser is significantly affected by the buoyancy module, and the influence is amplified with the increase in U¯r.

Numerical Simulation Study on Vibration Characteristics and Influencing Factors of Coal Containing Geological Structure

Accurately determining the natural frequency of coal-containing geological structures is crucial for preventing mine dynamic disasters and utilizing vibration waves to break coal and enhance its permeability. Based on the modal theory of rock, vibration models of coal-containing geological structures, including layering and fractures are established. By analysis, the undamped vibration equation and its characteristic equation for both the layered coal system and the fractured coal system are derived. Subsequently, the Lanczos method is employed to solve the system’s vibration modes using ABAQUS. The effects of the layering position, layering thickness, layering physical properties, crack width, and crack length on the natural frequency and vibration response of coal-containing geological structures are investigated. The results indicate that when a single influencing factor is altered, the displacement response distribution of the coal body vibration system with geological structures remains essentially the same, and these single influencing factors have a minimal impact on the vibration displacement of the coal-containing geological structure. The natural frequency of the system decreases exponentially as the distance between the layering and the geometric center of the coal system with geological structures increases. The presence of layering in the coal system with geological structures significantly reduces the system’s natural frequency. The natural frequency of the coal system with geological structures increases in a power function manner as the layering elastic modulus increases. Conversely, the natural frequency decreases with an increase in crack length. When the change ranges of crack width and bedding thickness are the same, the natural frequency of the fractured coal body system exhibits more significant changes. The natural frequency of the coal system with geological structures initially decreases and then increases as bedding thickness and crack width increase. The trend in the natural frequency changes and the position of the extreme point are related to the ratio of the elastic modulus and density of the geological structure.

Order of magnitude increase in power from flow-induced vibrations

Natural hydro environments such as rivers and ocean currents provide abundant and essentially free sources of kinetic energy. Although significant research has been devoted to harnessing this power through traditional turbine systems, there are also studies on the novel use of flow-induced vibration of a bluff body. The large oscillations of an elliptical cylinder resulting from the newly-discovered hyper branch have raised interesting questions about its potential as a source of effective renewable energy. This study investigates the power extraction characteristics of the hyper branch over a range of flow velocities. A factor-of-ten increase in the maximum time-mean power coefficient relative to an established flow-induced vibration system — the vortex induced vibration for aquatic clean energy converter is demonstrated. This suggests the possibility of a new and effective strategy to utilise flow-induced vibrations for energy generation and could help drive the commercial implementation and uptake of oscillating energy converters.

Research on rapid stabilization of aero-engine casings subjected to shock loads using nonlinear energy sink

In this study, we study the application of nonlinear energy sinks (NES) for targeted vibration energy transfer and absorption in aero-engine casings subjected to shock loads. A simplified single-degree-of-freedom model with an attached NES is characterized to understand the influence of control parameters such as damping and nonlinear stiffness on the NES. Using the complexification-averaging (CX-A) technique, we analyze the main dynamic characteristics of the vibration system, revealing nonlinear normal modes (NNM) and the energy localization phenomenon that enables targeted energy transfer. Then we establish a thin-walled casing model with an NES and calculate its vibration energy transfer under shock load. The results of this study are as follows: (1) NNMs are related to initial energy, with energy localization leading to targeted vibration energy transfer and dissipation; (2) NES operates optimally within a specific energy domain, exceeding this domain reduces its effectiveness, which is primarily influenced by the NES’s nonlinear stiffness; (3) Optimizing the NES’s nonlinear stiffness on the thin-walled casing achieves targeted shock energy transfer and dissipation, significantly reducing the casing’s vibration amplitude (from 0.008 m to 0.003 m, a 62.5% reduction) and stabilization time (from 0.007s to 0.002s, a 71% reduction). The study’s results are instructive for achieving rapid stabilization of aero-engine casings under shock excitation, providing insights into the mechanism of NES and the impact of damping and nonlinear stiffness on its performance. This research guides the optimized design of NES for thin-walled casings to effectively dissipate shock-induced vibrations.

Analytical Solutions Based on Hamiltonian System for the Free Vibration of Polyline Thin Plates

It is challenging to establish analytical solutions for conventional inverse and semi-inverse approaches because of the intricacy of standard mathematical calculations. In this study, the symplectic superposition approach is used to provide the analytical solution for the free vibration of a thin plate with a polyline shape. The polyline plate is separated into four sub-plates based on the superposition principle, and then the problem is solved by using the symplectic eigen-expansion method. Multiple sets of constants dependent on boundary conditions can be found by applying a specific mechanical quantity to the edge of each sub-plate. The four sub-plate solutions can be combined to provide the final analytical solution. By contrasting the numerical results obtained under various boundary restrictions, the correctness and effectiveness of the method are confirmed. The frequency values decrease with increasing a2/a1 due to the decrease of structure’s stiffness. The method proposed in this work can be extended to solve the vibration of anisotropic thin plate with other boundary conditions and irregular plates.

Counter-rotating synchronization theory and experiment of tri-rotor actuated with dual-frequency considering adaptive global sliding mode control strategy

In petroleum drilling engineering, self-synchronous vibration screen with single-frequency actuation is difficult to implement the scheduled synchronous behavior caused by its invariance and instability of dynamic characteristics, which usually leads to reduction of the production efficiency. Hence, to solve the problem mentioned above, a dual-frequency counter-rotating synchronization control method among three exciters is presented by combining adjacent cross-coupling control (ACCC) structure with global sliding mode control (GSMC) theory. Firstly, motion differential equation of the vibration system in each direction is derived according to mathematical model of the tri-rotor vibration machine. Secondly, considering exponential reaching law and adaptive control algorithm, the adjacent cross-coupling controller and the vector controller of each induction motor are investigated to achieve the stable zero phase difference synchronization between double-frequency rotors. Subsequently, Runge-Kutta method is introduced to establish the electromechanical coupling control model and prove validity of the control theory. Meanwhile, it is also discussed that the rotors cannot obtain an ideal self-synchronization state since velocity of high-frequency motor is not strictly equal to twice that of low-frequency motor. Finally, based on the experimental test scheme, an experimental prototype related to controlled multi-rotor synchronization vibration system is designed independently, which further verifies the validity of theory and computer simulation. Research shows that the desirable synchronous state of the vibration system can be accurately controlled via the designed control strategy, and the control system can implement diversity of the dynamical characteristics, due to the existence of strong robustness.

Numerical investigation on the suppression of vortex-induced vibration system by assembling different rotors based on quasi-active control method

Combining the innovative concept of quasi-active control method, a numerical simulation is conducted to investigate the vortex-induced vibration (VIV) responses. The objects of this study include a main cylinder (MC) and a cylindrical system outfitted with a pair of rotors of different types (with Banki rotors, Darrieus rotors, and Savonius rotors, denoted as WBR, WDR, and WSR), and the VIV responses are analyzed within the Reynolds number range of 0.8 × 103≤Re ≤ 5.6 × 103. The findings indicate that all three kinds of rotors show excellent vibration suppression effect in downstream and cross-flow directions by adjusting the VIV response (amplitude, frequency, hydrodynamic coefficient) and vortex pattern (vortex mode, wake shape). The maximum amplitude suppression rate can reach 99% for the Banki and Savonius cases at high reduced velocity. Within the whole velocity range, the maximum amplitudes of WBR, WDR, and WSR cases in the downstream and cross-flow directions were 0.32 and 0.45 times, 0.73 and 0.65 times, and 0.28 and 0.33 times, respectively, compared to the maximum amplitude of MC. The time-averaged drag coefficient of the controlled cylinder in the WBR case was minimized to about 0.015. The Banki rotor and Savonius rotor significantly reduced the vibration frequency of the VIV system compared to the Darrieus rotor. Especially, the Banki rotor could keep the VIV system vibration frequency within a narrow range at different reduced velocity. Moreover, the vorticity contour of the VIV system with assembled rotors was significantly improved, with a narrower flow wake width and more regular vortex shedding at high reduced velocity. Considering both amplitude suppression and drag coefficient, Banki rotors were recommended.

Stationary Responses of Seven Classes of Fractional Vibrations Driven by Sinusoidal Force

This paper gives the contributions in three folds. First, we propose fractional phasor motion equations of seven classes of fractional vibrators. Second, we put forward fractional phasor responses to seven classes of fractional vibrators. Third, we bring forward the analytical expressions of stationary responses in time to seven classes of fractional vibration systems driven by sinusoidal force using elementary functions. The present results show that there are obvious effects of fractional orders on the sinusoidal stationary responses to fractional vibrations.

A novel method of vehicle height control utilizing semi-active actuator

Inspired by the physical phenomenon that the balance position of the vehicle body changes due to a suspension system with asymmetric damping, this paper presents a novel method to control the vehicle height utilizing semi-active actuators. The proposed vehicle height control method uses the asymmetric damping of the semi-active actuator to control the raising and lowering of the vehicle body, which essentially harnesses the energy from the vehicle’s driving vibrations and has the characteristics of low cost, energy saving and fast response. Aiming at the strong nonlinearity and discontinuity of the piecewise linear nonlinear system of the vehicle body vibration, the homotopy analysis method (HAM) is used to solve the high-order analytical solution, the non-smooth terms are processed through Fourier series expansion, and the iteration method is combined to treat the iteration result as the initial guess solution for the next iteration, improving the convergence accuracy of the series solution and expands the application scope of the HAM. The feasibility of the presented method is investigated from an analytical point of view and the influences of some critical parameters on the responses of the system are analyzed. Finally, the magnetorheological damper (MRD) produced by LORD company is utilized as the actuator, and the vehicle height control experiments system is established by using NI-Labview software and NI-PXI hardware platform, The experiments are performed to verify the feasibility of the proposed vehicle height control method and the system response laws. The proposed method realizes the functions of active actuators using semi-active actuators, and tries a new method and approach for vehicle height control under specific working conditions, such as short-term obstacle surmounting, high-speed steering, emergency avoidance, and rollover prevention.

Research on semi-active vibration reduction of offshore wind turbine structure combined eddy current theory with tuned mass dampers

At present, the offshore wind power gradually shows a development trend towards the profound ocean with characteristic of larger capacity, higher tower and longer blades. Therefore, the offshore wind turbine (OWT) is more vulnerable to extreme loads and may lead to the negative influence of structural vibration safety. In this research, a new semi-active eddy current tuned mass damper (SEC-TMD) was proposed for the vibration control of OWT structures and its vibration reduction effect under multiple kinds of dynamic loads was also discussed. Firstly, taking one actual 3.0 MW OWT supported by bucket foundation as object, the SEC-TMD was designed based on the linear quadratic optimal control (LQR) algorithm and bounded Hrovat optimal control algorithm in order to obtain the optimal control force of structural vibration systems. The relationship between damping coefficient and magnetic conductivity spacing was further fitted to achieve variable damping control of SEC-TMD. Secondly, the theoretical model of 3.0 MW OWT structure installed with SEC-TMD was established and the effectiveness of the established theoretical model was verified through the comparison on modal analysis between the theoretical calculations and measured data identification. Finally, the vibration reduction effect of SEC-TMD on the measured OWT structure under wind-wave, seismic and vibration amplification conditions was analyzed and compared with the results calculated from the other passive dampers including EC-TMD and TLCD. It is shown that the maximum reduction percentage of peak value for vibration displacement and acceleration on the tower top can respectively reach 31.93 %, 44.11 %, 30.20 % and 54.57 %, 33.94 %, 31.75 % under three above conditions. Comparing with EC-TMD and TLCD, the better vibration reduction effect indicates that the proposed SEC-TMD has good engineering application value for the vibration suppression of OWT.