Inherent Vibration Research Articles

Zr-MOF-based substrate with inherent internal standards facilitates reliable SERS analysis of sulfonamide antibiotics

A multifunctional structure comprising gold nanoparticles immobilized within a zirconium-based metal-organic framework (AuNPs/Zr-MOF) was systematically designed. With the capabilities of analyte enrichment, Raman signal enhancement and internal standard calibration, the as-prepared AuNPs/Zr-MOF substrates demonstrate the outstanding SERS sensing performance toward the representative sulfonamide antibiotics (SAs), sulfadiazine, sulfamerazine, sulfamethazine and sulfaquinoxaline. For the first time, these four SAs are detected by SERS in real honey samples at levels of 2.8 ∼ 5.2 ng·g−1 within 10 min. The extensive π-bond conjugated system of Zr-MOF significantly enhances the concentration of SAs through π-π interactions. The entrapped SAs are adsorbed perpendicularly onto the surface of Au via coordinated interactions between Au and two oxygen atoms, or between Au and the terminal amino group. To achieve reliable quantitative analysis, the inherent vibration of the Zr-MOF structure was used as an internal standard label. Combined with a simple clean-up protocol, the established SERE sensing method is superior to conventional methods in terms of time, while achieving the impressive sensitivity. This study presents a robust SERS-based approach for the rapid detection and monitoring of multiple analytes.

Optimal design of vibration resistance of fiber-reinforced composite sandwich plates embedded in a viscoelastic square honeycomb core

This work focuses on investigating the optimal design of composite sandwich plates (FCSPs) with a viscoelastic square honeycomb core (VSHC). Firstly, using the cross-fill theory, the complex modulus technique, the first-order shear deformation theory, the minimum strain energy principle, and the Newmark-β method, a theoretical model of the VSHC-FCSPs under half-sine pulse excitation is formulated to calculate the inherent frequencies, the peak and vibration decay time of the transient response in time domain. The peak and vibration decay time are taken as the indexes of the anti-vibration performance. Considering an index of structural stiffness performance, the average value of the inherent frequencies is adopted to calculate the overall stiffness. After a set of literature validations and optimization validations, the multi-objective genetic algorithm is employed to study the optimization issue of VSHC-FCSPs. The optimization objectives are to minimize the three design variables of the transient response peak, vibration decay time, and reciprocal of overall stiffness. Then, the fiber laying angle of each layer, the core thickness ratio and the modulus ratio are assumed as optimization variables. Finally, the results with good vibration resistance and structural stiffness in the Pareto front are chosen as references, and these corresponding variations of the design variables and optimization objectives are obtained. The optimization results have revealed that the optimization variables corresponding to the intermediate points should be selected as references to improve the anti-vibration capacity and ensure the structural stiffness performance.

Vibration disturbance compensation in in situ confocal microscopy.

In situ microscopic measurement, conducted within the natural environment of a material or device, offers precise observations directly at the sample location, mitigating potential damage or deformation during transport. However, the inherent vibration of microscopic measurement equipment can introduce blurring and distortion to images, compromising measurement accuracy. This study proposes employing an acceleration sensor to detect microprobe vibrations and subsequently calculates three-dimensional coordinate displacements to compensate for measurement discrepancies. This approach can diminish the adverse effects of vibration on measurement outcomes within the order of hundreds of nanometers. Experimental results demonstrated the efficacy of this method in mitigating vibration artifact stripes or irregularities with a displacement amplitude I = sinc2[a(z - b)] ranging from ∼0.2 to 5.2 μm and a frequency spanning ∼7.9-18.8 Hz. Moreover, the lateral resolution of the probe attained 212 nm. Notably, the measurement error associated with the standard step height was decreased from 2.32 to 0.03 μm.

Modelling of electromechanical coupling dynamics for high-speed EHT system used in HEV and characteristics analysis

As the development of hybrid electric vehicle (HEV) to high-speed, heavy-load, the electromechanical coupling vibration becomes the bottleneck in high-speed electromechanical hybrid transmission (EHT) system. To explore the dynamics characteristics and optimization direction for high-speed EHT system, an electromechanical coupling dynamics model under multi-source excitations is established with lumped-distributed parameter method and verified with experiment data. The dynamics model shows higher accuracy in both time and frequency domain analysis. On this basis, firstly, the comparison between lumped-shaft and distributed-shaft model is studied under time and frequency domain. Comparing with the lumped-shaft model, the distributed-shaft model shows higher accuracy, and can better reflect the coupling vibration of multi-stage planetary gears (PGs). Secondly, the inherent vibration model is derived, and the effect of electromechanical coupling and high-speed working conditions on inherent vibration characteristics are studied. Thirdly, a new method called ‘machine-electricity-magnet coupling interface’ is proposed to reveal the coupling vibration phenomenon. In addition, the signal of stator current and electromagnetic torque includes the frequency of PGs, which is a basis on the fault diagnosis and state monitor of EHT system. Last but not the least, the vibration acceleration of EHT system is analysed under variable speed and load working conditions. Rotation speed and gear meshing force is found as the main influencing factor of series EHT system, and the specific optimization direction is also given.

A coarse and fine-grained deep multi view subspace clustering method for unsupervised fault diagnosis of rolling bearings

Abstract To address the issue of insufficient characterization of fault features in inherent vibration data that affects the performance of unsupervised learning-based fault diagnosis, a coarse and fine-grained deep multi view subspace clustering method (CFG-DMVSC) for unsupervised fault diagnosis of rolling bearings is proposed. The proposed method designs a convolutional autoencoder network based on the Gramian angular field transformation for multi-signal analysis domains. A multi-view coarse-grained self-expressive method based on information entropy is designed to handle differences in information across different views. Furthermore, a fine-grained common and independent information separation loss function based on mutual information is proposed to ensure compactness among multiple views. Both the Case Western Reserve University rolling bearing dataset and privately built bearing fault test bench data demonstrate that, compared to existing methods, the proposed method can perform coarse and fine-grained division in multi-view subspaces, achieving better clustering diagnosis performance on the extracted common information among views.

Deep Fusion of Intrinsic Vibration Information and Grassmann Manifold-based Similarity for Fault Identification of Reciprocating Compressor

This paper introduces a new method based on deep belief networks (DBN) to integrate intrinsic vibration information and assess the similarity of subspaces established on the Grassmann manifold for intelligent fault diagnosis of a reciprocating compressor (RC). Initially, raw vibration signals undergo empirical mode decomposition (EMD) to break them down into multiple intrinsic mode functions (IMFs). This operation can reveal inherent vibration patterns of fault and other components hidden in the original signals. Subsequently, features are refined from all the IMFs and concatenated into a high-dimensional representative vector, offering localized and comprehensive insights into RC operation. Through DBN, the fault-sensitive information are further refined from the features to enhance their performance in fault identification. Finally, similarities among subspaces on the Grassmann manifold are computed to match fault types. The efficacy of the method is validated using field data. Comparative analysis with traditional approaches for feature dimension reduction, feature extraction, and Euclidean distance-based fault identification underscores the effectiveness and superiority of the proposed method in RC fault diagnosis. Conflict of Interest Statement The authors declare no conflicts of interest.

EXPERIMENTAL INVESTIGATION OF THE VIBRATION-REDUCTION CHARACTERISTICS OF THE SHAFT COATING FOR A TURBOCHARGER

A turbocharger is a system that is fitted to automotive engines to increase performance and efficiency by taking air at atmospheric pressure, compressing it to a higher pressure and passing the compressed air into the engine via the inlet valves. A turbocharger consists of a turbine and a compressor impeller interconnected with a shaft supported in most cases by journal bearings. The shaft is one of most crucial components of a turbocharger system and it operates at high speed. The shaft vibrations are an inherent phenomenon and they are travelling to the surrounding structure, effecting the stability and reliability of the turbocharger system. The selection of the appropriate shaft-material property is a critical parameter among the parameters that affect the vibration of the system. This study focuses on exploring whether it is possible to reduce the shaft vibration using different types of coating materials, including aluminum chromium nitride (AlCrN), titanium nitride (TiN) and aluminum titanium nitride (AlTiN), each having thicknesses of (2, 4, and 6) µm, for a shaft made of AISI 4140 alloy steel. The inherent natural vibration properties, such as the resonant frequencies, damping, and mode shapes of the turbocharger shaft with and without coating, were obtained by conducting an experimental modal analysis through measurements of the frequency-response function, which is about curve fitting the data using a predefined mathematical model of the turbocharger shaft. The results were validated numerically with the finite element method. From overall results, it was observed that the AlCrN, TiN, and AlTiN coating thicknesses have a small effect on the resonant frequencies, but a good damping effect. The resonant response of the turbocharger shaft at resonant frequencies was suppressed remarkably by the AlCrN and AlTiN coatings, especially those having a thickness of 6 and 4 µm.

Vibration Response of Metal Plate and Shell Structure under Multi-Source Excitation with Welding and Bolt Connection

There are many excitation sources and complex vibration environments in combine harvesters. The coupling and superposition of different vibration signals on the plate and shell seriously affect the working parts of the body. This also reduces the reliability of the whole machine. At present, domestic and foreign research on existing harvesters mainly focuses on harvesting performance, with less research on vibration characteristics. Therefore, in this paper, the vibration response of the metal plate–shell under the two connection modes of bolt connection and welding is studied, in order to optimize the design and structure of the plate–shell structure of the combine harvester and improve the overall performance. First, the welded and bolted plates are numerically modeled using Hypermesh pre-processing functions. Then, the boundary conditions are simulated by continuous variable stiffness elastic constraint experiments. Finally, the intrinsic vibration dynamic model of the four-sided simply supported plate and four-sided solidly supported plate is established using the modal superposition method. By analyzing the modal frequencies and vibration patterns, the following results are obtained. The connection method between the plate and the frame has a significant impact on the inherent vibration characteristics of the plate. The bolt connection will make the plate’s intrinsic vibration frequency higher than that of the welding method, but the effect on the plate’s intrinsic vibration pattern is more minor. At the same time, in order to verify the accuracy of the model, the actual modal vibration patterns and frequencies of the same proportion of plates in the modal test are compared with the results of modal vibration patterns and frequencies obtained by Ansys. The errors of the two dynamic model analytical methods are within 1% and 3%, respectively. This result verifies the accuracy of the dynamic model of the metal plate and shell structure under different connection methods.

An enhanced quasi-3D HSDT for free vibration analysis of porous FG-CNT beams on a new concept of orthotropic VE-foundations

The original primary objective of this study is to conduct a comprehensive investigation into the free vibration behavior of beams with porosity, reinforced by carbon nanotubes (CNTs). These beams are supported by an arbitrary orthotropic variable elastic foundation (AOVEF). The focus lies on understanding how the presence of porosity and CNT reinforcement, coupled with the complex support provided by the AOVEF, influences the vibration characteristics of the beams. In addition, we intend to examine the impact of a number of micromechanical models on the vibration properties of these beams. Four carbon nanotube variables are introduced to symbolize several CNT variations. CNTs’ mechanical properties are examined through a variety of micromechanical models. Shear deformation effects are considered into account in the framework of higher-order shear deformation (HSDT) beam theory. The equations of motion are constructed using Hamilton’s concept and the equation system for the FG-CNT beam with supported ends is solved via the Navier methodology. A new approach in elastic foundation modeling is the Arbitrarily Orthotropic Variable Elastic (AOP-VE) foundation. It builds on the Winkler layer concept but introduces the idea of a variable response along the length of the beam foundation. Unlike the Winkler-Pasternak model, AOP-VE allows for control over the directional properties of the Pasternak foundation. The study looks into multiple aspects, involving various distribution kinds of CNTs, the impact of Winkler and Pasternak factors, mode values, side-to-length ratio, porosity, and angle variation. The results indicate that these parameters have a major effect on the inherent vibration features of FG-CNT beams. The study results in various novel findings that improve the understanding of the subject topic and set a standard for future studies.

Experimental research on vibration reduction characteristics of adhesively bonded beam structures with acoustic black hole geometry

Beam structures are widely used in industrial applications such as automobiles, aircraft, naval architecture, trains, and buildings. The vibration characteristics of beams are inherent phenomenon and directly affect usage comfort and service life, but more dangerously may damage the structure due to excessive vibrations that are transmitted through the surrounding structure of the system. Vibration reduction of beam structures is a continuous challenge for industrial applications. It is important to reduce vibrations of the beam structures for stability. In this study, experimental research on vibration reduction characteristics of adhesively bonded beam structures with Acoustic Black Hole technique is presented. The Acoustic Black Hole, which is a geometry, tapered with a power-law profile enables vibration reduction by decreasing the velocity and the wavelength of vibration. The inherent natural vibration properties called modal parameters such as the natural frequencies, damping, and mode shapes of the beam structure with and without damping layer using power-law profile having various the Acoustic Black Hole length and exponent values were investigated and evaluated with experimental modal analysis. For validation, natural frequencies are determined numerically by the finite element method, and then compared with results obtained by the experimental modal analysis. The overall results indicated that the Acoustic Black Hole has ability to significantly suppress the vibration level and showed the capability of enhancing the damping efficiency when using the damping layer attached to the Acoustic Black Hole length of the beam structure.

Natural Vibration Analysis of a Simple Vibration Absorber

The slender rod + mass block system is a typical elastic vibration absorber structure, with a simple structural form and strong design ability. It has wide application in engineering. This paper focuses on the inherent vibration characteristics of elastic structures and discusses the effects of gravity and typical geometric parameters on the modal frequency of the absorber structure. The calculation results show that, under the action of gravity, the overall strain rate is very low, and the impact of gravity on the structure's vibration characteristics can be ignored. With the increase of the length of mass block, length of slender rod, and the diameter of the mass block or with the decrease of diameter of slender rod, modal frequency of the elastic structure gradually decreases. The research conclusions can provide reference for the optimization design of simple elastic structures in engineering projects.

Terahertz electric field induced melting and transport of monolayer water confined in double-walled carbon nanotubes.

Understanding the structures and dynamics of confined water in nanochannels holds great promise for various applications, ranging from membrane separation to blue energy collection. A setting of particular interest is the confined monolayer water within double-walled carbon nanotubes (DWCNTs), which demonstrates rich ice morphologies; however, the dynamics of this peculiar system are still unexplored. In this work, a series of molecular dynamics (MD) simulations reveal that the two-dimensional ice in DWCNTs can be effectively melted by terahertz electric fields but not by static electric fields, exhibiting an interesting ice to vapor-like transition along with extraordinary dynamical behaviors. Specifically, under appropriate field frequency, the water flow presents a sharp increase with the increase in field strength, indicating an excellent gating behavior. These remarkable findings are attributed to the resonance effect between the terahertz electric field and inherent vibration of water hydrogen bonds, causing the water molecules to change from the frozen to super permeation states. The amount of confined water exhibits a sudden reduction, confirming the breakdown of the hydrogen bond network. The distributions of density profiles, hydrogen bond number and dipole orientation demonstrate more details of the water structural change. Furthermore, under a certain field strength, the water flow shows a peculiar maximum behavior with the increase in field frequency, implying frequency optimization for water transport. These findings not only enhance our understanding of the phase transition behavior of water molecules confined within DWCNTs under the influence of a terahertz electric field but also provide a promising avenue for designing innovative nanofluidic devices.

Study on electromechanical coupling inherent vibration characteristics and parameter influencing law of EMT system used in HEV

As high-speed, heavy-load, and high-power density are realized in hybrid electric vehicle (HEV), the electromechanical coupling inherent vibration of electromechanical composite transmission (EMT) system becomes the bottleneck in this study area. To reduce vibration, the analysis of inherent vibration characteristics of EMT system and parameter influencing law of mechanical-electro-magnetic parameter is key. Here, an electromechanical coupling dynamics model is established considering multi-source excitations, and the inherent vibration model is obtained. Based on this inherent vibration model, firstly, the inherent vibration frequency and mode with and without electromagnetic effect of EMT system are studied and summarized. Secondly, the resonance speed of EMT system is identified based on Campbell diagram and modal energy method. Thirdly, the inherent frequency trajectory and variation law affected by PMSM parameters (inner power factor angle (IPFA), armature current, stator-rotor eccentricity) and the mode mutations phenomenon of inherent frequency trajectory caused by PG parameter (connecting, gear meshing, and bearing support stiffness) are studied. This study results provide a reference for the modeling and analysis of inherent vibration characteristics, as well as the design and optimization of mechanical-electro-magnetic parameter of EMT system.

Vibration of flexible robots: Dynamics and novel synthesis of unbounded trajectories

Flexible Robotic Systems, by and large, are prone to inherent vibration that recreates itself in several modal frequencies. This in-situ vibration in flexible robots or in any such complaint robotic unit becomes tricky so far as the control system architecture is concerned. Thus, customization of the design and firmware of higher-order flexible robots is highly challenging due to its inherent parameters related to real-time vibration. Vibration in flexible robots has been investigated hitherto from the standpoint of frequency & amplitude tuple, sidetracking the important paradigm of looping of the trajectories. This work has added a technological niche in bringing out the intrinsic dynamics of this vibration from a mathematical perspective of trajectory formation so as to understand the mechanics of spiraling loops while a flexible/compliant robotic system is vibrating under natural conditions. The analytical modeling of the said in-situ vibration has been experimented with through an indigenous single-link flexible robot, fitted with a miniature gripper.

Modular design and simulation analysis of truss robot based on spatial bars structure

For industrial applications, truss robots can perform mutipleoperations, such as transporting objects and handling tools independently, but face the challenges of inconvenient disassembly and non-recyclability. Therefore, a truss robot load-bearing module based on a spatial bar structure is designed, which consists of truss bars and connectors. Ansys Workbench is used for the static analysis of the truss robot beam. The results show that the maximum stress of the truss robot beam is 32.46 MPa and the maximum deformation is 1.1 mm under the load of 12,000 N. The maximum stress of the beam is significantly small than the yield limit of the material and the deformation is small, which meets the requirements of structural strength and load stability of the truss robot. Based on the mode analysis of the truss robot, the inherent vibration and frequency of the truss robot are extracted, providing a reference basis for the stability control of the truss robot. The modular truss robot has mutiple advantages, including the large span, high load capacity and assembly flexibility.

Noise Prediction Study of Traction Arc Tooth Cylindrical Gears for New Generation High-Speed Electric Multiple Units

As the speed of the new generation of high-speed electric multiple units (EMU) increases, the requirements for vibration and noise reduction in traction gear trains are becoming higher and higher. Although most researchers have focused on the vibration mechanics analysis of gears, the actual noise has the most direct impact on passenger experience and safety. To address this problem, a new type of curved cylindrical gear is proposed to analyze the dynamic characteristics of the gear pair and predict its radiated noise based on the acoustic-vibration coupling theory using the finite element-boundary element method. Parametric modeling of the gear pair using CREO and assembly motion analysis were performed. ANSYS was used to analyze the stress distribution, inherent frequency, and inherent vibration pattern of the gear pair, and harmonic response analysis was performed using the modal superposition method to solve the displacement frequency response curve and vibration characteristics. ACTRAN was used to construct the free-field model, create acoustic excitation based on the acoustic-vibration coupling equation, set the field points, and predict radiated noise. The research results show that the noise is mainly concentrated in the tooth meshing area, and the root mean square RMS range of its sound pressure level value is 91–100 dB. Its dynamic characteristics and noise values are in line with the traction requirements of high-speed EMU, providing a new idea for improving the noise prediction of traction gears for new generation high-speed EMU, which in turn strongly support the noise control of high-speed EMU stock and thus improve the passenger experience and driving environment.

Dynamic Effect of Fluid–Structure Interaction and Modal Analysis of Crude–Pipeline Interaction System Considering the Fluctuating Pressure of Medium

This work explored the fluid–structure interaction (FSI) effect of crude oil and pipeline and the vibration characteristics of the pipe–crude oil structural system. A finite element computational analysis theory and corresponding simulation method were proposed for crude oil pipelines considering the FSI effect. Meanwhile, the spring model of the FSI interface between crude oil and pipeline was proposed. The experimental simulation and neural network were adopted to obtain the flow-excited pulsation pressure (FEPP), and the kinetic equations of the pipe–crude oil FSI were analyzed. The finite element computation (FEC) model for pipe–crude oil bi-directional FSI dynamics was established, which was composed of five support span lengths and four pipe liquid levels and can provide five different crude oil fluid velocities. One hundred orthogonal simulation test conditions were designed. In addition, the displacement response and acceleration response under FSI of the pipe wall were calculated, and the first six orders of inherent frequencies and main vibration patterns of the FEC model were analyzed. The results revealed that the dynamic effect of FSI between the crude oil transport medium and pipeline was complex and was influenced by the length of the pipeline crossing section, medium flow velocity, difference of liquid surface height, and displacement response. The acceleration response possessed prominent vibration decay characteristics, and the response peak in the same condition was about 8.2 times larger than that of the steady-flow state response. Therefore, the effect changed the inherent frequency and vibration pattern of the pipeline, to which the engineering design should pay sufficient attention.

Investigation on gas-coupled vibration damping modules in free-piston Stirling generator

The free-piston Stirling generator (FPSG) is efficient and environmentally friendly. However, the inherent vibration limits FPSG’s application and shortens its life. This paper presents two novel vibration damping modules, which are placed inside the FPSG with the vibration damping piston (VDP) driven by the pressure fluctuation in the back space. One is a passive vibration damping module (PVDM), and the other is an active vibration damping module (AVDM). By adjusting the movement of VDP, the sum of the momentums of the moving parts can be zero, thus eliminating the shell’s vibration. For PVDM, the movement of VDP is adjusted by changing the opening of a needle valve. For AVDM, it is adjusted by changing the electric power of the linear alternator. The performances of these two modules are investigated based on SAGE software. Both PVDM and AVDM enable FPSG’s shell to work without vibration under the design condition with minimal reduction of thermal-acoustic-electric conversion efficiency. When the damping coefficient of vibration damping piston, external load, and heating block temperature deviate from the design value, PVDM can reduce the vibration to a certain extent. AVDM can eliminate the vibration completely under any operating conditions. For this module, the acoustic power in the back space and the input electric power are its two main energy sources, and the input electric power is relatively small. The efficiency of the whole system is reduced by no more than 1% to eliminate the vibration. Adopting these two vibration damping modules can facilitate the application of the free-piston Stirling generator.

Research on a Variable Pressure Driving Method for Soft Robots Based on the Electromagnetic Effect.

This study proposes a novel variable air pressure supply structure based on the electromagnetic effect. This structure can be implemented in various soft robots driven by air pressure, including pneumatic artificial muscles, pneumatic soft grippers, and other soft robots. The structure's main body comprises a hollow circular tube, a magnetic piston arranged in the tube, and an electromagnetic solenoid nested outside the tube. The electromagnetic solenoid is designed with special winding and power supply access modes, generating either an attractive force or a repulsive force on the magnetic piston. This solenoid conforms with the magnetic piston expectation in the tube by changing the polarity direction. The interior of the whole structure is a closed space. The gas is conveyed to the soft robot by the gas guide hoses at the two ends of the structure, and the expansion energy of the compressed gas is fully utilized. Then, the gas supply pressure is controlled to drive the robot. The mathematical model of the structure is established based on the analysis of the electromagnetic force and gas pressure on the piston. The simulation results show that the structure's inherent vibration characteristics under various parameters align with expectations. The real-time automatic optimization of the controller parameters is realized by optimizing the incremental proportional-integral-derivative (PID) controller based on a neural network. The simulation results show that the structure can meet the application requirements. The experimental results show that the proposed gas supply structure can provide a continuous pressure supply curve with any frequency in a specific amplitude range and has an excellent tracking effect on the sinusoidal-like pressure curve.

The dynamic investigation of intrinsic vibration characteristics of a stranding machine by the finite element method

In response to the design problems of violent vibration and noise when a stranding machine is running at high speed, this project completed a motion simulation and vibration analysis based on the prototype FB-650C-2 bow-type stranding machine produced by Fuchuan Mechanical and Electrical Technology Co. The modal analysis was carried out in ANSYS to obtain the first eight orders of inherent frequencies and vibration patterns, combined with excitation force analysis to verify whether the rotating parts could avoid the resonant frequency when operating. Harmonic response analysis was carried out based on the modal state to calculate the steady-state forced vibration of the structure, and the variation curve of response value (usual deformation) with frequency and the cloud diagrams of stress distribution of each component at the rotation frequency were obtained. Suggestions for improving vibration and reducing noise were made based on the experimental and analytical results.