Vibration Transmission Path Research Articles

Electrical Contact Resistance of Connector Response to Mechanical Vibration Environment

Contact resistance is an important barometer for service life and reliability of electrical connectors, which are widely used in electrical and electronic system. Long and harsh mechanical vibration stress would result in the function failure of electrical contact. In this article, the electrical contact resistance (ECR) of a typical connector is accurately recorded in real time with the four-wire method under mechanical vibration environment. Furthermore, the relationship between the ECR and vibration stress (including frequency and acceleration) is investigated explicitly. To better understand the physical mechanism of the ECR fluctuation and degradation, the vibration transmission path and associated dynamic response model of the connector are built. Finally, the main influencing factors on the ECR under mechanical vibration stress are summarized systematically.

An adaptive stochastic resonance method based on multi-agent cuckoo search algorithm for bearing fault detection

Bearing is widely used in the rotating machinery and prone to failure due to the harsh working environment. The bearing fault-induced impulses are weak because of poor background noise, long vibration transmission path, and slight fault degree. Therefore, the bearing fault detection is difficult. A novel adaptive stochastic resonance method based on multi-agent cuckoo search algorithm for bearing fault detection is proposed. Stochastic resonance (SR) is like a nonlinear filter, which can enhance the weak fault-induced impulses while suppressing the noise. However, the parameters of the nonlinear system exert an influence on the SR effect, and the optimal parameters are difficult to be found. Multi-agent cuckoo search (MACS) algorithm is an excellent heuristic optimization algorithm and can be used to search the parameters of nonlinear system adaptively. Two bearing fault signals are used to validate the effectiveness of our proposed method. Three other adaptive SR methods based on cuckoo search algorithm, particle swarm optimization or genetic algorithm are also used for comparison. The results show that MACS can find the optimal parameters more quickly and more accurately, and our proposed method can enhance the fault-induced impulses efficiently.

Expression of Concern on “Reliability Analysis of Random Vibration Transmission Path Systems”

Expression of Concern on “Reliability Analysis of Random Vibration Transmission Path Systems”

Vibration Characteristics of Framed SUV Cab Based on Coupled Transfer Path Analysis

The vibration transmission paths in a sport-utility vehicle with a frame structure were used to evaluate the coupled vibration of each vibration transmission link. This method was based on the transmission path of an “engine-powertrain mount system-frame-vehicle body suspension-body-driver seat rail,” and the research objective was to improve the vibration characteristics of the cab. This coupled transfer path analysis combined analysis and experiment to establish the vehicle vibration transmission path model and a finite element simulation model. With this method, the vibration level of the driver’s seat rail was reduced and engineering practice was effectively used to improve the vibration characteristics of the cab. This method was applied to a framed SUV cabin.

A Multi-Point Iterative Analysis Method for Vibration Control of a Steering Wheel at Idle Speed

Steering wheel vibration control is of great significance to improve the ride comfort of vehicles. However, the coupling effect of the multi-source vibration transfer path makes it difficult to screen out the abnormal vibration transfer intervals. Therefore, a multi-point iterative analysis method (MIAM) is presented in this paper. In addition, this paper researches the characteristics of the main vibration transmission path of a truck and proposes a new vibration isolation structure. Considering the structural characteristics of the modal deformation of the car body, the installation orientation of the measuring point is further adjusted according to the area formed by modal deformation nodes, and a simplified vibration transfer path is presented. After weighing the vibration data of the sensor and considering the vibration transfer rate as the analysis index, the abnormal interval of vibration transmission on the main path was detected. The effectiveness of the improved structure is verified with the modal verification analysis of an extracted steering system model. In addition, the experimental results show that the improved measures reduce the total vibration of the steering wheel by 34% and offsets the peak corresponding frequency by 4.8%, showing the effectiveness of the proposed method and proving its advantages for other vibration control problems.

Research on Vibration of Axial Piston Pump Based on Rotor Dynamics and Vibration Transmission Path

Research on Vibration of Axial Piston Pump Based on Rotor Dynamics and Vibration Transmission Path

Helicopter interior noise reduction using compounded periodic struts

This paper characterizes the performance of a novel compounded gearbox periodic strut on controlling the noise in a helicopter cabin through modelling, simulation and experimental research. The strut exhibits low transmissibility in the specified frequency ranges, called “stop bands”. Based on a certain helicopter model, a dynamic acoustic-structure coupled system is first built by using the finite element method and the transfer matrix method. Subsequently, according to the gear mesh vibration transmission path, analyses of the vibration and noise reduction characteristics are conducted. Compared with the plain strut, attenuations of both vibration and noise in excess of 60 dB are obtained in the simulations. On a specially designed helicopter platform, experimental research is conducted simultaneously on the two aspects of fuselage vibration and cabin noise. The effectiveness of the novel strut used for helicopter cabin broadband noise reduction is demonstrated by the agreement between the simulation and experimentation results, where the attenuations of measured fuselage vibration and cabin noise exceed the levels of 40 dB and 30 dB, respectively, in the frequency range from 300 to 2000 Hz.

Band gap characteristics of periodic gyroscopic systems

The stop and pass bands (i.e. the band gaps) characteristics are determined for gyroscopic systems by developing an approach which is compatible with such class of systems which is based on the concept of Bloch wave propagation in periodic structures. In this approach, the dispersion curves of the periodic gyroscopic systems are determined for different rotational speeds. The obtained characteristics are compared with non-rotating systems in an attempt to quantify the effect of the gyroscopic forces on the “band gap” characteristics. The developed approach is illustrated by a new class of drill strings with passive periodic inserts. These inserts are utilized to filter out the vibration transmission along the drill string. Such mechanical filtering capabilities allow the vibrations to propagate along the periodic drill string only within specific frequency bands called the ‘pass bands’ and completely block it within other frequency bands called the ‘stop bands’. The inserts introduce impedance mismatch zones along the vibration transmission path to impede the propagation of vibration along the drill string. The design and the location of the inserts are selected to confine the dominant modes of vibration of the drill string within the stop bands generated by the periodic arrangement of the inserts in order to completely block the propagation of the vibrations.A finite element model (FEM) that simulates the operation of this new class of drill strings is developed to describe the complex nature of the vibration encountered during drilling operations. The FEM is used to extract the dispersion characteristics of the gyroscopic unit cell of the drill string in order to determine its stop and pass band characteristics. Experimental prototype of the passive periodic drill string is built and tested to demonstrate the feasibility and effectiveness of the concept of periodic drill string in mitigating undesirable vibrations. The experimental results are used to validate the developed theoretical model in order to develop a scalable design tool that can be used to predict the dynamical behavior of this new class of drill strings.

A scaled experimental research on reducing metro railway vibration by using trench and barriers

In order to research on reducing vibration by using trench and barriers at the vibration transmission path, the presented paper introduced a test campaign in a 1:5 scaled benches. The tests were conducted for four different conditions, including the control condition, open trench, concrete barriers, and concrete barriers with PUR mat. Findings indicated that the specific barriers made of concrete with elastic PUR layer can indeed efficiently reduce the transmission through the soil of vibrations.

Reliability analysis of random vibration transmission path systems

The vibration transmission path systems are generally composed of the vibration source, the vibration transfer path and the vibration receiving structure. The transfer path is the medium of the vibration transmission. Therefore, the uncertainty of path parameters influences the system reliability greatly. In order to avoid the resonance failure, the transmission reliability analysis and the reliability sensitivity analysis are both very important. Based on the reliability theory, the absolute value difference of natural frequency and excitation frequency of random vibration transmission path system was limited and the reliability pattern of the resonance problem was defined in this paper. Applying the generalized second moment technique of vector-valued functions and the stochastic finite element theory, the theoretical analysis method of the transmission reliability and reliability sensitivity was presented. The corresponding vibration transmission path system with uncertain path parameters including mass, stiffness and path position was analyzed theoretically and computed numerically, and then the correlated mathematical expressions were obtained. Thus, in practical project, most of uncertain factors in the vibration systems can be analyzed so that the effective way can be given to avoid resonance failure.

Vibration signal–based fault diagnosis in complex structures: A beam-like structure approach

Sensor network–based data-driven fault diagnosis in complex structures using limited prior knowledge is an interesting and hot topic in the literature. In this study, an integrated feature characterization and fuzzy decision method is developed based on a novel beam-like structure approach for fault diagnosis using available limited prior knowledge. Complex structures embedded with vibration sensors can be regarded as some virtual beam-like structures by considering the vibration transmission path from vibration sources to each sensor. The dynamic response of the structures in this vibration transmission path can demonstrate obvious fault features if there is a fault (typically, for example, cracks in connecting rods or around bolts, and bolt-loosening). These fault features can be effectively characterized and efficiently captured and utilized for fault diagnosis with a fuzzy decision method based on the virtual beam-like structure concept. This novel virtual beam-like structure approach needs only limited prior knowledge of the faults and does not require stationary response data. It is also not with respect to a specific structure design and is easy to implement within a sensor network. The effectiveness of the proposed method is well validated in the experiments for fault diagnosis including loosening bolts or cracks around bolts of complex structures such as bolted-base hanging structures in satellites.

Localized fault detection of sun gears based on windowed synchronous averaging in the angular domain

The vibration transmission paths between the fixed-mounted accelerometer and the meshing points of the sun gear’s local fault gear tooth is time varying in a planetary gearbox. Consequently, the conventional time synchronous averaging used in vibration-based fault detection of fixed-axis gearboxes is invalid for the localized fault detection of sun gears. To address the noise reduction, the windowed synchronous averaging originally introduced by McFadden can be employed to extract the useful components and reduce the effect of transmission paths. However, the speed fluctuation makes the above method inapplicable in real-world applications. In order to improve the robustness of windowed synchronous averaging under the speed fluctuation condition, a non-separation version of the windowed synchronous averaging in the angular domain is proposed in this article to address the speed fluctuation. In this scheme, the windowed time-domain signal is resampled at constant angular increments by the computed order tracking, which converts the non-stationary signal in the time domain into the stationary one in the angular domain. Then, the windowed angular-domain signal is processed by the synchronous averaging. In this way, the frequency blur and waveform distortion caused by rotating speed fluctuations can be eliminated. Experiments are conducted to verify the validity of the proposed method.

Power flow analysis of built-up plate structures using the dynamic stiffness method

The dynamic stiffness method (DSM) in our recent paper, which can consider both in-plane and out-of-plane vibrations simultaneously, is formulated to investigate the power flow characteristics of built-up plate structures. Prior to power flow analysis, comprehensive validation works on our DSM are performed so as to better exhibit its numerical capabilities. Power input and power transmission within a two-plate structure are then analyzed by following the context of in-plane and out-of-plane vibrations. In addition, three vibration transmission paths within a multiple plate structure are characterized in terms of power flow densities, which can provide better physical insights in vibration transmission within complex plate structures. Compared to power flow analysis based on the well-known reception/mobility method, our approach is strongly recommended for the dynamics of built-up structures since it can assemble the overall stiffness matrix in a straightforward manner like that in the conventional finite element technique.

Time-Frequency Analysis of Torsional Vibration Signals in Resonance Region for Planetary Gearbox Fault Diagnosis Under Variable Speed Conditions

Translational vibration-based methods have been widely used for machinery fault diagnosis. However, because of the unique gear configuration and complex kinetics, planetary gearbox translational vibration signals have complex modulation features due to gear faults and time-varying vibration transmission paths. This results in complex frequency components of translational vibrations, and adds difficulty to gear fault signature extraction. Under variable speed conditions, the resultant time-variant frequency components and complex sidebands may overlap in frequency domain, thus making it more difficult to pinpoint fault features. To address this issue, torsional vibration signals are exploited, because they are free from the extra modulation effect due to time-varying transmission paths and have simpler frequency contents. Gear faults generate impacts, thus exciting resonances and leading to modulations on resonances. Therefore, torsional resonance frequency band is concentrated to extract gear fault information. The time-variant but symmetric sideband characteristics in the resonance region are derived based on the explicit time-varying amplitude modulation and frequency modulation signal model. Resonance frequencies are identified under variable speed conditions by virtue of their independence on running conditions. Furthermore, time-frequency analysis is utilized to extract time-variant gear fault frequencies. The proposed method is validated using both numerical simulation and lab experimental data. Localized faults of the sun, planet, and ring gears are diagnosed under variable speed conditions.

Dynamic Modeling and Characteristic Analysis of Floating Raft System with Attached Pipes

The vibration transmission performance of a floating raft system with attached pipes is investigated in this paper. The frequency response function-based (FRF-based) substructure synthesizing method whose accuracy has been verified by numerical simulations and experiment is applied for modeling the system. The power flow through the transmission paths is used for exploring the additional vibration transmission path provided by the attached pipes. The results show that the existence of the additional transmission paths caused by the pipes breaks the symmetries of the system, which leads to the enhancement of the coupling between each substructure. Consequently, it degrades the vibration isolation performance of the raft system. Moreover, a parametric study is performed to investigate the effects on the mean-square velocity of the hull of the attached pipes, which gives a brief guideline for designing the attached pipes.

Reliability Analysis of Random Vibration Transmission Path Systems

The vibration transmission path systems are generally composed of the vibration source, the vibration transfer path, and the vibration receiving structure. The transfer path is the medium of the vibration transmission. Moreover, the randomness of transfer path influences the transfer reliability greatly. In this paper, based on the matrix calculus, the generalized second moment technique, and the stochastic finite element theory, the effective approach for the transfer reliability of vibration transfer path systems was provided. The transfer reliability of vibration transfer path system with uncertain path parameters including path mass and path stiffness was analyzed theoretically and computed numerically, and the correlated mathematical expressions were derived. Thus, it provides the theoretical foundation for the dynamic design of vibration systems in practical project, so that most random path parameters can be considered to solve the random problems for vibration transfer path systems, which can avoid the system resonance failure.

A sensor network based virtual beam-like structure method for fault diagnosis and monitoring of complex structures with Improved Bacterial Optimization

This paper proposes a novel method for the fault diagnosis of complex structures based on an optimized virtual beam-like structure approach. A complex structure can be regarded as a combination of numerous virtual beam-like structures considering the vibration transmission path from vibration sources to each sensor. The structural ‘virtual beam’ consists of a sensor chain automatically obtained by an Improved Bacterial Optimization Algorithm (IBOA). The biologically inspired optimization method (i.e. IBOA) is proposed for solving the discrete optimization problem associated with the selection of the optimal virtual beam for fault diagnosis. This novel virtual beam-like-structure approach needs less or little prior knowledge. Neither does it require stationary response data, nor is it confined to a specific structure design. It is easy to implement within a sensor network attached to the monitored structure. The proposed fault diagnosis method has been tested on the detection of loosening screws located at varying positions in a real satellite-like model. Compared with empirical methods, the proposed virtual beam-like structure method has proved to be very effective and more reliable for fault localization.

Vibration signal modeling of a planetary gear set with transmission path effect analysis

For a planetary gear set, the transducer-perceived vibration signal contains vibration information from multiple sources including the sun gear, planet gears, and the ring gear. All these vibration sources are subject to corresponding transmission path effects. In this paper, a comprehensive vibration signal model for a planetary gear set is proposed considering all the vibration sources and transmission path effects. Vibration sources were generated with a nonlinear two-dimensional lumped-parameter dynamic model. Transmission path effects are modeled as two parts: the part inside the gearbox to the casing and the other part along the casing to the transducer position. Given the gear sizes, the transmission path effect modeling parameters are estimated. Then the influences of different transmission paths on resultant vibration signals are analyzed. Some vibration characteristics are revealed for one healthy planetary gear set. These vibration characteristics are validated with lab experimental data in both time domain and frequency domain.

Development procedure for a vibration transmission element using a reversed design optimization method

Mechanical structures are generally composed of vibrational focal components, components in the vibration transmission path and vibration evaluation locations. The evaluation of vibration is conducted at vibration evaluation locations using results obtained from the frequency domain. However, engineers normally repeat the manufacturing of vibration transmission elements by utilizing their experience and intuition until the desired vibration levels have been obtained. Through this general process, the engineers seek for the optimal configuration of the transmission element that can satisfy the desired vibration level. In this research, we attempted to determine the configuration of the transmission component that minimizes vibration at the evaluation position by reversing the standard approach in the process described. In addition, this reverse approach is performed along with a size optimization in the design optimization methods.

Analysis of Energy Transfer and Distribution Characteristics of the Gearbox Vibration Transmission Channel Based on Energy Finite Element

For a wide range of applications of gearbox system,starting in gear box system vibration mechanism and the analysis of vibration transmission path,this paper establishes a analysis model of gearbox elastic coupling system.Analyzes energy transfer characteristic of the complex coupling structure of gearbox system based on admittance theory.From the perspective of energy distribution,analyzes of the characteristics of energy distribution of the different parameters and different structural arrangement.