Vibration Engineering Articles
Timber-to-timber composite floors connection optimization for vibration and deflection reduction
By Yuri De Santis, Francesca Pancella, Dag Pasquale Pasca, Angelo Aloisio, Massimo Fragiacomo
Timber floors are prone to vibration due to the reduced modulus of elasticity of the material. Composite floors represent the most convenient solution to achieve acceptable performances and at the same time to save material and cost. In determining the natural frequency of a composite floor, the stiffness of the connection between the joined structural member is crucial. Inclined screws connections are characterized by the highest slip modulus among the mechanical fastener connections. However, the determination of the optimal inclination angle of the screws for vibration and deflection reduction remains an unexplored issue. The optimization problem is faced by means of an analytical model of beam on foundation.
Applying deep learning and wavelet transform for predicting the vibration behavior in variable thickness skew composite plates with intermediate elastic support
By Wael A. Altabey
A convolutional neural network method based on Adam optimizer with power-exponential learning rate for bearing fault diagnosis
By Youming Wang, Zhao Xiao, Gongqing Cao
Fault diagnosis and health management of bearings in rotating equipment based on vibration analysis – a review
By Adnan Althubaiti, Faris Elasha, Joao Amaral Teixeira
A review on wind turbines gearbox fault diagnosis methods
By H. Gu, W. Y. Liu, Q. W. Gao, Y. Zhang
Journal of Vibroengineering
Investigation of dynamic properties of the microturbine with a maximum rotational speed of 120 krpm – predictions and experimental tests
Advances in the development of analysis and design methods for fluid-flow machines have enabled both their multi-criteria optimisation and miniaturisation. To decrease the size of such a machine whilst, at the same time, maintaining its output power level, the rotor’s rotational speed needs to be increased. It is the reason for serious difficulties with respect to the rotor dynamics and the selection of a bearing system. This article discusses the simulation analysis and experimental research carried out on a prototypical microturbine, designed for use in a domestic ORC (organic Rankine cycle) cogeneration system. During the design process, the basic assumption was to develop a turbomachine, whose dimensions would have been as small as possible and whose output electric power would have been about 1 kilowatt. A supersonic impulse turbine, with a nominal rotational speed of 100,000 rpm, was used in order to obtain high flow efficiency. The maximum speed of the rotor was determined at a level of 120,000 rpm. The article presents the results of analyses made at the design stage and preliminary results of the experimental research. The numerical simulations covered the bearing system optimisation and the rotor dynamics analysis. Next, based on the outcomes of these analyses, a decision was made to use non-conventional gas bearings which are fed by the low-boiling medium’s vapour that comes from the ORC system. Within the framework of the experimental research, the dynamic behaviour of the turbogenerator was examined in terms of the rotational speed and produced energy. The performed measurements are proof of very good dynamic properties of the tested machine and after the research was over it was concluded that there were absolutely no signs of wear of the turbogenerator’s subassemblies.
Ground vibration propagation and attenuation of vibrating compaction
When a high-power vibrating roller compact the subgrade, the vibration wave will quickly propagate along the surface of the subgrade and generate hazards to surrounding environment and structure. To study the vibration propagation rules of the roller, the vibration acceleration of the high-power vibrating roller was measured on the surface of the rock subgrade, coarse-grained soil subgrade and fine-grained soil subgrade. The respective relations between vibration acceleration and the distance from a vibration source in the vertical, horizontal radial and horizontal circumferential direction have been discovered. The research results show that the vibration peak frequency generated by the vibrating roller on the subgrade approximates vibration frequency. The vibration effective influence distance varies from 10m to14m, and the horizontal radial vibration is greater than that of vertical and horizontal circumferential direction. The vibration of the rock subgrade attenuates the most slowly and propagates the most remotely.
Bearing fault diagnosis based on improved VMD and DCNN
Vibration signal produced by rolling element bearings has obvious non-stationary and nonlinear characteristics, and it’s necessary to preprocess the original signals to obtain better diagnostic results. This paper proposes an improved variational mode decomposition (IVMD) and deep convolutional neural network (DCNN) method to realize the intelligent fault diagnosis of rolling element bearings. Firstly, to solve the problem that the number of decomposed modes of variational mode decomposition (VMD) needs to be preset, an IVMD method is proposed, where the mode number can be determined adaptively according to the curve of the instantaneous frequency mean of mode functions. With this method, the vibration signal can be decomposed into a series of modal components containing bearing fault characteristic information. Then, DCNN is employed to fuse these multi-scale modal components, which can automatically learn fault features and establish bearing fault diagnosis model to realize intelligent fault diagnosis eventually. Experimental analysis and comparison results verify that the proposed method can effectively enhance the bearing fault features and improve the diagnosis accuracy.
Dynamical processes in a multi-motor gear drive of heavy slabbing mill
A real case study is represented of abrupt failures in a new multi-motor gear drive of vertical rolls in the heavy slabbing mill. Modal analysis is conducted, and the lowest torsional vibration modes are verified by the data from an industrial plant. Conditions of parametric resonances due to variable stiffness of teeth are determined within the range of working speed. The branched gear drive is investigated by the non-linear dynamical model with backlashes. It is shown that instantaneous dynamic loads in driveline are strongly dependent on the difference in gap sizes and phase shift between two intermediate gears in the output gear wheel coupling. Deviation in electrical parameters by 0.5 % is considered as the additional cause of not equal load sharing of parallel motors. Results of this research allowed preventing further failures of the gearbox and optimizing slabbing mill control. The proposed approach can be used in other multi-motor machines.
Journal of Vibroengineering
Comprehensive platform for advancements in the field of vibration engineering
Best of Theme
June 25, 2019
Mechanics of robot inspector on electrical transmission lines conductors: performance analysis of dynamic vibration absorber
By Mohammad Reza Bahrami, Salam Ahmed Abed
September 30, 2019
Combustion monitoring in engines using accelerometer signals
By S. Narayan, Sasa Milojevic, Vipul Gupta
December 31, 2018
An intelligent fault diagnosis method of rotating machinery using L1-regularized sparse filtering
By Weiwei Qian, Shunming Li, Jinrui Wang, Zenghui An, Xingxing Jiang
September 30, 2019
Fault diagnosis method for energy storage mechanism of high voltage circuit breaker based on CNN characteristic matrix constructed by sound-vibration signal
By Shutao Zhao, Erxu Wang, Jiawei Hao
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Modal finite element analysis of PCBs and the role of material anisotropy
By Uday H. Kalyani, Mark Wylie
Printed Circuit Boards (PCBs) are epoxy resin-impregnated and cured sheets of counter woven glass fabric (e.g. FR4) laminated between thin sheets of Copper. The nature of the PCB is inherently anisotropic and inhomogeneous but previous modal FEMs of PCBs have assumed isotropic, anisotropic (transversely isotropic and orthotropic) material properties and shown good correlation with test data for specific scenarios [1-3]. This paper details part of a research program aimed at gaining a better understanding of accurately modeling PCB’s dynamic behavior. New investigations into the impact of material anisotropy and, in particular, the effect of material orthogonal plane definition (Ex and Ey) on eigenfrequencies is analysed. A modal FEM of a JEDEC PCB is created, verified, and validated using well established theories by Steinberg and empirical data by others [4, 5]. The relative contributions of Ex, Ey and Ez on PCB eigenfrequencies is examined using a parametric modal FEM, analysing the role of material isotropy verses anisotropy. The impact of transversely isotropic material properties is also analysed for a typical JEDEC PCB. This analysis details the mesh density required for accurately modeling the PCB eigenfrequencies. The results show that a 100 % increase in Ez has only a 0.2 % difference in the eigenfrequency where as a 100 % increase in Ey has a 1.2 % difference in the eigenfrequency. The effect of orthotropic plane definition (alternating Ex with Ey) on the JEDEC PCB amount to a 7.95 % delta in eigenfrequency.
Development of an underwater robotic arm using multibody dynamics approach
By S. Fernando, M. Perera
Underwater robotic arms are important devices that enables workers to carry out tasks remotely from a safe distance reducing or eliminating the risks that are involved with the task. The primary objective of the robotic manipulator is to perform maintenance and cleaning activities of the hull of a ship. However, the control of these devices underwater is quite complicated due to the numerous factors that make these systems unstable and non-linear. The aim of this study is to develop a multibody dynamic robotic manipulator model, integrated with a control strategy to optimize and obtain stable kinematics solutions. The hydrodynamic forces are integrated to the manipulator model considering buoyancy forces and surface drag forces. A basic algorithm is used to generate the joint angles using 7 geometrical parameters. The control of the manipulator was done to simply follow any path that represents the given coordinates. The P, I and D parameters are tuned individually to optimize the kinematic solution of the manipulator. 3-DOF articulated manipulator is the commonly used manipulator configuration. However, a 6-DOF manipulator configuration was selected in this study to allow for change in orientation using wrist motions.
Numerical simulation of hydraulic fracturing in transversely isotropic rock masses based on PFC-2D
In order to make a better understanding of the hydraulic fracturing in transversely isotropic rock masses, the modified particle flow modeling method was used by embedding the smooth joint models within an area of certain thickness, and the optimized fluid-mechanical coupling mechanism was applied in hydraulic fracturing modeling. On this basis, the influence of the injection rates, in-situ stress ratios and inclination angles of the bedding planes on the breakdown pressure and propagation of the hydraulic fractures was analyzed. The simulation indicated that: 1) Excessive small or large injection rates would lead to the increase of the breakdown pressure of the hydraulic fractures. 2) Under different inclination angles of the bedding planes, the crack breakdown pressure increased linearly with the increasing of the in-situ stress ratios. And under conditions of different in-situ stress ratios, the crack breakdown pressure changed as a ‘wave’ type with the increasing inclination angles of bedding planes. 3) Both the in-situ stress ratios and the inclination angle of bedding planes affected the propagation of the hydraulic fractures. The existence of the bedding planes would induce the hydraulic fractures to propagate along the bedding planes. The large inclinations of the bedding planes would cause the hydraulic fractures to keep propagating with the direction of maximum principal stress.
Research on blasting vibration effect and time-frequency characteristics of vibration signals in a road corridor at xianning nuclear power station
Drill and blast is a major method for foundation excavation in nuclear power plant engineering. For transporting heavy components to engineering construction, the blast-induced vibration of foundation excavation in a road corridor may has a great influence on new pouring mass concrete and surrounding bedrock in Xianning Nuclear Power Station, which will affect the safety of the engineering construction. So it is necessary to monitor the process of blasting excavation and put forward effective control measures on blasting vibration effect, in which the peak particle velocity (PPV) attenuation law are investigated through regression analysis of practical field data by Duvall empirical formula and the time-frequency characteristics was analyzed by wavelet transform and wavelet package decomposition. By analyzing the velocity amplitude and power spectrum density amplitude of wavelet components, it shows the blast energy of original vibration signal is mainly within the frequency below 250 Hz and has three sub-band which varies from 10 Hz to 30 Hz, from 40 Hz to70 Hz and from 75 Hz to 125 Hz, respectively. Wavelet packet analysis indicates the energy of the signal in 0-125 Hz accounts for 94.25 % of the total signal. At the same time, for the sake of ensuring the safety of road corridor, Chinese admissibility standards (GB6722-2014) of blasting-induced vibration and the constants obtained from the regression were used to establish the maximum explosive charge per delay for an acceptable ground vibration level that would not cause damage for new pouring mass concrete and bedrock in road corridor. The safety criteria of particle vibration velocity for new pouring mass concrete and bedrock in road corridor could be both set as 5 cm/s, which show the remarkable effect on blasting damage control of the new pouring mass concrete and surrounding bedrock, the results demonstrate that controlling maximum explosive charge per delay methodology can be commendably applied to road corridor to control blasting-induced vibration effects.