Journal of Vibroengineering
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A new method to enhance of fault detection and diagnosis in gearbox systems
Get PDFThe kurtogram analysis presents some limitations when diagnosing gearbox systems, particularly in time domain. Its envelop signal analysis is not able to detect any defects. This paper presents a new approach to enhance the detection and diagnosis in gearbox systems. This new approach is based on Maximum Correlated Kurtosis Deconvolution combined with Spectral Kurtosis fault diagnosis methodology. This technique allows us to obtain better detection in the gearbox system which is not the case of the spectral kurtosis analysis alone. For this purpose, a dynamical model of a simple stage gearbox is proposed. The approach can detect and identify at early stage the gearbox and also the crack tooth defects
Vibration-based damage detection of concrete gravity dam monolith via wavelet transform
Get PDFThis study has presented a method to estimate the damage location in the concrete gravity dam monolith. The first four vibration mode of the highest monolith of the Koyna dam was estimated and analyzed by the combined discrete and continuous wavelet transform. The position of the damage scenarios was identified by using bior 3.9 wavelet in the spatial variation of the data response. The sensitivity of wavelet to random signal noise was investigated by using noise to displacement response of cracked monolith. Three noise levels were introduced in the model and the capacity of this method to detect damage from noisy data was discussed
Analysis of the blast-induced vibration structure in open-cast mines
Get PDFBlasting in opencast mines is characterized by the use of large masses of explosives for a single blast. Blasting is done in a series of several to tens or even hundreds of charges placed in long holes and fired with a millisecond delay. Works are often carried out in the vicinity of buildings; therefore, reducing vibration impact is essential for opencast mines. This paper presents the applicability of the method of time-frequency Matching Pursuit (MP) for analysis of vibration structure. The use of MP analysis enables the development of much deeper and more reliable impact assessments of blasting on the environment
The modal analysis of disc resonator gyroscope using isogeometric analysis
Get PDFThis paper presents a free vibration analysis of the disc resonator gyroscope (DRG) based on the Isogeometric Analysis (IGA). The non-uniform rational B-splines (NURBS) basis functions are employed to represent both the exact geometry of DRG and displacement fields. It provides a unified process between the geometric design and analysis which significantly reduces the design cycle by eliminating the re-meshing process. Moreover, the modeling process of IGA and the numerical example of three-circle cascaded model with four different refinement schemes are presented and the computational accuracy and efficiency of the present numerical method are verified by comparing with the standard finite method (ABAQUS)
A new beamforming microphones array with acoustic insulation baffle
Get PDFTo eliminate the influence of the interference acoustic source behind the array on the source identification performance, some modifications on the traditional single-layer beamforming microphone array are made, a new array with acoustic insulation baffle in the microphone plane is given out to suppress the influence of interference acoustic source. Simulation and verification results show that, with the presence of the interference acoustic source in the rear of traditional planar array, the acoustic source position and amplitude deviations are larger and it indicates that the interference acoustic source seriously affects the identification performance of target acoustic source. Compared to the performance of traditional planar array, the new microphone array with acoustic insulation baffle can effectively eliminate the influence of interference acoustic source behind the array and improve the accuracy of the location and amplitude of the target acoustic source. The experiment verifies the correctness of the simulation conclusions and the applicability of the modified microphone array in the cabin of automotive and aircraft and other narrow space
Multi-objective topology optimization to reduce vibration of micro-satellite primary supporting structure
Get PDFWe applied multi-objective topology optimization to reduce vibration of the primary supporting structure of video satellites in the frequency domain. The optimal structure is obtained by the multi-objective topology optimization with stiffness and random vibration response as the targets. This is compared with the optimal structure obtained by single-objective topology optimization with stiffness as the target. The dynamic analysis results show that the root mean square values in all three spatial directions of the optimal structure by the multi-objective optimization are smaller than that of the single-objective optimization. The maximal declining value reaches 2.94 g, and the maximal declining degree is 30.6 %. The maximal declining response value on the top of the cylinder reaches 3.87 g with a degree of 33.0 %. The results demonstrate that the multi-objective optimization method significantly improves the vibration response of the base plate, which therefore suppressed the vibration of the satellite. An acceptance condition experiment is performed for the satellite with the optimal base plate from the multi-objective optimization. The dynamic analysis results match well with the experimental data, and verify the applicability of the multi-objective optimization
Wheel vibration estimation of railway vehicle utilizing state observer
Get PDFWheel vibration is one of the most crucial factors associated with the running safety of a train. How to detect and estimate it in real-time attracts significantly researchers’ interest recently? In this paper, a new method of estimating the wheel vibration of a railway vehicle utilizing a partial state observer is proposed. The partial state observer of wheel vibration estimation is designed based on the railway vehicle dynamic system model established in state space. Different kinds of track irregularities are considered as inputs for the vehicle dynamic system. Subsequently, the state responses of the car-body and the bogie frame obtained from dynamic simulation are used as the inputs of the partial state observer. The simulations were conducted at various running speeds of a vehicle. The results show that the partial state observer is capable of estimating well the wheel vibration using dynamic responses of the car-body and the bogie frame, and has a stable convergence, which leads to get consistent with the real dynamic system after duration of 0.15 s from starting system. This method thus would provide an innovative approach to estimate the wheel vibration of a real railway vehicle in real-time
Fluctuation characteristics and rolling control for an underactuated spherical underwater exploration robot
Get PDFCompared with other underwater exploration robots, Spherical underwater robot has an outstanding advantage for the underwater exploration, whose spherical shell has the excellent resiliency to protect the internal electronic components. In addition, this steering resistance is very small to move flexibly. In this paper, a type of spherical underwater robot with the pendulums and a propeller was studied on moving at the water bottom in a rolling manner. The structure and force were analyzed to understand that the hydrodynamic force’s affection on the robot’s rolling at the water bottom. A mathematical model was established with the mass parameters and speeding parameters. The virtual simulation environment was established in Adams software. Furthermore, the coupling fluctuation characteristics of the speed, swing angle and the torque were studied by the simulation and the experiment in a pool. The study proved that this robot not only can use the propeller to move in water, but also can roll at the water bottom by driving the spherical shell. Especially, the result also can be obtained that the robot can roll at water bottom stably by increasing the pendulum mass and lowering the motor speed
Damage mechanism of stabilizing piles suffered from liquefaction based on dynamic numeric analyses
Get PDFA large deformation from liquefaction in saturated subgrade may lead to the instability of slope and the damage of the reinforcement measures. Firstly, in order to evaluate the damage mechanism of stabilizing piles suffered from the saturated subgrade liquefaction, this paper perform a dynamic centrifuge modelling test using a kind of stabilizing concrete model pile to study the dynamic water pore pressure, landslide of slope and dynamic crack of the stabilizing pile. Secondly, the breaking damage mechanism of the stabilizing pile is discussed under the condition of a large liquefaction deformation by means of the dynamic consolidation finite element method. The study shows that the large deformation of the reinforced slope caused by the liquefaction leads to a decrease in the earth pressure in front of the stabilizing pile and an increase in the earth pressure behind the stabilizing pile. These comprehensive effects result in a significant increase in the dynamic excess bending moment of the stabilizing pile, and eventually, the total static and dynamic bending moment of the stabilizing piles exceeds the ultimate bending moment and leads to the breaking damage of the piles
Aerodynamic performance analysis of wind-sand flow on riding-type hangers of suspension bridges
Get PDFWith global climate and environment deterioration, the desertification is getting worse and the phenomenon of wind-sand flow frequently occurs in many areas. Hangers of suspension bridges may suffer the impact from wind-sand flow and be damaged. In this study, the riding-type hangers with four strands which are the commonly used hanger of long-span suspension bridges are taken as an example to investigate the influence of wind-sand flow on the hangers. The aerodynamic interference effect can occur among the four strands under the action of wind-sand flow. In order to explore the influence of wind-sand flow on the hangers, the wind-sand flow field around the riding-type hangers of a long-span suspension bridge is simulated within the FLUENT software on the basis of the numerical simulation of computational fluid dynamics. The pressure and velocity contour, aerostatic coefficients and forces produced by the wind-sand flow under different wind attack angle and volume fractions of sand phase are analyzed from the simulation. Results indicate that the forces exerted by the wind-sand flow on riding-type hangers are greater than the forces exerted only by wind. In the wind and wind-sand flow field, the drag and lift coefficients of the front two strands of hangers exhibit minor changes with increasing wind attack angle, whereas those of the back two strands increase first and then decrease to a small value. The volume fraction of the sand phase has an insignificant effect on the drag and lift coefficients, but has a significant effect on the force exerted on the hanger, and the force exerted on the hangers multiplies when the volume fraction of the sand phase multiplies. The results lay a theoretical foundation for the corrosion fatigue analysis of riding-type hangers for large-span suspension bridges under the action of wind-sand flow