Journal of Vibroengineering
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Vibroactivity analysis of a dual fuel diesel engine based on the knock sensor signal and measuring pressure in the combustion chamber
Get PDFA study conducted by a team of authors attempts to identify the occurrence of knocking based on the vibro-acoustic signal from the knock sensor and the signal from the pressure sensor glow plug (PSG). The reason the authors decided to discuss the issue is increasing interest in the use of information contained in the generated vibration and acoustic emissions as well as reducing acoustic emissions as one of the environmental threats. The adopted form of experiment and analysis enables determining the validity of testing of NVH multifuel engines. Information based on the vibro-acoustic signal allows to determine the qualitative and quantitative occurrence of the phenomenon of knocking in case of proper analysis. Both the energy spectrum of the vibration and the summation value of the successive bands of the spectrum confirm the occurrence of knock resulting from the analysis of the pressure in the combustion chamber and allow to relate to its intensity
The effect of an orifice plate with different orifice numbers and shapes on the damping characteristics of a dual-chamber air spring
Get PDFA dual-chamber air spring is an important vibration absorber. The shape and number of damping orifices directly influence the damping characteristics of dual-chamber air springs. The study investigates the application of damping characteristics of gas-liquid coupling dual-chamber air springs to mitigate the motion of a marine floating platform. An experimental method is used to analyze the influence of changes in the orifice number and shape on the damping characteristics of dual-chamber air springs given the same opening area. To analyze the effect of various orifice shapes, the study adopts a non-dimensional number to measure the image complexity, namely area/perimeter2 ratio. Additionally, two non-dimensional numbers are considered simultaneously, namely the orifice number and tightness factor, and the influence of changes in the orifice number and orifice position layout on damping characteristics of circular and square orifices is investigated, given the same opening area. The damping cloud map and a formula to calculate the damping for the gas-liquid coupling dual-chamber air springs are obtained by analyzing the experimental data. The proposed formula can be used to quickly calculate the damping coefficients of the dual-chamber air springs when the number and position layout of the orifices are known
Optimization the inner product vector method and its application to structural health monitoring
Get PDFFast methods to identification and recognition of structural defects are important issues for the industry. In recent years, a growing interest has been on quick structural inspection to significantly reduce inspection’s cost and time, while minimizing the number of Non-Destructive Testing (NDT). Investigations on damage detection methods based on vibration monitoring have been developed in the last decade. This paper presents a study on Inner Product Vector (IPV) method. The IPV method is a new vibration based damage detection technique. In this method vibration responses are measured before and after damage occurrence. The vibration responses include the time domain acceleration (or displacement or velocity). The IPV method has the potential to significantly reduce costs by minimizing the need for NDT methods. For damage detection via the IPV method, a threshold should be selected for classifying the damaged and undamaged sections of a structure. Proper determination of the threshold value requires selection of Confidence Interval Factor (CIF). In this study, a new algorithm for the IPV method is suggested in which a new optimized model for damage detection is presented. Aforementioned optimized model can provide an accurate value for the CIF. To ascertain the exact CIF, the damage detection method is simulated. An accurate threshold makes the IPV method capable to accurately detect damages. The method has been verified by means of an FEM model as well as an experimental case study. The results show that the optimization process can be used as a reference to ascertain value for the CIF. The IPV method can be used as a Structural Health Monitoring (SHM) method, but it’s necessary to optimize the IPV method for each sample
Vibration-based classification of centrifugal pumps using support vector machine and discrete wavelet transform
Get PDFDue to the quick advancement of technology, application of different methods is highly required to maintain the high quality of production and health assessment of production lines. Hence, condition monitoring is widely used in the industry as an efficient approach. The purpose of the present study was to classify faults in centrifugal pumps using the vibration signal analysis and support vector machine (SVM) method. Vibration signals were decomposed in three levels by Daubechies wavelets, and a total of 44 descriptive statistical features were extracted from detail coefficients and approximation coefficients of the wavelets. In order to find the best model for fault classification of centrifugal pumps, parameters such as penalty, degree of polynomial, and width of the Gaussian radial basis function kernel (RBF kernel) were investigated. The classification results using the SVM method indicated that the maximum classification accuracy was 96.67 percent, which was obtained at an RBF kernel width of 0.1 and a penalty parameter value of 1
Effects of pile rows on vibration reduction in nearly saturated soil
Get PDFThis paper presents an analysis about the vibration reduction effects by a barrier in a nearly saturated soil medium. The barrier is assumed to consist in an arbitrary distribution of parallel cylindrical piles embedded in an infinite nearly saturated soil. Based on the equations governing the motion of nearly saturated soil, the complex wave numbers and amplitude ratios between the liquid phase and solid phase are first derived according to the Helmholtz decomposition theorem. With the aid of the Graff’s addition theorem, the unknown multiple complex scattering coefficients by an arbitrary configuration of piles as barriers are determined by taking an advantage of the boundary conditions at pile-soil interfaces and the linear independence of trigonometric functions. Then the corresponding expressions for the nearly saturated soil displacements at both sides of the pile rows can be obtained. The numerical results show that soil saturation degree and permeability exert significant influences on the isolation effectiveness of pile rows, and that the distance between neighboring rows is crucial for the isolation effectiveness. The isolation rules can provide useful guidelines to the design of pile rows as barriers in nearly saturated soil
Nonlinear dynamic modeling and fuzzy sliding-mode controlling of electromagnetic levitation system of low-speed maglev train
Get PDFThe electromagnet levitation system (ELS) of low-speed maglev train is taken as the research object. The nonlinear dynamics and control law of ELS are discussed. Specifically, by employing the Euler-Lagrange’s method, a nonlinear dynamic model is constructed for the single-ELS. Then, the linear control law is studied, which has a disadvantage of weak robustness. To improve the performance of the controller, a fuzzy sliding-mode control law is proposed. According to the dynamic nonlinear model, a novel sliding surface which can make the system reach the stable point within the finite time is presented. Moreover, the fuzzy inference method is utilized to slow down the speed of the states crossing the sliding surface. The simulation results demonstrate that the global robustness of external disturbance and parameter perturbation can be achieved through the proposed control law. And the chattering phenomenon can be reduced significantly. Finally, the experiments are also implemented to examine its practical dynamic performance of the proposed control law
System identification of force transducers for dynamic measurements using particle swarm optimization
Get PDFA method of system identification for force transducers against the oscillation force is developed. In this method, force transducers are equipped with an additional top mass and excited by a facility with the sine mechanism. Particle swarm optimization (PSO) algorithm is employed to identify the parameters of the derived mathematical models. For improving the convergence speed of PSO, exponential transformation is introduced to the fitness function. Subsequently, numerical simulations and experiments are carried out, and consistent results demonstrate that the identification method proposed in this investigation is feasible and efficient for estimating the transfer functions from sinusoidal force calibration measurements
Numerical study on parameter impact on fundamental frequencies and dynamic characteristics of pre-stressed concrete beams
Get PDFThis paper established 6 kinds of different concrete beams, and 5 kinds of models were applied horizontal pre-stress. Their fundamental frequencies and deflections were numerically computed, and the correctness of numerically computational model was experimentally verified. Fundamental frequencies of 6 kinds of models were 46.23 Hz, 68.45 Hz, 69.36 Hz, 70.46 Hz, 72.11 Hz and 157.73 Hz respectively. Concrete beams without being applied pre-stress had a low fundamental frequency. The fundamental frequency of concrete beams could be obviously improved through internally applying pre-stressed tendons to concrete beams. In addition, the improvement effect of Model 5 was more obvious. When pre-stressed tendons were externally applied to the concrete beam, the fundamental frequency was greatly improved. However, externally pre-stressed tendons would limit the use of concrete beams and increase the cost. When other parameters remained unchanged, the fundamental frequency of pre-stressed concrete beams would gradually increase with the increase of pre-stress. When the pre-stress was the same, fundamental frequencies gradually increased with the increase of eccentricity, the number of circular tendons in composite tendons and concrete strength, and gradually decreased with the increase of counterweight. When the applied load was the same, Model 1 was not strengthened and its deflection was the largest. On the contrary, the model which was applied external pre-stress and its deflection was the smallest, but its use was limited and cost was high. In the strengthening proposals of internal pre-stress, composite tendons were applied to Model 5, and it presented a small deflection. When other parameters remained unchanged and the applied load was lower than a value, the deflection of concrete teams gradually increased with the increase of applied load. On the contrary, the deflection of concrete beam tended to be stable with the increase of applied load. When the applied load was the same, the deflection of concrete beams gradually decreased with the increase of eccentricity, the number of circular tendons in composite tendons and concrete strength, and gradually increased with the increase of counterweight
Research on the ultrasonic testing of defect for LY12 aluminum alloy based on transmission wave in lamb wave
Get PDFAimed at the problem that the ultrasonic testing is applied in defect of LY12 aluminum alloy by using liquid or semi-solid coupling agent, transfer matrix method and gas-solid boundary conditions of ultrasonic wave propagation is used for establishing mathematic model in LY12 aluminum alloy, and this model is solved to obtain the propagation characteristic curve. When cut-off frequency is less than 2 MHz·mm, it has only S0 modal. The simulation result provides proper parameters for ultrasonic testing, in which the incidence angle is 30° and the center frequency is 1 MHz. The different circuit defect for LY12 aluminum alloy is made and detected, and time domain waveform is obtained. The experimental results show that the diameter of the defects has a little influence on the amplitude of the direct wave, defect wave amplitude decreases gradually with the increase of the defect diameter
Numerical simulation on structural safety and dynamic response of coal mine rescue ball with gas explosion load using Arbitrary Lagrangian-Eulerian (ALE) algorithm
Get PDFCoal mine rescue devices, which can supply miners underground with fundamental shelters after gas explosion, are essential for safety production of coal mines. In this paper, a novel and composite structure-rescue antiknock ball for coal mine rescue is designed. Further, the structural safety and dynamic response under gas explosion of the antiknock ball is investigated by ALE algorithm. To achieve this goal, the ALE finite element method is described in dynamic form, and governing equations and the finite element expressions of the ALE algorithm are derived. 3 balls with different structures are designed and dynamic response analysis has been conducted in a semi-closed tunnel with explosive load of pre-mixed gas/air mixture by using ALE algorithm based on explicit nonlinear dynamic program LS-DYNA. Displacement field, stress field and energy transmission laws are analyzed and compared via theoretical calculations. Results show that the cabin door, emergency door and spherical shell are important components of the rescue ball. The 3# composite ball is the optimization structure that can delay the shock effect of the gas explosion load on a coal mine rescue system; the simulation results can provide reference data for coal mine rescue system design