International Journal of Vehicle Noise and Vibration (9 papers in press)
Free vibration analysis of a cracked elastically supported beam
by Mahieddine Chettah, Rachid Lassoued
Abstract: In this paper, closed-form expressions based on the Rayleigh's method are studied theoretically to evaluate the first two mode shapes and fundamental frequencies of a cracked elastically supported beam. Such a problem has not been very well investigated in the literature. The EulerBernoulli beam theory is employed to model the cracked beam, and the crack is represented as a rotational spring. Some numerical examples are given to illustrate the proposed method and to present the effect of cracks on the natural frequencies and mode shapes of this cracked system. The results are compared with analytical, numerical and previous experimental studies. It is found that the present method is simpler in the application, faster in decreasing the time and cost of computations and shows a good promise for further development as a practical method to minimise the difference between measured and calculated results, also it can be an alternative solution in the case of crack identification for elastically supported beams.
Keywords: cracked beam; elastic bearing; rotational spring; Rayleigh’s method; transfer matrix method.
Diagnosis of bearing defects by variational modes decomposition from vibratory and acoustic emission measurements
by Djamal Zarour, Marc Thomas, Salim Meziani
Abstract: Empirical Modal Decomposition (EMD) may be used for decomposing a time signal into Intrinsic Mode Functions (IMFs), presenting the filtered information from the highest frequency to the lowest one. However, EMD can present problems owing to its sensitivity to noise and mode mixing. To avoid the mode mixing effect, the Ensemble Empirical Mode Decomposition (EEMD) may be used. The principle of the EEMD is to add white noise to the original signal and then average it, IMF by IMF. This method provides improvements over the original method EMD. However, the amplitude of the added noise stays empirical, which makes this method ineffective in some situations. In order to improve the diagnosis of bearing defects, a new method called Variational Mode Decomposition (VMD) is proposed. This research shows an experimental application for the detection of bearing defects at two stages of degradation: at the early stage and at an advanced stage. In this work, a comparative experimental study between vibratory and acoustic emission measurements, analysed by VMD, is carried out. However, the application of this method requires determining the number of significant frequencies (K) and a balancing parameter (α). For this purpose, the Operational Modal Analysis (OMA) and a correlation study are used to determine the required parameters K and α. The results show that both measurements methods work well to detect the bearing frequencies, but the vibration measurement revealed more sensitive for an early detection.
Keywords: variational mode decomposition; empirical mode decomposition; bearing fault; operational modal analysis; vibration; acoustic emission.
Response of functionally graded beams subjected to a moving load and different types of attachment
by Hazem Zibdeh, Ahmad Abu Hannieh
Abstract: This paper develops an analytical solution for the dynamic response of a Euler-Bernoulli functionally graded (FG) beam subjected to a load moving with constant velocity and different types of attachment. The classical beam theory (CBT) is used to derive the equation of motion. The material properties of the beam are considered to vary continuously in the transverse direction according to an exponential model and a power law model. The stress distribution is evaluated and the location of the neutral axis of the FG beam is obtained. Different types of attachment connected to the beam at specific locations are analysed. The effect of using FG materials to enhance the properties of the beam, and hence in decreasing the response of the beam, is made clear. Also, the effect of the restoring force of attachments in reducing the dynamic response of the beam is discussed.
Keywords: forced vibration; functionally graded beams; attachments on beams; moving load.
Noise and vibration suppression of electric power steering systems: a survey
by Mary Freund, Oumar Barry
Abstract: Electric power steering (EPS) systems have become the ideal steering system for most vehicles because of the generated torque assist mechanism making steering easier for drivers. However, EPS systems generate unwanted noise and vibration that can adversely affect the comfort and health of drivers. Numerous studies have been conducted to examine the sources of vibrations. Various isolation techniques including passive, active, or semi-active have been proposed for achieving the best noise and vibration attenuation. Discrete and distributed mathematical models have been employed to predict the dynamic response of EPS systems. This paper presents the state-of-the-art review of mathematical modelling, vibration isolation methods, and optimisation techniques used for improving the design of EPS systems.
Keywords: noise; vibration; isolation; electric power steering; optimisation.
Dynamic study of composite material shaft in high-speed
by Thimothy Harold Gonsalves, G.C. Mohan Kumar, M.R. Ramesh
Abstract: In this work, the composite material shaft in high-speed rotor-bearing systems is analysed to achieve better rotor dynamics along with the effect of internal damping of the composite shaft. The pioneering studies on a rotating composite shaft along with rotating internal damping are revisited to evaluate its effects on rotor dynamics of high-speed rotor-bearing systems. Two practical rotor-bearing systems are selected to study their suitability for composite shaft application where the composite material is used in the cold section while the existing steel alloy is retained in the hot section as well as at the ends. The rotor dynamic analysis shows significant improvements in rotor dynamics of one of the rotor-bearing systems where the first lateral mode changes to desirable rigid mode from flexure mode shape of existing metallic shaft rotor-bearing system. The frequency values of second and third modes also increase above the operating speed, indicating a clear advantage in rotor dynamics.
Keywords: Campbell diagram; composite material shaft; critical speed; external damping; flexural shaft mode; rotor dynamic analysis; rotor dynamic instability; rotor internal damping; unbalance.
An improved narrowband active noise control system without secondary path modelling based on the time domain
by Kuheli Mondal, Saurav Das, Nozomu Hamada, Aminudin Bin Hj. Abu, Saikat Das, Waleed Fekry Faris
Abstract: Various kinds of ANC system are available including FxLMS with secondary path modelling to reduce acoustics noise. However, secondary path modelling causes the problems to increase the complexity of ANC implementation, reduction of performance caused by modelling error and requirement of auxiliary noise for secondary path modelling. The acoustic noise generated is further compounded by using secondary path identification, which makes the system complex. Therefore, several approaches have been proposed for modifying the FxLMS to solve these problems. There are several available ANC algorithms that do not require secondary path estimation. However, some have drawbacks, such as slow convergence and the complexity of the phase shift mechanism. To solve these problems, a novel approach with no secondary path modelling is adopted, in which the adaptation stability is guaranteed by switching the sign of the step size. It is combined with the online tunable delay of the reference signal to significantly improve the adaptation convergence properties of the algorithm. The present study investigates the acoustic noise by the ANC system without secondary path identification. This study gives an insight into the robustness of the proposed ANC system that can annul the engine noise and can increase passenger comfort. A new mathematical modelling has been proposed to reduce the acoustic noise that increases the convergence criteria.
Keywords: ANC; delay LMS; secondary path modelling; time domain; all-pass filtered x LMS.
Vibration testing of vehicle components by fatigue damage spectrum control
by Alexander Steinwolf, Peter Wolfsteiner
Abstract: Random vibration testing with increased kurtosis introduces high peaks into shaker drive signals to simulate land vehicle vibration more accurately or to shorten duration of fatigue damage testing. For the latter, the kurtosis control method must be able to pass high kurtosis values from the generated shaker vibration into the stress response of the tested component. It was verified and confirmed in the paper that the method of phase manipulation based on the analytical relationship between the IFFT phases and kurtosis was capable of doing so if the resonance frequency of the component is known. However, the fatigue damage spectrum model used for evaluation of time-to-failure considers not just one but a number of resonance frequencies constituting a certain test profile which cannot be simulated by the kurtosis control alone. For this purpose, the phase manipulation method was developed further and verified for operational vibrations of a railway vehicle.
Keywords: vibration testing; kurtosis; IFFT phases; fatigue damage spectrum; accelerated lifetime testing.
Fault feature extraction of localised rub-impact fault based on vector-bispectrum and Teager energy operator
by Zhang Chao
Abstract: Bispectrum analysis is able to suppress the Gaussian noise and analyse quadratic phase coupling in the signals more accurately. However, traditional bispectrum has the problem of losing fault information at low frequency, and may not comprehensively reflect nonlinear information of the fault, which leads to weak diagnostic ability, especially for local rub-impact fault. For this reason, a new feature extraction method called vector-bispectrum energy operator is presented in this paper, which adopts vector-bispectrum based on Teager energy operator and is used to obtain the fault feature of local rubbing rotor. The results of the experiment show that the feature of the local rubbing fault extracted by Teager energy operator based vector-bispectrum is very noticeable, and the fault classification through SVM has a high recognition rate.
Keywords: rub rotor; fault feature extraction; high order statistics; bispectrum energy.
Evaluation of vibration characteristics of partially cracked symmetric laminated orthotropic hybrid composite plates
by Ajay Kumar Verma, Pratap B. Deshmukh, Mohan L. Verma
Abstract: The present study is a numerical investigation on the vibration and deflection characteristics of industry-driven carbon-boron/epoxy hybrid laminated composite plate with partial cracking. The effects of laminated stacking sequence, volume fraction and crack length on natural frequency are investigated. The study is carried out using analytical methods such as classical laminated theory, finite element analysis and artificial neural network for trained sets. Validation and comparison of the present work has been made with the work by Khdeir and Librescu on analysis of symmetric cross-ply laminated elastic plates using a higher-order theory, in which buckling and free vibration were considered. In this study, the CCSS boundary condition is used. A very good agreement has been observed between the analytical and finite element analysis results. In this study, the natural frequency and deflection of various stacking configurations, volume fraction and crack length are calculated using the Classic Lamination Theory (CLT), and the calculated data are fitted to an Artificial Neural Network (ANN) model. With the aid of the developed model, robust indices are developed for both fundamental frequency and deflection. The concept of mechanical behaviour is introduced to address both the natural frequency and deflection criteria, with which a design guideline for robust hybrid composites is given. Simulation studies are conducted to demonstrate the validity of the proposed method.
Keywords: vibration; hybrid composite; crack; classical lamination theory; finite element analysis; artificial neural network; Matlab; Ansys.