International Journal of Vehicle Noise and Vibration (11 papers in press)
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.
Effect of car speed on the transmission of vibration through the seat pan and backrest: field study
by Said Grami, Naser Nawayseh, Sadeque Hamdan
Abstract: This study investigates the effect of car speed on the vibration transmitted to the passenger through both the seat pan and backrest. Ten male subjects sat in the front passenger seat of a sedan car and were driven at three different speeds (60, 80 and 100 km/h). During each ride, the vibration dose value (VDV) was measured in the x-, y- and z-directions on the seat pan and at the backrest. The results showed an increase in the VDV in all directions with increasing the car speed. The VDVs at the backrest were found as high as, or even higher than, those measured on the seat depending on the speed and the measurement axis. Hence, it is recommended that vibration in road vehicles be assessed using more than one speed while taking into consideration measurement at the backrest.
Keywords: car speed; transmission of vibration; vibration dose value; backrest.
Three cylinder TGDI+CVT equipped driveline torsional vibration mode study over driveline component inertia/torsional stiffness
by Qian Zhao
Abstract: It is already known how MT equipped driveline torsional modes are distributed and influenced, and that is successfully applied to MT equipped vehicle NVH problem solving. However, it is still marginal for systematic CVT equipped driveline torsional modes sensitivity analysis, hence it is meaningful to establish the CVT driveline torsional vibration mode distribution and sensitivity to driveline component inertia/torsional stiffness. Thus the right driveline component parameters could be predefined from the very start of driveline development or tuned during the refining stage. The aim of this paper is to find out CVT equipped driveline torsional vibration mode sensitivity to driveline component inertia/torsional stiffness and establish rules to tune the driveline torsional vibration modes to mitigate torsional vibration-induced NVH issues.
Keywords: driveline; torsional vibration; CVT; inertia; torsional stiffness; sensitivity study.
Vibration suppression of a car engine frame via tuned vibration Absorber Design
by Jun Wei Sam, Hock Khuen Cheow, Jee-Hou Ho, Hoon Kiat Ng, Ai Bao Chai
Abstract: Whole body vibration degrades passengers ride comfort, which significantly affects their perception towards overall vehicle quality and induces health concerning issues under long term exposure. Motivated by the qualitative perception of whole body vibration experienced by users during vehicle ride, this paper focuses on the vibration characterisation of a car engine frame and proposes a design and implementation of a tuned vibration absorber (TVA) as the vibration attenuation solution in addressing the vertical vibrations, which are most perceived at the idling condition. TVA with frequency intentionally detuned to avoid exciting the second structural resonance throughout the nominal engine idle operating frequency results in a vibration acceleration amplitude reduction of 30.3% at the second order. The result shows that TVA is effective in attenuating tonal vibration at a particular troublesome frequency, such as the second order tonal vibration commonly experienced by conventional inline 4-cylinder engines.
Keywords: vibration analysis; vibration attenuation; tuned vibration absorber.
Time and magnitude dependent masking effects of vehicle's 2 Hz shock-type vibrations on the perception of vehicle's 4.5 Hz longitudinal shock-type vibrations for seated human subjects
by Nils Bulthaupt, Frank Gauterin
Abstract: In the literature there are no known studies regarding temporal masking effects of vehicle's shock-type vibrations. Since shock-type vibrations of different directions of movements, magnitudes and frequencies are acting on the human body while driving a vehicle, temporal masking effects may be relevant when evaluating vehicle's ride comfort. This study investigates temporal post-masking effects of vehicle's 2 Hz shock-type vibrations (masker) on the perception of 4.5 Hz longitudinal shock-type vibrations (test signal) for the seated human body. It was found that post-masking exists for the investigated vibrations. The masking effect is highly dependent on the time gap between masker and test signal: with increasing time gap the masking effect decreases. Furthermore the amount of masking increases with increasing masker magnitude. Both findings are consistent to the findings in psychoacoustics. In addition to that, the masking effect depends on the masker's direction of movement.
Keywords: vehicle's shock-type vibrations; ride comfort; human vibration perception; whole-body vibration; temporal masking effects; forward masking; post-masking; seated human body.
Application of optimized neural networks models in gears and bearings faults diagnosis
by Kaaïs Khoualdia, Elia Hadjadj Aoul, Tarek Khoualdia
Abstract: Gears and bearings are one of the most important machine components in the industrial world and detection of their faults has become a major trend. In the present article, in order to bring a reliable methodology for monitoring and diagnosis of rotating machinery failures, a test rig is implemented. However, to diagnose combined faults of gears and bearings, a monitoring system based on neural network model (NNM), is proposed. To train and test the NNM, the principal high frequency indicators, determined with the collected time domain vibration data, and codes of defects are used respectively as input and output data. A comparison of two learning algorithms, optimised by the Taguchi method, was done to determine the best NNM. Therefore, the proposed method is effective to study other various industrial cases.
Keywords: gear and bearing combined defects; fault vibration analysis; design of experiment; ANN; Taguchi method.
Effects of dampers on piston slapping motion
by Faisal O. Mahroogi, S. Narayan
Abstract: The secondary motion of piston skirt is a key contributor to Noise, Vibration and Harshness (NVH) emissions from an internal combustion engine. Previous works have focused on various mathematical models of this motion. In the present work, an overview of piston secondary motion is discussed. The scope of using a novel indirect method to control this motion is presented that involves use of vibration dampers. With use of suitable dampers a reduction up to the order of 50% was visualised. The discussed methodology can be used to design an optimised profile of skirt in order to control noise and vibrations emitted and hence satisfy customer benchmarks.
Keywords: vehicle noise; vehicle vibration; piston secondary motion; energy absorption.