International Journal of Vehicle Noise and Vibration (7 papers in press)
Vibration analysis of simulated tyre-vehicle system using frequency based substructuring
by Matthew Clontz, Saied Taheri, Reilly Giunta
Abstract: There is a complex relationship between tyre dynamics and the overall ride comfort and noise of a given vehicle. The main source of this complexity is the interaction of the tyre and vehicle subsystems. This interaction is investigated in the present work through an application of frequency-based substructuring techniques to obtain frequency response information for the tyre from a quarter car system. First, these techniques are applied to a simplified, single coupling degree of freedom representation of the quarter car system. Subsequently, the process is repeated for a simulated system containing a rigid ring tyre model. The results show the power of the technique for studying tyre and suspension subsystems as parts of the assembled quarter car system. This process will allow for a more precise estimation of vehicle ride properties without the need to create complex models or test physical models for each tyre-suspension combination.
Keywords: quarter car; frequency based substructuring; decoupling; tyre; suspension; noise; vibration; ride comfort.
Impact identification of traffic flow and road age on traffic noise emission via an approach of relative traffic noise pressure index
by Kai Huang, Liming Dai, Matthew Yao
Abstract: Traffic noise is one of the main sources of societal noise pollution, which is influenced by various factors. Road surface ageing is a major factor to be considered in evaluating the traffic noise generated by vehicles and that created by the interactions between the vehicle tyres and the road surface. In this study, a series of field experiments are conducted on a highway to identify the effects of traffic flow and pavement operation time on traffic noise emission. The traffic noises at different times of day and at the pavements of various operation durations are investigated. Logarithmic functions are established in the investigations to fit the measurements of traffic flow and traffic noise at two measurement sites. An indicator named the relative traffic noise pressure index is proposed for quantitatively evaluating the effects of the road pavement ageing on traffic noise emission. The results of the research indicated that the repaved road surface may effectively reduce the traffic noise level when the operation time of the road surface is relatively short. It is also shown that the relative traffic noise pressure index proposed is an effective measure for evaluating the traffic noise with respect to the traffic flow and road pavement ageing.
Keywords: acoustic measurement; traffic noise; highway pavement; traffic flow; noise mitigation; pavement ageing.
Assessment of gear pit monitoring system based on order analysis
by Mohamed El Morsy
Abstract: A monitoring system is understood as the identification of a machine's condition/faults on the basis of symptoms. Conventional monitoring methods are based on the stationary assumption, thus they are not applicable to the diagnosis of gears working under varying speed. This constraint limits the gear diagnosis to the industrial application expressly for maintenance decisions. In order to extend the conventional diagnostic methods to speed variation cases, an order analysis technique is proposed in this paper. Order analysis method is introduced to extract the harmonic orders of pitted gear from the response signals under variable speed conditions by using a Tach-probe to detect the variation of investigated gear speeds and an accelerometer to collect the vibration signals, the FFT-based analysis is performed in order spectra. Also, order Cepstrum is presented for gear fault diagnosis under steady state operation condition to measure the ability of order analysis as a monitoring technique in different operation conditions. The effectiveness of the proposed methods is demonstrated by real vibration signals collected from the vehicle gearbox, which is tested on the laboratory stand equipped with three dynamometers: the input dynamometer serves as an internal combustion engine, and the output dynamometers introduce the load on the flanges of output joint shafts. Analysed results show that the proposed methods could identify faulty gear effectively and accurately under different operation conditions.
Keywords: gear pit; order analysis; gear faults diagnosis; monitoring system.
Validation of an innovative viscoelastic treatment, integrated on a real vehicle mock-up for the internal vibro-acoustic improvement
by Massimo Viscardi, Maurizio Arena, Daniela Siano, Marco Brandizzi
Abstract: In the modern transport engineering scenario on a large scale, the search for greater interior comfort is more and more a target for all leading industries. Several technological solutions from the aeronautical to the automotive sector, which could allow for ensuring a high level of efficiency and at the same time safeguarding the environment, as well as reducing the manufacturing costs, are under theoretical analysis and experimentation for the achievement of such purposes. The 'vibro-acoustic design' of the current and future means of transport is going to become one of the focal points of the technological and commercial challenges that will involve in the coming years the bigger manufacturing houses on the world stage. These trends and prospects are prompting the exploration for both numerical and experimental tools that can support this new ambitious requirement. In this framework, this paper, following depth broad spectrum investigations, designs and leads the mass production of an innoavative viscoelastic foam to enhance the sound-absorbing performances better than conventional trim treatments. Noise characterisation rational strategies applied to a real vehicle have successfully confirmed the results already reached by laboratory tests on the stand-alone components. After a brief digression on the outcomes achieved in the previous works, in this context particular attention is paid to the trim-layer assembly in view of the integration in the passengers' compartment for the vibro-acoustic qualification.
Keywords: damping; integration; internal comfort; PU measurement; trim treatment.
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.