http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2013 , Hindawi Publishing Corporation . All rights reserved. Tue, 07 May 2013 08:21:13 +0000 http://www.hindawi.com/journals/aav/2013/610407/ The paper describes a stalldetection criterion based on the use of symmetrised dot pattern (SDP) visual waveform analysis and the stallwarning methodology based on a recently developed analysis. The experimental study explores the capability of the SDP technique to detect the stall incipience and evolution in the presence of low signal-to-noise ratios, that is, a noisy working environment. Moreover, the investigation presents a systematic analysis on the probe position’s influence with respect to the fan section. As such, the SDP technique in combination with an acoustic measurement is able to create a visual pattern that one can use to detect stall from potentially any location around the fan/duct system. Stefano Bianchi, Alessandro Corsini, and Anthony G. Sheard Copyright © 2013 Stefano Bianchi et al. All rights reserved. Thu, 18 Apr 2013 12:24:21 +0000 http://www.hindawi.com/journals/aav/2013/841215/ A two-node element is suggested for analyzing the stability and free vibration of Timoshenko beam. Cubic displacement polynomial and quadratic rotational fields are selected for this element. Moreover, it is assumed that shear strain of the element has the constant value. Interpolation functions for displacement field and beam rotation are exactly calculated by employing total beam energy and its stationing to shear strain. By exploiting these interpolation functions, beam elements' stiffness matrix is also examined. Furthermore, geometric stiffness matrix and mass matrix of the proposed element are calculated by writing governing equation on stability and beam free vibration. At last, accuracy and efficiency of proposed element are evaluated through numerical tests. These tests show high accuracy of the element in analyzing beam stability and finding its critical load and free vibration analysis. Abbas Moallemi-Oreh and Mohammad Karkon Copyright © 2013 Abbas Moallemi-Oreh and Mohammad Karkon. All rights reserved. Wed, 27 Mar 2013 17:05:32 +0000 http://www.hindawi.com/journals/aav/2013/876973/ There are controversial requirements involved in developing numerical methodologies in order to compute the flow in industrial fans. The full resolution of turbulence spectrum in such high-Reynolds number flow configurations entails unreasonably expensive computational costs. The authors applied the study to a large unidirectional axial flow fan unit for tunnel ventilation to operate in the forward direction under ambient conditions. This delivered cooling air to the tunnel under routine operation, or hot gases at 400∘C under emergency conditions in the event of a tunnel fire. The simulations were carried out using the open source code OpenFOAM, within which they implemented a very large eddy simulation (VLES) based on one-equation SGS model to solve a transport equation for the modelled (subgrid) turbulent kinetic energy. This subgrid turbulence model improvement is a remedial strategy in VLES of high-Reynolds number industrial flows which are able to tackle the turbulence spectrum’s well-known insufficient resolution. The VLES of the industrial fan permits detecting the unsteady topology of the rotor flow. This paper explores the evolution of secondary flow phenomena and speculates on its influence on the actual load capability when operating at peak-pressure condition. Predicted noise emissions, in terms of sound pressure level spectra, are also compared with experimental results and found to agree within the uncertainty of the measurements. Stefano Bianchi, Domenico Borello, Alessandro Corsini, Franco Rispoli, and Anthony G. Sheard Copyright © 2013 Stefano Bianchi et al. All rights reserved. Sun, 24 Mar 2013 11:41:16 +0000 http://www.hindawi.com/journals/aav/2013/487141/ Data from a low pressure air test facility are used to quantify the influence of the acoustic field in the main line on side branch resonance behavior. The main line of diameter = 7.6 cm may accumulate acoustic energy broadcast from a resonating branch of diameter = 1.9 cm ( = 0.25). The side branch resonance amplitude is a strong function of branch position along the main line with the normalized pressure rising to 1.2 in the most favorable branch positions with Strouhal number near 0.3. Large time variation of the side branch and main line resonance amplitude is apparent for most branch positions. A moving window is used on the time history to collect an array of power spectral densities (PSDs). Peak amplitude values from the PSD array are represented in a probability density function (PDF) that provides a repeatable characterization of data from the system. Arthur Ruggles, Eric M. Moore, and Michael Shehane Copyright © 2013 Arthur Ruggles et al. All rights reserved. Tue, 05 Mar 2013 08:57:37 +0000 http://www.hindawi.com/journals/aav/2013/158329/ This paper describes a resonance decay estimation for structural health monitoring in the presence of nonstationary vibrations. In structural health monitoring, the structure's frequency response and resonant decay characteristics are very important for understanding how the structure changes. Cumulative spectral analysis (CSA) estimates the frequency decay by using the impulse response. However, measuring the impulse response of buildings is impractical due to the need to shake the building itself. In a previous study, we reported on system damping monitoring using cumulative harmonic analysis (CHA), which is based on CSA. The current study describes scale model experiments on estimating the hidden resonance decay under non-stationary noise conditions by using CSA for structural condition monitoring. Satoru Goto, Yoshinori Takahashi, and Mikio Tohyama Copyright © 2013 Satoru Goto et al. All rights reserved. Mon, 14 Jan 2013 09:27:27 +0000 http://www.hindawi.com/journals/aav/2013/546120/ Increasing demands on the capabilities of engine thermo-fluid dynamic simulation and the ability to accurately predict both performance and acoustics have led to the development of several approaches, ranging from fully 3D to simplified 1D models. The quasi-3D approach is proposed as a compromise between the time-demanding 3D CFD analysis and the fast 1D approach; it allows to model the acoustics of intake and exhaust system components, used in internal combustion engines, resorting to a 3D network of 0D cells. Due to its 3D nature, the model predicts high-order modes, improving the accuracy at high frequencies with respect to conventional plane-wave approaches. The conservation equations of mass and energy are solved at cell centers, whereas the momentum equation is applied to cell connections including specific source term to account for the of sound-absorbing materials and perforated elements. The quasi-3D approach has been validated by comparing the predicted transmission loss to measured data for a number of standard configurations typical of internal combustion engine exhaust systems: a reverse-flow chamber and series chambers with perforates and resistive material. G. Montenegro, A. Della Torre, A. Onorati, and R. Fairbrother Copyright © 2013 G. Montenegro et al. All rights reserved. Tue, 25 Dec 2012 10:23:06 +0000 http://www.hindawi.com/journals/aav/2012/278082/ This paper describes research involving an in-service failure of a “variable pitch in motion” fan’s blade bearing. Variable pitch in motion fans rotate at a constant speed, with the changing blade angle varying the load. A pitch-change mechanism facilitates the change in blade angle. A blade bearing supports each blade enabling it to rotate. The author observed that as the fan aerodynamic stage loading progressively increased, so did the rate of blade-bearing wear. The reported research addressed two separate, but linked, needs. First, the ongoing need to increase fan pressure development capability required an increase in fan loading. This increase was within the context of an erosive operating regime which systematically reduced fan pressure development capability. The second need was to identify the root cause of blade-bearing failures. The author addressed the linked needs using a computational analysis, improving the rotor inflow aerodynamic characteristics through an analysis of the inlet box and design of inlet guide vanes to control flow nonuniformities at the fan inlet. The results of the improvement facilitated both an increase in fan-pressure-developing capability and identification of the root cause of the blade-bearing failures. A. G. Sheard Copyright © 2012 A. G. Sheard. All rights reserved. Sun, 23 Dec 2012 13:43:37 +0000 http://www.hindawi.com/journals/aav/2012/681787/ Church bell ringing as practised in the UK involves large-amplitude motions of both bell and clapper. A simulation model is developed and validated against experimental measurements. It is shown that the clapper does not hit the bell with a single impact but a long series of bounces, and this has important consequences for the decay profile of the bell vibration. Information relevant to bell-ringers and bell-hangers is collected in a series of design charts derived from the simulation model. These charts can assist in the diagnosis and correction of faults. Arising from the analysis of the bouncing clapper, a more general result is also presented relating to the frequency bandwidth when any structure is excited by a small bouncing impactor, for example an impulse hammer used in vibration testing. J. Woodhouse, J. C. Rene, C. S. Hall, L. T. W. Smith, F. H. King, and J. W. McClenahan Copyright © 2012 J. Woodhouse et al. All rights reserved. Thu, 20 Dec 2012 17:38:26 +0000 http://www.hindawi.com/journals/aav/2012/819725/ Based on the transmission and equilibrium relationship of vibration energy in beam-like structures, the Galerkin weighted residual method was applied to equation discretization. An equivalent transformation of feedback element was suggested to develop the Energy Finite Element model of a composite piezoelectric cantilever beam driven by harmonic excitation on lateral direction, with both systems with and without time delay being studied and the power input estimation of harmonic excitation was discussed for the resolution of Energy Finite Element function. Then the energy density solutions of the piezoelectric coupling beam through Energy Finite Element Method (EFEM) and classical wave theory were compared to verify the EFEM model, which presented a good accordance. Further investigation was undertaken about the influence of control parameters including the feedback gain and arrangement of piezoelectric patches on characteristics of system energy density distribution. Jinhua Xie, Rui Huo, Yanfeng Guan, and Zhen Zhou Copyright © 2012 Jinhua Xie et al. All rights reserved. Tue, 11 Dec 2012 09:06:28 +0000 http://www.hindawi.com/journals/aav/2012/562309/ Tunnel ventilation fans, classically, must have the ability to both supply and extract air from a tunnel system, with the operator's choice dependent on the tunnel ventilation system's operating mode most appropriate at any given point in time. Consequently, tunnel ventilation fans must incorporate a reversible aerodynamic design which limits the maximum fan pressure rise. This paper presents three high pressure reversible fan concepts. These comprise a two-stage counter rotating fan, a single-stage high speed fan, and a two-stage fan with a single motor and impeller on each end of the motor shaft. The authors consider the relative merits of each concept. The third concept offers the most compact fan, transform, silencer, and damper package size. The authors discuss the mechanical design challenges that occur with a two-stage fan with a single motor and impeller on each end of the motor shaft. They present and consider a selected motor bearing arrangement and casing design for maintainability. Finally, the authors present both prototype fan and full-scale package aerodynamic and acoustic performance, before discussing the challenges presented by high temperature certification in accordance with the requirements of EN 12101-3: 2012. A. G. Sheard and K. Daneshkhah Copyright © 2012 A. G. Sheard and K. Daneshkhah. All rights reserved. Thu, 29 Nov 2012 17:20:37 +0000 http://www.hindawi.com/journals/aav/2012/689379/ Compressed air energy is expensive, but common in industrial manufacturing plant. However, a significant part of the generated compressed air energy is lost due to leakage. Best practice requires ongoing leak detection and repair. Leak detection in the ultrasonic frequency range using handheld devices is possible only over short distances as associated high-frequency sound is rapidly attenuated by atmospheric absorption. Pressurized air escaping to ambience also generates frequencies below 20 kHz. In this paper beamforming—a well known method for generating noise maps—is tested as a tool for localization of compressed air leaks at larger distances in the audible frequency range. Advanced beamforming methods in both time domain (broadband) and frequency domain (narrowband) have been implemented in a variety of situations on a laboratory experimental rig with several open blows representing leakage in a noisy environment similar to a factory setting. Based on the results achieved it is concluded that the microphone array approach has the potential to be a robust leak identification tool. The experience gained here can also provide useful guidance to the practitioner. Petr Eret and Craig Meskell Copyright © 2012 Petr Eret and Craig Meskell. All rights reserved. Mon, 19 Nov 2012 07:30:32 +0000 http://www.hindawi.com/journals/aav/2012/507031/ Vibrations of a cylindrical shell composed of three layers of different materials resting on elastic foundations are studied out. This configuration is formed by three layers of material in thickness direction where the inner and outer layers are of isotropic materials and the middle is of functionally graded material. Love shell dynamical equations are considered to describe the vibration problem. The expressions for moduli of the Winkler and Pasternak foundations are combined with the shell dynamical equations. The wave propagation approach is used to solve the present shell problem. A number of comparisons of numerical results are performed to check the validity and accuracy of the present approach. Abdul Ghafar Shah, Aalia Ali, Muhmmad Nawaz Naeem, and Shahid Hussain Arshad Copyright © 2012 Abdul Ghafar Shah et al. All rights reserved. Tue, 13 Nov 2012 13:55:46 +0000 http://www.hindawi.com/journals/aav/2012/253121/ Shutao Xing, Marvin W. Halling, and Qingli Meng Copyright © 2012 Shutao Xing et al. All rights reserved. Wed, 07 Nov 2012 08:19:25 +0000 http://www.hindawi.com/journals/aav/2012/268964/ A beam-type absorber has been known as one of the dynamic vibration absorbers used to suppress excessive vibration of an engineering structure. This paper studies an absorbing beam which is attached through a visco-elastic layer on a primary beam structure. Solutions of the dynamic response are presented at the midspan of the primary and absorbing beams in simply supported edges subjected to a stationary harmonic load. The effect of structural parameters, namely, rigidity ratio, mass ratio, and damping of the layer and the structure as well as the layer stiffness on the response is investigated to reduce the vibration amplitude at the fundamental frequency of the original single primary beam. It is found that this can considerably reduce the amplitude at the corresponding troublesome frequency, but compromised situation should be noted by controlling the structural parameters. The model is also validated with measured data with reasonable agreement. Mothanna Y. Abd, Azma Putra, Nawal A. A. Jalil, and Jamaludin Noorzaei Copyright © 2012 Mothanna Y. Abd et al. All rights reserved. Mon, 05 Nov 2012 14:59:49 +0000 http://www.hindawi.com/journals/aav/2012/532458/ Application of sonar technologies to bottom acoustics study has made significant advances over recent decades. The sonar systems evolved from the simple analog single-beam and single-frequency systems to more sophisticated digital ones. In this paper, a quantified sonar system was applied to detect and quantify the bottom echoes. The increasing of mean diameter is accompanied by a higher backscattering strength. From this study, identification and characterization using sonar is possible. Henry M. Manik Copyright © 2012 Henry M. Manik. All rights reserved. Wed, 10 Oct 2012 07:54:18 +0000 http://www.hindawi.com/journals/aav/2012/473531/ Sound wave scattering by a flexible plate embedded on water surface is considered. Linear acoustics and plate elasticity are assumed. The aim is to assess the effect of the plate’s flexibility on sound scattering and the potential in using that flexibility for this purpose. A combined sound-structure solution is used, which is based on a Fourier transform of the sound field and a finite-difference numerical-solution of the plate’s dynamics. The solution is implemented for a circular plate subject to a perpendicular incoming monochromatic sound wave. A very good agreement is achieved with a finite-difference solution of the sound field. It is shown that the flexibility of the plate dampens its scattered sound wave regardless of the type of the plate’s edge support. A hole in the plate is shown to further scatter the sound wave to form maxima in the near sound field. It is suggested that applying an external oscillatory pressure on the plate can reduce significantly and even eliminate its scattered wave, thus making the plate close to acoustically invisible. A uniformly distributed external pressure is found capable of achieving that aim as long as the plate is free edged or is not highly acoustically noncompact. Eldad J. Avital, Theodosios Korakianitis, and Touvia Miloh Copyright © 2012 Eldad J. Avital et al. All rights reserved. Sat, 29 Sep 2012 10:38:25 +0000 http://www.hindawi.com/journals/aav/2012/805141/ Structural pounding can cause considerable damage and even lead to collapse of structures. Most research focuses on modeling, parameter investigation, and mitigation approaches. With the development of structural health monitoring, the on-line detection of pounding becomes possible. The detection of pounding can provide useful information of potential damage of structures. This paper proposed using wavelet scalograms of dynamic response to detect pounding and examined the feasibility of this method. Numerical investigations were performed on a pounding system that consisted of a damped single-degree-of-freedom (SDOF) structure and a rigid barrier. Hertz contact model was used to simulate pounding behavior. The responses and pounding forces of the system under harmonic and earthquake excitations were numerically solved. The wavelet scalograms of acceleration responses were used to identify poundings. It was found that the scalograms can indicate the occurrence of pounding and occurrence time very well. The severity of the poundings was also approximately estimated. Experimental studies were carried out, in which shake table tests were conducted on a bridge model that underwent pounding between its different components during ground motion excitation. The wavelet scalograms of the bridge responses indicated pounding occurrence quite well. Hence the conclusions from the numerical studies were verified experimentally. Shutao Xing, Marvin W. Halling, and Qingli Meng Copyright © 2012 Shutao Xing et al. All rights reserved. Sun, 23 Sep 2012 11:38:39 +0000 http://www.hindawi.com/journals/aav/2012/868247/ The paper presents a case history: the acoustical analysis of a rectangular auditorium. The following acoustical parameters were evaluated: early decay time, reverberation time, clarity, definition, and center time. The excitation signal was linear sweep sine and additional analysis was carried out: peak-to-noise ratio, reverberation time for empty and occupied room, standard deviation of acoustical parameters, diffusion, and just noticeable differences analysis. Conclusions about room’s destination and modeling were drawn in the end. Marina Dana Ţopa, Norbert Toma, Botond Sandor Kirei, Ioana Sărăcuţ, and Angelo Farina Copyright © 2012 Marina Dana Ţopa et al. All rights reserved. Thu, 20 Sep 2012 15:16:11 +0000 http://www.hindawi.com/journals/aav/2012/314706/ Early fault detection and diagnosis for medium-speed diesel engines are important to ensure reliable operation throughout the course of their service. This work presents an investigation of the diesel engine combustion-related fault detection capability of crankshaft torsional vibrations. Proposed methodology state the way of early fault detection in the operating six-cylinder diesel engine. The model of six cylinders DI Diesel engine is developed appropriately. As per the earlier work by the same author the torsional vibration amplitudes are used to superimpose the mass and gas torque. Further mass and gas torque analysis is used to detect fault in the operating engine. The DFT of the measured crankshaft’s speed, under steady-state operating conditions at constant load shows significant variation of the amplitude of the lowest major harmonic order. This is valid both for uniform operating and faulty conditions and the lowest harmonic orders may be used to correlate its amplitude to the gas pressure torque and mass torque for a given engine. The amplitudes of the lowest harmonic orders (0.5, 1, and 1.5) of the gas pressure torque and mass torque are used to map the fault. A method capable to detect faulty cylinder of operating Kirloskar diesel engine of SL90 Engine-SL8800TA type is developed, based on the phases of the lowest three harmonic orders. S. H. Gawande, L. G. Navale, M. R. Nandgaonkar, D. S. Butala, and S. Kunamalla Copyright © 2012 S. H. Gawande et al. All rights reserved. Mon, 17 Sep 2012 14:31:02 +0000 http://www.hindawi.com/journals/aav/2012/581769/ Vibration transmission characteristics of a cylindrical shell with a rectangular plate are discussed in this paper by the substructure receptance method. The system is divided into two substructures: the plate and the shell. After finding the theoretical receptance function of each substructure, the coupling equation of the combined system is solved by considering the continuity conditions at the joint between the plate and the shell. The numerical results are compared with the experimental ones to show the validity of the formulation. After that, effects of the plate's parameters on vibration transmission characteristics are discussed. The parameter study shows that it is important to avoid impedance matching for the plate and the shell in the design of suitable structures with low vibration and noise radiation characteristics. Zhimei Zhao, Meiping Sheng, and Yang Yang Copyright © 2012 Zhimei Zhao et al. All rights reserved. Wed, 12 Sep 2012 10:04:17 +0000 http://www.hindawi.com/journals/aav/2012/268595/ A new technique to simulate nonsmooth motions occurring in vibro-impacting continuous systems is proposed. Sticking motions that are encountered during vibro-impact simulation are imposed exactly using a Lagrange multiplier, which represents the normal reaction force between the continuous system and the obstacle. The expression for the Lagrange multiplier is developed in closed form. The developed theory is demonstrated by numerically simulating the forced response of a pinned-pinned beam impacting a point-like rigid obstacle. C. P. Vyasarayani, Sukhpreet Singh Sandhu, and John McPhee Copyright © 2012 C. P. Vyasarayani et al. All rights reserved. Thu, 06 Sep 2012 09:21:32 +0000 http://www.hindawi.com/journals/aav/2012/901547/ Jafar Saniie, Mario Kupnik, and Erdal Oruklu Copyright © 2012 Jafar Saniie et al. All rights reserved. Thu, 06 Sep 2012 08:09:40 +0000 http://www.hindawi.com/journals/aav/2012/402130/ It is not uncommon for modern aquaria to be built with special entertainment areas. There are no known measurements of sound spillover from such entertainment areas into underwater animal exhibits. Entertainment organizations typically prefer to play music for events at 95 and 100 dBA in a ballroom at Georgia Aquarium. Concern over the potential effects of the music and noise on animals in adjacent exhibits inspired an initial project to monitor and compare sound levels in the adjacent underwater exhibits against the typical in-air sound levels of the ballroom. Measured underwater noise levels were compared to modeled levels based on finite element analysis and plane wave transmission loss calculations through the acrylic viewing window. Results were compared with the model to determine how, if at all, the ambient noise level in the Cold Water Quest exhibit changed as a result of music played in the ballroom. Peter M. Scheifele, John Greer Clark, Kristine Sonstrom, Huikwan Kim, Gopu Potty, James H. Miller, and Eric Gaglione Copyright © 2012 Peter M. Scheifele et al. All rights reserved. Tue, 04 Sep 2012 17:12:51 +0000 http://www.hindawi.com/journals/aav/2012/378361/ Palatal clicks are most interesting for human echolocation. Moreover, these sounds are suitable for other acoustic applications due to their regular mathematical properties and reproducibility. Simple and nondestructive techniques, bioinspired by synthetized pulses whose form reproduces the best features of palatal clicks, can be developed. The use of synthetic palatal pulses also allows detailed studies of the real possibilities of acoustic human echolocation without the problems associated with subjective individual differences. These techniques are being applied to the study of wood. As an example, a comparison of the performance of both natural and synthetic human echolocation to identify three different species of wood is presented. The results show that human echolocation has a vast potential. Juan Antonio Martínez Rojas, Santiago Vignote Peña, Jesús Alpuente Hermosilla, Rocío Sánchez Montero, Pablo Luis López Espí, and Isaac Martínez Rojas Copyright © 2012 Juan Antonio Martínez Rojas et al. All rights reserved. Wed, 29 Aug 2012 14:58:27 +0000 http://www.hindawi.com/journals/aav/2012/698737/ Noise control devices such as panels and barriers, when of high efficiency, generally are of difficult acquisition due to high costs turning in many cases their use impracticable, mainly for limited budget small-sized companies. There is a huge requirement for new acoustic materials that have satisfactory performance, not only under acoustic aspect but also other relevant ones and are of low cost. Vegetable fibers are an alternative solution when used as panels since they promise satisfactory acoustic absorption, according to previous researches, exist in abundance, and derive from renewable sources. This paper, therefore, reports on the development of panels made from vegetable fibers (coconut, palm, sisal, and açaí), assesses their applicability by various experimental (flammability, odor, fungal growth, and ageing) tests, and characterize them acoustically in terms of their sound absorption coefficients on a scale model reverberant chamber. Acoustic results point out that the aforementioned fiber panels play pretty well the role of a noise control device since they have compatible, and in some cases, higher performance when compared to commercially available conventional materials. Leopoldo Pacheco Bastos, Gustavo da Silva Vieira de Melo, and Newton Sure Soeiro Copyright © 2012 Leopoldo Pacheco Bastos et al. All rights reserved. Wed, 01 Aug 2012 10:50:45 +0000 http://www.hindawi.com/journals/aav/2012/874081/ We consider ultrasonic imaging for the visualization of flaws in a material. Ultrasonic imaging is a powerful nondestructive testing (NDT) tool which assesses material conditions via the detection, localization, and classification of flaws inside a structure. We utilize reflections of ultrasonic signals which occur when encountering different media and interior boundaries. These reflections can be cast as direct paths to the target corresponding to the virtual sensors appearing on the top and bottom side of the target. Some of these virtual sensors constitute a virtual aperture, whereas in others, the aperture changes with the transmitter position. Exploitations of multipath extended virtual array apertures provide enhanced imaging capability beyond the limitation of traditional multisensor approaches. The waveforms observed at the physical as well as the virtual sensors yield additional measurements corresponding to different aspect angles, thus allowing proper multiview imaging of flaws. We derive the wideband point spread functions for dominant multipaths and show that fusion of physical and virtual sensor data improves the flaw perimeter detection and localization performance. The effectiveness of the proposed multipath exploitation approach is demonstrated using real data. Yimin D. Zhang, Xizhong Shen, Ramazan Demirli, and Moeness G. Amin Copyright © 2012 Yimin D. Zhang et al. All rights reserved. Wed, 25 Jul 2012 10:30:29 +0000 http://www.hindawi.com/journals/aav/2012/480473/ A fractional fourier transform (FrFT) based chirplet signal decomposition (FrFT-CSD) algorithm is proposed to analyze ultrasonic signals for NDE applications. Particularly, this method is utilized to isolate dominant chirplet echoes for successive steps in signal decomposition and parameter estimation. FrFT rotates the signal with an optimal transform order. The search of optimal transform order is conducted by determining the highest kurtosis value of the signal in the transformed domain. A simulation study reveals the relationship among the kurtosis, the transform order of FrFT, and the chirp rate parameter in the simulated ultrasonic echoes. Benchmark and ultrasonic experimental data are used to evaluate the FrFT-CSD algorithm. Signal processing results show that FrFT-CSD not only reconstructs signal successfully, but also characterizes echoes and estimates echo parameters accurately. This study has a broad range of applications of importance in signal detection, estimation, and pattern recognition. Yufeng Lu, Alireza Kasaeifard, Erdal Oruklu, and Jafar Saniie Copyright © 2012 Yufeng Lu et al. All rights reserved. Wed, 25 Jul 2012 09:29:46 +0000 http://www.hindawi.com/journals/aav/2012/863061/ In the automotive industry, numerous expensive and time-consuming trials are used to “optimize” the ride and handling performance. Ideally, a reliable virtual prototype is a solution. The practical usage of a model is linked and restricted by the model complexity and reliability. The object of this study is development and analysis of a refined quarter car suspension model, which includes the effect of series stiffness, to estimate the response at higher frequencies; resulting Maxwell's model representation does not allow straightforward calculation of performance parameters. Governing equations of motion are manipulated to calculate the effective stiffness and damping values. State space model is arranged in a novel form to find eigenvalues, which is a unique contribution. Analysis shows the influence of suspension damping and series stiffness on natural frequencies and regions of reduced vibration response. Increase in the suspension damping coefficient beyond optimum values was found to reduce the modal damping and increase the natural frequencies. Instead of carrying out trial simulations during performance optimization for human comfort, an expression is developed for corresponding suspension damping coefficient. The analysis clearly shows the influence of the series stiffness on suspension dynamics and necessity to incorporate the model in performance predictions. A. N. Thite Copyright © 2012 A. N. Thite. All rights reserved. Tue, 24 Jul 2012 09:19:48 +0000 http://www.hindawi.com/journals/aav/2012/283535/ Vibration signals measured from a gearbox are complex multicomponent signals, generated by tooth meshing, gear shaft rotation, gearbox resonance vibration signatures, and a substantial amount of noise. This paper presents a novel scheme for extracting gearbox fault features using adaptive filtering techniques for enhancing condition features, meshing frequency sidebands. A modified least mean square (LMS) algorithm is examined and validated using only one accelerometer, instead of using two accelerometers in traditional arrangement, as the main signal and a desired signal is artificially generated from the measured shaft speed and gear meshing frequencies. The proposed scheme is applied to a signal simulated from gearbox frequencies with a numerous values of step size. Findings confirm that 10−5 step size invariably produces more accurate results and there has been a substantial improvement in signal clarity (better signal-to-noise ratio), which makes meshing frequency sidebands more discernible. The developed scheme is validated via a number of experiments carried out using two-stage helical gearbox for a healthy pair of gears and a pair suffering from a tooth breakage with severity fault 1 (25% tooth removal) and fault 2 (50% tooth removal) under loads (0%, and 80% of the total load). The experimental results show remarkable improvements and enhance gear condition features. This paper illustrates that the new approach offers a more effective way to detect early faults. Ghalib R. Ibrahim and A. Albarbar Copyright © 2012 Ghalib R. Ibrahim and A. Albarbar. All rights reserved. Wed, 18 Jul 2012 15:51:48 +0000 http://www.hindawi.com/journals/aav/2012/957379/ Ultrasonic flaw detection and imaging through reverberant layers are challenging problems owing to the layer-induced reverberations and front surface reflections. These undesired signals present a strong clutter and mask the flaw echoes. In this paper, a subspace-based approach is developed for removing, or significantly reducing, the unwanted reverberations, enabling proper flaw detection and imaging. The technique utilizes a set of independent clutter-only reference measurements of the material through the layer. If these measurements are not available, array measurements of the material with flaws are used instead. The clutter, due to its high strength relative to the flaw reflections, forms a subspace spanned by the eigenvectors corresponding to the dominant eigenvalues of the data covariance matrix. The clutter subspace is estimated and removed using orthogonal subspace projection. The clutter usually occupies multidimension subspace that is dependent on the level of coupling, material inhomogeneity, surface roughness, and the sampling rate of the measurements. When the clutter-only reference is not available, information theoretic techniques are used to estimate the dimension of the clutter subspace so that clutter signals are sufficiently suppressed without distorting the flaw signals. The effectiveness of the proposed approach is demonstrated using simulations and real measurement results. Ramazan Demirli, Moeness G. Amin, Xizhong Shen, and Yimin D. Zhang Copyright © 2012 Ramazan Demirli et al. All rights reserved.