bluuebunny/crossref_metadata_2025 huggingface dataset:
An Experimental Technique for the Evaluation of Strain Dependent Material Properties of Hard Coatings
Authors: Reed Shad A. , Palazotto Anthony N. , Baker William P.
Published: January 2014

A novel vibration experiment consisting of a free‐free boundary condition, an electromagnetic excitation source, a vacuum chamber, and a laser vibrometer based surface measurement system has been developed that permits high levels of excitation on highly damped specimens with a minimal amount of unwanted systematic error. While some of the aspects of this experiment are not unique, when combined with a processing technique that accounts for the nonlinearities present in the system, this experiment permits, accurate measurement of strain dependent stiffness and damping properties of hard coatings at high strain levels. This procedure has been demonstrated using a titanium beam that has been coated with a free‐layer damping treatment of Magnesium Aluminate Spinel. The results indicate that Magnesium Aluminate Spinel has both nonlinear stiffness and damping properties. The stiffness asymptotes to a minimum value around 650 microstrain while the damping is a maximum around 100 microstrain. Additionally, the data contained herein cover a larger strain range for this material than previously reported.
Asymmetric Vibration of Polar Orthotropic Annular Circular Plates of Quadratically Varying Thickness with Same Boundary Conditions
Authors: Bhardwaj N. , Gupta A.P. , Choong K.K.
Published: January 2014

In the present paper, asymmetric vibration of polar orthotropic annular circular plates of quadratically varying thickness resting on Winkler elastic foundation is studied by using boundary characteristic orthonormal polynomials in Rayleigh‐Ritz method. Convergence of the results is tested and comparison is made with results already available in the existing literature. Numerical results for the first ten frequencies for various values of parameters describing width of annular plate, thickness profile, material orthotropy and foundation constant for all three possible combinations of clamped, simply supported and free edge conditions are shown and discussed. It is found that (a) higher elastic property in circumferential direction leads to higher stiffness against lateral vibration; (b) Lateral vibration characteristics of F-Fplates is more sensitive towards parametric changes in material orthotropy and foundation stiffness than C-C and S-Splates; (c) Effect of quadratical thickness variation on fundamental frequency is more significant in cases of C-C and S-S plates than that of F-Fplates. Thickness profile which is convex relative to plate center‐line tends to result in higher stiffness of annular plates against lateral vibration than the one which is concave and (d) Fundamental mode of vibration of C-C and S-Splates is axisymmetrical while that of F-Fplates is asymmetrical.
Suppression of Vibration Using Passive Receptance Method with Constrained Minimization
Authors: Tursun Murat , Eşkinat Eşref
Published: January 2014

Structural vibration analysis is used to suppress unwanted vibrations in many areas such as aerospace engineering, manufacturing, defense, automotive, etc. As a result of suppressing the unwanted vibration, the quality of the product is improved. Focusing on the minimization of the vibration amplitudes via a concept of receptance, a new and efficient method for calculating the receptance of a translational mass‐spring‐damper system with N masses and M absorbers (where N and M are any positive integer) is developed. The receptance of the combined system, in terms of the parameters of the main and absorber systems is derived, separately. The optimal parameters of the absorbers are then found. A methodology is derived using dynamic stiffness and linear graph representation in order to verify the dynamic stiffness, i.e., the inverse of the receptance, of the system.
Patterns of Semantic Memory Impairment in Mild Cognitive Impairment
Authors: Joubert Sven , Felician Olivier , Barbeau Emmanuel J. , Didic Mira , Poncet Michel , Ceccaldi Mathieu
Published: January 2014

Although the semantic memory impairment has been largely documented in Alzheimer′s disease, little is known about semantic memory in the preclinical phase of the disease (Mild Cognitive Impairment). The purpose of this study was to document the nature of semantic breakdown using a battery of tests assessing different aspects of conceptual knowledge: knowledge about common objects, famous people and famous public events. Results indicate that all domains of semantic memory were impaired in MCI individuals but knowledge about famous people and famous events was affected to a greater extent than knowledge about objects. This pattern of results suggests that conceptual entities with distinctive and unique properties may be more prone to semantic breakdown in MCI. In summary, results of this study support the view that genuine semantic deficits are present in MCI. It could be useful to investigate the etiological outcome of patients failing or succeeding at such tests.
Lessons Learned in Applying Accelerometers to Nuclear Effects Testing
Authors: Walter Patrick L.
Published: January 2014

Exoatmospheric nuclear effects, such as those that would be encounter by reentry bodies, provide instantaneous (near zero‐duration), impulsive loading of structures. Endoatmospheric nuclear effects possess an impulse that is finite in duration, but whose rise time is still instantaneous. The commonality of these loadings is that they initiate waves propagating through structures, resulting in extremely short duration accelerations to free surfaces where accelerometers are mounted. Over the years, attempts have been made to measure free surface accelerations using ceramic, quartz, and piezoresistive accelerometers. This paper describes the lessons learned, and looks to the future. It also provides a history of shock accelerometer development.
Vibration of Clamped Visco‐Elastic Rectangular Plate with Parabolic Thickness Variations
Authors: Gupta A.K. , Khanna Anupam
Published: January 2014

Most of the machines and engineering structures experience vibration and their design generally requires consideration for their dynamic behavior. Due to this, the study of vibration, as it deals with the vibratory behavior of bodies, is acquiring increasingly importance in several engineering applications, nuclear reactor technology and aeronautical field etc. Most of the work has been done in the field of elastic and non‐elastic behavior of the bodies but a very little work is done in the field of visco‐elastic bodies with varying thickness. The analysis presented here is to study the effect of taper constants on free vibration of a clamped visco‐elastic rectangular plate with parabolically varying thickness. The two‐dimensional thickness variation is taken as the Cartesian product of parabolic variations along the two concurrent edges of the plate. Using Rayleigh‐Ritz method, frequency equation derives. Logarithmic decrement, time period and deflection for the first two modes of vibration are calculated for various values of taper constants and aspect ratio.
Subspace‐Based Identification of Nonlinear Structures
Authors: Marchesiello S. , Garibaldi L.
Published: January 2014

Conventional linear estimators give results contaminated in presence of nonlinearities and the extraction of underlying linear system properties is thus difficult. To overcome this problem, the implementation of a recently developed method, called Nonlinear Subspace Identification (NSI), is considered in this paper, by using the perspective of nonlinearities as unmeasured internal feedback forces. Although its formulation is very simple, particular care has to be taken to reduce the ill‐conditioning of the problem, in order to find numerically stable solutions. To this purpose, the robustness and the high numerical performances of the subspace algorithms are successfully exploited, as shown by the implementation of the proposed method on simulated multi‐degree‐of‐freedom systems with typical nonlinear characteristics as well as on an experimental case. These examples demonstrate that the application of subspace algorithms to nonlinear system identification gives better conditioning and computational efficiency with respect to the most recent nonlinear techniques. Moreover, the capability of the NSI method of simultaneously dealing with several nonlinear terms, with a light computational effort, may be also exploited in those situations where no a priori knowledge of the location and the type of nonlinearities is given, being this method well capable of detecting the contribution of the dominant nonlinearities.

On the basis of the results discussed in this paper, and compared with those of other well‐assessed nonlinear techniques, the proposed method appears having the chances to become a robust procedure to be widely exploited in many industrial fields, being its capability of separating linear and nonlinear contribution terms widely requested in mechanical and civil engineering field.
Age‐Related Quantitative and Qualitative Changes in Decision Making Ability
Authors: Isella Valeria , Mapelli Cristina , Morielli Nadia , Pelati Oriana , Franceschi Massimo , Appollonio Ildebrando Marco
Published: January 2014

The “frontal aging hypothesis” predicts that brain senescence affects predominantly the prefrontal regions. Preliminary evidence has recently been gathered in favour of an age‐related change in a typically frontal process, i.e. decision making, using the Iowa Gambling Task (IGT), but overall findings have been conflicting. Following the traditional scoring method, coupled with a qualitative analysis, in the present study we compared IGT performance of 40 young (mean age: 27.9 ± 4.7) and 40 old (mean age: 65.4 ± 8.6) healthy adults and of 18 patients affected by frontal lobe dementia of mild severity (mean age: 65.1 ± 7.4, mean MMSE score: 24.1 ± 3.9). Quantitative findings support the notion that decision making ability declines with age; moreover, it approximates the impairment observed in executive dysfunction due to neurodegeneration. Results of the qualitative analysis did not reach statistical significance for the motivational and learning decision making components considered, but approached significance for the attentional component for elderly versus young normals, suggesting a possible decrease in the ability to maintain sustained attention during complex and prolonged tasks as the putative deficit underlying impaired decision making in normal aging.
Crossed Aphasia and Visuo‐Spatial Neglect Following a Right Thalamic Stroke: A Case Study and Review of the Literature
Authors: De Witte Lieve , Verhoeven Jo , Engelborghs Sebastiaan , De Deyn Peter P. , Mariën Peter
Published: January 2014

Crossed aphasia in dextrals (CAD) following pure subcortical lesions is rare. This study describes a right‐handed patient with an ischemic lesion in the right thalamus. In the post‐acute phase of the stroke, a unique combination of ‘crossed thalamic aphasia’ was found with left visuo‐spatial neglect and constructional apraxia. On the basis of the criteria used in Mariën et al. [67], this case‐report is the first reliable representative of vascular CAD following an isolated lesion in the right thalamus. Furthermore, this paper presents a detailed analysis of linguistic and cognitive impairments of ‘possible’ and ′reliable′ subcortical CAD‐cases published since 1975. Out of 25 patients with a pure subcortical lesion, nine cases were considered as ‘possibly reliable or reliable’. A review of these cases reveals that: (1) demographic data are consistent with the general findings for the entire group of vascular CAD, (2) the neurolinguistic findings do not support the data in the general CAD‐population with regard to (a) the high prevalence of transcortical aphasia and (b) the tendency towards a copresence of an oral versus written language dissociation and a ‘mirror‐image’ lesion‐aphasia profile, (3) subcortical CAD is not a transient phenomenon, (4) the lesion‐aphasia correlations are not congruent with the high incidence of anomalous cases in the general CAD‐population, (5) neuropsychological impairments may accompany subcortical CAD.
An Updating Method for Structural Dynamics Models with Uncertainties
Authors: Faverjon B. , Ladevèze P. , Louf F.
Published: January 2014

One challenge in the numerical simulation of industrial structures is model validation based on experimental data. Among the indirect or parametric methods available, one is based on the “mechanical” concept of constitutive relation error estimator introduced in order to quantify the quality of finite element analyses. In the case of uncertain measurements obtained from a family of quasi‐identical structures, parameters need to be modeled randomly. In this paper, we consider the case of a damped structure modeled with stochastic variables. Polynomial chaos expansion and reduced bases are used to solve the stochastic problems involved in the calculation of the error.
Psychophysiology and Imaging of Visual Cortical Functions in the Blind: A Review
Authors: Simon-Dack Stephanie L. , Rodriguez P. Dennis , Teder-Sälejärvi Wolfgang A.
Published: January 2014

Imaging, transcranial magnetic stimulation, and psychophysiological recordings of the congenitally blind have confirmed functional activation of the visual cortex but have not extensively explained the functional significance of these activation patterns in detail. This review systematically examines research on the role of the visual cortex in processing spatial and non-visual information, highlighting research on individuals with early and late onset blindness. Here, we concentrate on the methods utilized in studying visual cortical activation in early blind participants, including positron emissions tomography (PET), functional magnetic resonance imaging (fMRI), transcranial magnetic stimulation (TMS), and electrophysiological data, specifically event-related potentials (ERPs). This paper summarizes and discusses findings of these studies. We hypothesize how mechanisms of cortical plasticity are expressed in congenitally in comparison to adventitiously blind and short-term visually deprived sighted participants and discuss potential approaches for further investigation of these mechanisms in future research.
Noise Reduction Evaluation of Multi‐Layered Viscoelastic Infinite Cylinder under Acoustical Wave Excitation
Authors: Mofakhami M.R. , Toudeshky H. Hosseini , Hashemi Sh. Hosseini
Published: January 2014

In this paper sound transmission through the multilayered viscoelastic air filled cylinders subjected to the incident acoustic wave is studied using the technique of separation of variables on the basis of linear three dimensional theory of elasticity. The effect of interior acoustic medium on the mode maps (frequency vs geometry) and noise reduction is investigated. The effects of internal absorption and external moving medium on noise reduction are also evaluated. The dynamic viscoelastic properties of the structure are rigorously taken into account with a power law technique that models the viscoelastic damping of the cylinder. A parametric study is also performed for the two layered infinite cylinders to obtain the effect of viscoelastic layer characteristics such as thickness, material type and frequency dependency of viscoelastic properties on the noise reduction. It is shown that using constant and frequency dependent viscoelastic material with high loss factor leads to the uniform noise reduction in the frequency domain. It is also shown that the noise reduction obtained for constant viscoelastic material property is subjected to some errors in the low frequency range with respect to those obtained for the frequency dependent viscoelastic material.

Noise reduction analyses are also performed for the infinite cylinder subjected to the periodic incident wave with uniform and piecewise form.
Clinical Application of Standardized Cognitive Assessment Using fMRI. II. Verbal Fluency
Authors: Allen Mark D. , Fong Alina K.
Published: January 2014

In this study, we describe an fMRI version of the verbal fluency test. This is the second in a series of fMRI adaptations of classical neuropsychological tests, for which normative samples of functional activation have been collected from unimpaired control subjects and structured in a manner that makes individual patient evaluation possible in terms of familiar z-score distributions. This fMRI protocol is shown to have strong convergent validity with the FAS phonemic fluency test and to elicit activation patterns highly consistent with a large body of previous neuroimaging studies of verbal fluency. We also present a case study, in which we report concurrent data from a patient with selective deficits in verbal processing, using both conventional neuropsychological and fMRI approaches. These analyses reveal striking correspondences between the deficits present in this patient on cognitive performance tests and the equally selective patterns of deviation present in his fMRI data.
Capgras Syndrome and Unilateral Spatial Neglect in Nonconvulsive Status Epilepticus
Authors: Turtzo L. Christine , Kleinman Jonathan T. , Llinas Rafael H.
Published: January 2014

Nonconvulsive status epilepticus can manifest as personality changes and psychosis. We report an 87-year-old right-handed male presenting with both Capgras syndrome and severe unilateral spatial neglect during nonconvulsive status epilepticus. After treatment of his seizures, his Capgras syndrome and hemispatial neglect resolved. This case illustrates a report of the confluence of Capgras syndrome and documented hemispatial neglect in nonconvulsive status epilepticus only reported once previously [1].
A Spectral Finite Element Model for Vibration Analysis of a Beam Based on General Higher‐Order Theory
Authors: Sujuan Jiao , Jun Li , Hongxing Hua , Rongying Shen
Published: January 2014

The spectral element matrix is derived for a straight and uniform beam element having an arbitrary cross‐section. The general higher‐order beam theory is used, which accurately accounts for the transverse shear deformation out of the cross‐sectional plane and antielastic‐type deformation within the cross‐sectional plane. Two coupled equations of motion are derived by use of Hamilton′s principle along with the full three‐dimensional constitutive relations. The theoretical expressions of the spectral element matrix are formulated from the exact solutions of the coupled governing equations. The developed spectral element matrix is directly applied to calculate the exact natural frequencies and mode shapes of the illustrative examples. Numerical results of the thick isotropic beams with rectangular and elliptical cross‐sections are presented for a wide variety of cross‐section aspect ratios.
The Use of Virtual Environments for Survey Spatial Ability Evaluation in Topographical Disorientation
Authors: Morganti Francesca , Rusconi Maria Luisa , Paladino Anna , Geminiani Giuliano , Carassa Antonella
Published: January 2014

Due to their interactivity and to the sense of presence they afford, virtual environments constitute an interesting opportunity to study spatial cognition. In accordance with this perspective, we aimed to introduce a spatial test in virtual simulation in order to investigate the survey spatial ability in patients with topographical disorientation. To do this, we used the “planning in advance task” in a virtual environment that constitutes an effective procedure to experimentally evaluate survey maps. With this procedure we present the single case of a woman, with a right medial temporal lobe lesion, who shows a selective impairment in the acquisition of new spatial relationships. The patient’s performance in “planning in advance task” was compared with that of a control group made up of 40 female subjects matched for age and education. Results show how the patient revealed a significantly lower spatial performance when compared to the control group, demonstrating an inability to solve survey‐type spatial tasks in complex virtual environments.
Geometrical Nonlinear Aeroelastic Stability Analysis of a Composite High‐Aspect‐Ratio Wing
Authors: Xie Chang Chuan , Leng Jia Zhen , Yang Chao
Published: January 2014

A composite high‐aspect‐ratio wing of a high‐altitude long‐endurance (HALE) aircraft was modeled with FEM by MSC/NASTRAN, and the nonlinear static equilibrium state is calculated under design load with follower force effect, but without load redistribution. Assuming the little vibration amplitude of the wing around the static equilibrium state, the system is linearized and the natural frequencies and mode shapes of the deformed structure are obtained. Planar doublet lattice method is used to calculate unsteady aerodynamics in frequency domain ignoring the bending effect of the deflected wing. And then, the aeroelastic stability analysis of the system under a given load condition is successively carried out. Comparing with the linear results, the nonlinear displacement of the wing tip is higher. The results indicate that the critical nonlinear flutter is of the flap/chordwise bending type because of the chordwise bending having quite a large torsion component, with low critical speed and slowly growing damping, which dose not appear in the linear analysis. Furthermore, it is shown that the variation of the nonlinear flutter speed depends on the scale of the load and on the chordwise bending frequency. The research work indicates that, for the very flexible HALE aircraft, the nonlinear aeroelastic stability is very important, and should be considered in the design progress. Using present FEM software as the structure solver (e.g. MSC/NASTRAN), and the unsteady aerodynamic code, the nonlinear aeroelastic stability margin of a complex system other than a simple beam model can be determined.
Prognosis under Uncertainty – An Idealised Computational Case Study
Authors: Worden Keith , Manson Graeme
Published: January 2014

The object of this paper is to investigate computationally the possibility of damage prognosis in a structure under the most idealised circumstances. A simple isotropic material – Titanium alloy Ti‐6Al‐4V – is assumed. The structure is a simple finite plate under harmonic uniaxial loading and the damage is assumed to be a central mode 1 through crack for which various approximations to the stress intensity factor are known. The damage propagation model is the Paris‐Erdogan law. Where the paper departs from complete simplicity is in the assumption that the parameters of the damage propagation law are uncertain. The paper investigates the effect of the parameter uncertainty on the estimated lifetime of the specimen. Two approaches are adopted for the uncertainty propagation, a statistical Monte Carlo scheme and one based on interval arithmetic.
Accurate Reaching after Active But Not Passive Movements of the Hand: Evidence for Forward Modeling
Authors: Coslett H. Branch , Buxbaum Laurel J. , Schwoebel John
Published: January 2014

Converging behavioral findings support recent models of motor control suggesting that estimates of the future positions of a limb as well as the expected sensory consequences of a planned movement may be derived, in part, from efference copies of motor commands. These estimates are referred to as forward models. However, relatively little behavioral evidence has been obtained for proposed forward models that provide on‐line estimates of current position. We report data from a patient (JD) who reached accurately to visualized targets with and without vision of her hand despite substantial proprioceptive loss. Additionally, we administered a double‐start reaching test to examine the possibility that efference copy information could be used to estimate current limb position. JD reached accurately, without vision, to a final target after actively reaching to a landmark, but exhibited severely impaired reaching after passive movements to the landmark. This finding suggests that forward modeling of efference copy signals may provide relatively accurate estimates of current limb position for the purpose of motor planning. The possibility that such estimates may also contribute to the awareness of body position and to self‐recognition is discussed.
Constrained Balancing of Two Industrial Rotor Systems: Least Squares and Min-Max Approaches
Authors: Huang Bin , Fujimura Daiki , Allaire Paul , Lin Zongli , Li Guoxin
Published: January 2014

Rotor vibrations caused by rotor mass unbalance distributions are a major source of maintenance problems in high-speed rotating machinery. Minimizing this vibration by balancing under practical constraints is quite important to industry. This paper considers balancing of two large industrial rotor systems by constrained least squares and min-max balancing methods. In current industrial practice, the weighted least squares method has been utilized to minimize rotor vibrations for many years. One of its disadvantages is that it cannot guarantee that the maximum value of vibration is below a specified value. To achieve better balancing performance, the min-max balancing method utilizing the Second Order Cone Programming (SOCP) with the maximum correction weight constraint, the maximum residual response constraint as well as the weight splitting constraint has been utilized for effective balancing. The min-max balancing method can guarantee a maximum residual vibration value below an optimum value and is shown by simulation to significantly outperform the weighted least squares method.
Design Optimization for Vibration Reduction of Viscoelastic Damped Structures Using Genetic Algorithms
Authors: Xie Zhengchao , Steve Shepard Jr. W. , Woodbury Keith A.
Published: January 2014

Due to the large number of design variables that can be present in complex systems incorporating visco-elastic damping, this work examines the application of genetic algorithms in optimizing the response of these structures. To demonstrate the applicability of genetic algorithms (GAs), the approach is applied to a simple viscoelastically damped constrained-layer beam. To that end, a finite element model (FEM) derived by Zapfe, which was based on Rao's formulation, was used for a beam with constrained-layer damping. Then, a genetic algorithm is applied to simultaneously determine the thicknesses of the viscoelastic damping layer and the constraining layer that provide the best response. While the targeted response is ultimately at the discretion of the designer, a few different choices for the fitness function are shown along with their corresponding impact on the vibratory response. By integrating the FEM code within the GA routine, it is easier to include the frequency-dependence of both the shear modulus and the loss factors for the viscoelastic layer. Examples are provided to demonstrate the capabilities of the method. It is shown that while a multi-mode optimization target provides significant reductions, the response for that configuration is inferior to the response when only single-mode reduction is considered. The results also reveal that the optimum configuration has a lower response level than when a thick layer of damping material is used. By demonstrating the applicability of GA for a simple beam structure, the approach can be extended to more complex damped structures.
Analysis of Switched-Rigid Floating Oscillator
Authors: Marur Prabhakar R.
Published: January 2014

In explicit finite element simulations, a technique called deformable-to-rigid (D2R) switching is used routinely to reduce the computation time. Using the D2R option, the deformable parts in the model can be switched to rigid and reverted back to deformable when needed during the analysis. The time of activation of D2R however influences the overall dynamics of the system being analyzed. In this paper, a theoretical basis for the selection of time of rigid switching based on system energy is established. A floating oscillator problem is investigated for this purpose and closed-form analytical expressions are derived for different phases in rigid switching. The analytical expressions are validated by comparing the theoretical results with numerical computations.
Repetitive Identification of Structural Systems Using a Nonlinear Model Parameter Refinement Approach
Authors: Lin Jeng-Wen , Chen Hung-Jen
Published: January 2014

This paper proposes a statistical confidence interval based nonlinear model parameter refinement approach for the health monitoring of structural systems subjected to seismic excitations. The developed model refinement approach uses the 95% confidence interval of the estimated structural parameters to determine their statistical significance in a least-squares regression setting. When the parameters' confidence interval covers the zero value, it is statistically sustainable to truncate such parameters. The remaining parameters will repetitively undergo such parameter sifting process for model refinement until all the parameters' statistical significance cannot be further improved. This newly developed model refinement approach is implemented for the series models of multivariable polynomial expansions: the linear, the Taylor series, and the power series model, leading to a more accurate identification as well as a more controllable design for system vibration control. Because the statistical regression based model refinement approach is intrinsically used to process a “batch” of data and obtain an ensemble average estimation such as the structural stiffness, the Kalman filter and one of its extended versions is introduced to the refined power series model for structural health monitoring.
Minimal-Sensing, Passive Force Identification Techniques for a Composite Structural Missile Component
Authors: Stites Nick , White Jonathan , Adams Douglas E. , Triplett Matt
Published: January 2014

Structural health monitoring systems are often limited to the use of one sensor due to cost, complexity, and weight restrictions. Therefore, there is a need to develop load and damage identification techniques that utilize only one sensor. Two passive force estimation techniques are investigated in this work. The techniques focus on either the shape or the amplitude of the magnitude of the applied force in the frequency domain. Both techniques iteratively reduce an underdetermined set of equations of motion into many overdetermined systems of equations to solve for the force estimates. The techniques are shown to locate and quantify impulsive impacts with over 97% accuracy and non-impulsive impacts with at least 87% accuracy. A filament-wound rocket motor casing is used as a test structure. Impacts not acting at a specific input degree of freedom are also accurately located depending on the distance away from the modeled input degrees of freedom, and damaging impact forces are quantified by making assumptions about the impulsive nature of the applied force.
Numerical and Experimental Study on Integration of Control Actions into the Finite Element Solutions in Smart Structures
Authors: Malgaca L. , Karagülle H.
Published: January 2014

Piezoelectric smart structures can be modeled using commercial finite element packages. Integration of control actions into the finite element model solutions (ICFES) can be done in ANSYS by using parametric design language. Simulation results can be obtained easily in smart structures by this method. In this work, cantilever smart structures consisting of aluminum beams and lead-zirconate-titanate (PZT) patches are considered. Two cases are studied numerically and experimentally in parallel. In the first case, a smart structure with a single PZT patch is used for the free vibration control under an initial tip displacement. In the second case, a smart structure with two PZT patches is used for the forced vibration control under harmonic excitation, where one of the PZT patches is used as vibration generating shaker while the other is used as vibration controlling actuator. For the two cases, modal analyses are done using chirp signals; Control OFF and Control ON responses in the time domain are obtained for various controller gains. A non-contact laser displacement sensor and strain gauges are utilized for the feedback signals. It is observed that all the simulation results agree with the experimental results.
Active Engine Mounting Control Algorithm Using Neural Network
Authors: Darsivan Fadly Jashi , Martono Wahyudi , Faris Waleed F.
Published: January 2014

This paper proposes the application of neural network as a controller to isolate engine vibration in an active engine mounting system. It has been shown that the NARMA-L2 neurocontroller has the ability to reject disturbances from a plant. The disturbance is assumed to be both impulse and sinusoidal disturbances that are induced by the engine. The performance of the neural network controller is compared with conventional PD and PID controllers tuned using Ziegler-Nichols. From the result simulated the neural network controller has shown better ability to isolate the engine vibration than the conventional controllers.
Synchronization of Two Non-Identical Coupled Exciters in a Non-Resonant Vibrating System of Linear Motion. Part I: Theoretical Analysis
Authors: Zhao Chunyu , Zhu Hongtao , Wang Ruizi , Wen Bangchun
Published: January 2014

In this paper an analytical approach is proposed to study the feature of frequency capture of two non-identical coupled exciters in a non-resonant vibrating system. The electromagnetic torque of an induction motor in the quasi-steady-state operation is derived. With the introduction of two perturbation small parameters to average angular velocity of two exciters and their phase difference, we deduce the Equation of Frequency Capture by averaging two motion equations of two exciters over their average period. It converts the synchronization problem of two exciters into that of existence and stability of zero solution for the Equation of Frequency Capture. The conditions of implementing frequency capture and that of stabilizing synchronous operation of two motors have been derived. The concept of torque of frequency capture is proposed to physically explain the peculiarity of self-synchronization of the two exciters. An interesting conclusion is reached that the moments of inertia of the two exciters in the Equation of Frequency Capture reduce and there is a coupling moment of inertia between the two exciters. The reduction of moments of inertia and the coupling moment of inertia have an effect on the stability of synchronous operation.
Optimal Occupant Kinematics and Crash Pulse for Automobile Frontal Impact
Authors: Cheng Zhiqing , Pellettiere Joseph A. , Crandall Jeff R. , Pilkey Walter D.
Published: January 2014

Based on a lumped-parameter model of the occupant-vehicle system, optimal kinematics of the occupant in frontal impact are investigated. It is found that for the minimization of the peak occupant deceleration, the optimal kinematics move the occupant at a constant deceleration. Based on this the optimal vehicle crash pulse is investigated. The optimal crash pulse for passive restraint systems is found to be: a positive impulse at the onset, an immediate plunge followed by a gradual rebound, and finally a positive level period. The relation of the peak occupant deceleration to the impact speed, crash deformation, and vehicle interior rattlespace is established. The optimal crash pulse for active and pre-acting restraint systems is discussed.
Design of an Active Anti-Roll Bar for Off-Road Vehicles
Authors: Gosselin-Brisson S. , Bouazara M. , Richard M.J.
Published: January 2014

This paper presents a comparison of performance between a passive and an active anti-roll bar. Off-road vehicles are subject to large input road motion and appreciable lateral forces, making anti-roll bars desirable. A four DOF linear model is used to represent an independent suspension and to design the controller. For every case the performance is evaluated for severe road input perturbation and lateral acceleration. A method is presented to illustrate the compromise between stability and comfort inherent in passive anti-roll bar selection. This method was used to select a realistic anti-roll bar stiffness. The active anti-roll bar was designed using full state feedback optimal controller. A simplification of the active system is proposed to reduce the number of measurements and eliminate the need for an optimal observer. The results show a superior performance in ride and handling for the active controller in the frequency range of interest. The addition of filters is proposed to maximize controller efficiency and to reduce associated problems.
New Approach for the Analysis of Damped Vibrations of Fractional Oscillators
Authors: Rossikhin Yuriy A. , Shitikova Marina V.
Published: January 2014

The dynamic behavior of linear and nonlinear mechanical oscillators with constitutive equations involving fractional derivatives defined as a fractional power of the operator of conventional time-derivative is considered. Such a definition of the fractional derivative enables one to analyse approximately vibratory regimes of the oscillator without considering the drift of its position of equilibrium. The assumption of small fractional derivative terms allows one to use the method of multiple time scales whereby a comparative analysis of the solutions obtained for different orders of low-level fractional derivatives and nonlinear elastic terms is possible to be carried out. The interrelationship of the fractional parameter (order of the fractional operator) and nonlinearity manifests itself in full measure when orders of the small fractional derivative term and of the cubic nonlinearity entering in the oscillator's constitutive equation coincide.
Power Delivered to Mechanical Systems by Random Vibrations
Authors: Edwards Timothy S.
Published: January 2014

This paper develops deformational response power descriptions of multiple degree-of-freedom systems due to stationary random vibration excitation. Two new concepts are developed. The deformational response power density (DRPD) can be computed when a structure's natural frequencies and modal masses are available. The DRPD shows the spectral content of the deformational power delivered to a specific structure by the stationary, random excitation. This function can be found through a weighted windowing of the power spectrum of the input acceleration excitation. Deformational response input power spectra (DRIPS), similar to the input energy spectrum and shock response spectrum, give the power delivered to single-degree-of-freedom systems as a function of natural frequency. It is shown that the DRIPS is simply a smoothed version of the power spectrum of the input acceleration excitation. The DRIPS gives rise to a useful power-based data smoothing operation.
Modeling of the Archery Bow and Arrow Vibrations
Authors: Zaniewski I.
Published: January 2014

Vibration processes in the compound and open kinematical chain with an external link, as a model of an archery bow and arrow system, are evaluated. A mechanical and mathematical model of bend oscillations of the system during accelerate motion of the external link is proposed. Correlation between longitudinal acceleration and natural frequencies is obtained. There are recommendations regarding determination of virtual forms to study arrow vibrations and buckling. The models and methods have been adapted for realization into the engineering method using well-known mathematical software packages.
Application of SVM and SVD Technique Based on EMD to the Fault Diagnosis of the Rotating Machinery
Authors: Cheng Junsheng , Yu Dejie , Tang Jiashi , Yang Yu
Published: January 2014

Targeting the characteristics that periodic impulses usually occur whilst the rotating machinery exhibits local faults and the limitations of singular value decomposition (SVD) techniques, the SVD technique based on empirical mode decomposition (EMD) is applied to the fault feature extraction of the rotating machinery vibration signals. The EMD method is used to decompose the vibration signal into a number of intrinsic mode functions (IMFs) by which the initial feature vector matrices could be formed automatically. By applying the SVD technique to the initial feature vector matrices, the singular values of matrices could be obtained, which could be used as the fault feature vectors of support vector machines (SVMs) classifier. The analysis results from the gear and roller bearing vibration signals show that the fault diagnosis method based on EMD, SVD and SVM can extract fault features effectively and classify working conditions and fault patterns of gears and roller bearings accurately even when the number of samples is small.
Reliability Analysis of Electronic Equipment Subjected to Shock and Vibration – A Review
Authors: Amy Robin Alastair , Aglietti Guglielmo S. , Richardson Guy
Published: January 2014

Increasingly modern electronic equipment is expected to provide more functionality whilst still being able to withstand shock and vibration loads. The process of reliability prediction has been hampered by the complicated response and failure characteristics of electronic equipment, with the currently available methods being a compromise between accuracy and cost. A process to quickly and confidently predict the reliability of proposed electronic equipment to dynamic loads would greatly benefit industry.

This paper will illustrate the difficulties in predicting electronic equipment reliability, showing why progress has been slow, in addition to the difficulty in making a model that works across a broad range of equipment configurations. The four classes of reliability prediction methods (Handbook, Test data, Field data and Physics of Failure) will be contrasted before addressing the individual methods.

It is pertinent to note that although the majority of failures in electronic equipment are due to thermal issues, this review focuses on shock and vibration induced failures.
Free Vibration of Sandwich Plates and Shells by Using Zig-Zag Function
Authors: Brischetto S. , Carrera E. , Demasi L.
Published: January 2014

This paper analyses the free vibration response of sandwich curved and flat panels by introducing the zig-zag function (—1)kζk(ZZF) in the displacement models of classical and higher order two-dimensional shell theories. The main advantage of ZZF is the introduction of a discontinuity in the first derivative, zig-zag effect, of the displacements distribution with correspondence to the core/faces interfaces. Results including and discarding ZZF are compared. Several values of face-to-core stiffness ratio (FCSR) and geometrical plate/shell parameters have been analyzed. Both fundamental vibration modes and those corresponding to high wave numbers are considered in the analysis. It is concluded that: (1) ZZF is highly recommended in the free vibration analysis of sandwich plates and shells; (2) the use of ZZF makes the error almost independent by FCSR parameter; (3) ZZF is easy to implement and its use should be preferred with respect to other `more cumbersome' refined theories.
Active Noise Control Using a Functional Link Artificial Neural Network with the Simultaneous Perturbation Learning Rule
Authors: Zhou Ya-li , Zhang Qi-zhi , Zhang Tao , Li Xiao-dong , Gan Woon-seng
Published: January 2014

In practical active noise control (ANC) systems, the primary path and the secondary path may be nonlinear and time-varying. It has been reported that the linear techniques used to control such ANC systems exhibit degradation in performance. In addition, the actuators of an ANC system very often have nonminimum-phase response. A linear controller under such situations yields poor performance. A novel functional link artificial neural network (FLANN)-based simultaneous perturbation stochastic approximation (SPSA) algorithm, which functions as a nonlinear mode-free (MF) controller, is proposed in this paper. Computer simulations have been carried out to demonstrate that the proposed algorithm outperforms the standard filtered-x least mean square (FXLMS) algorithm, and performs better than the recently proposed filtered-s least mean square (FSLMS) algorithm when the secondary path is time-varying. This observation implies that the SPSA-based MF controller can eliminate the need of the modeling of the secondary path for the ANC system.
Ride Performance Analysis of Half-Car Model for Semi-Active System Using RMS as Performance Criteria
Authors: Ihsan S.I. , Ahmadian M. , Faris Waleed F. , Blancard E.D.
Published: January 2014

The work aims to study the root mean square (RMS) responses to acceleration input for four state variables: the msvertical acceleration, the mspitch angular acceleration and the front and rear deflections of the suspensions. A half-car two degree-of-freedom model of semi-active control scheme is analyzed and compared with the conventional passive suspension system. Frequency response of the transfer function for the heave, pitch of the sprung mass and suspension deflections are initially compared and then mean square analysis is utilized to see the effect of semi-active scheme. Results indicate that significant improvements were achieved in the sprung mass heave and pitch responses using semi-active control scheme. However results for the rear and front suspension deflection show that there are limiting values of damping coefficient beyond which, the semi-active scheme becomes disadvantageous than the passive system.
Hybrid Secondary Suspension Systems
Authors: Vahdati Nader , Ahmadian Mehdi
Published: January 2014

Passive fluid mounts are used in the fixed wing applications as engine mounts. The passive fluid mount is placed in between the engine and the fuselage to reduce the cabin's structure- borne noise and vibration generated by the engine.

To investigate the benefits of passive fluid mounts used in conjunction with tuned vibration absorbers (TVA), a simple mathematical model is developed. This mathematical model includes the mathematical model of a passive fluid mount, a TVA, and a spring representing the fuselage structure. The simulation results indicate that when passive fluid mounts are used in conjunction with TVAs, an active suspension system behavior is nearly created.
Experimental Investigation of a Novel Blast Wave Mitigation Device
Authors: Su Zhenbi , Peng Wen , Zhang Zhaoyan , Gogos George , Skaggs Reed , Cheeseman Bryan , Yen Chian Fong
Published: January 2014

A novel blast wave mitigation device was investigated experimentally in this paper. The device consists of a piston-cylinder assembly. A shock wave is induced within the cylinder when a blast wave impacts on the piston. The shock wave propagates inside the device and is reflected repeatedly. The shock wave propagation process inside the device lengthens the duration of the force on the base of the device to several orders of magnitude of the duration of the blast wave, while it decreases the maximum pressure over an order of magnitude. Two types of experiments were carried out to study the blast wave mitigation device. The first type of experiments was done with honeycomb structures protected by the blast wave mitigation device. Experimental results show that the device can adequately protect the honeycomb structure. A second type of experiments was done using a Hopkinson bar to measure the pressure transmitted through the blast wave mitigation device. The experimental results agree well with results from a theoretical model.