bluuebunny/crossref_metadata_2025 huggingface dataset:
Response of Base‐Isolated Liquid Storage Tanks
Authors: Jadhav M.B. , Jangid R.S.
Published: January 2014

Seismic response of liquid storage tanks isolated by elastomeric bearings and sliding system is investigated under real earthquake ground motions. The continuous liquid mass of the tank is modeled as lumped masses known as sloshing mass, impulsive mass and rigid mass. The coupled differential equations of motion of the system are derived and solved in the incremental form using Newmark′s step‐by‐step method with iterations. The seismic response of isolated tank is studied to investigate the comparative effectiveness of various isolation systems. A parametric study is also carried out to study the effect of important system parameters on the effectiveness of seismic isolation for liquid storage tanks. The various important parameters considered are: (i) aspect ratio of the tank and (ii) the time period of the isolation systems. It was observed that both elastomeric and sliding systems are found to be effective in reducing the earthquake forces of the liquid storage tanks. However, the elastomeric bearing with lead core is found to perform better in comparison to other systems. Further, an approximate model is proposed for evaluation of seismic response of base‐isolated liquid storage tanks. A comparison of the seismic response evaluated by the proposed approximate method and an exact approach is made under different isolation systems and system parameters. It was observed that the proposed approximate analysis provides satisfactory response estimates of the base‐isolated liquid storage tanks under earthquake excitation.
Application of Wave Propagation to Pyroshock Analysis
Authors: Gherlone M. , Lomario D. , Mattone M. , Ruotolo R.
Published: January 2014

Pyroshocks are high frequency transients due to pyrotechnic devices used in aerospace engineering in order to deploy solar arrays and antennae, separate subsystems from the spacecraft or separate the spacecraft itself from the base stage booster; their prediction is usually complex and very time consuming.

The aim of this article is to investigate on the application of the analysis of transmission of waves in elastic media in order to predict the dynamic response to pyroshocks. The work is completed by numerical examples, related to components of common use in the aerospace engineering field, showing the comparison between results obtained by using both MSC‐NASTRAN and this novel application of wave propagation analysis.
Dynamic Behavior of a Railway Wheelset on a Roller Rig versus Tangent Track
Authors: Bosso N. , Gugliotta A. , Somà A.
Published: January 2014

This paper addresses the comparison of dynamic behavior of a wheelset on roller and on rails. The development of equations of kinematics and motion allow to put in evidence the intrinsic differences between the dynamic behavior on rail and on roller. The stylized conical profile approximation of the wheel allows to focus the attention on the differences in creepages definition and in contact point shift due to the roller curvature. The treatise is addressed to a full scale roller and can be extended in the case of scaled roller rig to be applied in the case of the test bench developed for experimental analysis. In the present paper numerical simulation and examples are used to proof the analytical results.
Varieties of Alexia From Fusiform, Posterior Inferior Temporal and Posterior Occipital Gyrus Lesions
Authors: Sakurai Yasuhisa
Published: January 2014

Reading impairments of three alexia patients, two pure alexia and one alexia with agraphia, due to different lesions were examined quantitatively, using Kanji (Japanese morphogram) words, Kana (Japanese phonetic writing) words and Kana nonwords. Kana nonword reading was impaired in all three patients, suggesting that widespread areas in the affected occipital and occipitotemporal cortices were recruited in reading Kana characters (corresponding to European syllables). In addition, the findings in patient 1 (pure alexia for Kanji and Kana from a fusiform and lateral occipital gyri lesion) and patient 2 (pure alexia for Kana from a posterior occipital gyri lesion) suggested that pure alexia could be divided into two types, i.e. ventromedial type in which whole‐word reading, together with letter identification, is primarily impaired because of a disconnection of word‐form images from early visual analysis, and posterior type in which letter identification is cardinally impaired. Another type of alexia, alexia with agraphia for Kanji from a posterior inferior temporal cortex lesion (patient 3), results from deficient whole‐word images of words per se, and thus should be designated “orthographic alexia with agraphia”. To account for these impairments, a weighted dual‐route hypothesis for reading is suggested.
A High Precision Shear Flexible Triangular Element for Vibration of Composite Shells
Authors: Sheikh A.H. , Haldar S. , Sengupta D.
Published: January 2014

A high precision triangular shallow shell element is proposed and it is applied to free vibration analysis of composite and isotropic shells. The Mindlin′s hypothesis is followed to include the effect of shear deformation. The formulation is made in an efficient manner to make the element free from shear locking problem. The element has some internal nodes, which are eliminated through static condensation technique to improve the computational elegance of the element. In the present vibration problem, the implementation of the static condensation became possible with the help of an efficient mass lumping scheme. It is quite interesting that the effect of rotary inertia can be included in the recommended scheme for lumped mass matrix. Numerical examples covering a wide range of problems are solved and the results obtained are compared with the published results in many cases, which show the precision and range of applicability of the proposed element. The performance of the proposed technique for rotary inertia is found to be excellent. Some new results are produced, which may be useful in future research.
Frequency Domain Analysis of Continuous Systems with Viscous Generalized Damping
Authors: Sorrentino S. , Fasana A. , Marchesiello S.
Published: January 2014

This paper deals with the effects of generalized damping distributions on vibrating linear systems. The attention is focused on continuous linear systems with distributed and possibly non‐proportional viscous damping, which are studied in terms of modal analysis, defining and discussing the orthogonality properties of their eigenfunctions.

Exact expressions of the frequency response functions obtained by direct integration of the equations of motion are compared with the analogous formulas based on the superposition of modes. In addition, approximate expressions of the frequency response functions of both continuous and discrete (finite element models) systems in terms of their undamped eigenfunctions/eigenvectors are also considered and discussed.

The presented methods are explained, compared and validated by means of numerical examples on a clamped‐free Euler‐Bernoulli beam.
Identification of the 3D Vibratory Motion of a Rigid Body by Accelerometer Measurements
Authors: Di Puccio Francesca , Forte Paola
Published: January 2014

The identification of the motion of a rigid body by means of linear accelerometers is a problem already investigated by many researchers, but still debated. The optimisation of the number and placement of accelerometers is also another important aspect of the problem. In this study, an experimental procedure is proposed and applied to identify the rigid‐body vibratory motion of the steering wheel of a sporting car, by means of six linear accelerometers. Some numerical simulations for investigating possible errors are also presented.
Development of Laser Rifle Trainer with Full Shot Imitation
Authors: Bansevicius Ramutis , Fedaravicius Algimantas , Ostasevicius Vytautas , Ragulskis Minvydas
Published: January 2014

Laser trainers are effective tools for shot and sportsmen training. However, the majority of trainers have neither realistic recoil nor sound imitation systems. The objective of the development of laser rifle trainer with full shot imitation was to investigate and simulate the recoil of combat weapons under single and serial shooting regimes so that the training weapons could simulate complete recoil and sound imitation.

Theoretical and experimental investigations lead to the development of shot training systems which were successfully implemented in Lithuanian Army combat training facilities. The laser trainers are also equipped with interactive software interface which does not only control and register the process of shooting but also can reproduce the whole set of statistical data, including psychological impact on the rifleman and detection of his training problems. The incorporation of multimedia advances the system up to interactive laser shot trainer in virtual combat reality.
Pathological Laughter as a Symptom of Midbrain Infarction
Authors: Dabby Ron , Watemberg Nathan , Lampl Yair , Eilam Anda , Rapaport Abraham , Sadeh Menachem
Published: January 2014

Pathological laughter is an uncommon symptom usually caused by bilateral, diffuse cerebral lesions. It has rarely been reported in association with isolated cerebral lesions. Midbrain involvement causing pathological laughter is extremely unusual. We describe three patients who developed pathological laughter after midbrain and pontine‐midbrain infarction. In two patients a small infarction in the left paramedian midbrain was detected, whereas the third one sustained a massive bilateral pontine infarction extending to the midbrain. Laughter heralded stroke by one day in one patient and occurred as a delayed phenomenon three months after stroke in another. Pathological laughter ceased within a few days in two patients and was still present at a two year follow‐up in the patient with delayed‐onset laughter. Pathological laughter can herald midbrain infarction or follow stroke either shortly after onset of symptoms or as a delayed phenomenon. Furthermore, small unilateral midbrain infarctions can cause this rare complication.
Effects of Elastic Foundation on the Vibration of Laminated Non‐Homogeneous Orthotropic Circular Cylindrical Shells
Authors: Sofiyev A.H. , Keskin S.N. , Sofiyev Ali H.
Published: January 2014

In this paper an analytical procedure is given to study the free vibration characteristics of laminated non‐homogeneous orthotropic thin circular cylindrical shells resting on elastic foundation, accounting for Karman type geometric non‐linearity. At first, the basic relations and modified Donnell type stability equations, considering finite deformations, have been obtained for laminated thin orthotropic circular cylindrical shells, the Young′s moduli of which varies piecewise continuously in the thickness direction. Applying Galerkin method to the latter equations, a non‐linear time dependent differential equation is obtained for the displacement amplitude. The frequency is obtained from this equation as a function of the shell displacement amplitude. Finally, the effect of elastic foundation, non‐linearity, non‐homogeneity, the number and ordering of layers on the frequency is found for different mode numbers. These results are given in the form of tables and figures. The present analysis is validated by comparing results with those in the literature.
Transmissibility Matrix in Harmonic and Random Processes
Authors: Fontul M. , Ribeiro A.M.R. , Silva J.M.M. , Maia N.M.M.
Published: January 2014

The transmissibility concept may be generalized to multi‐degree‐of‐freedom systems with multiple random excitations. This generalization involves the definition of a transmissibility matrix, relating two sets of responses when the structure is subjected to excitation at a given set of coordinates. Applying such a concept to an experimental example is the easiest way to validate this method.
Wave Propagation in Periodic Shells with Tapered Wall Thickness and Changing Material Properties
Authors: Toso M. , Baz A.
Published: January 2014

A theoretical method based on the Transfer Matrix Formulation and Wavelet Transforms is developed in order to effectively investigate the influence of periodicity, variable geometry and material properties on the wave propagation characteristics of axis‐symmetric shells. Several experiments have been conducted to verify the numerical predictions and to demonstrate that the Wavelet Transform is a very powerful tool to uniquely identify and compare the energy distribution both in the time and frequency domain.

Thin shells are modeled as two‐dimensional wave‐guides, where the propagation of the longitudinal waves is coupled with the flexural (radial) waves. Variations of the wall thickness, medium radius and element length of the shell can effectively filter out/stop undesirable bands of frequencies from the longitudinal and/or the transverse wave characteristics. The principal parameter that influences the width and location of the stop bands is the ratio between the cross sections at the two ends of the shell element. Sophisticated exponential profiles and simpler linear taper are implemented and compared.

Functionally graded materials (FGM) are also investigated as an alternative way to influence the parameters of the stop bands. Combinations of the FGM and geometric taper give the flexibility needed for some very demanding applications. Different types of periodic taper configurations have complementary effects on the wave characteristics. Combinations of these complex geometries (bi-periodic tapered cells) are presented and shown to produce the most effectual energy redistribution.
A Cognitive Neuropsychological and Psychophysiological Investigation of a Patient Who Exhibited an Acute Exacerbated Behavioural Response during Innocuous Somatosensory Stimulation and Movement
Authors: Edelstyn N. M. J. , Baker S. R. , Ellis S. J. , Jenkinson P.
Published: January 2014

We report findings from a cognitive neuropsychological and psychophysiological investigation of a patient who displayed an exacerbated acute emotional expression during movement, innocuous, and aversive somatosensory stimulation. The condition developed in the context of non‐specific white matter ischaemia along with abnormalities in the cortical white matter of the left anterior parietal lobe, and subcortical white matter of the left Sylvian cortex.

Cognitive neuropsychological assessment revealed a pronounced deficiency in executive function, relative to IQ, memory, attention, language and visual processing. Compared to a normal control group, the patient [EQ] displayed a significantly elevated skin conductance level during both innocuous and aversive somatosensory stimulation. His pain tolerance was also significantly reduced. Despite this, EQ remained able to accurately describe the form of stimulation taking place, and to rate the levels of pain intensity and pain affect.

These results suggest that EQ’s exaggerated behavioural response and reduced pain tolerance to somatosensory stimulation may be linked to cognitive changes, possibly related to increased apprehension and fear, rather than altered pain intensity or pain affect per se.
A Single and Double Mode Approach to Chaotic Vibrations of a Cylindrical Shell with Large Deflection
Authors: Dai Liming , Han Qiang , Dong Mingzhe
Published: January 2014

The chaotic vibrations of a cylindrical shell of large deflection subjected to two‐dimensional exertions are studied in the present research. The dynamic nonlinear governing equations of the cylindrical shell are derived on the basis of single and double mode models established. Two different types of nonlinear dynamic equations are obtained with varying dimensions and loading parameters. The criteria for chaos are determined via Melnikov function for the single mode model. The chaotic motion of the cylindrical shell is investigated and the comparison between the single and double mode models is carried out. Results of the research show that the single mode method usually used may lead to incorrect conclusions under certain conditions. Double mode or higher order mode methods should be used in these cases.
A Unified Approach to Substructuring and Structural Modification Problems
Authors: D’Ambrogio Walter , Sestieri Aldo
Published: January 2014

Substructures coupling is still an important tool in several applications of modal analysis, especially structural modification and structures assembling. The subject is particularly relevant in virtual prototyping of complex systems and responds to actual industrial needs. This paper analyzes the possibility of assembling together different substructures′ models. The important role of rotational DoFs is highlighted, underlying the difficulty of assembling theoretical and experimental models, for which, usually, the rotational DoFs are not available. Expansion techniques can be used to provide this information as well as appropriate modelling of joints. With this information FRF models, modal models and FE models can be appropriately combined together and solutions for several cases of practical interest are presented. The analyzed procedures are tested on purpose‐built benchmarks, showing limits and capabilities of each of them.
Assessment of Theories for Free Vibration Analysis of Homogeneous and Multilayered Plates
Authors: Carrera Erasmo
Published: January 2014

This paper assesses classical and advanced theories for free vibrational response of homogeneous and multilayered simply supported plates. Closed form solutions are given for thick and thin geometries. Single layer and multilayered plates made of metallic, composite and piezo‐electric materials, are considered. Classical theories based on Kirchhoff and Reissner‐Mindlin assumptions are compared with refined theories obtained by enhancing the order of the expansion of the displacement fields in the thickness direction z. The effect of the Zig‐Zag form of the displacement distribution in z as well as of the Interlaminar Continuity of transverse shear and normal stresses at the layer interface were evaluated. A number of conclusions have been drawn. These conclusions could be used as desk‐bed in order to choose the most valuable theories for a given problem.
Dynamic Response of Buried Silo Caused by Underground Explosion
Authors: Kobielak Sylwester , Krauthammer Theodor
Published: January 2014

Experimental results of normal and tangential pressures on a buried silo wall caused by buried charge explosions are presented in the paper. The measured pressures depended on the charge mass, and its burial depth and distance from the silo front. Pressures were measured by sensors attached to the silo wall at different depths along to four diametrically opposite line generators located at the front, rear and two sides. The influence of each parameter is analyzed and discussed.
Parkinson’s Disease Protects Against Smoking?
Authors: Allam Mohamed Farouk , Campbell Michael J. , Del Castillo Amparo Serrano , Navajas Rafael Fernández-Crehuet
Published: January 2014

Our aim was to estimate the pooled risk of current and former smoking for Parkinson’s disease (PD).We have reviewed all observational studies that evaluated the association between PD risk and smoking habit. Twenty six studies were identified: 21 case‐control, 4 cohort and 1 cross‐sectional. The cross‐sectional study did not compare former with never smokers. These studies were carried out between 1968 and 2000.

There was an obvious protective effect of current smoking in the pooled estimate [risk estimate 0.37 (95% confidence interval 0.33 to 0.41)]. Former versus never smokers had pooled risk estimate of 0.84 (95% confidence interval 0.76 to 0.92). Current and former smoking do not, therefore, exert the same protective effect against PD so that it is unnecessary to postulate a biological mechanism through which smoking protects against PD. The results show that the reverse direction of causation is a more probable explanation, i.e. movement disorders of PD protect against smoking. Another explanation is that failure to develop strong smoking habits in early adult life might be a prodromal symptom of the disease and could perhaps be its first clinical manifestation.
The PolyMAX Frequency‐Domain Method: A New Standard for Modal Parameter Estimation?
Authors: Peeters Bart , Van der Auweraer Herman , Guillaume Patrick , Leuridan Jan
Published: January 2014

Recently, a new non‐iterative frequency‐domain parameter estimation method was proposed. It is based on a (weighted) least‐squares approach and uses multiple‐input‐multiple‐output frequency response functions as primary data. This so‐called “PolyMAX” or polyreference least‐squares complex frequency‐domain method can be implemented in a very similar way as the industry standard polyreference (time‐domain) least‐squares complex exponential method: in a first step a stabilisation diagram is constructed containing frequency, damping and participation information. Next, the mode shapes are found in a second least‐squares step, based on the user selection of stable poles. One of the specific advantages of the technique lies in the very stable identification of the system poles and participation factors as a function of the specified system order, leading to easy‐to‐interpret stabilisation diagrams. This implies a potential for automating the method and to apply it to “difficult” estimation cases such as high‐order and/or highly damped systems with large modal overlap. Some real‐life automotive and aerospace case studies are discussed. PolyMAX is compared with classical methods concerning stability, accuracy of the estimated modal parameters and quality of the frequency response function synthesis.
A Refined Numerical Simulation on Dynamic Behavior of Roller Chain Drives
Authors: Zheng H. , Wang Y.Y. , Quek K.P.
Published: January 2014

A refined numerical analysis of the dynamic behavior of roller chain drives is performed considering the roller assembly as a three‐layer structure with mechanical clearance between each two of the mechanical components. Instead of using analytical method, explicit finite element technique is utilized for modeling and simulating the dynamic behavior of chain drives. The complete standard geometry of sprockets and all components of chain links are used in the developed model with minor geometry simplification. A primary goal is to achieve a more complete understanding of the dynamic behavior of chain drives especially in the transient vibration response of the engaging rollers, which is crucial for noise emission calculation. The simulated velocity response of the engaging rollers and roller‐sprocket contact forces achieved using the full model are compared with what found by the simple model which has been adopted in analytical study of chain roller dynamics.
New Separation Techniques for Output‐Only Modal Analysis
Authors: Antoni Jérôme , Garibaldi Luigi , Marchesiello Stefano , Sidhamed Menad
Published: January 2014

The paper is devoted to the problem of discriminating between operational and natural modes of structures excited by generic inputs. This case often occurs when the system under analysis holds rotating parts and is contemporary excited by ambient noise; in this case the output‐only techniques may fail being easily trapped in a misinterpretation of the system eigenvalues. A survey of the methods available in literature is given, together with the explanation of their failures. To solve this problem, two new techniques are introduced and their capabilities are checked with numerical and experimental data from a paper machine.
Semi‐Active Friction Damping of Large Space Truss Structures
Authors: Gaul L. , Albrecht H. , Wirnitzer J.
Published: January 2014

The present approach for vibration suppression of flexible structures is based on friction damping in semi‐active joints. At optimal locations conventional rigid connections of a large truss structure are replaced by semi‐active friction joints. Two different concepts for the control of the normal forces in the friction interfaces are implemented. In the first approach each semi‐active joint has its own local feedback controller, whereas the second concept uses a global, clipped‐optimal controller. Simulation results of a 10‐bay truss structure show the potential of the proposed semi‐active concept.
Dynamic Model Updating Using Virtual Antiresonances
Authors: D’Ambrogio Walter , Fregolent Annalisa
Published: January 2014

This paper considers an extension of the model updating method that minimizes the antiresonance error, besides the natural frequency error. By defining virtual antiresonances, this extension allows the use of previously identified modal data. Virtual antiresonances can be evaluated from a truncated modal expansion, and do not correspond to any physical system. The method is applied to the Finite Element model updating of the GARTEUR benchmark, used within an European project on updating. Results are compared with those previously obtained by estimating actual antiresonances after computing low and high frequency residuals, and with results obtained by using the correlation (MAC) between identified and analytical mode shapes.
Decision‐Making Impairments in Patients with Parkinson’s Disease
Authors: Brand Matthias , Labudda Kirsten , Kalbe Elke , Hilker Rüdiger , Emmans David , Fuchs Gerd , Kessler Josef , Markowitsch Hans J.
Published: January 2014

A high percentage of Parkinson’s disease (PD) patients show cognitive impairments in addition to the cardinal motor symptoms. These deficits primarily concern executive functions most probably linked to dysfunctions in prefrontal regions due to decreased dopaminergic transmission in fronto‐striatal loops. To investigate possible associations between decision‐making and executive functions in PD, we examined 20 non‐demented PD patients and 20 healthy control subjects with a neuropsychological test battery and the Game of Dice Task. In this computerised decision‐making task, the rules for gains and losses and the winning probabilities are obvious and stable. Thus, strategic components besides feedback processing might influence decision‐making in this task. We found that PD patients were impaired in the Game of Dice task performance and that the frequency of disadvantageous choices correlated with both executive functions and feedback processing. We suggest that decision‐making deficits of PD patients in explicit gambling situations might be associated with dysfunctions in two different fronto‐striatal loops: the limbic‐orbitofrontal‐striatal loop, involved in feedback processing, and the dorsolateral prefrontal‐striatal loop, involved in executive functions.
Experimental Methods Applied in a Study of Stall Flutter in an Axial Flow Fan
Authors: Gill John D. , Capece Vincent R. , Fost Ronald B.
Published: January 2014

Flutter testing is an integral part of aircraft gas turbine engine development. In typical flutter testing blade mounted sensors in the form of strain gages and casing mounted sensors in the form of light probes (NSMS) are used. Casing mounted sensors have the advantage of being non‐intrusive and can detect the vibratory response of each rotating blade. Other types of casing mounted sensors can also be used to detect flutter of rotating blades. In this investigation casing mounted high frequency response pressure transducers are used to characterize the part‐speed stall flutter response of a single stage unshrouded axial‐flow fan. These dynamic pressure transducers are evenly spaced around the circumference at a constant axial location upstream of the fan blade leading edge plane. The pre‐recorded experimental data at 70% corrected speed is analyzed for the case where the fan is back‐pressured into the stall flutter zone. The experimental data is analyzed using two probe and multi‐probe techniques. The analysis techniques for each method are presented. Results from these two analysis methods indicate that flutter occurred at a frequency of 411 Hz with a dominant nodal diameter of 2. The multi‐probe analysis technique is a valuable method that can be used to investigate the initiation of flutter in turbomachines.
A New Method for Analysis of Complex Structures Based on FRF’s of Substructures
Authors: Liu C.Q. , Liu Xiaobo
Published: January 2014

A new method is presented for synthesizing the dynamic responses of a complex structure based upon the frequency response functions of the substructures. This method is shown to be superior to traditional methods for several reasons: (i) It can be applied to a generic class of systems. (ii) The analyst is spared the responsibilities of eliminating the coupling forces and rearranging the equations of motion. (iii) The coupling forces and the responses of the total system can be obtained simultaneously and efficiently.
Sound Radiation due to Modal Vibrations of a Spherical Source in an Acoustic Quarterspace
Authors: Hasheminejad Seyyed M. , Azarpeyvand Mahdi
Published: January 2014

Radiation of sound from a spherical source, vibrating with an arbitrary, axisymmetric, time‐harmonic surface velocity, while positioned within an acoustic quarterspace is analyzed in an exact manner. The formulation utilizes the appropriate wave field expansions along with the translational addition theorem for spherical wave functions in combination with the classical method of images to develop a closed‐form solution in form of infinite series. The analytical results are illustrated with numerical examples in which the spherical source, vibrating in the pulsating (n = 0) and translational oscillating (n = 1) modes, is positioned near the rigid boundary of a water‐filled quarterspace. Subsequently, the basic acoustic field quantities such as the modal acoustic radiation impedance load and the radiation intensity distribution are evaluated for representative values of the parameters characterizing the system.
Analysis of Vibration and Wave Propagation in Cylindrical Grid‐Like Structures
Authors: Jeong Sang Min , Ruzzene Massimo
Published: January 2014

The wave propagation in and the vibration of cylindrical grid structures are analyzed. The grids are composed of a sequence of identical elementary cells repeating along the axial and the circumferential direction to form a two‐dimensional periodic structure. Two‐dimensional periodic structures are characterized by wave propagation patterns that are strongly frequency dependent and highly directional. Their wave propagation characteristics are determined through the analysis of the dynamic properties of the unit cell. Each cell here is modelled as an assembly of curved beam elements, formulated according to a mixed interpolation method. The combined application of this Finite Element formulation and the theory of two‐dimensional periodic structures is used to generate the phase constant surfaces, which define, for the considered cell lay‐out, the directions of wave propagation at assigned frequencies. In particular, the directions and frequencies corresponding to wave attenuation are evaluated for cells of different size and geometry, in order to identify topologies with attractive wave attenuation and vibration confinement characteristics. The predictions from the analysis of the phase constant surfaces are verified by estimating the forced harmonic response of complete cylindrical grids, obtained through the assembly of the unit cells. The considered analysis provides invaluable guidelines for the investigation of the dynamic properties and for the design of grid stiffened cylindrical shells with unique vibration confinement characteristics.
Parameter Identification of Weakly Nonlinear Vibration System in Frequency Domain
Authors: Peng Jiehua , Tang Jiashi , Chen Zili
Published: January 2014

A new method of identifying parameters of nonlinearly vibrating system in frequency domain is presented in this paper. The problems of parameter identification of the nonlinear dynamic system with nonlinear elastic force or nonlinear damping force are discussed. In the method, the mathematic model of parameter identification is frequency response function. Firstly, by means of perturbation method the frequency response function of weakly nonlinear vibration system is derived. Next, a parameter transformation is made and the frequency response function becomes a linear function of the new parameters. Then, based on this function and with the least square method, physical parameters of the system are identified. Finally, the applicability of the proposed technique is confirmed by numerical simulation.
Non‐Stationary Random Response of MDOF Duffing Systems
Authors: Lin J.H. , Wang J. , Zhang Y.H.
Published: January 2014

This paper presents a method to solve non‐stationary random responses of nonlinear multi‐degrees‐of‐freedom (MDOF) Duffing systems subjected to evolutionary random excitations. Specific phase‐lags between the excitations can also be taken into account. The power spectral density (PSD) of the input excitations is not confined to simple white noise or filtered white noise, in fact it can also take more complicated forms. The MDOF nonlinear random differential equations are iteratively solved by means of the Equivalent Linearization Method (ELM) combined with the Pseudo Excitation Method (PEM). This combined method is easy and efficient. Two examples are given in which this method is well justified by the Monte‐Carlo numerical simulations. Although only a Duffing model is dealt with in this paper for computational simplicity, the proposed method is in fact quite general, e.g. it can also deal with nonlinear hysteretic structures that will be dealt with in a separate paper.
Two‐Stage Stochastic Model on Rattling Vibration with Amplitude Modulation
Authors: Wen Jian Ming , Feng Qi
Published: January 2014

Rattling vibration in gear boxes of automobiles is an annoying problem. It may be generated in those gear wheels of a car transmission system, which are unloaded. In recent years, very general models have been developed to analyze the rattling phenomenon. One of them, in consideration of plays being the consequence of tolerances, backlashes and others, is modeled as an impulsive system that consists of some unloaded gears being able to rattle. Modern research has shown that the chaotic vibration may occur on a rattling system. In this paper, a stochastic modulated rattling system with two‐stage was studied. A discrete stochastic model described by mean map was established using non‐Gaussian technique. By the analysis of the example this model can reveal chaotic stochastic behaviors.
Coupled Bending‐Bending‐Torsion Vibration of a Rotating Pre‐Twisted Beam with Aerofoil Cross‐Section and Flexible Root by Finite Element Method
Authors: Yardimoglu Bulent , Inman Daniel J.
Published: January 2014

The purpose of this paper is to extend a previously published beam model of a turbine blade including the centrifugal force field and root flexibility effects on a finite element model and to demonstrate the performance, accuracy and efficiency of the extended model for computing the natural frequencies. Therefore, only the modifications due to rotation and elastic root are presented in great detail. Considering the shear center effect on the transverse displacements, the geometric stiffness matrix due to the centrifugal force is developed from the geometric strain energy expression based on the large deflections and the increase of torsional stiffness because of the axial stress. In this work, the root flexibility of the blade is idealized by a continuum model unlike the discrete model approach of a combination of translational and rotational elastic springs, as used by other researchers. The cross‐section properties of the fir‐tree root of the blade considered as an example are expressed by assigning proper order polynomial functions similar to cross‐sectional properties of a tapered blade. The correctness of the present extended finite element model is confirmed by the experimental and calculated results available in the literature. Comparisons of the present model results with those in the literature indicate excellent agreement.
Training‐Based Interventions in Motor Rehabilitation after Stroke: Theoretical and Clinical Considerations
Authors: Sterr Annette
Published: January 2014

Basic neuroscience research on brain plasticity, motor learning and recovery has stimulated new concepts in neurological rehabilitation. Combined with the development of set methodological standards in clinical outcome research, these findings have led to a double‐paradigm shift in motor rehabilitation: (a) the move towards evidence‐based procedures for the assessment of clinical outcome & the employment of disablement models to anchor outcome parameters, and (b) the introduction of practice‐based concepts that are derived from testable models that specify treatment mechanisms. In this context, constraint‐induced movement therapy (CIT) has played a catalytic role in taking motor rehabilitation forward into the scientific arena. As a theoretically founded and hypothesis‐driven intervention, CIT research focuses on two main issues. The first issue is the assessment of long‐term clinical benefits in an increasing range of patient groups, and the second issue is the investigation of neuronal and behavioural treatment mechanisms and their interactive contribution to treatment success. These studies are mainly conducted in the research environment and will eventually lead to increased treatment benefits for patients in standard health care. However, gradual but presumably more immediate benefits for patients may be achieved by introducing and testing derivates of the CIT concept that are more compatible with current clinical practice. Here, we summarize the theoretical and empirical issues related to the translation of research‐based CIT work into the clinical context of standard health care.
Dynamic and Acoustic Characterisation of Automotive Wheels
Authors: Curà Francesca , Curti Graziano
Published: January 2014

The subject of this paper is the dynamic and acoustic characterisation of an automotive wheel. In particular, an experimental research activity previously performed by the authors about the dynamic behaviour of automotive wheels has been extended to the acoustic field.

This experimental research has begun in the laboratory of the Mechanics Department of Politecnico di Torino where the modal analysis of the SAAB 640/6Jx15H2 wheel has been carried on step by step, starting from the rim in the most simple constraint condition to realise in laboratory, that is the free‐free condition, up to the wheel (rim with tire) clamped to a real automotive hub; two cases have been considered: the wheel in hanging condition, that is with the vehicle on a lift‐bridge, and the wheel laying on the ground.

Then an acoustic study, analytical, numerical and experimental, of the cavity tire has also been performed. The experimental analysis has been carried on by introducing a microphone in the tire cavity (with no pressure) and by measuring the corresponding response level. The analytical study has been performed by utilising analytical relationships known in literature and a model of the tire cavity with an equivalent geometry. The numerical analysis has been carried on by means of a Boundary Element Method (BEM) model of the cavity.

All obtained results, both dynamic and acoustic, have been analysed and compared to those concerning the experimental tests of the wheel clamped to the vehicle hub.
Optimal Cantilever Dynamic Vibration Absorbers by Timoshenko Beam Theory
Authors: Cavacece M. , Vita L.
Published: January 2014

A double‐ended cantilever beam as a distributed parameter dynamic vibration absorber has been applied to a single‐degree‐of‐freedom system subjected to harmonic forces.

In this investigation, the beam has been analyzed under the well known model of Timoshenko and the computation of best parameters is based on the Chebyshev’s optimality criterion.

This is somewhat novel in the field since:

The design of cantilever beams as dynamic vibration absorbers is usually made under the hypotheses of the Euler‐Bernoulli theory;

It is the first time that the Chebyshev’s criterion is applied to the design of a double‐ended cantilever beam used as a dynamic vibration absorber.

For a ready use of the results herein presented, design charts allow a quick choice of optimal parameters such as tuning ratio and mass ratio.
Vibration of a Laminated Beam with a Delamination Including Contact Effects
Authors: Ostachowicz W. , Żak A.
Published: January 2014

Certain results are presented in this paper on damped vibration of a laminated cantilever beam with a single closing delamination. In order to investigate this task the finite element method has been applied in the current study. For modelling the beam higher order shear deformation beam finite elements have been used. The vibration of the beam is investigated in the time domain using a dynamic contact algorithm developed by the authors. The algorithm is based on the Newmark method and also incorporates a Newton‐Raphson based procedure for resolving the equation of motion. The time series obtained from solving the equation of motion have been subsequently analysed in the frequency domain by using FFT (Fast Fourier Transform). The vibration responses of the beam due to various harmonic and impulse excitations, at different delamination locations, and for different delamination lengths, as well as changes in the dissipation of damping energy due to the delamination, have all been considered in the paper.
Bifurcations and Crises in a Shape Memory Oscillator
Authors: Machado Luciano G. , Savi Marcelo A. , Pacheco Pedro M.C.L.
Published: January 2014

The remarkable properties of shape memory alloys have been motivating the interest in applications in different areas varying from biomedical to aerospace hardware. The dynamical response of systems composed by shape memory actuators presents nonlinear characteristics and a very rich behavior, showing periodic, quasi‐periodic and chaotic responses. This contribution analyses some aspects related to bifurcation phenomenon in a shape memory oscillator where the restitution force is described by a polynomial constitutive model. The term bifurcation is used to describe qualitative changes that occur in the orbit structure of a system, as a consequence of parameter changes, being related to chaos. Numerical simulations show that the response of the shape memory oscillator presents period doubling cascades, direct and reverse, and crises.
Hardware in the Loop Test‐Rig for Identification and Control Application on High Speed Pantographs
Authors: Collina A. , Facchinetti A. , Fossati F. , Resta F.
Published: January 2014

Trains current collection for traction motors is obtained by means of a sliding contact between the overhead line (OHL) and the collector strips mounted on the pantograph head. The normal force by which the collector presses against the contact wire ensures the contact pressure for the electrical contact. As the train speed increases, the variation of contact force between pantograph and catenary increases, and the pantograph‐OHL dynamic interaction becomes greater. This condition causes excessive mechanical wear and contact wire uplift (for high values of contact forces), and leads to high percentage of contact loss, arcing and electrically related wear.

The topic of actively controlled pantograph is gaining more interest as a tool to increase the performance of the current collection at high speed. In the last few years, it appears possible to transfer the knowledge based on numerical experiments, to the real operating condition. An important step in this direction is the set up of a laboratory hardware in the loop test‐rig in which the control strategies and the actuation can be tested, before tests performing in real life conditions, in order to demonstrate their actual feasibility. The present paper describes an hardware in the loop (HIL) test‐rig developed by the authors, which allows to reproduce the dynamical interaction between overhead lines and pantograph in high speed railways. Using the described laboratory set‐up, experimental investigation on the problems related with pantograph‐OHL interaction can be performed, very similarly to the real life operating conditions, with the advantage of varying test parameters and conditions easily.
Rate Dependent Multicontinuum Progressive Failure Analysis of Woven Fabric Composite Structures under Dynamic Impact
Authors: Lua James , Key Christopher T. , Schumacher Shane C. , Hansen Andrew C.
Published: January 2014

Marine composite materials typically exhibit significant rate dependent response characteristics when subjected to extreme dynamic loading conditions. In this work, a strain‐rate dependent continuum damage model is incorporated with multicontinuum technology (MCT) to predict damage and failure progression for composite material structures. MCT treats the constituents of a woven fabric composite as separate but linked continua, thereby allowing a designer to extract constituent stress/strain information in a structural analysis. The MCT algorithm and material damage model are numerically implemented with the explicit finite element code LS‐DYNA3D via a user‐defined material model (umat). The effects of the strain‐rate hardening model are demonstrated through both simple single element analyses for woven fabric composites and also structural level impact simulations of a composite panel subjected to various impact conditions. Progressive damage at the constituent level is monitored throughout the loading. The results qualitatively illustrate the value of rate dependent material models for marine composite materials under extreme dynamic loading conditions.
Variable Volumetric Stiffness Fluid Mount Design
Authors: Vahdati Nader , Ahmadian Mehdi
Published: January 2014

Passive fluid mounts are commonly used in the automotive and aerospace applications to isolate the cabin from the engine noise and vibration. Due to manufacturing and material variabilities, no two identical fluid mount designs act the same. So, fluid mounts are tuned one by one before it is shipped out to customers. In some cases, for a batch of fluid mounts manufactured at the same time, one is tuned and the rest is set to the same settings. In some cases they are shipped as is with its notch frequency not being in its most optimum location. Since none of the passive fluid mount parameters are controllable, the only way to tune the mount is to redesign the mount by changing fluid, changing inertia track length or diameter, or changing rubber stiffness. This trial and error manufacturing process is very costly. To reduce the fluid mount notch frequency tuning cycle time, a new fluid mount design is proposed. In this new fluid mount design, the notch frequency can be easily modified without the need for any redesigns. In this paper, the new design concept, and its mathematical model and simulation results will be presented.
Sensitivity of Dynamic Methods for Damage Detection in Structural Concrete Bridges
Authors: Breccolotti M. , Franceschini G. , Materazzi A.L.
Published: January 2014

A critical analysis of the available methods for the assessment of structural concrete bridges through the observation of their dynamic response is carried out. A mathematical model for the evaluation of the natural frequencies shift due to bridge damage is applied to the case of an existing reinforced concrete bridge. The numerical results, along with the general structure of the mathematical problem, allow discussing some limitation and drawbacks of the dynamic methods. Namely the need for a reference set of the bridges dynamic properties before the onset of damage and the effect of the ambient temperature variation may lead, in many cases, to unreliable estimates of the structural condition of the investigated bridges.