loss factor

High damping materials allow vibration and noise to be suppressed or at least reduced. Unfortunately, materials with high loss tangents also exhibit low modulus of elasticity. A new composite damping material is investigated, which consists of specially designed fibers embedded in a viscoelastic matrix. This new approach not only enhances damping through improvement of matrix loss tangent by the addition of elastomer, but also through selection of adequate ply orientation, ply stacking, geometry of fibers, and fraction of fibers. Theoretical analysis of the viscoelastic properties of this composite is presented in order to identify the optimum material with high stiffness and high loss tangent according to all parameters. To address validation theoretical developments are compared to experimental results.

Five types of nanofillers, namely, silica, surface-silylated silica, alumina, surface-silylated alumina, and boron nitride, were tested in this study. Nanocomposites composed of an epoxy/amine resin and one of the five types of nanoparticles were tested as dielectrics with a focus on (i) the surface functionalization of the nanoparticles and (ii) the water absorption by the materials. The dispersability of the nanoparticles in the resin correlated with the composition (OH content) of their surfaces. The interfacial polarization of the thoroughly dried samples was found to increase at lowered frequencies and increased temperatures. The β relaxation, unlike the interfacial polarization, was not significantly increased at elevated temperatures (below the glass-transition temperature). Upon the absorption of water under ambient conditions, the interfacial polarization increased significantly, and the insulating properties decreased or even deteriorated. This effect was most pronounced in the nanocomposite containing silica, and occurred as well in the nanocomposites containing silylated silica or non-functionalized alumina. The alternating current (AC) breakdown strength of all specimens was in the range of 30 to 35 kV•mm -1 . In direct current (DC) breakdown tests, the epoxy resin exhibited the lowest strength of 110 kV•mm -1 ; the nanocomposite containing surface-silylated alumina had a strength of 170 kV•mm -1 . In summary, water absorption had the most relevant impact on the dielectric properties of nanocomposites containing nanoparticles, the surfaces of which interacted with the water molecules. Nanocomposites containing silylated alumina particles or boron nitride showed the best dielectric properties in this study.

Poly(2-nonyl-2-oxazoline) 80 -stat-poly(2-dec-9 1 -enyl-2-oxazoline) 20 and poly(2-dec-9 1 -enyl-2-oxazoline) 100 can be synthesized from the cationic ring-opening polymerization of monomers that can be derived from fatty acids from renewable resources. These (co)poly(2-oxazoline)s can be crosslinked with di-and trifunctional mercapto compounds using the UV-induced thiol-ene reaction. The complex permittivity of the corresponding networks increases with the temperature and decreases with the network density. In a frequency range from 10 ´2 to 10 6 Hz and at temperatures ranging from ´20 to 40 ˝C, the changes of the real part of the complex permittivity as well as the loss factor can be explained by interfacial polarization within the material. At a temperature of 20 ˝C and a frequency of 50 Hz, the permittivity of the crosslinked (co)poly(2-oxazoline)s covers a range from 4.29 to 4.97, and the loss factors are in the range from 0.030 to 0.093. The electrical conductivities of these polymer networks span a range from 5 ˆ10 ´12 to 8 ˆ10 ´9 S/m, classifying these materials as medium insulators. Notably, the values for the permittivity, loss factor and conductivity of these copoly(2-oxazoline)s are in the same range as for polyamides, and, hence, these copoly(2-oxazoline)-based networks may be referred to as "green" alternatives for polyamides as insulators in electronic applications.

The extraordinary properties of shape memory NiTi alloy are combined with the inherent viscoelastic behavior of a silicon elastomer. NiTi wires are incorporated in a silicon elastomer matrix. Benefits include features as electrical/thermal conductivity, reinforcement along with enhanced damping performance and flexibility. To gain more insight of this composite, a comprehensive dynamic thermomechanical analysis is performed and the temperature-as well as frequency-dependent storage modulus and the mechanical loss factor are obtained. The analyses are realized for the composite and single components. Moreover, the models to express the examined properties and their temperature along with the frequency dependencies are also presented.

The extraordinary properties of shape memory NiTi alloy are combined with the inherent viscoelastic behavior of a silicon elastomer. NiTi wires are incorporated in a silicon elastomer matrix. Benefits include features as electrical/thermal conductivity, reinforcement along with enhanced damping performance and flexibility. To gain more insight of this composite, a comprehensive dynamic thermomechanical analysis is performed and the temperature- as well as frequency-dependent storage modulus and the mechanical loss factor are obtained. The analyses are realized for the composite and single components. Moreover, the models to express the examined properties and their temperature along with the frequency dependencies are also presented.

This paper explains a simple and efficient methodology for calculating monthly energy losses (EL) using the load loss factor technique and a representative composite load profile. One of the important benefits of the proposed work is a simpler, more efficient and less rigorous method to estimate the system-wide energy loss of an extensive distribution network with reasonable accuracy. The sum of all EL provided by each feeder section is used to calculate the total feeder EL. A base case feeder with a typical cable type and power factor is used to generate regression equations, a peak power loss function to estimate the EL. A case study is then used to show the models and techniques that have been established. The result indicates a high level of agreement with the time-series load flow simulations (smaller than 10% deviations). With this model, an approach to estimate the EL of all radial feeders of various configurations and characteristics could be extended and implemented. The sp...

In this paper, the effect of different boundary conditions on the free vibration analysis response of a sandwich plate is presented using the higher order shear deformation theory. The face sheets are orthotropic laminated composites that follow the first order shear deformation theory (FSDT) based on the Rissners-Mindlin (RM) kinematics field. The motion equations are derived considering the continuity boundary conditions between the layers based on the energy method and Hamilton's principle. The frequency and mode shapes of the structure are obtained using the differential quadrature method (DQM). The effects of different parameters such as the face sheet-to-core stiffness ratio, the boundary conditions, and the core-to-face sheet thickness ratio on the frequency of the sandwich plate are shown. Moreover, the numerical results indicate that the frequency of the CCCC and CFFF sandwich plates predict the higher and lower frequency, respectively.

In this paper, the results of the experimental investigation into the addition of indentations of power-law profile into composite plates and panels and their subsequent inclusion into composite honeycomb sandwich panels are reported. The composite plates in question are sheets of composite with visible indentations of power-law profile. A panel is a sheet of composite with the indentations encased within the sample. This makes a panel similar in surface texture to an un-machined composite sheet (reference plate) or conventional honeycomb sandwich panel. In the case of quadratic or higher-order profiles, the above-mentioned indentations act as two-dimensional acoustic black holes (ABH) for flexural waves that can absorb a large proportion of the incident wave energy. For all the composite samples tested in this investigation, the addition of two-dimensional acoustic black holes resulted in further increase in damping of resonant vibrations, in addition to the already substantial inherent damping due to large values of the loss factor for composites. Due to large values of the loss factor for composite materials, there was no need to use attached absorbing layers to implement the acoustic black hole effect.

Factor H is introduced for direct head loss calculation and sizing in dual-diameter laterals of sprinkler and trickle irrigation systems when the Hazen-Williams equation is to be applied. Application of this factor prevents trial and error and uses fewer head-loss equations in calculating the total friction loss and designing dual-diameter laterals. The proposed factor is a function of total number of outlets on the lateral, number of outlets on the smaller-diameter section of the pipe and ratio of smaller diameter to the larger diameter pipe. By solving two practical examples, the advantage of this factor over other approaches was shown. It was also demonstrated that design of lateral sizing by the given equations is simpler, easier and more accurate than the previous methods.

This study presents an analytical solution for calculating sound transmission loss through a circular cylindrical shell made of polymeric foam. The intended cylinder is excited by an acoustic plane wave. The equations of motion for the cylindrical shell are derived by the first-order shear deformation. Besides, the polymeric foam is characterized using functionally graded Zener model in which the mechanical properties are varying continuously in the thickness direction as well as considering the frequency-dependent parameters. Due to the lack of study on the vibro-acoustic behavior of the viscoelastic graded materials, the results are compared with those of some researchers in the literature of elastic materials, and excellent concurrences are observed. Next, the effects of geometrical and material characteristics on the transmission loss factor are investigated. The influence of various power-law index illustrates that by reducing this parameter, the sound transmission loss through the shell is extensively increased. Finally, a comparison is performed along with four models of the cylindrical shells with the same weights including functionally graded viscoelastic, functionally graded, viscoelastic and elastic materials. As a key result, it can be explored that the sound transmission loss in a functionally graded viscoelastic shell is more enhanced than the other cylinders.

This work aims to present an experimentally verified analytical solution to examine damping properties of systems including viscoelastic treatments. Although there are several methods for characterizing the behavior of three-layer damping systems, the RKU method is the most frequently used one. In this paper, this method is modified such a way that to be applied for a five-layer damping system. The achieved analytical relations are then employed to study the effects of a four-layer vibration-absorbing coating on the dynamic behavior of an aluminum sheet with free-free boundary conditions. Since the vibration-damping properties of the coating are unknowns, its loss factor and shear modulus are experimentally extracted based on the ASTM E756-05 standard method. The comparison between the analytical solution and performed modal tests expresses the efficiency of the presented method.

decreased with increasing temperature. Predictive equations were developed for dielectric constant (R 2 = 0.82) and dielectric loss factor (R 2 = 0.90) as a function of temperature, moisture, sugar, and starch. The predictive equations would be useful in determining the dielectric properties of sweet potato purees for the microwave processing technology.

El nuevo reglamento en materia de protección frente al ruido del Código Técnico de la Edificación (DB HR) sienta las bases para que los proyectistas calculen los parámetros de calidad acústica en las viviendas mediante un método que proviene del método simplificado la norma europea UNE 12354-1:2000. Dicho método toma como variables de entrada, no sólo los parámetros acústicos de los elementos involucrados, sino también sus dimensiones y las particularidades geométricas de cada par de recintos. Existe la creencia generalizada de que el caso peor se encuentra cubierto si se considera que ambos recintos presentan las cuatro aristas coincidentes. Esta suposición, que simplifica convenientemente la casuística de aplicación del método de cálculo, es en general incorrecta y puede, en algunos casos concretos, tener importantes consecuencias sobre el resultado final del cálculo de aislamiento. En este texto se presenta la casuística más habitual incluyendo algunos escenarios en los que existen dos elementos separadores que todavía no han sido incluidos en las hojas de cálculo oficiales. Se analizan asimismo algunas consecuencias de aceptar la simplificación por simetría.

The objective of the present work was to investigate the effect of presence of SiC reinforcement and the vibration frequency on the overall damping characteristics of pure magnesium. The testing method uses a combination of the modified free -free beam method coupled with a circle fit approach. The effect of frequency on the damping property was studied by adding end masses to the specimen so as to alter the resonant frequency of the suspended beam. In the present study, the results are compared against a monolithic magnesium sample. The results revealed a higher damping capability of the composite specimen at all tested frequencies when compared to monolithic magnesium. Both monolithic and reinforced magnesium showed a progressive decrease in damping with an increase in frequency. An attempt is made to rationalise the damping behaviour of the composite in terms of the presence of a process induced plastic zone at the matrix/particulate interface and the operating frequency. MST/6052

In order to understand the loss mechanism of mechanical oscillators in micro-electromechanical systems, we have studied the temperature dependence of the quality factor Q of a high Q silicon mechanical oscillator from 0.4 K to 300 K. At temperatures above 70 K, the energy loss is principally caused by thermoelastic effect in the flexural components of the modes. Below 50 K, we find the improvements in vibration isolation guided by the finite element method do not significantly improve its Q. This indicates that some intrinsic loss mechanism may still be important even at low temperatures.

The mathematical model of a flexible cantilever beam with a constrained viscoelastic layer and shape memory alloy layer called smart damping treatment (SDT) is presented. It is shown that a change of the elastic modulus of the shape memory alloy layer will affect the system loss factor and resonance frequency. The recovery stress of the SMA layer leads to an inhomogeneity in the governing differential equation. The recovery stress also functions as an excitation to the system. The effects of the different parameters found in the analysis are discussed in the paper.

The temperature effects on frequency, loss factor and control of a flexible beam with a constrained viscoelastic layer and shape memory alloy layer(SMA) are discussed. It is shown that the temperature in the SMA (actuation) layer is very important in the determination of frequency and loss factor of such a structure. The effects of damping layer shear modulus and damping layer height as affected by the temperature are also discussed. As temperature plays such an important role, it is, therefore, imperative to evaluate temperature effects on the control of the system as well. Results with and without active control are discussed.

High damping materials allow vibration and noise to be suppressed or at least reduced. Unfortunately, materials with high loss tangents also exhibit low modulus of elasticity. A new composite damping material is investigated, which consists of specially designed fibers embedded in a viscoelastic matrix. This new approach not only enhances damping through improvement of matrix loss tangent by the addition of elastomer, but also through selection of adequate ply orientation, ply stacking, geometry of fibers, and fraction of fibers. Theoretical analysis of the viscoelastic properties of this composite is presented in order to identify the optimum material with high stiffness and high loss tangent according to all parameters. To address validation theoretical developments are compared to experimental results.

The present study is concerned with the dynamic analysis of sandwich beams, with a viscoelastic core between composite layers and subjected to a moving load. The governing equations are derived by application of Hamilton principle and solved by finite element method. The coupled system of equations is integrated numerically by the Newmark method. Facial composites are modeled using classical plate theory and the kernel using Timoshenko's theory. This study deals with free and forced vibrations of the sandwich beams by considering the frequency according to the viscoelastic properties in frequency-domain and the numerical asymptotic method is employed in order to solve the complex eigenvalue problem. The influences of viscoelastic loss factor, orientation fiber of the composite layers and thickness ratio on the dynamic responses of sandwich beams are investigated. The results reported in this paper show that the viscoelastic loss factor has a significant effect on the vibration behavior involving the improvement of the damping of the structure. The influence of fiber orientation on vibration behavior showed that the damping of the structure could be improved by adopting a better configuration of the composite layers. The results obtained with the effect of the thickness ratio show that the sandwich structure has a greater dissipative vibratory energy capacity for the low viscoelastic thickness values.

Biological tissues, including insect tissues, are among lossy dielectric materials. The permittivity properties of these materials are described by loss factor ε″ and loss tangent tgδ. The dielectric properties of the worker honeybee body homogenate are tested in the range of high frequencies from 1 MHz to 6 GHz. The homogenate is produced by mixing whole worker honeybees and tested with an epsilometer from Compass Technology and a Copper Mountain Technologies vector circuit analyser VNA. Due to their consistency, the homogenate samples are placed inside polyurethane sachets. The measured permittivity relates to two components of a sample: homogenate and polyurethane. For five samples, two extremes were specified for the permittivity, loss factor ε″, and the loss tangent tgδ, for the frequency range 20 ÷ 80 MHz and 3 GHz. Four techniques of testing permittivity in biological tissues were used to determine the dielectric properties of the homogenate. A calculation model was developed...

A multidimensional finite element model of a viscoelastic sliding bearing is presented. The model consisted on two independent matrices, one represents the stiffness behavior and the other represents a damping matrix. These matrices are independent from each other since the viscoelastic material properties are assumed to be a Kelvin type material. Kelvin type materials are approximated as a linear combination of an elastic modulus and a viscous coefficient. This simple model describes accurately almost any rubber found in several machine components. The model combines the linearity of the Kelvin type material plus the finite element interpolation scheme. Thus, the advantages of the finite element method can be applied to any geometry. In order to obtain Kelvin´s coefficients, a test rig was built. Material properties were experimentally determined and the model was validated. Afterwards, a discretized model was developed for a radial support bearing with an embedded rubber band. From this model, it was possible to analyze bearing stiffness and damping properties. Then, damping and stiffness coefficients were input into a rotordynamic system. This system consisted on a single-mass rotor with a slender shaft. Thus, imbalance response characteristics were obtained applying the viscoelastic sliding bearings. This procedure allows the designer to evaluate alternative damping mechanisms that can be added to sliding bearings.

In recent decades, there has been an increasing penetration of new smart
grids (SG) and distributed generations (DG) that are connected to the
distribution network (DN). Thus, it is critical for utilities to analyze and
assess their impact on the power system networks, which often necessitates
major decisions about network operation and planning. Consequently,
researchers are constantly developing new and improved methods of
advanced control and operation to address these challenges. Unfortunately,
there are a limited number of realistic DN models that are made publicly
available by the utilities for the development, testing, and evaluation of such
new methods. This is mainly caused by the utilities' concerns and reluctance
to reveal the public's real and “sensitive” network information. Although
international standard test systems such as IEEE and CIGRE are publicly
available, these test network models are customized based on the US DN
and are not representative of the other networks that operate under different
network settings. This paper presents a brief literature survey of existing and
prominent representative DNs with a special emphasis on identifying the
general description, and application, as a comparison for future development
of test network in Malaysia.

Highlights 3.61% 43.9% 0.15% 8.64% 43.7% Overall power losses of a typical piezoelectric ultrasonic transducer under free conditions Dielectric loss Matching structrual damping Backing structrual damping Piezoelectric structural damping Friction loss

Although the classical theory of lumped mechanical systems employs the viscous friction mechanisms (dashpots), the loss factors of most solid structures are largely controlled by hysteresis. This paper presents new relationships for the dynamics of 2-DOF in-series systems with hysteresis damping. The most important among them is a close-form equation for the critical loss factor that was derived as the marginal condition for the degenerate case where the higher-frequency resonance peak fully vanishes in the vibration spectrum of the second mass. The critical loss factor can take values between 0 and 2-3/2 ≈ 0.354 and depends on the ratio of the natural frequencies of 2-DOF system: the closer the undamped natural frequencies, the lower the critical loss factor. The equation may help to interpret the vibration spectra for the second mass in the real 2-DOF systems, in particular on sweep-sine shaker tests. The single resonance peak in the degenerate case for a 2-DOF grows up notably as...

The objective of the present work was to investigate the effect of presence of SiC reinforcement and the vibration frequency on the overall damping characteristics of pure magnesium. The testing method uses a combination of the modified free-free beam method coupled with a circle fit approach. The effect of frequency on the damping property was studied by adding end masses to the specimen so as to alter the resonant frequency of the suspended beam. In the present study, the results are compared against a monolithic magnesium sample. The results revealed a higher damping capability of the composite specimen at all tested frequencies when compared to monolithic magnesium. Both monolithic and reinforced magnesium showed a progressive decrease in damping with an increase in frequency. An attempt is made to rationalise the damping behaviour of the composite in terms of the presence of a process induced plastic zone at the matrix/particulate interface and the operating frequency. MST/6052

The optical performance of the reflective polarizer was investigated over three kinds of direct-lit backlights and/or different configurations of the optical sheets. The optical gain factor achieved by using the reflective polarizer increased as the diffuse nature of the optical sheet was enhanced, because of the more efficient polarization conversion. In addition, the gain factor decreased substantially in flat-lamp backlights compared to tubular-lamp backlights, which was ascribed to the high loss factor during the polarization recycling process due to the complex structure and large area of flat lamps. All these results suggested that reducing the loss factor of the backlight is very important for efficient polarization conversion and thus high optical gain of the reflective polarizer.

Orthopaedic implant fixation is strongly dependant upon the effective mechanical properties of newly formed tissue. In this study, we evaluated the potential of modal analysis to derive viscoelastic properties of periprosthetic tissue. We hypothesized that Young's modulus and loss factor could be obtained by a combined theoretical, computational and experimental modal analysis approach. This procedure was applied to ex vivo specimens from a cylindrical experimental implant placed in cancellous bone in an unloaded press-fit configuration, obtained after a four week observation period. Four sections each from seven textured titanium implants were investigated. The first resonant frequency and loss factor were measured. Average experimentally determined loss factor was 2% (SD 0.4%) and average first resonant frequency was 2.1 KHz (SD: 50). A 2D axisymmetric finite element (FE) model identified effective Young's modulus of tissue using experimental resonant frequencies as input. Average value was 42 MPa (SD: 2.4) and no significant difference between specimens was observed. In this pilot study, the non-destructive method allowed accurate measure of dynamic loss factor and resonant frequency and derivation of effective Young's modulus. Prior to implementing this dynamic protocol for broader mechanical evaluation of experimental implant fixation, further work is needed to determine if this affects results from subsequent destructive shear push-out tests.

The quality factor Q of a damped oscillator equals 2π times the ratio of stored energy to the energy dissipated per cycle. This makes Q a sensitive probe of energy losses. Using modest equipment, we measured the acoustical Q for a set of cylindrical pipes having the same resonant frequency, but different diameters D. The graph of Q vs D could be well fitted with two parameters, one of which corresponds to energy loss via radiation from the ends of the pipe, and the other to thermal and viscous losses very close to the pipe wall. The wall loss parameter was quite constant no matter where the pipes were located, but the radiative loss parameter varied significantly with location inside a room, suggesting that room reflections affected the sound radiated from the pipe. This study offers valuable insights at no great expense, and could be the basis of an upper-division undergraduate laboratory experiment.

دییامن هدافتسا لیذ ترابع زا هلاقم نیا هب عاجرا يارب : Please cite this article using: M. Bagheri, A. Bijari, M. Raghebi, Modeling and calculating the anchor loss quality factor in the plunging-mode vibrations of a micromechanical rectangular-plate resonator with two T-shaped support beams, Modares Mechanical Engineering, Vol. 14, No. 12, pp. 75-84, 2014 (In Persian) لدم و يزاس م هبساح هیکت فلاتا تیفیک بیرض یلیطتسم رگدیدشت روانش یشاعترا دم رد هاگ

Microwave heating has been suggested by various authors as a suitable technology for extraction of organic material from oil shales. However, one of the limiting factors in the development of this technology is a lack of accurate dielectric property data for design purposes. In this study the dielectric behaviour of El-lajun oil shale is quantified. The dielectric constant and loss

Friction-induced vibration due to mode coupling is a major concern in a wide variety of mechanical systems. Though there are numerous papers on both linear and non-linear stability analyses of dynamical systems with friction-induced vibrations, the effects of damping on the evolution of the stable-unstable regions is not yet fully understood. The purpose of this work is to study a pin-disc model describing a typical frictioninduced vibration due to a geometric constraint in order to illustrate the effects of damping on linear stability analyses. The results not only illustrate the influence of damping for determining the stable and unstable zones, but they also indicate that the ''most efficient damping factor of the coupling modes'' is an important factor to be taken into account. The physical mechanism causing this change in instability as a consequence of the damping factor is also suggested to help avoid bad design.

High sound insulation façade requirements in contemporary buildings, led to the development of high-performance multilayer glazing systems. In this work a combined experimental and analytical approach has been adopted to predict the sound transmission loss of systems made of glass and PVB layers, which are used in several engineering areas (building, transportation, etc.). In particular, the mechanical properties of glazing systems have been measured using resonance curve method of flexural waves on multilayer glass beams with different boundary conditions. In order to achieve reliable input mechanical data (Young's modulus and loss factor) the beams are characterized in free-free and clamped-clamped boundary conditions respectively. Moreover, the diffuse field sound transmission loss of glass panels has been predicted through an analytical method for solid elastic layers. Results from the above-mentioned procedure have been compared with laboratory tests carried out according to ISO Standard 10140 series.

The objective was to investigate possible vibration isolator solutions for a 4D entertainment theater. The paper focused on resolving a vibration leakage issue experienced by customers of Company A which manufactures tactile motion actuators for 4D theater entertainment purposes. The investigation started by utilizing Cambridge Engineering Selector software to determine the value of the mechanical loss factor for given materials. Elastomers had the best mechanical loss coefficient, specifically polyurethanes. While considering the specifications provided by Company A, certain parameters such as nominal load withstanding and prices were considered. After investigating the materials thoroughly, Sorbothane showed the best performance along with suitable prices. The vibrational system investigated resulted in a frequency ratio of 6, and a transmissibility of 2.86% at normal conditions, which indicates that the material selected was suitable. Sorbothane material at shore 00 and durometer 50 showed its capability to withstand maximum nominal loading at 635 kg (1400 lbs). This was 57% higher than the targeted loading. The mechanical loss factor was 0.52 at 50-Hz excitation frequency, which was high enough to dissipate excessive vibrations.

How to cite Complete issue More information about this article Journal's homepage in redalyc.org Scientific Information System Network of Scientific Journals from Latin America, the Caribbean, Spain and Portugal Non-profit academic project, developed under the open access initiative

A tunable TM012-mode resonant cavity with an additional tuning mechanism and working at 2.45GHzhas been designed, fabricated and testedfor determination of dielectric properties of dates. The cavity has a Q-factor >5000, and a tuning mechanism which gives it more flexibility and controllability. The cavity has been used for determining the dielectric properties of Rezaiz, the most common type of dates used in the production of date juice in the Eastern Province of the Kingdom of Saudi Arabia. The dielectric constant for this type of dates was 4.6±0.16, and the loss factor was 0.21±0.03, at 8.75% moisture. These results are comparable with the dielectric properties of some other fruits, of similar composition, a the same moisture level.

Contribution of step-in geometric discontinuity to the longitudinal coupling impedance has been obtained analytically using exact field matching. We assumed a perfectly conducting beam-pipe wall of two different radii connected coaxially at z¼ 0 so that the contribution to the longitudinal coupling impedance is purely due to the beam-pipe geometric discontinuity. We also obtained the longitudinal loss factor for a Gaussian beam as a function of beam energy and bunch length. Results have been analyzed numerically for some representative parameters close to real machine parameters. Analytical results have also been compared with numerical simulation from CST at relativistic beam energies. We found a very good agreement between theory and simulation.

The purpose of the present research is to obtain waste of polymeric composite as an insulator capacitive application. Rubber materials, once they end their useful life, may be difficult to reuse or recycle. At present, research only uses one tire recycling method, which involves grinding and separating steel and fibers from vulcanized rubber, and then using the rubber particles for industrial capacitors. The methodology for this research is to compare the permittivity (ε′ and ε″) between high-density polyethylene (HDPE) and the polymer matrix compound, consisting of an HDPE polymeric matrix blended with end-of-life tire particles (ground tire rubber (GTR)), to analyze the feasibility of using such tires as electrically insulating materials (dielectrics). The incorporation of carbon black in the GTR compounds modifies conductivity; GTRs carry a significant amount of carbon black, and therefore some electrical properties may change significantly compared to highly insulating polymer s...

A numerical study to investigate the effects of temperature on the diffuse sound transmission loss (TL) of sandwich plates is presented. The numerical prediction tool used is based on a finite element formulation for the sandwich plate coupled to a boundary element method for the acoustic medium. The plate formulation is derived from Kirchhoff's theory for the elastic faces and Mindlin's theory for the core. The frequency-temperature dependence of the viscoelastic material properties are taken into account using an experimentally derived viscoelastic constitutive law. The results presented deal with a laminated glass subjected to a diffuse sound field. It is found that the dip of the TL curve at the coincidence frequency of the plate is totally removed for temperatures where this frequency is in the transition region of the used viscoelastic material. Indeed, the relative low value of the storage modulus and the high value of the loss factor in this region induce high transv...

A numerical study to investigate the effects of temperature on the diffuse sound transmission loss (TL) of sandwich plates is presented. The numerical prediction tool used is based on a finite element formulation for the sandwich plate coupled to a boundary element method for the acoustic medium. The plate formulation is derived from Kirchhoff's theory for the elastic faces and Mindlin's theory for the core. The frequency-temperature dependence of the viscoelastic material properties are taken into account using an experimentally derived viscoelastic constitutive law. The results presented deal with a laminated glass subjected to a diffuse sound field. It is found that the dip of the TL curve at the coincidence frequency of the plate is totally removed for temperatures where this frequency is in the transition region of the used viscoelastic material. Indeed, the relative low value of the storage modulus and the high value of the loss factor in this region induce high transv...

A microwave bench operating in the frequency range 8-12GHz (X-band) was used to investigate some of the electrical characteristics of the talc filled polypropylene composite. The impedance, return loss, and insertion loss are measured as a function of frequency in the X-band range. It was found that electromagnetic waves interact with the material via the impurities, inclusions and voids existing in the bulk composite. The impedance, return loss and insertion loss show relatively low frequency dependence. Also, the return loss and the impedance exhibit a resonance behaviour at 11.91 GHz. The results suggest that this composite material could be used in some microwave applications.

Damping treatment is a standard practice in many industries for controlling excessive vibration at resonance. Different damping materials are available for various engineering applications. Wax is one of them, and it’s mostly used in musical instruments. There are two types of wax are available namely beeswax (natural wax) and cosmetic wax. The aim of the present study is to measure damping properties of these two types of wax using Oberst Beam Method (OBM). The effects of damping material’s thickness and bare sample on damping loss factor are studied.

Magnetorheological elastomers (MRE) are smart composite materials by which their mechanical properties, such as stiffness, are changed under a magnetic field. In this article, the introduction of a variable stiffness coupling (VSC) fitted within a shaft for torsional vibration isolation that would adapt and change its attenuation frequency range is presented. The VSC concept on torsional vibration isolation is tested experimentally. MRE samples with 40% volume fraction are fabricated and manufactured using a 3D mold design and fixed within a coupling in a shaft to investigate the magnetic field effect on the torsional rigidity. Impact hammer test is conducted along with an accelerometer to obtain the transmissibility factor analysis. Results show that the vibration level decreases when the magnetic field increases. The 1st natural frequency of the system happened at 26 Hz and moved to 28 Hz when the applied current increases from 0 mT to 12.38 mT. MRE torsional stiffness increased f...

Vibration is undesirable, wasting energy and creating unwanted sound – noise. Sometimes these vibrations cause minor or serious performance or safety problems in engineered systems. Damping is one potential approach to reducing vibration level, in a structural system. Viscoelastic material among the damping materials is widely used to reduce the structural vibration. This paper describes theanalysis of performance of free layer damping treatment and constrain layer damping treatment to attenuate vibration response amplitude. Measurements are performed on Oberst beam as per ASTM E 756-05 standard.[1] This detailed experimental program that was undertaken to characterize the damping loss factor of Styrene-Butadiene (SBR) as a composite materials.The FLD and CLD treatments are compared and analyzed in this paper.