Showing papers on "Loss factor published in 2001"

Dielectric properties of epoxy/silica composites used for microlectronic packaging, and their dependence on post-curing

Abstract: We studied the dielectric properties (dielectric constant and loss factor) of epoxy molding compounds used for electronic packaging, as a function of frequency (100 Hz–100 kHz) and temperature (25–100 °C). Studies were performed for samples with different formulations (various silica and carbon black contents). At room temperature a loss peak is found at 50 kHz, whose intensity is enhanced by carbon black addition. Additional loss is detected below 1 kHz when the temperature is increased up to 100 °C. We also studied the influence of post-mold curing time (0–12 h at 165 °C) on the dielectric properties. The dielectric constant monotonically decreases with post-mold cure to level off to a minimum value for long post-cure durations. The loss factor first increases for short post-curing times, and then decreases as post-cure is continued. The origin of loss is discussed with reference to common relaxation processes observed in epoxy polymers.

Characterization of the vibrational damping loss factor and viscoelastic properties of ethylene-propylene rubbers reinforced with micro-scale fillers

Abstract: The influence of microscale fillers on ethylene–propylene rubbers (EPR) was examined with respect to their vibrational damping capacity and viscoelastic properties. The vibrational damping and dynamic mechanical properties of reinforced EPR were studied in systematic and comparative ways that reinforced the evidence of a direct relation between the vibrational damping loss factor and its mechanical damping loss factor. In this study, the sensitivity of the vibrational damping loss factor of reinforced EPR was quantified with respect to the variation in thickness, filler type, and filler content. Dynamic mechanical relaxation behaviors were also analyzed. The viscoelastic properties in terms of the storage modulus, loss modulus, mechanical damping loss factor, and frequency dependence of molecular relaxation showed interesting results with the filler types and compositions that had good correspondence with the vibrational damping behaviors. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3058–3066, 2001

Characterization of the Strain-amplitude and Frequency Dependent Damping Capacity in the M2052 Alloy

Abstract: In order to reveal the damping behavior of M2052 alloy dependent on the strain-amplitude and frequency, a centrally excited beam sample was used in free-decaying and frequency sweeping damping measurement. The decaying oscillations and the resonant peaks were obtained directly by the surface strain of the sample. Frequency sweeping was conducted at the strain-amplitudes of 1 x 10 -5 ∼ 1 x 10 -4 , and frequencies between 50 and 4000 Hz. The loss factor results were described in a contour map as the function of both strain-amplitude and frequency. Logarithmic decrement and loss factor were also obtained from the free-decaying oscillations at the first resonant frequency and different strain-amplitudes. The damping capacity of the alloy at larger strain-amplitudes could be also affected by the damping mode.

Composite soundproofing system for room-limiting surfaces

Abstract: The compound sound protection system for an area bounding a room comprises a floor, wall or ceiling lining (V), a sound damping layer (D) with a specified minimum flexural loss factor, and a sound insulation layer with specified uniaxial expansion loss factor, dynamic stiffness and density. The combined maximum thickness of the sound damping and insulating layers is limited to 14 mm.

Thermodynamic Model of the Loss Factor Applied to Steam Turbines

Abstract: Erosion, roughness, steam path damage, etc., are factors that reduce power capacity in a steam turbine. Any power loss occurring locally in intermediate stages of a steam turbine results in more available energy in the downstream stages, this effect is well known as the Loss Factor (Salisbury, 1974; Stodola, 1927; Husain, 1984). Currently, the Loss Factor is been calculated by graphical methods (Cotton, 1996). In this work a new thermodynamic expression for the Loss Factor (LF) is introduced, in order to improve applications to evaluate malfunctions in the first and intermediate stages of steam turbines. The new thermodynamic expression for the Loss Factor, is based on Second Law Analysis; and concepts like the internal parameter θ, and the dissipation temperature Td; (Royo, 1992). An Example of a steam turbine in a conventional power plant of 158 MW is analyzed by comparing a classical graphical method (ASME/ANSI PTC-6, 1970; and Cotton, 1993), and the proposed expression of the Loss Factor (LF). Special emphasis is made on the thermoeconomical deviations that could arise by an imprecise application of the Loss Factor Method, during an energy audit of the steam turbine internal parts.

Ferroelectric and ferromagnetic material having improved impedance matching

Abstract: The subject invention includes a composite material comprising a ferroelectric material and a ferromagnetic material having a loss factor (tan δ) for the composite material which includes a dielectric loss factor of the ferroelectric material and a magnetic loss factor of the ferromagnetic material. The composite material achieves the loss factor of from 0 to about 1.0 for a predetermined frequency range greater than 1 MHz. The ferroelectric material has a dielectric loss factor of from 0 to about 0.5 and the ferromagnetic material has a magnetic loss factor of from 0 to about 0.5 for the predetermined frequency range. The ferroelectric material is present in an amount from 10 to 90 parts by volume based on 100 parts by volume of the composite material and the ferromagnetic material is present in an amount from 10 to 90 parts by volume based upon 100 parts by volume of the composite material such that the amount of the ferroelectric material and the ferromagnetic material equals 100 parts by volume.

Dynamic damper and optical disk device

Abstract: PROBLEM TO BE SOLVED: To provide a dynamic damper reducing not only external vibration but also internal vibration, showing a steady effect from a low speed to a high speed, and manufactured in low cost with a simple construction, and an optical disk device provided with the same SOLUTION: An elastic part made of polymer elastic body having a loss factor tan δ under 03 at a room temperature and a balance plate part are integrated in this dynamic damper

Analysis of the Vibration Damping of Bonded Beams with a Single-Lap-Joint and Partial Dampers

Abstract: A theoretical analysis model for the lateral vibration of beams with a bonded single-lap-joint and partial layered dampers has been proposed in this paper. Both shear and normal forces acting along the interface between the elastic and viscoelastic layers were considered in the vibration analysis. The analytical results were comparable to those obtained by the modal strain energy method and the harmonic response analysis, which were based on a finite element model. The effects of the location and thickness of the partial dampers on the system loss factor ηs were studied. The characteristic variations of ηs, with changes of the modulus and loss factor of the viscoelastic layer in the lap joint part and partial dampers were also studied. Consequently, the geometrical and material conditions at maximizing ηs were suggested.

Expressions of the Loss Factor and the Vibration Transmissibility for the Anti-Resonances of Center-Driven Damped Beams Based on the Analysis of the Effective Mass.

Abstract: "Mechanical Impedance Method" is a measuring method of the loss factor of damped beam specimens widely adopted for practical use. In this method, an impedance head driven by a shaker is attached in the center of a beam. When the loss factor is evaluated for the anti-resonance, this method is considered to be a kind of double cantilever beam measurement. In order to confirm this, the equation for an Euler beam driven at the center is expanded with a linear combination of the natural modes of a double cantilever beam and the translational displacement. Thus, the equivalent mass of the natural modes is obtained. A frequency responce of mechanical impedance calculated using this equivalent mass is shown to be almost complete fitting with that calculated using free-free beam natural-modes. As one of remarkable applications of the modal expansion, an expression only using measurement in the center for estimating vibration transmissibility from the center to the tip is derived.

Physical mechanism and design of materials with electromagnetic wave absorption function

Abstract: The material with electromagnetic wave absorption function is an important military stealth material. Its physical mechanism is that it interacts with electromagnetic wave and the wave energy is changed into heat or other energy as much as possible. The important parameters for the wave absorption effects are electromagnetic loss factor, complex dielectric constant, complex magnetic conductivity. From simple equivalent electric circuit, the absorption mechanism of the material is analyzed ,the physical meaning of these parameters is explained and the design direction of the material is put forward qualitatively.It is illustrated from the results that the electromagnetic wave loss mechanisms are divided into resistance loss, dielectric loss, and magnetic loss. Both this losses and wave impedance matching are considered for design of the material. A good way to realize the goal of light weight, strong absorption, wide frequency band, absorbing microwave and infrared ray compatibly and other fine properties for the material is that it is made by more components composite especially nanoparticle polymer composite, combing three types′ losses and impedance matching. It is necessary that the absorption property is studied in microcosmic with solid state quantum mechanics to solve the problem of material design in theory.

High-frequency current suppression body using magnetic loss material exhibiting outstanding complex permeability characteristics

Abstract: In order to provide a magnetic loss material exhibiting outstanding high-frequency magnetic loss characteristics extremely effective in eliminating high-frequency transmission noise from very densely integrated electronic microcircuits such as semiconductor integrated circumference devices, together with a manufacturing method therefor and a high-frequency current suppression body wherein such is used, the present invention is a high-frequency current suppression body having a sheet shape comprising an adhesive layer or a pressure-sensitive adhesive layer (23) on at least one surface of a magnetic thin film (19). This magnetic thin film is a magnetic loss material consisting of M—X—Y, where M is at least one of Fe, Co, and Ni, X is at least one element other than M or Y, and Y is at least one of F, N, and O. The maximum value μ″max of the loss factor μ″ of the magnetic loss material exists in a frequency range of 100 MHz to 10 GHz. A relative bandwidth bwr is not greater than 200% where the relative bandwidth bwr is obtained by extracting a frequency bandwidth between two frequencies at which the value of μ″ is 50% of the maximum μ″max and normalizing the frequency bandwidth at the center frequency thereof.

拘束型磁性制振材の制振特性 : 第 1 報はりの曲げ振動解析に基づく損失係数の計算式の導出

Abstract: Viscoelastic damping materials with a constraining layer have excellent damping properties, but they have a weighty drawback that many works, such as preliminary treatment of adhesive surfaces and hold of viscoelastic damping materials till adhesive is completely stiffened, are required. To overcome this drawback, magnetic rubber dampers with a constraining layer (MRDC), which are composed of two layers-a magnetic rubber layer and a constraining steel layer-have been developed. They are easy to be fixed onto steel objects due to the attractive force of magnetic rubber layer. The damping property of MRDC is substantially caused by the friction loss which arises between the magnetic rubber layer and the steel object. The equation of loss factor of a beam with a sheet of MRDC is derived by taking the friction loss into account to analyze the flexural vibration of the beam.

Elastic wave control element using piezoelectric materials

Abstract: An elastic wave control element includes a piezoelectric material which is inserted into a propagation path for an elastic wave or installed in an oscillator to allow the elastic wave in a selected frequency to be damped, reflected, or transmitted. The piezoelectric material is provided with a pair of electrodes between which a negative capacitance circuit is connected to allow a loss factor of the negative capacitance circuit in a selected frequency or frequency band to be matched with a dielectric loss factor of the piezoelectric material.