Showing papers on "Loss factor published in 1979"
TL;DR: In this paper, the linear power balance equations for a two coupled plate model were used to determine the plate loss factors and the coupling loss factors in situ, and injected power at points chosen at random was measured.
Abstract: Inversion of the linear power balance equations for a two coupled plate model is used to determine the plate loss factors and the coupling loss factors in situ. To accomplish the determinations, injected power at points chosen at random was measured. To ensure effective statistical independence of modes, each plate was driven at five different points in sequence and the response of both plates in each case was determined at ten randomly chosen points. Good agreement is obtained between the predicted and measured coupling loss factors, and between the in situ loss factors and loss factors determined for each plate separately also in steady state from power injection measurements. Loss factors determined by transient decay methods are consistently lower than those determined by either steady‐state method. During reverberant decay, the more lightly damped modes predominate, giving rise to an apparent loss factor which is significantly less than the steady‐state loss factor determined under conditions of esse...
31 citations
TL;DR: In this paper, the propagation constants of an extensional acoustic wave are determined by exciting one end of a strip of material while the other end is suspended under constant tension. But the results are limited to a frequency range of 100 Hz to 40 kHz, depending on the extensional wave velocity and attenuation.
Abstract: A progressive wave apparatus featuring an automated data processor is described. The apparatus accurately determines the propagation constants of an extensional acoustic wave by exciting one end of a strip of material while the other end is suspended under constant tension. The apparatus is capable of making measurements in the frequency range of 100 Hz to 40 kHz, depending on the extensional wave velocity and attenuation in the material. As illustrations of the technique, measurements were made on several rubber compounds of different polymer type and compounding ingredients. Extensional sound speed, attenuation, modulus, and loss factor were determined over a frequency range of 1–10 kHz and a temperature range of 4°–47°C. Applying the time‐temperature superposition principle to the data, master curves were constructed and WLF shift constants were determined. The apparatus was found to be a fast and reliable method to determine the dynamic viscoelastic constants.
21 citations
TL;DR: In this article, a sample holder is described for use with a Q-Meter to measure the dielectric properties of materials, including provision for controlling the temperature of the sample.
Abstract: Anew sample holder is described for use with a Q-Meter to measure the dielectric properties of materials. It includes provision for controlling the temperature of the dielectric sample. It also is equipped with two cali-brated, variable air capacitors—one for measurements to determine the dielectric constant, and the other for measurements that determine the loss tangent. The im-proved design eliminates possible errors in determining the loss tangent, loss factor, and conductivity that can be caused by residual and lead inductance at the higher frequencies. Results of measurements between 10 and 40 MHz on samples of hard red winter wheat of different moisture contents are presented and discussed. Mea-sured values of the dielectric constant of wheat were somewhat dependent upon electrode spacing, because kernel dimensions were appreciable in relation to inter-electrode distances.
17 citations
TL;DR: In this paper, a simple method for measuring mechanical input power to a structure by direct analogue multiplication and integration of force and velocity signals is described, and the influence of phase errors is controlled through measurement of both the real and the imaginary power components.
2 citations
TL;DR: In this paper, a theoretical development for damping calculation has been carried out by considering shear force, normal force and bending moment for both face and core layers for both cantilever beam.
Abstract: The natural vibration damping of sandwich cantilever beam has been investigated. A theoretical development for damping calculation has been carried out by considering shear force, normal force and bending moment for both face and core layers. The ratio of thickness between the face and core layer is not constrained. Experimental results show that theoretical calculation is quite satisfied. When the elastic modulus of the core layer is larger than that of the face layer, a simpler and more convenient formula has been developed to calculate the loss factor.