Uniaxial Wave Propagation in a Viscoelastic Material Using Measured Material Properties

1968 ◽  
Vol 35 (3) ◽  
pp. 449-453 ◽  
Author(s):  
W. G. Knauss
Keyword(s):  
Wave Propagation ◽  
Viscoelastic Material ◽  
Material Properties ◽  
Material Characterization ◽  
Wave Speed ◽  
Initial Temperature ◽  
Initial Step ◽  
Shift Factor ◽  
Temperature Dependent ◽  
The Difference

The dynamic response of a long viscoelastic bar due to a step displacement at the end is considered. Neglecting geometric dispersion, the effect of realistic viscoelastic material properties is studied theoretically. The solution is obtained in the form of a Fourier sine integral, the convergence of which is studied numerically by piecewise integration to produce an alternating series. It is found that the initial step wave propagates with a high velocity corresponding to the glassy modulus of the material and its amplitude decays with time and distance along the rod. From a practical viewpoint the wave front may decay to immeasurable proportions and any measurable disturbance appears to travel thereafter, with a velocity which is smaller than the glassy wave speed. The effect of initial temperature is discussed. It is shown for thermorheologically simple materials that both the time and spatial variable are scaled by the same temperature dependent (shift) factor. As a consequence, the difference of wave propagation in hard and viscoelastic polymers is illustrated. It is also shown that limited material characterization is sufficient for certain dynamic problems. Comparison of the exact solution with two approximations is made.

scholarly journals A Novel Universal Approach for Temperature Correction on Frequency Domain Spectroscopy Curve of Transformer Polymer Insulation

Polymers ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1126 ◽  
Author(s):  
Jiefeng Liu ◽  
Xianhao Fan ◽  
Yiyi Zhang ◽  
Hanbo Zheng ◽  
Huilu Yao ◽  
...  
Keyword(s):  
Frequency Domain ◽  
Master Curve ◽  
Shift Factor ◽  
Temperature Correction ◽  
Universal Method ◽  
Temperature Dependent ◽  
Universal Approach ◽  
Different Types ◽  
Different Temperatures ◽  
The Difference

It is a fact that the frequency domain spectroscopy (FDS) curve at different temperatures can be corrected by the shift factor (αT) extracted from the master curve. However, the αT and master curve reported by previous works are distinctive due to the difference in the construction algorithm. Therefore, it is of great significance to report a universal approach for extracting αT. In this work, the unaged oil-immersed pressboards with different moisture content (mc%) are firstly prepared and selected as the research specimen. Then, the αT of FDS curves on the above pressboard is extracted based upon the master curve technique. The influence mechanism under the various test temperature (T) and mc% is therefore analyzed so as to establish a universal model for predicting the αT. The present findings reveal that the αT value extracted from FDS curves is both temperature-dependent and moisture-dependent. In addition, the predicted αT is not only suitable for temperature correction on FDS curve of same type pressboard with different insulation conditions (moisture contents and aging degrees), but also maintains considerable accuracy when applied to different types of pressboard. Therefore, the obtained conclusions will provide a universal method for temperature correction on FDS curve of transformer polymer insulation.

Stress-Wave Generation in a Temperature-Dependent Absorbing Solid by Impulsive Electromagnetic Radiation

1970 ◽  
Vol 37 (2) ◽  
pp. 339-344 ◽  
Author(s):  
G. A. Hegemier ◽  
F. Tzung
Keyword(s):  
Wave Propagation ◽  
Approximate Solution ◽  
Electromagnetic Radiation ◽  
Stress Wave ◽  
Material Properties ◽  
Mathematical Problem ◽  
Radiant Energy ◽  
Nonhomogeneous Medium ◽  
Temperature Dependent ◽  
Influence Of Temperature

An elastic, partially transparent solid, occupying the half space x > 0, is subjected to uniform impulsive electromagnetic radiation at the surface x = 0. The deposition of radiant energy over a finite absorption depth gives rise to a distributed heat source within the solid (thermal shock) which, in turn, dilatates the medium and generates a stress wave. In this paper, the nature of the stress-wave buildup in the absorption layer is studied for the case of a temperature-dependent solid, i.e., when material properties vary with temperature. The mathematical problem is one of wave propagation in a nonhomogeneous medium. An approximate solution to the posed problem is developed which readily exhibits the influence of temperature. Error bounds are provided. The results are illustrated by a numerical example.

scholarly journals Viscoelastic Material Characterization: A Realistic Approach to Stress Analysis

2021 ◽  
pp. 119-128
Author(s):  
Amor Zapanta ◽  
Jefferson Talledo
Keyword(s):  
Viscoelastic Material ◽  
Material Properties ◽  
Material Characterization ◽  
Time History ◽  
Thermal Conditions ◽  
Slow Cool ◽  
Test Sample ◽  
Compound Material ◽  
Semiconductor Packages ◽  
Viscoelastic Material Characterization

This paper presents an advanced method in materials characterization for the mold compound material in semiconductor packages to build models that can technically explain the actual warpage or stress observations under different thermal conditions and time history. In the study, the mold compound material characterization was conducted using Dynamic Mechanical Analyzer (DMA) followed by curve fitting to obtain parameters for the computer modeling input requirement. Thermo-mechanical modeling using viscoelastic material properties was conducted on a bi-material test sample model. Results showed that the new characterized viscoelastic material properties exhibited dependence on time and temperature. Slow cool down from post mold cure (PMC) to room temperature resulted in lower warpage or stress. This observed rate dependent response was explained using viscoelastic material properties in contrast to the usual linear elastic material simplification. Thus, a realistic result from stress or warpage analysis could be achieved using viscoelastic material characterization.

Temperature-Dependent Logic Failure in a GaAs Power Amplifier-Duplexer Module Caused by a Subtle Parasitic Schottky Diode

2014 ◽  
Author(s):  
Rose Emergo ◽  
Steve Brockett ◽  
Pat Hamilton
Keyword(s):  
Power Amplifier ◽  
Schottky Diode ◽  
Production Test ◽  
Temperature Dependent ◽  
Cold Temperatures ◽  
Collector Junction ◽  
Power Mode ◽  
The Difference ◽  
Base Contact ◽  
Single Power

Abstract A single power amplifier-duplexer device was submitted by a customer for analysis. The device was initially considered passing when tested against the production test. However, further electrical testing suggested that the device was stuck in a single power mode for a particular frequency band at cold temperatures only. This paper outlines the systematic isolation of a parasitic Schottky diode formed by a base contactcollector punch through process defect that pulled down the input of a NOR gate leading to the incorrect logic state. Note that this parasitic Schottky diode is parallel to the basecollector junction. It was observed that the logic failure only manifested at colder temperatures because the base contact only slightly diffused into the collector layer. Since the difference in the turn-on voltages between the base-collector junction and the parasitic Schottky diode increases with decreasing temperature, the effect of the parasitic diode is only noticeable at lower temperatures.

scholarly journals Action and Entropy in Heat Engines: An Action Revision of the Carnot Cycle

Entropy ◽  
2021 ◽  
Vol 23 (7) ◽  
pp. 860
Author(s):  
Ivan R. Kennedy ◽  
Migdat Hodzic
Keyword(s):  
Heat Engine ◽  
Working Fluid ◽  
Field Energy ◽  
Carnot Cycle ◽  
Gibbs Potential ◽  
Atmospheric Gases ◽  
Temperature Dependent ◽  
Expansion Phase ◽  
Heat Engines ◽  
The Difference

Despite the remarkable success of Carnot’s heat engine cycle in founding the discipline of thermodynamics two centuries ago, false viewpoints of his use of the caloric theory in the cycle linger, limiting his legacy. An action revision of the Carnot cycle can correct this, showing that the heat flow powering external mechanical work is compensated internally with configurational changes in the thermodynamic or Gibbs potential of the working fluid, differing in each stage of the cycle quantified by Carnot as caloric. Action (@) is a property of state having the same physical dimensions as angular momentum (mrv = mr2ω). However, this property is scalar rather than vectorial, including a dimensionless phase angle (@ = mr2ωδφ). We have recently confirmed with atmospheric gases that their entropy is a logarithmic function of the relative vibrational, rotational, and translational action ratios with Planck’s quantum of action ħ. The Carnot principle shows that the maximum rate of work (puissance motrice) possible from the reversible cycle is controlled by the difference in temperature of the hot source and the cold sink: the colder the better. This temperature difference between the source and the sink also controls the isothermal variations of the Gibbs potential of the working fluid, which Carnot identified as reversible temperature-dependent but unequal caloric exchanges. Importantly, the engine’s inertia ensures that heat from work performed adiabatically in the expansion phase is all restored to the working fluid during the adiabatic recompression, less the net work performed. This allows both the energy and the thermodynamic potential to return to the same values at the beginning of each cycle, which is a point strongly emphasized by Carnot. Our action revision equates Carnot’s calorique, or the non-sensible heat later described by Clausius as ‘work-heat’, exclusively to negative Gibbs energy (−G) or quantum field energy. This action field complements the sensible energy or vis-viva heat as molecular kinetic motion, and its recognition should have significance for designing more efficient heat engines or better understanding of the heat engine powering the Earth’s climates.

The interaction of bovine milk caseins with the detergent sodium dodecyl sulphate. II. The effect of detergent binding on spectral properties of caseins

1970 ◽  
Vol 37 (2) ◽  
pp. 259-267 ◽  
Author(s):  
G. C. Cheeseman ◽  
Dorothy J. Knight
Keyword(s):  
Sodium Dodecyl Sulphate ◽  
Sodium Dodecyl ◽  
Bovine Milk ◽  
Difference Spectrum ◽  
Temperature Dependent ◽  
Difference Spectra ◽  
Negative Change ◽  
Tryptophan Residues ◽  
Hydrophobic Binding ◽  
The Difference

SummaryThe dissociation of casein aggregates by the detergent sodium dodecyl sulphate (SDS) gave rise to difference spectra and these spectra were characteristic for each of the different types of casein. Increase in absorption by the chromophore groups, tyrosine and tryptophan, when αs1- and β-casein aggregates were dissociated indicated binding of the detergent at regions of the molecule containing these residues. A decrease in absorption when κ-casein was dissociated indicated that the tyrosine and tryptophan residues were not in the region of the molecule to which the detergent was bound and that in the κ-casein aggregate these residues were in a more hydrophobic environment. Peaks on the difference spectra were obtained at 280 and 288 nm for αs1-casein and 284 and 291 nm for β-casein and troughs at 278 and 286 nm for κ-casein. The difference spectrum reached a maximum value when the αsl- and β-casein aggregates were dissociated and the further binding of SDS did not alter this value. The large negative change in the difference spectrum of κ-casein did not occur until after most of the aggregates were dissociated and did not reach a maximum until binding with SDS was complete. The value obtained for ΔOD was found to be temperature-dependent for β-casein-SDS interaction, but not for αs1- and κ-casein. Changes in spectra were also observed when αs1- and κ-casein interacted to form aggregates. The data obtained confirmed the importance of hydrophobic binding in casein aggregate formation and indicated the possible involvement of tyrosine and tryptophan residues in this binding.

Magnetotelluric static shift: Estimation and removal using the cokriging method

Geophysics ◽  
2007 ◽  
Vol 72 (1) ◽  
pp. F25-F34 ◽  
Author(s):  
Benoit Tournerie ◽  
Michel Chouteau ◽  
Denis Marcotte
Keyword(s):  
Apparent Resistivity ◽  
A Priori ◽  
Shift Factor ◽  
Static Shift ◽  
Geostatistical Model ◽  
Data Set ◽  
Resistivity Sounding ◽  
The Difference ◽  
Cross Variogram

We present and test a new method to correct for the static shift affecting magnetotelluric (MT) apparent resistivity sounding curves. We use geostatistical analysis of apparent resistivity and phase data for selected periods. For each period, we first estimate and model the experimental variograms and cross variogram between phase and apparent resistivity. We then use the geostatistical model to estimate, by cokriging, the corrected apparent resistivities using the measured phases and apparent resistivities. The static shift factor is obtained as the difference between the logarithm of the corrected and measured apparent resistivities. We retain as final static shift estimates the ones for the period displaying the best correlation with the estimates at all periods. We present a 3D synthetic case study showing that the static shift is retrieved quite precisely when the static shift factors are uniformly distributed around zero. If the static shift distribution has a nonzero mean, we obtained best results when an apparent resistivity data subset can be identified a priori as unaffected by static shift and cokriging is done using only this subset. The method has been successfully tested on the synthetic COPROD-2S2 2D MT data set and on a 3D-survey data set from Las Cañadas Caldera (Tenerife, Canary Islands) severely affected by static shift.

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