scholarly journals Influence of the Static Pre-Stress in Micro-Viscothermoelastic Resonators Based on Dual-Phase-Lagging Heat Conduction

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Najat A. Alghamdi ◽  
Hamdy M. Youssef
Keyword(s):  
Heat Conduction ◽  
Energy Dissipation ◽  
Thermal Behavior ◽  
Quality Factor ◽  
Analytical Model ◽  
Relaxation Times ◽  
Mechanical Relaxation ◽  
Length Scale ◽  
Dual Phase ◽  
Quality Factors

Thermal and mechanical relaxation times play vital roles in the values of the quality factor of micro/nanoresonators. They can control the energy dissipation across the coupling of mechanical and thermal behavior. In this paper, we introduce an analytical model that considers a pre-stress in a micro-viscothermoelastic resonator to modify the thermal and mechanical relaxation times and thus higher the quality factor. The impacts of length scale and static pre-stress on the quality factor have been discussed. The model expects that significant improvement in terms of quality factors is possible by tuning the pre-stress and the thermal and mechanical relaxation times parameters, and the isothermal value of frequency have significant effects on the thermal quality factor of the resonators.

scholarly journals The influence of the static-pre-stress and mechanical damage variable in the thermal quality factor of two-temperature viscothermoelastic resonators

2020 ◽  
Vol 12 (6) ◽  
pp. 168781402093045 ◽  
Author(s):  
Hamdy M Youssef ◽  
Mohammed W Al-Hazmi
Keyword(s):  
Relaxation Time ◽  
Quality Factor ◽  
Relaxation Times ◽  
Thermal Relaxation ◽  
Mechanical Damage ◽  
Damage Variable ◽  
Mechanical Relaxation ◽  
Length Scale ◽  
Quality Factors ◽  
Two Temperature

The mechanical damage variable, as well as the thermal and mechanical relaxation times, plays essential roles in the thermal quality factor of the resonators, where controls energy damping through the coupling of mechanical and thermal behavior. In this article, we developed a mathematical model in which a static-pre-stress and mechanical damage variable in the context of a two-temperature viscothermoelasticity of silicon resonator has been considered. The effects of static-pre-stress, thermal relaxation time, mechanical relaxation time, mechanical damage variable, isothermal frequency, and length-scale on the quality factor have been discussed in the context of a one-temperature and two-temperature models. The model predicts that significant improvement in terms of quality factors is possible by tuning the static-pre-stress, isothermal frequency, and length-scale of the resonator. Moreover, the thermal and mechanical relaxation times and the mechanical damage variable have impacts on the thermal quality factor.

Nonhomogeneous Dual-Phase-Lag Heat Conduction Problem: Analytical Solution and Select Case Studies

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Simon Julius ◽  
Boris Leizeronok ◽  
Beni Cukurel
Keyword(s):  
Heat Flux ◽  
Heat Conduction ◽  
Analytical Solution ◽  
Heat Generation ◽  
Integral Transform ◽  
Heat Conduction Problem ◽  
Relaxation Times ◽  
Hyperbolic Heat Conduction ◽  
Phase Lag ◽  
Dual Phase

Finite integral transform techniques are applied to solve the one-dimensional (1D) dual-phase heat conduction problem, and a comprehensive analysis is provided for general time-dependent heat generation and arbitrary combinations of various boundary conditions (Dirichlet, Neumann, and Robin). Through the dependence on the relative differences in heat flux and temperature relaxation times, this analytical solution effectively models both parabolic and hyperbolic heat conduction. In order to demonstrate several exemplary physical phenomena, four distinct cases that illustrate the wavelike heat conduction behavior are presented. In the first model, following an initial temperature spike in a slab, the thermal evolution portrays immediate dissipation in parabolic systems, whereas the dual-phase solution depicts wavelike temperature propagation—the intensity of which depends on the relaxation times. Next, the analysis of periodic surface heat flux at the slab boundaries provides evidence of interference patterns formed by temperature waves. In following, the study of Joule heating driven periodic generation inside the slab demonstrates that the steady-periodic parabolic temperature response depends on the ratio of pulsatile electrical excitation and the electrical resistivity of the slab. As for the dual-phase model, thermal resonance conditions are observed at distinct excitation frequencies. Building on findings of the other models, the case of moving constant-amplitude heat generation is considered, and the occurrences of thermal shock and thermal expansion waves are demonstrated at particular conditions.

scholarly journals Vibration of circular micro-ceramic (Si3N4) plate resonators in the context of the generalized viscothermoelastic dual-phase-lagging theory

2019 ◽  
Vol 11 (11) ◽  
pp. 168781401988948 ◽  
Author(s):  
Najat A Alghamdi
Keyword(s):  
Aspect Ratio ◽  
Boundary Conditions ◽  
Laplace Transform ◽  
Circular Plate ◽  
Plate Theory ◽  
Relaxation Times ◽  
Mechanical Relaxation ◽  
Dual Phase ◽  
Governing Equations ◽  
Thermally Conducting

In this article, the analysis and numerical results are represented for the thermoelastic of an isotropic homogeneous, thermally conducting, Kelvin–Voigt-type circular micro-plate in the context of Kirchhoff’s Love plate theory of generalized viscothermoelasticity based on the dual-phase-lagging model. The governing equations are obtained for the generalized dual-phase-lagging model and coupled viscothermoelastic plates. The scaled viscothermoelasticity has been illustrated in the case of the circular plate and the axisymmetric circular plate for an aspect ratio for clamped boundary conditions. Laplace transform has been applied, and its inversions have been calculated numerically by using the Tzou method. The results have been carried out for the ceramic (Si3N4). It is noted that the temperature increment and lateral deflection are significantly affected by the time, the width, the thickness, and the mechanical relaxation times of the material.

Quality Factors of Crystalline Semiconductor Nanocomposite Resonators

2011 ◽  
Author(s):  
Puroorava Chakravarthy ◽  
Gang Li
Keyword(s):  
Molecular Dynamics ◽  
Energy Dissipation ◽  
Quality Factor ◽  
Material Properties ◽  
Quality Factors ◽  
Key Factors ◽  
Nano Scale ◽  
Crystalline Semiconductor ◽  
Bulk Matrix ◽  
Semiconductor Nanocomposite

A nanocomposite can generally be regarded as a solid combining a bulk matrix and nano-scale phases. The phases can be nanoparticles, nanowires, nanoplatelets and etc. The addition of nanosized phases into the bulk matrix can lead to significantly different material properties compared to their macrocomposite counterparts. In this work, we investigate the characteristics of energy dissipation in nanocomposite resonators. By using classical molecular dynamics (MD), we calculate the quality factors of layered and fibrous crystalline semiconductor nanocomposite resonators. Key factors that determine the quality factor of the nanocomposite resonators are identified and analyzed.

Quality Factor Optimization Techniques for MEMS Gyroscopes of Frame Structures

2012 ◽  
Vol 590 ◽  
pp. 173-178
Author(s):  
Chao Wei Si ◽  
Guo Wei Han ◽  
Jin Ning ◽  
Wei Wei Zhong ◽  
F.H. Yang
Keyword(s):  
Energy Dissipation ◽  
Quality Factor ◽  
Optimization Techniques ◽  
Frame Structure ◽  
Frame Structures ◽  
Mass Ratio ◽  
Quality Factors ◽  
Quadrature Error ◽  
Factor Ratio ◽  
Mems Gyroscopes

MEMS gyroscopes of frame structures are capable of isolating the quadrature error between the drive motion and the sense motion, which is often utilized in current gyroscope design. But quality factors of previous reported gyroscopes of frame structure are hardly over 1000, which are far more less than that of gyroscopes manufactured before with only one mass block for sensing and driving. Although the effectiveness of isolating quadrature errors is proved, the sensitivity is decreased as well as the power consumption is increased for higher drive voltage. Reasons why MEMS gyroscopes of frame structure has low quality factors is pointed out here with a method of anchor loss mechanism, and the energy dissipation is modeled with a 2 degree of vibration system, which tells the relationship between the mass ratio of the inner mass and the outer frame and the spring factor ratio for supporting masses, and the quality factor assess techniques is proposed here. Therefore the admissible parameters of the mass ratio and the spring factor ratio are given, which makes MEMS gyroscopes of frame structures have advantages of quadrature error isolation as well as high sensitivity. In the end, gyroscopes with optimized parameters and reported parameters are manufactured on SOI wafer, and variations of the quality factors as expected proves the rationality of the proposed energy dissipation model in this paper. For Process limitations, quality factors of gyroscopes of frame structures are improved lower than expected, but far more improved than previous reported gyroscopes, and better results should be realized in more mature and stabilized process.

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