Wave propagation in a generalized piezothermoelastic rotating bar of circular cross section

2015 ◽  
Vol 11 (2) ◽  
pp. 216-237 ◽  
Author(s):  
Rajendran Selvamani ◽  
Palaniyandi Ponnusamy
Keyword(s):  
Wave Propagation ◽  
Cross Section ◽  
Rotational Speed ◽  
Relaxation Times ◽  
Circular Cross Section ◽  
Thermal Relaxation ◽  
Wave Number ◽  
Content Type ◽  
Mechanical Coupling ◽  
Thermal Relaxation Times

Purpose – The purpose of this paper is to study the wave propagation in a generalized piezothermoelastic rotating bar of circular cross-section using three-dimensional linear theory of elasticity. Design/methodology/approach – A mathematical model is developed to study the wave propagation in a generalized piezothermelastic rotating bar of circular cross-section by using Lord-Shulman (LS) and Green-Lindsay (GL) theory of thermoelasticity. After developing the formal solution of the mathematical model consisting of partial differential equations, the frequency equations have been derived by using the thermally insulated/isothermal and electrically shorted/charge free boundary conditions prevailing at the surface of the circular cross-sectional bar. The roots of the frequency equation are obtained by using the secant method, applicable for complex roots. Findings – In order to include the time requirement for the acceleration of the heat flow and the coupling between the temperature and strain fields, the analytical terms have been derived for the non-classical thermo-elastic theories, LS and GL theory. The computed physical quantities such as thermo-mechanical coupling, electro-mechanical coupling, frequency shift, specific loss and frequency have been presented in the form of dispersion curves. From the graphical patterns of the structure, the effect of thermal relaxation times and the rotational speed as well as the anisotropy of the of the material on the various considered wave characteristics is more significant and dominant in the flexural modes of vibration. The effect of such physical quantities provides the foundation for the construction of temperature sensors, acoustic sensor and rotating gyroscope. Originality/value – In this paper, the influence of thermal relaxation times and rotational speed on the wave number with thermo-mechanical coupling, electro-mechanical coupling, frequency shift, specific loss and frequency has been observed and are presented as dispersion curves. The effect of thermal relaxation time and rotational speed on wave number for the case of generalized piezothermoelastic material of circular cross-section was never reported in the literature. These results are new and original.

Analysis of Deep Levels in GaAs Detector Diodes Using Impedance Spectroscopy

1993 ◽  
Vol 302 ◽  
Author(s):  
C Eiche ◽  
M Fiederle ◽  
J Weese ◽  
D Maier ◽  
D Ebling ◽  
...  
Keyword(s):  
Cross Section ◽  
Regularization Method ◽  
Capture Cross Section ◽  
Relaxation Times ◽  
Thermal Relaxation ◽  
Simulated Data ◽  
Deep Levels ◽  
Admittance Spectroscopy ◽  
Thermal Relaxation Times ◽  
Level 2

ABSTRACTImpedance or admittance spectroscopy has been shown to be a very convenient tool for the investigation of deep levels in semiconductor junctions. At constant temperature a frequency sweep is performed. After that the impedance signal is analysed by a regularization method based on Tikhonov regularization in order to obtain the thermal relaxation times of the deep levels present in the junction. The high resolution of the regularization method in comparison to conventional techniques is demonstrated using simulated data. The temperature dependence of the thermal relaxation times provides information about the properties of the deep levels such as activation energy or capture cross section. Two donor levels with activation energies dE1 =0.58 eV and dE2 =0.68 eV are observed in our detector diodes. It can be shown that the concentration of level 2 is increased after irradiation.

The thermomechanical response of a poroelastic medium with two thermal relaxation times

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Ibrahim Abbas ◽  
Aatef Hobiny
Keyword(s):  
Finite Element ◽  
Design Methodology ◽  
Relaxation Times ◽  
Thermal Relaxation ◽  
The Finite Element Method ◽  
Poroelastic Medium ◽  
Content Type ◽  
One Dimensional ◽  
Thermal Relaxation Times ◽  
Element Approach

Purpose–The purpose of this paper is to study the wave propagation in a porous medium through the porothermoelastic process using the finite element method (FEM).Design/methodology/approachOne-dimensional (1D) application for a poroelastic half-space is considered. Due to the complex governing equation, the finite element approach has been adopted to solve these problems.FindingsThe effect of porosity and thermal relaxation times in a porothermoelastic material was investigated.Originality/valueThe numerical results for stresses, displacements and temperatures for the solid and the fluid are represented graphically. This work will enable future investigators to have the insight of nonsimple porothermoelasticity with different phases in detail.

Electromagnetic wave propagation in a chiroplasma-filled waveguide

1999 ◽  
Vol 62 (1) ◽  
pp. 87-94 ◽  
Author(s):  
J. GONG
Keyword(s):  
Wave Propagation ◽  
Electromagnetic Wave ◽  
Cross Section ◽  
Electromagnetic Waves ◽  
Electromagnetic Wave Propagation ◽  
Propagation Constant ◽  
Circular Cross Section ◽  
Propagation Characteristics ◽  
Waveguide Modes ◽  
The Family

A dispersion equation is derived for a cylindrical waveguide of circular cross-section partially filled with chiroplasma. The propagation characteristics of electromagnetic waves in the family of waveguide modes are studied. The dispersion curves are given. It is found that the propagation constant changes almost linearly with the chirality admittance for the parameters that we choose, and increases with increasing filled area.

Elastic–plastic deformation and residual stresses in helical springs

2019 ◽  
Vol 16 (3) ◽  
pp. 448-475
Author(s):  
Vladimir Kobelev
Keyword(s):  
Residual Stresses ◽  
Closed Form ◽  
Cross Section ◽  
Circular Cross Section ◽  
Content Type ◽  
Closed Form Solutions ◽  
Helical Springs ◽  
First Case ◽  
Setting Process ◽  
The Wire

Purpose The purpose of this paper is to develop the method for the calculation of residual stress and enduring deformation of helical springs. Design/methodology/approach For helical compression or tension springs, a spring wire is twisted. In the first case, the torsion of the straight bar with the circular cross-section is investigated, and, for derivations, the StVenant’s hypothesis is presumed. Analogously, for the torsion helical springs, the wire is in the state of flexure. In the second case, the bending of the straight bar with the rectangular cross-section is studied and the method is based on Bernoulli’s hypothesis. Findings For both cases (compression/tension of torsion helical spring), the closed-form solutions are based on the hyperbolic and on the Ramberg–Osgood material laws. Research limitations/implications The method is based on the deformational formulation of plasticity theory and common kinematic hypotheses. Practical implications The advantage of the discovered closed-form solutions is their applicability for the calculation of spring length or spring twist angle loss and residual stresses on the wire after the pre-setting process without the necessity of complicated finite-element solutions. Social implications The formulas are intended for practical evaluation of necessary parameters for optimal pre-setting processes of compression and torsion helical springs. Originality/value Because of the discovery of closed-form solutions and analytical formulas for the pre-setting process, the numerical analysis is not necessary. The analytical solution facilitates the proper evaluation of the plastic flow in torsion, compression and bending springs and improves the manufacturing of industrial components.

Measuring compression caused by garments

2018 ◽  
Vol 30 (2) ◽  
pp. 138-151
Author(s):  
Brett Ellis ◽  
Erin Kirkpatrick ◽  
Sonal Kothari Phan ◽  
Stacy Imler ◽  
Haskell Beckham
Keyword(s):  
Cross Section ◽  
Performance Metrics ◽  
Angular Position ◽  
Circular Cross Section ◽  
Compression Garment ◽  
Compression Garments ◽  
Elliptical Cross ◽  
Content Type ◽  
Pressure Mapping ◽  
Tensile Data

Purpose Stretch fabrics are employed to create compression in garments for medical, sports, and fitness applications. Although potential correlations between wearing compression garments and physiological or performance metrics have been studied, such correlations require knowledge of the actual compression caused by garments. The purpose of this paper is to demonstrate, compare, and contrast different methods for measuring compression delivered by an exemplar compression garment. Design/methodology/approach The exemplar compression garment is a plain jersey knit maternity band. The compression delivered by this garment was determined via three different methods – Tekscan pressure mapping system, Hohenstein Measurement System (HOSY), and a fabric-based analytical model employing uniaxial fabric tensile data. Findings HOSY and the fabric-based model, assuming a circular cross section for the garment, provided comparable results for compression versus garment height. However, these methods did not capture the varying compression delivered at different transverse locations when the subject was noncircular in cross section. Assuming an elliptical cross section, the fabric-based model predicted results that were comparable to those measured by the Tekscan system: for example, compressions were approximately 130-160 percent greater at the hip, and approximately 60-100 percent lower at the posterior, than HOSY revealed. Further, the Tekscan system allows the effect of movement on compression to be captured. Originality/value This paper compares and contrasts three compression measurement methods and demonstrates the importance of angular position and height dependencies. Further, the fabric-based model is presented as a tool to assist design of compression garments.

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