scholarly journals EXPONENTIAL STABILITY OF LAMINATED BEAM WITH CONSTANT DELAY FEEDBACK

2021 ◽  
Vol 26 (4) ◽  
pp. 566-581
Author(s):  
Kassimu Mpungu ◽  
Tijani A. Apalara
Keyword(s):  
Wave Propagation ◽  
Exponential Stability ◽  
Propagation Speed ◽  
Transverse Displacement ◽  
Structural Damping ◽  
Constant Delay ◽  
Laminated Beams ◽  
Laminated Beam ◽  
Delay Term ◽  
Wave Propagation Speed

In this article, we consider a system of laminated beams with an internal constant delay term in the transverse displacement. We prove that the dissipation through structural damping at the interface is strong enough to exponentially stabilize the system under suitable assumptions on delay feedback and coefficients of wave propagation speed.

Influence of the applied pressure of the transducer on the propagation speed of the ultrasonic wave in wood

Holzforschung ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Edgar V.M. Carrasco ◽  
Rejane C. Alves ◽  
Mônica A. Smits ◽  
Vinnicius D. Pizzol ◽  
Ana Lucia C. Oliveira ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Applied Pressure ◽  
Pressure Gauge ◽  
Eucalyptus Grandis ◽  
Propagation Speed ◽  
Ultrasonic Waves ◽  
Ultrasonic Speed ◽  
Wave Propagation Speed ◽  
Propagation Technique ◽  
Non Destructive

Abstract The non-destructive wave propagation technique is used to estimate the wood’s modulus of elasticity. The propagation speed of ultrasonic waves is influenced by some factors, among them: the type of transducer used in the test, the form of coupling and the sensitivity of the transducers. The objective of the study was to evaluate the influence of the contact pressure of the transducers on the ultrasonic speed. Ninety-eight tests were carried out on specimens of the species Eucalyptus grandis, with dimensions of 120 × 120 × 50 mm. The calibration of the pressure exerted by the transducer was controlled by a pressure gauge using a previously calibrated load cell. The robust statistical analysis allowed to validate the experimental results and to obtain consistent conclusions. The results showed that the wave propagation speed is not influenced by the pressure exerted by the transducer.

scholarly journals К теории рассеяния Мандельштама-Бриллюэна в плазменном слое

2020 ◽  
Vol 128 (1) ◽  
pp. 98
Author(s):  
С.А. Двинин ◽  
Д.К. Солихов ◽  
Ш.С. Нурулхаков
Keyword(s):  
Wave Propagation ◽  
Pump Wave ◽  
Plasma Layer ◽  
Brillouin Scattering ◽  
Propagation Speed ◽  
Local Source ◽  
Arbitrary Angle ◽  
Perturbation Amplitude ◽  
Wave Propagation Speed ◽  
Over Time

The evolution of a perturbation from a local source for Mandel'shtam-Brillouin scattering in a plasma layer with unlimited length is calculated. Perturbation over time in this case can either leave the scattering region through one of the two boundaries, or propagate along the layer at a speed below sound wave propagation speed, with an exponential growth, or a fall in perturbation amplitude. In the particular case of strictly backward scattering (the scattering angle is π), this propagation velocity is zero. The paper calculates the threshold instability fields and the instability increments, taking into account both convective losses and collisional attenuation of waves. It is shown that the instability threshold for scattering at an arbitrary angle can be lower than for strictly backwards scattering and when the threshold is exceeded by the intensity of the pump wave; the scattering increment at an angle can also be higher than the increment for backscattering. When the threshold is greatly exceeded, the convective losses can be neglected, and the largest increment is observed for backward scattering.

Analytical and Optimization Study of Propagation and Reduction of Wave in Granular Sand by DEM Method

2021 ◽  
Author(s):  
Amin Moslemi Petrudi ◽  
Masoud Rahmani
Keyword(s):  
Wave Propagation ◽  
Particle Density ◽  
Propagation Speed ◽  
Granular Soils ◽  
Discrete Elements ◽  
Factors Affecting ◽  
Interparticle Force ◽  
Optimization Study ◽  
Solution Methods ◽  
Wave Propagation Speed

In this research, the discrete element method has been used to analyze wave propagation and to investigate the factors affecting wave reduction in granular soils. The method of discrete elements is important because of the possibility of preparing completely similar specimens and examining the effect of changes in a certain parameter on the Behavior of the specimens. This method also provides an understanding of the changes that have occurred at the micro-scale of granular materials that are not achievable with other laboratory and numerical methods. To model the specimens, a set of disks with specific granulation has been used for two-dimensional studies. PFC 2D software has been used to perform simulations and related analyzes such as interparticle force. The DEM code in MATLAB is used to check the wave depreciation. In this research, the optimization process was performed using experimental data and the Taguchi method using the DEM method. The results of this study show that there is a direct relationship between the number of particle set contacts and the wave propagation speed. Also, material properties such as particle density are the most important parameters affecting wave velocity. The results of the method (DEM) are done with PFC 2D software and a comparison between the results of this method with the solution methods used by other researchers is shown to be a good match.

Axial force measurement for U-bolt using wave propagation speed monitoring

2016 ◽  
Vol 140 (4) ◽  
pp. 3002-3002
Author(s):  
Gyungmin Toh ◽  
Dongki Min ◽  
Jaehong Lee ◽  
Junhong Park
Keyword(s):  
Wave Propagation ◽  
Axial Force ◽  
Force Measurement ◽  
Propagation Speed ◽  
Wave Propagation Speed

Extension of Campbell's Major Resonance With Experimental Demonstration

2013 ◽  
Vol 135 (5) ◽  
Author(s):  
Robert P. Czachor
Keyword(s):  
Wave Propagation ◽  
Rotational Velocity ◽  
Propagation Speed ◽  
Experimental Demonstration ◽  
Adjacent Structure ◽  
Component Test ◽  
Turbine Disc ◽  
Wave Propagation Speed ◽  
Trans Asme ◽  
Classic Paper

The interaction of vibratory traveling waves in rotating and stationary axisymmetric components is examined. In the most general case, a resonance can occur when the wave propagation speed in a first structure is equal in magnitude and direction to the rotational velocity of an adjacent structure. When a backward wave in a rotor appears stationary, a major resonance, as discussed in Wilfred Campbell's classic paper (Campbell, W., 1924, “The Protection of Steam Turbine Disc Wheels from Axial Vibrations,” Trans ASME, 46, pp. 31–160), results. A related resonance has been observed when the wave propagation speed in the stator is equal to the physical speed of the adjacent rotor. A third mechanism is derived for resonance between a wave in rotor 1 and a co- or counter-rotating rotor 2. Description of a component test which demonstrated this final phenomenon is provided.

scholarly journals Uniform stability for a type III thermoelastic laminated beam with structural damping

2022 ◽  
Author(s):  
Fayssal Djellali
Keyword(s):  
Heat Flux ◽  
Exponential Stability ◽  
Semigroup Theory ◽  
Stability Result ◽  
Uniform Stability ◽  
Well Posedness ◽  
Structural Damping ◽  
Laminated Beam ◽  
Wave Speeds ◽  
Lack Of Exponential Stability

In this work, we consider a thermoelastic laminated beam with structural damping, where the heat flux is given by Green and Naghdi theories. We establish the well-posedness of the system using semigroup theory. Moreover, under the condition of equal wave speeds, we prove an exponential stability result for the considered system. In the case of lack of exponential stability we show that the solution decays polynomially.

Asymptotic stability for a laminated beam with structural damping and infinite memory

2020 ◽  
Vol 25 (10) ◽  
pp. 1979-2004 ◽  
Author(s):  
Wenjun Liu ◽  
Xiangyu Kong ◽  
Gang Li
Keyword(s):  
Wave Propagation ◽  
Relaxation Function ◽  
Rotation Angle ◽  
Structural Damping ◽  
Laminated Beam ◽  
Infinite Memory ◽  
One Dimensional ◽  
Special Cases ◽  
Lack Of Exponential Stability ◽  
Well Posed

In this paper, we consider a one-dimensional laminated beam with structural damping and an infinite memory acting on the effective rotation angle. Under appropriate assumptions imposed on the relaxation function, we show that the system is well-posed by using the Hille–Yosida theorem, and then we establish general decay results, from which exponential and polynomial decays are only special cases, in the case of equal speeds of wave propagation as well as that of nonequal speeds. In the particular case when the wave propagation speeds are different and the relaxation function decays exponentially, we show the lack of exponential stability.

Assessment on speed and amplitude of elastic wave propagation in square-packed circular honeycombs

2020 ◽  
Vol 56 (1) ◽  
pp. 18-28
Author(s):  
He-Xiang Wu ◽  
Xin-Chun Zhang ◽  
Ying Liu
Keyword(s):  
Wave Propagation ◽  
Elastic Wave ◽  
Structural Parameters ◽  
Propagation Speed ◽  
Development Trend ◽  
Elastic Wave Propagation ◽  
Theoretical Expression ◽  
Chain Model ◽  
Propagation Characteristics ◽  
Wave Propagation Speed

In contrast to the dynamic response characteristics, few propagation characteristics of elastic waves have been described on cellular materials, to date. In view of the development trend of emerging metamaterials on multi-functional, detailed characterization of elastic wave in honeycombs becomes an important task in order to assess their performances. This study investigates the propagation characteristics of elastic wave in square-packed circular honeycombs through combining theoretical analysis and numerical simulation. We also establish a one-dimensional circular chain model to discuss the influence mechanism of impact velocities, material parameters, and structural parameters on the elastic wave propagation characteristics in square-packed circular honeycombs. The influence relations are quantified and a semi-empirical theoretical expression for assessing characterization is presented, which extends theory of elastic wave propagation speed from solid materials to square-packed circular honeycombs. The assessment equation fully describes the elastic wave propagation speed and stress amplitude variation with location during propagation in square-packed circular honeycombs, and the results are consistent with the experimental data from the literature. The findings herein are aimed at providing an assessment equation with simple form for engineering applications easily and providing theoretical basis for elastic wave control and multi-functional combination design of metamaterials.

scholarly journals Elastic spheres can walk on water

2016 ◽  
Vol 7 (1) ◽  
Author(s):  
Jesse Belden ◽  
Randy C. Hurd ◽  
Michael A. Jandron ◽  
Allan F. Bower ◽  
Tadd T. Truscott
Keyword(s):  
Wave Propagation ◽  
Shear Modulus ◽  
Elastic Waves ◽  
Engineering Application ◽  
Hydrodynamic Pressure ◽  
Propagation Speed ◽  
Spherical Shape ◽  
Water Impact ◽  
Wave Propagation Speed ◽  
Large Material

Abstract Incited by public fascination and engineering application, water-skipping of rigid stones and spheres has received considerable study. While these objects can be coaxed to ricochet, elastic spheres demonstrate superior water-skipping ability, but little is known about the effect of large material compliance on water impact physics. Here we show that upon water impact, very compliant spheres naturally assume a disk-like geometry and dynamic orientation that are favourable for water-skipping. Experiments and numerical modelling reveal that the initial spherical shape evolves as elastic waves propagate through the material. We find that the skipping dynamics are governed by the wave propagation speed and by the ratio of material shear modulus to hydrodynamic pressure. With these insights, we explain why softer spheres skip more easily than stiffer ones. Our results advance understanding of fluid-elastic body interaction during water impact, which could benefit inflatable craft modelling and, more playfully, design of elastic aquatic toys.

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