Attenuation of High Amplitude Vibrations With Particle Dampers

2002 ◽  
Author(s):  
Michael Y. Yang ◽  
Gary H. Koopmann ◽  
George A. Lesieutre ◽  
Stephen A. Hambric
Keyword(s):  
Fluid Transport ◽  
Extreme Temperature ◽  
Excitation Amplitude ◽  
High Amplitude ◽  
Transport Systems ◽  
Design Parameters ◽  
Gap Size ◽  
Physical Damage ◽  
Transient Phenomena ◽  
Particle Dampers

Fluid transport systems are rarely at steady state. Transient phenomena, such as water hammer, can inflict severe physical damage. Repair costs can soar into the millions of dollars (Myers, 1997), and can reduce or even halt operation. Such high amplitude vibrations may be attenuated with particle dampers, which are beds of small particles placed in an attached enclosure or contained void. Vibration of the enclosure causes the particles to collide with each other and with the enclosure walls, resulting in energy dissipation through inelastic impacts and friction. Particle dampers have many advantages over conventional viscoelastic treatments including lower cost, increased robustness, greater effectiveness at high amplitudes and the ability to operate in extreme-temperature environments. Previous papers focus on exploration of sensitivity to design parameters, modeling techniques, and effective applications. However, there still remains much that is unknown about the phenomena and design of particle dampers. In this paper, experiments were performed to explore the effects of friction, excitation amplitude, and particle gap size. The formation of an oily residue on the colliding surfaces when certain materials were used increased friction and reduced damper effectiveness. This agrees with the theoretical prediction made by Mansour and Filho (1974). Damping was found to peak at an optimum gap size. Increasing the excitation amplitude resulted in higher damping and reduced sensitivity to the optimum gap size. Overall, the particle damper was deemed to be successful, increasing the loss factor of a clamped beam by over 10 times with a damper/structure mass ratio of only 0.016.

Reversible Passive Bandgap Reconfiguration Using an Excitation Dependent On-Site Restoring Force

2015 ◽  
Author(s):  
Brian P. Bernard ◽  
Kim Arvidsson
Keyword(s):  
Nearest Neighbor ◽  
Energy Levels ◽  
Excitation Amplitude ◽  
High Amplitude ◽  
High Energy ◽  
Design Parameters ◽  
Energy Curve ◽  
Initial State ◽  
Restoring Force ◽  
Stable Curve

By applying an excitation dependent, on-site restoring force to oscillators in a uniform one-dimensional chain with nearest neighbor coupling, this paper demonstrates the feasibility of reversible passive bandgap reconfiguration. Waveguide devices are most commonly tuned using active controls, component replacement, or by manually varying design parameters. Recent studies on wave propagation have pursued passive controls, where high amplitude environmental excitation triggers a potential well escape in an asymmetric, bi-stable system, automatically changing its linear spectra without user interaction. Current designs, however, do not return to their initial state upon later excitation amplitude reduction, instead requiring manual reset for continued operation. In order to allow fully autonomous function, a passively reconfigurable system must also be designed to return to its low amplitude state after environmental excitation amplitude decreases. This paper proposes a system in which reversible bifurcations are observed by introducing an excitation dependent on-site stiffness. Instead of a fixed, bi-stable potential energy curve, the oscillators have a single mono-stable curve at low energy levels and a different mono-stable curve with its own distinct linear spectrum at high energy levels. Numerical simulations are provided to demonstrate system transitions from propagation zone to attenuation zone behavior, and back, when subjected to increasing and decreasing excitation amplitudes.

Coupling Simulation Algorithm of Dynamic Feature of a Plate With Particle Dampers Under Centrifugal Loads

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Zhaowang Xia ◽  
Xiandong Liu ◽  
Yingchun Shan
Keyword(s):  
Vibration Suppression ◽  
Extreme Temperature ◽  
Extreme Environment ◽  
Dynamic Feature ◽  
Simulation Algorithm ◽  
Centrifugal Forces ◽  
Granular Particle ◽  
Particle Damping ◽  
Particle Dampers ◽  
Element Method

Particle damper comprises granular particle enclosed in a container within a vibrating structure. The performance of particle damper is strongly nonlinear whose energy dissipation is derived from a combination of mechanisms including plastic collisions and friction between particles or particles and cavity walls. Particle damper containing suitable materials may be effective in a wider temperature range than most other types of passive damping devices. Therefore, it may be applied in extreme temperature environments where most conventional dampers would fail. It may also attenuate vibrations over a broad range of frequencies and cost less. Researches have indicated that particle damper could be a viable option for extreme environment applications. However, to date, no effort has come forward the can prove analytically or numerically that the particle damping is a viable solution for vibration suppression under centrifugal forces. In this paper, a coupling simulation algorithm based on the discrete element method and finite element method and the results of simulative studies aimed at understanding the effects of parameters of particle damper under centrifugal forces are presented. And the results show that the presented coupling simulation algorithm is effective and the analyses of dynamic feature of a plate with particle dampers under centrifugal loads are reasonable.

Particle Dampers for Workpiece Chatter Mitigation

2005 ◽  
Author(s):  
Neil D. Sims ◽  
Ashan Amarasinghe ◽  
Keith Ridgway
Keyword(s):  
Wide Frequency Range ◽  
Machining Process ◽  
Design Parameters ◽  
Depth Of Cut ◽  
Vibration Absorbers ◽  
Tuned Vibration Absorbers ◽  
Highly Nonlinear ◽  
Machining System ◽  
Order Of Magnitude ◽  
Particle Dampers

It is well known that the chatter stability of a machining process can be improved by increasing the structural damping of the system. To date this approach has been effectively used on various components of the machining system, for example boring bars, milling tools, and the machine structure itself. Various damping treatments have been proposed, including tuned vibration absorbers, active methods, and impact dampers. However, to date there has been little or no work to investigate the issue of particle dampers for this application. This special class of damper comprises a container of thousands of small granular particles which dissipate energy by friction and impact when the container vibrates. The resulting behaviour is highly nonlinear but can provide very high levels of damping across a wide frequency range. In the present study, particle dampers were applied to a workpiece to mitigate chatter during milling, and the limiting critical depth of cut was increased by an order of magnitude. This article gives an overview of the particle damper’s behaviour and key design parameters. Cutting trials employing the device are then described.

One-Dimensional Unsteady Periodic Flow Model with Boundary Conditions Constrained by Differential Equations

2009 ◽  
Vol 131 (6) ◽  
Author(s):  
Nhan T. Nguyen
Keyword(s):  
Differential Equations ◽  
Boundary Conditions ◽  
Euler Equations ◽  
Periodic Boundary ◽  
Closed Loop ◽  
Fluid Transport ◽  
Periodic Boundary Conditions ◽  
Transport Systems ◽  
Variable Approach ◽  
Upwind Method

This paper describes a modeling method for closed-loop unsteady fluid transport systems based on 1D unsteady Euler equations with nonlinear forced periodic boundary conditions. A significant feature of this model is the incorporation of dynamic constraints on the variables that control the transport process at the system boundaries as they often exist in many transport systems. These constraints result in a coupling of the Euler equations with a system of ordinary differential equations that model the dynamics of auxiliary processes connected to the transport system. Another important feature of the transport model is the use of a quasilinear form instead of the flux-conserved form. This form lends itself to modeling with measurable conserved fluid transport variables and represents an intermediate model between the primitive variable approach and the conserved variable approach. A wave-splitting finite-difference upwind method is presented as a numerical solution of the model. An iterative procedure is implemented to solve the nonlinear forced periodic boundary conditions prior to the time-marching procedure for the upwind method. A shock fitting method to handle transonic flow for the quasilinear form of the Euler equations is presented. A closed-loop wind tunnel is used for demonstration of the accuracy of this modeling method.

scholarly journals Optimization of SAW Devices with LGS/Pt Structure for Sensing Temperature

Sensors ◽  
2020 ◽  
Vol 20 (9) ◽  
pp. 2441
Author(s):  
Xueling Li ◽  
Wen Wang ◽  
Shuyao Fan ◽  
Yining Yin ◽  
Yana Jia ◽  
...  
Keyword(s):  
High Temperature ◽  
Quality Factor ◽  
Short Pulse ◽  
Extreme Temperature ◽  
Parameters Optimization ◽  
Design Parameters ◽  
Q Value ◽  
Element Analysis ◽  
Saw Devices ◽  
Extreme High Temperature

Research has shown that SAW (surface acoustic wave) devices with an LGS/Pt (langasite La3Ga5SiO14/platinum) structure are useful in high-temperature sensor applications. Extreme high temperature brings great acoustic attenuation because of the thermal radiation loss, which requires that the sensing device offer a sufficiently high quality factor (Q) and a low loss. Therefore, it is necessary to improve the performance of the quality factor as much as possible so as to better meet the application of high-temperature sensors. Based on these reasons, the main work of this paper was to extract accurate simulation parameters to optimize the Pt/LGS device and obtain Q-value device parameters. Optimization of SAW devices with LGS/Pt structure for sensing extreme high temperature was addressed by employing a typical coupling of modes (COM) model in this work. Using the short pulse method, the reflection coefficient of Pt electrodes on LGS substrate was extracted accurately by characterizing the prepared SAW device with strategic design. Other relevant parameters for COM simulation were determined by finite element analysis. To determine the optimal design parameters, the COM simulation was conducted on the SAW sensing device with a one-port resonator pattern for sensing extreme temperature, which allows for a larger Q-value and low insertion loss. Experimental results validate the theoretical simulation. In addition, the corresponding high-temperature characteristics of the prepared sensing device were investigated.

scholarly journals Influence of Material Selection on the Marginal Accuracy of CAD/CAM-Fabricated Metal- and All-Ceramic Single Crown Copings

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Matthias Rödiger ◽  
Lea Schneider ◽  
Sven Rinke
Keyword(s):  
Material Selection ◽  
Design Parameters ◽  
Processing Route ◽  
Chromium Alloy ◽  
Gap Size ◽  
Marginal Gap ◽  
Average Maximum ◽  
Single Crown ◽  
Cad Cam ◽  
Group 2

This study evaluated the marginal accuracy of CAD/CAM-fabricated crown copings from four different materials within the same processing route. Twenty stone replicas of a metallic master die (prepared upper premolar) were scanned and divided into two groups. Group 1 (n=10) was used for a pilot test to determine the design parameters for best marginal accuracy. Group 2 (n=10) was used to fabricate 10 specimens from the following materials with one identical CAD/CAM system (GAMMA 202, Wissner GmbH, Goettingen, Germany): A = commercially pure (cp) titanium, B = cobalt-chromium alloy, C = yttria-stabilized zirconia (YSZ), and D = leucite-reinforced glass-ceramics. Copings from group 2 were evaluated for the mean marginal gap size (MeanMG) and average maximum marginal gap size (AMaxMG) with a light microscope in the “as-machined” state. The effect of the material on the marginal accuracy was analyzed by multiple pairwise comparisons (Mann–Whitney, U-test, α=0.05, adjusted by Bonferroni-Holmes method). MeanMG values were as follows: A: 46.92 ± 23.12 μm, B: 48.37 ± 29.72 μm, C: 68.25 ± 28.54 μm, and D: 58.73 ± 21.15 μm. The differences in the MeanMG values proved to be significant for groups A/C (p=0.0024), A/D (p=0.008), and B/C (p=0.0332). AMaxMG values (A: 91.54 ± 23.39 μm, B: 96.86 ± 24.19 μm, C: 120.66 ± 32.75 μm, and D: 100.22 ± 10.83 μm) revealed no significant differences. The material had a significant impact on the marginal accuracy of CAD/CAM-fabricated copings.

scholarly journals Forecasting rational working modes of long-operated gas-transport systems under conditions of their incomplete loading

2021 ◽  
Vol 4 (8(112)) ◽  
pp. 6-15
Author(s):  
Volodymyr Grudz ◽  
Yaroslav Grudz ◽  
Myroslav Iakymiv ◽  
Mykola Iakymiv ◽  
Pavlo Iagoda
Keyword(s):  
Mathematical Modeling ◽  
Energy Consumption ◽  
Transport System ◽  
Gas Transport ◽  
Pressure Fluctuations ◽  
Initial Pressure ◽  
High Amplitude ◽  
Nonstationary Process ◽  
Optimality Criteria ◽  
Transport Systems

Prolonged operation of the gas-transport system in conditions of partial loading involves frequent changes in the volume of gas transportation, which necessitates prompt forecasting of system operation. When forecasting the modes of operation of the gas transport system, the main criterion of optimality implies the maximum volume of gas pumping. After all, in this case, the largest profit of the gas-transport company is achieved under the condition of full provision of consumers with energy. In conditions of incomplete loading of the gas-transport system caused by a shortage of gas supply, optimality criteria change significantly. First, the equipment is operated in ranges far from nominal ones which leads to growth of energy consumption. Secondly, changes in performance cause high-amplitude pressure fluctuations at the outlet of compressor stations. Based on mathematical modeling of nonstationary processes, amplitude and frequency of pressure fluctuations at the outlet of compressor stations which can cause the pipeline overload have been established. To prevent this, it was proposed to reduce initial pressure relative to the maximum one. Calculated dependence was obtained which connects the amplitude of pressure fluctuations with the characteristics of the gas pipeline and the nonstationary process. Reduction in energy consumption for transportation is due to the shutdown of individual compressor stations (CS). Mathematical modeling has made it possible to establish regularities of reduction of productivity of the gas-transport system and duration of the nonstationary process depending on the location of the compressor station on the route. With an increase in the number of shutdown compression stations, the degree of productivity decrease and duration of nonstationarity reduces The established patterns and proposed solutions will improve the reliability of a gas-transport system by preventing pipeline overload and reduce the cost of gas transportation by selecting running numbers of shutdown stations with a known decrease in productivity.

Bifurcation Patterns and Branching Exponents in Branchial Vessels in Tadpoles of Xenopus laevis Daudin during Metamorphosis-3D-Measurements from Microvascular Corrosion Casts

2001 ◽  
Vol 7 (S2) ◽  
pp. 1188-1189
Author(s):  
B. Minnich ◽  
H. Bartel ◽  
R. Karch ◽  
W. Schreiner ◽  
A. Lametschwandtner
Keyword(s):  
Fluid Transport ◽  
Vascular System ◽  
Three Dimensional ◽  
Circulatory System ◽  
Transport Systems ◽  
Corrosion Casts ◽  
Parent Vessel ◽  
Tubular System ◽  
Anuran Tadpole ◽  
Existing Data

IntroductionFluid transport systems of organisms [1] in general and the blood vascular system in particular are considered to be optimally designed. From Murray's laws [2] it is concluded that an arterial bifurcation where the diameter of the parent vessel (d0) relates to the larger (d1) and the smaller daughter vessel (d2) according to d03 = d13 + d23 is optimal. Interestingly, existing data predominantly refer to arterial branchings of the fully developed circulatory system of mammals. to the best of our knowledge there are no data available on arterial bifurcations and venous mergings in an initially growing but then regressing tubular system of blood vessels as it is found in the gill filter apparatus of the anuran tadpole where the highly complex three-dimensional vascular network totally disappears at the end of metamorphosis.

scholarly journals A design principle of root length distribution of plants

2019 ◽  
Vol 16 (161) ◽  
pp. 20190556
Author(s):  
Yeonsu Jung ◽  
Keunhwan Park ◽  
Kaare H. Jensen ◽  
Wonjung Kim ◽  
Ho-Young Kim
Keyword(s):  
Water Uptake ◽  
Root Length ◽  
Fluid Transport ◽  
Root Length Density ◽  
Global Climate ◽  
Plant Root ◽  
Length Distribution ◽  
Biological Data ◽  
Transport Systems ◽  
Network Systems

Shaping a plant root into an ideal structure for water capture is increasingly important for sustainable agriculture in the era of global climate change. Although the current genetic engineering of crops favours deep-reaching roots, here we show that nature has apparently adopted a different strategy of shaping roots. We construct a mathematical model for optimal root length distribution by considering that plants seek maximal water uptake at the metabolic expenses of root growth. Our theory finds a logarithmic decrease of root length density with depth to be most beneficial for efficient water uptake, which is supported by biological data as well as our experiments using root-mimicking network systems. Our study provides a tool to gauge the relative performance of root networks in transgenic plants engineered to endure a water deficit. Moreover, we lay a fundamental framework for mechanical understanding and design of water-absorptive growing networks, such as medical and industrial fluid transport systems and soft robots, which grow in porous media including soils and biotissues.

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