Damping Characterization of Bulk Nanostructured Nickel Using an Innovative Circle-Fit Approach: Effect of Frequency

In the present study, elemental Ni powder was mechanically milled (MMed) for 10 hours to reduce the grain (crystalline) size in the nano-range (<100nm). The mechanically milled powder (10h-MMed) was consolidated by die-cold compaction and was further hot extruded at high temperatures to maintain a crystallite size within the nano range. Further, the specimen was tested by a novel free-free type suspended beam arrangement, coupled with circle-fit approach to determine damping characteristics. To vary the resonant frequency of the suspended beam, end masses with different weights were added. The characterization results revealed that the nano-size grains exhibit increased damping compared to a coarse-grained sample, under similar vibration frequency. Results also show that the damping capacity of both nano and coarse grained samples decreases with an increase in frequency of vibration. Particular emphasis was placed to correlate the damping capacity with the process induced residual stresses present in the samples.

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Simulation and Characterization of Particle Damping in Transient Vibrations

Journal of Vibration and Acoustics ◽

10.1115/1.1687401 ◽

2004 ◽

Vol 126 (2) ◽

pp. 202-211 ◽

Cited By ~ 61

Author(s):

Kuanmin Mao ◽

Michael Yu Wang ◽

Zhiwei Xu ◽

Tianning Chen

Keyword(s):

Damping Capacity ◽

Friction Damper ◽

Dense Particle ◽

Relative Significance ◽

Analysis And Design ◽

Damping Characteristics ◽

Highly Nonlinear ◽

Particle Damping ◽

The Impact

Particle damping is a technique of providing damping with granular particles embedded within small holes in a vibrating structure. The particles absorb kinetic energy through particle-to-wall and particle-to-particle frictional collisions. While the concept of particle damping seems to be simple and it has been used successfully in many fields for vibration reduction, it is difficult to predict the damping characteristics due to complex collisions in the dense particle flow. In this paper, we utilize the 3D discrete element method (DEM) for computer simulation and characterization of particle damping. With the DEM modeling tool validated with experimental results, it is shown that the particle damping can achieve a very high value of specific damping capacity. Furthermore, simulations provide information of particle motions within the container hole during three different regions and help explain their associated damping characteristics. The particle damping is a combination of the impact and the friction damping. The damping is found to be highly nonlinear as the rate of energy dissipation depends on amplitude. Particularly, the damping effect results in a linear decay in amplitude over a finite period of time. These characteristics are examined with respect to a simple single-mass impact damper and a dry-friction damper. It is concluded that the particle damping is a mix of these two damping mechanisms. It is further shown that the relative significance of these damping mechanisms depends on a particular arrangement of the damper. This study represents an effort towards a deeper understanding of particle damping to provide a comprehensive methodology for its analysis and design.

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A Comprehensive Study on the Optimal Design of Magnetorheological Dampers for Improved Damping Capacity and Dynamical Adjustability

Actuators ◽

10.3390/act10030064 ◽

2021 ◽

Vol 10 (3) ◽

pp. 64

Author(s):

Liankang Wei ◽

Hongzhan Lv ◽

Kehang Yang ◽

Weiguang Ma ◽

Junzheng Wang ◽

...

Keyword(s):

Optimal Design ◽

Optimization Methods ◽

Design Stage ◽

Damping Capacity ◽

Damping Force ◽

Simulation And Optimization ◽

Damping Characteristics ◽

Hysteretic Characteristics ◽

Gap Width ◽

Comprehensive Study

Purpose: We aim to provide a systematic methodology for the optimal design of MRD for improved damping capacity and dynamical adjustability in performing its damping function. Methods: A modified Bingham model is employed to model and simulate the MRD considering the MR fluid’s compressibility. The parameters that describe the structure of MRD and the property of the fluid are systematically examined for their contributions to the damping capacity and dynamically adjustability. A response surface method is employed to optimize the damping force and dynamically adjustable coefficient for a more practical setting related to the parameters. Results: The simulation system effectively shows the hysteretic characteristics of MRDs and shows our common sense understanding that the damping gap width and yoke diameter have significant effects on the damping characteristics of MRD. By taking a typical MRD device setup, optimal design shows an increase of the damping force by 33% and an increase of the dynamically adjustable coefficient by 17%. It is also shown that the methodology is applicable to other types of MDR devices. Conclusion: The compressibility of MR fluid is one of the main reasons for the hysteretic characteristics of MRD. The proposed simulation and optimization methods can effectively improve the MRD’s damping performance in the design stage.

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Complex Permittivity Characterization of Liquid Samples Based on a Split Ring Resonator (SRR)

Sensors ◽

10.3390/s21103385 ◽

2021 ◽

Vol 21 (10) ◽

pp. 3385

Author(s):

Jialu Ma ◽

Jingchao Tang ◽

Kaicheng Wang ◽

Lianghao Guo ◽

Yubin Gong ◽

...

Keyword(s):

Resonant Frequency ◽

Complex Permittivity ◽

Ring Resonator ◽

High Sensitivity ◽

Split Ring Resonator ◽

Debye Model ◽

Split Ring ◽

Liquid Samples ◽

Microwave Sensor

A complex permittivity characterization method for liquid samples has been proposed. The measurement is carried out based on a self-designed microwave sensor with a split ring resonator (SRR), the unload resonant frequency of which is 5.05 GHz. The liquid samples in capillary are placed in the resonant zone of the fabricated senor for high sensitivity measurement. The frequency shift of 58.7 MHz is achieved when the capillary is filled with ethanol, corresponding a sensitivity of 97.46 MHz/μL. The complex permittivity of methanol, ethanol, isopropanol (IPA) and deionized water at the resonant frequency are measured and calibrated by the first order Debye model. Then, the complex permittivity of different concentrations of aqueous solutions of these materials are measured by using the calibrated sensor system. The results show that the proposed sensor has high sensitivity and accuracy in measuring the complex permittivity of liquid samples with volumes as small as 0.13 μL. It provides a useful reference for the complex permittivity characterization of small amount of liquid chemical samples. In addition, the characterization of an important biological sample (inositol) is carried out by using the proposed sensor.

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Characterization of Residual Stresses in Composites

Fundamentals of Metal-Matrix Composites ◽

10.1016/b978-0-08-052371-2.50008-0 ◽

1993 ◽

pp. 61-80 ◽

Cited By ~ 4

Author(s):

MARK A.M. BOURKE ◽

JOYCE A. GOLDSTONE ◽

MICHAEL G. STOUT ◽

ALAN NEEDLEMAN

Keyword(s):

Residual Stresses

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MECHANICAL CHARACTERIZATION OF MATERIALS AND DIAGNOSIS OF STRUCTURES BY INVERSE ANALYSES: SOME INNOVATIVE PROCEDURES AND APPLICATIONS

International Journal of Computational Methods ◽

10.1142/s0219876213430020 ◽

2014 ◽

Vol 11 (03) ◽

pp. 1343002 ◽

Cited By ~ 11

Author(s):

GIULIO MAIER ◽

VLADIMIR BULJAK ◽

TOMASZ GARBOWSKI ◽

GIUSEPPE COCCHETTI ◽

GIORGIO NOVATI

Keyword(s):

Structural Analysis ◽

Digital Image Correlation ◽

Residual Stresses ◽

Mechanical Characterization ◽

Image Correlation ◽

Alkali Silica Reaction ◽

Compression Tests ◽

Material Models ◽

Characterization Of Materials

A survey is presented herein of some recent research contributions to the methodology of inverse structural analysis based on statical tests for diagnosis of possibly damaged structures and for mechanical characterization of materials in diverse industrial environments. The following issues are briefly considered: identifications of parameters in material models and of residual stresses on the basis of indentation experiments; mechanical characterization of free-foils and laminates by cruciform and compression tests and digital image correlation measurements; diagnosis, both superficially and in depth, of concrete dams, possibly affected by alkali-silica-reaction or otherwise damaged.

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Detonation Synthesis of Nano-Size Materials

MRS Proceedings ◽

10.1557/proc-418-439 ◽

1995 ◽

Vol 418 ◽

Cited By ~ 1

Author(s):

J. Forbes ◽

J. Davis ◽

C. Wong

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Nucleation And Growth ◽

Detonation Synthesis ◽

X Ray Diffraction ◽

Crystalline Materials ◽

X Ray ◽

Transmission Electron ◽

Nano Size

AbstractThe detonation of explosives typically creates 100's of kbar pressures and 1000's K temperatures. These pressures and temperatures last for only a fraction of a microsecond as the products expand. Nucleation and growth of crystalline materials can occur under these conditions. Recovery of these materials is difficult but can occur in some circumstances. This paper describes the detonation synthesis facility, recovery of nano-size diamond, and plans to synthesize other nano-size materials by modifying the chemical composition of explosive compounds. The characterization of nano-size diamonds by transmission electron microscopy and electron diffraction, X-ray diffraction and Raman spectroscopy will also be reported.

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