scholarly journals INVESTIGASI KARAKTERISTIK GETARAN KOMPOSIT SANDWICH BERBAHAN SERAT KARBON UNI-DIRECTIONAL BERPENGUAT CRESTAPOL

Technologic ◽  
2021 ◽  
Vol 12 (2) ◽  
Author(s):  
Nur Mufidatul Ula ◽  
Yusuf Giri Wijaya ◽  
Mikhael Gilang Pribadi Putra Pratama ◽  
Nurul Lailatul Muzayadah
Keyword(s):  
Damping Ratio ◽  
Damping Factor ◽  
Damping Properties ◽  
Resin Infusion

Material Komposit Sandwich adalah jenis komposit yang terdiri dari susunan komposit laminate dengan core didalamnya. Pemanfaatan komposit sandwich saat ini sangat luas termasuk salah satunya sebagai struktur sekunder dalam pesawat mengingat masa komposit jenis ini lebih ringan dibandingkan komposit dengan full laminate. Salah satu pemanfaatanya adalah dalam pembuatan kompartemen float. Penggunaan komposit sebagai bahan kompartemen float perlu diketahui karakteristik dinamisnya. Dalam penelitian ini sampel yang digunakan dibuat dengan metode Vacuum Assisted Resin Infusion (VARI). Variasi sampel komposit akan diambil data karakteristik dinamik nya berupa damping factor dan natural frekuensinya sebagai acuan awal pemilihan komposisi material. Sampel uji yang digunakan berukuran 50x230mm dengan metode pengujian menggunakan metode Oberst. Profil getaran yang digunakan untuk pengujian adalah jenis sapuan sinus dari 10Hz sampai 2000Hz. Hasil pengujian menunjukkan bahwa sampel 3C3 memiliki Frekuensi natural yang lebih tinggi dibandingkan dengan sampel 2C2 namun memiliki nilai Damping properties yang lebih rendah. Hasil ini menunjukkan bahwa sampel 3C3 memiliki nilai kekakuan yang lebih tinggi dibandingkan 2C2. Dari hasil juga memperlihatkan bahwa sampel 2C2 memiliki kemampuan redaman yang lebih baik dibanding sampel 3C3. Pemilihan material berdasarkan hasil pengujian menunjukkan bahwa 2C2 memiliki keunggulan damping ratio dibandingkan 3C3 namun masih diperlukan lebih banyak variasi lagi untuk mendapatkan komposisi material terbaiknya.

scholarly journals Optimal design of controllers for power network connected SOFC using of multi-objective PSO

2018 ◽  
Vol 15 (2) ◽  
pp. 145-163 ◽  
Author(s):  
Amin Safari ◽  
Hossein Shahsavari ◽  
Farshad Babaei
Keyword(s):  
Damping Ratio ◽  
Damping Factor ◽  
Small Signal ◽  
Small Signal Stability ◽  
Machine System ◽  
Multi Objective ◽  
Signal Stability ◽  
Power Oscillations ◽  
System Stabilizer ◽  
Small Signal Modeling

In this paper, we study the concept and forming manner of Solid Oxide Fuel Cell (SOFC) into the electrical system and then, its effect on small signal stability is investigated. The paper illustrates the essential module, mathematical analysis and small signal modeling of the SOFC joined to single machine system. The aim of this study is to reduce power oscillations in the presence of the SOFC with optimal stabilizer. The multi-objective Particle Swarm Optimization (MOPSO) technique has been used for designing a Power System Stabilizer (PSS) in order to improve the performance of the system. Two objective functions are regarded for the design of PSS parameters in order to maximize the damping factor and the damping ratio of the system. To evaluate the efficiency of the proposed optimal stabilizers, four scenarios are considered and then, its results have been analyzed. The proposed PSS tuning technique can be applied to a multi-machine system connected to the SOFC. The efficiency of MOPSO based proposed PSS on the oscillations the system related to SOFC is illustrated by time-domain simulation and also, the comparison of the MOPSO based proposed PSS with the PSS based-single objective method has been prepared.

scholarly journals Improving the Damping Properties of Nanocomposites by Monodispersed Hybrid POSS Nanoparticles: Preparation and Mechanisms

Polymers ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 647 ◽  
Author(s):  
Wei Wei ◽  
Yingjun Zhang ◽  
Meihua Liu ◽  
Yifan Zhang ◽  
Yuan Yin ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Damping Factor ◽  
Damping Properties ◽  
Molecular Weights ◽  
Organic Hybrid ◽  
Transmission Electron ◽  
The Matrix ◽  
Movement Ability ◽  
Tan Δ ◽  
Oligomeric Silsesquioxane

In this work, a series of heptaphenyl siloxane trisilanol/polyhedral oligomeric silsesquioxane (T7-POSS) modified by polyols with different molecular weights were synthesized into liquid-like nanoparticle–organic hybrid materials using the grafted-from method. All grafted POSS nanoparticles changed from solid powders to liquid at room temperature. Polyurethane (PU) nanocomposites with POSS contents ranging from 1.75 to 9.72 wt % were prepared from these liquefied polyols-terminated POSS with polyepichlorohydrin (POSS–PECH). Transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to characterize the morphology of the POSS–PECH/PU nanocomposites. The results showed that the polyol-terminated POSS particles overcame the nanoagglomeration effect and evenly disperse in the polymeric matrix. The damping factor (tan δ) of resultant nanocomposites increased from 0.90 to 1.16, while the glass transition temperature decreased from 15.8 to 9.4 °C when POSS contents increased from 0 to 9.75 wt %. The gel content, tensile strength and Fourier transform infrared (FTIR) analyses demonstrated that the molecular thermal movement ability of the polyurethane (PU) matrix increased with increasing POSS hybrid content. Therefore, the improvement of the damping properties of the composites was mainly due to the friction-related losses occurring in the interface region between the nanoparticles and the matrix.

Improving Damping Properties of Railway Ballast by Addition of Tire-Derived Aggregate

2019 ◽  
Vol 2673 (5) ◽  
pp. 299-307 ◽  
Author(s):  
Weimin Song ◽  
Baoshan Huang ◽  
Xiang Shu ◽  
Hao Wu ◽  
Hongren Gong ◽  
...  
Keyword(s):  
Cyclic Loading ◽  
Damping Ratio ◽  
Shear Stiffness ◽  
Damping Properties ◽  
Railway Ballast ◽  
Loading Test ◽  
Interface Shear ◽  
Peak Shear Stress ◽  
Dilation Effect ◽  
Tire Derived Aggregate

The damping properties of railway ballast are critical to the safe operation of trains. This study aimed to improve the damping properties of railway ballast through the addition of tire-derived aggregate (TDA) and to evaluate the effect of TDA on other properties of ballast. The damping property and other mechanical properties of ballast mixed with different contents of TDA were tested utilizing a large direct shear test (DST) under static and cyclic loading conditions. The cyclic loading test was performed in accordance with ASTM D 7499, from which the resilient interface shear stiffness and damping ratio were obtained. The results showed that TDA significantly increased the damping ratio of railway ballast, but decreased the resilient interface shear stiffness. The stress-strain behavior of the ballast-TDA mixes was obtained from the static loading test, showing that TDA significantly decreased the peak shear stress and the dilation effect. According to the Mohr-Coulomb failure criterion, TDA also decreased the cohesion strength and the internal friction angle of the ballast. Based on the test results from this study, 5% rubber is recommended for use in railway ballast.

The Performance Study of Waterborne Damping Coating

2015 ◽  
Vol 1088 ◽  
pp. 444-448
Author(s):  
Xiao Wang ◽  
Pei Min Hou ◽  
Yuan Hao Xu ◽  
Jian Lei
Keyword(s):  
Mechanical Properties ◽  
Chemical Resistance ◽  
Physical And Mechanical Properties ◽  
Acrylic Resin ◽  
Damping Factor ◽  
Damping Properties ◽  
Performance Study ◽  
Excellent Performance

In this paper, waterborne damping coating with excellent performance was prepared by self-made acrylic resin, and its physical and mechanical properties, chemical resistance, and damping properties (damping factor) were studied.

Determination of Strength and Damping Characteristics of Carbon Nanotube-Epoxy Composites

2004 ◽  
Author(s):  
Himanshu Rajoria ◽  
Nader Jalili
Keyword(s):  
Carbon Nanotube ◽  
Impulse Response ◽  
Composite Beam ◽  
Damping Ratio ◽  
Chemical Vapor ◽  
Deposition Process ◽  
Epoxy Composites ◽  
Damping Properties ◽  
Stick Slip ◽  
Pzt Actuator

In this paper, the strength and damping properties of carbon nanotube-epoxy composites are examined. Carbon nanotubes (Single-walled and Multi-walled) were grown on stainless steel substrates using thermal chemical vapor deposition process. The nanotube-epoxy composites were then prepared by applying a layer of epoxy on the grown nanotubes and a PZT actuator was attached on this layer. The composite beam consisting of steel, nanotube-epoxy layer and PZT actuator was used as a cantilever beam for vibration experiments in order to determine the enhancement in strength and damping properties of the nanotube-epoxy layer. Several different samples were prepared for this purpose. Impulse and frequency sweep tests were conducted on these beams to obtain the impulse response and frequency response functions. Fast Fourier Transform of the impulse response was used to find the natural frequency of the composite beam. It was observed that there was an increase in the stiffness by using multi-walled nanotubes in the epoxy, while the damping ratio increased by using single-walled nanotubes. The stick-slip mechanism is discussed in order to explain the results obtained.

scholarly journals The Role of Damping and Definition of the Robust Damping Factor for a Self-Exciting Mechanism With Constant Friction

2006 ◽  
Vol 129 (3) ◽  
pp. 297-306 ◽  
Author(s):  
J-J. Sinou ◽  
G. Fritz ◽  
L. Jézéquel
Keyword(s):  
Damping Ratio ◽  
Damping Factor ◽  
Structural Damping ◽  
Modal Interaction ◽  
Mechanical Process ◽  
Flutter Instability ◽  
Constant Friction ◽  
Definition Of ◽  
Two Degree Of Freedom

This paper presents a linear two-degree-of-freedom model in order to analyze friction-induced instabilities that are governed by modal interaction. The role of structural damping on flutter instability is undertaken, and the effects of the structural damping ratio between the stable and unstable modes are investigated in order to clarify and to explain the mechanical process of flutter instability. In certain conditions, it is demonstrated that the merging scenario and the unstable mode may change due to this structural damping ratio. Discussions not only demontrate the role of strutural damping and the associated mechanical process but also define the robust damping factor in order to avoid design errors and to reduce flutter instability.

Kick Detection Using Downhole Accelerometer Data

2020 ◽  
Vol 142 (8) ◽  
Author(s):  
Robello Samuel
Keyword(s):  
High Frequency ◽  
Damping Ratio ◽  
Energy Operator ◽  
Damping Factor ◽  
Accelerometer Data ◽  
Intrinsic Mode Functions ◽  
Minimum Entropy ◽  
Time Data ◽  
Essential Information ◽  
Vibration Data

Abstract The high-frequency downhole vibration data include a greater amount of hidden information than the low-frequency surface data. This paper proposes the monitoring of high-frequency acceleration data for early kick detection. The trend of accelerator sensor values is monitored, rather than processed. When the gas, fluid, or oil kick occurs, the fluid influx reduces the viscosity of the fluid in annulus, which causes the degradation of the damping factor. The sensor installed on the drillpipe detects the velocity/acceleration change that results in the damping factor change. This approach includes an analytical model to calculate the effect of the damping ratio on the acceleration calculations. The fluid influx and migration in the wellbore strongly affect the damping factor. The paper presents a method of deconvoluting the sensor values that uses a combination of minimum entropy deconvolution and Teager-Kaiser energy operator to remove the noise, unwanted sensor values, and likelihood of false prediction. It is then proposed to calculate instantaneous jerk and jerk intensity at each depth. The trend of the final intrinsic mode functions (IMF) at each depth is continuously monitored to predict the formation influx, if any. A novel concept of monitoring the incremental IMF and IMF energy at each depth is introduced. This technique is shown to reveal a wealth of information and simplifies the process of monitoring and analyzing the vast amount of available data. The methodology developed is applied to extract the essential information from high-frequency vibration data to make real-time data monitoring straightforward, reliable, and fast.

scholarly journals Mechanical and Damping Properties of Recycled Aggregate Concrete Modified with Air-Entraining Agent and Polypropylene Fiber

Materials ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 2004 ◽  
Author(s):  
Chonggang Zhou ◽  
Xingwang Pei ◽  
Wenlong Li ◽  
Yijun Liu
Keyword(s):  
Mechanical Performance ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Polypropylene Fiber ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Favorable Effect ◽  
Damping Properties ◽  
Aggregate Concrete ◽  
Negative Effect

In this study, recycled aggregate concrete (RAC) modified with polypropylene fiber (PP) and air-entraining agent (AGA) was prepared, and the effects of PP and AGA on the static (compressive strength, Young’s modulus, and splitting tensile strength) and dynamic properties (dynamic modulus of elasticity and damping ratio) of RAC were investigated. The experimental results showed that the addition of an AGA and PP had a favorable effect on the damping ratio of the concrete, however, the addition of the AGA had a slightly negative effect on the mechanical performance of the concrete. The AGA and PP contents required to achieve the optimum damping ratio of the concrete with the least reduction in the mechanical performance were 0.02% and 0.10%, respectively. Furthermore, the addition of AGA was more effective than that of PP in improving the damping property of the concrete.

Damping of Resonant Oscillations of a Jacket Structure Based on Full-Scale Measurements

1995 ◽  
Vol 117 (2) ◽  
pp. 71-77
Author(s):  
T. C. Thuestad ◽  
F. G. Nielsen
Keyword(s):  
Damping Ratio ◽  
Full Scale ◽  
Type Model ◽  
Damping Properties ◽  
Dynamic Motion ◽  
Highly Nonlinear ◽  
Jacket Structures ◽  
Coulomb Type ◽  
The Impact ◽  
Motion Amplitude

Damping of jacket structures are discussed on the basis of full-scale measurements. During a submarine impact with a jacket structure, unique transient response time series, damping properties are evaluated in terms of the nature and magnitude of the total damping. It is shown that the damping is highly nonlinear and fits a Coulomb-type model reasonably well. The damping magnitude expressed as the relative damping ratio is estimated to be in the range from 0.5 to 3.0 percent, dependent on the motion amplitude. Within the range of motion amplitudes experienced during the impact, the damping decreases with increasing motion amplitudes. The resonant motion amplitudes recorded during the impact are shown to be far greater than the expected dynamic motion amplitudes during a storm period.

scholarly journals The damping and structural properties of dragonfly and damselfly wings during dynamic movement

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Carina Lietz ◽  
Clemens F. Schaber ◽  
Stanislav N. Gorb ◽  
Hamed Rajabi
Keyword(s):  
Insect Flight ◽  
Damping Ratio ◽  
Damping Properties ◽  
Oscillatory Behaviour ◽  
Environmental Disturbances ◽  
Insect Wing ◽  
Dynamic Movement ◽  
Flying Insects ◽  
Flight Muscles ◽  
The Mean

AbstractFor flying insects, stability is essential to maintain the orientation and direction of motion in flight. Flight instability is caused by a variety of factors, such as intended abrupt flight manoeuvres and unwanted environmental disturbances. Although wings play a key role in insect flight stability, little is known about their oscillatory behaviour. Here we present the first systematic study of insect wing damping. We show that different wing regions have almost identical damping properties. The mean damping ratio of fresh wings is noticeably higher than that previously thought. Flight muscles and hemolymph have almost no ‘direct’ influence on the wing damping. In contrast, the involvement of the wing hinge can significantly increase damping. We also show that although desiccation reduces the wing damping ratio, rehydration leads to full recovery of damping properties after desiccation. Hence, we expect hemolymph to influence the wing damping indirectly, by continuously hydrating the wing system.

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