scholarly journals Performance of a New Fine Particle Impact Damper

2008 ◽  
Vol 2008 ◽  
pp. 1-6 ◽  
Author(s):  
Yanchen Du ◽  
Shulin Wang ◽  
Yan Zhu ◽  
Laiqiang Li ◽  
Guangqiang Han
Keyword(s):  
Fine Particle ◽  
Mechanical Vibration ◽  
Low Frequency ◽  
Particle Impact ◽  
Momentum Exchange ◽  
Impact Damper ◽  
Low Frequency Vibration ◽  
Cantilevered Beam ◽  
The Impact ◽  
First Time

The energy dissipation mechanisms of conventional impact damper (CID) are mainly momentum exchange and friction. During the impact process, a lot of vibration energy cannot be exhausted but reverberated among the vibration partners. Besides, the CID may produce the additional vibration to the system or even amplify the response in the low-frequency vibration. To overcome these shortcomings, this paper proposes a new fine particle impact damper (FPID) which for the first time introduces the fine particle plastic deformation as an irreversible energy sink. Then, the experiments of the cantilevered beam with the CID and that with the FPID are, respectively, carried out to investigate the behavior of FPID. The experimental results indicate that the FPID has a better performance in vibration damping than in the CID and the FPID works well in control of the vibration with frequency lower than 50 Hz, which is absent to the non-obstructive particle damper. Thus, the FPID has a bright and significant application future because most of the mechanical vibration falls in the range of low freqency.

Modeling the fine particle impact damper

2010 ◽  
Vol 52 (7) ◽  
pp. 1015-1022 ◽  
Author(s):  
Yanchen Du ◽  
Shulin Wang
Keyword(s):  
Fine Particle ◽  
Particle Impact ◽  
Impact Damper

Evaluation of CFRP Hole Quality in Low Frequency Vibration-Assisted Dry Drilling of CFRP/Ti Stacks

2018 ◽  
Author(s):  
Haojun Yang ◽  
Yan Chen ◽  
Jiuhua Xu
Keyword(s):  
Feed Rate ◽  
Kinematic Model ◽  
Mechanical Damage ◽  
Low Frequency ◽  
Spindle Speed ◽  
Hole Quality ◽  
Drilling Force ◽  
Low Frequency Vibration ◽  
The Impact ◽  
Conventional Drilling

Low frequency vibration assisted drilling (LFVAD) is regarded as one of the most promising process in CFRP/Ti stacks drilling. This work carries the investigation of the difference between conventional drilling and LFVAD based on kinematic model. The experiments are conducted under varied vibration amplitude to a specific feed rate, also under varying spindle speeds, feed rates when the ratio of amplitude to feed rate is fixed. Then the hole quality of CFRP is evaluated based on the analysis of drilling force, chip morphology, chip extraction. The results show that there is rarely no difference between conventional drilling and LFVAD in drilling mechanism when the drilling diameter is over 1 mm. Because the impact effect caused by drill vibration is already weak. It is found that the severe mechanical damage of the CFRP holes surface could be significantly reduced due to the fragmented chips obtained in vibration drilling. The maximum instantaneous feed rate combined with feed rate and amplitude plays a significant role in CFRP hole quality. Lower maximum instantaneous feed rate results in better hole wall quality and less entry delamination. Spindle speed has no visible influence on entry delamination, while higher spindle speed improves the hole surface quality due to the resin coating phenomenon.

Investigation into the linear velocity response of cantilever beam embedded with impact damper

2019 ◽  
Vol 25 (7) ◽  
pp. 1365-1378 ◽  
Author(s):  
Yiqing Yang ◽  
Xi Wang
Keyword(s):  
Cantilever Beam ◽  
Continuous System ◽  
Linear Velocity ◽  
Superposition Method ◽  
Momentum Exchange ◽  
Impact Damper ◽  
Mode Superposition Method ◽  
Velocity Response ◽  
The Impact ◽  
Nonlinear Velocity

The impact damper causes momentum exchange between the primary structure and impact mass, and achieves vibration attenuation through repeated collisions. A cantilever beam embedded with the impact damper is modeled in the form of a continuous system, and the equations of motion are formulated based on the mode superposition method. The mechanism of the impact damper is investigated, and linear velocity response is achieved by a proper selection of a mass ratio of 8.4%, clearance within 0.30 mm, and excitation force ranged from 3.2 N to 5.5 N. The reverse collision has higher damping than co-directional collision, based on which a new criterion of response regimes is proposed for the design of the impact damper. The velocity responses of the damped cantilever beam under sinusoidal and impulse excitation are simulated and verified via the sinusoidal sweep experiments. The velocity amplitudes of the damped cantilever beam are linearly decreased when the clearance is increased within 0.30 mm. Finally, linear and nonlinear velocity responses of the damped cantilever beam are discussed. It is found that the nonlinear velocity response reaches larger damping, but that a strongly modulated response exists.

Measurements of Low Frequency Vibration in Subsea Piping Using ROV Video Analysis

2020 ◽  
Author(s):  
Andries van Wijhe ◽  
Lennert Buijs ◽  
Leszek Stachyra ◽  
Olivier Macchion
Keyword(s):  
Video Analysis ◽  
Video Processing ◽  
Production Systems ◽  
Mechanical Vibration ◽  
Water Injection ◽  
Low Frequency ◽  
Free Vibrations ◽  
Accelerometer Data ◽  
Lighting Condition ◽  
Low Frequency Vibration

Abstract Vibrations in Subsea Production Systems are well recognized as a concern in the subsea industry. To identify the severity of the vibrations and potential accumulated fatigue damage, subsea vibrations need to be measured with great accuracy. Currently, accurate detection and subsea measurements are often performed by utilizing accelerometers, which have to be connected to the structure by ROV or a diver. ROV video analysis provides an alternative solution. Video analyses are widely utilized across different applications. With the increased quality of a HD camera on ROV, the accessibility of such measurements is an attractive substitute to other techniques. As a part of on-shore mechanical testing on a full assembled XT in St John’s Canada, a flowloop on a water injection XT was subjected to free vibrations. The vibrations were filmed using a commercial HD camera placed on a tripod. This test was done to validate data generated using video processing in which pipe vibration of an operating subsea XT was filmed using an ROV camera. A study that aimed to quantify the video processing accuracy, limitations and provide general guidance was conducted. For the onshore test filmed with a tripod the results of video analyses were compared with the measurements obtained by means of accelerometers. For the video of an operating subsea XT filmed by an ROV, the obtained vibration frequency and direction was compared with the free mechanical vibration obtained by a FEM model. The results obtained by means of the video analysis matched well with the accelerometer data. A high accuracy was reached, as vibration displacements as low as 20% of the pixel were accurately determined in the video analysis. With respect to detection frequencies, the upper cut-off frequency was around 15 Hz determined by the video framerate. The video analysis utilizing ROV videos was found to be applicable for low frequency vibration measurements, opening the opportunity for easier and more cost effective vibration detection and monitoring. The method is also reliable for subsea application in which the camera is placed on an ROV and is thus not affected by ROV movements, subsea lighting condition and moving ocean debris.

Experimental study of passive vibration suppression using absorber with spherical ball impact damper

2016 ◽  
Vol 231 (17) ◽  
pp. 3193-3201 ◽  
Author(s):  
Riadh Chaari ◽  
Fathi Djemal ◽  
Fakher Chaari ◽  
Mohamed Slim Abbes ◽  
Mohamed Haddar
Keyword(s):  
Vibration Suppression ◽  
Industrial Applications ◽  
Design Parameters ◽  
Particle Impact ◽  
Ball Impact ◽  
Impact Damper ◽  
Ball Size ◽  
Wide Range ◽  
The Impact ◽  
Impact Damping

Impact dampers are efficient in many industrial applications with a wide range of frequencies. An experimental analysis of the impact damping of spherical balls is investigated to simplify the particle impact damping design and improve the vibration suppression. The objective of the study is to analyze some of the design parameters of impact damper using spherical balls. The experimental investigation consists to test the effect of the ball size for each mass level, the number of balls for each size level and different exciting force levels on vibrations of the main structure. The parametric study provided useful information to understand and optimize Particle Impact Damping design.

scholarly journals The Impact of Sound Exposure on Heart Rate Variability in Adolescent Students

2018 ◽  
pp. 695-702 ◽  
Author(s):  
M. VETERNIK ◽  
I. TONHAJZEROVA ◽  
J. MISEK ◽  
V. JAKUSOVA ◽  
H. HUDECKOVA ◽  
...  
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
Low Frequency ◽  
Sound Intensity ◽  
Sine Wave ◽  
Adolescent Students ◽  
Sound Exposure ◽  
Cardiac Autonomic Regulation ◽  
The Impact ◽  
First Time

Previous studies of physiological responses to music and noise showed the effect on the autonomic nervous system. The heart rate variability (HRV) has been used to assess the activation of the sympathetic and the parasympathetic nervous systems. The present study was aimed to examine HRV with exposure to four sine-wave pure tones (20 Hz, 50 Hz, 2 kHz and 15 kHz) in an environment where the sound intensity exceeded level 65 dB (A-weighted). The participants (20 adolescent girls) were lying in supine position during exposure protocol divided into 6 periods, the first time with generated sounds and the second time without sounds. In the protocol without sound exposure, the low frequency band of the HRV spectrum was increased compared to the basal state before examination (period_1: 6.05±0.29 ms2 compared to period_5: 6.56±0.20 ms2, p<0.05). The significant increase of root Mean Square of the Successive Differences (rMSSD, period_1: 4.09±0.16 s compared to period_6: 4.33±0.12 s, p<0.05) and prolongation of R to R peak (RR) interval (period_1: 889±30 ms compared to period_5: 973±30 ms, p<0.001) were observed in the protocol without sound exposure comparing to the protocol with sound exposure where only bradycardia was observed. Contrary to rather polemical data in literature our pilot study suggests that sounds (under given frequencies) have no impact on the heart rate variability and cardiac autonomic regulation.

Study on Looseness and Impact - Rub Coupling Faults of a Vertical Dual-Disk Cantilever Rotor- Bearing System

2007 ◽  
Vol 353-358 ◽  
pp. 2479-2482
Author(s):  
Yan Jun Lu ◽  
Zhao Hui Ren ◽  
Hong Chen ◽  
Nai Hui Song ◽  
Bang Chun Wen
Keyword(s):  
Finite Element ◽  
Low Frequency ◽  
Element Model ◽  
Coupling Faults ◽  
Mechanics Model ◽  
Low Frequency Vibration ◽  
Rotor Bearing ◽  
Impact And Rubbing ◽  
The Impact ◽  
Bearing System

Because of wrong setting or long-term running of rotating machinery, the looseness may ouur in the bearing seats or bases. And also bring impact and rubbing of rotor-stator, That is the looseness and rub-impact coupling fault. In the paper,a mechanics model and a finite element model of a vertical dual-disk cantilever rotor- bearing system with coupling faults of looseness and rub-impact are set up. Based on the nonlinear finite element method and contact theory, the dynamical characteristices of the system under the influence of the looseness rigidity and impact-rub clearance is studied. The results show that the impact-rub of rotor-stator can reduce the low frequency vibration caused by looseness, and the impact-rub caused by looseness has obvious orientation. Also, the conclusion of diagnosing the looseness and rub-impact coupling faults is given in the end of the paper.

A Novel Boat Shock Vibration Control using Momentum Exchange Principle with Pre-Straining Spring Mechanism

2020 ◽  
Vol 17 (2) ◽  
pp. 7858-7867
Author(s):  
L. Son ◽  
J. Malta ◽  
E. Satria ◽  
B. Yuliandra ◽  
H. Matsuhisa
Keyword(s):  
Wave Excitation ◽  
Momentum Exchange ◽  
Beam Structure ◽  
Mass System ◽  
Impact Damper ◽  
Vibration Attenuation ◽  
Spring Mechanism ◽  
The Impact ◽  
Impact Vibration ◽  
Better Than

This research proposes a new method for boat impact vibration attenuation using the exchange of momentum principle with a pre-straining spring mechanism. The boat dynamic is modeled using a hinged-supported beam structure. The wave excitation on the boat hull is expressed using one degree of freedom spring-mass system. The simulation study is performed to evaluate the impact damper performance in reducing the boat shock response. Two kinds of momentum exchange impact damper i.e., without and with pre-straining spring mechanism, are evaluated. The simulation results show that the impact damper with pre-straining spring mechanism (PSMEID) is better than the passive momentum exchange impact damper (PMEID) in reducing the boat shock vibration response

scholarly journals A new concept for UAV landing gear shock vibration control using pre-straining spring momentum exchange impact damper

2016 ◽  
Vol 24 (8) ◽  
pp. 1455-1468 ◽  
Author(s):  
Lovely Son ◽  
Mulyadi Bur ◽  
Meifal Rusli
Keyword(s):  
Landing Gear ◽  
Main Body ◽  
Force Transmission ◽  
Momentum Exchange ◽  
Lumped Mass ◽  
Maximum Acceleration ◽  
Impact Damper ◽  
Aerial Vehicle ◽  
Theoretical Application ◽  
The Impact

This study proposes a new method for reducing the shock vibration response of an Unmanned Aerial Vehicle (UAV) during the landing process by means of the momentum exchange principle (MEID). The performance of the impact damper is improved by adding a pre-straining spring to the damper system. This research discusses the theoretical application of the damper to the UAV landing gear system. The UAV dynamics is first modeled as a simple lumped mass translational vibration system. Then we analyze a more complex two-dimensional model of UAV dynamics. This model consists of the main wheel, nose wheel and main body. Three cases of UAV landing gear mechanisms: without damper, with passive MEID (PMEID) and with pre-straining spring MEID (PSMEID) are simulated. The damper performance is evaluated from the maximum acceleration and force transmission to the main body. The energy balance calculation is conducted to investigate the performance of PSMEID. The simulation results show that the proposed PSMEID method is the most effective method for reducing the maximum acceleration and force transmission of UAV during impact landing.

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