On the Impact Intensity of Vibrating Axially Moving Roller Chains

1992 ◽  
Vol 114 (3) ◽  
pp. 397-403 ◽  
Author(s):  
K. W. Wang ◽  
S. P. Liu ◽  
S. I. Hayek ◽  
F. H. K. Chen
Keyword(s):  
Chain Structure ◽  
Momentum Balance ◽  
System Response ◽  
Roller Chain ◽  
Impulse Function ◽  
Static Approach ◽  
Axially Moving ◽  
Local Impacts ◽  
The Impact ◽  
Chain Drives

Experimental observation has shown that the most significant noise source in roller chain drives is from the impacts between the chain and the sprocket during their meshing process. Despite its importance, studies have not been made to thoroughly analyze the chain/sprocket impact dynamics and their interaction with the vibrating, axially moving chain structure. This paper presents a novel analysis which integrates the local meshing phenomena with the global system. An axially moving chain interacting with local impacts has been modelled and the momentum balance method is employed to derive the impulse function. A study is carried out to quantify the intensity of subsequent impacts. It is found that the impact intensity is significantly affected by the vibration characteristics and response of the moving chain, and vice versa. The classical quasi-static approach will create errors in predicting the impulse magnitude and system response. Meshing frequencies that will cause maximum and minimum impulses are analytically predicted. This fundamental investigation provides new insight into roller chain dynamics, which is an essential step toward the design of quiet chain drives.

On the Impact Intensity of Vibrating Axially Moving Roller Chains

1991 ◽  
Author(s):  
K. W. Wang ◽  
S. P. Liu ◽  
S. I. Hayek ◽  
F. H. K. Chen
Keyword(s):  
Chain Structure ◽  
Momentum Balance ◽  
System Response ◽  
Roller Chain ◽  
Impulse Function ◽  
Static Approach ◽  
Axially Moving ◽  
Local Impacts ◽  
The Impact ◽  
Chain Drives

Abstract Experimental observation has shown that the most significant noise source in roller chain drives is from the impacts between the chain and the sprocket during their meshing process. Despite its importance, studies have not been made to thoroughly analyze the chain/sprocket impact dynamics and their interaction with the vibrating, axially moving chain structure. This paper presents a novel analysis which integrates the local meshing phenomena with the global system. An axially moving chain interacting with local impacts has been modelled and the momentum balance method is employed to derive the impulse function. Convergence of the impulse function is examined and a study is carried out to quantify the intensity of subsequent impacts. It is found that the impact intensity is significantly affected by the vibration characteristics and response of the moving chain, and vice versa. The classical quasi-static approach will create errors in predicting the impulse magnitude and system response. This fundamental investigation provides new insight to roller chain dynamics, which is an essential step toward the design of quiet chain drives.

scholarly journals Vibration of Roller Chain Drives at Low, Medium and High Operating Speeds

1993 ◽  
Author(s):  
Woosuk Choi ◽  
Glen E. Johnson
Keyword(s):  
Boundary Conditions ◽  
Transverse Vibration ◽  
Equations Of Motion ◽  
Time Dependent ◽  
Partial Differential ◽  
Periodic Load ◽  
Roller Chain ◽  
Axially Moving ◽  
The Impact ◽  
Chain Drives

Abstract A model based on axially moving material is developed to study transverse vibration in roller chain drives. A unique feature of the work presented in this study is that impact, polygonal action and external periodic load have been included through chain tension and boundary conditions and periodic length change is also considered. The impact between the engaging roller and sprocket surface is modeled as a single impact between two elastic bodies and the modeling of the polygonal action is based on a four bar mechanism (rigid four bar at low speeds, elastic four bar at moderate and high speeds). At low and medium operating speeds, the system equation of motion for the chain span is expressed as a mixed type partial differential equation with time-dependent coefficients and time-dependent boundary conditions. At high operating speeds, the system equations of motion are two partial differential equations for transverse and longitudinal vibrations respectively and they are nonlinearly coupled The effects on transverse vibration of center distance, the moment of inertia of the driven sprocket system, static tension, and external periodic load are presented and discussed. Solutions are obtained by a finite difference method and Galerkin’s method.

Dynamics of High Speed Roller Chain Drives

1995 ◽  
Author(s):  
Peter Fritz ◽  
Friedrich Pfeiffer
Keyword(s):  
High Speed ◽  
Contact Forces ◽  
System Structure ◽  
Unilateral Constraints ◽  
Roller Chain ◽  
Contact Configuration ◽  
Nonlinear Force ◽  
A Chain ◽  
The Impact ◽  
Chain Drives

Abstract This paper deals with roller chain drives applied in combustion engines. In order to find characteristics for an optimal design, all components of a chain drive are taken into account. For a detailed analysis of the chain strand vibrations and the contact configurations each chain link, sprocket and guide is treated as a separate body. A nonlinear force element describes the joint forces, including elasticity, damping, backlash and oil-displacement. To determine real contact forces between a link and a sprocket or a guide, the exact contour and the mutual dependence of the contacts are considered. The impact of one link may influence the other links in such a manner that their contact configuration may change. In the mechanical model these contacts are represented by unilateral constraints. Applying the formulation of the linear complementarities including additional inequality conditions, the determination of a valid contact configuration after a change in the system structure is simplified.

Design and Construction of a Machine to Evaluate the Forces in Roller Chain Drives

1992 ◽  
Author(s):  
James C. Conwell ◽  
Glen E. Johnson ◽  
S. W. Peterson
Keyword(s):  
Experimental Investigation ◽  
Impact Force ◽  
Normal Operation ◽  
Test Machine ◽  
Chain Drive ◽  
Roller Chain ◽  
Wide Range ◽  
The Impact ◽  
Chain Drives ◽  
Design And Construction

Abstract In this article, a brief history of chain drives is presented, and the design and construction of a machine to investigate chain drive force phenomena is discussed. The new test machine allows the measurement of the impact force between a roller and the sprocket during “seating” and it can also be used to measure the forces that exist in the link sides plates during normal operation (including start-up and shut down conditions). Data can be obtained for a wide range of chain loads and speeds. Two companion papers (“Experimental Investigation of the Impact Force that Occurs When a Roller Seats on the Sprocket During Normal Operation of a Roller Chain Drive” and “Experimental Investigation of the Forces in a Link Side Plate During Normal Operation of a Roller Chain Drive”, both presented at this conference) describe experiments that have been completed with this test machine.

Reduction of Noise and Vibration in Roller Chain Drives

1977 ◽  
Vol 191 (1) ◽  
pp. 363-370 ◽  
Author(s):  
S. W. Nicol ◽  
J. N. Fawcett
Keyword(s):  
High Frequency ◽  
Noise Level ◽  
Experimental Tests ◽  
Chain Drive ◽  
Noise And Vibration ◽  
High Frequency Vibration ◽  
Roller Chain ◽  
Guide Device ◽  
The Impact ◽  
Chain Drives

Particularly at the higher sprocket speeds, one of the main sources of noise and high-frequency vibration in a roller chain drive is the impact which occurs each time the driving sprocket collects a roller from the chain span. A method of guiding the chain so as to virtually eliminate these impacts is described. Details are given of experimental tests in which a simply-constructed guide device greatly reduced the amplitude of the high-frequency vibration of a drive, and produced a very significant lowering of the noise level.

scholarly journals Advanced Constitutive Modeling of the Thixotropic Elasto-Visco-Plastic Behavior of Blood: Steady-State Blood Flow in Microtubes

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 367
Author(s):  
Konstantinos Giannokostas ◽  
Yannis Dimakopoulos ◽  
Andreas Anayiotos ◽  
John Tsamopoulos
Keyword(s):  
Blood Flow ◽  
Steady State ◽  
Constitutive Model ◽  
Blood Plasma ◽  
Constitutive Modeling ◽  
Flow Direction ◽  
Momentum Balance ◽  
Plastic Behavior ◽  
Flow Investigation ◽  
The Impact

The present work focuses on the in-silico investigation of the steady-state blood flow in straight microtubes, incorporating advanced constitutive modeling for human blood and blood plasma. The blood constitutive model accounts for the interplay between thixotropy and elasto-visco-plasticity via a scalar variable that describes the level of the local blood structure at any instance. The constitutive model is enhanced by the non-Newtonian modeling of the plasma phase, which features bulk viscoelasticity. Incorporating microcirculation phenomena such as the cell-free layer (CFL) formation or the Fåhraeus and the Fåhraeus-Lindqvist effects is an indispensable part of the blood flow investigation. The coupling between them and the momentum balance is achieved through correlations based on experimental observations. Notably, we propose a new simplified form for the dependence of the apparent viscosity on the hematocrit that predicts the CFL thickness correctly. Our investigation focuses on the impact of the microtube diameter and the pressure-gradient on velocity profiles, normal and shear viscoelastic stresses, and thixotropic properties. We demonstrate the microstructural configuration of blood in steady-state conditions, revealing that blood is highly aggregated in narrow tubes, promoting a flat velocity profile. Additionally, the proper accounting of the CFL thickness shows that for narrow microtubes, the reduction of discharged hematocrit is significant, which in some cases is up to 70%. At high pressure-gradients, the plasmatic proteins in both regions are extended in the flow direction, developing large axial normal stresses, which are more significant in the core region. We also provide normal stress predictions at both the blood/plasma interface (INS) and the tube wall (WNS), which are difficult to measure experimentally. Both decrease with the tube radius; however, they exhibit significant differences in magnitude and type of variation. INS varies linearly from 4.5 to 2 Pa, while WNS exhibits an exponential decrease taking values from 50 mPa to zero.

scholarly journals Vibro-Acoustical Sensitivities of Stiffened Aircraft Structures Due to Attached Mass-Spring-Dampers with Uncertain Parameters

Aerospace ◽  
2021 ◽  
Vol 8 (7) ◽  
pp. 174
Author(s):  
Johannes Seidel ◽  
Stephan Lippert ◽  
Otto von Estorff
Keyword(s):  
System Response ◽  
Fuzzy Arithmetic ◽  
Parameter Uncertainties ◽  
Excitation Spectra ◽  
Radiated Noise ◽  
Linking Elements ◽  
Manufacturing Tolerances ◽  
Suitable Framework ◽  
Mass Spring ◽  
The Impact

The slightest manufacturing tolerances and variances of material properties can indeed have a significant impact on structural modes. An unintentional shift of eigenfrequencies towards dominant excitation frequencies may lead to increased vibration amplitudes of the structure resulting in radiated noise, e.g., reducing passenger comfort inside an aircraft’s cabin. This paper focuses on so-called non-structural masses of an aircraft, also known as the secondary structure that are attached to the primary structure via clips, brackets, and shock mounts and constitute a significant part of the overall mass of an aircraft’s structure. Using the example of a simplified fuselage panel, the vibro-acoustical consequences of parameter uncertainties in linking elements are studied. Here, the fuzzy arithmetic provides a suitable framework to describe uncertainties, create combination matrices, and evaluate the simulation results regarding target quantities and the impact of each parameter on the overall system response. To assess the vibrations of the fuzzy structure and by taking into account the excitation spectra of engine noise, modal and frequency response analyses are conducted.

Impurity leakage and radiative cooling in the first nitrogen and neon seeding study in the slot divertor at DIII-D

2021 ◽  
Author(s):  
Livia Casali ◽  
David Eldon ◽  
Adam G McLean ◽  
Tom H Osborne ◽  
Anthony W Leonard ◽  
...  
Keyword(s):  
Experimental Studies ◽  
Mean Free Path ◽  
Flow Reversal ◽  
Momentum Balance ◽  
Ionization Source ◽  
Power Flux ◽  
Impurity Transport ◽  
Plasma Drifts ◽  
High Level ◽  
The Impact

Abstract A comparative study of nitrogen versus neon has been carried out to analyze the impact of the two radiative species on power dissipation, SOL impurity distribution, divertor and pedestal characteristics. The experimental results show that N remains compressed in the divertor, thereby providing high radiative losses without affecting the pedestal profiles and displacing carbon as dominant radiator. Neon, instead, radiates more upstream than N thus reducing the power flux through the separatrix leading to a reduced ELM frequency and compression in the divertor. A significant amount of neon is measured in the plasma core leading to a steeper density gradient. The different behaviour between the two impurities is confirmed by SOLPS-ITER modelling which for the first time at DIII-D includes multiple impurity species and a treatment of full drifts, currents and neutral-neutral collisions. The impurity transport in the SOL is studied in terms of the parallel momentum balance showing that N is mostly retained in the divertor whereas Ne leaks out consistent with its higher ionization potential and longer mean free path. This is also in agreement with the enrichment factor calculations which indicate lower divertor enrichment for neon. The strong ionization source characterizing the SAS divertor causes a reversal of the main ions and impurity flows. The flow reversal together with plasma drifts and the effect of the thermal force contribute significantly in the shift of the impurity stagnation point affecting impurity leakage. This work provides a demonstration of the impurity leakage mechanism in a closed divertor structure and the consequent impact on pedestal. Since carbon is an intrinsic radiator at DIII-D, in this paper we have also demonstrated the different role of carbon in the N vs Ne seeded cases both in the experiments and in the numerical modeling. Carbon contributes more when neon seeding is injected compared to when nitrogen is used. Finally, the results highlight the importance of accompanying experimental studies with numerical modelling of plasma flows, drifts and ionization profile to determine the details of the SOL impurity transport as the latter may vary with changes in divertor regime and geometry. In the cases presented here, plasma drifts and flow reversal caused by high level of closure in the slot upper divertor at DIII-D play an important role in the underlined mechanism.

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