Joint Clearances With Lubricated Long Bearings in Multibody Mechanical Systems

1999 ◽  
Vol 122 (4) ◽  
pp. 484-488 ◽  
Author(s):  
P. Ravn ◽  
S. Shivaswamy ◽  
B. J. Alshaer ◽  
Hamid M. Lankarani
Keyword(s):  
Mechanical Systems ◽  
Steady Motion ◽  
Joint Clearance ◽  
Hydrodynamic Theory ◽  
Viscous Effects ◽  
Analysis And Design ◽  
Joint Clearances ◽  
The Impact ◽  
Crank Mechanism ◽  
Hydrodynamic Theory Of Lubrication

Proper modeling of joint clearance is of great importance in the analysis and design of multibody mechanical systems. The clearance may be due to wear or imperfection in manufacturing. When there is no lubricant in the clearance, solid-to-solid contact occurs. The impulse due to contact between the links is transmitted throughout the system. The presence of a lubricant avoids such contact, as the hydrodynamic forces developed by the lubricant film support the loads acting on the bodies and prevent the bodies from coming into contact. In this paper, an analysis of revolute joint clearances in multibody mechanical systems with and without lubricant is presented. Squeeze as well as viscous effects are considered utilizing the hydrodynamic theory of lubrication in long bearings. Unlike the traditional machine design approach, the instantaneous lubricant forces are the unknown and evaluated in terms of the known geometrical position and velocity of the journal and bearing. In the case of analysis of a joint clearance with no lubricant, a modified Hertzian relation is used to model the impact or contact between the journal and bearing, which includes a hysteresis damping term to account for the energy dissipation during impact. The methodology is applied for the analysis of a slider-crank mechanism having a clearance in the piston pin. The simulations are carried out with and without lubricant and the results are compared. It is shown that the lubricant results in a steady motion with fewer peaks in the required cranking moment for the system. [S1050-0472(00)01804-3]

Treatment of Lubrication in Long Bearings for Joint Clearances in Multibody Mechanical Systems

1999 ◽  
Author(s):  
P. Ravn ◽  
S. Shivaswamy ◽  
H. M. Lankarani
Keyword(s):  
Mechanical Systems ◽  
Steady Motion ◽  
Machine Design ◽  
Joint Clearance ◽  
Hydrodynamic Theory ◽  
Solid Contact ◽  
Damping Term ◽  
Joint Clearances ◽  
The Impact ◽  
Crank Mechanism

Abstract Proper modeling of joint clearance is of great importance in the analysis of multibody mechanical systems. The clearance may be due to wear or imperfection in manufacturing. When there is no lubricant in the clearance, solid-to-solid contact occurs. The impulse due to contact between the links is transmitted throughout the system. The presence of a lubricant avoids such contact, as the hydrodynamic forces developed by the lubricant film supports the loads acting on the bodies and prevents the bodies from coming into contact. In this paper, an analysis of revolute joint clearances in multibody mechanical systems with and without lubricant is presented. Hydrodynamic theory of long bearing is utilized in this study. Unlike the traditional machine design approach, the instantaneous lubricant forces are the unknown and evaluated in terms of the known geometrical position and velocity of the journal and bearing. In the case of analysis of a joint clearance with no lubricant, a modified Hertzian relation is used to model the impact or contact between the journal and bearing, which includes a hysteresis damping term to account for the energy dissipation during impact. The methodology is applied for the analysis of a slider-crank mechanism having a clearance in the piston pin. The simulations are carried out with and without lubricant and the results are compared. It is shown that the lubricant results in a steady motion with fewer peaks in the required cranking moment for the system.

Dynamic Behavior of a Revolute Clearance Joint in Multibody Mechanical Systems

2003 ◽  
Author(s):  
P. Flores ◽  
H. M. Lankarani ◽  
J. Ambro´sio ◽  
J. C. P. Claro
Keyword(s):  
Mechanical Systems ◽  
Force Model ◽  
Continuous Contact ◽  
Revolute Clearance Joint ◽  
Regular Motion ◽  
Clearance Joint ◽  
Contact Force Model ◽  
The Coefficient Of Friction ◽  
The Impact ◽  
Crank Mechanism

This work describes the influence of the clearance size and the coefficient of friction on the dynamic response of a revolute clearance joint in multibody mechanical systems. When there is a clearance in a revolute joint, impacts between the journal and the bearing can occur, and consequently, local deformations take place. The impact is internal and the response of the system is performed using a continuous contact force model. The friction effect due to the contact between joint elements is also modeled. The clearance size and friction effects are analyzed separately. Through the use of Poincare´ maps both periodic and chaotic responses of the system are observed. The results predict the existence of the periodic or regular motion at certain clearance sizes and friction coefficients and chaotic or nonlinear in other cases. A detailed discussion of the results relative to a planar slider-crank mechanism with a revolute clearance joint is presented.

Uncertainty of Coupler Point Position of Slider Crank Mechanisms

2015 ◽  
Author(s):  
Zetao Yu ◽  
Kwun-Lon Ting ◽  
Kuan-Lun Hsu ◽  
Jun Wang ◽  
Wesley Waggoner
Keyword(s):  
Geometric Model ◽  
Joint Clearance ◽  
Link Length ◽  
Position Uncertainty ◽  
Prismatic Joint ◽  
Point Position ◽  
Joint Clearances ◽  
Crank Mechanism ◽  
Short Link

In this paper, a novel geometric model for a planar slider-crank mechanism is established to quantify the position uncertainty of a coupler point caused by joint clearances. The clearance of each revolute and prismatic joint is characterized by a short clearance link. The prismatic joint with clearance is modeled as a link with infinite link length and a variable short link. The linkage with joint clearance is thus modeled as one with redundant freedom. The uncertainty is the result of the redundancy and the extremity of the redundancy is determined through Ting’ N-bar rotatability laws.

scholarly journals Performance Analysis and Design Considerations of the Shallow Underwater Optical Wireless Communication System with Solar Noises Utilizing a Photon Tracing-Based Simulation Platform

Electronics ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 632
Author(s):  
Xiaozheng Wang ◽  
Minglun Zhang ◽  
Hongyu Zhou ◽  
Xiaomin Ren
Keyword(s):  
Performance Analysis ◽  
Wireless Communication ◽  
Ambient Noise ◽  
Large Scale ◽  
Delay Spread ◽  
Simulation Platform ◽  
Optical Wireless Communication ◽  
Optical Wireless ◽  
Analysis And Design ◽  
The Impact

The performance of the underwater optical wireless communication (UOWC) system is highly affected by seawater´s inherent optical properties and the solar radiation from sunlight, especially for a shallow environment. The multipath effect and degradations in signal-to-noise ratio (SNR) due to absorption, scattering, and ambient noises can significantly limit the viable communication range, which poses key challenges to its large-scale commercial applications. To this end, this paper proposes a unified model for underwater channel characterization and system performance analysis in the presence of solar noises utilizing a photon tracing algorithm. Besides, we developed a generic simulation platform with configurable parameters and self-defined scenarios via MATLAB. Based on this platform, a comprehensive investigation of underwater channel impairments was conducted including temporal and spatial dispersion, illumination distribution pattern, and statistical attenuation with various oceanic types. The impact of ambient noise at different operation depths on the bit error rate (BER) performance of the shallow UOWC system was evaluated under typical specifications. Simulation results revealed that the multipath dispersion is tied closely to the multiple scattering phenomenon. The delay spread and ambient noise effect can be mitigated by considering a narrow field of view (FOV) and it also enables the system to exhibit optimal performance on combining with a wide aperture.

scholarly journals On the Effectiveness of Sampling for Evolutionary Optimization in Noisy Environments

2018 ◽  
Vol 26 (2) ◽  
pp. 237-267 ◽  
Author(s):  
Chao Qian ◽  
Yang Yu ◽  
Ke Tang ◽  
Yaochu Jin ◽  
Xin Yao ◽  
...  
Keyword(s):  
Negative Impact ◽  
Fitness Function ◽  
Evolutionary Optimization ◽  
Function Evaluation ◽  
Noisy Optimization ◽  
Running Time ◽  
Analysis And Design ◽  
True Value ◽  
Wide Range ◽  
The Impact

In real-world optimization tasks, the objective (i.e., fitness) function evaluation is often disturbed by noise due to a wide range of uncertainties. Evolutionary algorithms are often employed in noisy optimization, where reducing the negative effect of noise is a crucial issue. Sampling is a popular strategy for dealing with noise: to estimate the fitness of a solution, it evaluates the fitness multiple ([Formula: see text]) times independently and then uses the sample average to approximate the true fitness. Obviously, sampling can make the fitness estimation closer to the true value, but also increases the estimation cost. Previous studies mainly focused on empirical analysis and design of efficient sampling strategies, while the impact of sampling is unclear from a theoretical viewpoint. In this article, we show that sampling can speed up noisy evolutionary optimization exponentially via rigorous running time analysis. For the (1[Formula: see text]1)-EA solving the OneMax and the LeadingOnes problems under prior (e.g., one-bit) or posterior (e.g., additive Gaussian) noise, we prove that, under a high noise level, the running time can be reduced from exponential to polynomial by sampling. The analysis also shows that a gap of one on the value of [Formula: see text] for sampling can lead to an exponential difference on the expected running time, cautioning for a careful selection of [Formula: see text]. We further prove by using two illustrative examples that sampling can be more effective for noise handling than parent populations and threshold selection, two strategies that have shown to be robust to noise. Finally, we also show that sampling can be ineffective when noise does not bring a negative impact.

Numerical Study of Viscous Flows Inside Partially Filled Spinning and Coning Cylinders

1996 ◽  
Vol 118 (2) ◽  
pp. 335-340 ◽  
Author(s):  
Mohamed Selmi
Keyword(s):  
Stokes Equations ◽  
Numerical Study ◽  
Center Of Mass ◽  
Steady Motion ◽  
Practical Interest ◽  
Nonlinear Effects ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Practical Applications ◽  
Analysis And Design

This paper is concerned with the solution of the 3-D-Navier-Stokes equations describing the steady motion of a viscous fluid inside a partially filled spinning and coning cylinder. The cylinder contains either a single fluid of volume less than that of the cylinder or a central rod and a single fluid of combined volume (volume of the rod plus volume of the fluid) equal to that of the cylinder. The cylinder rotates about its axis at the spin rate ω and rotates about an axis that passes through its center of mass at the coning rate Ω. In practical applications, as in the analysis and design of liquid-filled projectiles, the parameter ε = τ sin θ, where τ = Ω/ω and θ is the angle between spin axis and coning axis, is small. As a result, linearization of the Navier-Stokes equations with this parameter is possible. Here, the full and linearized Navier-Stokes equations are solved by a spectral collocation method to investigate the nonlinear effects on the moments caused by the motion of the fluid inside the cylinder. In this regard, it has been found that nonlinear effects are negligible for τ ≈ 0.1, which is of practical interest to the design of liquid-filled projectiles, and the solution of the linearized Navier-Stokes equations is adequate for such a case. However, as τ increases, nonlinear effects increase, and become significant as ε surpasses about 0.1. In such a case, the nonlinear problem must be solved. Complete details on how to solve such a problem is presented.

The Impact Analysis of Revolute Pair Clearance to the End Pose Accuracy of Welding Robot

2015 ◽  
Vol 778 ◽  
pp. 259-263
Author(s):  
Fa Jun Zhang ◽  
Lin Zi Li ◽  
Hui Lin ◽  
Yin Lin Pu ◽  
Zhu Xin
Keyword(s):  
Mathematical Model ◽  
Impact Analysis ◽  
Joint Clearance ◽  
Welding Robot ◽  
Movement Characteristic ◽  
Movement Stability ◽  
Simulation Results ◽  
The Impact ◽  
The Mathematical Model ◽  
Welding Position

Various uncertain factors affect the movement of the welding robot, thus welding gun tend to deviate from the theory of welding position which reduces the welding accuracy, of which the revolute pair clearance have an greater effect on the movement of the welding robot. In order to study the influence of revolute pair clearance to the end pose accuracy of welding robot, the mathematical model of revolute pair clearance was established, and the software SolidWorks was used for establishing the welding robot model, making simulations of the mechanical arm with joint clearance and no joint clearance. At last, the movement characteristic of the hinge shaft is attained. The simulation results showed that the shaft velocity and displacement of mechanical arm with joint clearance has a certain degree of fluctuation, which affecting the end pose accuracy of welding robot , and reducing the movement stability and the welding accuracy of welding robot.

Perancangan Kampanye Sosial Dampak Game Online Bagi Remaja Di Kota Palembang

2020 ◽  
Vol 5 (2) ◽  
Author(s):  
Sapar Junoko
Keyword(s):  
Computer Games ◽  
Technological Development ◽  
Online Games ◽  
Media Planning ◽  
Analysis And Design ◽  
Planning Methods ◽  
Negative Impacts ◽  
Identification Analysis ◽  
The Impact ◽  
The City

<div class="page" title="Page 1"><div class="layoutArea"><div class="column"><p><span>Technological progress is something that can not be avoided in today's life. One of the results of technological development is the internet, one of its benefits is as a means of entertainment, for example to play online games. Online games themselves are not only played from computer games but can also be played on smartphones, online games are much loved by teenagers because online games themselves are a means of entertainment for them but most teenagers are addicted to playing online games. Online games themselves have positive and negative impacts, but if playing excessive online games can have positive impacts which are definitely addicted to playing continuously. The main study of this research focuses on the identification, analysis and design of Video Motion Graphic works and other supporting media. This design uses premedia media planning methods, playing media and media follow-up. Data collected through, observation, interviews, literature and website. The data is then identified, classified, selected, then analyzed using the 5W + 1H method and interpreted according to the text and context. The design of the social media campaign of the impact of online games for teens in the city of Palembang as a visual communication media which is part of the design discussion. This design aims to encourage adolescents to reduce and reduce the number of addictions due to online games especially teenagers in the city of Palembang in order to be able to balance between playing online games and learning to get achievements in education. </span></p></div></div></div>

Aerodynamic Optimization Design of Airfoil Shape Using Entropy Generation as an Objective

2018 ◽  
Vol 11 (2) ◽  
Author(s):  
Wei Wang ◽  
Jun Wang ◽  
Xiao-Pei Yang ◽  
Yan-Yan Ding
Keyword(s):  
Entropy Generation ◽  
Energy Cost ◽  
Optimization Design ◽  
Generation Rate ◽  
Entropy Generation Rate ◽  
Aerodynamic Optimization ◽  
Analysis And Design ◽  
Constraint Model ◽  
The Impact ◽  
Drag Ratio

Abstract An entropy analysis and design optimization methodology is combined with airfoil shape optimization to demonstrate the impact of entropy generation on aerodynamics designs. In the work herein, the entropy generation rate is presented as an extra design objective along with lift-drag ratio, while the lift coefficient is the constraint. Model equation, which calculates the local entropy generation rate in turbulent flows, is derived by extending the Reynolds-averaging of entropy balance equation. The class-shape function transform (CST) parametric method is used to model the airfoil configuration and combine the radial basis functions (RBFs) based mesh deformation technique with flow solver to compute the quantities such as lift-drag ratio and entropy generation at the design condition. From the multi-objective solutions which represent the best trade-offs between the design objectives, one can select a set of airfoil shapes with a low relative energy cost and with improved aerodynamic performance. It can be concluded that the methodology of entropy generation analysis is an effective tool in the aerodynamic optimization design of airfoil shape with the capability of determining the amount of energy cost.

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