Virtual Model of Gear Shaping—Part II: Elastic Deformations and Virtual Gear Metrology

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
Andrew Katz ◽  
Kaan Erkorkmaz ◽  
Fathy Ismail
Keyword(s):  
Cutting Tools ◽  
Transmission Error ◽  
Spur Gear ◽  
Tool Deflection ◽  
Time Step ◽  
Elastic Deflection ◽  
Major Factors ◽  
Shaping Part ◽  
The Right ◽  
Gear Shaping

Elastic deflection of cutting tools relative to the workpiece is one of the major factors contributing to dimensional part inaccuracies in machining. This paper examines the effect of tool deflection in gear shaping and its effect on the gear's profile form error, which can cause transmission error and noise during gear operation. To simulate elastic tool deflection in gear shaping, the tool's static stiffness is estimated from impact hammer testing. Then, based on simulated cutter-workpiece engagement and predicted cutting forces, the elastic deflection of the tool is calculated at each time-step. To examine the effect of tool deflection on the profile error of the gear, a virtual gear measurement module is developed and used to predict the involute profile deviations in the virtually machined part. Simulated and measured profile deviations were compared for a one-pass external spur gear process and a two-pass external spur gear process. The simulated profile errors correlate very well with the measured profiles on the left flanks of the workpiece teeth, which are cut by the leading edges of the cutter teeth. However, additional research is needed to improve the prediction of the right flanks, which are cut by the trailing edges of the cutter teeth.

Virtual Model of Gear Shaping—Part I: Kinematics, Cutter–Workpiece Engagement, and Cutting Forces

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
Andrew Katz ◽  
Kaan Erkorkmaz ◽  
Fathy Ismail
Keyword(s):  
Cutting Force ◽  
Cutting Forces ◽  
Spur Gear ◽  
Cutting Edge ◽  
Prediction Algorithm ◽  
Force Model ◽  
Time Step ◽  
Solid Modeler ◽  
Chip Geometry ◽  
Gear Shaping

Gear shaping is, currently, the most prominent method for machining internal gears, which are a major component in planetary gearboxes. However, there are few reported studies on the mechanics of the process. This paper presents a comprehensive model of gear shaping that includes the kinematics, cutter–workpiece engagement (CWE), and cutting forces. To predict the cutting forces, the CWE is calculated at discrete time steps using a tridexel discrete solid modeler. From the CWE in tridexel form, the two-dimensional (2D) chip geometry is reconstructed using Delaunay triangulation (DT) and alpha shape reconstruction. This in turn is used to determine the undeformed chip geometry along the cutting edge. The cutting edge is discretized into nodes with varying cutting force directions (tangential, feed, and radial), inclination angles, and rake angles. If engaged in the cut during a particular time-step, each node contributes an incremental force vector calculated with the oblique cutting force model. Using a three-axis dynamometer on a Liebherr LSE500 gear shaping machine tool, the cutting force prediction algorithm was experimentally verified on a variety of processes and gears, which included an internal spur gear, external spur gear, and external helical gear. The simulated and measured force profiles correlate closely with about 3–10% RMS error.

Dynamic Analysis of Contacting Spur Gear Pair for Fast System Simulation

2006 ◽  
Vol 110 ◽  
pp. 151-162 ◽  
Author(s):  
Daisuke Suzuki ◽  
Shigeru Horiuchi ◽  
Jin Hwan Choi ◽  
Han Sik Ryu
Keyword(s):  
System Simulation ◽  
Transmission Error ◽  
Spur Gear ◽  
Contact Analysis ◽  
Gear System ◽  
Force Model ◽  
Gear Pair ◽  
Time Step ◽  
Efficient System ◽  
Static Transmission Error

The prime source of vibration and noise in a gear system is originated from transmission error between the meshing gears. In this paper, the dynamic modeling method and response of a spur gear pair for the efficient system simulation are investigated by using a detailed contact analysis at each time step. Input values such as time-varying mesh stiffness and static transmission error excitation are not required in this investigation because mesh forces are obtained by contact analysis directly. The efficient contact search kinematics and algorithms in the context of the compliant contact model are developed to detect the interactions between teeth surfaces. In this investigation the compliant force model based on the Herzian law is employed using Coulomb friction force model, and dynamic transmission error (DTE) and mesh frequency values of contacting gear system are also illustrated.

Modeling the Nonlinear Vibration of a Spur Gear Pair

2000 ◽  
Author(s):  
R. G. Parker ◽  
S. M. Vijayakar ◽  
T. Imajou
Keyword(s):  
Finite Element ◽  
Transmission Error ◽  
Spur Gear ◽  
Tooth Surface ◽  
Nonlinear Phenomena ◽  
Gear Pair ◽  
Mesh Stiffness ◽  
Time Step ◽  
Mechanics Model ◽  
Wide Range

Abstract The dynamic response of a spur gear pair is investigated using a finite element/contact mechanics model that offers significant advantages for dynamic gear analyses. The gear pair is analyzed across a wide range of operating speeds and torques. Comparisons are made to other researchers’ published experiments that reveal complex nonlinear phenomena. The nonlinearity source is contact loss of the meshing teeth, which, in contrast to the prevailing understanding, occurs even for large torques despite use of high-precision gears. A primary feature of the modeling is that dynamic mesh forces are calculated using detailed contact analysis at each time step as the gears roll through mesh; there is no need to externally specify the excitation in the form of time-varying mesh stiffness, static transmission error input, or the like. A semi-analytical model near the tooth surface is matched to a finite element solution away from the tooth surface, and the computational efficiency that results permits dynamic analysis. Two single degree of freedom models are discussed briefly. While one gives encouragingly good results, the second, which appears to have better mesh stiffness modeling, gives poor comparisons with experiments. The results indicate the sensitivity of such models to changing mesh stiffness representations.

Harmonic Resonance Frequency Factor of Spur Gear System and Oscillation Reduction Approaches

2007 ◽  
Author(s):  
Jianping Wang ◽  
Pengfei Li ◽  
Ziying Wu ◽  
Minghong Zhang
Keyword(s):  
Parametric Excitation ◽  
Linear Time ◽  
Primary Resonance ◽  
Frequency Factor ◽  
Multiple Scale ◽  
Transmission Error ◽  
Spur Gear ◽  
High Order ◽  
Time Varying ◽  
Harmonic Resonance

In this study, a non-linear time-varying dynamic model of a spur gear pair system is used to investigate the dynamic behavior of the system by means of multiple scale approach. Both time-varying stiffness, transmission error and tooth backlash clearance of the system are taken into account in the model. The mesh stiffness fluctuation is developed as high order Fourier series and tooth backlash clearance is fitted by high order polynomial function. The frequency factors of the system are investigated and the frequency-response equations at the case of internal and external excitation, parametric excitation and combined excitation are obtained. The peak value of the amplitude of the primary resonance, super and sub harmonic resonance and combination harmonic under internal, external and parametric excitation are researched. The approaches of vibration reduction are investigated. Finally an example is investigated using the presented process and the results indicate the sensitivity and correctness of the presented analysis approaches.

Hard Nano-Crystalline Coatings for Cutting Tools

2007 ◽  
Vol 567-568 ◽  
pp. 185-188 ◽  
Author(s):  
Miroslav Piska
Keyword(s):  
High Speed ◽  
Metal Cutting ◽  
Cutting Tool ◽  
Cutting Tools ◽  
Dry Cutting ◽  
Nano Crystalline ◽  
The Right ◽  
Machining Productivity ◽  
Hard Cutting ◽  
Cutting Tool Materials

Modern trends in metal cutting, high speed/feed machining, dry cutting and hard cutting set more demanding characteristics for cutting tool materials. The exposed parts of the cutting edges must be protected against the severe loading conditions and wear. The most significant coatings methods for cutting tools are PVD and CVD/MTCVD today. The choice of the right substrate or the right protective coating in the specific machining operation can have serious impact on machining productivity and economy. In many cases the deposition of the cutting tool with a hard coating increases considerably its cutting performance and tool life. The coating protects the tool against abrasion, adhesion, diffusion, formation of comb cracks and other wear phenomena.

scholarly journals State-Building, Power-Sharing Discourse, and Political Autonomy of Minorities within Ethno-Nationalist Gloom in Sri Lanka

2016 ◽  
Vol 9 (1) ◽  
pp. 88
Author(s):  
Mohammad Agus Yusoff ◽  
Athambawa Sarjoon ◽  
Abd Rashid Abdul Wahab
Keyword(s):  
Sri Lanka ◽  
State Building ◽  
Power Sharing ◽  
Building Projects ◽  
Political Autonomy ◽  
Minority Ethnic Groups ◽  
Building Process ◽  
Ultimate Result ◽  
Major Factors ◽  
The Right

Positioning minority concerns within a power-sharing mechanism is a key issue that has been influential in Sri Lanka’s modern state-building process experimented from the later part of the colonial period. Throughout the post-independent era, most state-building projects were critically debated with regard to sharing political autonomy between the majority Sinhalese and the minorities. This study attempts to locate the claims and concerns of minorities seeking political autonomy in Sri Lanka’s state-building and power-sharing discourse. The study found that the state-building process in Sri Lanka has always been a struggle between establishing a majoritarian-ethno-nationalist hegemonic state system and preserving the right of minority ethnic groups to political power-sharing. The study further found that (a) insufficient emphasis given towards understanding power-sharing and federalism as a means to accommodate diverse interests and rights, including the political autonomy rights of minorities, (b) the opportunistic politics of opposition parties, and (c) the ethno-nationalist agenda of the majority Sinhalese were the major factors that have induced to undermine the minorities’ claims for political autonomy. The ultimate result of this is the continuous struggles by minorities to situate their political autonomy demands within Sri Lanka’s state-building and power-sharing discourse.

Low excitation spur gears with variable tip diameter

2021 ◽  
Vol 263 (5) ◽  
pp. 1275-1285
Author(s):  
Joshua Götz ◽  
Sebastian Sepp ◽  
Michael Otto ◽  
Karsten Stahl
Keyword(s):  
Transmission Error ◽  
Spur Gear ◽  
Low Noise ◽  
Spur Gears ◽  
Mesh Stiffness ◽  
Helical Gears ◽  
Axial Forces ◽  
Tooth Width ◽  
Drive Trains ◽  
Static Transmission Error

One important source of noise in drive trains are transmissions. In numerous applications, it is necessary to use helical instead of spur gear stages due to increased noise requirements. Besides a superior excitation behaviour, helical gears also show additional disadvantageous effects (e.g. axial forces and tilting moments), which have to be taken into account in the design process. Thus, a low noise spur gear stage could simplify design and meet the requirements of modern mechanical drive trains. The authors explore the possibility of combining the low noise properties of helical gears with the advantageous mechanical properties of spur gears by using spur gears with variable tip diameter along the tooth width. This allows the adjustment of the total length of active lines of action at the beginning and end of contact and acts as a mesh stiffness modification. For this reason, several spur gear designs are experimentally investigated and compared with regard to their excitation behaviour. The experiments are performed on a back-to-back test rig and include quasi-static transmission error measurements under load as well as dynamic torsional vibration measurements. The results show a significant improvement of the excitation behaviour for spur gears with variable tip diameter.

scholarly journals Changing Mindsets of Middle Level Officers in Government Organizations

2003 ◽  
Vol 28 (4) ◽  
pp. 63-76 ◽  
Author(s):  
S Ramnarayan
Keyword(s):  
Recent Change ◽  
Middle Level ◽  
Government Organizations ◽  
Governmental Organizations ◽  
Management Processes ◽  
New Strategy ◽  
Major Factors ◽  
The Individual ◽  
The Right ◽  
The Way

This paper uses a simple system of classification for examining mindsets of middle level officers in government organizations. It proposes that a middle level officer may assume or take on a spectator mindset or an actor mindset. With a spectator mindset, the person may pick up a signal from the environment or get an idea for improvement but he/she does not act on that learning or insight. As a result, organizational learning does not occur and this is reflected by organizational inaction or inappropriate action. On the other hand, with actor orientation, the individual acts on his/her learning and this leads to the right organizational action. This paper proposes that spectator orientation is rooted in four major factors: organizational characteristics nature of relations with superior the way work is performed the nature of middle management role. When the organization is perceived as conflict-ridden, rule bound, having too many free-riders and not oriented to customer and stakeholder requirements, there is a tendency for spectator mindset to predominate. This mindset also results in hierarchical, impersonal, and non-appreciative relations with superior. The third factor that leads to spectator mindset is the way work is performed. When the emphasis is more on performing activities in a ritualistic mode rather than to have impact and when there is inadequate attention to linkage, integration, and people management issues, spectator mindset is more likely. Finally, the nature of roles at operating levels such as fragmentation and segmentation of functions and excessive preoccupation with fix-it type of activities can lead to spectator orientation. Any attempt to change the mindset has to therefore address these four important factors. This paper reviews some change experiments and experiences in governmental organizations in India to propose two broad approaches to bring about organizational and mindset changes: Transformational approach which aims to bring about new strategy, management processes, and approaches by creating a new equilibrium for the organization. Continuous improvement approach which focuses on small doses of incremental changes that affect only part of the organization by modifying ways and means of doing work. It builds on the efforts of organizational members. This paper discusses these two approaches in some detail and examines the factors that are critical for the success of each of these approaches. It looks at how these approaches can also complement and strengthen each other. There can be no two opinions on how important it is to change mindsets in government organizations. This paper is an attempt to review some recent change experiences to shed some light on this important issue.

scholarly journals Numerical study of various geometries of breakwaters for the installation of floating wind turbines

2016 ◽  
Vol 13 (1) ◽  
pp. 27-37 ◽  
Author(s):  
Keyvan Esmaeelpour ◽  
Rouzbeh Shafaghat ◽  
Rezvan Alamian ◽  
Rasoul Bayani
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Numerical Study ◽  
Energy Resources ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Renewable Energy Resources ◽  
Time Step ◽  
Set Up ◽  
The Right

The everyday growing populations all over the world and the necessity of increase in consumption of fossil energies have made the human to discover new energy resources, which are clean, cheap and renewable. Wind energy is one of the renewable energy resources. Considerable wind speed has made settling of wind turbines at sea beneficial and appealing. For this purpose, choosing the appropriate plates to set up wind turbines on the surface of sea is necessary. Regarding the installation condition, by choosing suitable geometry for floating breakwaters, offshore wind turbine can be mounted on them. Suitable geometry of breakwater for multifunctional usage could be selected with analyzing and comparing pressure, force and moment produced by incoming waves. In this article, we implement boundary element method to solve governing differential equations by assuming potential flow. On the other hand, for promoting free surface in each time step, we employed Euler-Lagrangian method. Finally, to find the appropriate geometry for installing the wind turbine on the breakwater, moment and wave profile next to the right and left side of breakwater body are calculated. Among simulated geometries, breakwater with trapezoid geometry which its larger base is placed in the water has more sustainability and it is the most suitable geometry for wind turbine installation.

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