Numerical Calculation of Elastohydrodynamic Lubrication E-Book

Ping Huang

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 248

Veröffentlichungsjahr: 2015

Beschreibung

The book not only offers scientists and engineers a clear inter-disciplinary introduction and orientation to all major EHL problems and their solutions but, most importantly, it also provides numerical programs on specific application in engineering. * A one-stop reference providing equations and their solutions to all major elastohydrodynamic lubrication (EHL) problems, plus numerical programs on specific applications in engineering * offers engineers and scientists a clear inter-disciplinary introduction and a concise program for practical engineering applications to most important EHL problems and their solutions * brings together a number of case studies in one text, each being solved using solution methods which share common features and methods

Leseprobe

NUMERICAL CALCULATION OF ELASTOHYDRODYNAMIC LUBRICATION

METHODS AND PROGRAMS

Ping Huang

School of Mechanical and Automotive EngineeringSouth China University of TechnologyPeople’s Republic of China

This edition first published 2015

© 2015 by Tsinghua University Press. All rights reserved

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Library of Congress Cataloging-in-Publication Data

Huang, Ping, 1957–Numerical calculation of elastohydrodynamic lubrication : methods and programs / Ping Huang.           pages    cm     Includes bibliographical references and index.

     ISBN 978-1-118-92096-1 (cloth)1. Elastohydrodynamic lubrication.    2. Lubrication and lubricants–Mathematical models.    3. Tribology.    I. Title.     TJ1075.H68 2015     621.8′9–dc23

                      2015005240

A catalogue record for this book is available from the British Library.

Preface

The book is a companion book of Numerical Calculation of Elastohydrodynamic Lubrication: Methods and Programs [2] written by the author and his graduate students. Since its Chinese publication, it has been widely approved, so we felt necessary to write a book similar to that in elastohydrodynamic lubrication (EHL).

The present book is based on numerical methods and programs of EHL and it describes the calculation of isothermal and thermal EHL problems in line contact, point contact, and elliptical contact in detail. In addition, numerical calculations of some special problems of EHL, such as velocities in different directions, grease lubrication, electric double layer effect, unsteady state, rough surface, and micro-polar fluid are introduced as well.

EHL calculation has a very close relationship with practical engineering. For example, EHL exists in rolling contact bearings and gears. However, compared with calculation of hydrodynamic lubrication, EHL calculation is more difficult. This is because the Reynolds equation, elastic deformation equation, viscosity pressure equation, and energy equation should be solved simultaneously. As EHL solutions are always obtained through iterations, if the iteration method is inappropriately chosen, it often causes the calculation process to be divergent. In this book, we have chosen the more reliable iteration methods and have checked and confirmed that all the programs and examples provided give satisfactory results.

However, it must be noted that because of the complexities of EHL problems, an EHL program is commonly not universal, that is, when the working conditions change, the program may not be able to get a converged or satisfied solution when used directly. In such cases, the reader should note the following conditions.

Divergence for given accuracy:

There always exist some numerical errors in numerical calculation. If the accuracy given in the program cannot be met for some EHL problems, for example, double precision is not used, the calculation process may repeated at a lower level of accuracy. However, it is not really divergent. In such cases, although the accuracy does not meet the requirement, the result can be still considered as a converged solution so that the solution is useful.

No convergence due to limitation of iteration number:

In any iteration program, in addition to level of accuracy, in order not to calculate infinitely, a number must be set to limit the iteration loops. Therefore, although the iteration may have begun to converge, but the limitation of the iteration number has been reached, the calculation will be stopped. In this case, although the result is not convergent, the solution is available. If readers need a more accurate solution, he or she can increase the limitation of number of iterations.

Divergence for small calculation region:

The calculation region of EHL is generally set to be six times of the half width of the contact zone, where the inlet zone is about four times the half-width of the contact zone and the exit zone is about 1.5–2 times. Such a width generally meets the requirement to solve typical EHL problems. However, for some EHL problems, such as light-load, high-speed, high-viscosity, or non-Newtonian fluids, the length may be not large enough to bring the convergent result. For such a situation, please increase the calculation region so as to get a converged solution. However, this may usually bring loss of accuracy and the loss cannot be compensated by the approach to increase the node number.

Divergence for unsuitable problems:

The maximum contact pressure of EHL commonly is between 0.2 and 0.8 GPa in the line or point contacts. If the maximum pressure is very low or very high, the lubrication state may tend to be a hydrodynamic lubrication or the film thickness may be too thin. In such situations, the present EHL calculation programs are not suitable anymore. In such cases, if the reader cannot obtain a convergent solution, he or she must find an appropriate program suitable for his own problem.

Readers must note that most EHL calculation programs are not universal. It is necessary for a user to be familiar with the EHL properties, and modify the corresponding statements in the program accordingly to satisfy the calculation requirements. However, this does not affect the role of the book as it shares the same purpose of the book Numerical Calculation of Elastohydrodynamic Lubrication: Methods and Programs. That is, the authors hope to establish an EHL calculation platform so as to avoid repeated EHL calculations and help users to complete EHL calculations and obtain solutions more quickly.

This book is also written by Lai Tianmao (Section 2.3, Chapters 8 and 10), Yang Qianqian (Chapter 4), Wang Yazhen (Chapters 6 and 9), Chen Yingjun (Chapter 11), Bai Shaoxian and Zuo Qiyang (Chapter 12) and Zhang Wei (Chapter 13). Ping Huang is responsible for the remaining chapters and has edited the whole book. Due to time and scope limitations, errors and problems cannot be avoided entirely in the book. We hope that readers’ invaluable comments will help to further improve the subsequent editions of this book.

Ping Huang

Introduction

In this book, numerical methods and programs of elastohydrodynamic lubrication (EHL) are described. The contents of the book are divided into 15 chapters. In Chapters 1–3, basic numerical methods of EHL, numerical methods of elastic deformation, and numerical methods of energy equation are given, based on which the subsequent chapters are described. In Chapters 4–10, isothermal EHL problems in line contact, point contact, and elliptical contact are discussed, which are the basic and the most important contents in EHL calculation. Moreover, in Chapter 9, the EHL problem in the elliptical contact with different direction velocities is discussed. In Chapters 11–15, grease lubrication, electric double layer effect, unsteady EHL, rough surface and micro-polar fluid EHL are introduced, which are modified from the former and basic programs.

This book can serve as a textbook or a reference book for teachers and postgraduate students in mechanical engineering. It can be used as reference material for professional techniques in EHL computational analysis and engineering research as well.