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A Contact Fatigue Model Of Ellipsoidal Inhomogeneities By Method Of Images

Posted on:2022-05-14Degree:MasterType:Thesis
Country:ChinaCandidate:J L LiFull Text:PDF
GTID:2492306536969049Subject:Engineering (aeronautical engineering)
Abstract/Summary:PDF Full Text Request
The service performance of machine parts plays an important role in the development of national economy.With the progressive innovation of science and technology,the comprehensive requirements for high-performance materials in aerospace,wind power,metallurgy,automobile and many other fields are becoming increasingly stringent.However,due to the existence of cracks,holes,inclusions and other second phase components,most engineering materials are heterogeneous in the micro level.Contact fatigue is the major mode detected in failures of gear,bearing and other mechanical transmission parts.In order to improve the safety and reliability of machine components under extreme working conditions,it is of practical value to explore the contact fatigue mechanism of heterogeneous materials.The life prediction based on fatigue failure is helpful to improve the manufacturing process and service performance of mechanical parts,and consequently their high reliability and long service lifeThe mechanics involving a surface boundary(e.g.,half-space model)is of significance for developing the contact fatigue analyses.However,it is difficult if not impossible to solve a general half-space inclusion problem analytically.To the best of the author’s knowledge,analytical solution has only been obtained for an ellipsoidal inclusion subjected uniform dilatational eigenstrain(i.e.thermal inclusion)in an elastic half-space.To circumvent the complexity of analytical studies,method of images is applied comprehensively in this work to handle the half-space inclusion problems.In conjunction with the contact fatigue life model,a quantitative study is conducted to explore the influences of the inclusion contents on the life prediction of an engineering material subjected contact fatigue.First,the classical solution for an ellipsoidal inclusion in an infinite space is introduced,and a specific example of a thermal inclusion is presented.With the assistance of the elementary contact solution,the half-space thermal inclusion is solved in view of method of images,whose effectiveness and accuracy is then validated with the analytical solutions in literature.The capability of method of images in solving an elastic half-space containing multiple ellipsoidal inclusions is further exemplified.Secondly,a numerical discretization scheme using the elementary solution of a cuboidal inclusion is adopted as an alternative approach for solving the half-space containing an ellipsoidal inclusion.The resulting stresses of an ellipsoidal inclusion in a semi-infinite space are solved by both the numerical discretization method and method of images,demonstrating sufficient agreement.It is noted that method of images shows much excellent computational efficiency because it does not need to discretize the ellipsoid in three dimensions,and one may anticipate that this advantage would be more prominent when dealing with multiple distributed ellipsoids.Then,for all the 6independent eigenstrain components in a general half space inclusion problem,method of images is used to study the contribution of each component to the elastic field.Furthermore,the numerical implementation of Eshelby’s equivalent inclusion method is used to solve the problem of heterogeneous inclusions(inhomogeneities)in a half space.The analytical models of half space problems with inhomogeneities under Hertzian-type contact load and uniform remote loading are considered respectively,where the corresponding disturbance of the stress fields caused by the inhomogeneities are discussed.For a selected group of both Hertzian and remote loads,the variation of the disturbance of the stress field due to the size,depth location and elastic modulus of the inhomogeneity are examined.Finally,the research of ellipsoidal inclusions and inhomogeneities in a half space is further applied in the contact fatigue prediction.Zaretsky’s fatigue life model is introduced to quantitatively predict the influence of material impurities on the fatigue life under Hertzian type contact load.The influences of the elastic modulus,size and location of the ellipsoidal inhomogeneity on the fatigue life are discussed.
Keywords/Search Tags:Half space, Inclusion, Method of images, Contact fatigue, Life model
PDF Full Text Request
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