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On Hertzian contact and fracture at finite friction
KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).ORCID iD: 0000-0002-0596-228X
2006 (English)Licentiate thesis, comprehensive summary (Other scientific)
Place, publisher, year, edition, pages
Stockholm: KTH , 2006. , 9 p.
Series
Trita-HFL. Report / Royal Institute of Technology, Solid Mechanics, ISSN 1654-1472 ; 0402
Keyword [en]
contacts mechanics, elastic material, friction, nanoindentation, fracture
National Category
Other Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-3856OAI: oai:DiVA.org:kth-3856DiVA: diva2:9725
Presentation
2006-02-17, Q2, KTH, Osquldas väg 10, 2 tr, Stockholm, 10:15
Opponent
Supervisors
Note

QC 20101117

Available from: 2006-02-14 Created: 2006-02-14 Last updated: 2013-01-15Bibliographically approved
List of papers
1. Hertz contact at finite friction and arbitrary profiles
Open this publication in new window or tab >>Hertz contact at finite friction and arbitrary profiles
2005 (English)Article in journal (Refereed) Published
Abstract [en]

Axisymmetric contact at finite Coulomb friction and arbitrary profiles is examined analytically and numerically for dissimilar linear elastic solids. Invariance and generality are aimed at and an incremental procedure is developed resulting in a reduced benchmark problem corresponding to a rigid flat indentation of an elastic half-space. The reduced problem, being independent of loading and contact region, was solved by a finite element method based on a stationary contact contour and characterized by high accuracy. Subsequently, a tailored cumulative superposition procedure was developed to resolve the original problem to determine global and local field values. Save for the influence of the coefficients of friction and contraction ratio, it is shown that at partial slip the evolving relative stick-slip contour is independent of any convex and smooth contact profile at monotonic loading. For flat and conical profiles with rounded edges and apices, results are illustrated for relations between force, depth and contact contours together with surface stress distributions. The solution for dissimilar solids in a full space is transformed to a half-space problem and solved for a combination of material parameters in order to first determine interface traction distributions. Subsequently, full field values for the two solids were computed individually. In order to predict initiation of fracture and plastic flow, results are reported for the location and magnitude of maximum tensile stress and effective stress, respectively, for a range of geometrical and material parameters. In two illustrations, predicted results are compared with experimental findings related to initiation of brittle fracture and load-depth relations at nanoindentation.

Keyword
Contact mechanics, Elastic material, Fracture, Friction, Nanoindentation
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-5374 (URN)10.1016/j.jmps.2004.11.009 (DOI)000229272400009 ()2-s2.0-16344384224 (Scopus ID)
Note
QC 20100729Available from: 2006-02-14 Created: 2006-02-14 Last updated: 2010-11-17Bibliographically approved
2. Hertzian fracture at unloading
Open this publication in new window or tab >>Hertzian fracture at unloading
2006 (English)In: Journal of the mechanics and physics of solids, ISSN 0022-5096, Vol. 54, no 11, 2453-2473 p.Article in journal (Refereed) Published
Abstract [en]

Hertzian fracture through indentation of flat float glass specimens by steel balls has been examined experimentally. Initiation of cone cracks has been observed and failure loads together with contact and fracture radii determined at monotonically increasing load but also during unloading phases. Contact of dissimilar elastic solids under decreasing load may cause crack inception triggered by finite interface friction and accordingly the coefficient of friction was determined by two different methods. In order to make relevant predictions of experimental findings, a robust computational procedure has been developed to determine global and local field values in particular at unloading at finite friction. It was found that at continued loading it is possible to specify in advance how the contact domain divides into invariant regions of stick and slip. The maximum tensile stress was found to occur at the free surface just outside the contact contour, the relative distance depending on the different elastic compliance properties and the coefficient of friction. In contrast, at unloading invariance properties are lost and stick/slip regions proved to be severely history dependant and in particular with an opposed frictional shear stress at the contact boundary region. This causes an increase of the maximum tensile stress at the contour under progressive unloading. Predictions of loads to cause crack initiation during full cycles were made based on a critical stress fracture criterion and proved to be favourable as compared to the experimental results.

Keyword
Contact mechanics; Elastic material; Fracture; Friction; Unloading; Contact contour; Contact mechanics; Elastic materials; Stress fracture; Computational methods; Friction; Glass; Indentation; Interfaces (materials); Tensile stress; Fracture mechanics
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-7645 (URN)10.1016/j.jmps.2006.04.014 (DOI)000241961400009 ()2-s2.0-33749666497 (Scopus ID)
Note
QC 20100729Available from: 2007-11-14 Created: 2007-11-14 Last updated: 2010-11-17Bibliographically approved

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Jelagin, Denis

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