Hertzian fracture at unloading

International Journal of Solids and Structures

2008

The influence of indenter elasticity on Hertzian fracture initiation at frictional dissimilar elastic contact has been examined experimentally and numerically. In flat float glass specimens initiation of cone cracks has been observed and fracture loads measured with steel and tungsten carbide indenters at monotonically increasing loading and during a load cycle. The observed effect of indenter elasticity on fracture loads was found to be qualitatively different from the one predicted by the Hertz contact theory. This discrepancy may be explained by the presence of interfacial friction. The friction coefficient between the indenters and the specimen was measured and a contact cycle at finite Coulomb friction has been analyzed numerically. The influence of the indenter elasticity and the friction coefficient on the surface maximum tensile stress has been investigated and the results concerning the influence of these parameters on the fracture loads as given based on a critical stress fracture criterion. The obtained computational results were found to be in better agreement with experimental findings as compared to the predictions based on the frictionless contact theory. A remaining quantitative discrepancy was attributed to the well-known fact that a Hertzian macro-crack initiates from pre-existing defects on the specimen's surface. In order to account for the influence of the random distribution of these defects a Weibull statistics was introduced. The predicted critical loads corresponding to the 50% failure probability were found to be in close agreement with experimentally observed ones.

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Section: Formulation Of the Problem And Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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On indentation and initiation of fracture in glass

International Journal of Solids and Structures

2008

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“…The elasticity parameters for the contact materials are given in Table 1, along with material parameters for the equivalent rigid-elastic contact pair. The interfacial friction coefficient, µ, is set to 0.1 as measured by Elaguine et al [2006]. Numerical studies are performed for the case of flat and rounded contact profiles as shown in Figure 1.…”

Section: Resultsmentioning

confidence: 99%

“…In the present study an ABAQUS-based finite element method is used to analyze frictional contact between two dissimilar elastic bodies, as depicted in Figure 1, drawing upon the experience gained during previous and similar analyses [Elaguine et al 2006;Jelagin and Larsson 2008a;2008b]. In Figure 2 the finite element mesh is shown for the case of a spherical indenter with axisymmetry taken into account and with eight-noded isoparametric quadrilateral elements used.…”

Section: Formulation Of the Problemmentioning

confidence: 99%

On indenter boundary effects at elastic contact

J. Mech. Mater. Struct.

2012

Axisymmetric contact problems at finite Coulomb friction and rounded profiles are examined for linear elastic solids. In previous analytical/numerical approaches to this problem often incremental procedures have been developed resulting in a reduced incremental problem corresponding to a rigid flat indentation of an elastic half-space. The reduced problem, being independent of loading and contact region, can be solved by a finite element method based on a stationary contact contour and characterized by high accuracy. Subsequently, with cumulative superposition procedures it is then possible to resolve the original problem in order to determine global and local field values. Such a procedure, when applied to for example to flat and conical profiles with rounded edges and apices, is exact save for the influence from boundaries close to the contact region. This influence could be exemplified by the indenter boundaries of a flat deformable profile with rounded edges indenting a linear elastic half-space. In the present analysis such effects are investigated qualitatively and quantitatively. In doing so, the results derived using previously discussed analytical/numerical approaches are compared with corresponding ones from full-field finite element calculations. Both local as well as global quantities are included in the comparison in order to arrive at a complete understanding of the boundary effects at elastic contact.

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Nonlocal Frictional Effects at Indentation of Elastic Materials

2013

Tribol Lett