Topic
Indentation
About: Indentation is a research topic. Over the lifetime, 13002 publications have been published within this topic receiving 340476 citations.
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TL;DR: In this article, the Griffith equation and indentation fracture mechanics were used to characterize the R-curve behavior of two in-situ reinforced silicon nitrides, and the effects of these properties on design were discussed.
Abstract: R-curves for two in-situ reinforced silicon nitrides A and B of nominally the same composition are characterized using the Griffith equation and indentation fracture mechanics. These R-curves are calibrated against fine-grained silicon nitrides which have a known chevron-notch (long-crack) toughness and with a nearly flat R-curve behavior. Silicon nitride A, with its coarser microstructure and higher chevron-notch toughness, shows lower resitance to crack growth than silicon nitride B if the crack size is less than ∼200 μm. These results are consistent with the indentation–Strength measurements which show a crossover of strength between the two materials at an indentation load between 49 and 98 N, and below the crossover A has a lower strength. The toughening behavior is explained using an elastic-bridging model for the short crack, and a pullout model for the long crack. The effects of R-curve properties on design are discussed.
105 citations
TL;DR: In this paper, the effect of indenter elasticity on the adhesion energy and elastic modulus ratio of the compliant layers was investigated for both spherical and flat punch probes. But, the authors focused on the contact of homogeneous, isotropic solids.
Abstract: The Johnson, Kendall and Roberts (JKR) adhesion theory is frequently applied to study the adhesion mechanics of thin compliant layers coated on to glass substrate in an atomic force microscope (AFM). These compliant layers are subjected to micro indentation in the AFM using a flat or spherical indenter. But, JKR theory is based on the contact of homogeneous, isotropic solids. The finite element analysis used by Sridhar et al (1997) (J. Phys. D: Appl. Phys. 30 1710-19) to study the adhesion mechanics of the three-layered crossed-cylinder arrangement of the surface force apparatus (SFA) has been extended to this AFM geometry. The effect of indenter elasticity is included for both spherical and flat punch probes. Computations of contact size and contact compliance each as a function of load are presented for a range of values of adhesion energy and elastic modulus ratio of layer and substrate.
105 citations
TL;DR: In this paper, the authors proposed an improved technique to determine the plastic properties of a bulk material from the load-displacement curve from only one conical indentation test.
105 citations
TL;DR: In this article, the effect of core thickness on the deformation mechanism of an aluminium foam core/thermoplastic composite facing sandwich structure under 4-point bending was investigated.
105 citations
TL;DR: In this article, the variation of apparent hardness observed in previously reported Vickers indentation tests of metals is reexamined and it is shown that the effect is consistent with varying size of a previously postulated "plastic hinge" at the perimeter of the indent.
Abstract: The variation of apparent hardness observed in previously reported Vickers indentation tests of metals is reexamined. Common deseriptions of the effect are shown to be inaccurate: the variation of apparent hardness is monotonic but not simple. The effect is consistent with varying size of a previously postulated “plastic hinge” at the perimeter of the indent. This complexity confers uncertainty on the estimation of characteristic macrohardness from small scale tests. Association of the indentation size effect with friction and with strain hardening is confirmed.
104 citations