Indentation

About: Indentation is a research topic. Over the lifetime, 13002 publications have been published within this topic receiving 340476 citations.

Scaling relationships for indentation measurements

Abstract: Using dimensional analysis and finite-element calculations, several relationships that relate features of indentation loading and unloading curves to the hardness, the elastic modulus and the work of indentation are extended to conical indentation in elastic-plastic solids with various angles. These relationships provide new insights into indentation measurements. They may also be useful to the interpretation of results obtained from instrumented indentation experiments.

Nanoindentation of wood cell walls: Continuous stiffness and hardness measurements

Abstract: The objective of this study was to measure the mechanical properties of individual, native wood fibers using the continuous nanoindentation measurement technique. The indentation depth profile exhibited a small length-scale effect, which was confirmed using the size-effect index derived from the indentation loading curve. The hardness (Hu) or stiffness (Eu) values determined from indentation unloading were also examined for 10 different annual rings of a loblolly pine, with microfibril angles (MFA) between 14� and 36� .A predictable pattern of Eu values was found as a function of MFA, and hence Eu can at least be considered a relative measure of the longitudinal stiffness properties of wood cell walls. For Hu values, a dependence on orientation was observed, and there is a preliminary indication that the dependence could be affected by cell-wall extractives. It is thus desirable, for cell-wall modification studies, to minimize any unintended variations by using samples that are from the same growth ring, so that any treatment-induced changes in the cellwall hardness can be identified. � 2006 Elsevier Ltd. All rights reserved.

Study of Elastic Modulus and Yield Strength of Polymer Thin Films Using Atomic Force Microscopy

Abstract: Nanometer-scale elastic moduli and yield strengths of polycarbonate (PC) and polystyrene (PS) thin films were measured with atomic force microscopy (AFM) indentation measurements. By analysis of the AFM indentation force curves with the method by Oliver and Pharr, Young's moduli of PC and PS thin films could be obtained as 2.2 +/- 0.1 and 2.6 +/- 0.1 GPa, respectively, which agree well with the literature values. By fitting Johnson's conical spherical cavity model to the measured plastic zone sizes, we obtained yield strengths of 141.2 MPa for PC thin films and 178.7 MPa for PS thin films, which are similar to2 times the values expected from the literature. We propose that it is due to the AFM indentation being asymmetric, which was not accounted for in Johnson's model. A correction factor, epsilon, of similar to0.72 was introduced to rescale the plastic zone size, whereupon good agreement between theory and experiment was achieved.

Indentation deformation mechanism in glass: Densification versus shear flow

Abstract: Although the characteristic time constant for viscous relaxation of glass is so large at room temperature that viscous flow would be hardly detectable, a permanent deformation can be easily achieved at ambient temperature by applying a sharp contact loading—a Vickers indenter for instance—for few seconds only. We provide direct evidence for densification and volume conservative shear flow by means of atomic force microscopy topological analysis of the indentation profile and volume on as-quenched and densified specimens (pressure up to 25 GPa). We show that both possible mechanisms contribute to different extents depending on the glass composition. A major finding is that densification predominates in glasses with relatively low atomic packing density but that shear flow relays on once densification is achieved.