Indentation

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

Indentation load-displacement curve, plastic deformation, and energy

Abstract: Various methods to access indentation data are considered on the basis of the load P–displacement h curve, its derivative, or its integral. This paper discusses and extends the various analytical models to estimate the indentation P–h curve, the slope, and the dissipated energy to aid the development of a concise methodology to analyze indentation data. Special consideration is given to the effect of pile-up and sink-in. Relationships for sharp and spherical indenters are presented and in addition for sharp indenters with a rounded tip. An overview over analytic expressions for the P–h curve is given and compared to finite element simulations and experimental data. An expression derived for the representative strain at the onset of yield under sharp and spherical indenters compares well with literature results. The effect of a rounded tip on the yielding under a sharp indenter is discussed. The ratio of loading to unloading slope and the ratio of the plastically dissipated energy to the total energy is related to hardness and elastic modulus. In combination these ratios can be used to determine the strain-hardening coefficient.

Indentation hardness evaluation of cathodic arc deposited thin hard coatings

Abstract: One trend in the development of wear-resistant vapour deposited coatings is to make them increasingly harder and thinner, by improvement and optimisation of the deposition processes. A complex interdependence exists between the individual properties of a coating and a substrate on the one hand, and those of the ‘composite’ coated system on the other. For example, system stiffness and hardness may vary with indentation depth according to different laws. There is a great need for quantitative modelling methods so that the design of coatings and multi-layered systems can be improved, and the choice of materials optimised. In the present study, various hard coatings produced by filtered cathodic arc deposition were characterised by micro-indentation and macro-indentation methods, and scanning electron microscopy. SEM was used to elucidate the fracture behaviour of these coatings, which exerts an important influence on their hardness performance. Hardness testing results were analysed using a newly proposed modification of the work-of-indentation model, an approach that was recently developed and applied to a range of coated systems. The new development of this model allows more accurate fitting of the empirical data, and yields an estimate for the ultimate coating hardness, and values of dimensionless materials parameters β 0 and X . These parameters describe the normalised depth and the degree of abruptness at which the hardness transition from coating to substrate occurs, and are related in a complex way to the ductility and toughness of the thin film and the interface, as well as the substrate's yield strength and hardening behaviour. In this study we use the model to interpret micro- and macro-indentation data, and to discuss the results of extrapolating the depth–hardness curve to the important region where the indentation depth lies is between 5 and 10% of the coating thickness, and composite hardness approaches the ultimate film hardness.

Interfacial mechanical behavior of 3D printed ABS

Abstract: We describe an experimental approach for characterizing the local mechanical behavior of acrylonitrile butadiene styrene (ABS) structures processed through fused deposition modeling. ABS test specimens processed in various build orientations were subject to multiscale mechanical tests as well as local morphology and chemical analyses. Instrumented indentation, local dynamic mechanical analysis, and atomic force microscopy tests were used to explore the mechanical behavior and morphology of build surfaces and weld interfaces. An interfacial stiffening effect was found for the majority of the specimens tested, with up to a 40% increase in the indentation elastic modulus measured with respect to the build surfaces. Raman spectroscopy mapping of the interfacial areas revealed ∼30% less butadiene/styrene and butadiene/acrylonitrile ratios with respect to analysis of the build surfaces. The results provide insight into the multiscale behavior of additive manufactured structures and offer the potential to guide processing–structure–property understanding of these materials. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43671.