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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01 Jan 2000
TL;DR: Instrumented indentation testing (IIT) as mentioned in this paper is a relatively new form of mechanical testing that significantly expands on the capabilities of traditional hardness testing and has been widely used in the literature.
Abstract: INSTRUMENTED INDENTATION TESTING (IIT), also known as depth-sensing indentation, continuous-recording indentation, ultra-low-load indentation, and nanoindentation, is a relatively new form of mechanical testing that significantly expands on the capabilities of traditional hardness testing. Developed largely over the past two decades, IIT employs high-resolution instrumentation to continuously control and monitor the loads and displacements of an indenter as it is driven into and withdrawn from a material (Ref 1–13). Depending on the details of the specific testing system, loads as small as 1 nN can be applied, and displacements of 0.1 nm (1 A) can be measured. Mechanical properties are derived from the indentation load-displacement data obtained in simple tests. The advantages of IIT are numerous, as indentation load-displacement data contain a wealth of information, and techniques have been developed for characterizing a variety of mechanical properties. The technique most frequently employed measures the hardness, but it also gives the elastic modulus (Young’s modulus) from the same data (Ref 8, 11). Although not as well-developed, methods have also been devised for evaluating the yield stress and strain-hardening characteristic of metals (Ref 14–16); parameters characteristic of damping and internal friction in polymers, such as the storage and loss modulus (Ref 17, 18); and the activation energy and stress exponent for creep (Ref 19–25). IIT has even been used to estimate the fracture toughness of brittle materials using optical measurement of the lengths of cracks that have formed at the corners of hardness impressions made with special sharp indenters (Ref 13, 26, 27). In fact, almost any material property that can be measured in a uniaxial tension or compression test can conceivably be measured, or at least estimated, using IIT. An equally important advantage of IIT results because load-displacement data can be used to determine mechanical properties without having to image the hardness impressions. This facilitates property measurement at very small scales. Mechanical properties are routinely measured from submicron indentations, and with careful technique, properties have even been determined from indentations only a few nanometers deep. Because of this, IIT has become a primary tool for examining thin films, coatings, and materials with surfaces modified by techniques such as ion implantation and laser heat treatment. Many IIT testing systems are equipped with automated specimen manipulation stages. In these systems, the spatial distribution of the near-surface mechanical properties can be mapped on a point-to-point basis along the surface in a fully automated way. Lateral spatial resolutions of about a micron have been achieved. An example of small indentations located at specific points in an electronic microcircuit is shown in Fig. 1. The purpose of this article is to provide a practical reference guide for instrumented indentation testing. Emphasis is placed on the better-developed measurement techniques and the procedures and calibrations required to obtain accurate and meaningful measurements.
229 citations
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TL;DR: In this paper, the authors investigated the effect of major material properties on the indentation load-deflection curve via finite element (FE) analyses based on incremental plasticity theory.
Abstract: In this work, some inaccuracies and limitations of prior indentation theories, which are based on experimental observations and the deformation theory of plasticity, are investigated. Effects of major material properties on the indentation load-deflection curve are examined via finite element (FE) analyses based on incremental plasticity theory. It is confirmed that subindenter deformation and stress–strain distribution from deformation plasticity theory are quite dissimilar to those obtained from incremental plasticity theory. We suggest an optimal data acquisition location, where the strain gradient is the least and the effect of friction is negligible. A new numerical approach to indentation techniques is then proposed by examining the FE solutions at the optimal point. Numerical regressions of obtained data exhibit that the strain-hardening exponent and yield strain are the two key parameters which govern the subindenter deformation characteristics. The new indentation theory successfully provides a stress–strain curve and material properties with an average error of less than 3%.
227 citations
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TL;DR: In this article, the effect of surface friction characteristics of aramid fabrics with respect to their static deformation behavior and their ballistic capture performance was investigated, and a simulation of the ballistic deformation process in fabrics was devised on the basis of this first-order model of the quasi static indentation process.
226 citations
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TL;DR: In this paper, it was shown that the indentation hardness of metals is directly related to the uniaxial yield stress as augmented by the deformation and work hardening produced by the process itself.
Abstract: This introductory paper is a brief revised account of basic studies carried out between 1940 and 1946 on the meaning of indentation hardness. Using very simple concepts, it shows that the indentation hardness of metals is directly related to the uniaxial yield stress as augmented by the deformation and work hardening produced by the indentation process itself. The work originally carried out on metals is applicable to many other solids, particularly if they have a crystalline structure. The paper concludes with a short review of current studies in the field of microhardness and nanohardness.
225 citations
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TL;DR: In this paper, the problem of indentation of a hard sphere into inelastic solids, Brinell indentation, is examined theoretically and numerically by aid of classical plastic flow theory.
Abstract: Indentation of a hard sphere into inelastic solids, Brinell indentation, is examined theoretically and numerically by aid of classical plastic flow theory. With the main interest focused on fully plastic behaviour at indentation the mechanical analysis is carried out for power-law hardening rigid-plastic materials where self-similarity features play a dominant role. It is explained in detail how the problem of a moving contact boundary may be reduced to a stationary one by an appropriate transformation of field variables. Within this setting classical empirical findings by Meyer (1908) and O'Neill (1944) are established on a rigorous theoretical ground. In particular, it is shown to advantage also for nonlinear materials how intermediate solutions for a flat die may by cumulative superposition generate solutions for a class of curved indenters. In the case of perfect plasticity it turns out in the present context that indentation hardness is independent of die profiles. For hardening solids when the material behaviour is history dependent, reduction to a stationary geometry is achieved also by expressing the accumulated strain by cumulative superposition. The intermediate flat die problem is then solved for a variety of hardening exponents by a finite element procedure designed to account for material incompressibility. With finite element computations as a basis desired solutions are obtained by straightforward numerical superposition procedures. Detailed results are then given for bulk quantities such as the mean contact pressure as well as relevant field variables. The influence of hardening characteristics on sinking-in and piling-up of indented surfaces and contact pressure distributions are discussed in the light of earlier findings based on deformation theory of plasticity and available discriminating experiments. Correlation is particularly sought with the celebrated universal hardness parameters proposed by Tabor (1951) and the existence of representative strain measures. Attention is also given to the elastic-plastic transition region of Brinell indentation in search for loading levels sufficiently high that the results tend to an asymptotic fully plastic state. A standard finite element technique employing contact elements for a moving boundary is used to analyse with tolerable accuracy the influence of elasticity and more elaborate hardening behaviour. Some relevant features are shown for a sequence of solutions from elastic Hertzian to fully plastic behaviour.
222 citations