Numerical investigations of pyramid indentation on powder compacts
About: This article is published in Scripta Materialia.The article was published on 2001-06-08. It has received 3 citations till now. The article focuses on the topics: Indentation hardness & Powder metallurgy.
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TL;DR: In this article, a bibliographical review of the finite element modelling and simulation of indentation testing from the theoretical as well as practical points of view is given, with references to papers, conference proceedings and theses/dissertations that were published between 1990 and 2002.
Abstract: This paper gives a bibliographical review of the finite element modelling and simulation of indentation testing from the theoretical as well as practical points of view. The bibliography lists references to papers, conference proceedings and theses/dissertations that were published between 1990 and 2002. At the end of this paper, 509 references are listed dealing with subjects such as, fundamental relations and modelling in indentation testing, identification of mechanical properties for specific materials, fracture mechanics problems in indentation, scaling relationship for indentation, indenter geometry and indentation testing.
18 citations
TL;DR: In this article, the plane-strain, elasto-plastic contact problem is treated for a substrate that is perfectly plastic post yield, and so simulates compression molding of some metals at elevated temperatures.
15 citations
Dissertation•
01 Jan 2010
TL;DR: In this article, the effect of sample tilt on results of nanoindentation tests was investigated, and it was shown that for materials that sink-in and those that pile-up, the projected contact area of a tilted sample is higher than that estimated by the standard area function, which leads to overestimation of the hardness and elastic modulus.
Abstract: This dissertation consists of four submission-ready papers that address some of the key error sources that
affect the accuracy of interpretation of nanoindentation test results to obtain material properties for elastoplastic
materials. The first part of the work is a study of the effect of sample tilt on results of nanoindentation tests.
Geometrical relations are used to develop a correction to account for the effect of tilt angle on the contact area. 3D
FEA (Finite Element Analysis) shows that the assumptions made in deriving the geometric correction are valid, and
the results for contact area, hardness and modulus match the predictions of the analytical model. It is shown that for
both materials that sink-in and those that pile-up, the projected contact area for nanoindentation on tilted sample is
higher than that estimated by the standard area function, which leads to overestimation of the hardness and elastic
modulus. Experimental nanoindentation tests on tilted samples show lower sensitivity to sample tilt compared to
FEA results because the compliance of the indenter holder causes the indenter tip to displace in the direction of the
surface tilt, reducing the total penetration of the tip into the surface. For tips with very high compliance, this may
even lead to significant underestimation of the hardness and modulus.
The second part discusses the various factors that affect the accuracy of FEA of nanoindentation. With the
understanding that contact area error arising from discretization of the continuum is a key contributor to noise in the
hardness data, a self similar mesh is designed that results in a known amount of maximum error in contact area over
a range of depths of penetration of the indenter. Based on the fact that contact area increases in discrete jumps, it is
argued that the maximum force that a given area of contact can support, before the next element comes into contact,
is the best measure of the true hardness of the material that can be obtained with a given mesh. FEA simulations
carried out with meshes of different amounts of error in contact area show that as the discretization becomes coarser,
the estimate of the true hardness increases, due to the inability of the mesh to resolve the steep gradients in stress
and strain near the end point of contact. It is also shown that results obtained from different meshes with different
error percentages can be extrapolated to determine the exact value of hardness that will be obtained with
infinitesimally small elements. It is shown that other sources of error, such as the convergence tolerance of the
iterative solution process, are small in comparison to the discretization errors.
The third part is a study aimed at identifying the size of the volume underneath a nanoindentation that
influences the hardness and modulus measured. FEA simulations of the indentation of a hemispherical particle
embedded in a matrix reveal that the hardness of particle can be measured accurately by nanoindentation as long as
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the plastically…
6 citations
Additional excerpts
...2 as FEA and experimental studies (Basaran et al., 2004; Chen et al., 2006; Fleck et al., 1992; Kumar et al., 2001; Tasan et al., 2009; Xiang et al., 2006)....
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...2 as FEA and experimental studies (Basaran et al., 2004; Chen et al., 2006; Fleck et al., 1992; Kumar et al., 2001; Tasan et al., 2009; Xiang et al., 2006)....
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References
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TL;DR: In this article, the authors evaluated the tensile and compressive mechanical properties of various initial porosities, and determined the effect of deformation on the evolution of porosity, pore size and pore shape.
162 citations
IBM1
TL;DR: In this paper, the contact problem in a multilayer medium is analyzed based upon classical elasticity theory and the mixed boundary value problem is reformulated into a general approximation technique suitable for calculation on a digital computer.
148 citations
TL;DR: In this paper, the title problem is treated under the conditions of frictionless and completely adhesive contact, within the context of incremental elasto-plasticity, and the analysis employs a constant-strain-triangle, finite element code, together with a new grid expansion technique which aids computational efficiency.
127 citations
TL;DR: In this paper, a parametric analysis of Vickers and Berkovich indentations using the finite element method was performed and the pressure sensitivity of the materials was modeled according to the classic Drucker-Prager plastic potential.
107 citations
TL;DR: In this article, the effect of porosity upon indentation resistance is explored for a sticking conical indenter, and two material models are used: the Gurson model which is appropriate for lower porosities, where there are well separated voids that are roughly spherical in shape, and the particle yield model of Fleck et al.
97 citations