Instrumented pyramidal and spherical indentation of polycrystalline graphite

2004 ◽  
Vol 19 (1) ◽  
pp. 228-236 ◽  
Author(s):  
M. Sakai ◽  
Y. Nakano
Keyword(s):  
Surface Deformation ◽  
Spherical Indentation ◽  
Polycrystalline Graphite ◽  
Geometry Dependence ◽  
Indentation Tests ◽  
The Mean ◽  
Loading Parameter ◽  
Material Length ◽  
Tip Radius ◽  
True Hardness

The elastoplastic surface deformation of a polycrystalline graphite was studied by examining the indenter’s geometry dependence of load P versus penetration depth h relation (P–h relation) in instrumented pyramidal/spherical indentation tests. The tetrahedral pyramid indenters included inclined face angles β of 10.0°, 22.0° (Vickers pyramid), and 40.0°. The tip radius of spherical indenters used were 32 μm, 200 μm, 794 μm, 1.59 mm, and 6.35 mm. The true hardness H as a measure for plasticity was singled out of the elastoplastic loading parameter k1 in the quadratic expression of P = k1h2 and then quantitatively related to the yield stress Y that was determined from the mean contact pressure for spherical indentation at the onset of plastic yielding. The size effect of Y, decreasing with the increase in the tip radius of spherical indenter, is discussed using the model of geometrically necessary dislocations in terms of the material length scales for a plastic field with strain gradient.

scholarly journals Deformation And Fracture Analysis Of Coating-Substrate Systems

2015 ◽  
Vol 60 (3) ◽  
pp. 2307-2317 ◽  
Author(s):  
M. Kot
Keyword(s):  
Complex Analysis ◽  
Ceramic Coatings ◽  
Fracture Analysis ◽  
Spherical Indentation ◽  
Test Results ◽  
Deformation And Fracture ◽  
Indentation Tests ◽  
Tem Microscopy ◽  
Formation Of Cracks ◽  
Tip Radius

Abstract The paper presents the deformation and fracture analysis of coating-substrate systems during spherical indentation. CrN and TiN ceramic coatings with a thickness of 1-5 μm were tested using 10 to 200 μm tip radius spherical indenters. The typical results of indentation tests i.e. force-penetration depth curves were transformed into stress-strain curves using an algorithm developed by the author. The test results are compared with the results of numerical analysis conducted using FEM modelling. Such a complex analysis allows users to determine the level of tensile stress leading to the formation of cracks observed using SEM and TEM microscopy, and to define the failure maps for the coating substrate-systems.

An experimental device for depth-sensing indentation tests in millimeter-scale

1998 ◽  
Vol 13 (6) ◽  
pp. 1650-1655 ◽  
Author(s):  
N. Huber ◽  
Ch. Tsakmakis
Keyword(s):  
Aluminum Alloy ◽  
Data Use ◽  
Spherical Indentation ◽  
Depth Sensing ◽  
One Dimensional ◽  
Young’S Moduli ◽  
Accuracy Of Measurements ◽  
Indentation Tests ◽  
Constitutive Properties ◽  
Tip Radius

A device for spherical indentation using a tip radius of 2 mm and loads up to 10 kN is presented. This facility can be applied, for example, to verify methods for characterizing the behavior of materials exhibiting homogeneous and isotropic constitutive properties. The indentation device can be driven both load- and depth-controlled. The accuracy of measurements is about 1 N for load and 0.2 μm for depth at a total depth of 200 μm. Two materials, an austenitic steel and an aluminum alloy, have been tested and their Young's moduli have been determined. For determining Young's modulus from spherical indentation data, use is made of a so-called Lt method, which had been developed in Ref. 1. Results obtained in this way are compared with corresponding values measured by one-dimensional homogeneous tensile experiments.

scholarly journals Dynamics of the Ice-Crushing Process

1988 ◽  
Vol 34 (118) ◽  
pp. 318-326 ◽  
Author(s):  
Ian J. Jordaan ◽  
Garry W. Timco
Keyword(s):  
Ice Sheet ◽  
Load Cycle ◽  
Stored Energy ◽  
Indentation Process ◽  
Ice Particles ◽  
Mode Of Failure ◽  
Indentation Tests ◽  
Energy Exchanges ◽  
The Mean ◽  
Crushed Ice

Abstract During fast indentation tests on ice sheets at constant rates, crushing is commonly observed at appropriate combinations of speed and aspect ratio. An analysis is made of this mode of failure, using as a basis a recently conducted test on an ice sheet under controlled conditions. The variation of load with time is given special attention, and cyclic variation of load is associated with periodic crushing (pulverization) events, followed by clearing of the crushed ice particles. An analysis of the clearing process is summarized in the paper, treating the crushed ice as a viscous material. A detailed analysis of the energy exchanges during the indentation process is given. Elastic variations of stored energy in the indenter and in the ice sheet are calculated; these are relatively minor. The dissipation of energy during a typical load cycle (3 mm movement during 0.05 s) is about 8 J. The energy required to create surfaces of the crushed ice particles is small (0.006 J), as is the work of crushing based on mechanical testing (0.09 J). It is concluded that the process of viscous extrusion of crushed ice is the main seat of energy dissipation, basically as a frictional process. A relationship for the mean thickness of the crushed ice layer is developed, based on energy-balance considerations.

Identification of Hardening Parameters of Metals From Spherical Indentation Tests

2001 ◽  
Vol 123 (3) ◽  
pp. 245-250 ◽  
Author(s):  
S. Kucharski ◽  
Z. Mro´z
Keyword(s):  
Indentation Test ◽  
Strain Curve ◽  
Load Level ◽  
Spherical Indentation ◽  
Indentation Tests ◽  
Geometric Sequence ◽  
Loading And Unloading ◽  
Plastic Hardening ◽  
Hardening Curve ◽  
Two Parameters

The identification method of hardening parameters specifying stress-strain curve is proposed by applying spherical indentation test and measuring the penetration depth during loading and unloading. The loading program is composed of a geometric sequence of loading and partial unloading steps from which the variation of permanent penetration with load level is determined. This data is used for specification of two parameters k and m occurring in the plastic hardening curve εp=σ/k1/m, where εp denotes the plastic strain.

Controlled Elasticity in Nano-Structured Metallic Glass by Ion Implantation Method

2007 ◽  
Vol 561-565 ◽  
pp. 1315-1318
Author(s):  
Shinji Muraishi ◽  
Hirono Naito ◽  
Jhi Shi ◽  
Yoshio Nakamura ◽  
Tatsuhiko Aizawa
Keyword(s):  
Metallic Glass ◽  
Glassy Phase ◽  
Glassy Matrix ◽  
Nano Structure ◽  
Glass Forming ◽  
Nitride Formation ◽  
Indentation Tests ◽  
The Mean ◽  
Implantation Method ◽  
Critical N Concentration

Different reactivity of ions has been implanted into Zr-Cu metallic glass to obtain nano-structured surface with controlled elasticity. The penetration of glass forming element of Ni+ into crystalline Zr-Cu stabilizes glassy phase to induce crystalline-amorphous (c-a) transition during implantation process. In the meanwhile, penetration of N+ into glassy matrix induces precipitation of (Zr, Cu)N at the mean penetration depth of N. Critical N concentration for nitride formation is estimated to be (Zr,Cu)-20at%N, which also suggests existing of N solid solution of glassy phase. Inert element of Ar+ yields dispersion of nano-voids among glassy matrix. Nano-indentation tests reveal that Young’s modulus of ion implanted glassy film dramatically changes with respect to the induced nano-structure, to decrease 0.4 times for Ar+, to increase 1.3 times for N+ as comparison with that for as-deposited state.

A study on determination of tensile properties of metals at elevated temperatures from spherical indentation tests

2019 ◽  
Vol 54 (5-6) ◽  
pp. 331-347
Author(s):  
Tairui Zhang ◽  
Shang Wang ◽  
Weiqiang Wang
Keyword(s):  
Tensile Properties ◽  
Analytical Model ◽  
Elevated Temperatures ◽  
Regression Function ◽  
Maximum Error ◽  
Analytical Models ◽  
Uniaxial Tensile ◽  
Spherical Indentation ◽  
Material Parameters ◽  
Indentation Tests

In this study, spherical indentation tests were used to determine the uniaxial tensile properties of metals at elevated temperatures (200 °C, 400 °C, and 600 °C). Taking the difference between spherical indentation tests at room and elevated temperatures into consideration, the incremental and analytical models were used to determine material parameters ( σ0, Ep, and n) and thermal softening parameters ( Eeff and m) in the Johnson–Cook constitutive equation, respectively. A discussion on the stability of the analytical model proved that despite in relative complicated forms and with three intercoupling material parameters, the analytical model is still effective for tensile property calculation. From the investigation on the relationship between pm and pi, it was found that correlating coefficient ξ is actually a function of both indentation depth and material parameters, and thus, a regression function was proposed for a more accurate description of ξ. Effectiveness of the spherical indentation tests was verified through experiments on three steels, SA508, 15CrMoR, S30408, and one titanium alloy, TC21, which proved that the spherical indentation tests can provide both proof and tensile strength calculations with a maximum error around 15% at room temperature and within 20% at elevated temperatures, and thus satisfy the demands for engineering applications.

scholarly journals Numerical verification for instrumented spherical indentation techniques in determining the plastic properties of materials

2009 ◽  
Vol 24 (12) ◽  
pp. 3653-3663 ◽  
Author(s):  
Taihua Zhang ◽  
Peng Jiang ◽  
Yihui Feng ◽  
Rong Yang
Keyword(s):  
Numerical Experiments ◽  
Spherical Indentation ◽  
Numerical Verification ◽  
Instrumented Indentation ◽  
Plastic Properties ◽  
Wide Range ◽  
Validity Range ◽  
Indentation Tests ◽  
Properties Of Materials ◽  
Indentation Methods

Instrumented indentation tests have been widely adopted for elastic modulus determination. Recently, a number of indentation-based methods for plastic properties characterization have been proposed, and rigorous verification is absolutely necessary for their wide application. In view of the advantages of spherical indentation compared with conical indentation in determining plastic properties, this study mainly concerns verification of spherical indentation methods. Five convenient and simple models were selected for this purpose, and numerical experiments for a wide range of materials are carried out to identify their accuracy and sensitivity characteristics. The verification results show that four of these five methods can give relatively accurate and stable results within a certain material domain, which is defined as their validity range and has been summarized for each method.

Local Mechanical Characterization of Metal Foams by Nanoindentation

2015 ◽  
Vol 662 ◽  
pp. 59-62 ◽  
Author(s):  
Jiří Němeček ◽  
Vlastimil Kralik
Keyword(s):  
Cell Walls ◽  
Plastic Material ◽  
Spherical Indentation ◽  
Isotropic Hardening ◽  
Plastic Properties ◽  
Macro Scale ◽  
Static Indentation ◽  
Indentation Tests ◽  
Constitutive Parameters

This paper deals with microstructure and micromechanical properties of two commercially available aluminium foams (Alporas and Aluhab). Since none of the materials is available in a bulk and standard mechanical testing at macro-scale is not possible the materials need to be tested at micro-scale. To obtain both elastic and plastic properties quasi-static indentation was performed with two different indenter geometries (Berkovich and spherical tips). The material phase properties were analyzed with statistical grid indentation method and micromechanical homogenization was applied to obtain effective elastic wall properties. In addition, effective inelastic properties of cell walls were identified with spherical indentation. Constitutive parameters related to elasto-plastic material with linear isotropic hardening (the yield point and tangent modulus) were directly deduced from the load–depth curves of spherical indentation tests using formulations of the representative strain and stress introduced by Tabor.

Energy principle of indentation contact: The application to sapphire

1993 ◽  
Vol 8 (5) ◽  
pp. 1068-1078 ◽  
Author(s):  
Roman Nowak ◽  
Mototsugu Sakai
Keyword(s):  
Indentation Test ◽  
Shear Stresses ◽  
Anisotropic Behavior ◽  
Energy Principle ◽  
Triangular Pyramid ◽  
Indentation Tests ◽  
Crystallographic Planes ◽  
Continuous Indentation ◽  
True Hardness ◽  
Crystallographic Orientations

The recently developed energy principle of indentation mechanics was applied to the continuous indentation test performed on pure sapphire. Three crystallographic planes, M = (10$\overline 1$0), A = (1$\overline 1$10), and C = (0001), have been indented by a symmetrical triangular pyramid (Berkovich). The distinct anisotropic behavior of the indented crystal has been observed for the maximum indentation loads of 1.961 N, 0.686 N, and 0.392 N. The indentation hysteresis loop energy and the related “true hardness parameter” have been determined for various crystallographic orientations, as well as for two different orientations of the indenter. The observed effects have been discussed in terms of the energy principle of indentation with crystallographic considerations. The effective resolved shear stresses for the slip and twinning systems were calculated and applied to the anisotropic indentation behavior. It was concluded that the energy principle is highly recommended for analyzing the data of continuous indentation tests.

scholarly journals A new method for hardness determination from depth sensing indentation tests

1996 ◽  
Vol 11 (12) ◽  
pp. 2964-2967 ◽  
Author(s):  
J. Gubicza ◽  
A. Juhász ◽  
J. Lendvai
Keyword(s):  
Contact Pressure ◽  
Elastic Material ◽  
Depth Sensing ◽  
Hardness Number ◽  
Indentation Tests ◽  
Semiempirical Formula ◽  
Loading And Unloading ◽  
The Mean ◽  
Limiting Case

A new semiempirical formula is developed for the hardness determination of the materials from depth sensing indentation tests. The indentation works measured both during loading and unloading periods are used in the evaluation. The values of the Meyer hardness calculated in this way agree well with those obtained by conventional optical observation, where this latter is possible. While the new hardness formula characterizes well the behavior of the conventional hardness number even for the ideally elastic material, the mean contact pressure generally used in hardness determination differs significantly from the conventional hardness number when the ideally elastic limiting case is being approached.

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