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.

Spherical indentation of ductile power law materials

2004 ◽  
Vol 19 (9) ◽  
pp. 2641-2649 ◽  
Author(s):  
Roberta Mulford ◽  
Robert J. Asaro ◽  
Robert J. Sebring
Keyword(s):  
Power Law ◽  
Contact Surface ◽  
Indentation Test ◽  
Strain Curve ◽  
Spherical Indentation ◽  
Actual Contact ◽  
Indentation Tests ◽  
Surface Profiles ◽  
Constitutive Parameters ◽  
Versus Strain

A procedure for extracting simple constitutive parameters from microindentationtests is described. The analysis used to interpret the indentation tests is based onthe analysis of the spherical indentation test developed by Hill et al. for power law materials. Indentation tests are supplemented by scanning interference microscopyof the residual indented surface profiles and a method is suggested for using the residual surface profiles to estimate the actual contact surface. This, in turn, allowsfor the construction of the entire stress versus strain curve.

Can indentation technique measure unique elastoplastic properties?

2009 ◽  
Vol 24 (3) ◽  
pp. 784-800 ◽  
Author(s):  
Ling Liu ◽  
Nagahisa Ogasawara ◽  
Norimasa Chiba ◽  
Xi Chen
Keyword(s):  
Critical Strain ◽  
Indentation Test ◽  
Strain Curve ◽  
Spherical Indentation ◽  
Plastic Behavior ◽  
Displacement Curve ◽  
Application Range ◽  
Indentation Technique ◽  
Elastoplastic Properties ◽  
Force Displacement

Indentation is widely used to extract material elastoplastic properties from measured force-displacement curves. Many previous studies argued or implied that such a measurement is unique and the whole material stress-strain curve can be measured. Here we show that first, for a given indenter geometry, the indentation test cannot effectively probe material plastic behavior beyond a critical strain, and thus the solution of the reverse analysis of the indentation force-displacement curve is nonunique beyond such a critical strain. Secondly, even within the critical strain, pairs of mystical materials can exist that have essentially identical indentation responses (with differences below the resolution of published indentation techniques) even when the indenter angle is varied over a large range. Thus, fundamental elastoplastic behaviors, such as the yield stress and work hardening properties (functions), cannot be uniquely determined from the force-displacement curves of indentation analyses (including both plural sharp indentation and deep spherical indentation). Explicit algorithms of deriving the mystical materials are established, and we qualitatively correlate the sharp and spherical indentation analyses through the use of critical strain. The theoretical study in this paper addresses important questions of the application range, limitations, and uniqueness of the indentation test, as well as providing useful guidelines to properly use the indentation technique to measure material constitutive properties.

Determining engineering stress–strain curve directly from the load–depth curve of spherical indentation test

2010 ◽  
Vol 25 (12) ◽  
pp. 2297-2307 ◽  
Author(s):  
Baoxing Xu ◽  
Xi Chen
Keyword(s):  
Indentation Test ◽  
Strain Curve ◽  
Spherical Indentation ◽  
Displacement Curve ◽  
Large Set ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Constraint Factors ◽  
Engineering Stress ◽  
Depth Curve

The engineering stress–strain curve is one of the most convenient characterizations of the constitutive behavior of materials that can be obtained directly from uniaxial experiments. We propose that the engineering stress–strain curve may also be directly converted from the load–depth curve of a deep spherical indentation test via new phenomenological formulations of the effective indentation strain and stress. From extensive forward analyses, explicit relationships are established between the indentation constraint factors and material elastoplastic parameters, and verified numerically by a large set of engineering materials as well as experimentally by parallel laboratory tests and data available in the literature. An iterative reverse analysis procedure is proposed such that the uniaxial engineering stress–strain curve of an unknown material (assuming that its elastic modulus is obtained in advance via a separate shallow spherical indentation test or other established methods) can be deduced phenomenologically and approximately from the load–displacement curve of a deep spherical indentation test.

Determination of the Elastic-Plastic Properties of 15Kh2MFA Steel with Austenitic Cladding

2013 ◽  
Vol 586 ◽  
pp. 43-46 ◽  
Author(s):  
Aleš Materna ◽  
Jiri Nohava ◽  
Petr Haušild ◽  
Vladislav Oliva
Keyword(s):  
Tensile Test ◽  
Indentation Test ◽  
Strain Curve ◽  
Indentation Load ◽  
Spherical Indentation ◽  
Compression Tests ◽  
Material Interface ◽  
Plastic Properties ◽  
Longitudinal Orientation ◽  
Sufficient Distance

The spherical indentation response of pressure vessel reactor steel with austenitic cladding is investigated both experimentally and numerically. The instrumented indentation test was performed for both materials at a sufficient distance from the bi-material interface, thus the results can be compared with the bulk data obtained from the standard tensile and compression tests. The stress – plastic strain curve for austenitic cladding estimated by a simplified inverse analysis of the indentation load – penetration curve is shifted to a harder response compared with that determined from the tensile test. One of the possible reasons, anisotropy of the cladding metal, was experimentally observed during the compression tests performed in the longitudinal orientation of the tensile test specimens and in the transverse orientation identical with the direction of the material indentation.

MATERIAL CHARACTERIZATION BASED ON INSTRUMENTED AND SIMULATED INDENTATION TESTS

2009 ◽  
Vol 01 (01) ◽  
pp. 61-84 ◽  
Author(s):  
ZISHUN LIU ◽  
EDY HARSONO ◽  
SOMSAK SWADDIWUDHIPONG
Keyword(s):  
Neural Network ◽  
Material Properties ◽  
Indentation Test ◽  
Network Models ◽  
Spherical Indentation ◽  
Instrumented Indentation ◽  
Neural Network Models ◽  
Advantages And Disadvantages ◽  
Indentation Tests ◽  
Load Displacement

This paper reviews various techniques to characterize material by interpreting load-displacement data from instrumented indentation tests. Scaling and dimensionless analysis was used to generalize the universal relationships between the characteristics of indentation curves and their material properties. The dimensionless functions were numerically calibrated via extensive finite element analysis. The interpretation of load-displacement curves from the established relationships was thus carried out by either solving higher order functions iteratively or employing neural networks. In this study, the advantages and disadvantages of these techniques are highlighted. Several issues in an instrumented indentation test such as friction, size effect and uniqueness of reverse analysis algorithms are discussed. In this study, a new reverse algorithm via neural network models to extract the mechanical properties by dual Berkovich and spherical indentation tests is introduced. The predicted material properties based on the proposed neural network models agree well with the numerical input data.

Orthogonal Properties of Human Trabecular Bone by Spherical Indentation Test

2006 ◽  
Vol 326-328 ◽  
pp. 793-796
Author(s):  
Tae Soo Bae ◽  
Tae Soo Lee ◽  
Kui Won Choi
Keyword(s):  
Trabecular Bone ◽  
Apparent Density ◽  
Indentation Test ◽  
Spherical Indentation ◽  
Power Relationship ◽  
Ct Scanner ◽  
Diamond Blade ◽  
Custom Made ◽  
Indentation Tests

The elastic modulus and the apparent density of the trabecular bone were evaluated from spherical indentation tests and Computed Tomography and their relationship was quantified. After the femurs were prepared and embedded with respect to their anatomical orientation, the transverse planes of the trabecular bone specimens were scanned at 1mm intervals using a CT scanner. The metaphyseal regions were sectioned with a diamond-blade saw, producing 8mm cubes. Using a custom-made spherical indentation tester, the cubes were mechanically tested in the anteriorposterior (AP), medial-lateral (ML), and inferior-superior (IS) directions. After determination of modulus from the mechanical testing, the apparent densities of the specimens were measured. The results showed that the IS modulus was significantly greater than both the AP and ML moduli with the AP modulus greater than the ML modulus. This demonstrated that orthogonality was a structural characteristic of the trabecular bone. The power relationship between the modulus and the apparent density was also found to be statistically significant.

Determination of Young's modulus by spherical indentation

1997 ◽  
Vol 12 (9) ◽  
pp. 2459-2469 ◽  
Author(s):  
N. Huber ◽  
D. Munz ◽  
Ch. Tsakmakis
Keyword(s):  
Finite Element ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Indentation Test ◽  
Spherical Indentation ◽  
Plastic Materials ◽  
Finite Element Calculations ◽  
Loading And Unloading ◽  
Elastic Plastic Materials

In this paper we consider elastic plastic materials that are tested by spherical indentation. Finite element calculations, which take into account nonlinear geometry properties, are carried out in order to determine the influence of the plastic history on the unloading response of the material. Two different iterative methods are proposed for determining Young's modulus under the assumption of a bilinear plasticity law. The first method deals with loading and unloading parts of the indentation test, whereas the second one deals only with unloading parts of the indentation test.

An Expanding Cavity Model for Indentation Analysis of Shape Memory Alloys

2019 ◽  
Vol 87 (3) ◽  
Author(s):  
J. Anuja ◽  
R. Narasimhan ◽  
U. Ramamurty
Keyword(s):  
Phase Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Indentation Test ◽  
Spherical Indentation ◽  
Cavity Model ◽  
Functional Responses ◽  
Indentation Tests ◽  
Indentation Analysis ◽  
Analytical Expressions

Abstract The mechanical and functional responses of shape memory alloys (SMAs), which are often used in small volume applications, can be evaluated using instrumented indentation tests. However, deciphering the indentation test results in SMAs can be complicated due to the combined effects of the non-uniform state of stress underneath the indenter and stress-induced phase transformation. To address this issue, an expanding cavity model (ECM) applicable to spherical indentation of SMAs is developed in this work based on an analytical solution for an internally pressurized hollow sphere. Analytical expressions for key indentation parameters such as the mean contact pressure and size of the transforming zone are obtained, whose validity is evaluated by recourse to finite element simulations and published experimental data for a Ni–Ti alloy. It is shown that the ECM predicts the above parameters reasonably well for indentation strains varying from 0.01 to 0.04. Also, a method is proposed to determine the critical stress required to initiate phase transformation under uniaxial compression based on the application of the ECM to interpret the indentation stress–strain response.

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