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.

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.

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.

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.

Effect of Nonlinear Kinematic Hardening Constants on Cyclic Spherical Indentation Test

2010 ◽  
Author(s):  
A. Nayebi
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Applied Load ◽  
Kinematic Hardening ◽  
Hysteresis Loops ◽  
Indentation Test ◽  
Material Behavior ◽  
Spherical Indentation ◽  
Displacement Curve ◽  
Residual Displacements

In the last decade, instrumented indentation test has been widely used to determine the mechanical properties of different materials and especially for metals. The mechanical properties such as Young modulus, yield stress, hardening exponent, and stress-strain curve were determined with the help of the load–displacement curve of the continuous indentation test. The method consists of pushing an indenter in a material sample and the applied load and the indenter displacement are measured. In this research the load on the indenter was considered as cyclic and varied from zero to Fmax. Because of the Bauschinger effect, the hysteresis loops were formed. With the help of these hysteresis loops, nonlinear kinematic hardening parameters of the Armstrong–Freiderick (A-F) model can be determined. Spherical indenter was used and the sample was considered isotropic. The material behavior was modeled by the A-F rule. The test was modeled by the finite element method. An axi-symmetric mesh was used. The A–F model constants, C and γ, were varied to obtain their effects on the hysteresis loops. Maximum applied load was considered constant for different finite element modeling and the maximum and residual displacements were calculated from the simulations results. The normalized maximum and the residual displacements were increased as a function of the cycles. It was shown that these parameters value and their rate are dependent on the material model constants. These dependences were shown for different examples which can help to characterize the A-F model constants by the cyclic spherical indentation tests.

Evaluation of Indentation Test for Measuring Young’s Modulus of Cancellous Bone

2007 ◽  
Vol 544-545 ◽  
pp. 307-310
Author(s):  
Moon Kyu Lee ◽  
Kui Won Choi ◽  
Tae Soo Lee ◽  
H.N. Lim
Keyword(s):  
Porous Materials ◽  
Young’S Modulus ◽  
Cancellous Bone ◽  
Indentation Depth ◽  
Young's Modulus ◽  
Indentation Test ◽  
Spherical Indentation ◽  
Uniaxial Compression Test ◽  
Displacement Curve ◽  
Fe Model

The indentation test has been in the spotlight due to easy and non-destructive testing characteristics. However, there are little studies for the indentation test of porous materials in the evaluation aspect of methodology. The goal of this study was to evaluate a spherical indentation test in the aspect of indenter-size and indentation depth by measuring elastic modulus of porous materials such as a cancellous bone using a FEM. We developed a microstructure-based FE model of cancellous bone with apparent density 0.2~0.8 g/cm3 in order to simulate uniaxial compression test and indentation test in the light of anatomical observation with a scanning electron microscope (SEM). We obtained a load-displacement curve through the indentation simulation and calculated the Young’s modulus of cancellous structure based on Pharr's hypothesis. The result indicated that indenter diameter has to be more than five times of pore size and indentation depth should be about 8% of indenter diameter at least to obtain the appropriate result of the indentation test. It is expected that this result may guide to the design and the simulation of indentation test for porous materials

Mechanical properties evaluation for engineering materials utilizing instrumented indentation: Finite element modelling approach

2021 ◽  
Vol 15 (1) ◽  
pp. 7671-7683
Author(s):  
Ahmed F. Elmisteri ◽  
Farag M. Shuaeib ◽  
Abdelbaset R. H. Midawi
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Finite Element Simulation ◽  
Plastic Region ◽  
Indentation Test ◽  
Strain Curve ◽  
Instrumented Indentation ◽  
Indentation Technique ◽  
Element Simulation ◽  
Engineering Materials

Instrumented indentation technique gives the possibility to determine the mechanical properties for small specimens and material in service. Several researchers have attempted to evaluate this approach experimentally and investigated the factors that affect it by using different indenter’s geometries for different engineering materials. In this work, the instrumented indentation technique was used to evaluate the mechanical properties experimentally and numerically using finite element simulation to understand the contact mechanics between the indenter surface and the substrate for two types of steel alloys namely ASTM516-G70 and AISI1010 steel. Two shapes of indenters, blunt (spherical) and sharp (Vickers) were used. The results were then compared with the experimental results extracted from the instrumented indentation test. The results have demonstrated a good agreement between the experimental and the finite element simulation results with error bound a ±5 % for young’s modulus and ±7.7 % for yield strength. Whereas excellent agreement is observed in the elastic region and the beginning of the plastic region for the true stress-strain curve. Finally, it is to be emphasized that the obtained results are more applicable for the tested materials and further research is recommended to accommodate other materials as well and to confirm the generality of this method.

New sharp indentation method of measuring the elastic–plastic properties of compliant and soft materials using the substrate effect

2006 ◽  
Vol 21 (12) ◽  
pp. 3134-3151 ◽  
Author(s):  
Manhong Zhao ◽  
Xi Chen ◽  
Nagahisa Ogasawara ◽  
Anghel Constantin Razvan ◽  
Norimasa Chiba ◽  
...  
Keyword(s):  
Finite Thickness ◽  
Indentation Test ◽  
Soft Materials ◽  
Substrate Effect ◽  
Plastic Properties ◽  
Application Range ◽  
Elastic Plastic ◽  
Elastoplastic Properties ◽  
Uniqueness Of The Solution ◽  
Sharp Indentation

We propose a new theory with the potential for measuring the elastoplastic properties of compliant and soft materials using one sharp indentation test. The method makes use of the substrate effect, which is usually intended to be avoided during indentation tests. For indentation on a compliant and soft specimen of finite thickness bonded to a stiff and hard testing platform (or a compliant/soft thin film deposited on a stiff/hard substrate), the presence of the substrate significantly enhances the loading curvature which, theoretically, enables the determination of the material power-law elastic-plastic properties by using just one conical indentation test. Extensive finite element simulations are carried out to correlate the indentation characteristics with material properties. Based on these relationships, an effective reverse analysis algorithm is established to extract the material elastoplastic properties. By utilizing the substrate effect, the new technique has the potential to identify plastic materials with indistinguishable indentation behaviors in bulk forms. The error sensitivity and uniqueness of the solution are carefully investigated. Validity and application range of the proposed theory are discussed. In the limit where the substrate is taken to be rigid, the fundamental research is one of the first steps toward understanding the substrate effect during indentation on thin films deposited on deformable substrates.

New Approach to Stress-Strain Curve Prediction Using Ball Indentation Test

2011 ◽  
Author(s):  
Jan Brumek ◽  
Bohumi´r Strnadel ◽  
Ivo Dlouhy´
Keyword(s):  
Mechanical Properties ◽  
Indentation Test ◽  
Strain Curve ◽  
High Strength ◽  
Stress Strain ◽  
Element Analysis ◽  
Indentation Technique ◽  
Strain Behavior ◽  
Ball Indentation ◽  
Ball Indentation Test

This work is concerned with the method for predicting stress-strain behavior of material using instrumented indentation technique. High strength low alloy steel with different thermal treatment was taken into the analysis. Heat treatment for the steel was performed to obtain different mechanical properties. Assessment of mechanical properties was done by using inverse technique of the finite element analysis. The results were confronted with conventional test parameters and prediction procedure defined such Automated Ball Indentation Technique (ABIT). Comparison of the material curves shows good agreement with tensile test properties which makes this non-destructive method suitable for industrial application.

Characterisation of Elastoplastic Behaviour Using Spherical Indentation

2006 ◽  
Vol 514-516 ◽  
pp. 744-748
Author(s):  
António Castanhola Batista ◽  
José P. Marinheiro ◽  
Joao P. Nobre ◽  
A. Morão Dias
Keyword(s):  
Inverse Method ◽  
Indentation Test ◽  
Strain Curve ◽  
Tensile Tests ◽  
Spherical Indentation ◽  
Stress Strain Curve ◽  
Hardening Law ◽  
Behaviour Study ◽  
Behaviour Law ◽  
Good Agreement

An inverse method for the characterisation of the elastoplastic behaviour of materials has been studied. The method is based on spherical indentation test data and numerical analysis of the indentation process, enabling to find a characteristic stress-strain curve. This method will be appropriate for elastoplastic behaviour study, mainly on surface hardened materials, when the standard methods cannot be applied. In this work, the method was applied to annealed and quenched steels, with homogeneous properties over the cross section. The obtained results are in good agreement with those obtained from the standard tensile tests. However, if the material does not follow a linear hardening law, the elastoplastic characteristics determined by the inverse method will depend on the indentation depth. For these cases a method for the evaluation of the actual behaviour law has been improved.

Sign in / Sign up

Export Citation Format

Share Document