Improvement of predicting mechanical properties from spherical indentation test

2016 ◽  
Vol 117 ◽  
pp. 182-196 ◽  
Author(s):  
Yingzhi Li ◽  
Paul Stevens ◽  
Mingcheng Sun ◽  
Chaoqun Zhang ◽  
Wei Wang
Keyword(s):  
Mechanical Properties ◽  
Indentation Test ◽  
Spherical Indentation

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.

Characterization of mechanical properties of metallic foams by instrumented indentation test

2018 ◽  
Vol 115 (4) ◽  
pp. 405
Author(s):  
Ali Nayebi ◽  
Azam Surmiri
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Constitutive Model ◽  
Indentation Test ◽  
Metallic Foam ◽  
Spherical Indentation ◽  
Metallic Foams ◽  
Aluminum Foams ◽  
Inelastic Behaviour ◽  
Indentation Response

In this study, the spherical indentation tests with a spherical rigid indenter of 5 mm radius were used. The inelastic behaviour of metallic foam was considered as an isotropic crushable foam constitutive model of Deshpande and Fleck which has been shown experimentally that their model can be applied to aluminum foams. The spherical indentation test was modeled by finite element method. A 2D axisymmetric model was developed. Practically, the size of the indenter tip should be reasonably large compared to the size of the cells/pores in the specimen and the indentation depth should also be reasonably large so that the indentation response does reflect the averaged material behaviours, which are described by the aforementioned constitutive model. The applied load on the indenter versus its displacement was obtained under different metallic foam mechanical properties. Numerical results from the finite element simulations are used to obtain the dependence of the indentation response on the metallic foam material parameters which characterizes the plastic deformation of metallic foams. Finally, the stress–curves and the elastic modulus of different foams are obtained by the indentation curve, which is obtained by FEM.

Inverse Characterization of Nonlinear Anisotropic Mechanical Properties of Engineered Cardiovascular Tissues Using a Spherical Indentation Test

2007 ◽  
Author(s):  
M. A. J. Cox ◽  
R. A. Boerboom ◽  
C. V. C. Bouten ◽  
N. J. B. Driessen ◽  
F. P. T. Baaijens
Keyword(s):  
Mechanical Properties ◽  
Soft Tissues ◽  
Indentation Test ◽  
Tensile Tests ◽  
Material Behavior ◽  
Uniaxial Tensile ◽  
Spherical Indentation ◽  
Mechanical Conditioning ◽  
Indentation Tests

Over the last few years, research interest in tissue engineering as an alternative for e.g. current treatment and replacement strategies for cardiovascular and heart valve diseaes has significantly increased. In vitro mechanical conditioning is an essential tool for engineering strong implantable tissues [1]. Detailed knowledge of the mechanical properties of the native tissue as well as the properties of the developing engineered constructs is vital for a better understanding and control of the mechanical conditioning process. The typical highly nonlinear and anisotropic behavior of soft tissues puts high demands on their mechanical characterization. Current standards in mechanical testing of soft tissues include (multiaxial) tensile testing and indentation tests. Uniaxial tensile tests do not provide sufficient information for characterizing the full anisotropic material behavior, while biaxial tensile tests are difficult to perform, and boundary effects limit the test region to a small central portion of the tissue. In addition, characterization of the local tissue properties from a tensile test is non-trivial. Indentation tests may be used to overcome some of these limitations. Indentation tests are easy to perform and when indenter size is small relative to the tissue dimensions, local characterization is possible. Therefore, we propose a spherical indentation test using finite deformations.

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.

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.

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