scholarly journals A Neural Networks approach to characterize material properties using the spherical indentation test

2011 ◽  
Vol 10 ◽  
pp. 3062-3067 ◽  
Author(s):  
A.H. Mahmoudi ◽  
S.H. Nourbakhsh
Keyword(s):  
Neural Networks ◽  
Material Properties ◽  
Indentation Test ◽  
Spherical 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.

Evaluation of tensile strength of Al7075-SiC nanocomposite compacted by gas gun using spherical indentation test and neural networks

2016 ◽  
Vol 27 (4) ◽  
pp. 1821-1827 ◽  
Author(s):  
A. Atrian ◽  
G.H. Majzoobi ◽  
S.H. Nourbakhsh ◽  
S.A. Galehdari ◽  
R. Masoudi Nejad
Keyword(s):  
Neural Networks ◽  
Tensile Strength ◽  
Indentation Test ◽  
Spherical Indentation ◽  
Gas Gun

Examination of Prestressed Coating/Substrate Systems Using Spherical Indentation—Determination of Film Prestress, Film Modulus, and Substrate Modulus

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
James A. Mills ◽  
Hang Xiao ◽  
Xi Chen
Keyword(s):  
Material Properties ◽  
Indentation Test ◽  
Spherical Indentation ◽  
Indentation Force ◽  
Forward Analysis ◽  
Substrate Properties ◽  
Error Sensitivity Analysis ◽  
Film Substrate

There have been many studies performed with respect to the indentation of thin films affixed to a corresponding substrate base. These studies have primarily focused on determining the mechanical properties of the film. It is the goal of this paper to further understand the role that the film plays and how a potential prestressing of this film has on both the film and substrate base. It is equally important to be able to understand the material properties of the substrate since during manufacturing or long-term use, the substrate properties may change. In this study, we establish through spherical indentation a framework to characterize the material properties of both the substrate and film as well as a method to determine the prestress of the film. It is proposed that through an initial forward analysis, a set of relationships are developed. A single spherical indentation test can then be performed, measuring the indentation force at two prescribed depths, and with the relationships developed from the forward analysis, the material properties of both the film and substrate can be determined. The problem is further enhanced by also developing the capability of determining any equibiaxial stress state that may exist in the film. A generalized error sensitivity analysis of this formulation is also performed systematically. This study will enhance the present knowledge of a typical prestressed film/substrate system as is commonly used in many of today’s engineering and technical applications.

Finite Thickness Influence on Spherical and Conical Indentation on Viscoelastic Thin Polymer Film

2005 ◽  
Vol 127 (1) ◽  
pp. 33-37 ◽  
Author(s):  
V. Gonda ◽  
J. den Toonder ◽  
J. Beijer ◽  
G. Q. Zhang ◽  
L. J. Ernst
Keyword(s):  
Polymer Film ◽  
Material Properties ◽  
Finite Thickness ◽  
Thin Polymer Film ◽  
Spherical Indentation ◽  
Infinite Plane ◽  
Precise Knowledge ◽  
Thin Polymer ◽  
Measurement Results ◽  
Conical Indentation

The thermo-mechanical integration of polymer films requires a precise knowledge of material properties. Nanoindentation is a widely used testing method for the determination of material properties of thin films such as Young’s modulus and the hardness. An important assumption in the analysis of the indentation is that the indented medium is a semi-infinite plane or half space, i.e., it has an “infinite thickness.” In nanoindentation the analyzed material is often a thin film that is deposited on a substrate. If the modulus ratio is small, (soft film on hard substrate) and the penetration depth is small too, then the Hertzian assumption does not hold. We investigate this situation with spherical and conical indentation. Measurement results are shown using spherical indentation on a visco-elastic thin polymer film and a full visco-elastic characterization is presented.

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.

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.

Poroelastic Indentation Analysis for Hydrated Biological Tissues

2006 ◽  
Vol 975 ◽  
Author(s):  
Michelle L. Oyen ◽  
Amanpreet K. Bembey ◽  
Andrew J. Bushby
Keyword(s):  
Indentation Test ◽  
Biological Tissues ◽  
Time Dependent ◽  
Spherical Indentation ◽  
Indentation Creep ◽  
Polar Solvents ◽  
Viscoelastic Analysis ◽  
Wide Range ◽  
Indentation Problem

ABSTRACTIndentation techniques are employed for the measurement of mechanical properties of a wide range of materials. In particular, techniques focused at small length-scales, such as nanoindentation and AFM indentation, allow for local characterization of material properties in heterogeneous materials including natural tissues and biomimetic materials. Typical elastic analysis for spherical indentation is applicable in the absence of time-dependent deformation, but is inappropriate for materials with time-dependent responses. Recent analyses for the viscoelastic indentation problem, based on elastic-viscoelastic correspondence, have begun to address the issue of time-dependent deformation during an indentation test. The viscoelastic analysis has been shown to fit experimental indentation data well, and has been demonstrated as useful for characterization of viscoelasticity in polymeric materials and in hydrated mineralized tissues. However, a viscoelastic analysis is not necessarily sufficient for multi-phase materials with fluid flow. In the current work, a poroelastic analysis—based on fluid motion through a porous elastic network—is used to examine spherical indentation creep responses of hydrated biological materials. Both analytical and finite element approaches are considered for the poroelastic Hertzian indentation problem. Modeling results are compared with experimental data from nanoindentation of hydrated bone immersed in water and polar solvents (ethanol, methanol, acetone). Baseline (water-immersed) bone responses are characterized using the poroelastic model and numerical results are compared with altered hydration states due to polar solvents.

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