Uniqueness of reverse analysis from conical indentation tests

2004 ◽  
Vol 19 (8) ◽  
pp. 2498-2502 ◽  
Author(s):  
K.K. Tho ◽  
S. Swaddiwudhipong ◽  
Z.S. Liu ◽  
K. Zeng ◽  
J. Hua
Keyword(s):  
Material Properties ◽  
Plastic Material ◽  
Large Strain ◽  
Indentation Load ◽  
Initial Slope ◽  
Displacement Curve ◽  
Maximum Indentation Depth ◽  
Indentation Tests ◽  
Reverse Analysis ◽  
Load Displacement

The curvature of the loading curve, the initial slope of the unloading curve, and the ratio of the residual depth to maximum indentation depth are three main quantitiesthat can be established from an indentation load-displacement curve. A relationship among these three quantities was analytically derived. This relationship is valid for elasto-plastic material with power law strain hardening and indented by conical indenters of any geometry. The validity of this relationship is numerically verified through large strain, large deformation finite element analyses. The existence of an intrinsic relationship among the three quantities implies that only two independent quantities can be obtained from the load-displacement curve of a single conical indenter. The reverse analysis of a single load-displacement curve will yield non-unique combinations of elasto-plastic material properties due to the availability of only two independent quantities to solve for the three unknown material properties.

scholarly journals Application of Nanoindentation in the Characterization of a Porous Material with a Clastic Texture

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4579
Author(s):  
Sathwik S. Kasyap ◽  
Kostas Senetakis
Keyword(s):  
Materials Science ◽  
Complex Structure ◽  
Elastic Stiffness ◽  
Indentation Load ◽  
Nanoindentation Test ◽  
Displacement Curve ◽  
Indentation Tests ◽  
Materials Science And Engineering ◽  
Loading And Unloading ◽  
Load Displacement

In materials science and engineering, a significant amount of research has been carried out using indentation techniques in order to characterize the mechanical properties and microstructure of a broad range of natural and engineered materials. However, there are many unresearched or partly researched areas, such as, for example, the investigation of the shape of the indentation load–displacement curve, the associated mechanism in porous materials with clastic texture, and the influence of the texture on the constitutive behavior of the materials. In the present study, nanoindentation is employed in the analysis of the mechanical behavior of a benchmark material composed of plaster of Paris, which represents a brand of highly porous-clastic materials with a complex structure; such materials may find many applications in medicine, production industry, and energy sectors. The focus of the study is directed at the examination of the influence of the porous structure on the load–displacement response in loading and unloading phases based on nanoindentation experiments, as well as the variation with repeating the indentation in already indented locations. Events such as pop-in in the loading phase and bowing out and elbowing in the unloading phase of a given nanoindentation test are studied. Modulus, hardness, and the elastic stiffness values were additionally examined. The repeated indentation tests provided validations of various mechanisms in the loading and unloading phases of the indentation tests. The results from this study provide some fundamental insights into the interpretation of the nanoindentation behavior and the viscoelastic nature of porous-clastic materials. Some insights on the influence of indentation spacing to depth ratio were also obtained, providing scope for further studies.

Simulation of sub-micron indentation tests with spherical and Berkovich indenters

2001 ◽  
Vol 16 (7) ◽  
pp. 2149-2157 ◽  
Author(s):  
A. C. Fischer-Cripps
Keyword(s):  
Experimental Data ◽  
Elastic Modulus ◽  
Material Properties ◽  
Indentation Testing ◽  
Depth Sensing ◽  
Displacement Response ◽  
Analysis Methods ◽  
Detailed Treatment ◽  
Indentation Tests ◽  
Load Displacement

The present work is concerned with the methods of simulation of data obtained from depth-sensing submicron indentation testing. Details of analysis methods for both spherical and Berkovich indenters using multiple or single unload points are presented followed by a detailed treatment of a method for simulating an experimental load–displacement response where the material properties such as elastic modulus and hardness are given as inputs. A comparison between simulated and experimental data is given.

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.

The Deformation Mechanism at Pop-In: Monocrystalline Silicon under Nanoindentation with a Berkovich Indenter

2008 ◽  
Vol 389-390 ◽  
pp. 453-458 ◽  
Author(s):  
Li Chang ◽  
Liang Chi Zhang
Keyword(s):  
Mechanical Properties ◽  
Phase Transition ◽  
Loading Rate ◽  
Monocrystalline Silicon ◽  
Displacement Curve ◽  
Berkovich Indenter ◽  
Rapid Loading ◽  
Slope Change ◽  
Indentation Tests ◽  
Load Displacement

This paper investigates the “pop-in” behavior of monocrystalline silicon under nanoindentation with a Berkovich indenter. The indentation tests were carried out under ultra-low loads, i.e. 100 μN and 300 μN, with different loading/unloading rates. It was found that with the experimentally determined area function of the indenter tip, the mechanical properties of silicon can be accurately calculated from the load-displacement data, that a pop-in event represents the onset of phase transition, and that a lower loading rate favours a sudden volume change but a rapid loading process tends to generate a gradual slope change of the load-displacement curve.

THE PLASTICITY OF MONOCRYSTALLINE SILICON UNDER NANOINDENTATION

2008 ◽  
Vol 22 (31n32) ◽  
pp. 6022-6028 ◽  
Author(s):  
LI CHANG ◽  
L. C. ZHANG
Keyword(s):  
Plastic Deformation ◽  
Shape Change ◽  
Indentation Load ◽  
Monocrystalline Silicon ◽  
Displacement Curve ◽  
Wide Range ◽  
Rapid Loading ◽  
Load Displacement ◽  
The Difference ◽  
Critical Contact

This paper focuses on a fundamental understanding of the plastic deformation mechanism in monocrystalline silicon subjected to nanoindentation. It was found that over a wide range of indentation loads from 100 μN to 30 mN and loading/unloading rates from 3.3 μN/s to 10 mN/s, the plasticity of silicon is mainly caused by stress-induced phase transitions. The results indicate that the critical contact pressure for phase transition at unloading is almost constant, independent of the maximum indentation load ( P max ) and loading/unloading rates. However, the shape of the load-displacement curves greatly relies on the loading/unloading conditions. In general, higher P max and lower unloading/loading rates favor an abrupt volume change and thus a discontinuity in the load-displacement curve, commonly referred to as pop-in and/or pop-out events; whereas smaller P max and rapid loading/loading processes tend to generate gradual slope changes of the curves. This study concludes that the difference in the curve shape change does not indicate the mechanism change of plastic deformation in silicon.

scholarly journals Erratum: “Indentation responses of time-dependent films on stiff substrates” [J. Mater. Res. 19, 2487 (2004)]

2004 ◽  
Vol 19 (10) ◽  
pp. 3120-3121
Keyword(s):  
Power Law ◽  
Peak Load ◽  
Indentation Load ◽  
Small Peak ◽  
Peak Loads ◽  
Materials Research ◽  
Indentation Tests ◽  
Unloading Rate ◽  
Loading And Unloading ◽  
Load Displacement

This article appeared in the August 2004 issue of Journal of Materials Research. The following corrections are required.Section II. Experiments p. 2488The third paragraph in the Experiments section should appear as follows:One mechanism to explore changes in the shape of an indentation load-displacement response is to normalize the trace by its peak point. It has been demonstrated that the normalized [h/h(PMAX), P/PMAX] experimental responses for bulk polymers indented at constant loading- and unloading rate with the same rise time (but at different peak load levels) are identical. Figure 1(a) shows raw load-displacement data for indentation tests performed at small peak loads in the thickest polymer film (Epon) in the current study. The peak loads, 1 and 2 mN, were chosen to correspond to depths less than 10% of the film thickness in both cases. The responses normalize to the same shape [Fig. 1(b)]. When the 1-mN normalized response is compared with those from much greater load levels (50 and 500 mN), there are clear changes in the shape of the response, both loading and unloading [Fig. 1(c)]. In particular, the loading response shifts from slightly less than quadratic (power law fit with exponent 1.8) for the 1-mN response, as would be expected for a quadratic material with some creep effect; to a response between quadratic and cubic (power law fit with exponent 2.6) for the 500-mN response. The unloading response is also altered in shape, with a steeper unloading tangent at the larger load.

Characterization and Modeling of Large Displacement Micro-/Nano-Indentation of Polymeric Solids

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Y. C. Lu ◽  
D. M. Shinozaki
Keyword(s):  
Large Strain ◽  
Large Displacement ◽  
Plastic State ◽  
Large Strains ◽  
Displacement Curve ◽  
Plastic Properties ◽  
Indentation Tests ◽  
The Mean ◽  
Strain Hardening Behavior ◽  
Micro Indentation

Large displacement micro-indentation tests have been performed on various polymeric solids to measure the plastic properties. Cylindrical flat-ended indenters with diameter in the range of 10–90 μm are mostly used. The mechanism of large-strain indentation has been examined with optical microscopy and finite element simulations. Results show that under a flat-tipped indenter, the material can quickly reach a fully plastic state. The size (diameter) of the plastic zone is constant in large-strain regions and unaffected by the exact tip profile (flat, spherical, and conical). The indentation stress-displacement curve at large strains is linear as a result of the steady-state plastic flow, from which the mean indentation pressure, a measure of yield strength, can be readily extrapolated. The indentation stress-displacement response is independent of the indenter diameters but strongly dependent on the strain-hardening behavior of the material and the friction between a material and an indenter. Compared with other shaped indenters, the flat-ended indenter requires the least penetration depth in order to probe the plastic properties of a material or structure.

Prediction of the Bilinear Stress-Strain Curve of Engineering Material by Nanoindentation Test

2010 ◽  
Vol 437 ◽  
pp. 589-593
Author(s):  
Tung Sheng Yang ◽  
Te Hua Fang ◽  
C.T. Kawn ◽  
G.L. Ke ◽  
S.Y. Chang
Keyword(s):  
Plastic Material ◽  
Bulk Material ◽  
Strain Curve ◽  
Nanoindentation Test ◽  
Displacement Curve ◽  
Film Material ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Plastic Properties ◽  
Indentation Tests

Instrumented indentation is widely used to probe the elastic and plastic properties of engineering materials. Finite Element Method (FEM) has been widely used for numerical simulation of indentation tests on bulk and film material in order to analyze its deformation response. This study proposed an improved technique to determine the stress-strain curve of bulk material. FEM in conjunction with an abductive network is used to predict the stress-strain relationship of bilinear elastic-plastic material from the nanoindentation test’s force-displacement curve.

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