scholarly journals The Correlation of Indentation Size Effect Experiments with Pyramidal and Spherical Indenters

2001 ◽  
Vol 695 ◽  
Author(s):  
J. G. Swadener ◽  
E. P. George ◽  
G. M. Pharr
Keyword(s):  
Size Effect ◽  
Work Hardening ◽  
Size Effects ◽  
Indentation Size Effect ◽  
Experimental Results ◽  
Indentation Size ◽  
Depth Of Penetration ◽  
Wide Range ◽  
Sphere Radius

ABSTRACTExperiments were conducted in annealed iridium using pyramidal and spherical indenters over a wide range of load. For a Berkovich pyramidal indenter, the hardness increased with decreasing depth of penetration. However, for spherical indenters, hardness increased with decreasing sphere radius. Based on the number of geometrically necessary dislocations generated during indentation, a theory that takes into account the work hardening differences between pyramidal and spherical indenters is developed to correlate the indentation size effects measured with the two indenters. The experimental results verify the theoretical correlation.

scholarly journals Atomic force microscopy study of nanoindentation deformation and indentation size effect in MgO crystals

1999 ◽  
Vol 14 (10) ◽  
pp. 3973-3982 ◽  
Author(s):  
K. Sangwal ◽  
P. Gorostiza ◽  
J. Servat ◽  
F. Sanz
Keyword(s):  
Experimental Data ◽  
Plastic Deformation ◽  
Atomic Force Microscopy ◽  
Size Effect ◽  
Deformation Zone ◽  
Indentation Size Effect ◽  
Indentation Size ◽  
Depth Of Penetration ◽  
Force Microscopy ◽  
Atomic Force

The dependences of various nanoindentation parameters, such as depth of penetration d, indentation diameter a, deformation zone radius R, and height h of hills piled up around indents, on applied load were investigated for the initial (unrecovered) stage of indentation of the (100) cleavage faces of MgO crystals by square pyramidal Si tips for loads up to 10 μN using atomic force microscopy. The experimental data are analyzed using theories of elastic and plastic deformation. The results revealed that (i) a, R, and h linearly increase with d; (ii) the development of indentation size and deformation zone and the formation of hills are two different processes; (iii) the load dependence of nanohardness shows the normal indentation size effect (i.e., the hardness increases with a decrease in load); and (iv) there is an absence of plastic deformation involving the formation of slip lines around the indentations. It is found that Johnson's cavity model of elastic–plastic boundary satisfactorily explains the experimental data. The formation of hills around indentations is also consistent with a new model (i.e., indentation crater model) based on the concept of piling up of material of indentation cavity as hills.

Indentation Size Effects in Ductile and Brittle Materials

2013 ◽  
Vol 586 ◽  
pp. 51-54
Author(s):  
Jaroslav Menčík ◽  
Martin Elstner
Keyword(s):  
Size Effect ◽  
Size Effects ◽  
Indentation Size Effect ◽  
Brittle Materials ◽  
Indentation Hardness ◽  
Indentation Size ◽  
Homogeneous Materials

Indentation hardness of homogeneous materials should be constant. However, at very small depths, the apparent hardness often increases with decreasing imprint size. The paper discusses various cases of this indentation size effect in metals and ceramics and explains the extrinsic and intrinsic reasons.

On the Time Dependence of Size Effect in Polydimethylsiloxane

2013 ◽  
Author(s):  
F. Alisafaei ◽  
Seyed Hamid Reza Sanei ◽  
E. J. Smith ◽  
Chung-Souk Han
Keyword(s):  
Size Effect ◽  
Time Dependence ◽  
Size Effects ◽  
Indentation Depth ◽  
Applied Force ◽  
Experimental Results ◽  
Time Dependent ◽  
Deformation Mechanisms ◽  
Indentation Size ◽  
Hardness Model

Nanoindentation tests at the nano-micrometer scales are conducted to investigate the depth and time dependent deformation mechanisms of polydimethylsiloxane (PDMS). Astonishing indentation size effects observed in these experiments are analyzed with an existing theoretical hardness model, and the effects of loading time on the hardness and indentation stiffness of PDMS are studied. The change in the indentation recovery with respect to indentation depth and loading time are analyzed. Furthermore, it is shown that the stiffness of PDMS obtained at the maximum applied force can be efficiently applied to validate the applied theoretical hardness model with the experimental results.

scholarly journals INDENTATION SIZE EFFECT IN HIGH PRESSURE TORSION PROCESSED HIGH ENTROPY ALLOY

2020 ◽  
Vol 27 ◽  
pp. 141-144
Author(s):  
Petr Haušild ◽  
Jakub Čížek ◽  
Jaroslav Čech ◽  
Jiří Zýka ◽  
Hyoung Seop Kim
Keyword(s):  
High Pressure ◽  
Size Effect ◽  
Indentation Size Effect ◽  
High Pressure Torsion ◽  
High Entropy Alloy ◽  
Indentation Size ◽  
Depth Of Penetration ◽  
Slow Cooling ◽  
Cast Sample ◽  
High Entropy

High entropy alloy HfNbTaTiZr in as cast conditions and after high pressure torsion straining was characterized by nanoindentation. The length-scale dependent material response (indentation size effect) was characterized by indentation at various indentation depths. Hardness dependence on the characteristic length (depth of penetration) indicated decomposition of disordered high entropy alloy in the as cast sample, which probably occurred during slow cooling after casting. Subsequent severe plastic deformation by high pressure torsion led on the other hand to the short-range disorder of (originally partially decomposed as cast) structure. Further hardening was generated during high pressure torsion by the mechanisms of grain refinement and increasing dislocation density.

Nanoindentation Size Effects for Calcium Silicate Hydrate

2010 ◽  
Vol 177 ◽  
pp. 537-540
Author(s):  
Wu Yao ◽  
Kang Liang
Keyword(s):  
Size Effect ◽  
Size Effects ◽  
Calcium Silicate ◽  
Calcium Silicate Hydrate ◽  
Indentation Size Effect ◽  
High Density ◽  
Nanoindentation Test ◽  
Low Density ◽  
Indentation Size ◽  
Basic Composition

Hardness of Calcium Silicate Hydrate (CSH) at different ages was measured by nanoindentation test. The results show obvious indentation size effect in hardness of CSH. Hardness decreases with increasing depth. Moreover, both low density CSH and high density CSH follow the same size effect law in hardness. This phenomenon further indicates that two types of CSH are of the same basic composition but different packing densities.

The Identation Size Effect and Hall-Petch Behaviour of Annealed Polycrystalline Copper

2006 ◽  
Vol 976 ◽  
Author(s):  
XiaoDong Hou ◽  
T.T. Zhu ◽  
N. M. Jennett ◽  
A. J. Bushby
Keyword(s):  
Grain Size ◽  
Size Effect ◽  
Size Effects ◽  
Indentation Size Effect ◽  
Indentation Test ◽  
Small Radius ◽  
Contact Radius ◽  
Length Scale ◽  
Indentation Size ◽  
Non Destructive

AbstractMethods to obtain tensile stress-strain properties of materials from a practically non-destructive indentation test are of great industrial interest. However, to do this successfully, indentation size effects must be accounted for. Many indentation size effects, such as strain gradient plasticity and micro-pillar experiments [1], show a size dependence proportional to the inverse square root of a length scale, in common with Hall-Petch behavior. Recently, however, the indentation size effect from small radius spherical indenters has been shown, for a range of fcc metals, not to follow a Hall-Petch-like relationship but to be proportional to the inverse cube root of indenter radius [2]. Here, we investigate these differences further and present results for the indentation size effect with spherical indenters on Cu samples that have been engineered to have different grain sizes. The important experimental control parameter of the relative size of the indentation compared to the grain size is also explored since the cross over from grains significantly smaller than the contact radius to grains significantly larger than the contact radius occurs at different length scales in each sample. A thorough understanding of the various length-scale effects in the different test methods (e.g. the indentation size effect and grain size effect in indentation), is essential if a relationship, robust enough for industrial application, is to be defined to obtain tensile properties from an essentially non-destructive indentation test.

scholarly journals Investigation of the mechanism of the indentation size effect for titanium

2019 ◽  
Vol 6 (2) ◽  
pp. 18-00545-18-00545
Author(s):  
Shota HASUNUMA ◽  
Hirohisa MIYAZAKI ◽  
Takeshi OGAWA
Keyword(s):  
Size Effect ◽  
Indentation Size Effect ◽  
Indentation Size

Study of the Size Effects and Friction Conditions in Microextrusion—Part II: Size Effect in Dynamic Friction for Brass-Steel Pairs

2007 ◽  
Vol 129 (4) ◽  
pp. 677-689 ◽  
Author(s):  
Lapo F. Mori ◽  
Neil Krishnan ◽  
Jian Cao ◽  
Horacio D. Espinosa
Keyword(s):  
Grain Size ◽  
Friction Coefficient ◽  
Size Effect ◽  
Contact Pressure ◽  
Size Effects ◽  
Numerical Models ◽  
Kolsky Bar ◽  
Experimental Results ◽  
Material Response ◽  
Dynamic Coefficients

In this paper, the results of experiments conducted to investigate the friction coefficient existing at a brass-steel interface are presented. The research discussed here is the second of a two-part study on the size effects in friction conditions that exist during microextrusion. In the regime of dimensions of the order of a few hundred microns, these size effects tend to play a significant role in affecting the characteristics of microforming processes. Experimental results presented in the previous companion paper have already shown that the friction conditions obtained from comparisons of experimental results and numerical models show a size effect related to the overall dimensions of the extruded part, assuming material response is homogeneous. Another interesting observation was made when extrusion experiments were performed to produce submillimeter sized pins. It was noted that pins fabricated from large grain-size material (211μm) showed a tendency to curve, whereas those fabricated from billets having a small grain size (32μm), did not show this tendency. In order to further investigate these phenomena, it was necessary to segregate the individual influences of material response and interfacial behavior on the microextrusion process, and therefore, a series of frictional experiments was conducted using a stored-energy Kolsky bar. The advantage of the Kolsky bar method is that it provides a direct measurement of the existing interfacial conditions and does not depend on material deformation behavior like other methods to measure friction. The method also provides both static and dynamic coefficients of friction, and these values could prove relevant for microextrusion tests performed at high strain rates. Tests were conducted using brass samples of a small grain size (32μm) and a large grain size (211μm) at low contact pressure (22MPa) and high contact pressure (250MPa) to see whether there was any change in the friction conditions due to these parameters. Another parameter that was varied was the area of contact. Static and dynamic coefficients of friction are reported for all the cases. The main conclusion of these experiments was that the friction coefficient did not show any significant dependence on the material grain size, interface pressure, or area of contact.

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