Further analysis of the size effect in indentation hardness tests of some metals

1995 ◽  
Vol 10 (11) ◽  
pp. 2908-2915 ◽  
Author(s):  
M. Atkinson
Keyword(s):  
Size Effect ◽  
Strain Hardening ◽  
Indentation Size Effect ◽  
Plastic Hinge ◽  
Small Scale ◽  
Indentation Hardness ◽  
Vickers Indentation ◽  
Indentation Size ◽  
Hardness Tests ◽  
Indentation Tests

The variation of apparent hardness observed in previously reported Vickers indentation tests of metals is reexamined. Common deseriptions of the effect are shown to be inaccurate: the variation of apparent hardness is monotonic but not simple. The effect is consistent with varying size of a previously postulated “plastic hinge” at the perimeter of the indent. This complexity confers uncertainty on the estimation of characteristic macrohardness from small scale tests. Association of the indentation size effect with friction and with strain hardening is confirmed.

Indentation size effect and strain-hardening

1989 ◽  
Vol 8 (10) ◽  
pp. 1139-1140 ◽  
Author(s):  
Philip M. Sargent
Keyword(s):  
Size Effect ◽  
Strain Hardening ◽  
Indentation Size Effect ◽  
Indentation Size

scholarly journals Exploring the origins of the indentation size effect at submicron scales

2021 ◽  
Vol 118 (30) ◽  
pp. e2025657118
Author(s):  
Xiaolong Ma ◽  
Wesley Higgins ◽  
Zhiyuan Liang ◽  
Dexin Zhao ◽  
George M. Pharr ◽  
...  
Keyword(s):  
Size Effect ◽  
Indentation Size Effect ◽  
Critical Role ◽  
Small Scale ◽  
Structural Development ◽  
Depth Range ◽  
Indentation Size ◽  
Dislocation Source ◽  
Dislocation Interaction ◽  
Submicron Scale

The origin of the indentation size effect has been extensively researched over the last three decades, following the establishment of nanoindentation as a broadly used small-scale mechanical testing technique that enables hardness measurements at submicrometer scales. However, a mechanistic understanding of the indentation size effect based on direct experimental observations at the dislocation level remains limited due to difficulties in observing and quantifying the dislocation structures that form underneath indents using conventional microscopy techniques. Here, we employ precession electron beam diffraction microscopy to “look beneath the surface,” revealing the dislocation characteristics (e.g., distribution and total length) as a function of indentation depth for a single crystal of nickel. At smaller depths, individual dislocation lines can be resolved, and the dislocation distribution is quite diffuse. The indentation size effect deviates from the Nix–Gao model and is controlled by dislocation source starvation, as the dislocations are very mobile and glide away from the indented zone, leaving behind a relatively low dislocation density in the plastically deformed volume. At larger depths, dislocations become highly entangled and self-arrange to form subgrain boundaries. In this depth range, the Nix–Gao model provides a rational description because the entanglements and subgrain boundaries effectively confine dislocation movement to a small hemispherical volume beneath the contact impression, leading to dislocation interaction hardening. The work highlights the critical role of dislocation structural development in the small-scale mechanistic transition in indentation size effect and its importance in understanding the plastic deformation of materials at the submicron scale.

Residual Area Max Depth Model for Nanoindentation Hardness Size Effect of Single Crystal Silicon

2007 ◽  
Vol 339 ◽  
pp. 389-394
Author(s):  
L. Zhou ◽  
Ying Xue Yao ◽  
Shahjada Ahmed Pahlovy
Keyword(s):  
Size Effect ◽  
Single Crystal ◽  
Indentation Size Effect ◽  
Peak Load ◽  
Single Crystal Silicon ◽  
Indentation Hardness ◽  
Indentation Size ◽  
Crystal Silicon ◽  
New Model ◽  
Nanoindentation Hardness

In material nanoindentation hardness testing, the hardness will decrease with the indentation depth or peak load increase, i.e. indentation size effect (ISE). There are several models and equations were proposed to describe ISE. But the variables self-inaccurate in these models and equations, it will affect the result trueness. Single crystal silicon was used for nanoindentation experiments, and max depths were obtained from these experiments. Combining Matlab software, residual areas were obtained by atomic force microscopy (AFM). Based on max depth and residual area, a new model—residual area max depth model was proposed for indentation size effect in nanoindentaion hardness. The new model perhaps can understand and describe ISE in indentation hardness better than other models and equations.

scholarly journals Characterization of strain amplitude-dependent behavior of hardness and indentation size effect of SS400 structural steel

2020 ◽  
Vol 14 (3) ◽  
pp. 15-25
Author(s):  
Nguyen Ngoc Vinh ◽  
Vu Quoc Anh ◽  
Hong Tien Thang
Keyword(s):  
Mechanical Properties ◽  
Cyclic Loading ◽  
Size Effect ◽  
Strain Rate ◽  
Structural Steel ◽  
Indentation Size Effect ◽  
Low Cycle Fatigue ◽  
Indentation Hardness ◽  
Gradient Plasticity ◽  
Indentation Size

In this paper, the continuous stiffness measurement (CSM) indentation is employed to investigate fatigue mechanical properties of structural steel under cyclic loading. For this purpose, several representative analytical approaches were introduced to estimate the basic mechanical properties including Young’s modulus and indentation hardness from the characteristics of the loading/unloading curves. Several experiments including CSM nanoindentation, low-cycle fatigue experiment for four strain amplitude levels, optical microscope (OM), and transmission electron microscopy (TEM) examinations were conducted to observe the variation characteristics of mechanical properties at the microscale and their micro-mechanisms. The microstructural evolution of the specimens deformed by the low-cycle fatigue was observed using the OM and TEM examinations. The standard nanoindentation experiments were then performed at different strain rate levels to characterize the influences of strain rate indentation on hardness of the material. The micro-mechanisms established based on the microstructural evolution and strain gradient plasticity theory were introduced to be responsible for the variation of indentation hardness under cyclic loading. Finally, the indentation size effect (ISE) phenomenon in SS400 structural steel was investigated and explained through the strain gradient plasticity theory regarding geometrically necessary dislocations underneath the indenter tip. The experimental results can be used for practical designs as well as for understanding the fatigue behavior of SS400 structural steel. Keywords: cyclic loading; fatigue; nanoindentation; indentation size effect; strain rate sensitivity; structural steel.

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.

Deformation behavior and indentation size effect in amorphous and crystallized Pd40Cu30Ni10P20 alloy

2009 ◽  
Vol 24 (5) ◽  
pp. 1693-1699 ◽  
Author(s):  
N. Li ◽  
L. Liu ◽  
K.C. Chan
Keyword(s):  
Amorphous Alloy ◽  
Size Effect ◽  
Deformation Behavior ◽  
Indentation Depth ◽  
Indentation Size Effect ◽  
Indentation Hardness ◽  
Indentation Size ◽  
Surface Residual Stress ◽  
Deformation Behaviors ◽  
The Difference

The deformation behavior and indentation size effect (ISE) in amorphous and crystallized Pd40Cu30Ni10P20 alloy were comparatively studied through instrumented nanoindentation. It was found that the two alloys showed different deformation behaviors, the amorphous alloy exhibited conspicuous pop-in events in the load-depth (P-h) curve, while the crystallized alloy showed a relatively smooth P-h curve. In addition, the indentation hardness was observed to decrease with increasing penetration depth in the two alloys, exhibiting a significant ISE. However, the crystallized alloy displayed a sharper reduction of hardness with indentation depth as compared to the amorphous alloy, indicating a more significant indentation size effect in the crystalline alloy. The structure difference and friction factor associated with the surface residual stress are taken into account to interpret the difference in the deformation behavior and indentation size effect of the two alloys.

Analysis of Indentation Size Effect of Vickers Hardness Tests of Steels

2013 ◽  
Vol 652-654 ◽  
pp. 1307-1310 ◽  
Author(s):  
Nyoman Budiarsa ◽  
Andrew Norbury ◽  
Xiao Xiang Su ◽  
Gareth Bradley ◽  
Xue Jun Ren
Keyword(s):  
Experimental Data ◽  
Size Effect ◽  
Power Law ◽  
Vickers Hardness ◽  
Material Properties ◽  
Indentation Size Effect ◽  
Indentation Load ◽  
Indentation Size ◽  
Load Range ◽  
Hardness Tests

In this work, the indentation size effect (ISE) in Vickers hardness tests of steel with selected heat treatments (annealed or tempered) has been investigated and analysed. Systematical hardness tests were performed within a commonly used micro-load range. The experimental data was analysed according to the Meyer power-law and the proportional specimen resistance (PSR) models and the link between ISE and material properties was discussed. The results showed that the experimental data fitted well with the Mayers power-law (P = A.dn) and the PSR (P/d = al + a2d) models. The ISE index (n) showed a good correlation with the hardness-elastic modulus ratio (H/E), which potentially could be used to predict the relative contributions of the elastic and plastic deformation contact area under indentation load and to normalize the hardness values for inverse material properties .

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
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