scholarly journals Round Robin into Best Practices for the Determination of Indentation Size Effects

Nanomaterials ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 130 ◽  
Author(s):  
Ana Ruiz-Moreno ◽  
Peter Hähner ◽  
Lukasz Kurpaska ◽  
Jacek Jagielski ◽  
Philippe Spätig ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Size Effects ◽  
Nuclear Fission ◽  
Round Robin ◽  
Indentation Hardness ◽  
Martensitic Steels ◽  
Indentation Size ◽  
Single Cycle ◽  
Fusion Applications ◽  
Methodological Bias

The paper presents a statistical study of nanoindentation results obtained in seven European laboratories that have joined a round robin exercise to assess methods for the evaluation of indentation size effects. The study focuses on the characterization of ferritic/martensitic steels T91 and Eurofer97, envisaged as structural materials for nuclear fission and fusion applications, respectively. Depth-controlled single cycle measurements at various final indentation depths, force-controlled single cycle and force-controlled progressive multi-cycle measurements using Berkovich indenters at room temperature have been combined to calculate the indentation hardness and the elastic modulus as a function of depth applying the Oliver and Pharr method. Intra- and inter-laboratory variabilities have been evaluated. Elastic modulus corrections have been applied to the hardness data to compensate for materials related systematic errors, like pile-up behaviour, which is not accounted for by the Oliver and Pharr theory, and other sources of instrumental or methodological bias. The correction modifies the statistical hardness profiles and allows determining more reliable indentation size effects.

A study of indentation work in homogeneous materials

2006 ◽  
Vol 21 (6) ◽  
pp. 1363-1374 ◽  
Author(s):  
Mengxi Tan
Keyword(s):  
Plastic Deformation ◽  
Elastic Modulus ◽  
Elastic Energy ◽  
Size Effects ◽  
Unit Volume ◽  
Plastic Work ◽  
Total Work ◽  
Indentation Size ◽  
Scaling Relationships ◽  
Homogeneous Materials

The work of indentation is investigated experimentally in this article. A method of using the elastic energy to extract the elastic modulus is proposed and verified. Two types of hardness related to the work of indentation are defined and examined: Hwtis defined as the total work required creating a unit volume of contact deformationand Hwp is defined as the plastic work required creating a unit volume of plastic deformation; experiments show that both hardness definitions are good choices for characterizing hardness. Several features that may provide significant insights in understanding indentation measurements are studied. These features mainly concern some scaling relationships in indentation measurements and the indentation size effects.

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.

Investigation of the Bi-linear Behavior of the Indentation Size Effects in Single and Polycrystalline Ni Thin Films/MEMS Thin Films

2006 ◽  
Vol 976 ◽  
Author(s):  
Abdelmageed A. Elmustafa ◽  
J. Lou ◽  
Z. Zong ◽  
W. O. Soboyejo
Keyword(s):  
Thin Films ◽  
Experimental Study ◽  
Size Effects ◽  
Size Dependence ◽  
Indentation Hardness ◽  
Indentation Size ◽  
Dislocation Source ◽  
Nano Scale ◽  
Linear Behavior ◽  
Dislocation Hardening

AbstractThis paper presents the results of an experimental study of the indentation size effects at the nano, sub-micron, and micron-scales. The size dependence of the indentation hardness in these regimes is shown to exhibit a bi-linear behavior when the data are fitted to Taylor Dislocation Hardening (TDH) model. The deformation in indent sizes corresponding to the onset of the transition from micro and deep nano indents to shallow nano indents represent dislocation substructures at the sub-micron and micron scales whereas the deformation at the nano-scale represents dislocation source-limited behavior.

Nanoindentation measurement of hardness and modulus anisotropy in Ni3Al single crystals

2002 ◽  
Vol 17 (9) ◽  
pp. 2314-2320 ◽  
Author(s):  
W. Wang ◽  
K. Lu
Keyword(s):  
Elastic Modulus ◽  
Single Crystals ◽  
Indentation Load ◽  
Indentation Hardness ◽  
Gradient Plasticity ◽  
Indentation Size ◽  
Hardness Anisotropy ◽  
Nanoindentation Measurement ◽  
Small Anisotropy ◽  
Strain Gradient Plasticity Theory

Hardness and elastic modulus of (111), (110), and (001) oriented Ni3Al single crystals were determined by nanoindenter measurements. Obvious elastic modulus anisotropy and hardness anisotropy were observed. The modulus for (001) was about 17% smaller than that for (111), (110). The hardness was found to be strongly dependent on the indentation size and exhibited a small anisotropy at low indentation loads. When the indentation load was increased further, the hardness anisotropy became apparent. The hardness for (111) was observed to be higher compared to (001). The indentation hardness size effect was examined by using strain gradient plasticity theory.

scholarly journals Investigation on the Influences of Hygrothermal Aging on the Indentation Size Effects and Micro-Indentation Measurements of PMMA. Part I: Experimental Results

2020 ◽  
Vol 10 (16) ◽  
pp. 5454 ◽  
Author(s):  
Hui Lin ◽  
Lin Lv ◽  
Tao Jin
Keyword(s):  
Elastic Modulus ◽  
Aging Time ◽  
Size Effects ◽  
Companion Paper ◽  
Strain Rates ◽  
Indentation Size ◽  
Hygrothermal Aging ◽  
Shear Transformation ◽  
Micro Indentation ◽  
Indentation Strain

The polymethyl methacrylate (PMMA) subjected to hygrothermal aging was applied to nanoindentation tests under different indentation strain rates. The influences of hygrothermal aging on the indentation behaviors of PMMA are discussed. Results show that the indentation elastic modulus and hardness decrease with increasing aging time. Furthermore, the indentation size effects (ISE) can be observed in aged PMMA specimens as they are sensitive to aging time as well as to the indentation strain rate. The quantitative analysis of ISE is proposed on the basis of shear transformation-mediated plasticity and was presented in our companion paper.

On the origin of indentation size effects and depth dependent mechanical properties of elastic polymers

2016 ◽  
Vol 36 (1) ◽  
pp. 103-111 ◽  
Author(s):  
Chung-Souk Han ◽  
Seyed H.R. Sanei ◽  
Farid Alisafaei
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Size Effects ◽  
Indentation Depth ◽  
Second Order ◽  
Indentation Size

Abstract Indentation size effects have been observed in both polymers and metals but, unlike in metals, the origin of size effects in polymers is not well understood. To clarify the role of second order gradients of displacements, a model polymer is examined with spherical and Berkovich tips at probing depths between 5 and 25 μm. Applying different theories to determine the elastic modulus, it is found that with a pyramidal tip, the elastic modulus increases with decreasing indentation depth, while tests with the spherical tip yielded essentially constant values for the elastic modulus independent of indentation depth. The differences between these tips are attributed to second order displacement gradients, as they remain essentially constant with a spherical tip while they increase in magnitude with decreasing indentation depth applying a Berkovich tip.

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.

New expanding cavity model for indentation hardness including strain-hardening and indentation size effects

2006 ◽  
Vol 21 (5) ◽  
pp. 1317-1326 ◽  
Author(s):  
X.-L. Gao
Keyword(s):  
Strain Hardening ◽  
Young’S Modulus ◽  
Strain Gradient ◽  
Young's Modulus ◽  
Indentation Hardness ◽  
Cavity Model ◽  
Indentation Size ◽  
New Model ◽  
Plastic Materials ◽  
Classical Plasticity

An expanding cavity model (ECM) for determining indentation hardness of elastic–strain-hardening plastic materials is developed. The derivation is based on a strain gradient plasticity solution for an internally pressurized thick-walled spherical shell of an elastic linear-hardening material. Closed-form formulas are provided for both conical and spherical indentations. The formulas explicitly show that indentation hardness depends on Young's modulus, yield stress, strain-hardening index, and strain gradient coefficient of the indented material as well as on the geometry of the indenter. The newly formulated ECM can capture the indentation size effect, unlike classical plasticity based ECMs. The new model reduces to existing classical plasticity based ECMs (including Johnson's ECM for elastic-perfectly plastic materials) when the strain gradient effect is not considered. The presently developed ECM is validated by comparing with existing experimental hardness data. The numerical results obtained using the new model reveal that the hardness is indeed indentation size dependent when the indentation radius is very small: the smaller the indentation, the larger the hardness. Also, the indentation hardness is seen to increase with the Young's modulus and strain-hardening level of the indented material for both conical and spherical indentations. The strain-hardening effect on the hardness is observed to be significant for materials having strong strain-hardening characteristics. In addition, it is found that the indentation hardness increases with decreasing cone angle of the conical indenter or decreasing radius of the spherical indenter. These trends agree with existing experimental observations and model predictions.

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