On the interpretation of the indentation size effect (ISE) through gradient theory for Vickers and Berkovich indenters

Kampouris, Asterios K.; Konstantinidis, Avraam

doi:10.1515/jmbm-2017-0003

Cited by 7 publications

(4 citation statements)

References 8 publications

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“…These two regions, protrusions and background, were found to have differing mechanical properties and crystallinities. At lower indentation depths, differences were evident in what is known as the indentation size effect (ISE) region, believed to be caused by dislocation effects [43]. Following this region, at indentation depths of 4-6 µm, the correlation between the hardness and the crystallinity, as measured by FT-IR, is similar to that observed by Slouf et al [30].…”

Section: Discussionsupporting

confidence: 71%

Anomalous Wear Behavior of UHMWPE During Sliding Against CoCrMo Under Varying Cross-Shear and Contact Pressure

et al. 2022

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Wear of ultra-high-molecular weight polyethylene (UHMWPE) in joint implant applications has been shown to increase with cross-shear (CS, i.e., multidirectional sliding) but decrease with higher contact pressure (CP). Moreover, structural changes, resulting in protrusions, are known to occur to the surface of the pin following multidirectional sliding. However, these phenomena are not yet fully understood. In this study, we simultaneously varied CP and CS to derive an empirical formula for the wear factor as a function of these parameters. The wear factor increased when going from unidirectional sliding to multidirectional sliding but decreased with increasing CP, as has been previously observed. Following these tests, the protrusions on the pin surface were chemically and mechanically characterized to gain insights into both their origin and influence on wear behavior. Micro-FT-IR confirmed that the structures consist of polyethylene, rather than adsorbed, denatured proteins. It also allowed the crystallinity of both the protrusions and unaffected UHMWPE to be estimated, showing a strong positive correlation with the hardness of these different areas on the surface. Time-of-flight secondary-ion mass spectrometry was used to probe the chemistry of the surface and near-surface region and indicated the presence of contamination from the test fluid within the structure. This suggests that the protrusions are formed by the folding of UHMWPE following plastic deformation. It is also suggested that the higher hardness of the protrusions affords some protection of the surface, leading to the observed anomalous behavior, whereby wear increases with decreasing CP. Graphical Abstract

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Section: Discussionsupporting

confidence: 71%

Anomalous Wear Behavior of UHMWPE During Sliding Against CoCrMo Under Varying Cross-Shear and Contact Pressure

et al. 2022

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“…In formula (1), the parameter H is taken as the initial size of the deformable element, and the parameter h its absolute deformation. After transformations, formula (1) is represented in the following form…”

Section: Indentation Size Effect Arising From Vickers Hardness Measur...mentioning

confidence: 99%

“…When using the pyramid in the range of macroindentation the ISE is practically not manifested and hardness testers fix rather stable hardness values. But when the depth of pyramid insertion is reduced to values corresponding to the micro and nanoindentation ranges, the recorded hardness increases significantly [1][2][3][4][5].…”

Section: Introductionmentioning

confidence: 99%

Indentation size effect and hardness of materials

Udalov,

Udalov

2023

E3S Web Conf.

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In recent decades, the Indentation Size Effect (ISE), which manifests itself as a change in fixed hardness depending on indentation conditions, has become one of the most urgent problems of modern materials science. Research efforts are aimed at identifying and eliminating the causes of ISE, because the discrepancy between actual and true hardness values greatly complicates the task of finding the optimal material for the manufacture of parts. The proposed paper gives a brief review of the theories explaining ISE and its relationship with hardness of materials. A more detailed analysis of the effect of ISE on hardness is presented using an energy model based on the determination of the specific work of plastic deformation during indenter indentation. In all cases of ISE manifestation, a proportional relationship was established between the fixed hardness and the specific work of plastic deformation. Thus, the main cause of ISE is the hardening of the material in the centre of deformation under the indenter. The degree of influence of ISE on the fixable hardness as a function of material pre-hardening was determined. At a high level of pre-hardening (at ε>0.25) the influence of the ISE becomes insignificant, so it cannot be of practical importance. The proposed method of hardness determination will allow to assign material for manufacturing of parts to a greater extent corresponding to the operating conditions.

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“…Indentation size effect (ISE) is manifested in a change in the readings of instruments for measuring hardness depending on the deformation conditions of indentation into the sample material. For example, when measuring the hardness with a pyramidal tip with a decrease in the indentation force, the hardness of the material increases [9][10][11][12][13][14]. When measuring hardness with a spherical tip, ISE is more complex and manifests itself when not only the indentation force changes but also the indenter diameter [10,[15][16][17].…”

Section: Introductionmentioning

confidence: 99%

Indentation Size Effect during Measuring the Hardness of Materials by Spherical Indenter

Udalov

Parshin

2020

SSP

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The work balance method was used to study the effect of the indenter diameter on the indentation size effect when measuring Brinell hardness. It is shown that the main criterion for the indentation size effect is the specific work of plastic deformation when an indenter is introduced. The conditions of indentation are established to ensure the smallest deviation of the actual hardness value from the true one. The results of the study can be used in determining the mechanical characteristics of materials and in the practice of metal forming processes.

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On the interpretation of the indentation size effect (ISE) through gradient theory for Vickers and Berkovich indenters

Cited by 7 publications

References 8 publications

Anomalous Wear Behavior of UHMWPE During Sliding Against CoCrMo Under Varying Cross-Shear and Contact Pressure

Anomalous Wear Behavior of UHMWPE During Sliding Against CoCrMo Under Varying Cross-Shear and Contact Pressure

Indentation size effect and hardness of materials

Indentation Size Effect during Measuring the Hardness of Materials by Spherical Indenter

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