scholarly journals Indentation Depth Dependent Mechanical Behavior in Polymers

2015 ◽  
Vol 2015 ◽  
pp. 1-20 ◽  
Author(s):  
Farid Alisafaei ◽  
Chung-Souk Han
Keyword(s):  
Size Effect ◽  
Mechanical Behavior ◽  
Size Effects ◽  
Indentation Depth ◽  
Common Ground ◽  
Experimental Studies ◽  
Experimental Methods ◽  
Indentation Size ◽  
Size Dependent ◽  
Nanoindentation Testing

Various experimental studies have revealed size dependent deformation of materials at micro and submicron length scales. Among different experimental methods, nanoindentation testing is arguably the most commonly applied method of studying size effect in various materials where increases in the hardness with decreasing indentation depth are usually related to indentation size effects. Such indentation size effects have been observed in both metals and polymers. While the indentation size effects in metals are widely discussed in the literature and are commonly attributed to geometrically necessary dislocations, for polymer the experimental results are far sparser and there does not seem to be a common ground for their rationales. The indentation size effects of polymers are addressed in this paper, where their depth dependent deformation is reviewed along with the rationale provided in the literature.

Indentation Depth Dependent Hardness in Polydimethylsiloxane

2011 ◽  
Author(s):  
Chung-Souk Han ◽  
Andrew J. Wrucke ◽  
Partha Majumdar
Keyword(s):  
Experimental Data ◽  
Size Effects ◽  
Indentation Depth ◽  
Berkovich Indenter ◽  
Indentation Size ◽  
Size Dependent

Size dependent deformation in polymers has been observed in various experiments including microbeam bending, foams, composites and indentation. For indentation depths from 100 microns down to hundreds of nanometers strong increases in the hardness has been observed where the hardness has been determined with a Berkovich indenter tip on polydimethylsiloxane. These observations are related to other existing experimental data of the literature and possible rationales for these indentation size effects are discussed.

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.

Indentation Size Effect on Hardness of Nanostructured Thin Films

2006 ◽  
Vol 312 ◽  
pp. 363-368 ◽  
Author(s):  
Chun Sheng Lu ◽  
Yiu Wing Mai ◽  
Yao Gen Shen
Keyword(s):  
Thin Films ◽  
Plastic Deformation ◽  
Grain Boundary ◽  
Size Effect ◽  
Indentation Depth ◽  
Indentation Size Effect ◽  
Indentation Size ◽  
Nanostructured Thin Films ◽  
Measured Hardness

Based on nanoindentation techniques, the evaluation of hardness of two nanostructured thin films, AlN and Ti-Al-N, is discussed. In the case of AlN films, the indentation size effect of hardness can be modeled using the concept of geometrically necessary dislocations, whereas in the case of Ti-Al-N films, the measured hardness increases exponentially as the indentation depth decreases. The results show that, as thin films approach superhard, dislocation-based plastic deformation is gradually replaced by grain-boundary mediated deformation.

Analysis of Load-Displacement Curves of Ceramics Measured with Low-Load Vickers Hardness Test: Indentation Size Effect

2011 ◽  
Vol 492 ◽  
pp. 9-13
Author(s):  
Bei Xu ◽  
Jiang Hong Gong
Keyword(s):  
Size Effect ◽  
Vickers Hardness ◽  
Indentation Size Effect ◽  
Hardness Test ◽  
Hardness Testing ◽  
Indentation Size ◽  
Nanoindentation Testing ◽  
Low Load ◽  
Load Displacement ◽  
Vickers Hardness Test

The load-displacement curves for a series of ceramic and glass samples were recorded continuously during the low-load Vickers hardness testing. Then the hardnesses of all samples were determined by analyzing the unloading curves. It was found that all the test materials exhibit indentation size effect (ISE) similar to that observed in nanoindentation testing. The applicability of the proportional specimen resistance (PSR) model and the modified PSR model was then examined using the measured indentation data.

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.

scholarly journals Indentation Size Effect in Pressure-Sensitive Polymer Based on A Criterion for Description of Yield Differential Effects and Shear Transformation-Mediated Plasticity

Polymers ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 412 ◽  
Author(s):  
Hui Lin ◽  
Tao Jin ◽  
Lin Lv ◽  
Qinglin Ai
Keyword(s):  
Size Effects ◽  
Indentation Depth ◽  
Yield Criterion ◽  
Strain Rates ◽  
Depth Range ◽  
Pressure Sensitivity ◽  
Indentation Size ◽  
Strength Differential ◽  
Two Factors ◽  
Shear Transformation

Indentation size effects in poly(methyl methacrylate) (PMMA) were studied through nanoindentation. Two factors of indentation size effects in PMMA, namely yield criterion and shear transformation-mediated plasticity, were analysed in detail. The yield criterion that considers strength differential (SD) effects and pressure sensitivity was constructed by performing the combined shear-compression experiments. The relationship between hardness and normal stress can then be obtained based on Tabot’s relation. Shear transformation-mediated plasticity was also applied to model the measured hardness as a function of the indentation depth at different strain rates. Results show that the yield criterion contains the terms of SD effects and pressure sensitivity gives the best description of the yielding of PMMA. Additionally, the volume of single shear transformation zone calculated through the presented criterion agrees well with simulation and exhibits increases with increasing strain rate. Indentation size effects in PMMA under different strain rates were discussed and an appropriate indentation depth range was suggested for calculating the hardness and modulus.

An Investigation of Film Thickness Effect on Mechanical Properties of Au Films Using Nanoindentation Techniques

2005 ◽  
Vol 875 ◽  
Author(s):  
Yifang Cao ◽  
Zong Zong ◽  
Wole Soboyejo
Keyword(s):  
Thin Films ◽  
Mechanical Properties ◽  
Electron Beam ◽  
Film Thickness ◽  
Size Effects ◽  
Experimental Studies ◽  
Thickness Effect ◽  
Length Scale ◽  
Indentation Size ◽  
Au Thin Films

AbstractThis paper presents the results of nanoindentation experimental studies of Au thin films with different thicknesses. The effects of film thickness and microstructure on the hardnesses of electron-beam deposited Au films were studied in terms of Hall-Petch relationship. The effects of different thicknesses on indentation size effects (ISE) are explained within the framework of mechanism-based strain gradient (MSG) theory using the concept of microstructural length scale.

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 Size-Dependent Dynamic Behavior of a Microcantilever Plate

2012 ◽  
Vol 2012 ◽  
pp. 1-5 ◽  
Author(s):  
Xiaoming Wang ◽  
Fei Wang
Keyword(s):  
Size Effect ◽  
Dynamic Behavior ◽  
Size Effects ◽  
Numerical Solutions ◽  
Couple Stress Theory ◽  
Differential Quadrature Method ◽  
Modified Couple Stress Theory ◽  
Cantilever Plate ◽  
Size Dependent ◽  
Material Length Scale

Material length scale considerably affects the mechanical properties of microcantilever components. Recently, cantilever-plate-like structures have been commonly used, whereas the lack of studies on their size effects constrains the design, testing, and application of these structures. We have studied the size-dependent dynamic behavior of a cantilever plate based on a modified couple stress theory and the differential quadrature method in this note. The numerical solutions of microcantilever plate equation involving the size effect have been presented. We have also analyzed the bending and vibration of the microcantilever plates considering the size effect and discussed the dependence of the size effect on their geometric dimensions. The results have shown that (1) the mechanical characteristics of the cantilever plate show obvious size effects; as a result, the bending deflection of a microcantilever plate reduces whereas the natural frequency increases effectively and (2) for the plates with the same material, the size effect becomes more obvious when the plates are thinner.

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.

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