Indentation of freestanding circular elastomer films using spherical indenters

Scott, Orion N.; Begley, Matthew R.; Komaragiri, Uday; Mackin, Thomas J.

doi:10.1016/j.actamat.2004.06.043

Cited by 71 publications

(58 citation statements)

References 13 publications

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“…5, where it can be seen that the model provides a realistic prediction of the load-deflection behaviour. Both the experiment and model display a J-shaped load deflection response, which is a characteristic of indenting soft materials [2,3,8,15,21,22,27]. However, the experiment is slightly less stiff than the model, which is most likely due to some slipping of the substrate in the grips (note:…”

Section: Fe Model Validationmentioning

confidence: 94%

On the sharpness of straight edge blades in cutting soft solids: Part II – Analysis of blade geometry

McCarthy

Annaidh

Gilchrist

2010

Engineering Fracture Mechanics

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In Part I of this paper a new metric, titled the "Blade Sharpness Index" or "BSI", for quantifying the sharpness of a straight edge blade when cutting soft solids was derived from first principles and verified experimentally by carrying out indentation type cutting tests with different blades types cutting different target or substrate materials. In this Part II companion paper, a finite element model is constructed to examine the effect of different blade variables including tip radius, wedge angle and blade profile on the BSI developed in Part I. The finite element model is constructed using ABAQUS implicit and experiments are performed to characterise the non-linear material behaviour observed in the elastomeric substrate. The model is validated against the experiments performed in Part I and a suitable failure criterion is determined by carrying out experiments on blades with different tip radii. The paper finds that a simple maximum stress criterion is a good indicator for predicting the onset of cutting.The validated model is then used to examine blade geometry. It is shown that finite element analysis is an important tool in helping to understand the mechanics of indentation.Furthermore, the study finds that all the blade geometric variables have an influence on the

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Section: Fe Model Validationmentioning

confidence: 94%

On the sharpness of straight edge blades in cutting soft solids: Part II – Analysis of blade geometry

McCarthy

Annaidh

Gilchrist

2010

Engineering Fracture Mechanics

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“…30,41 In addition, type I collagen hydrogels were used since type I collagen is the principal fibrous protein of the cornea and through compression can be reproducibly fabricated to generate a thin, homogeneous, dense collagen fiber structure similar to the cornea that was thin enough to facilitate NLO CXL throughout the corneal phantom. Since collagen organization in collagen hydrogels is random, tissue-indentation testing was used to measure the stiffening of collagen regardless of orientation.…”

Section: Discussionmentioning

confidence: 99%

Nonlinear optical collagen cross-linking and mechanical stiffening: a possible photodynamic therapeutic approach to treating corneal ectasia

et al. 2013

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Abstract. In this study we test the hypothesis that nonlinear optical (NLO) multiphoton photoactivation of riboflavin using a focused femtosecond (FS) laser light can be used to induce cross-linking (CXL) and mechanically stiffen collagen as a potential clinical therapy for the treatment of keratoconus and corneal ectasia. Riboflavin-soaked, compressed collagen hydrogels are cross-linked using a FS laser tuned to 760 nm and set to either 100 mW (NLO CXL I) or 150 mW (NLO CXL II) of laser power. FS pulses are focused into the hydrogel using a 0.75 NA objective lens, and the hydrogel is three-dimensionally scanned. Measurement of hydrogel stiffness by indentation testing show that the calculated elastic modulus (E) values are significantly increased over twofold following NLO CXL I and II compared with baseline values (P < 0.05). Additionally, no significant differences are detected between NLO CXL and single photon, UVA CXL (P > 0.05). This data suggests that NLO CXL has a comparable effect to conventional UVA CXL in mechanically stiffening collagen and may provide a safe and effective approach to localize CXL at different regions and depths within the cornea. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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“…Thus, r/a y 0.31 for the graphene membrane considered in Fig. 7 (a y 80 nm), and the sphere load model 29,30 applies. Substituting d ¼ 7.5 nm in eqn (1) and neglecting the pre-tension, we obtain a force of F ¼ 15 nN.…”

Section: Graphene Suspended On Gold Nanovoidsmentioning

confidence: 99%

Determination of the STM tip-graphene repulsive forces by comparative STM and AFM measurements on suspended graphene

et al. 2016

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Graphene grown by chemical vapour deposition is transferred on top of flat gold nanoislands and characterized by scanning tunnelling microscopy (STM) and atomic force microscopy (AFM). Graphene bubbles are formed with lateral dimensions determined by the size and shape of nanoislands. These graphene bubbles can be squeezed during STM imaging using bias voltages of less than 250 mV and tunnelling currents of 1 nA. Similarly, the graphene suspended over gold nanovoids is deflected 4-5 nm by the STM tip when imaging at low bias voltages (U ¼ 30 mV). Nanoindentation measurements performed by AFM show that the squeezing of graphene bubbles occurs at repulsive forces of 20-35 nN, and such forces can result in deflections of several nanometres in suspended graphene parts, respectively. Comparing the AFM and STM results, this study reveals that mechanical forces of the order of 10 À8 N occur between the STM tip and graphene under ambient imaging conditions and typical tunnelling parameters.

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Indentation of freestanding circular elastomer films using spherical indenters

Cited by 71 publications

References 13 publications

On the sharpness of straight edge blades in cutting soft solids: Part II – Analysis of blade geometry

On the sharpness of straight edge blades in cutting soft solids: Part II – Analysis of blade geometry

Nonlinear optical collagen cross-linking and mechanical stiffening: a possible photodynamic therapeutic approach to treating corneal ectasia

Determination of the STM tip-graphene repulsive forces by comparative STM and AFM measurements on suspended graphene

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