Strain gradient plasticity effect in indentation hardness of polymers

Chong, Arthur C.M.; Lam, David Chuen Chun

doi:10.1557/jmr.1999.0554

Cited by 332 publications

(132 citation statements)

References 7 publications

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“…Such elevated hardnesses at small indentation depths have also been observed in polymers [Briscoe et al 1998;Chong and Lam 1999;Tjernlund et al 2004;Lim and Chaudhri 2006; but, in comparison to metals, for polymers these effects are not well understood. An understanding of size-dependent deformation behavior is important not only for small components in MEMS/NEMS (micro/nano-electromechanical systems), but also for the development of advanced material systems and composite materials with small material phases and other applications such as sealants, gaskets [Tan et al 2007], and adhesives [Han et al 2007b].…”

Section: Introductionmentioning

confidence: 90%

Rate dependence of indentation size effects in filled silicone rubber

Tatiraju

Han

2010

JOMMS

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Indentation experiments at the nanometer and micrometer range reported in the literature have shown that the deformation of polymers is -similarly to metals -size-dependent. In addition its size dependence, the deformation behavior of polymers is also known to be rate-dependent. Here silicone rubber is considered. In order to characterize the relation between size and rate-dependent deformation indentation tests of silicone at indentation depths of between 30 and 300 microns and loading times of between 1 and 1000 seconds are performed. In these experiments the hardness and dissipation increased with decreasing loading time and decreasing indentation depth. These experimental results are analyzed with a recently suggested indentation model which incorporates a Frank energy-related nonlocal deformation work. It is found that the indentation model is in good agreement with the experimental data. Evaluation of the experimental data indicates that the rate effects are mostly related to the nonlocal, size-dependent deformation.

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Section: Introductionmentioning

confidence: 90%

Rate dependence of indentation size effects in filled silicone rubber

Tatiraju

Han

2010

JOMMS

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“…Other measurements evaluate the material length scale parameter of single crystal and polycrystalline copper to be 12 and 5.84 μm, respectively (McElhaney et al, 1998;Nix and Gao, 1998). Also, the size-dependent behavior has been detected in some kinds of polymers (Chong and Lam, 1999). For hardness measurement of bulk gold, it is found that the plastic length scale parameter (for indentation test and hardness behavior) of Au increases from 470 nm to 1.05 μm with increasing the Au film thickness from 500 nm to 2 μm (Cao et al, 2007).…”

Section: Using Various Approachesmentioning

confidence: 99%

Modeling the size dependent pull-in instability of beam-type NEMS using strain gradient theory

Koochi

Sedighi

Abadyan

2014

Lat. Am. j. solids struct.

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It is well recognized that size dependency of materials characteristics, i.e. size-effect, often plays a significant role in the performance of nano-structures. Herein, strain gradient continuum theory is employed to investigate the size dependent pull-in instability of beam-type nano-electromechanical systems (NEMS). Two most common types of NEMS i.e. nano-bridge and nano-cantilever are considered. Effects of electrostatic field and dispersion forces i.e. Casimir and van der Waals (vdW) attractions have been considered in the nonlinear governing equations of the systems. Two different solution methods including numerical and Rayleigh-Ritz have been employed to solve the constitutive differential equations of the system. Effect of dispersion forces, the size dependency and the importance of coupling between them on the instability performance are discussed.

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“…The experiments conducted on the microstructures subjected to different loading conditions have revealed their size-dependent behavior (Nix 1989;Fleck et al 1994;Ma and Clarke 1995;Vardoulakis et al 1998;Stolken and Evans 1998;Chong and Lam 1999;Lam et al 2003;and Colton 2005). When the dimensions of a structure are on the order of microns or submicrons, it R. Ansari is necessary to consider internal material length scale parameters in order to predict its mechanical behavior.…”

Section: Introductionmentioning

confidence: 99%

Size-Dependent Bending, Buckling and Free Vibration Analyses of Microscale Functionally Graded Mindlin Plates Based on the Strain Gradient Elasticity Theory

Ansari

Hasrati

Shojaei

et al. 2016

Lat. Am. j. solids struct.

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In this paper, a size-dependent microscale plate model is developed to describe the bending, buckling and free vibration behaviors of microplates made of functionally graded materials (FGMs). The size effects are captured based on the modified strain gradient theory (MSGT), and the formulation of the paper is on the basis of Mindlin plate theory. The presented model accommodates the models based upon the classical theory (CT) and the modified couple stress theory (MCST) if all or two scale parameters are set to zero, respectively. By using Hamilton's principle, the governing equations and related boundary conditions are derived. The bending, buckling and free vibration problems are considered and are solved through the generalized differential quadrature (GDQ) method. A detailed parametric and comparative study is conducted to evaluate the effects of length scale parameter, material gradient index and aspect ratio predicted by the CT, MCST and MSGT on the deflection, critical buckling load and first natural frequency of the microplate. The numerical results indicate that the model developed herein is significantly sizedependent when the thickness of the microplate is on the order of the material scale parameters.

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Strain gradient plasticity effect in indentation hardness of polymers

Cited by 332 publications

References 7 publications

Rate dependence of indentation size effects in filled silicone rubber

Rate dependence of indentation size effects in filled silicone rubber

Modeling the size dependent pull-in instability of beam-type NEMS using strain gradient theory

Size-Dependent Bending, Buckling and Free Vibration Analyses of Microscale Functionally Graded Mindlin Plates Based on the Strain Gradient Elasticity Theory

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