Indentation of a power law creeping solid

Bower, Allan F.; Fleck, N.A.; Needleman, A.; Ogbonna, Nkem

doi:10.1098/rspa.1993.0050

Cited by 259 publications

(115 citation statements)

References 18 publications

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“…Using this technique, they could show an enhanced SRS of NC ZnO 12 and NC-TiO 2 . 13 A more general theoretical work on dynamic nanoindentation was given by Bower et al, 14 who used finite element modeling (FEM) to describe indentations in power law creeping solids. They showed that Mulhearn and Tabor's 15 concept on effective stress and effective strain rate generally applies to power law creeping solids.…”

Section: Introductionmentioning

confidence: 99%

Nanoindentation strain-rate jump tests for determining the local strain-rate sensitivity in nanocrystalline Ni and ultrafine-grained Al

et al. 2011

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A nanoindentation strain-rate jump technique has been developed for determining the local strainrate sensitivity (SRS) of nanocrystalline and ultrafine-grained (UFG) materials. The results of the new method are compared to conventional constant strain-rate nanoindentation experiments, macroscopic compression tests, and finite element modeling (FEM) simulations. The FEM simulations showed that nanoindentation tests should yield a similar SRS as uniaxial testing and generally a good agreement is found between nanoindentation strain-rate jump experiments and compression tests. However, a higher SRS is found in constant indentation strain-rate tests, which could be caused by the long indentation times required for tests at low indentation strain rates. The nanoindentation strain-rate jump technique thus offers the possibility to use single indentations for determining the SRS at low strain rates with strongly reduced testing times. For UFG-Al, extremely fine-grained regions around a bond layer exhibit a substantial higher SRS than bulk material.

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Section: Introductionmentioning

confidence: 99%

Nanoindentation strain-rate jump tests for determining the local strain-rate sensitivity in nanocrystalline Ni and ultrafine-grained Al

et al. 2011

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“…On the abrupt application of the load, the penetration almost instantaneously reaches a certain value, which is attributable to the elastic response of the material. This is followed by a second stage with an approximately linear relation between penetration and elapsed time--this regime can be directly correlated with the steady-state creep response of the gel (18). Now consider each of the three cases shown in Fig.…”

Section: Increases In Penetration Rate Are a Results Of Fsi Effects Ramentioning

confidence: 99%

Unsteady penetration of a target by a liquid jet

Uth

Deshpande

2013

Proc. Natl. Acad. Sci. U.S.A.

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It is widely acknowledged that ceramic armor experiences an unsteady penetration response: an impacting projectile may erode on the surface of a ceramic target without substantial penetration for a significant amount of time and then suddenly start to penetrate the target. Although known for more than four decades, this phenomenon, commonly referred to as dwell, remains largely unexplained. Here, we use scaled analog experiments with a low-speed water jet and a soft, translucent target material to investigate dwell. The transient target response, in terms of depth of penetration and impact force, is captured using a high-speed camera in combination with a piezoelectric force sensor. We observe the phenomenon of dwell using a soft (noncracking) target material. The results show that the penetration rate increases when the flow of the impacting water jet is reversed due to the deformation of the jet-target interface--this reversal is also associated with an increase in the force exerted by the jet on the target. Creep penetration experiments with a constant indentation force did not show an increase in the penetration rate, confirming that flow reversal is the cause of the unsteady penetration rate. Our results suggest that dwell can occur in a ductile noncracking target due to flow reversal. This phenomenon of flow reversal is rather widespread and present in a wide range of impact situations, including water-jet cutting, needleless injection, and deposit removal via a fluid jet.impact loading | ballistic penetration | fluid-structure interaction | interface defeat C eramic materials, although having a reputation for being inherently brittle, have been used for different armor systems for almost a century. The application of ceramic-based armor ranges from protection of aircraft and personnel against smallcaliber threats, to vehicle armor designed to defeat long-rod penetrators and shaped charges.Here, we consider thick, well-confined ceramic armor systems designed to withstand the high-velocity impact of heavy-metal longrod penetrators. Such systems are extensively used to study the dynamic penetration properties of ceramics over relatively long time frames: the confinement prevents/reduces the macroscopic cracking of the ceramic target and thus provides a more controlled experimental setting where statistical effects of cracking are minimized.The time-resolved penetration behavior of ceramic armor has been extensively studied over the past 45 y using flash radiography, a technique used for impact experiments involving optically opaque targets (1-4). As sketched in Fig.

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“…Reduction of the creep problem in indentation to a nonlinear elasticity problem has been discussed by Bower et al (1993). For self-similar indenters the problem can be further simplified by observing that h andḣ are the only measures of length and velocity respectively.…”

Section: Similarity and Reduction To A Non-linear Elasticity Problemmentioning

confidence: 99%

“…An important feature is that in many cases the creep problem can be reduced to the solution of a static nonlinear elasticity problem. The problem of indentation is one of such cases (Bower et al [20]). …”

Section: Introductionmentioning

confidence: 99%

Indentation of power law creep solids by self-similar indenters

Chen

Cheng

2010

Materials Science and Engineering: A

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a b s t r a c tFor creep solids obeying the power law under tension proposed by Tabor, namely = bε m , it has been established through dimensional analysis that for self-similar indenters the load F versus indentation depth h can be expressed ashere the dimensionless factor˘˛depends on material parameters such as m and the indenter geometry. In this article, we show that by generalizing the Tabor power law to the general three dimensional case on the basis of isotropy, this factor can be calculated so that indentation test can be used to determine the material parameters b and m appearing in the original power law. Hence indentation test can replace tension test. This could be a distinct advantage for materials that come in the form of thin films, coatings or otherwise available only in small amounts. To facilitate application values of this constant are given in tabulated form for a range of material parameters.

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Indentation of a power law creeping solid

Cited by 259 publications

References 18 publications

Nanoindentation strain-rate jump tests for determining the local strain-rate sensitivity in nanocrystalline Ni and ultrafine-grained Al

Nanoindentation strain-rate jump tests for determining the local strain-rate sensitivity in nanocrystalline Ni and ultrafine-grained Al

Unsteady penetration of a target by a liquid jet

Indentation of power law creep solids by self-similar indenters

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