iMechanica - rupture
https://imechanica.org/taxonomy/term/7522
enDynamic instabilities of frictional sliding at a bimaterial interface
https://imechanica.org/node/18531
<div class="field field-name-taxonomy-vocabulary-6 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/76">research</a></div></div></div><div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/356">friction</a></div><div class="field-item odd"><a href="/taxonomy/term/744">elastodynamics</a></div><div class="field-item even"><a href="/taxonomy/term/5990">instabilities</a></div><div class="field-item odd"><a href="/taxonomy/term/7522">rupture</a></div><div class="field-item even"><a href="/taxonomy/term/2679">Earthquakes</a></div><div class="field-item odd"><a href="/taxonomy/term/1519">tribology</a></div><div class="field-item even"><a href="/taxonomy/term/706">contact mechanics</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p>Understanding the dynamic stability of bodies in frictional contact steadily sliding one over the other is of basic interest in various disciplines such as physics, solid mechanics, materials science and geophysics. Here we report on a two-dimensional linear stability analysis of a deformable solid of a finite height H, steadily sliding on top of a rigid solid within a generic rate-and-state friction type constitutive framework, fully accounting for elastodynamic effects.</p>
<p>We derive the linear stability spectrum, quantifying the interplay between stabilization related to the frictional constitutive law and destabilization related both to the elastodynamic bi-material coupling between normal stress variations and interfacial slip, and to finite size effects. The stabilizing effects related to the frictional constitutive law include velocity-strengthening friction (i.e.~an increase in frictional resistance with increasing slip velocity, both instantaneous and under steady-state conditions) and a regularized response to normal stress variations.</p>
<p>We first consider the small wave-number k limit and demonstrate that homogeneous sliding in this case is universally unstable, independently of the details of the friction law. This universal instability is mediated by propagating waveguide-like modes, whose fastest growing mode is characterized by a wave-number satisfying k H ~O(1) and by a growth rate that scales with 1/H. We then consider the limit k H>>1 and derive the stability phase diagram in this case.</p>
<p>We show that the dominant instability mode travels at nearly the dilatational wave-speed in the opposite direction to the sliding direction. In a certain parameter range this instability is manifested through unstable modes at all wave-numbers, yet the frictional response is shown to be mathematically well-posed. Instability modes which travel at nearly the shear wave-speed in the sliding direction also exist in some range of physical parameters. Previous results obtained in the quasi-static regime appear relevant only within a narrow region of the parameter space. Finally, we show that a finite-time regularized response to normal stress variations, within the framework of generalized rate-and-state friction models, tends to promote stability.</p>
<p>The relevance of our results to the rupture of bi-material interfaces is briefly discussed.</p>
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</div></div></div>Fri, 03 Jul 2015 06:37:11 +0000Eran Bouchbinder18531 at https://imechanica.orghttps://imechanica.org/node/18531#commentshttps://imechanica.org/crss/node/18531Rupture of a highly stretchable acrylic dielectric elastomer (VHB)
https://imechanica.org/node/12523
<div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/31">fracture</a></div><div class="field-item odd"><a href="/taxonomy/term/85">suo group research</a></div><div class="field-item even"><a href="/taxonomy/term/608">research</a></div><div class="field-item odd"><a href="/taxonomy/term/795">viscoelasticity</a></div><div class="field-item even"><a href="/taxonomy/term/992">dielectric elastomer</a></div><div class="field-item odd"><a href="/taxonomy/term/7032">VHB</a></div><div class="field-item even"><a href="/taxonomy/term/7522">rupture</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p>Dielectric elastomer transducers are often subject to large tensile stretches and are susceptible to rupture. Here we carry out an experimental study of the rupture behavior of membranes of an acrylic dielectric elastomer (VHB 4905). Pure-shear test specimens are used to measure force-displacement curves, using samples with and without pre-cracks. We find that introducing a pre-crack into a membrane drastically reduces the stretch at rupture. Furthermore, we measure the stretch at rupture and fracture energy using samples of different heights at various stretch-rates. The stretch at rupture is found to decrease with sample height, and the fracture energy is found to increase with stretch-rate.<br />
This paper has appeared in the Journal of Applied Physics and can be downloaded from:<br /><a href="http://www.seas.harvard.edu/suo/papers/276.pdf">Rupture of a highly stretchable acrylic dielectric elastomer </a></p>
</div></div></div>Tue, 29 May 2012 14:20:05 +0000Matt Pharr12523 at https://imechanica.orghttps://imechanica.org/node/12523#commentshttps://imechanica.org/crss/node/12523