Sia Nemat-Nasser

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The transition from microto macro-variables of a representative volume element (RVE) of a ®nitely deformed aggregate (e.g., a composite or a polycrystal) is explored. A number of exact fundamental results on averaging techniques, valid at ®nite deformations and rotations of any arbitrary heterogeneous continuum, are obtained. These results depend on the(More)
This paper presents the results of a systematic comparative study of the dynamic thermomechanical response of Ti± 6Al±4V alloys with three di€erent microstructures. Two of the alloys are produced by the hot isostatically pressed technique using rapidly solidi®ed granules, with one alloy milled prior to hot pressing. Experiments are performed over a broad(More)
An ionic polymer-metal composite (IPMC) consisting of a thin perfluorinated ionomer (usually, Nafion or Flemion) strip, platinum, and/or gold plated on both faces and neutralized by a certain amount of appropriate cations undergoes large bending motion when, in a hydrated state, a small electric field is applied across its thickness. When the same membrane(More)
A new class of systems of strongly singular integrodifferential equations is examined, which emerges in the study of the bridged interface crack growth, e.g., in fiber stitched layered composites. This work generalizes the asymptotic analysis of strongly singular integral equations by Willis and Nemat-Nasser [Quart. Appl. Math., 48 (1990), pp. 741–753].(More)
The fracture strength of PMMA is studied using columns with rectangular crosssection that contain a central hole and are subjected to axial compression. Sampleswith geometries such that the width is 2, 3, 4, and 5 times the diameter of the hole are investigated. Cracks are initiated by introducing sharp notches in the axial direction at the crowns of the(More)
To characterize the thermomechanical response, especially the superelastic behavior of NiTi shape-memory alloys (SMAs) at various temperatures and strain rates, we have performed a series of both quasi-static and dynamic uniaxial compression tests on cylindrical samples, using an Instron servohydraulic testing machine and UCSD’s enhanced Hopkinson(More)
The compressive response of a NiTi shape-memory alloy is investigated at high strain rates, using UCSD s modified split Hopkinson pressure bar and a mini-Hopkinson bar with specially designed striker bars. To obtain a constant strain rate during the formation of the stress-induced martensite phase in a Hopkinson test, a copper-tube pulse shaper of suitable(More)
The compressive response of a NiTi shape-memory alloy is investigated at various strain rates using UCSD’s modified 1 2-in. Hopkinson pressure bar and a conventional Instron machine. To obtain a constant strain rate during the formation of a stress-induced martensite in a Hopkinson test, a copper tube of suitable dimensions is employed as a pulse shaper,(More)