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Distribution by Scientific Domains

Polymers and Materials Science	50%

Selected Abstracts

Fatigue of Alumina Under Cyclic Torsion Loading,

ADVANCED ENGINEERING MATERIALS, Issue 7 2009
Thomas Schwind
The work investigates the cyclic fatigue behavior of alumina. It reveals that for cyclic torsion tests the maximum stress criterion is not valid. Cyclic torsion loading leads to a reduced lifetime compared to cyclic tensile-compression. Also an increased cyclic fatigue effect compared to four point bending tests was revealed. [source]

Baryon loading and the Weibel instability in gamma-ray bursts

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2006
M. Fiore
ABSTRACT The dynamics of two counter-streaming electron,positron,ion unmagnetized plasma shells with zero net charge is analysed in the context of magnetic field generation in gamma-ray burst internal shocks due to the Weibel instability. The effects of large thermal motion of plasma particles, arbitrary mixture of plasma species and space charge effects are taken into account. We show that, although thermal effects slow down the instability, baryon loading leads to a non-negligible growth rate even for large temperatures and different shell velocities, thus guaranteeing the robustness and the occurrence of the Weibel instability for a wide range of scenarios. [source]

Creep and recovery behavior of novel organic-inorganic polymer hybrids

POLYMER COMPOSITES, Issue 2 2002
Sunil B. Adalja
A novel class of organic-inorganic polymer hybrids were developed by meltblending up to 50 (v/v) % [about 83 (w/w) %] tin-based polyphosphate glass (Pglass) and low-density polyethylene (LDPE) in conventional plastics processing equipment. The creep and recovery behavior of these polymer hybrids at 30°C were studied to understand the effect of the Pglass on the creep resistance of the LDPE. The results suggest that the Pglass acts as a reinforcement and an increase in the Pglass loading leads to significantly lower creep strains. This creep resistance is further enhanced by pretreating the Pglass with coupling agents prior to incorporating them into the Pglass-LDPE hybrids. The experimental creep compliance of these materials conformed excellently with empirical power-law equation and a modified Burger's model, suggesting that the materials are linearly viscoelastic under the test conditions. [source]

Abfraction: separating fact from fiction

AUSTRALIAN DENTAL JOURNAL, Issue 1 2009
JA Michael
Abstract Non-carious cervical lesions involve loss of hard tissue and, in some instances, restorative material at the cervical third of the crown and subjacent root surface, through processes unrelated to caries. These non-carious processes may include abrasion, corrosion and possibly abfraction, acting alone or in combination. Abfraction is thought to take place when excessive cyclic, non-axial tooth loading leads to cusp flexure and stress concentration in the vulnerable cervical region of teeth. Such stress is then believed to directly or indirectly contribute to the loss of cervical tooth substance. This article critically reviews the literature for and against the concept of abfraction. Although there is theoretical evidence in support of abfraction, predominantly from finite element analysis studies, caution is advised when interpreting results of these studies because of their limitations. In fact, there is only a small amount of experimental evidence for abfraction. Clinical studies have shown associations between abfraction lesions, bruxism and occlusal factors, such as premature contacts and wear facets, but these investigations do not confirm causal relationships. Importantly, abfraction lesions have not been reported in pre-contemporary populations. It is important that oral health professionals understand that abfraction is still a theoretical concept, as it is not backed up by appropriate clinical evidence. It is recommended that destructive, irreversible treatments aimed at treating so-called abfraction lesions, such as occlusal adjustment, be avoided. [source]