Crack propagation during fatigue experiments

In the present paper a very simple phenomenological theory of crack propagation during fatigue experiments is presented. It is shown that an important role is played by work-hardening to explain both the existence of a fatigue limit and the well known deviations from Miner's Rule in the case of tests conducted at varying maximum applied stresses. Although approximate, the theory can account for the main phenomena involved in fatigue experiments.

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Zusammenfassung Es wird eine sehr einfache Grundlagentheorie zur Beschreibung der Fortpflanzungsbedingungen eines Risses unter Dauerbeanspruchung dargelegt.Die Grundlage dieser Theorie besteht darin die Rissfortpflanzung mit der mechanischen Hysteresis in Zusammenhang zu bringen.Es wird auf die wichtige Rolle der Verformung hingewiesen, sowohl für der Begriff der Dauerfestigkeit als auch für die wohlbekannten Abweichungen von dem Miner Gesetz, im falle von Versuchen bei maximaler Beanspruchung mit veränderlichen Amplituden.Trotz einer Anzahl von Vereinfachungen, gibt these Theorie eine gute Beschreibung der wichtigsten Vorgänge beim Dauerversuch.

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Résumé On présente une théorie phénoménologique extrêmement simple pour décrire les conditions de propagation des fissures en fatigue. Cette théorie repose sur le principe d'associer la propagation des fissures an cycle d'hystérésis mécanique. On montre que l'écrouissage joue un rôle important, à la fois dans la notion de la limite d'endurance, et dans les inexactitudes, bien connues, de la règle de Miner, lorsque des essais sent conduits à des contraintes maximales d'amplitude variable.Quoique assez grossière, cette théorie rend compte des principaux phénomènes qui interviennent dans des expériences de fatique.

     

Planar Translational Cable‐Direct‐Driven Robots

We present the simulated dynamics and control of a planar, translational cable‐directdriven robot (CDDR). The motivation behind this work is to improve the serious cable interference problem with existing CDDRs and to avoid configurations where negative cable tensions are required to exert general forces and moments on the environment and during dynamic motions. Generally for CDDRs the commanded rotations are more demanding than commanded translations in terms of slack cable conditions. Therefore we propose a translational CDDR whose end‐effector may be fitted with a traditional serial wrist mechanism to provide rotational freedom (assuming proper design to resist the moments). Only the translational CDDR is considered in this article, including kinematics and statics modeling, statics workspace (wherein all possible Cartesian forces and moments may be exerted with only positive cable tensions), plus a dynamics model and simulated control for planar CDDRs. Here we focus only on planar CDDRs, to clearly demonstrate our dynamics and control work; we will extend this work to spatial CDDRs in the future. Examples are presented to demonstrate simulated control including feedback linearization of the four‐cable CDDR (with one degree of actuation redundancy) performing a Cartesian task. An on‐line dynamic minimum torque estimation algorithm is introduced to ensure all cable tensions remain positive for all motion; otherwise slack cables can result from CDDR dynamics and control is lost. © 2003 Wiley Periodicals, Inc.     

Application of cone calorimeter for the assessment of class of flame retardants for polypropylene

The study presented addresses the fire behaviour of polypropylene compounded with six classes of flame retardants. The application of cone calorimetry for the assessment of the thermal characteristics of the tested materials and their comparison with thermogravimetry are the central point of this research. This study only presents data for 25 kW/m² of incident heat flux exposure and includes five tests for polypropylene with no additives and five tests for polypropylene with flame retardants based on triglycidylisocyanurate and lignin. The data collected include the rate of heat release, mass loss rate, char yield, time to ignition and time of total combustion. Results represent meaningful comparison between the behaviour of the materials under simulated fire conditions, using the cone calorimeter, and in the slow dynamic environment utilized in thermogravimetric analysis. © 1998 John Wiley & Sons Ltd.     

Dimensions of emotionality in a rat model of innate anxiety.

Emotionality is thought to be multidimensional, with "anxiety" representing one dimension. Dissecting emotional dimensions in animal models is an essential prerequisite for investigating the neurobiological mechanisms that underlie anxiety. The authors used factor analysis to investigate emotional dimensions in normal rats and rats bred for either high or low anxiety-related behavior. Hyperanxious rats were reduced in emotional dimensions in the elevated plus-maze by selection pressure, and a modified hole board test revealed a dissection of their emotionality with precisely defined dimensions. This enabled clear differentiation of "anxiety" from other emotional dimensions including risk assessment behavior and exploration. Factors extracted by analyzing data from a multiple-test battery correspond to particular test characteristics rather than to emotional dimensions. The approach used might help to develop specific treatment strategies for anxiety disorders. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Application of partial least square regression to differential scanning calorimetry data for fatty acid quantitation in olive oil

A chemometric approach based on partial least (PLS) square methodology was applied to unfolded differential scanning calorimetry data obtained by 63 samples of different vegetable oils (58 extra virgin olive oils, one olive and one pomace olive oil, three seed oils) to evaluate fatty acid composition (palmitic, stearic, oleic and linoleic acids, saturated (SFA), mono (MUFA) and polysaturated (PUFA) percentages, oleic/linoleic and unsaturated/saturated ratios).     

Effect of nisin‐producing Lactococcus lactis starter cultures on the inhibition of two pathogens in ripened cheeses

The effect of Lactococcus lactis nisin‐producing strains, isolated from Italian fermented foods, on the survival of two foodborne pathogens namely Listeria monocytogenes and Staphylococcus aureus was investigated in experimental cheese production. One of the three Lactobacillus lactis nisin innoculated as starters, Lactobacillus lactis 41FL1 lowered S. aureus count by 1.73 log colony‐forming units (cfu)/g within the first 3 days, reaching the highest reduction, 3.54 log cfu/g, by the end of ripening period of 60 days. There was no effect on L. monocytogenes. The application of L. lactis 41FL1 as bioprotective culture in controlling S. aureus shows considerable promise.     

A capacitive technique to assess water content in extra virgin olive oils

The present research investigated the correlations between capacitance and water content of extra virgin olive oils (EVOO). A commercial capacitor probe for radio applications and an LCR meter were used for electric tests in the frequency range from 500 Hz to 512 kHz. Seventeen samples of different EVOO with a moisture content ranging from 178 to 1321 mg/kg oil were selected for study. To assess the influence of moisture only, the oil with the maximum water content was filtered down to 288 mg/kg oil and five samples with intermediate water contents were prepared and submitted to electrical measurements. Subsequently, the capacitance of all 17 EVOO samples was measured at selected frequencies.