Transducteur-tension-fréquence pour systèmes de puissance à 60 hz

Transducteur de tension -- Principe de fonctionnement -- Critères de réalisation -- Atténuateur et redresseur -- Détecteur de maximum -- Échantillonnage -- Bloqueur d'ordre zéro -- Remise à zéro -- Transducteur de fréquence -- Paramètres de l'approximation -- Discussion -- Bilan des caractéristiques du transducteur tension-fréquence -- mesure en tension -- Mesure en fréquence

Investigation of Re-Crystallization of Injection Molded TPO Unpainted Plaques

Peer reviewed: YesNRC publication: Ye

Injection molding and properties of highly filled copper-polyamide 11 composites

Copper-polyamide-I1 composites containing up to 90 wt.% of spherical copper powder were made using three approaches: (1) conventional injection molding of dry copper-polyamide powder blends, (2) compounding of powder blends and subsequent injection molding of composite pellets, and (3) direct molding of powder blends on an injection machine equipped with a vacuum hopper. The conventional molding of powders results in products having a significant porosity, which originates from the air dragged into the machine with the powder. The other two approaches can be used to produce essentially void-free materials. The mechanical properties are affected by the state of the filler surface. The "as-atomized" copper (which has a rough surface covered with an oxide layer) adheres better to the polymer than that whose surface was reduced to pure metal by hydrogen. </jats:p

Rheological properties of long glass fibre filled polypropylene

International audienceLong glass fiber-filled polypropylene (PP) composites are produced by pultrusion, and the extrudate is cut at different lengths producing composites containing long fibers of controlled length. The rheological properties of such composites in the molten state have been studied using different rheometers. A capillary rheometer has been constructed and mounted on a molding-injection machine. The shear viscosity of filled PP determined from the capillary rheometer, after corrections for entrance effects, was found to be very close to that of unfilled PP. However, large excess pressure losses at the capillary entrance were observed and these data have been used to obtain an apparent elongational viscosity. The apparent elongational viscosity was shown to be considerably larger than the shear viscosity for PP and filled PP, and it increased markedly with fiber length and fiber content. Rotational rheometers with a parallel-plate geometry were used to investigate the viscoelastic properties of these composites and their behavior was found to be non-linear, exhibiting a yield stress. A model is proposed to describe the shear viscosity from a solid-like behavior at low stresses to fluid-like behavior at high shear stresses taking into account fiber content and orientation. A modified model, proposed for elongational flow, describes relatively well the apparent elongational data