No abstract

Reinforced polymer-matrix composites are widely used under sliding contact conditions in various boating and automotive applications. In this paper, the friction and wear of bulk epoxy and carbon filler reinforced epoxy composites have been investigated using a pin-on-disc tribometer. The effect of different fillers on the tribological behavior of an epoxy has been studied using treated and untreated carbon nanotubes, graphite, and a mixture of graphite and carbon nanotubes. Filler addition greatly enhances the tribological properties of the epoxy resin, by reducing the friction coefficient and the wear rate. In addition, it was found that the treated carbon nanotubes/epoxy composites have the best tribological behavior. Moreover, a correlation between contact temperature and friction coefficient is reported. Finally, the wear mechanisms were determined by scanning electronic microscopy.

Sheet metal bending processes are some of the most commonly used industrial manufacturing operations. The development and optimization of these processes are time consuming and costly. Therefore, finite element simulations may aid the design and quality assurance of sheet metal products. In the present study, a commercial finite element package was used to analyze the three-roller bending of a steel sheet. A two-dimensional finite element model of this process was built under the ABAQUS/Explicit environment based on the solution of several key techniques, such as contact boundary condition treatment, material property definition, meshing technique, and so on. Maps with desired curvature radii were established by varying the distance between the two bottom rollers and the position of the upper one. The developed maps made the rolling process easier and less time consuming. An industrial experiment using optimized numerical results was carried out to validate the numerical model. Residual stress and equivalent plastic strain distributions were also studied. The numerical spring back phenomenon was compared with analytical results.

A nanocrystallized surface layer of around 150 µm thickness was created on AISI 304L by nano-scale surface peening. Electron back scattered diffraction (EBSD) has revealed that the upper layer of the nanocrystallized surface was formed by nanosized ferrite grains. However, bottom layer was compounded from martensite and deformed austenite. Tribocorrosion behavior of the nanocrystallized surface against alumina was investigated in a mixture of olive pomace and tap water filtrate. Nanopeened 304L was more sensitive to tribocorrosion under intermittent sliding than continuous one due to depassivation/repassivation phenomena. Mechanical and corrosion wear components were quantified. Tribocorrosion mechanism was dominated by abrasion mechanical removal of the uncovered surface. The wear resistance of AISI 304L surface was markedly improved by treatment. That improvement could be explained by the higher hardness of nanocrystallized AISI 304L.

Usual plate solar collectors, based on a metal absorber (Cu, Al) selectively coated are technologically very sophisticated, expensive to produce and they are great consumer of fossil raw material. Polymeric materials are considered as a promising alternative for many interesting properties; easy moldability, corrosion resistance, they also offer a significant cost-reduction for solar thermal collectors, and a mass production may thus benefit to a broader utilization of solar energy. Most drawbacks of polymers are their low thermal properties; essentially thermal conductivity coefficient may strongly affect the solar absorber efficiency and deteriorate the collector performance. Polymers used in solar collectors are mainly petroleum-derivative product and mass use of them is not a response to environmental concern. That is why the laboratory chose to explore the potentialities of bio-polymers for the production of absorbers. This group of material presents the same properties as ordinary polymers. It is on the other hand possible to modify the thermal properties of the basic matrix by the addition of loads, such as carbon black, graphite or carbon nanotubes. The thermal performance of a solar collector is closely related to the thermal properties of the absorber. Within this framework, many measurements are necessary, more particularly the conductivity, but also emissivity and absorptivity to solar radiation. The aim of this paper is to study the thermal properties of the PLA bio-polymer charged of exfoliated graphite and/or CNT. Thereafter, the total hemispherical absorptivity, an estimation of the total hemispherical emissivity and the thermal conductivity coefficient were measured for different load rates, we will conclude on the interest and the potentialities of tested materials.