Khaled Elleuch

Thermophysical and Radiative Properties of Conductive Biopolymer Composite

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.

Damage of Stainless Steel Components by Olive Paste

ABSTRACT Failure of equipment for processing olives interrupted oil production after only 3 weeks in service. Macroscopic and microscopic analyses were used in the present investigation to analyze damaged surfaces. Observations and data suggest that failure was induced via tribocorrosion with a predominance of mechanical damage. This damage is attributed to abrasive wear combined with corrosion of AISI 304L stainless steel in olive paste (seed particles and pulp) mixed with tap water. Microscopic observations revealed fracture and localized plastic deformation in the damaged area along with a tribologically transformed structure and work-hardened surfaces. The tribological behavior of AISI 304L was determined using a pin-on-disc tribometer, and these results were compared to damage on the olive processing equipment. The steel was sensitive to tribo-oxidation, mostly due to abrasion by seeds and steel wear particles, and somewhat due to corrosion reactions with the environment.

A greenhouse comportments extraction using a neuro-fuzzy classifier

In this paper we present an incremental neuro-fuzzy classifier algorithm. The validation step is given on two linear different comportments and it is then compared with the fyzzy c-means method. This neuro-fuzzy classifier is then used to extract comportments (behaviors) of a greenhouse operating during one day.

On the Tribocorrosion Responses of Two Stainless Steels

ABSTRACT Tribocorrosion has considerable effects on AISI 304L used in olive processing equipment. In fact, some investigations have been conducted to compare the tribocorrosion behavior of AISI 304L to UNS 2205 stainless steels sliding against alumina in olive pomace–tap water filtrate. The active and passive surface states involved in tribocorrosion mechanisms of the steels have accordingly been analyzed. Mechanical and corrosion wear components were quantified. It was revealed that the tribocorrosion mechanism was dominated by mechanical removal. The mechanical resistance of UNS 2205 proved to be more important than that of AISI 304L. Furthermore, UNS 2205 was more sensitive to corrosion under sliding than AISI 304L due to its two-phase microstructure.

Effects of 316SS addition on the properties of the coatings based on Al2O3 applied by plasma spraying

Ceramic plasma-sprayed coatings are successfully used for prolonging the service life of industrial components where high wear and corrosion resistance are required. In this work, various types of coatings based on alumina were deposited by atmospheric plasma spraying on 304 L austenitic stainless steel substrate. These coatings were used in further tribological studies. For the atmospheric plasma spraying applications, spraying parameter choices such as carrier gases, plasma enthalpy, current intensity, spraying distance, and particles granulometry are the key issues. Two kinds of Al2O3 particle sizes 2–12 µm (Amperit) and 15–45 µm (Norton) were used to prepare pure and composite coatings. The spraying distance was varied from 90 mm to 120 mm. Microstructure characterization performed by scanning electron microscopy showed that the Amperit powders projected at a distance of 90 mm provided better cohesion and a more dense microstructure. However, the choice of the spraying distance of 120 mm was defined to manufacture composite structures, which allowed more stability in the plasma jet and enabled large metal particles to be mixed with ceramics. To develop hard and wear-resistant coatings, alumina and 316SS were mixed with different addition rates by volume (Al2O3–5 vol.%316SS and Al2O3–25 vol.%316SS) and fed through a single injection port. Composite coatings include porosity and unmolten particles in a lamellar microstructure. The addition of 316SS powder led to the formation of typical layered structure due to the effect of viscosity and different densities of the two particles. These coatings were investigated by different tests to evaluate microhardness, cohesion, and fracture values of such materials. Despite the significant decrease in the microhardness values, the 316SS particle addition demonstrates an improvement in the toughness and crack resistance.

Multiple Neural Control Strategies Using a Neuro-Fuzzy Classifier

The paper deals with the control of complex dynamic systems. The main objective is to partition the whole operational system domain in local regions using an incremental neuro-fuzzy classifier in order to achieve multiple neural control strategies for the considered system. In our case, this approach is applied to a greenhouse operating during one day. Therefore, banks of neural controllers and direct neural local models are made from different partitioned greenhouse behaviors and two multiple neural control strategies are proposed to control the greenhouse. The selection of the suitable controller is accomplished by computing the minimal output error between desired and direct neural local models outputs in the case of the first control strategy and from a supervisor block containing the considered neuro-fuzzy classifier in the case of the second control strategy. Simulation results are then carried out to show the efficiency of the two control strategies.

Optimization of mechanical and tribological properties of anodized 5754 aluminium alloy

This paper deals with the optimization of the micro-hardness and the tribological properties of the anodized Al 5754 aluminium alloy. A sulphuric anodizing process was considered. Three anodizing bath parameters, namely: the bath temperature, the current density, and the sulphuric acid concentration, were varied using Doehlert experimental design. The selected responses were: the micro-hardness, the wear rate and the growth rate of the anodic oxide layer. The variance analysis was used to check the adequacy of response models. Additional tests were performed to validate the obtained model. In order to maximize the growth rate and the micro-hardness of the anodic oxide layer and to minimize the wear rate at the same time, a multi-criteria optimization using the desirability function was performed. The main finding of this study indicated that under optimal anodizing conditions (T = 11.1°C, J = 2.1 A/dm2, Csul = 198 g/L), the estimated values responses were 0.64 μm/min, 442 HV, and 4.8% for the growth rate, micro-hardness and wear rate, respectively. The best friction behavior and the lowest wear rate of the optimum anodic layer could be correlated with the surface morphology of the anodic oxide layer revealed by the scanning electron microscopy and optical observations during friction and scratch tests.