The objective of the present work is to evaluate the wind potential in the nearshore of the Mediterranean Sea. Thus, a comprehensive picture of the wind conditions is provided by considering 15-year of cumulative information coming from remotely sensed data and from two numerical models. These are provided by the European Center for Medium-Range Weather Forecasts (ECMWF) and the National Centers for Environmental Prediction (NCEP). Since most of the offshore wind turbines usually operate at about 80 m height, the initial wind conditions (reported at 10 m) were adjusted to this height and various wind parameters were evaluated. Besides these, the characteristics of the Vestas V90-3.0MW wind turbine were used to identify the efficiency of this type of generator in terms of operating capacity, rated capacity and capacity factor. From the analysis of these data, it can be noticed that more energetic wind conditions are encountered in the northern part of the basin (close to the Spain–France border and south of Greece) and also in the southern part of the sea (Tunisia sector). In the final part of the paper, based on satellite measurements, the wind conditions (monthly and seasonal) coresponding to some representative locations in the Mediterranean Sea were compared to those from several offshore locations where wind farms already operate.

This chapter means to explain the tribological behavior of polymer-based materials, to support a beneficial introducing of those materials in actual applications based on test campaigns and their results. Generally, the designers have to take into consideration a set of tribological parameters, not only one, including friction coefficient, wear, temperature in contact, contact durability related to application. Adding materials in polymers could improve especially wear with more than one order of magnitude, but when harder fillers are added (as glass beads, short fibers, minerals) the friction coefficient is slightly increased as compared to neat polymer. In this chapter, there are presented several research studies done by the authors, from which there is point out the importance of composite formulation based on experimental results. For instance, for PBT sliding on steel there was obtained a friction coefficient between 0.15 and 0.3, but for the composite with PBT + micro glass beads, the value of friction coefficient was greater. Adding a polymer playing the role of a solid lubricant (PTFE) in these composites and also only in PBT, decreased the friction coefficient till a maximum value of 0.25. The wear parameter, linear wear rate of the block (from block-on-ring tester) was reduced from 4.5 μm/(N⋅km) till bellow 1 μm/(N⋅km) for a dry sliding regime of 2.5…5 N, for all tested sliding velocities, for the composite PBT + 10% glass beads +10% PTFE, the most promising composite from this family of materials. This study emphasis the importance of polymer composite recipe and the test parameters. Also there are presented failure mechanisms within the tribolayer of polymer-based materials and their counterparts.

Purpose: – The paper aims to present results on the friction and the wear of polytetrafluoroethylene (PTFE) and eight commercially available composites with PTFE matrix, for tests done on shoe/roller tribotester with water lubrication in open circuit. There are pointed out particular tribological processes within the superficial layers of the composites with the help of optical microscopy.Design/methodology/approach: – Analysing the tribological behaviour of eight grades of PTFE composites sliding in water on shoe/roller tribotester.Findings: – Good results of wear behaviour under water lubrication for all the composites. PTFE exhibits severe wear under the tested regime.Originality/value: – The research could support PTFE composite application for water lubricated systems.

This paper presents the influence of TiO 2 as additive in refined rapeseed oil in different massic concentration (0.25%wt, 0.50%wt and 1%wt) on the tribological parameters. Tests are done on a four-ball machine from the laboratory LubriTest, at "Dunarea de Jos" University of Galati. The test parameters were load: 100 N, 200 N and 300 N and the rotational speed 1000 rpm, 1400 rpm and 1800 rpm. Particles of TiO 2 have an average size of 215 nm. The rapeseed oil was supplied by Prutul Galati. For the tested ranges of the parameters, the additivation of rapeseed oil with TiO 2 do not improve the friction coefficient and the wear rate of WSD. The additivation of rapeseed oil with TiO 2 is still less efficient for the tested ranges of load and speed as compared to the neat rapeseed oil, but there is visible that friction coefficient and analysed wear parameter are less influenced by the regime for the concentration of 1% TiO 2 in rapeseed oil.

This paper presents results on tribological characteristics for polymer blends made of polybutylene terephthalate (PBT) and polytetrafluoroethylene (PTFE). This blend is relatively new in research as PBT has restricted processability because of its processing temperature near the degradation one. Tests were done block-on-ring tribotester, in dry regime, the variables being the PTFE concentration (0%, 5%, 10% and 15% wt) and the sliding regime parameters (load: 1, 2.5 and 5 N, the sliding speed: 0.25, 0.5 and 0.75 m/s, and the sliding distance: 2500, 5000 and 7500 m). Results are encouraging as PBT as neat polymer has very good tribological characteristics in terms of friction coefficient and wear rate. SEM investigation reveals a quite uniform dispersion of PTFE drops in the PBT matrix. Either considered a composite or a blend, the mixture PBT + 15% PTFE exhibits a very good tribological behavior, the resulting material gathering both stable and low friction coefficient and a linear wear rate lower than each component when tested under the same conditions.