Tribological performance of polymer composites used in electrical engineering applications

Sliding wear performance of 20% mica-filled polyamide 6 (PA6 + 20% mica) and 20% short glass fibre-reinforced polysulphone (PSU + 20 GFR) polymer composites used in electrical applications were investigated using a pin-on-disc wear test apparatus. Two different disc materials were used in this study. These are AISI 316 L stainless steel and 30% glass fibre-reinforced polyphenylenesulphide (PPS + 30%GFR) polymer composite. Wear test was carried out at 10, 20 and 30 N applied load values and 0·5 m/s sliding speed and at ambient temperature and humidity. Different combinations of rubbing surfaces were examined and friction coefficient and specific wear rate values were obtained and compared. For two material combinations used in this investigation, the coefficient of friction shows insignificant sensitivity to applied load values and large sensitivity to material combinations. For specific wear rate, PA6 + 20% mica composite has shown insensitivity to change in load, speed and materials combination while PSU + 20% glass fibre composite has shown high sensitivity to the change in load and material combinations. The friction coefficient of PA6 + 20% mica and PSU + 20 glass fibre rubbing against the AISI 4140 steel disc is between 0·35 and 0·40. In rubbing against PPS + 30% glass fibre their values were between 0·25 and 0·30. Specific wear rate for PA6 + 20% mica and PSU + 20% glass fibre composites are in the order of 10^???13 to 10^???14 m²/N. Finally, the wear mechanisms are a combination of adhesive and abrasive wear processes. In terms of application, especially in electrical systems, a substantial contribution was provided to extend switch life. Thus, besides robustness, this also ensured safety for the system and the users against undesirable situations.     

Moisture Sorption Isotherms of Dried Apricot, Fig and Raisin at 20 °C and 36°C

Isotherms were found to be of type I, typical of high sugar foods. Study on temperature dependence of isotherms showed that above water activities of 0.6, moisture content was higher at higher temperature. This was explained by endothermic dissolution of sugar at high water activities. Iglesias and Chirife, Halsey, BET and GAB equations were tested to fit the data. Monolayer moisture contents for the three foods were determined from BET and GAB equations. In both models, monolayer moisture was found to decrease with increasing temperature. Isosteric heat of sorption data from the isotherms at two temperatures, revealed that strength of interactions between water vapor and adsorbent increased with moisture content.     

Uncertainty modelling of critical column buckling for reinforced concrete buildings

Buckling is a critical issue for structural stability in structural design. In most of the buckling analyses, applied loads, structural and material properties are considered certain. However, in reality, these parameters are uncertain. Therefore, a prognostic solution is necessary and uncertainties have to be considered. Fuzzy logic algorithms can be a solution to generate more dependable results. This study investigates the material uncertainties on column design and proposes an uncertainty model for critical column buckling reinforced concrete buildings. Fuzzy logic algorithm was employed in the study. Lower and upper bounds of elastic modulus representing material properties were defined to take uncertainties into account. The results show that uncertainties play an important role in stability analyses and should be considered in the design. The proposed approach is applicable to both future numerical and experimental researches. According to the study results, it is seen that, calculated buckling load values are stayed in lower and upper bounds while the load values are different for same concrete strength values by using different code formula.     

Recipe development for production of a Turkish dessert,cheese halva

Within the scope of this study, six different recipes were developed for the production of cheese halva. White unsalted cheeses were produced by using cow milk or sheep milk or a blend of cow and sheep milk, and each was produced with white flour or semolina. It was found that there was no significant difference among the recipes in terms of chemical properties, but there were significant differences in sensory properties. Moreover, the microbial quality of cheese halva were determined. It was found that the shelflife of cheese halva can be up to 10 days at ambient temperature and for up to 1 month when refrigerated.