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Acta Physica Polonica A
|
2015
|
vol. 127
|
issue 4
1388-1392
EN
In this study, a counter flow convection-type dryer was designed and manufactured. During experiments, four different geometrical forms of pepper specimens were dried in a complete (unsliced), perforated, crosscut, and longitudinally sliced forms. For each type of red pepper specimens, the experiments have been conducted at air velocity level of 0.5 m/s, relative humidity of 10-15%, and temperature of 55-60°C. The theoretical mathematical model of drying process was developed, considering the pepper's bottom surface to be isolated. The drying curves of experimental results are compared to ones obtained from the theoretical analyses. The comparison showed that experimental results are consistent with the theoretical model. The best results, considering the drying duration, are collected from the specimens sliced longitudinally, which were followed by the crosscut specimens, perforated and unsliced-complete specimens, respectively. 82% water (humidity) content in 500 g sample was reduced to 4% in longitudinally cut samples, 6% in crosscut samples, 7.5% in perforated samples and 8% in unsliced-complete samples, after 14 hours of drying. It is suggested that regarding to easiness of processing, the crosscut red peppers are more suitable, compared to the other geometrical forms.
EN
Controlling the heat, generated during the cutting process, is an important factor in improving the quality of the product and performance of the machining. A vortex tube was employed to evaluate the effects of cooling on the turning parameters. Various cutting parameters (100 m/min, 250 m/min and 400 m/min) together with various cooling temperatures (-4°C, 8°C and 20°C) were considered to find surface roughness, cutting force and cutting temperature. Response surface methodology was used to optimize the experimental parameters. The best attainable surface roughness value was found to be 0.77 μm Ra, under the conditions of 0.15 mm/rev feed, 400 m/min cutting speed, -4°C (with vortex tube) cutting temperature and 1.2 mm tool edge radius. Cutting forces were not affected by the temperature changes. The difference was negligible and as small as 1%. The minimum cutting temperature was 74.17°C, which was obtained under the machining conditions of 0.25 mm feed, 250 m/min cutting speed -4°C (with vortex tube) cutting temperature and 0.8 mm tool edge radius.
EN
In this study, DP 600 (Dual-Phase) steel plates having 1 mm thickness were joined by copper-based CuAl8 wire in gas metal arc brazing technique. Specimens were prepared as butt joint. Brazing operations were done with ten different arc voltages and weld currents as 40, 45, 50, 55, 60, 65, 70, 75, 80 and 85 A. Tensile strength, bending force, microstructure of brazed materials, and their microhardness distribution throughout joining were determined. In macro and microstructure examinations, stereo optical microscope, scanning electron microscope (SEM) and energy dispersive spectroscopy were used. This study investigated the effects of current intensity on microstructure and microhardness distribution of transition zone between DP 600 steel and MIG-brazed joint. The tensile strength and bending resistance increase with increasing current intensity.
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