Defect and Diffusion Forum Vol. 441

Abstract: It is well known that the surface roughness in turning consists of the theoretical roughness, vibration in the depth of cut direction, and overcutting by adhered work material. Some of authors had already proposed the method to calculate surface roughness components. In this method, the approximate arc was used as a representative tool contour of the tool contour to dividing roughness curve into each feed marks. The arc was defined by the height of the intersection of the measured tool contours set at feed intervals horizontally. However, when the boundary wear occurred in the finished surface formation area, the arc defined by the height of the intersection sometimes didn’t agree with theoretical roughness obtained by the measured tool contours set at feed intervals horizontally. As a result, there was concern that the difference affected the prediction reliability of tool edge contour position during cutting. Therefore, both of theoretical roughness and approximate arc of the measured tool contour were defined by the peak point of the measured tool contours set at feed intervals horizontally. Additionally, the representative tool contour was also defined by the different arcs to adopt the asymmetry of tool wear. Using the newly representative tool contour, the reliable roughness components could be calculated regardless of the tool pattern.

Abstract: The utilization of hydrogen in the construction of a decarbonized society is expected to expand the application of austenitic stainless steels with high resistance to hydrogen embrittlement as structural materials. However, the residual stress generated during machining causes material deformation, leading to increased costs and decreased productivity. Therefore, cutting methods that can control residual stress are necessary, prompting numerous studies on residual stress. We proposed conditions to reduce deformation and clarify the relationship between the depth of cut and material deformation, as well as the relationship between residual stress and material thickness after machining. In this study, stainless steel (AISI 304) was face milled, and the relationship between the cutting temperature and material deformation after machining was evaluated, as in a previous study. In addition, electrolytic polishing was performed to measure the residual stress in the depth direction, and its relationship with material deformation was evaluated. The experimental results showed no correlation between the cutting temperature and deformation. However, the measurement of the residual stress in the depth direction suggests that the removal of the surface layer by electropolishing may affect material deformation and residual stress.

Abstract: Experimental research was conducted on a horizontal mini-pipe to obtain primary data on the effect of different glucose concentrations on the void fraction. The experiment was performed on a test section using a 1.6 mm diameter mini glass pipe in a horizontal position. The gas phase consisted of dry air, and the liquid phase was a 0.9% sodium chloride solution with glucose concentrations of 5% and 10%. The superficial gas velocity (J_G) ranged from 0.083 m/s to 74.604 m/s, while the superficial liquid velocity (J_L) ranged from 0.041 m/s to 4.145 m/s. Void fraction data was obtained using a high-speed camera, and the results were processed through image analysis. The detected flow patterns were plug, slug-annular, annular, bubble, and churn. The stratified flow pattern was not observed in this study. An increase in JG generally results in an increase in the void fraction (ε).

Abstract: A wet cooling tower is an apparatus for transferring heat and mass that directly links hot water and air movement. Because the wet cooling tower provides a large surface area for heat and mass transfer, fill is essential to the tower. This study uses experiments to investigate the performance of a multi-level inclined perforated splash fill in a forced wet cooling tower (WTC). The packing has a 2.6%, 3%, and 3.6% perforation ratio and an inclination angle of 15 degrees, with five layers of galvanized plate fill. The hot water temperature is adjusted to 60 degrees Celsius. The airflow rate varies five times: 0.02033, 0.02631, 0.02995, 0.03770, and 0.04261 kg/s. The water flow rate is ± 0.0917 kg/s. The hot water at the inflow is 60 degrees Celsius. The findings of this study indicate that the cooling efficiency of cooling towers may be significantly improved by raising the mass airflow rate and adopting the suitable perforation ratio.

Abstract: Renewable energy has become a promising alternative energy due to innovations that have reduced costs and realized the future of environmentally friendly energy. Hydroelectric power plants are one of the most promising renewable energy in Indonesia, especially in areas with many rivers. In many low head water flow locations, Archimedes Screw Turbine (AST) may be more cost-effective, with lower installation and operation costs than alternative hydroelectric power systems. Although many theoretical and experimental investigations have been published regarding the implementation of this AST over the past decade, there has been no experimental evaluation in the literature for heads below 1 meter. This post presents test results from Single Screw Archimedes turbine with a difference in flow rate of 106 l/min, 291 l/min, 594 l/min, and 1035 l/min and head variations of 0.7 meters, 0.8 meters, 0.9 meters, and 1 meter. Maximum turbine power of 93.93 Watt at 1035 l/min at head 0.7 meters. The results provide new insights into the performance of the Archimedes screw turbine efficiency under the 1-meter head. The flow rate is comparable to torque and power increases as the turbine entry flow increases.