Narrow Results

In the present works effective application of partial preheating by high frequency induction to enlarge the partial diameter of middle carbon steel was experimentally investigated. The partial reheating was carried out by varying preheating times under the same electric power conditions. As all other conditions other than temperature remained constant during the diameter enlargement experiments, the partial preheating effects were clarified to be estimative using a parameter of the σ/σ_y, which was found to be dependent on temperature regardless of constant compressive axial stress. For heating times of less than 50 sec, the preheating effect for promoting partial diameter-enlargement did not appear. In fact the reverse effect appeared in times ranging from 30 sec to 50 sec due to blue brittleness generated at temperatures from about 523K to about 623K. Also, low cycle fatigue cracks must be avoided when initiating at the filet end of an enlarged shaft while passing through the temperature range of blue brittleness during the cooling process. Therefore, the preheating temperature found to be most effective for promoting the diameter enlargement was greater than about 856K so as to increase easily the D_f/D₀ to above 2 times without generating damage cracks from fatigue.

Thermal-assisted machining (TAM) is an effective processing solution to improve productivity and product quality made from materials with high strength and hardness. This method is widely used in nonchip machining such as forging, stamping, deep drawing, etc. For the method of heating on the molds, it is possible to control local heat or uniform heat on the workpiece. However, the calculation of heat capacity, heat transfer as well as the heating time to achieve the temperature on the workpiece is necessary to design suitable molds and heating system. This study focuses on a heating system that uses single-sided thermostatic heating rods to heat the molds, verify the effect of the heating time on the temperature of the workpieces and then control the temperature on the workpieces at various heat levels through a heating control system. Thereby, this study proposes to build a mathematical model between temperature and heating time on the workpiece.

The synthesis and properties of high luminescent thio-stabilized nanocrystals (NCs) in aqueous media was discussed in this paper. The sharp peaks of photoluminescence (PL) and full width at half-maximum (fwhm), were observed in the range of 50 to 70nm. The PH was 9 and the molar ratio of Cd to thiol (1:2.4) was constant during the experiment. The stabilized NCs through thioglycolic acid (TGA) show great luminosity in which the spectral of PL emission is variable with controlling the size of NCs. The size ranges of thioglycerol(TG) stabilized NCs and the spectral range of PL emission are more limited than TGA in the same condition. The concentration of thio-ligands and heating time are two factors that that will discuss in this paper to control the size of NCs.