Papers by Keyword: Temperature Increase

Abstract: In this study, the temperature increase of the Ti-17 alloy (Ti–5Al–2Sn–2Zr–4Cr–4Mo, wt.%) during isothermal forging in the (α + β) dual-phase region was investigated using large-size workpieces forged between hot dies in a 1500-ton forging press. The temperature increase was predicted using finite element analysis (FEA). The tip of a thermocouple was inserted into the center of the workpiece (diameter: 100 mm; height: 50 mm). The forging temperatures were 1023 K (750 °C) and 1073 K (800 °C) in the (α + β) dual-phase region. The strain rate was 0.05 s⁻¹ and 0.5 s⁻¹ at each temperature. Meanwhile, the compression percentage was 75%. The true stress–true strain curves were inversely obtained by fitting the load–stroke curves using the FEA. The predicted temperature was in a good agreement with that in the experimental results when the value of 1.0 was used as the conversion factor for plastic deformation energy to heat energy in the FEA under the current forging conditions. At the strain rate of 0.5 s⁻¹, the temperature instantly increased to a β-transus temperature in 3 s at 1073 K (800 °C). In contrast, the temperature logarithmically increased at both 1023 K (750 °C) and 1073 K (800 °C) at 0.05 s⁻¹ in 28 s (e.g., 42 K at 1023 K (750 °C)). The obtained true stress–true strain curves indicate that flow softening occurred during the forgings, which is attributed to dynamic recrystallization and/or dynamic recovery. The temperature increase in the Ti-17 alloy was smaller than that in the Ti–6Al–4V alloy under the same forging condition.

Abstract: The SPSS19.0 software was used to analyse the data of enclosure experiments last for 7 days in summer of 2011. Water temperature increase as a factor to establish the statistical model, and the response relation of thermal discharge warming and Coscinodiscus Jonesianus biomass was analyzed quantitatively. The results showed that, it would promote Coscinodiscus Jonesianus growth and reproduction with the water warming at 0.2°C to 0.79°C , which would be restrained at the water warming at 0.8°C to 2.0°C. When the water temperature increase 0.1°C, 0.4°C and 0.7°Cwill respectively result in Coscinodiscus Jonesianus biomass grow 216.12%, 72.87% and 15.05%. While the water temperature increase 1.0°C, 1.5°C and 2.0°C will respectively result in Coscinodiscus Jonesianus biomass reduce 6.38%, 17.95% and 26.17%.

Abstract: The kinetic energy of lift car will be consumed by the friction between the safety gear and guide rail in emergent braking process. This will lead to remarkable temperate increase of frictional surface. Due to the explosive atmospheres in which the explosive-proof lift servers, the high temperature may result in severe explosion accident. In this paper, an finite element model is developed to analysis this progress. The transient heat flux density is derived from energy transformation progress in safety gear action, and applied as boundary condition to the finite element model. Experiments are carried out to measure the temperature increase of safety gear frictional surface, and the results show good coincidence of temperature increase tendency between experiments and simulations.

Abstract: Trend of the high-speed and high efficiency machining has pushed the continuous demand of higher spindle speed and power for the machining center application. However, Conventional steel spindles are not appropriate for high speed operation because of their high rotational inertia and low damping ratio. Moreover, heat generation and dynamic loading caused by high speed rotation have been obstacles for increasing the speed limit in many conventional steel spindles applications. Apart from optimizing lubrication, the application of new materials is an interesting alternative to increase the boundary speed and life-span of roller bearings for machine-tool spindles. In this study, a high speed grinding motorized spindle equipped with hot isostatically pressed silicon nitride (HIPSN) fully-ceramic ball bearings without inner rings and yttria partially stabilized tetragonal zirconia polycrystal (Y-TZP) ceramic spindle shaft was designed for higher speed, rigidity, precision and longer operating life. Furthermore, the characteristics of ceramic motorized spindle, such as temperature increase, vibration, power, rigidity, noise and so on, were investigated by the experimentation. The results show that the ceramic motorized spindles have good behaviors under low load, high speed grinding conditions.