Papers by Keyword: Temperature

Abstract: The formation of metatitanic acid particles in the form of rutile TiO₂ is an important step in the sulfuric acid process used to manufacture white pigment. F value, temperature and stirring speed were investigated to study their influence on the particle size and distribution in this paper. The results showed that suitable size and narrow particle size distribution were obtained in metatitanic acid on the condition that F value was 2.02, the temperature was 95°C and the stirring speed was 300r/min. Metatitanic acid was calcined above 850°C to form rutile TiO₂. The crystal structure and micromorphology of TiO₂ were characterized by XRD and SEM, respectively. The results demonstrated that a rutile TiO₂ with high crystallinity was prepared.

Abstract: The degradation of polycarbonate (PC) food contact materials was studied based on analysis with GC-MS, FTIR, UV-Vis and TG techniques. It was evident that the processing temperature of the materials significantly enhanced the release of bisphenol A, an endocrine disruptor. Investigation of the redshift of UV band also revealed that high temperatures accelerated the aging degradation of PC.

Abstract: The low cycle fatigue behaviour of TA29 titanium alloy blisk forging at 300°C, 400°C, 500°C, 600°C were studied. The cyclic stress response, the stress-strain behaviour, the fatigue life and the fractograph were observed and analyzed. Through the double logarithm linear regression, the Coffin-Manson model parameters of TA29 titanium alloy at different temperatures were obtained. The results showed that the fatigue life decreases as the strain amplitude increases. Also, the testing temperature has a significant effect on the low cycle fatigue properties of TA29 titanium alloy. At the same level of the strain amplitude, the fatigue life and the peak value of cyclic stress decrease, while the plastic strain component in total strain amplitude increases with the increase of testing temperature. On the basis of the fractograph of fatigue specimens, the initiation of crack is mainly on the surface of the specimen. Fatigue striations can be seen clearly at fatigue crack propagation area. The fatigue striations in stable fatigue crack propagation area were broadened, and the propagation area was reduced and the final rupture area was increased with the increase of testing temperature.

Abstract: Vibration and noise are the dangers for equipment, human health and environment. Developing of a new Mg matrix composite with high damping performance and high strength rate has been acknowledged as an important approach for the reduction of vibrations and prevention of noise. In this paper, xHA/Mg-3Zn-0.5Zr (x=0.5wt.%, 1wt.%, 1.5wt.%) composites were prepared by vacuum induction melting and hot extruding. The microstructure and damping performance were observed and measured using an optical microscope and a dynamic thermomechanical analysis apparatus (DMA), respectively. The influence of HA and environmental factors (temperature, frequency and strain amplitude) on the damping performance of HA/Mg-3Zn-0.5Zr composites were studied. The results showed that the damping performance of HA/Mg-3Zn-0.5Zr composites increased with increasing HA content and strain amplitude. The damping mechanism was in line with the G-L theory and interface damping theory. The damping values were strongly amplified at 150-300°C. The plot of damping versus temperature showed a peak for the Mg-3Zn-0.5Zr-1HA composite at 235°C. The low frequency damping values of xHA/Mg-3Zn-0.5Zr were higher than the high frequency damping values. It is suggested that the change of damping by a variety of external factors is due to the presence of different dominant damping mechanism at different conditions. Furthermore, it was found that at increased HA content, the grain size of HA/Mg-3Zn-0.5Zr composites decreased and the tensile strength and elongation of HA/Mg-3Zn-0.5Zr composites improved. This work will be beneficial for the study of Mg based joint implant materials with high vibration damping performance.

Abstract: The development of the city traffic and its increasing traffic flux are the signs of the development of the society, but causing a serious pollution on the city's ecological environment. Cement hydration reactions are needed to generate Ca (OH)₂, C-S-H gel, and AFt, as well as other hydrated products. Meanwhile, heavy metal ions are contained and fixed in a cement paste under physical encapsulation, absorption, isomorphous replacement, and double decomposition. This paper mainly discusses the impact of hydration environment on the adsorption law of materials adsorbing heavy metal ions and the adsorption mechanism under different pH values and temperatures, analyzing specific reasons from the perspective of micro-structure. Through the analysis it can be seen that, in addition to zinc ions, the cement-based materials’ capacity of adsorbing heavy metal ions increases as the pH value and the temperature increase. Micro-structure analysis shows that cement-based materials’ main adsorption methods are different when pH values are different.

Abstract: This work will focus on the preparation of yttrium iron garnet (Y₃Fe₅O₁₂, YIG) via mechanical alloying technique derive by steel waste product. The Fe₂O₃ powder derived from the steel waste purified by using magnetic and non-magnetic particles (MNM) and Curie temperature separation (CTS) technique. The purified powder was then oxidized in air at 500 °C for 9 hours in air. The Fe₂O₃ was mixed with Y₂O₃ using high energy ball milling for 9 hours. The mixed powder obtained was pressed and sintered at different temperature 500/600/700/800/900/1000/1100 °C. X-ray diffraction (XRD) shows the YIG is completely form at 1100 °C. The field emission scanning electron microscopy (FESEM) images shows the grain size increases as increase the sintering temperatures. The frequency dependence on the complex permeability, µ’ and magnetic loss, µ’’ in the frequency range 10 MHz to 1 GHz were measured in this study. The results showed that the highest μ΄ is 5.890 obtained from 1100 °C.

Abstract: The paper presents an analysis of the selection of the regression function in the optimization of steel turning using Taguchi method. The study attempts to investigate cutting force and temperature during turning of steel. Taguchi L16 (4) 2 orthogonal array has been applied for experimental design. S/N ratio and ANOVA analyses were performed to identify significant parameters influencing cutting force and temperature. Mathematical models for both response parameters i.e. cutting force and temperature roughness were obtained through regression analysis. The confirmation experiments carried out at optimal combination of parameters given by Taguchi’s analysis. The optimal solution provided by desirability function optimization was compared with the optimal setting of parameters given by Taguchi analysis. The optimization results provided by both techniques are in close proximity.

Abstract: Research of the correlation of the biomechanical characteristic of a sitting human and car seat is based on measurements of several basic parameters, such as value of the area contact pressure, map of contact temperature, contact humidity, etc. So obtained map of surface each parameter which we can compare at a same time and so we can identify correlations between these parameters and biomechanical properties of human, e.g. human anatomy, the body forms, age, sex physique etc. Based on these analyzes is possible to optimize the levels of this parameters for obtaining the ideal seating comfort. The correlation between fatigue for the driver and sitting comfort is described in many publications dealing with this theme. However, a repeatability real experiment in a car is questionable [1]. It is therefore preferable to perform these measurements in the laboratory and simulate the same conditions as in moving car at a constant ambient temperature and humidity, with the same test persons. The most suitable is the use in the measurement of different types of car seats and various human.

Abstract: Low-pressure steam turbine parts are generally exposed to lowest steam parameters only and it could seem that they should not be susceptible to permanent deformation. However, this assumption is incorrect and permanent changes in geometry become visible in low-pressure turbine casings when they are disassembled after the first time in operation. The driving mechanism of the plastic deformation of the low-pressure casings is mainly the non-uniform temperature field. This paper deals with results obtained from a numerical FEM simulation of a steam turbine low pressure part, which includes elastic-plastic behavior of the material, and results measured under the real conditions.

Abstract: Shown are results of theoretical and experimental research of force modes and limit possibilities of the first and subsequent operations of combined isothermal drawing of axisymmetric parts made out of anisotropic materials through conic and radial matrixes in the mode of short-time creeping. Studied was straining of anisotropic material under conditions of short-time creeping. We ignore the elastic components of strain. We introduced potential straining speeds for an anisotropic body under conditions of short-time creeping. Found was the effect of technological parameters, anisotropy of mechanical properties, and of age-hardening upon the stress condition, the force modes of the operation, and upon the design margin of strain during the first and subsequent operations of combined drawing. Experimental research was carried out for the force conditions and possible limits of straining during the first and second operations of combined isothermal drawing with convex-face and conic matrices in the mode of short-time creeping. Comparing the results of theoretical and experimental research for force modes and strain limits during the first and subsequent operations of combined drawing has shown their satisfactory similarity (up to 5% - 10%).