The load on drive elements under extreme pressure conditions is significantly larger than that used in machine tools. When operating under a heavy load for a long period, large deformation and severe ...wear between the ball and the track are more likely to occur. To reduce wear, the most fundamental solution is to improve the surface properties of the material. Moreover, heat treatment is the most effective method to improve the surface properties of materials, thereby achieving wear resistance and low friction. It is necessary to develop a new heat treatment technology for wear resistance in extreme pressure conditions. Therefore, this study conducted experiments using a reciprocating friction tester. The responses of electrical contact resistance and the friction coefficient were measured synchronously to investigate wear resistance and low friction of the alloy steels after the induction heat treatment. Then, the results were compared and verified with low-carbon alloy steel after the traditional carburizing heat treatment. The experimental results show that the application of new induction heat treatment technology can not only improve the performance of drive components, but also save time and energy, and streamline the production process of the drive components. Therefore, the results of these wear analyses confirm that the induction heat treatment mode can replace the traditional carburizing heat treatment mode for drive elements.
The application of hardened aluminum alloys on the drive elements must be safe and reliable, T6 treatment is often used to improve their mechanical properties and dimensional stability. However, the ...impact of T6 treatment on operating life is not easy to evaluate. Hence, the effects of T6 treatment on the wear of aluminum 5083/6061/7075 were studied by a steel ball on disk tester. The results showed that T6 treatment tended to reduce the values of the friction coefficient about 9%. Moreover, T6 treatment had no significant effect on the frequency of the change of the friction coefficient of 5083 and 6061, but significantly affected that of 7075. T6 treatment can also reduce the size of wear particles about 16%. Based on the results, the wear mechanisms of aluminum 5083/6061/7075 with and without T6 treatment are described in this paper.
The process of preparing anti-glare thin films by spray-coating silica sol-gel to soda-lime glass was exclusively and statistically studied in this paper. The effects of sol-gel deliver pressure, air ...transport pressure, and spray gun displacement speed on the gloss, haze, arithmetic mean surface roughness, and total transmittance light were analyzed. The experimental results indicate that the factors of sol-gel deliver pressure, air transport pressure, and displacement speed exhibit a significant effect on the haze, gloss, and Ra. In contrast, the variation of total transmittance light with these three factors are insignificant. Because the anti-glare property is predominantly determined by low gloss and high haze, we therefore aim to minimize gloss and maximize haze to achieve high anti-glare. Central composite design and response surface methodology are employed to analyze the main and interaction effects of the three factors through quadratic polynomial equations, which are confirmed by the analysis of variance and R². The response surface methodology predict the lowest gloss and highest haze are 9.2 GU and 57.0%, corresponding to the sol-gel deliver pressure, air-transport pressure, and displacement speed of 250 kPa, 560 kPa, and 140 mm/s, and 340 kPa, 620 kPa, and 20 mm/s, respectively. Comparing the predicted optimal data with the real experimental results validates the applicability of the mathematical model. This study provides an important basis for the subsequent production of anti-glare glass with different specifications to satisfy the market demand.
► We develop a new design for metal-sheet roofing structure by using Phase change material (PCM). ► The design helps to reduce inward heat flow through roof to indoor space. ► The indoor comfort can ...be maintained much longer. ► The peak-load of indoor air conditioning can be shifted purposely by modifying PCM amount. ► We reported thermal performance of the new design in different weather conditions.
Heat flow through the roof contributes in the total heat gain of a building. The contribution becomes more severe for single story houses covered by metal sheet roofing. This paper presents a new design for metal sheet roofing structure in order to improve its total thermal resistance. Its main concept is to utilize phase change material properties to firstly absorb the downward heat flow made by incident solar radiation to the room and then release it back to the environment by means of the naturally favored external convection especially during the nocturnal cycle. Experimental and numerical analyses have been conducted to compare thermal performance of the new design and the available normal roofing with the same materials and color. A general mathematic equation system, which can be used for further evaluation and prediction of the new design with varied parameters, has been derived for the thermal process through the roof. The results show that the new design can effectively reduce the downward thermal flow through the roof into the house. As a consequence, the cooling load of the house can be lower and more electricity for cooling attempt can be saved.
In this study, an inverse algorithm based on the conjugate gradient method and the discrepancy principle has been successfully applied to an irregular fin made of functionally graded materials to ...estimate the unknown base heat flux distributions by using temperatures at some measurement locations. The inverse results, in which three different base heat flux distributions are to be determined, have proven current method's capability to accurately estimate arbitrary fin-base heat flux distributions even measurement errors have been taken into account. The temperature data calculated from the direct problem are used to simulate the measured temperature. The influence of measurement errors upon the precision of the estimated results is also investigated. This method does not need any prior information on the unknown quantity, and results show that excellent estimations can be obtained for the test cases considered in this study.
A novel interleaved high step-up DC-DC converter based on voltage multiplier cell and voltage-stacking techniques is proposed for the power conversion in renewable energy power systems. The circuit ...configuration incorporates an input-parallel output-series boost converter with coupled inductors, clamp circuits and a voltage multiplier cell stacking on the output side to extend the voltage gain. The converter achieves high voltage conversion ratio without working at extreme large duty ratio. The voltage stresses on the power switches are significantly lower than the output voltage. As a result, the low-voltage-rated metal-oxide-semiconductor field-effect transistors (MOSFETs) can be employed to reduce the conduction losses and higher conversion efficiency can be expected. The interleaved operation reduces the input current ripple. The leakage inductances of the coupled inductors act on mitigating the diode reverse recovery problem. The operating principle, steady-state analysis and design guidelines of the proposed converter are presented in detail. Finally, a 1-kW prototype with 28-V input and 380-V output voltages was implemented and tested. The experimental results are presented to validate the performance of the proposed converter.
The reforming of ethanol for hydrogen production was carried out in this study. The effects of ethanol supply rate, catalysts, O2/EtOH and different energy-saving approaches on the reforming ...temperature, H2 + CO (syngas) concentration and thermal efficiency were investigated. The results showed that the best H2 + CO concentration of 43.41% could be achieved by using rhodium (Rh), while the next best concentration of about 42.08% could be obtained using ruthenium (Ru). The results also showed that the conversion efficiency of ethanol, concentrations of H2 and CO, and the energy loss ratio could be improved by heat insulation and heat recycling; and the improvement in the reforming performance was greater by the Ru catalyst rather than by the Rh catalyst with the energy-saving approaches. The greatest improvement in hydrogen production was achieved when using the Ru catalyst with the addition of steam and heat recycling system under an O2/EtOH ratio of 0.625 and S/C ratio of 1.0.
► Ethanol was reformed to produce H2 by energy-saving ATR over various catalysts. ► Noble metal catalysts can achieve reforming under lower temperatures. ► Noble metals have better H2 selectivity than other catalysts investigated. ► Heat insulation and heat recycling can give better results than original system. ► Reforming was greatly improved by Ru catalyst with energy saving methods.
In this study, an inverse algorithm based on the conjugate gradient method and the discrepancy principle is applied to solve the inverse hyperbolic heat conduction problem in estimating the unknown ...time-dependent inner-wall heat flux of a hollow cylinder from the knowledge of temperature measurements taken within the medium. The inverse solutions have been justified through the numerical experiments in two specific cases to determine the unknown heat flux. Temperature data obtained from the direct problem are used to simulate the temperature measurements. The influence of measurement errors upon the precision of the estimated results is also investigated. Results show that excellent estimation on the time-dependent heat flux can be obtained for the test cases considered in this study. Once heat flux variation is accurately estimated, the evolution of temperature, displacement, and stress distributions can be calculated in great precision.
In this study, an inverse algorithm based on the conjugate gradient method and the discrepancy principle is applied to estimate the unknown space-dependent thermal conductivity of a functionally ...graded hollow cylinder. Two different boundary condition types are discussed. The results show that boundary condition type is very crucial to the success of the inverse method. For the case studied here, the inverse method works in conjunction with heat flux specified at the inner wall and convective heat transfer condition at the outer wall but not with constant temperatures specified at both inner and outer walls. The effect of measurement error and sensor number on the estimation accuracy is also investigated. The method can be developed into an accurate, simple, and inexpensive technique for the quality control during the manufacture of functionally graded materials.
In this study, an inverse algorithm based on the conjugate gradient method and the discrepancy principle is applied to solve the inverse hyperbolic heat conduction problem in estimating the unknown ...space- and time-dependent base heat flux of a cylindrical pin fin from the knowledge of temperature measurements taken within the medium. The inverse solutions have been justified based on the numerical experiments in which three specific cases to determine the unknown base heat flux are examined. The temperature data obtained from the direct problem are used to simulate the temperature measurements. The influence of measurement errors upon the precision of the estimated results is also investigated. Results show that an excellent estimation on the space- and time-dependent base heat flux can be obtained for the test cases considered in this study.
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