高性能零件制造过程质量控制方法研究

针对高性能零件批量少、品种多的生产模式,提出了利用改进的田口质量损失函数的关键工序确定方法。通过对质量损失度的计算,用数字来确定关键工序。在数据处理方面,针对样本量少的情况,提出了基于历史数据的相似工序成组法,使样本量的问题迎刃而解。最后,列举了实例,对上述两种方法进行了有效的验证。

Combustion characteristics of Daqing oil shale and oil shale semi-cokes

Thermo-gravimetric-analysis(TGA) was used to analyze the combustion characteristics of an oil shale and semi-cokes prepared from it.The effect of prior pyrolysis and TGA heating rate on the combustion process was studied.Prior pyrolysis affects the initial temperature of mass loss and the ignition temperature.The ignition temperature increases as the volatile content of the sample decreases.TG/DTG curves obtained at different heating rates show that heating rate has little effect on ignition temperature.But the peak of combustion shifts to higher temperatures as the heating rate is increased.The Coats-Redfern integration method was employed to find the combustion-reaction kinetic parameters for the burning of oil shale and oil shale semi-coke.

Experimental study on gas explosion suppression based on ferrocene

In order to study the gas explosion suppression performance based on ferrocene, the self-constructed experimental facility was used to accomplish the experiment of gas explosion suppression. By means of thermogravimetric analysis, the thermal characteristics of ferrocene have been gotten and the gas explosion suppression mechanism of ferrocene has been analyzed. The results show that ferrocene had good effects on gas explosion suppression, and the explosion pressure and flame propagation speed declined obviously. When ferrocene concentration is 0.08 g/L and methane volume concentration is 9.5%, the maximum explosion overpressure and maximum flame propagation speed of methane-air respectively decreased by about 59.5% and 19.6%, respectively. TG and DSC curves showed that the mass loss of ferrocene consists of two processes, which are sublimation and lattice fracture. The temperature of mass loss ranged from 128 ℃ to 230 ℃. The results showed profoundly theoretical significance to gas explosion suppression by ferrocene in coal mines.

Corncobs as Substrate for Oleaginous Yeast-Pretreatment via Steam Explosion and Hydrolysis

Corn cobs are a promising lignocellulosic substrate for the production of biofuels like bioethanol via conventional yeast or biodiesel via oleaginous yeast. Pretreatment of the substrate is essential for further hydrolysis and fermentation steps. This study focused on the steam explosion method as pretreatment. Therefore, different steam explosion severities were evaluated. The content of glucan, xylan and Klason lignin was examined. Xylan degraded with increasing severity from 412.7 g·kg-1 （untreated） to a minimum of 127.3 g-kg1 dry matter （190 ℃/30 min）. Glucan concentrations increased from 315.1 g·kg1 （untreated） to a maximum of 371.6 g·kg-1 dry matter （200 ℃/20 min）. For soluble lignin, an increase could be observed at rising severity, from 145.3 g·kg-l （untreated） to a maximum of 214.9 g·kg-1 dry matter （190 ℃/30 min）. Furthermore, the mass recovery was calculated. At harsher pretreatment conditions, a significant mass loss was observed, estimated by the ash content in the recovered dry matter. The lowest recovery rate was observed for SF = 4.13 （190 ℃/30 min） with 68.39%. The produced inhibitors were evaluated.

Evaluation of Hydroabrasion in a Slurry Tank

A slurry erosion tank test rig was designed and built to investigate the erosion rates of different materials and effects of the influencing parameters on material loss and erosion profiles. A CFD （computational fluid dynamics） tool is applied to study the flow impact velocity, solid concentration and particle size effects on the erosion rate of sample plates in the liquid-solid mixture in a cylindrical tank. The MRF （multiple reference frames） method is applied to model the rotating parts inside the tank. The flow behavior and liquid-solid interactions in the slurry tank test rig are simulated and the results are validated with the experimental data. It was approved that changing the height and diameter of each rotating zone （MRF zones） have a negligible effect on simulation results. It was observed that the erosion mass losses are increasing with increase in flow velocity and sand concentration. Both variations can be predicted with a logarithmic dependence of mass loss to rotational velocity and sand concentration. The increase in erosion rate by increase in particle size was also observed for three various particle size distributions.

Experimental Study on Elevated Fires in a Ceiling Vented Compartment

The impacts of elevation on fires in a ceiling vented compartment were investigated experimentally. The flame behavior of elevated fires was recorded. Various parameters including the fuel mass loss rate, the light extinction coefficient, the oxygen concentration and the gas temperature were measured. Results indicated that the variations of the flame behavior were consistent with that of the fuel mass loss rate. The fire location significantly impacted the light extinction coefficient, the oxygen concentration and the gas temperature, which all showed distinct stratification phenomena. For a higher elevated f＇we, the average fuel loss rate and the overall light extinction co- efficient were smaller, the oxygen concentration was higher and the gas temperature was lower. In addition, the smoke descending was slower. From the perspective of those parameters the fire was less hazardous if the fire was elevated higher, which was totally different from the elevated fires in closed compartments.

Thermal Analysis and Kinetics of Coal during Oxy-Fuel Combustion

The pyrolysis and oxy-fuel combustion characteristics of Polish bituminous coal were studied us/ng non- isothermal thermogravimetric analysis. Pyrolysis tests showed that the mass loss profiles were almost similar up to 870℃ ha both N2 and CO2 atmospheres, while further mass loss occurred ha CO2 atmosphere at higher temper- atures due to char-CO2 gasification. Replacement of N2 ha the combustion environment by CO2 delayed the com- bustion of bituminous coal. At elevated oxygen levels, TG/DTG profiles shifted through lower temperature zone, ignition and burnout temperatures decreased and mass loss rate significantly increased and complete combustion was achieved at lower temperatures and shorter times. Kinetic analysis for the tested coal was performed using Kissinger-Akahira-Sunose （KAS） method. The activation energies of bituminous coal combustion at the similar oxygen content in oxy-fuel with that of air were higher than that in air atmosphere. The results indicated that, with O2 concentration increasing, the activation energies decreased.

DFT Investigation of Structural,Electronic,Elastic and Optical Properties of SrMO_4(M=Mo and W)

A planes waves pseudo-potential calculations are performed for the SrMO4 （M=Mo and W） compound in order to investigate the structural, electronic, elastic and optical properties. The calculated lattice constants are in good agreement with experiment ones. The electronic structures show that SrMO4 has a direct band gap situated at F point. The calculated elastic constants indicate that both structures are mechanically stable. The bulk modulus, shear modulus, Young＇s modulus and Poisson ratio are investigated from the elastic constants, in the same time the anisotropy of the elastic properties is discussed. The imaginary part of the dielectric functions is calculated and the contributions of various transitions peaks are analyzed. Furthermore, the other optical properties such as absorption coefficient I（w）, optical reflectivity R（w）, energy-loss spectrum L（w）, and the refractive index n（w） have been investigated.