ARJ21复杂双曲面长桁零件弯扭复合冷成型方法

通过对零件几何特征和计算机辅助软件的分析,在掌握零件变化规律的基础上,确定了零件的成型方法,以及实验确定成型过程中各参数值。

Simplified Computation of Reflective Overpressure in Closed Cuboid Space Due to Internal Explosion

A simplified method is proposed for analyzing the overpressure history of an optional point on the walls of a closed cuboid due to its internal optional point-explosion. Firstly, the overpressure histories of all nodes on the walls of a cube with a side-length of 2 m are computed under a reference-charge explosion at each node of its inner space using the LS-DYNA software, and then are collected to form a reference database. Next, with the thought of the isoparametric finite element, an interpolating algori...

Extrapolation of High Pressure VLE Data and Simultaneous Representation of Excess Enthalpies by Using NRTL Equation

The non-random two liquids （NRTL） equation together with the Pitzer/Curl Virial equation of state are used to investigate the simultaneous representation of excess enthalpies （h^E） and vapour-liquid equilibria （VLE） and the VLE prediction from h^E data. The calculation strategy for properly determining NRTL parameters and the effect of their temperature dependence on the simultaneous correlation of h^E and VLE data and the VLE extrapolation are analysed in detail.

Effects of process parameters and die geometry on longitudinal welds quality in aluminum porthole die extrusion process

By using the rigid-visco-plasticity finite element method, the welding process of aluminum porthole die extrusion to form a tube was simulated based on Deform-3D software. The welding chamber height （H）, back dimension of die leg （D）, process velocity and initial billet temperature were used in FE simulations so as to determine the conditions in which better longitudinal welding quality can be obtained. According to K criterion, the local welding parameters such as welding pressure, effective stress and welding path length on the welding plane are linked to longitudinal welds quality. Simulation turns out that pressure-to-effective stress ratio （ρ/σ） and welding path length （L） are the key factors affecting the welding quality, Higher welding chamber best and sharper die leg give better welding quality. When H=10 mm and D=0.4 mm, the longitudinal welds have the best quality. Higher process velocity decreases welds quality. The proper velocity is 10 mm/s for this simulation. In a certain range, higher temperature is beneficial to the longitudinal welds. It is found that both 450 and 465℃ can satisfy the requirements of the longitudinal welds.

Outlining a stepwise,multi-parameter debris flow monitoring and warning system:an example of application in Aizi Valley,China

In recent years, the increasing frequency of debris flow demands enhanced effectiveness and efficiency of warning systems. Effective warning systems are essential not only from an economic point of view but are also considered as a frontline approach to alleviate hazards. Currently, the key issues are the imbalance between the limited lifespan of equipment, the relatively long period between the recurrences of such hazards, and the wide range of critical rainfall that trigger these disasters. This paper attempts to provide a stepwise multi-parameter debris flow warning system after taking into account the shortcomings observed in other warning systems. The whole system is divided into five stages. Differentwarning levels can be issued based on the critical rainfall thresholds. Monitoring starts when early warning is issued and it continues with debris flow near warning, triggering warning, movement warning and hazard warning stages. For early warning, historical archives of earthquake and drought are used to choose a debris flow-susceptible site for further monitoring. Secondly, weather forecasts provide an alert of possible near warning. Hazardous precipitation, model calculation and debris flow initiation tests, pore pressure sensors and water content sensors are combined to check the critical rainfall and to publically announce a triggering warning. In the final two stages, equipment such as rainfall gauges, flow stage sensors, vibration sensors, low sound sensors and infrasound meters are used to assess movement processes and issue hazardwarnings. In addition to these warnings, communitybased knowledge and information is also obtained and discussed in detail. The proposed stepwise, multiparameter debris flow monitoring and warning system has been applied in Aizi valley China which continuously monitors the debris flow activities.

Host Engineering for Red Electrophosphorescent Devices

In this paper, we demonstrate that controlled dopantoncentration is an essential issue for charge carriers transporting in red Phosphorescent Organic Light-Emitting Device （PHOLED）. Carriers transport via dopant molecules in the emitting layer with a single host, however, via both dopant and host molecules when their energy levels are well aligned. Conditions for reduced driving-voltage and enhanced efficiency of red PHOLED are obtained by employing a mixed host structure. A pure red PHOLED with color coordinates of （0.67, 0.33） has been realized by using only 4 wt% dopant, The device achieves 100 cd/cm2 at 2.9 V, with correspond- ing power efficiency of 9.3im/W and external quantum efficiency of 14.3%.

Effect of Cooking Method and Storage on the Quality of Minced Pork

Minced pork paste was mixed with cooked rice and noodle resulted in very popular traditional gourmet meal in Taiwan. The 100 ℃, 4 h was normally cooking condition for commercial business. However, the pressure cooker with higher cooking temperature （106 ℃, 116 ℃ and 121 ℃） and different cooking time were under studied in order to improving efficiency, quality and even cost down. The samples of neck pork substitute, cooking at 106℃, 100 rain; 116℃, 75 min; 121 ℃, 45 min with different pressure were perfomed the result as well as traditional 20% fat in ordinary formulation and cooking at 100℃ for 4 h. During storage, the products were taste acceptable for 4 weeks at 4 ℃, 4 months at - 18 ℃ and better than 1 day at 25 ℃ storage.

Numerical investigation for anisotropy of compressive strength of rock mass with multiple natural joints

Based on Rock Failure Process Analysis model RFPA2D, the evolutionary proc- esses of failure process of rock mass with multiple natural joints were simulated. Numeri- cal simulations show that anisotropy of compressive strength of jointed rock mass varies with the number of natural joints and inclination of natural joints. As the number of natural joints in rock mass increases, the anisotropy becomes less and less. It is justifiable to treat approximately rock mass containing six or more natural joints instead of four or more joints that was described in literature of Hoek and Brown as isotropy.

Critical Heat Flux with Subcooled Flowing Water in Tubes for Pressures from Atmosphere to Near-Critical Point

During last 45 years, two groups of the experimental data on critical heat flux were obtained in bare tubes, covering the pressures from atmosphere to near-critical point. One group of the data were obtained in the inner diameter of 2.32, 5.16, 8.05, 10.0 and 16.0 mm, respectively, with the ranges of pressure of 0.1-1.92 MPa, velocity of 1.47-23.3 m/s, local subcooling of 3.7-108.7 ℃ and heat flux of up to 38.3 MW/m2. Another group of the data were obtained in the inner diameter of 4.62, 7.98 and 10.89 mm, respectively, with the ranges of pressure of 1.7-20.6 MPa, mass flux of 454-4,055 kg/（m2.s） and inlet subcooling of 53-361 ℃. The results showed complicated effects of the pressure, mass flux, subcooling and diameter on the critical heat flux. They were formulated by two empirical correlations. A mechanistic model on the limit of heat transfer capability from the bubbly layer to the subcooled core was also proposed for all the results.

Online Monitoring the Products Quality by Measuring Cavity Pressure during Injection Molding

Injection molding is a complicated production technique for the manufacturing of polymer products. During injection molding, it＇s hard to predict molding quality; the injection molding parameters, such as mold temperature, melt temperature, packing pressure and packing time, affect the final properties of product. The cavity pressure is a significant key factor. Residual stress and injection molding weight are significantly affected by the cavity pressure. This study created an approach to predict weight of injection-molded by real-time online cavity pressure monitoring. This study uses a 6-inch with thickness lmm light guide panel and the largest area beneath the pressure curve of time as well as the maximum pressure as its characteristic. The upper and lower limits of the control are set to ＋2 standard deviations, and GUI （Graphical User Interface）-based LabVIEW software is used to perform calculation and analysis of the pressure curve. The results of the experiment show that the online internal cavity pressure monitoring system can effectively monitor the quality of the molded products. In 500 injection molding cycle tests, its error rate was less than 8%, whereas the deviation in mass of the molded products selected through the system＇s filtering process was successfully controlled to be within ±4%.

Flow Loss in Screens： A Fresh Look at Old Correlation

Pressure losses in flow components are generally characterized either by pressure loss coefficients or by discharge coefficients. The pressure drop for incompressible flow across a screen of fractional free area a is often calculated from widely used correlation provided in Perry＇s Handbook. This correlation was developed based on experimental work which have covered a wide range of fractional free area （a = 0.14 to 0.79）. The present work aims at validation for a flow in plain square mesh screen with a particular fractional free area （porosity, a） of 0.25 using CFD （Computational Fluid Dynamics） approach. The simulations are carried out for wide range of screen Reynolds number （Re = 0.1 to 105） covering both laminar and turbulent flow regimes. Initial simulations are carried out for incompressible fluid （water） and further extended to compressible fluid （air）. Discharge coefficients obtained from the simulations are compared with experimental values. Effect of compressibility on discharge coefficients is described.