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简要介绍世界几种主要薄板坯连铸工艺。着重叙述应用大型通用商业软件MSC.MARC。模拟液芯压下时铸坯的变形,确定最佳压下方案的有限元分析,液芯压下应该在结晶器出口处及二冷区扇形段开始部分进行,这样能减小铸坯的应变。 相似文献
3.
挤压力对晶体生长速度及枝晶间距的影响 总被引:4,自引:4,他引:0
研究了挤压铸造时挤压力对宏观晶体生长速度的影响,给出了晶体生长速度表达式。结果表明:挤压力对合金宏观晶体生长速度的影响除与合金成分有关外,在某些挤压条件下,当形核率的增加幅度超过长大速度时,则挤压力可使宏观晶粒细化;反之,会使宏观晶粒变粗。随着挤压力的提高,合金凝固速度加快,一次枝晶间距和二次枝晶间距都随之减小,从而细化了树枝晶。 相似文献
4.
通过测试连铸二冷喷嘴性能,对比同型号喷嘴使用前后两种状态下特性参数,分析了喷嘴参数变化的原因。提出了对使用中的喷嘴特性进行检测与校核的建议,以确保喷嘴特性满足铸坯二冷工艺条件,保证铸坯质量。 相似文献
5.
Critical Shear Stress of Bimodal Sediment in Sand-Gravel Rivers 总被引:1,自引:0,他引:1
A new model for the critical shear stress and the transport of graded sediment is presented. The model is based on the size distribution of the bed surface and can be used to compute sediment transport rates in numerical simulations with an active layer model. This model makes a distinction between unimodal and bimodal sediments. It is assumed that all size fractions of unimodal sediments have the same critical shear stress while there is selective transport for the gravel fractions of bimodal sediments. A recently published laboratory transport data set is used to calibrate our model. 相似文献
6.
Robert Tuttle 《Journal of Failure Analysis and Prevention》2007,7(4):247-249
The investigation described in this article examined a cast aluminum head used in a high performance (drag racing) application.
These engine heads had been failing within a few seconds of startup. A sample head was examined to determine the cause. Visual
inspection found two cracks on the exhaust side of the head. One crack initiated at the bottom of a spark plug well. The head
was then sectioned for metallographic examination and fracture analysis. Metallographic examination revealed a large number
of shrinkage pores throughout the casting. The fracture surface intersected many of these shrinkage pores. A significantly
sized pore was located near the bottom of the suspect spark plug well near a stress-concentrating feature. This pore acted
as the crack-initiating defect, which caused the engine head to fail. 相似文献
7.
Bedload Transport in Alluvial Channels 总被引:1,自引:0,他引:1
Miguel Bravo-Espinosa W. R. Osterkamp Vicente L. Lopes 《Canadian Metallurgical Quarterly》2003,129(10):783-795
Hydraulic, sediment, land-use, and rock-erosivity data of 22 alluvial streams were used to evaluate conditions of bedload transport and the performance of selected bedload-transport equations. Transport categories of transport-limited (TL), partially transport-limited (PTL), and supply-limited (SL) were identified by a semiquantitative approach that considers hydraulic constraints on sediment movement and the processes that control sediment availability at the basin scale. Equations by Parker et al. in 1982, Schoklitsch in 1962, and Meyer-Peter and Muller in 1948 adequately predicted sediment transport in channels with TL condition, whereas the equations of Bagnold in 1980, and Schoklitsch, in 1962, performed well for PTL and SL conditions. Overall, the equation of Schoklitsch predicted well the measured bedload data for eight of 22 streams, and the Bagnold equation predicted the measured data in seven streams. 相似文献
9.
The results of applying enhanced-surface-area packed-bed (ESAP) electrodes in electrogenerative SO2/O2 cells are reported to illustrate their utility and potential applications. Mathematical analysis with parameters pertinent
to the experimental conditions shows that all electrocatalyst sites in these electrodes are expected to be uniformly utilized
for electrochemical SO2 oxidation. Experimental results showed that ESAP electrodes (1 mg Pt/cm2) could provide at least 5 times higher SO2 conversion at given cell voltages than graphite sheet electrodes (1.5 mg Pt/cm2). 相似文献
10.
《Drying Technology》2007,25(5):831-839
Residence time distributions for an aqueous solution of 10% sodium chloride in a spouted bed dryer of inert particles were determined using the stimulus-response technique. Glass and polyethylene beads with diameters 2.6 and 3.4 mm were used as inert bodies in a cylindrical column of 14.0 cm diameter and 60° conical base. The effects of inert bodies load, air, and paste flow rates on the mean residence times and RTD were determined following 23 factorial designs. The RTD could be correlated to the perfect mixing cell model with R2 varying from 0.8684 to 0.9815. The mean residence times in CSBD varied from 10.8 to 13.9 and 10.7 to 13.3 min for glass and polyethylene beads, respectively. For both inert particles, mean residence times increased with bed height and decreased with paste feed rates. Also, terms of interaction among the factors were significant in some cases, showing a complex behavior of paste residence times. Equations obtained by response surface regression could predict mean residence times on glass and polyethylene beads with deviations lower than ±10%. 相似文献