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51.
精密陶瓷部件近净成型技术的发展 总被引:5,自引:0,他引:5
重点介绍了近十年发展起来的陶瓷部件的近净成型技术 ,主要包括直接凝固注模成型、凝胶注模成型、陶瓷注射成型、陶瓷无模成型和微注入成型。对这些新的成型方法的原理、工艺过程及应用特点进行了较全面的分析与比较。 相似文献
52.
Combined shape and sizing optimization of truss structures 总被引:1,自引:0,他引:1
In this paper, an evolutionary optimization method is presented for weight minimum problem of a 3-dimensional truss structure
in terms of nodal coordinates and element cross-sectional areas. The structure is subject to stress, local buckling and displacement
constraints. Two types of design variables with different natures are optimized separately: (1) a fully stressed design (FSD)
and scaling techniques are applied to sizing variables and (2) the evolutionary node shift method is applied to shape variables.
Alternating procedure is utilized to couple the two types of variables and to combine the results. The optimum solution is
achieved gradually from the initial configuration design. Two typical truss structures are examined to illustrate the validity
of the method.
Received: 22 October 2001 / Accepted: 04 June 2002
This research work is supported by the National Natural Science Foundation of China under the guarantees no. 10072050 and
10172072, respectively. 相似文献
53.
A. Moran C. Madden R. Rebis R. Payne M. A. Matteson 《Journal of Thermal Spray Technology》1994,3(2):197-198
Over the past five years, the Annapolis Detachment, Carderock Division, Naval Surface Warfare Center (formerly David Taylor
Research Center) has established a state- of- the- art spray forming facility for the study and exploitation of this near
net shape manufacturing process. Spray forming is a single step gas atomization/deposition process which yields ferrous and
nonferrous, near final shape, near fully dense preforms that has proven to be a viable and cost effective alternative to conventional
metalworking technology for the production of material preforms with properties surpassing those of their cast and wrought
counterparts. Current programs at Carderock Divison Naval Surface Warfare Center are aimed at optimization of the process,
certification of the spray formed products and industrialization of the technology. 相似文献
54.
The extraction of nitrogenous material from Brewers' spent grain (BSG) by solvents (water, sodium chloride solution, aqueous alcohol, acidic and alkaline solutions) commonly used to extract cereal proteins, resulted in the relatively low (0·2 to 8·5%) recovery of the total nitrogen. The recovery of nitrogenous material by the use of aqueous alkaline solutions was increased from 3–4% to 41% when the BSG was subjected to cellulase incubation prior to extraction. Approximately 75% of the nitrogen was solubilized with trifluoracetic acid. Detergent solutions (acid, neutral) solubilized more than 80% of the total nitrogen of the BSG. The low solubility of the nitrogenous constituents by conventional protein solvents could be the result of association between cellulosic material and protein. 相似文献
55.
56.
Relative grain boundary energies can be simply related to true dihedral angles, which are the angles between grain boundary planes meeting at triple edges in polycrystals. Some limited efforts in the measurement of true dihedral angles have used the technique of serial sectioning, which is usually cumbersome and time consuming. In this study the three‐dimensional probe called the ‘disector’ has been employed to evaluate true dihedral angles. This probe, combined with automated image processing, introduces precision as well as efficiency, overcomes the disadvantages of the two‐dimensional probe and is far less tedious and less complicated than serial sectioning. It is shown that the technique is relatively simple and therefore can be applied to obtain a significantly large and accurate statistical sample of true dihedral angles. The application of this method is demonstrated by evaluating the triple junction geometry and the associated relative grain boundary energies in polycrystalline 316L austenitic stainless steel. 相似文献
57.
ECAP细化晶粒法的仿真与分析 总被引:7,自引:0,他引:7
ECAP(Equal Channel Angular Extrusion)方法,是实现材料纯剪切变形的有效方法。本文采用有限元(FEA)分析软件ANSYS对Al的挤压过程进行仿真与分析。分析结果表明:外切角Φ、圆角半径、试样与凹模之间的摩擦系数、凹模本身的特性(如弹性模量、泊松比等)等等,对材料的变形量都有不同程度的影响。 相似文献
58.
38MnSiVS5 steel is similar to 38MnVS6 steel (EN), the difference being the addition of a small Ti content. Typical Ti and Al contents in the chemical composition of 38MnSiVS5 steel are Ti=0.020 and Al=0.035 mass%. Both elements combine easily with nitrogen, especially Ti, and it has been observed that relatively high Al levels are harmful for austenite grain size control at reheating temperatures. In this work 38MnSiVS5 steel is used to manufacture a large number of castings, varying only the Ti and Al contents and obtaining ingots with a different Ti/Al ratio in each case. The results show that abnormal growth of the austenitic grain occurs irrespective of the Ti and Al contents, due fundamentally to the partial dissolution and coarsening of TiN precipitates. However, the steels with high Al contents present worse behaviour due to the formation of a second type of precipitates, namely AIN, which quickly dissolve between 1000 and 1100°C, causing a drastic decline in local pinning forces that gives rise to more pronounced abnormal growth of the affected grains. 相似文献
59.
60.