定向结晶时高温合金组织控制的工艺前景EI

报道了俄国航空材料研究院(ВИАМ)在定向单晶高温合金组织控制方面的最新研究成果,例如,利用高速定向结晶工艺创造具有单晶组织的宽弦叶片,以及制造前后缘为规定位相的单晶,而在叶身中部为细柱状定向结晶组织的复合组织叶片。这些新工艺提高了材料的工作能力和发动机寿命。     

Contact interaction of double titanium and chromium diboride with Fe-Cr alloys

The kinetics of wetting double titanium and chromium diboride by iron-based alloys with different chromium content is studied. It is shown that contact angles are formed in such systems over the range 0–10°. The energy parameters of wetting are calculated. It is established that chromium as a surface-active element promotes Fe-Cr alloy spreading on the diboride surface. The microstructure of the interaction area is studied. It is shown that terminal solid solutions and eutectics are formed in the TiCrB₂-(Fe-Cr) system. The optimum compositions of the metallic binder are determined for TiCrB₂-based composite materials. __________ Translated from Poroshkovaya Metallurgiya, Vol. 46, No. 1–2(453), pp. 109–115, 2007     

Surface and normal ensembles for surface reconstruction

The majority of the existing techniques for surface reconstruction and the closely related problem of normal reconstruction are deterministic. Their main advantages are the speed and, given a reasonably good initial input, the high quality of the reconstructed surfaces. Nevertheless, their deterministic nature may hinder them from effectively handling incomplete data with noise and outliers. An ensemble is a statistical technique which can improve the performance of deterministic algorithms by putting them into a statistics based probabilistic setting. In this paper, we study the suitability of ensembles in normal and surface reconstruction. We experimented with a widely used normal reconstruction technique [Hoppe H, DeRose T, Duchamp T, McDonald J, Stuetzle W. Surface reconstruction from unorganized points. Computer Graphics 1992;71-8] and Multi-level Partitions of Unity implicits for surface reconstruction [Ohtake Y, Belyaev A, Alexa M, Turk G, Seidel H-P. Multi-level partition of unity implicits. ACM Transactions on Graphics 2003;22(3):463-70], showing that normal and surface ensembles can successfully be combined to handle noisy point sets.     

Constraint-based beautification and dimensioning of 3D polyhedral models reconstructed from 2D sketches

3D models reconstructed from 2D sketches are inaccurate because of the inherent inaccuracies in the input and the reconstruction method. It is therefore necessary to “beautify” them before use in CAD systems. We present a method that detects geometric constraints, such as parallel and orthogonal faces, present in the reconstructed model and then selects a subset that constrains the object sufficiently and consistently. The subset selection algorithm first prioritizes the constraints depending on their type and then uses a novel method, based on quasi-Newton optimization, to detect and eliminate redundant and inconsistent constraints. The remaining constraints then define the dimensions of the model fully and consistently. Results from our implementation show that the method can beautify and dimension recovered 3D models correctly at acceptable speed.     

20CrMo棒材带状组织的控制研究

通过Gleeble-1500热模拟机对20CrMo轧材精轧阶段轧制过程及冷却过程的模拟,研究了终轧温度、冷却速度对室温组织的影响,分析了形成带状组织的条件,最终得出了理想室温组织的终轧温度和冷却速度。     

钻井工程固井胶结界面研究现状

固井质量问题在石油勘探开发中备受关注，对特殊工艺井钻井、油水井开采寿命和勘探开发效益有直接的影响。对固井胶结界面的研究是从根本上提高固井质量的一项基础性研究工作。为了推动固井胶结界面研究工作的开展，分析了国内外近年来有关固井界面研究的文献，阐述了开展固井胶结界面基础研究工作的意义，着重分析了这一研究领域目前所采用的研究方法，以及提高固井界面胶结强度的主要途径。在分析文献的基础上，提出今后深入开展固井界面研究工作的重点是：1）继续完善研究方法；2）重视动态研究；3）从胶结界面的微观结构和钻井工程整体系统的角度开展研究工作；4）注重改善胶结界面水化产物的微观结构和钻井工作液之间的协调增强作用。     

Optimal control of nonlinear systems to given orbits

Using optimal control techniques we derive and demonstrate the use of an explicit single-step control method for directing a nonlinear system to a target orbit and keeping it there. We require that control values remain near the uncontrolled settings. The full nonlinearity of the problem in state space variables is retained. The “one-step” of the control is typically a composition of known or learned maps over (a) the time required to learn the state, (b) the time to compute the control and (c) the time to apply the control. No special targeting is required, yet the time to control is quite rapid. Working with the dynamics of a well-studied nonlinear electrical circuit, we show how this method works efficiently and accurately in two situations: when the known circuit equations are used, and when control is performed only on a Poincaré section of the reconstructed phase space. In each case, because the control rule is known analytically, the control strategy is computationally efficient while retaining high accuracy. The target locations on the selected target trajectory at each control stage are determined dynamically by the initial conditions and the system dynamics, and the target trajectory is an approximation to an unstable periodic orbit of the uncontrolled system. A linear stability analysis shows that dissipation in the dynamical system is essential for reaching a controllable state.     

三维目标旋转畸变不变光学相关滤波器组的设计

研究了三维目标旋转畸变不变光学相关滤波器组的设计原理，完成了滤波器组参数的计算和编码，以及光学相关识别的计算机模拟。     

添加高速钢粉对烧结钢组织与性能的影响

研究了添加高速钢粉对烧结钢组织与性能的影响。实验结果表明，含２０％高速钢的烧结钢综合力学性能最好；添加高速钢粉能导致烧结钢密度减小的冲击韧性降低，当高速钢含量增中时，硬度随之增加，烧结钢中残余奥氏体和马氏体的含量与高速钢的含量呈线性关系。烧结钢中的马氏体显微硬度很高，它主要原高速钢粒子和原铁粒子的连接区域形成。     

Comparison of interfaces in Ti composites reinforced with uncoated and TiB2/C-coated SiC fibres

Interfaces play an important role in determining the mechanical properties of composite materials. The interfaces established between a titanium-alloy matrix (Ti-6Al-4V) and uncoated and TiB₂/C-coated SiC fibres are analysed by scanning electron microscopy, transmission electron microscopy and X-ray techniques. Emphasis is placed upon the interfacial morphology and microstructure, identification of reaction products, and the stability of the coating layer. Complex multi-reaction layers are observed frequently in the interfacial zones. Previous, often contradictory, reports about the interlayers are reviewed. Experimental observation demonstrates that the type and distribution of interlayers vary in a given system, due to prolonged treatment of the samples at temperature. The formation and distribution of the interlayers are discussed further, with respect to these and previous findings. Methods of reducing interfacial reactivity are discussed.