T型管液压成形过程的有限元分析

应用动态显式有限元法,建立了T型管液压成形分析模型,对不同加载条件下的模拟结果进行对比,分析了轴向载荷的作用,探讨了最佳载荷曲线的确立原则.     

On some new operations in soft module theory

In this paper, we introduce the notions of sum and direct sum of soft submodules, small soft submodules and radical of a soft module. Moreover, we obtain basic properties of such soft submodules.     

Description and composition of bio-inspired design patterns: a complete overview

In the last decade, bio-inspired self-organising mechanisms have been applied to different domains, achieving results beyond traditional approaches. However, researchers usually use these mechanisms in an ad-hoc manner. In this way, their interpretation, definition, boundary (i.e. when one mechanism stops, and when another starts), and implementation typically vary in the existing literature, thus preventing these mechanisms from being applied clearly and systematically to solve recurrent problems. To ease engineering of artificial bio-inspired systems, this paper describes a catalogue of bio-inspired mechanisms in terms of modular and reusable design patterns organised into different layers. This catalogue uniformly frames and classifies a variety of different patterns. Additionally, this paper places the design patterns inside existing self-organising methodologies and hints for selecting and using a design pattern.     

Capillary self-alignment of polygonal chips: a generalization for the shift-restoring force

Capillary-driven self-alignment using droplets is currently extensively investigated for self-assembly and microassembly technology. In this technique, surface tension forces associated to capillary pinning create restoring forces and torques that tend to bring the moving part into the alignment. So far, most studies have addressed the problem of square chip alignment on a dedicated patch of a wafer, aiming to achieve 3D microelectronics. In this study, we investigate the shift-restoring forces for more complex moving parts such as regular—convex and non-convex—polygons and regular polygons with regular polygonal cavities. A closed-form approximate expression is derived for each of these polygonal geometries; this expression agrees with the numerical results obtained with the Surface Evolver software. For small shifts, it is found that the restoring force does not depend on the shift direction or on the polygonal shape. In order to tackle the problem of microsystem packaging, an extension of the theory is done for polygonal shapes pierced with connection vias (channels), and a closed form of the shift-restoring force is derived for these geometries and again checked against the numerical model. In this case, the restoring force depends on the shift direction. Finally, a non-dimensional number, the shift number, is proposed that indicates the isotropic or anisotropic behavior of the chip according to the shift direction.     

Analysis of the gate current as a suitable indicator for FET degradation under nonlinear dynamic regime

Electron device degradation, although not directly accounted for, represents a key issue in microwave circuit design. This is especially true when the particular applications involved (e.g., satellite, military, consumer) do not allow or strongly discourage any kind of maintenance. As a matter of fact, in order to account for device degradation in circuit design, a suitable electron device model is needed which is able to predict the performance degradation as a function of the actual electrical regime involved in the device operation. Such a kind of model is not available in literature. In this paper, quantitative results are provided for device degradation indicators which correlate DC and RF stress experiments. These results can be considered an important step toward the definition of a nonlinear model accounting for device degradation.     

Study on Microstructure and Mechanical Properties of Hot Rolled Low Silicon Containing Phosphorus TRIP Steel

The effects of final air cooling temperature on the microstructure and mechanical properties of hot rolled 0.2C-1.9Mn-0.5Si-0.08P TRIP steel were studied by utilizing OM, SEM, TEM and tensile tests. Experimental results showed that in the multiphase microstructure of the investigated steel when the finish rolling temperature was about 820 ℃ and the final air cooling temperature was in the range of 630-700 ℃, the grain size of most of ferrite was finer (about 4 μm) and which had higher dislocation density, t...     

Modification of Fe and Al elemental powders’ sintering with addition of magnesium and magnesium hydride

An attempt to modify sintering of iron and aluminium elemental powders with use of small additions of Mg and MgH₂ was presented in this paper. The kinetics of such modified sintering was investigated using DSC technique, XRD analysis and SEM observations. Significant changes in the mechanism of exothermal formation reaction of Fe–Al intermetallic phases in compositions doped with magnesium and its hydride was observed. Initiation temperature of Self-propagating High-temperature Synthesis (SHS) reaction was pronouncedly shifted to lower value as compared with undoped composition. Influence of additions on the SHS reaction kinetics parameters was also calculated with use of the JMA model and changes of the Avrami exponent value of specific phase formation was noticed. Positive effect of MgH₂ addition on partial homogeneity of final product was also studied.     

Microstructure of electrochemical micromachining using inert metal mask

Electrochemical micromachining (EMM) has been gaining popularity as an alternative method to fabricate microstructure. A method of EMM is proposed to produce microhole array or micro-dimple array, in which a patterned inert metal mask (platinum plate) is closely attached to workpiece (anode), not bonded to the anode. When voltage is applied across the anode and the cathode over which electrolyte flows at a high speed, the patterns in the mask are transferred to the anode, and microstructures are produced. A mathematical model to describe the actual machining process is established. By considering the effect of nonlinear electrolyte, the parametric finite element method is adopted to simulate and numerically analyze the erosion process. Some experiments are performed to verify the proposed model.     

灵活性住宅类型

欧洲受到当今全球性生态和经济的挑战,可持续性和适应性的建筑结构设计概念再次变得愈发重要。此外,个性化的要求、人口结构的变化、民族的多样化以及向灵活工作方式的过渡也激发了对适应性住房需求的日益增长。自20世纪80年代末以来,灵活住宅的范围在欧洲显著扩大,并产生了多种类型：从功能开放的楼层平面、活动墙体的楼层平面以及各种组合类型,到前卫的空间场景、实验性高科技适应结构以及开放功能计划的建筑类型。建立起一种实现灵活性之方法的框架,并介绍了几个具有创新性的案例。     

Error evaluation on experimental stress–strain curve obtained from tube bulging test

To get precise material data for advanced numerical modelling of tube hydroforming process, the tube bulging test is recommended. Stresses and strains in the tube cannot be evaluated easily and several approaches have been proposed. A review is proposed and points out their advantages and drawbacks.