基于Moldflow的微流控芯片收缩变形研究

用Moldflow模拟微流控芯片的注射成型过程可以发现潜在的设计缺陷,但Moldfolw的材料库并不能包括所有牌号的聚合物原料。以PMMA(CP51A)为测试对象,通过测试其黏度和PVT特性曲线,并以此为基础模拟其在X方向(宽度方向)和Y方向(长度方向)的收缩变形量,其模拟结果和实测收缩变形量两者获得较为一致结果。     

Modeling assembly systems with repetitive operations

Two methods are presented to model assembly systems where repetitive operations are integrated in one single machine following strictly planned sequences. The first method introduces an aggregate machine to approximate the original repetitive assembly machine so that the aggregate machine and the original machine have equivalent behaviors on processing time, machine reliability and maintainability. The second method transforms the repetitive assembly operations into a series of synchronized assembly/disassembly models so that the traditional assembly model can be applied to analyze such repetitive assembly machines. We systematically compare the accuracy of those two new models with that of a simulation model.     

Hole-injection properties of annealed polythiophene films to replace PEDOT–PSS in multilayered OLED systems

Hole-injection properties of annealed poly(alkoxy- and alkylthiophene) films in OLEDs were studied. Among them, annealed poly(3,3′-dihexyloxy-2,2′-bithiophene) (aPHOBT) film exhibited good hole-injection properties and a triple-layered OLED with the structure ITO/aPHOBT/PVK/Alq3/Mg–Ag (device I) showed much higher performance than a double-layered device without the aPHOBT layer (device II, ITO/PVK/Alq3/Mg–Ag). Device I was slightly inferior to a device having a PEDOT–PSS layer as the hole injector (device III, ITO/PEDOT– PSS/PVK/Alq3/Mg–Ag) in the low-intermediate region of the applied voltage (6–11 V), but gave comparable luminance to III when the applied voltage exceeded 11 V.     

Modeling of cast systems using smoothed-particle hydrodynamics

To understand and control the filling process for metals in high-pressure die casting and ingot casting, researchers have used new flow-simulation software for the modeling of mold filling. Smoothed-particle hydrodynamics (SPH) is a non-conventional computational fluid dynamics method that has been successfully applied to these problems. Due to its mesh-free nature, it can handle complex splashing free surface flows and the differential motion of multiple solid-casting equipment components relatively easily. The ability of SPH to predict the detailed filling patterns of real large-scale automotive die castings is demonstrated in this study, and the use of SPH simulation for wheel shape optimization in ingot casting based on minimizing oxide generation while increasing the throughput is also presented. Editor’s Note: A hypertext-enhanced version of this article is available on-line at www.tms.org/pubs/journals/JOM/0403/Cleary0403.html. For more information, contact, John F. Grandfield, CSIRO Manufacturing Science and Technology, Albert and Raglan Streets, Preston, VIC 3072, Australia; +61-3-9662-7832; fax +61-3-9662-7770; e-mail john.grandfield@csiro.au.     

聚合物微流控芯片模具制造关键技术研究进展

成型微通道型腔镶块的加工是聚合物微流控芯片模具制造的核心问题。介绍了国内外微流控芯片模具镶块加工技术的发展状况,分析了各种加工技术的适用范围与发展前景。研究表明,微流控芯片模具镶块制造技术对精密注射成型技术的发展具有一定的推动作用。     

Modeling of orders in autonomously controlled logistic systems

The paper extends the Autonomous Logistics Engineering Methodology (ALEM) by a deeper understanding of immaterial logistic objects to trigger manufacturing processes. Further, a hierarchical modeling concept is introduced to split customer orders logically into partial orders, which run directly at the shop floor level. Each partial order consists of certain manufacturing steps. The amendments enable adequate modeling of autonomous manufacturing processes. The research is a further step to integrate autonomously controlled processes in logistics.     

Modeling for driving systems of four-high rolling mill

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Modeling transient liquid phase bonding in multicomponent systems

Transient liquid phase (TLP) bonding is finding use in applications that require high thermal, electrical, chemical, and/or mechanical stability such as in electrical connectors, turbine vanes, and metal-matrix composites. To date, much work has been done to quantify the behavior of binary material combinations during the rate-limiting isothermal solidification step of TLP bonding. However, this model is not general enough to accurately predict the behavior of more complex multicomponent alloys and interlayers. A model is presented here that begins to account for the behavior in such systems.     

模内自动冲切浇口凝料机构的微流控芯片注射模设计

以具有微纳米结构的碟形微流控芯片为研究对象,设计了具有模内自动冲切浇口的注射成型模具。通过对碟形微流控芯片注射时熔体流动均匀性和散热翘曲分析,注射成型模具采用1模1腔的形式,注射浇口选择盘形浇口,冷却水道采用环形水道。为了提高生产效率,降低后续消除浇口对芯片造成的二次破坏,注射模中增加了模内自动切浇口凝料机构,以实现开模前完成浇口凝料切除,并用工具显微镜观察切口成型质量。     

Modeling linear guide systems with CoFEM: experimental validation

In this work a new efficient finite element (FE) model for rolling contact [RiBEM (rigid ball with equivalent material)] is shortly presented. The RiBEM model is used to efficiently compute the eigenmodes of a linear guide system. Experimental modal analysis of the real linear guide shows with 5?% error a very good correlation with the numerical results. Although the new contact model reduces computational time by more than ten times compared with the standard FE model, it is still too expensive for use within whole machine tool models. For this reason an equivalent, mesh independent and geometrically scalable model (rolling contact spring) based on the Hertz theory is introduced and also validated with the help of modal measurements. As a justification for the presented work, results with stiffness data from the manufacturer are also presented and less correlation with the experiment is found in this case.     

Function-based assembly: an application of MEMS-based assembly of rate gyroscopes

The assembly of MEMS-based devices in certain applications requires alignment within tolerances better than ±1μm. This standard has proven to be difficult to achieve consistently due to manufacturing and assembly errors. This article describes an active alignment process which incorporates the actual geometric parameters of the microelements as well as geometric constraints in order to determine the optimal location of the microelements in the assembly. The determination of this location guarantees optimal functionality of the device and helps achieve tight alignment tolerances without compromising the device design. The effectiveness of this approach is demonstrated in a micromachined vibrating rate gyroscope assembly. Simulation and measurements taken of the assembled rate gyroscope confirmed an assembly accuracy of better than ±1μm.     

Synthesis of nanoscale multilayered ZrN/W2N multilayered coatings by magnetron sputtering

ZrN/W₂N multilayered coatings with nanoscale modulation period in an ultra-high vacuum rf magnetron sputter chamber. XRD, SEM, Nano Indenter and profiler were employed to investigate the influence of modulation periods and working pressures on structural and mechanical properties of the coatings. The low-angle XRD pattern and cross-sectional SEM indicated a well-defined composition modulation and layer structure of the multilayered coating. All multilayered coatings revealed higher hardness than the rule-of-mixtures value of monolithic ZrN and W₂N coatings at different working pressures. The maximum hardness was up to 34 GPa. The multilayers obtained mixed polycrystalline textures of ZrN(111), W₂N(111), W₂N(200) and W₂N(311). 0.8 Pa was an optimum working pressure for mechanical property enhancement.     

Friction stir welding of multilayered steel

Abstract

This study investigates the mechanical properties and microstructure of friction stir butt welded high strength/ductility multilayered steel consisting of 15 alternating layers of SUS 301 austenitic stainless steel (eight layers) and SUS 420J2 martensitic stainless steel (seven layers) with a total thickness of 1·2 mm. With optimised welding parameters, defect free welds with an ultimate tensile strength (UTS) of 1240 MPa and a fracture elongation of 13% were accomplished. This corresponds to a joint efficiency of 90%. In this case, fracture occurred in the heat affected zone as a result of a very pronounced hardness drop in the martensitic layers resulting from the formation of a large amount of grain boundary precipitates, which were formed at temperatures ～750°C slightly below A_c1. By applying post-weld heat treatment, the hardness drop in the martensitic layers was removed and the tensile properties were enhanced to UTS of 1310 MPa (95% joint efficiency) and a fracture elongation of 22%.     

千层钢组织和力学性能分析

1. 兰州理工大学 有色金属先进加工与再利用省部共建国家重点实验室,兰州 730050;2. 钢铁研究总院,北京 100081     

Corrosion protection by multilayered conducting polymer coatings

Multilayered coatings, consisting of combinations of the conducting polymers polyaniline (Pani) and polypyrrole (Ppy), were galvanostatically deposited on to both carbon steel and stainless steel. Potentiodynamic polarisation was used to assess the ability of these copolymers to provide an effective barrier to corrosion in chloride environments. For carbon steel the performance of these multilayered coatings on carbon steel were not sufficiently better than for single Pani coatings to justify their more complicated deposition procedures. However, in the case of stainless steels the new multilayered coatings proved to be significantly better than previously reported single Pani coatings, especially at protecting against pitting corrosion. It was found that the degree of protection was a function of the deposition order of the copolymer, with films consisting of a Pani layer over the top of a Ppy layer yielding the best results. Scanning electronic microscopy observations and adhesion measurements, along with the electrochemical data suggested that the ability of a conducting polymer film to act as electronic and chemical barriers were more important in providing corrosion protection than its ability to act as a physical barrier.     

Creep deformation in multilayered and microlaminate materials

Multilayered and microlaminate foils offer a convenient specimen geometry for studying creep deformation in fine-grained materials. Multilayered foils can have large total thicknesses, allowing for ease of handling and testing, while being composed of very small grains that can be controlled and maintained in the individual layers. Uniaxial creep studies have been performed on two model systems, metal/metal multilayers and metal/intermetallic multilayers, revealing both conventional and non-conventional behavior in these materials. These two studies demonstrate the benefits of studying creep deformation of multilayer materials through uniaxial tensile tests of free-standing specimens, specifically the ability independently to vary temperature, applied stress, strain and grain size. Such techniques can be applied to a variety of metal/metal and metal/intermetallic systems and enable investigation into the high-temperature deformation of fine-grained materials. For more information, contact A.C. Lewis, The Johns Hopkins University, Department of Materials Science and Engineering, Baltimore, MD 21218; lewisac@jhu.edu.