TC4铣削切屑形态与表面形貌特征

目的 对TC4铣削过程中锯齿状切屑的形成与对应产生的加工表面形貌特征进行研究,掌握钛合金TC4高速铣削加工切屑形态随铣削速度的变化规律,从而提高加工表面质量和效率。方法 基于有限元软件,建立钛合金TC4二维变厚度切削模型,通过仿真和铣削试验分析铣削速度对切屑形态的影响规律。利用超景深显微镜和PS50表面轮廓仪对TC4铣削过程中形成的切屑形态及工件加工表面形貌进行观测和分析,确定铣削加工TC4过程中铣削速度与切屑形态、工件表面形貌和表面粗糙度之间的关系。结果 铣削试验验证得出铣削力仿真值与试验值最大误差为9.86%,验证了二维变厚度切削模型的准确性。随着铣削速度从40 m/min增大到120 m/min,切屑形态由带状转变为锯齿状,且铣削力逐渐减小。同时,铣削速度由80 m/min增大到240 m/min时,切屑的锯齿化系数和剪切带内的剪切角均增大,而剪切带间距减小,TC4加工表面波纹加深、波纹间距变宽,并且伴随有大量韧窝出现,导致表面粗糙度值增大。结论 掌握锯齿状切屑几何特征与工件表面形貌随铣削速度的变化规律,以便在铣削加工TC4过程中对锯齿状切屑进行控制,对于提高工件加工表面质量和加...     

Application of titanium machining chips in welding consumables for wear-resistant hardfacing

Equipment of sugar cane plants and mineral extraction are submitted to severe abrasive wear conditions. Welded hardfacings are usually applied to repair this kind of damage, where commercial chromium/carbon-rich welding consumables have usually been employed. In the present work we investigated the microstructure of experimental hardfacings made by addition of residues (chips) collected from the machining of ASTM F67 (unalloyed Ti, grade 4) alloy. Mixtures with different carbide-formers (Cr/Nb ferro-alloys) were also tested. Two layers of ‘pure’ chips (Ti), chips plus Fe–Cr (Ti–Cr), and chips plus Fe–Nb (Ti–Nb) were applied on low-carbon steel specimens by the GTAW/TIG process. The microstructure of hardfacing layers was observed by optical and scanning electron microscopy (SEM) equipped with EDS microanalysis. The microstructural characterization has determined that carbide distributions change significantly with the chemical nature of the hardfacing. SEM observations coupled with EDS microanalysis have confirmed the formation of complex carbides within the metal weld, whose stoichiometry was determined by X-ray diffraction (XRD) analysis. Mixed carbides of MC type and some cementite have been found. As a result it was suggested that use of ASTM F67 chips as carbide formers for composition of welding consumables can contribute to improved wear resistance of hardfacings, if compared with traditional chromium-based hardfacings.     

基于钉书机钣金外壳的级进模设计

分析了订书机钣金外壳零件的结构特点和冲压工艺性,将成形难度锁定在产品侧面的小孔及小孔沉头,结合生产要求,提出了采用14工位的级进模工艺方案,依方案确定级进模的料带图。根据成形难度,重点介绍了该模具滑块与侧冲针的结构,将滑块的斜楔设置在滑块的两侧,将侧冲针的头部设计为圆锥形状,锥形起定位作用,使侧孔的形状稳定。在冲侧孔时,合理地利用钣金外壳的回弹,使产品侧边小孔的沉头在回弹作用下脱离凸模的凹陷位,从而实现顺利脱模,并用吸气的方式实现排屑。最后,绘制模具装配图,并阐述其工作过程。结果表明:钉书机钣金外壳件采用一套级进模成形,可连续进行冲孔、折弯、压凸、成形等工序,实现高效率的冲压生产,为同类制件的生产提供了一定的理论指导和技术支撑。     

Asymptotic Analysis of Quick Service Systems with Nonhomogeneous Structure

An asymptotic distribution of the instant of first failure in models with quick service, structural heterogeneity, and variable service discipline is investigated.     

Architectural and Basic Circuit Considerations for a Flexible 128 × 128 Mixed-Signal SIMD Vision Chip

From a system level perspective, this paper presents a 128 × 128 flexible and reconfigurable Focal-Plane Analog Programmable Array Processor, which has been designed as a single chip in a 0.35 m standard digital 1P-5M CMOS technology. The core processing array has been designed to achieve high-speed of operation and large-enough accuracy (7 bits) with low power consumption. The chip includes on-chip program memory to allow for the execution of complex, sequential and/or bifurcation flow image processing algorithms. It also includes the structures and circuits needed to guarantee its embedding into conventional digital hosting systems: external data interchange and control are completely digital. The chip contains close to four million transistors, 90% of them working in analog mode. The chip features up to 330 GOPs (Giga Operations per second), and uses the power supply (180 GOP/Joule) and the silicon area (3.8 GOPS/mm²) efficiently, and is able to maintain VGA processing throughputs of 100 Frames/s with about 10–20 basic image processing tasks on each frame.     

Optimization of Blanching for Crispness of Banana Chips Using Response Surface Methodology

Whole green bananas were blanched in water at 50, 60, 70, 80, 90, and 100°C for 2, 15, and 30 min using a factorial design then peeled, sliced and fried in oil to make chips. Crispness was measured using a bending-snapping test in the TA.XT2 Texture Analyzer. Significant interactions were found between blanch time and temperature and crispness of chips. A second experiment was then performed using a central composite design and blanch temperatures from 41.7 to 98.3°C. Response surface analysis predicted that crispiest chips should be produced at blanching conditions of 69°C and 22 min.     

Evolvable hardware techniques for on-chip automated reconfiguration of programmable devices

While complete automated design is a harder problem than computer-assisted design, automated hardware reconfiguration is an even more challenging problem, because it needs to adjust to limited resources and various factors, such as noise and parasitic capacitance, a resistance and inductance. This paper presents some experimental results of on-chip automated design and reconfiguration using evolvable hardware techniques. It describes a stand-alone board level evolvable system, and its use to demonstrate on-chip synthesis of new circuits in only a few seconds. The experiments presented here indicate a recovery capability in the case of extreme environmental conditions, such as extreme temperatures, that adversely affect electronics. Some of the difficulties of dealing with the real hardware are exposed, as well as challenges more generally related to automated evolution of complex electronic systems.The work described in this paper was performed at the Center for Integrated Space Microsystems, Jet Propulsion Laboratory, California Institute of Technology and was sponsored by the Defense Advanced Research Projects Agency and by the National Aeronautics and Space Administration.     

P2P视频在人才招聘网站上的应用

简要描述了传统人才招聘网站的方式;从招聘的流程、环节、方式等方面,从现实的情况提出了“P2P视频优化的即时沟通方式”;重点介绍P2P即时通讯的视频方式对网站优化所起到的作用和优点;通过对P2P视频在网站上的优点的分析,说明分P2P的视频应用是完全可行的,有助于企业、人才、网站三方面优化和提高效率。     

钢屑中铜的测定

介绍了钢屑中铜的测定方法。火焰原子吸收法越来越多地应用于化学分析中，用其测定钢屑中的铜，操作步骤简便．准确度高，适用性强。