金属粉末注射成形工艺质量控制和缺陷分析

本文分析了金属粉末注射成形工艺过程（金属粉末注射成形坯、注射成形坯的脱黏、烧结）产生的质量缺陷、采取的对策及该成形技术在汽车工业中的应用前景.     

基于电磁动态塑化理论的销钉挤出机混炼过程仿真

借助于计算流体动力学软件POLYFLOW,基于电磁动态塑化理论建立了销钉混炼元件和单螺杆混炼元件的简化几何模型,并对其进行数值模拟仿真,对比分析两种混炼元件在稳态与动态加工成形条件下的混炼性能。结果表明:销钉混炼元件比单螺杆混炼元件累计停留时间长、分离尺度小、瞬时混合效率高,引入振动场可以强化其熔体颗粒分流和重排,改善熔体流动状态,提高其流道物料混炼性能;同时,用实验验证了引入振动力场有利于减小物料粒子粒径。研究结果为电磁动态塑化理论应用于混炼设备的设计研发提供了参考和借鉴。     

多层模板粉末压制设备及其液压系统的研制

粉末压制设备是影响金属粉末压坯质量的一个重要因素，为了成形密度均匀无裂纹的金属粉末压坯，本文在分析国内外现有粉末压制设备特点的基础上，设计和制造用于成形具有上二台面和下三台面复杂粉末冶金零件的多层模板粉末压制设备，并根据压制工艺要求设计了适用于多层模板粉末压制设备的液压系统，该系统采用集成油缸驱动多层模架，多层模冲均能独立运动，实现压制复杂的多台面压坯的动作要求．起到改善压坯密度均匀性，避免裂纹产生的作用。     

金属粉末流动温压成形的特点及其技术问题分析

介绍了金属粉末流动温压成形技术的发展动态及其技术特点，分析了流动温压成形的关键技术问题。流动温压成形的关键是提高粉末的流动性．其实现方法有三种．一是向粉末中加入精细粉末．二是加入比传统粉束冶金工艺稍多但比金属粉末注射成形少得多的特殊粘结剂和润滑剂，三是加入表面活化剂或增塑剂．以提高将末体的流变性能。流动温压成形结合了常规温压成形和金属注射成形的优点，既克服了传统粉末冶金技术在成形方面的不足．又避免了注射成形技术的高成本．具有广阔的应用前景。     

塑料注射成形全过程计算机模拟

对塑料注射成形流动、保压和冷却过程中热传递行为进行计算机模拟，通过迭代求解耦合参数单元的温度值、实现注民形流动、保压和冷却全过程的耦合迭代分析。     

微结构与微型零件的微注射成形

设计并制作了微注射成形模具，采用光刻、离子蚀刻工艺相结合在硅片上制得了微零件型腔、流道及浇口。利用该模具在微型注射机上进行了聚丙烯微注射成形实验，注射成形了微结构零件及独立的微型零件，其中最小微结构部分是直径50μm的微圆柱，最小独立的微型零件是直径300μm、厚300μm的微圆片。分析了模具温度、注射压力及保压时间对微注射成形的影响，其中模具温度影响最大，注射压力、保压时间的影响次之。     

振动力场强化单螺杆挤出固体输送的离散单元法模拟

将岩石力学中的研究方法——离散单元法引入塑料挤出固体输送研究中，并建立了固体输送段的离散输送模型。该模型可以从微观上分析聚合物颗粒在挤出过程中的受力和运动，也可以从宏观上描述整个颗粒体系的运动规律。模型能体现振动力场对强化单螺杆挤出固体输送的影响，反映电磁动态挤出机固体输送段的输送规律，为新型设备的设计应用提供理论支持。     

名词解释

<正>注射成形注射成形又称为注塑成形,是热塑性塑料成形的主要方法。注射成形时,将粒状或粉状的塑料加入到注射机的料斗,在注射机内塑料受热熔融并使之保持流动状态,然后在一定压力下注入闭合的模具,经冷却定型后,熔融的塑料就固化成为所需的塑件。注射过程一般包括:加料、塑化、充模、保压、倒流、冷却和脱模等步骤。注射成形是热塑性塑料成形的一种主要方法。它能一次成形形状复杂、尺寸精确、带有金属或非金属嵌件的塑件。注射成形的成形周期短、生产率高、易实现自动化生产。到目     

液压脉振注射机塑化过程螺杆动态特性分析

采用液压激振力为驱动力的运动机构方法,将脉动压力引入到注塑成型熔融塑化整个过程。简介了塑化部分结构,分析了螺杆在动态塑化时的轴向受力状况,利用集中质量的方法建立了塑化过程广义螺杆轴向动态响应的物理和数学模型,研究了此种振动装置在塑化过程中螺杆的动态响应。结果表明,在工作频率范围内,随着振动频率增大,螺杆响应振幅减小,低频率激励的振幅放大系数高于高频率激励振幅放大系数,实验结果与理论分析相一致。     

小型复杂零件量产新工艺

1．金属粉末注射成形简介 金属粉末注射成形技术（Metal Powder Injection Molding，简称MIM）是将注塑成形技术和传统粉末冶金技术相结合而形成的一项新型粉末冶金成彤技术。首先将粒径在2—15μm的微细金属粉末与定比例粘合剂均匀混合成为具有良好流动性和润滑性的颗粒状喂料，然后采用特制的注射机调整注射压力及速度后，     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

ANGULAR DISTORTION ALLOWABLE VALUE AND ASSESS METHOD OF WELD ON COKE TOWER

A graph as the new engineering method for estimate the safety of bulging deformation of coke tower is proposed. Through stresses analysis of circumferential weld of coke tower and comparing the stresses produced by pressure with heat stress of steady state, residual stress, bending stress produced by both itself weight and wind loads, it showed that the stresses produced by pressure on the angle distortion are the main factor of equivalent stress of the combined stress. After comparing four kinds of stress controlling conditions, the relation to stress with depth of angular distortion, grade of curvature of angular distortion and half of region of angular distortion has been inferred. Graph of deformation allowable value of coke tower for different condition by angular distortion and half of region of angular distortion has been plotted. The five steps for its engineering use have been explained. The lighter the grade of curvature is, the larger of bulge allowance, may be, and the bigger of depth of angular distortion may pose too. For the coke tower with a popular structure of Dg 5 400 mm×28 mm, the result by graph is nearly more than the result of two formulas formed by other research, the error is less than 7.0%. But, the graph can be easily applied to different size of angular distortion.