Necking Point in PET High-speed Fiber Spinning

Cross-over method is established to predict necking point for PET high- speed fiber spinning. Even slowly crystallizing polymers such as PET can crystallize on the spinline at sufficiently high spinning speed. The development of rtmning velocity, temperature, crystallinity and theological force is investigated for the take-up velocity over a range of 6 000 - 10 000 m/min. The position of necking point, temperature rise and abrupt increase of crystallinity move closer to the spinneret with the increase of take-up velocity,

STRUCTURE EVOLUTION OF POLYMER CHAINS FOR NECKING FORMATION IN HIGH-SPEED FIBER SPINNING PROCESS

Finite element method is used to simulate the high-speed melt spinning process, based on the equation system proposed by Doufas et al. Calculation predicts a neck-like deformation, as well as the related profiles of velocity, diameter, temperature, chain orientation, and crystallinity in the fiber spinning process. Considering combined effects on the process such as flow-induced crystallization, viscoelasticity, filament cooling, air drag, inertia, surface tension and gravity, the simulated material flow behaviors are consistent with those observed for semi-crystalline polymers under various spinning conditions, The structure change of polymer coils in the necking region described by the evolution of conformation tensor is also investigated. Based on the relaxation mechanism of macromolecules in flow field different types of morphology change of polymer chains before and in the neck are proposed, giving a complete prospect of structure evolution and crystallization of semi-crystalline polymer in the high speed fiber spinning process.

Modeling of workpiece temperature suppression in high-speed dry milling of UD-CF/PEEK considering heat partition and jet heat transfer

High-performance carbon fiber-reinforced polyether-ether-ketone(CF/PEEK)has been gradually applied in aerospace and automobile applications because of its high strength-to-weight ratio and impact resistance.The drymachining requirement tends to cause the cutting temperature to surpass the glass transition temperature(Tg),leading to poor surface quality,which is the bottleneck for dry milling of CF/PEEK.Temperature suppression has become an important breakthrough in the feasibility of high-speed dry(HSD)milling of CF/PEEK.However,heat partitioning and jet heat transfer mechanisms pose strong challenges for temperature suppression analytical modeling.To address this gap,an innovative temperature suppression analytical model based on heat partitioning and jet heat transfer mechanisms is first developed for suppressing workpiece temperature via the first-time implementation of an air jet cooling process in the HSD milling of UD-CF/PEEK.Then,verification experiments of the HSD milling of UD-CF/PEEK with four fiber orientations are performed for dry and air jet cooling conditions.The chip morphologies are characterized to reveal the formation mechanism and heat-carrying capacity of the chip.The milling force model can obtain the force coefficients and the total cutting heat.The workpiece temperature increase model is validated to elucidate the machined surface temperature evolution and heat partition characteristics.On this basis,an analytical model is verified to predict the workpiece temperature of air jet cooling HSD milled with UD-CF/PEEK with a prediction accuracy greater than 90%.Compared with those under dry conditions,the machined surface temperatures for the four fiber orientations decreased by 30%–50%and were suppressed within the Tg range under air jet cooling conditions,resulting in better surface quality.This work describes a feasible process for the HSD milling of CF/PEEK.

Serrated chip characteristics and formation mechanism in high-speed machining of selective laser melted Ti6Al4V alloys

Serrated chips,consisting of extremely uneven plastic deformation,are a prominent feature of high-speed machining of difficultto-machine materials.This paper focuses on the evolution of chip form,chip morphology features(chip free surface,tool-chip contact surface,and chip edge),and chip segment parameters in subsequent high-speed(vc=50 and 150 m min-1)machining of selective laser melted(SLMed)Ti6Al4V alloys,which are significantly different from conventional Ti6Al4V alloy in microstructure,mechanical properties and machinability.The effect of laser beam scanning schemes(0°,67.5°,and 90°),machined surfaces(top and front),and cutting speeds on serrated chip characteristics of SLMed Ti6Al4Valloys was investigated.Based on the Johnson-Cook constitutive model of SLMed Ti6Al4Valloys,an orthogonal cutting model was developed to better understand the effect of physical-mechanical properties on the shear localization,which dominates the formation mechanism of serrated chips in post-machining of SLMed Ti6Al4V alloy.The results showed that the critical cutting speed(CCS)for chip serration of SLMed Ti6Al4V alloy is lower than that for serrated chips of conventional Ti6Al4V alloy,and the serrated profile of SLMed Ti6Al4V chips was more regular and pronounced.Besides,due to anisotropic microstructure and mechanical properties of SLMed Ti6Al4Valloys,the serration degree of chips produced on the top surfaces of SLMed Ti6Al4Valloys is more prominent than that of chips generated on the front surfaces.In addition,because of the poor deformation coordination and high plastic flow stresses of needle-like martensiteα′,the plastic flow and grain distortion in the adiabatic shear band(ASB)of SLMed Ti6Al4V chips are significantly smaller than those in the ASB of conventional Ti6Al4V with equiaxed grains.

聚酯长丝的再生生产工艺分析

在聚酯长丝的再生生产中,合理的工艺对其资源利用率的提升、石油消耗的降低以及环保效果的提升都十分有利。基于此,文章对聚酯长丝的再生生产工艺进行分析,包括再生切片干燥生产工艺、再生切片熔融挤出工艺、聚酯长丝纺丝成形工艺以及聚酯长丝拉伸卷绕工艺等,以期为聚酯长丝的再生生产提供科学参考。

毛细管微流控芯片器件研究进展

毛细管微流控芯片是微流控芯片领域中重要的一部分,因其具有制备难度低、材料成本低、化学性能优良以及设计灵活的独特优势而得到了广泛的应用与研究。文中对毛细管微流控芯片的基本工作原理与制作方法进行了详细叙述,重点综述了近年来毛细管微流控芯片在液滴生成、纤维纺丝等领域中的研究进展与应用,最后对目前面临的问题进行了探讨,并展望了该技术未来在标准化、高通量及灵活性等方面应用的发展方向。

Chip morphology and cutting temperature of ADC12 aluminum alloy during high-speed milling

The ADC12 aluminum alloy is prone to severe tool wear and high cutting heat during high-speed milling because of its high hardness.This study analyzes the highspeed milling process from the perspective of different chip morphologies.The influence of cutting temperature on chip morphology was expounded.A two-dimensional orthogonal cutting model was established for finite element analysis(FEA)of high-speed milling of ADC12 aluminum alloy.A theoretical analysis model of cutting force and cutting temperature was proposed based on metal cutting theory.The variations in chip shape,cutting force,and cutting temperature with cutting speed increasing were analyzed via FEA.The results show that,with the increase in cutting speed,the chip morphology changes from continuous to serrated,and then back to continuous.The serrated chip is weakened and the cutting temperature is lowered when the speed is lower than 600 m·min^(-1)or higher than 1800 m·min^(-1).This study provides a reference for reducing cutting temperature,controlling chip morphology and improving cutting tool life.

基于单片机的断纱监测控制系统设计

为了提升细纱工序生产效率和产品质量,设计一种基于单片机的细纱机单锭断纱在线监测控制系统,介绍该系统的设计方案,详述压电传感器、信号处理电路、单片机控制电路和夹持器的系统硬件以及处理盒软件、控制箱软件的设计要点.指出:断纱监测控制系统以AT89S52单片机为控制核心,采用485总线通信技术,通过处理盒单元和控制箱单元,可实现细纱工序纱锭状态信息的实时在线采集与处理显示,且环境适应性强、成本低廉、性能稳定可靠;将多个处理盒在总线上并联,可适配任意锭数细纱机,实现对所有纱锭信息的处理、分析汇总和显示,降低挡车工劳动强度和企业用工量,提高了细纱生产流程的智能化水平.

可生物降解聚乳酸长丝的熔融纺丝工艺

为了纺制高品质的聚乳酸长丝,采用熔融纺丝方法,优化切片干燥工艺,研究了纺丝工艺参数(纺丝温度、纺丝速度、拉伸倍数、拉伸温度)对聚乳酸长丝性能(黏均分子质量、取向、力学性能等)的影响,最终确定了最佳的纺丝工艺。最优的切片干燥工艺为:分2阶段进行干燥,第1阶段由室温逐步升温至60～65℃,停留3～4 h预结晶,第2阶段逐步升温至100℃干燥15 h,最终切片含水率低于0.005%。最佳纺丝工艺为:纺丝温度195℃,纺丝速度1 000 m/min,拉伸3倍,拉伸温度T1/T2/T3=72℃/80℃/82℃。

MEMS原子自旋陀螺气室芯片加工设备与工艺研究

原子自旋陀螺是基于原子自旋极化效应的一类陀螺仪,在实现高精度检测的同时,又具有小型化和批量化制造的潜力。本文针对原子自旋陀螺对气室芯片的高浓度补偿气氛要求,结合集成制造的技术趋势,设计制造了能承受20×101.325kPa气压的气室芯片专用键合装置。完成了集成RF线圈的6amagat Amagat为浓度单位,定义为1个大气压0℃情况下单位体积内理想气体的分子数浓度原子自旋陀螺用气室芯片的工艺流程设计并进行了工艺流片。流片结果获得了完整的气室芯片结构,漏率的检测结果为3.0×10-8 Pa·m3/s,验证了装置和工艺的可行性。

聚酯切片中的粉末研究

采用ＤＳＣ，ＧＰＣ等方法研究了聚酯切片中的粉末与切片的区别，发现湿粉末与切片的粘度、相对分子质量及其分布基本相同，但粉末有一定程度的结晶，而湿切片是无定形的。二者的主要差别在于粉末的熔体结晶速率快，结晶峰尖窄，过冷程度低。粉末经过预结晶、干燥之后并未形成高熔点物，但其粘度高于干切片，可能发生了部分固相缩聚，易造成纺丝熔体不均匀。粉末的存在对高速纺丝有不良影响，应该去除。

电子自旋共振仪中嵌入单片机测控系统的设计

嵌入式单片机系统与传统的实验仪器相结合,是实现测量自动化和提高实验精度的有效方法。在经典近代物理实验仪器———电子自旋共振仪中嵌入8051单片机系统,用计算机代替人眼对信号的观测,克服了传统示波显示方法的弱点,实现了共振峰的客观判定,显著地提高了判断的准确度。同时,由于共振谱线等信号被量化,可以被方便地存储、调用,还可通过串行通信口送往PC机做进一步的处理。与传统实验仪器相比,测量数据的分散性得到了明显的改善,g因子的相对误差由大于0.5%减小为0.1%左右。

微流体芯片在纤维成型方面的应用研究进展

微流体芯片可在微通道中控制、操作和检测复杂流体,具有尺寸小、效率高、集成度高、响应时间短、样品需量少等优点。除了在生物化学、有机合成、疾病检测等领域有广泛的应用之外,微流体芯片在纤维成型方面也有很大的应用潜力。在简介了微流体技术的基础上,比较了传统纺丝技术和微流体纺丝技术,综述了微流体芯片在即时纺丝、静电纺丝和蛋白质成纤方面的研究进展,展望了微流体纺丝技术在高性能纤维、纳米纤维、生物/化学纳米传感器、组织工程等方面的应用前景。

芯片原子自旋陀螺在空空导弹中的应用展望

原子陀螺具有高精度和高灵敏度等优点,近年来已经成为国内外惯性技术的研究热点。简要介绍了原子陀螺的发展现状,根据空空导弹惯性制导系统的特点,重点对芯片原子自旋陀螺在空空导弹中的应用前景进行了展望。

一种混合滤波算法在电子自旋共振仪中的应用

在电子自旋共振仪中,由于所采集的信号受脉冲和连续变化的扫场电流的干扰,造成测量数据失真,从而导致显示不稳定。通过硬件和软件滤波的方法可以消除干扰。本文研究了一种基于软件的混合滤波算法,该算法是一种极值和均值相结合的混合滤波算法。实验表明,这种混合滤波方法比通常的中值滤波、均值滤波具有更好的抗干扰能力,能够提高数据的准确度。采用混合滤波算法后,电流测量值的误差不大于±0.4mA,达到了设计要求。

细纱机新型成型机构控制方法的研究

提出变频调速系统控制细纱机偏心凸轮成型机构的算法.介绍了单片机同步控制传动装置的原理及其软硬件实现,并通过实验进行了分析.运行结果表明:该控制系统调节方便,运行可靠,能够满足实际应用的需要.

生物组织脱水机智能控制系统设计

介绍了以AT89C2051单片机作为控制核心的生物组织脱水机智能控制系统的设计思想及实现方法,并对系统的硬件接口和主要控制软件进行了具体分析。解决了传统生物组织脱水机抗干扰能力差、易死机等问题;采用了滚动式中文菜单,能对机器在运行中出现的故障给出完整、明确的提示。从而实现了高质量的机电一体化设计。

FinFET纳电子学与量子芯片的新进展

综述了后摩尔时代中两大发展热点:鳍式场效应晶体管(FinFET)纳电子学和基于量子计算新算法的量子芯片的发展历程和近两年的最新进展。在FinFET纳电子学领域,综述并分析了当今Si基互补金属氧化物半导体(CMOS)集成电路的发展现状,包括FinFET的发展、10 nm和7 nm技术节点的量产、5 nm和3 nm技术节点的环栅场效应晶体管(GAAFET)和2 nm技术节点的负电容场效应晶体管(FET)的前瞻性技术研究以及非Si器件(InGaAs FinFET、WS2和MoS2两种2D材料的FET)的探索性研究。指出继续摩尔定律的发展将以Si基FinFET和GAAFET的技术发展为主。在量子芯片领域,综述并分析了超导、电子自旋、光子、金刚石中的氮空位中心和离子阱等五种量子比特芯片的发展历程,提高相干时间、固态化及多量子比特扩展等的技术突破,以及近几年在量子信息应用的新进展。基于Si基的纳米制造技术和新的量子计算算法的结合正加速量子计算向工程化的进展。

硅基自旋量子比特技术研究进展

量子芯片是运用量子力学基本原理构建实用化计算机的基础。各国研究团队通过近几年的卓越研究工作,将硅基量子比特芯片技术发展成量子计算的核心方向之一。文章重点归纳了Si自旋量子比特的主要类型,分析了可靠量子计算实现所要求的高保真度、长程耦合等指标的关键技术。这些技术的研究表明,硅是一个能实现全面量子计算发展的可行平台。

基于自旋阀结构的磁传感器的研究

自旋阀结构的发现为磁电子学以及磁传感器的研究揭开了新的一页。基于自旋阀结构的磁传感器由于具有灵敏度高、功耗小、高集成度等优点,因此在传感器工业中具有广泛的应用前景。本文介绍了基于自旋阀结构的磁传感器的研究方法。首先介绍了自旋阀结构及其特性,然后介绍了基于自旋阀结构的磁性薄膜的制备方法和结构优化,其次介绍了基于自旋阀薄膜的磁传感器芯片的制造工艺,最后介绍了基于惠斯通电桥结构的自旋阀磁传感器芯片。