FE simulation and process analysis on forming of aluminum alloy multi-layer cylinder parts with flow control forming

The aluminum alloy parts used in airbag of car were studied with flow control forming(FCF) method, which was a good way to low forming force and better mechanical properties. The key technology of FCF was the design of control chamber to divide metal flow. So, the design method of FCF was analyzed and two type of control chamber were put forward. According to divisional principle, calculation model of forming force and approximate formula were given. Then forming process of aluminum alloy multi-layer cylinder parts was simulated. The effect of friction factor, die radius and punch velocity on metal flow and forming force was obtained. Finally, the experiment was preformed under the direction of theory and finite element(FE) simulation results. And the qualified parts were manufactured. The simulation data and experimental results show that the forming sequence of inner wall and outer wall, and then the force step, can be controlled by adjusting the process parameters. And the FCF technology proposed has very important application value in precision forging.

NEW NORMAL FORMS FOR NONLINEAR SYSTEMS (Ⅱ)——CONTROLLABLE FORM

This paper proposes a sort of new normal forms consisting of observer form and controllable form for nonlinear systems. The conditions for transforming to these normal forms are given, respectively. These normal forms are used to treat the problems of observer design and linearization. The first part of this paper deals with the observer form, and the second the controllable form.

CONTROLLED HOT FORMING OF RETAINING RING OF GENERATOR

The relevant results of thermodynamics simulation test, recrystallization study and FEM numercal simulation are described. A method is also introduced that the controlled hot forming is carried out by adopting the program of expansion-extrusion compound forming.

Release Characteristics of Different N Forms in an Uncoated Slow/Controlled Release Compound Fertilizer

This study examined the release characteristics of different N forms in an uncoated slow/controlled-release compound fertilizer （UCRF） and the N uptake and N-use efficiency by rice plants. Water dissolution, soil leaching, and pot experiments were employed. The dynamics of N release from the UCRF could be quantitatively described by three equations： the first-order kinetics equation [N1=N0 （1-e^-kt）], Elovich equation （N1=a ＋ blnt）, and parabola equation （N1=a ＋ bt^0.5）, with the best fitting by the first-order kinetics equation for different N （r= 0.9569^＊＊-0.9999^＊＊）. The release potentials （No values estimated by the first-order kinetics equation） of different N in the UCRF decreased in the order of total N 〉 DON 〉 urea-N 〉 NH4^＋-N 〉 NO3^-N in water, and total N 〉 NH4^＋-N 〉 DON 〉 urea-N 〉 NO3^--N in soil, respectively, being in accordance with cumulative amounts of N release. The constants of N release rate （k values and b values） for different N forms were in decreasing order of total N 〉 DON 〉 NH4^＋-N 〉 NO3^--N in water, whereas the k values were urea- N 〉DON 〉 NH4^＋-N 〉 total N 〉 NO3^--N, and the b values were total N 〉 NH4^＋-N 〉 DON 〉 NO3^--N 〉 urea-N in soil. Compared with a common compound fertilizer, the N-use efficiency, N-agronomy efficiency, and N-physiological efficiency of the UCRF were increased by 11.4%, 8.32 kg kg^-1, and 5.17 kg kg^-1, respectively. The ratios of different N to total N in the UCRF showed significant correlation with N uptake by rice plants. The findings showed that the first-order kinetics equation [Nt=N0 （l-e^kt）] could be used to describe the release characteristics of different N forms in the fertilizer. The UCRF containing different N forms was more effective in facilitating N uptake by rice compared with the common compound fertilizer containing single urea-N form.

电弧熔丝增材制造控形技术研究现状与展望

金属增材制造是制造强国战略下推动我国高端装备制造业转型升级的重点发展方向。电弧增材制造以其高沉积效率、低成本、可进行复杂结构直接成形等优势受到了广泛的关注。但增材过程中涉及的物理过程复杂,成形质量与精度面临很大挑战。针对电弧增材制造技术短流程、长周期的制造特征,讨论如何从热源上降低成形偏差、从过程上降低制造误差、从结果上改善成形精度,介绍了一系列创新的热源调制、过程控制与结果优化的方法策略,总结了现有技术存在的问题与面临的挑战,为如何进一步提升电弧增材过程的成形控制效果提出了几点思考。

Humanoid Based Intelligence Control Strategy of Plastic Cement Die Press Work-Piece Forming Process for Polymer Plastics

The plastic cement belongs to a sort of polymer material, the chemical composition is very complex, and the plastic cement work-piece is generally manufactured by die press forming. Aimed at being difficult to control in parameters of forming process, the paper explored the humanoid based intelligence control strategy. In the paper, it made the anatomy in control puzzle resulted in uncertainty such as chemical component of plastic cement etc., summarized up the characteristic of cybernetics in forming process, researched on the humanoid based intelligence control strategy, and constructed the control algorithm of forming process in plastic cement work-piece. Taking the process experiment of temperature and pressure control as an example, it validated the good dynamic and static control quality through simulation of control algorithm constructed in this paper. The experimental results show that the control algorithm explored in this paper is reasonably available.

Noether-Form Invariance of Nonholonomic Controllable Mechanical Systems in Phase Space

In this paper,we study the Noether-form invariance of nonholonomic mechanical controllable systems inphase space.Equations of motion of the controllable mechanical systems in phase space are presented.The definitionand the criterion for this system are presented.A new conserved quantity and the Noether conserved quantity deducedfrom the Noether-form invariance are obtained.An example is given to illustrate the application of the results.

Teaching Form Reform of "Prevention and Control of Poultry and Poultry Diseases" Course in Higher Vocational Colleges

[ Objective] To meet the needs of ＂Prevention and Control of Poultry and Poultry Diseases＂ course in higher vocational colleges in new period. [Method] In order to introduce theoretical knowledge, enhance practical ability and train quality, teaching content, teaching methods and practical teaching of the course were explored according to trends of academic development and personnel training. [ Result] The reform of teaching form improved the teaching effect, mobilized the learning enthusiasm and initiative of students, and enhanced their ability to solve practical prob- lems. [ Conclusion] The teaching form of ＂Prevention and Control of Poultry and Poultry Diseases＂ course has been successfully reformed.

基于产教融合的材料专业课程体系改革研究

高等教育肩负创新型人才培养重要使命,对支撑科技发展和行业转型升级起到输送人才的关键作用。吉林大学材料成型及控制专业课程体系以产教融合育人为改革目标,针对产业与教学脱节、培养模式固化单一、育人软硬件支撑条件不足等问题,从教学实践课程体系顶层设计优化、科学素养与工程能力双驱动发展和多元育人平台建设等方面,结合吉林省汽车制造与轨道交通支柱产业集群优势,进行具有产教融合特色的课程体系改革研究,探索创新型人才培养新范式,实现“教学支撑科技,科技反哺教学”双驱动的多元协同育人新生态。

产教融合背景下应用型高校材控专业建设探索

文章以成都工业学院材料成型及控制工程专业为例,分析了目前材料成型及控制工程专业发展过程中出现的问题,并围绕模具产业学院建设、专业人才培养模式改革、专业人才培养方案开发、师资队伍建设、实验实训基地、教学情境建设等问题开展调研,探讨了专业建设的目标方向,为培养应用型、高素质材料成型及控制工程专业人才的路径和方式进行了有益探索。

粉细砂岩油藏硅烷基改性控砂剂性能评价与应用

微粒运移是影响粉细砂岩油藏开发效果的主要原因,常规抑砂剂难以达到有效控制微粒运移的要求。为进一步提高药剂稳定储层微粒的性能,文章在计算机分子模拟基础上,设计引入硅烷基改性的新型控砂剂,对合成的控砂剂进行了结构表征和性能测试。新型控砂剂体系含有酰胺基、硅烷基等功能性官能团,与储层微粒通过氢键、共价键作用相互吸附,形成稳定均匀的分子膜,原位固定地层粉细砂或黏土颗粒。性能评价表明:新型控砂剂体系耐冲刷排量达8 500 mL/h,远高于常用抑砂剂900 mL/h的指标,对不同粒径微粒均具有良好的控砂作用,储层原位控砂作用显著。截至目前,现场应用60井次,措施有效率95%,延长稳产期1年以上,取得了显著效果。该技术在全国疏松砂岩油藏具有推广示范意义。

构网型柔性直流系统阻尼环节控制策略优化研究

采用构网控制的柔性直流输电系统可模拟同步电机运行特性,为电网提供频率和电压支撑,而传统的功率同步型构网控制阻尼环节引入了调频功能,使柔直功率输出随电网频率变化而波动。该文基于同步发电机调频和阻尼环节的机理辨析,提出了功率同步型构网控制阻尼环节改进方法,可同时满足并网运行稳态功率精准控制和频率突变的阻尼需求,并基于小信号稳定分析给出了控制参数设计原则,基于电磁暂态仿真平台以及渝鄂柔性直流工程现场试验验证了改进策略的有效性。

定形态隧道压力波激扰下车内压力迭代学习控制

同一列车重复通过同一隧道时所产生隧道压力波激扰具有形态相似、变尺度变幅值的特性.针对现有控制策略未考虑这一定形态特性的问题,提出一种基于高阶反馈遗忘迭代学习的控制方法.首先,建立高速列车车内外气压传递数学模型,并利用实测车内外压力数据进行修正与验证;其次,通过控制列车通风设备的阀门来减缓车内压力变化,提出阶反馈遗忘迭代学习控制算法,并设计变幅值和变尺度处理方法;最后,利用实测压力波生成一组定形态的随机压力波,并进行仿真分析.仿真结果表明:在重复定形态的隧道压力波激扰下,高阶反馈遗忘迭代学习控制算法能够使车内压力在第8个迭代周期后1 s变化率基本收敛到200 Pa/s以下,而且均方根误差也在第4个迭代周期后降低到15.0000%以下.

大面积有机–无机杂化钙钛矿薄膜及其光伏应用研究进展

有机–无机杂化钙钛矿太阳能电池具有制备成本低、光电转换效率(Photoelectric Conversion Efficiency,PCE)高的巨大优势,显示出广阔的商业化前景。经过十几年的深入研究,钙钛矿太阳能电池(Perovskite Solar Cells,PSCs)的实验室器件(<1 cm^(2))、大面积器件(1~10 cm^(2))、迷你模组级器件(10~800 cm^(2))和模组级器件(>800 cm^(2))的最高认证PCE已分别提升至26.10%、24.35%、22.40%和18.60%。随着PSCs面积扩大,PCE急剧下降,这主要是因为制备方法的局限性,难以获得高质量的大面积钙钛矿薄膜。实验室器件常采用的旋涂法难以应用到实际生产中,目前大面积钙钛矿薄膜的制备方法主要有刮涂法和狭缝涂布法,但其存在薄膜成核结晶过程难以精确控制等问题。本文从大面积有机–无机杂化钙钛矿薄膜的制备方法入手,介绍了大面积钙钛矿层成膜机制及薄膜质量提升策略。最后,对未来高PCE、高稳定性的大面积PSCs的制备技术和应用进行了展望,旨在对高性能的大面积PSCs研究提供有益参考。

基于相对等效短路比的新能源——柔直送出系统振荡风险评估

新能源基地并网系统面临与电压支撑强度密切相关的振荡稳定性问题,在海量运行方式下,逐一建立精细化模型的稳定性分析过程耗时较长。短路比指标可直观反映新能源并网系统的电压支撑强度和稳定裕度,但现有短路比无法适用于无同步机电源的系统。为此,将短路比概念合理扩展至全电力电子化系统,基于戴维南等效网络来度量新能源-柔直送出系统电压支撑强度,进而提出了能快速评估新能源-柔直送出系统振荡风险的相对等效短路比计算方法,并阐明相对等效短路比能够全面考虑新能源场站发电功率、交流网架结构以及新能源设备变流控制系统等多重因素对振荡稳定性的影响,最后通过算例验证了相对等效短路比评估方法的有效性。

基于扰动观测的构网型柔直系统阻尼控制器设计

构网型柔直逆变器具有惯性支撑能力,可对低惯性电网进行频率支撑,但也具有类似同步发电机的振荡特性,系统受扰后构网型逆变站易参与电网振荡,导致振荡范围扩大。首先构建了构网型逆变站和受端电网的简化状态空间模型,基于奇异值分解技术研究了控制器参数、柔直并网位置以及电网惯量分布对交直流系统振荡特性的影响,确定了两区域系统中柔直的最佳并网位置。接着利用构网型逆变站对电网扰动的主动响应能力,设计了基于扩展状态观测技术的振荡阻尼控制器(disturbance observer-based damping controller,DODC),利用构网型逆变站自身的量测对交直流混联系统的关键状态进行实时估计,并利用二次型最优反馈控制实现关键振荡模态阻尼抑制。最后通过DIgSILENT/PowerFactory-MATLAB联合仿真模型对所提控制策略的有效性进行了验证。

集无功和谐波补偿功能于一体的构网型变流器研发

为了解决大规模风电并网面临的电压越限、谐波谐振、主动支撑能力变差等问题,充分利用电力电子变换装置灵活可控的优势,研发了一种集静止无功发生器(SVG)和有源滤波器(APF)功能于一体的构网型变流器。类比直流母线电容的充放电特性和同步发电机转子的加减速特性,设计有功控制环,在不引入锁相环的情况下实现电网相位跟随、谐振风险降低;基于无功-电压下垂控制原理,设计无功控制环,实现无功补偿和电压支撑;通过谐波电流检测和内环电流控制,实现负载谐波电流补偿。最后,搭建基于RT-Box的硬件在环实验平台,对所提构网型变流器的多重功能进行验证。结果表明,并联设计的集静止无功发生器和有源滤波器功能于一体的构网型变流器可大大改善电网谐波、功率因数,提高电力系统的电能质量。

构网型控制改善跟网型变流器次/超同步振荡稳定性的机理和特性分析

构网型(grid-forming,GFM)并网变流器具有良好的弱电网稳定性,同时能够改善跟网型变流器的次/超同步振荡稳定性。为明确GFM控制改善振荡稳定性的机理和特性,首先推导了GFM变流器电路特性与每个控制环节的关系,并分别从变流器自身电路特性、变流器并网系统整体阻抗特性角度揭示了GFM控制改善振荡稳定性的电路机理。然后,基于阻抗模型定量分析了GFM变流器占比提升对系统振荡频率、阻尼的影响。最后,利用电磁暂态仿真进行了验证。结果表明:GFM变流器在无功控制环节、电压外环作用下表现为“正电阻”,能够削弱跟网型变流器控制环节引入的负阻尼特性,进而改善系统次/超同步振荡稳定性;此外,GFM变流器占比提升能够显著改善系统振荡阻尼,但对振荡频率影响较小。

全功率直驱风机电网友好型控制策略

基于构网型控制的电网友好型风电机组具有黑启动、电网支撑和弱电网运行等优势,近年来逐渐被广泛研究。为探究不同电网友好型控制在不同场景下的运行性能,以全功率直驱风机为研究对象,总结归纳了4种典型的电网友好型风电机组控制策略。基于不同控制策略的架构和特点,在PSCAD/EMTDC仿真平台上搭建了相应电网友好型风电机组模型。分别在黑启动、风速变化、功率减载、频率支撑、电压支撑、故障恢复以及故障限流7种工况下探究不同控制策略的运行性能。最后,综合不同工况下的仿真结果,得到了总体性能最优的控制策略。

一种体现构网型控制特征的柔性直流机电暂态改进建模方法

总结柔性直流采用构网型控制呈现的新特性并提出相应的机电暂态建模方法。通过分析,提出构网型控制替代跟网型控制给柔性直流带来的主要变化是:电压源支撑,故障穿越切换措施以及电流限幅方法。相对应的,构网控制型柔性直流机电暂态模型是对跟网控制型柔性直流模型的改进,包括将换流器与交流网络的接口由传统的一个交流仿真步长内的平均功率改为平均电压;增加故障穿越措施切换逻辑以及增加基于用户自定义的电流限幅措施。通过交直流间接口方法仿真对比,以及机电、电磁暂态模型故障模拟验证所提模型的有效性。该模型能高精度模拟构网控制型柔性直流在交流电网中的动态行为,具有良好的应用价值。