2219铝合金电子束堆焊凝固缺陷的模拟预测

铝合金电子束堆焊焊缝根部缩孔是一种特种焊接缺陷,它会导致应力集中诱发裂纹产生,显著降低焊件承载能力,必须给予足够重视.文中主要借助于ANSYS有限元软件的APDL二次开发编程语言,将匙孔模式焊接热源模型与枝晶间渗流理论和Niyama判据相结合,提出了一套基于温度场的凝固收缩判据程序,并应用它成功模拟预测了非熔透2219铝合金电子束堆焊件的根部缩孔缺陷.结果表明,通过模拟手段得到的缩孔缺陷沿焊缝熔深方向误差为8.76%,沿焊缝熔宽方向误差为13.28%,与试验对比件基本吻合,验证了缺陷判据程序的正确性和实用性.     

基于CAE技术的自行车座同模异穴型腔熔料流动平衡设计

利用CAE技术对2种尺寸的自行车座在同一副注射模中成型时熔料的流动平衡状态进行分析,提出对原浇口结构进行改进的方案,并对改进的方案进行模拟分析。根据分析的结果,对原浇注系统尺寸进行改进。结果表明:CAE技术在熔料填充模具型腔的流动平衡设计过程中,具有快速、准确、高效等优势,可以缩短模具制造周期,降低制造成本,提高生产效率。     

基于加工中心的大尺寸深腔之精加工方法

对于尺寸较大的配合型腔的精加工,可先加工出四周内壁之间的圆弧过渡部分,再分别对内壁和底面进行粗加工和精加工,最后加工底面圆角。具体分析了每一环节可能出现的问题,并提出切实可行的加工办法和操作技巧。     

插装阀先导控制级的集成设计

对具有换向动作要求的插装阀先导控制级集成设计进行了研究。以单容腔执行元件和双容腔执行元件为基础研究了先导控制级的集成设计过程,并通过在注塑机液压系统中的应用完整演示了集成设计的应用方法。结果表明:经过插装阀先导控制级的集成可以节省液压系统成本,降低系统控制的复杂程度,该方法可以进一步推广到具有比例方向、流量和压力控制功能的其他系统中,可为液压系统智能设计工具的开发提供参考。     

低速旋转盘腔内液体流动特性

利用粒子图像测速测试平台研究了低速旋转盘腔轴向中截面的液体流动特性,并利用Realizable k-e模型对低速旋转盘腔内液体流场进行三维数值模拟,模拟结果与实验值吻合较好,最大相对误差为16.9%. 利用模型方程研究了导流板数、导流板相对长度、进口雷诺数和旋转雷诺数对盘腔内液体流动的影响. 结果表明,盘腔体积平均相对速度及涡量受进口雷诺数(Re)、导流板数、导流板相对长度影响较大,当进口Re从17000升至53000时,体积平均相对速度及涡量分别增加2.4倍和1.6倍;当导流板数由0提高至4时,体积平均相对速度及涡量增幅分别为62%和30%;当导流板相对长度由0.5提高至0.93时,体积平均相对速度及涡量增幅分别为114%和58%. 盘腔压损主要受进口Re的影响,当进口Re从17000升至53000时,盘腔压损增长8倍,而导流板数及导流板相对长度对压损的影响较小,增幅均小于5%. 为强化旋转盘腔内流体与壁面间传热,减小流体阻力,应优化进口Re、尽量增加导流板数和长度.     

Electric charging/discharging characteristics of super capacitor,using de-alloying and anodic oxidized Ti-Ni-Si amorphous alloy ribbons

Charging/discharging behaviors of de-alloyed and anodic oxidized Ti-Ni-Si amorphous alloy ribbons were measured as a function of current between 10 pA and 100 mA, using galvanostatic charge/discharging method. In sharp contrast to conventional electric double layer capacitor (EDLC), discharging behaviors for voltage under constant currents of 1, 10 and 100 mA after 1.8 ks charging at 100 mA show parabolic decrease, demonstrating direct electric storage without solvents. The supercapacitors, devices that store electric charge on their amorphous TiO_2-x surfaces that contain many 70-nm sized cavities, show the Ragone plot which locates at lower energy density region near the 2nd cells, and RC constant of 800 s (at 1 mHz), which is 157,000 times larger than that (5 ms) in EDLC.     

Flash microwave pressing of zirconia

Microwave Pressing is a promising way to reduce microwave sintering temperatures and stabilize microwave powder materials processing. A multiphysics simulation was conducted of the regulated pressure-assisted microwave cavity. This simulation took into consideration resonance phenomena and the nonlinear temperature-dependent material parameters of zirconia. The intrinsic behaviors of microwave systems and zirconia make the regulation of the microwave pressing difficult. However, the same phenomena can be used to activate flash sintering. Flash microwave sintering uses high electric fields of the resonant microwave profile, the Negative Temperature Behavior (NTC) of zirconia resistivity, and the mechanical pressure applied to the powder via a die compaction configuration. The resulting flash microwave pressing still needs improvement in terms of the processed material structure homogeneity, but it has the capacity to become the fastest sintering treatment as it allows room temperature activation where the total process time only takes a few seconds. In addition, this 10-20 seconds processing technique has shown good potential for improving the transparency of alumina presintered specimens.     

Effect of Cavity Disinfectants on Adhesion to Primary Teeth—A Systematic Review

Some authors have been proposing the use of cavity disinfectants in order to reduce, or even eliminate, the effect of the microorganisms present in a dental cavity before a restoration is placed. The aim of this study was to evaluate the effect of different cavity disinfectants on bond strength and clinical success of composite and glass ionomer restorations on primary teeth. The research was conducted using Cochrane Library, PubMed/MEDLINE, SCOPUS, and Web of Science for articles published up to February 2021. The search was performed according to the PICO strategy. The evaluation of the methodological quality of each in vitro study was assessed using the CONSORT checklist for reporting in vitro studies on dental materials. Sixteen in vitro studies and one in situ study fulfilled the inclusion criteria and were analyzed. Chlorhexidine was the most studied cavity disinfectant, and its use does not compromise dentin bonding. Sodium hypochlorite is a promising alternative, but more research on its use is required to clearly state that it can safely be used as a cavity disinfectant for primary teeth. Although other disinfectants were studied, there is a low-level evidence attesting their effects on adhesion, therefore their use should be avoided.     

电极塞及塞座模具的设计

阐述了电极塞与塞座两种热固性小塑件模具设计的经过及设计中应注意的问题，并成功地解决了这两种塑件的模具设计难题，为其国产化提供了必不可少的工艺装备。     

高反射激光泵浦腔材料的研制

本研究制备了氧化铝陶瓷泵浦腔，并在其表面施上了掺杂具有激活和敏化作用的稀土元素的釉，以提高腔体釉面的反射率。试验中对只掺杂激活离子和掺杂了敏化离子及激活离子的样品的反射性进行了对比研究，发现掺杂稀土元素的釉能有效地提高氧化铝陶瓷的白度及反射率。