空调制冷用Φ5mm瘦齿大螺旋角内螺纹铜管旋压成形和管内换热性能

通过旋压成形模具优化设计、工艺试验、齿形参数观测和单管换热性能测试,研究Φ5 mm瘦齿大螺旋角内螺纹铜管旋压成形工艺和换热性能。结果表明,5球旋压工艺下,Φ5 mm×0.23 mm×0.12 mm,54条齿,12°齿顶角,27°螺旋角内螺纹铜管旋压成形的最佳旋模比为800~900。降低旋压成形过程中变形率利于获得较大螺旋角的内螺纹铜管。管内换热性能较同规格普通内螺纹铜管有明显提升,特别是冷凝换热系数平均提高17%,而压力损失仅略有增加。     

Key Technologies for Preparing Nanoparticles of Hydrogen Storage Material by Combining Ball Milling with Aerosol Generation

The developing trend of vehicle is electrical vehicle in future,and fuel cell will become the one of the main batteries of electrical vehicle because of its the prominent properties.The one of current obstacle for fuel cell in popularization and applications is lacking of excellent performance hydrogen storage materials and advanced technologies of preparing nanoparticles for hydrogen storage materials.The principles,typical classifications and characteristics of chemically and physically preparing nanoparticles for hydrogen storage materials are briefly introduced.And it predicts that physical method is going to be the major developing direction for nanoparticles for hydrogen storage material fabrication.The principle,the system composition &characteristics of method by means of combining ball milling with aerosol generation preparing nanoparticles for hydrogen storage materials are expounded.The ball milling process for hydrogen storage material is needed to conduct effective cooling process,and the lower cooling temperature has better milling results.The cooling media for ball milling include room temperature water,ice water,pure ethanol with dry ice and liquid nitrogen.The proper level of vacuum in canister is significant for injecting aerosol particles during the ball milling.In order to maximize the friction force,it is better to design multi-level stirring rod and the profile of stirring rod with large contact area,therefor stirring rod with cylinder has less grinding effect than with ring profile.The more stirring rod with more layers will obtain higher stirring efficiency.The distance between each layer of branches is 2.5times larger than diameter of the ball.The simulation results show that the average speed has 120% increases from 400 rpm to 800 rpm.Based on the kinetic energy equation,it is obtained that there is 350% increase in energy from 400 r / min to 800 r / min.The higher stirring speed will generate the finer material.And the discussion of this article provides a favorable basis of preparing nanoparticles for hydrogen storage materials in fuel cell vehicle.     

热机械合金化法制备纳米晶W-Cu复合粉末

采用热机械合金化制备纳米晶W-Cu复合粉末。通过XRD、SEM、激光粒度测试等方法对球磨后的粉末进行表征。结果表明:随球磨时间延长,W的晶粒尺寸不断减小,球磨30 h后W的平均晶粒尺寸为41 nm左右;球磨初期,粉末迅速细化;随球磨时间延长,粉末粒度有所增加;进一步增加球磨时间,粉末粒度减小。球磨粉末还原后有较高的烧结活性,1 200℃烧结后相对密度可达97%以上。烧结材料的组织非常均匀,且晶粒细小。     

An investigation on electrochemical hydrogen storage performances of Mg-Y-Ni alloys prepared by mechanical milling

The nanocrystalline and amorphous Mg2Ni-type electrode alloys with a composition of Mg20?xYxNi10 (x=0, 1, 2, 3 and 4) were fabricated by mechanical milling. Effects of Y content on the structures and e...     

基于小波包分析的铣刀状态监测方法研究

应用小波分析方法,通过对声发射信号的处理及分析判别铣刀状态.以三齿牛鼻铣刀为实验对象,分别以铣刀3种状态为例,采用不同的切削参数进行铣削实验,将采集到的AE信号进行小波分解后再进行时频域对比,结果表明:该方法可以比较准确的判断铣刀状态,并且有较好的理论基础、直观性与易操作性.     

UG／CAM在汽车模具加工中的应用

介绍了UG／CAM数控编程的基本过程,以第三横梁成形模中的凹模镶件为例,重点分析了不同加工方法对加工质量的影响。     

彩色显像管模具锥型芯内腔小孔数控铣床加工与修理

在彩色显像管玻壳模具加工中,锥型芯内腔小孔加工和修理不可避免,而且加工的精度直接影响到产品的成型。多年来美国、日本等国均采用成型刀加工,而且维修时采用切割掉小头部分,然后组装焊接,再加工的方式,这样既浪费材料,又增加加工成本,且新焊接的材料与已经高温使用过的本体材料有差别,造成产品成型质量的不稳定。本文就介绍在数控铣床上加工锥型芯内腔小孔和修理的加工方法。     

金属抗磨自修复材料对球轴承寿命的影响

采用2组相同型号的滚动轴承疲劳寿命强化试验机,设置相同的外部环境及试验条件,在其中1组试验机的润滑油箱中按比例加入金属抗磨自修复材料,进行对比试验研究。结果表明,添加金属抗磨自修复材料的强化试验机的润滑油理化指标无明显变化,轴承振动值稳定,且轴承疲劳寿命明显延长。     

氧化锆陶瓷微细铣削工艺参数实验研究

微小型化技术已经形成了全球化的发展趋势,并对多种应用领域产生了深刻的影响,尤其在武器装备和现代生物医学等领域.同时,氧化锆陶瓷材料由于其高硬度、绝缘的性能,被普遍应用于微型飞行器、微型发动机、微型机载设备、微传感器、微型机器人、微型卫星等领域.陶瓷材料由于其硬度高,难以采用常规硬质合金刀具进行铣削加工,且由于其不导电的...