一种精确测量ASTM标准圆形拉伸试样锥度的方法

介绍了ASTM标准中圆形拉伸试样主要部位的尺寸与要求。采用国产万能工具显微镜-投影法对试样在平行长度部位的锥度进行了测量。该方法简便易行,结果准确可靠,满足了标准要求,同时发挥了老设备的作用,保证了试样的加工精度。     

消防水炮喷嘴流场数值模拟研究

消防水炮是消灭大型火灾的关键工具,正在向大流量、远射程和高射高等方向发展。喷嘴作为消防水炮的核心部件之一,其设计直接决定射流性能的优劣。采用Fluent对3种不同内轮廓线结构的消防水炮喷嘴进行流场数值模拟,分析结构形式对射流压力、速度和湍动能的影响,从而确定消防水炮喷嘴的最佳内轮廓线结构。通过实验结果可知,在流量为40、50、60和80 L/s的情况下,采用正弦形式的喷嘴内轮廓曲线的射程高于国标规定射程15%以上。以上研究可为提高消防水炮射流性能提供参考。     

Numerical Investigation on Residual Stresses of the Safe-End/Nozzle Dissimilar Metal Welded Joint in CAP1400 Nuclear Power Plants

The residual stress evolution in a safe-end/nozzle dissimilar metal welded joint of CAP1400 nuclear power plants was investigated in the manufacturing process by finite element simulation. A finite element model, including cladding, buttering, post-weld heat treatment (PWHT) and dissimilar metal multi-pass welding, is developed based on SYSWELD software to investigate the evolution of residual stress in the aforementioned manufacturing process. The results reveal a large tensile axial residual stress, which exists at the weld zone on the inner surface, leads to a high sensitivity to stress corrosion cracking (SCC). PWHT process before dissimilar metal multi-pass welding process has a great influence on the magnitude and distribution of final axial residual stress. The risk of SCC on the inner surface of the pipe will increase if PWHT process is not taken into account. Therefore, such crucial thermal manufacturing process such as cladding, buttering and post-weld heat treatment, besides the multi-pass welding process, should be considered in the numerical model in order to accurately predict the distribution and the magnitude of the residual stress.     

微细盘状电极制备及其微细电解加工研究

基于电化学腐蚀加工方法,提出了一种微细盘状电极的制备方法。先采用平板阴极电化学腐蚀法,将毛坯加工成圆柱状微细电极,再对圆柱电极端部进行绝缘保护,进一步腐蚀制备得到微细盘状电极。利用微细圆柱电极、盘状电极和盘状群电极,在厚1 mm的304不锈钢片上进行电解加工对比实验,结果证明采用微细盘状电极电解加工微小孔,其加工定域性有明显改善,侧壁间隙减小,且降低了孔锥度。     

1000MW机组中速磨煤机风环改造分析

针对电厂长期存在的石子煤排量大、风环堵塞、出力不够等问题,对磨煤机进行改造。通过对磨煤机风环进行优化设计,合理分配喉口数量、优化叶片流线外形、保证合理的通流面积。将喷嘴的下部向外倾斜一定角度,设计成"喇叭"状,实现拆分一次风为两部分的目的,形成一次风通过喷嘴向上吹扫和侧向吹扫的状态。改变风环的材质,采用耐磨性高的高铬白口铸铁,降低风环的磨损量。设置了可调节的挡板装置,用于补偿磨煤机的后期磨损。提高了磨煤机出力,增加了磨煤机碾磨能力,减轻中速磨煤机易磨损部件的磨损,延长其使用寿命。满足锅炉大比例掺烧褐煤的需要,降低了发电成本。     

空间光通信系统发射光束准直特性研究

提出一种前端直接耦合光纤平凸透镜的聚合物直光锥光准直系统.通过具体地对直光锥的端体结构参数进行优化设计以得到高耦合效率准直精度的直接耦合式聚合物直光准直系统.并利用光线传输理论和仿真实验,论证了直光锥的锥角和锥长准直效能的较大影响.结果表明,选择合适的锥角和锥长能达到十微弧度级准直精度,能较好地满足空间光通信系统远距离发射和接收对于光束质量的要求.此外,理论数值和仿真实验同样验证了该直接耦合式直光准直系统对于较大发散角的发散光束具有较好准直效果.     

Non-contact measurements of water jet spreading width with a laser instrument

Jet spreading width is one of the important characteristics of water jets discharging into the air. Many researchers have dealt with measuring this width, and contact measuring methods on the water jet surface were employed in a lot of the cases. In order to avoid undesirable effects caused by the contact on the jet surface, we introduce non-contact measuring methods with a laser instrument to the measurements of jet spreading width. In measurements, a transmitter emits sheet-like laser beam to a receiver. The water jet between the transmitter and the receiver interrupts the laser beam and makes a shadow. The minimum and maximum values of the shadow width are measured. In addition, pictures of the water jet are taken with a scale, and the shadow width is measured from the pictures. The experiments on various needle strokes were performed. Three kinds of width consistent with the jet structure were obtained. In the results, it can be concluded that our non-contact measuring methods are feasible. The data of jet spreading widths and jet taper were obtained and are useful for future applications.     

异形孔零件的线切割编程与加工

通过对典型零件的加工工艺分析，介绍了用北京迪蒙卡特线切割机床加工锥度、上下异形类零件的程序编制规则和方法，该方法相比TurboCAD软件自动编程操作简单快捷，编程者更易掌握。     

AWJM Performance of jute/polyester composite using MOORA and analytical models

This work addresses the machinability performance of jute/polyester composites with variable laminate thickness using Abrasive water jet machining (AWJM) process. A hybrid objective function was developed using surface roughness (R_a) and kerf taper angle (T_a) and studied using a cost-effective Multi Objective Optimization by Ratio Analysis named as MOORA. The influence of machining parameters such as hydraulic pressure (P), feed rate (V_f) and standoff distance (S_d) on quality characteristics were considered for this analysis. Among all, V_f was found to be a strong influencing factor on T_a and R_a. The deviation in the magnitude of T_a and R_a was observed in the case of varying laminate thicknesses without affecting the optimum condition. Besides, a mathematical regression model was developed for both T_a and R_a based on the correlation between the dependent variables. Furthermore, two other models of R_a available in the literature were considered for comparison with experimental results. The results revealed the suitability of these models for the polymer-based fiber-reinforced composite materials, but limited to the maximum thickness of 3?mm. The good agreement of the models with two different sets of experimental values was also found.     

影响锥形喇叭口密封性的有限元分析

为解决制动系统接头加注过程中出现的泄漏问题,将锥形接头的密封原理应用到泄漏原因分析中。首先,运用有限元分析软件ANSYS,建立了两组不同结构尺寸与接头密封性之间的关系,根据分析得到的结果,把每一组的接触状态分布图和位移矢量变形图进行了对比,找出了影响喇叭口接触密封性能的主要原因;然后,进行了生产工艺上的改进;最后,进行了密封性试验。研究结果表明,锥角差是影响密封性能的主要原因,并且改进后的喇叭口密封性能得到了显著提高。