异种状态TC4 钛合金电子束焊接性能分析

针对相对疏松的铸造钛合金和相对密实的锻造钛合金的焊接问题,开展了两种状态的TC4钛合金电子束焊接工艺研究,对比了不同焊接参数对焊接质量的影响。研究结果表明,采用方波扫描可以较好地实现铸造钛合金与锻造钛合金的连接,焊缝成形良好,内部无缺陷;焊接接头力学性能分析表明,拉伸断裂位置全部在铸件母材区一侧。实焊结果证明,电子束焊接可以实现异种状态TC4钛合金焊接的工程化应用。     

A-TIG焊接技术在奥氏体不锈钢焊接中的应用研究

简要介绍了A-TIG焊接的工艺特点和国内外发展概况。研究了A-TIG焊接技术中活化剂对0Cr18Ni9奥氏体不锈钢焊缝熔深的影响。分别考察对比了不锈钢A-TIG焊及普通TIG焊焊接后所得两种焊缝的机械性能、化学成分、金相组织、铁素体含量及焊缝抗晶间腐蚀性能。结果表明：A-TIG焊接具有与TIG焊间等优良的焊缝质量，并可大幅度地增加焊缝的熔透量，提高焊接效率。     

电子回旋共振中和器内静磁场及微波电磁场的数值计算

为了研究电子回旋共振中和器内静磁场和微波电磁场的分布规律,设计合理的磁路结构以形成电子回旋共振区,并使微波强电场区与电子回旋共振区重合,采用有限元分析软件对中和器内的静磁场和微波电磁场进行了数值计算。计算结果表明:永磁体及磁轭的尺寸均影响电子回旋共振区的分布;天线伸入长度越长,微波电场越强。微波频率为4.2GHz时,六块相同的长12mm,宽8mm,高5mm的条形永磁铁与磁轭组成的磁路结构,可以产生合理的电子回旋共振区。L型天线伸入长度为5mm时微波强电场区可与电子回旋共振区重合。     

焊接方式对铝合金搅拌摩擦焊T 型接头性能的影响

采用4种规格的搅拌头进行了2A70-T6铝合金T型接头搅拌摩擦焊试验,并对焊缝横截面进行了观察以及焊缝抗拉强度的测试.结果表明:焊缝中前进侧熔合过渡区的金属变形比返回侧剧烈,焊缝断裂往往发生在前进侧;在相同的焊接参数下,单道焊缝的焊核宽度与抗拉强度随着搅拌针直径的增大而增大,但增大的幅度较小,并列焊的焊缝抗拉强度仅为单道焊缝的93％左右;为了获取相同宽度的焊核,采用加粗搅拌针单道焊比并列焊更具有优势.     

Primary mass discrimination of high energy cosmic rays using PNN and k-NN methods

Probabilistic neural network (PNN) and k-Nearest Neighbors (k-NN) methods are widely used data classification techniques. In this paper, these two methods have been used to classify the Extensive Air Shower (EAS) data sets which were simulated using the CORSIKA code for three primary cosmic rays. The primaries are proton, oxygen and iron nuclei at energies of 100?TeV–10?PeV. This study is performed in the following of the investigations into the primary cosmic ray mass sensitive observables. We propose a new approach for measuring the mass sensitive observables of EAS in order to improve the primary mass separation. In this work, the EAS observables measurement has performed locally instead of total measurements. Also the relationships between the included number of observables in the classification methods and the prediction accuracy have been investigated. We have shown that the local measurements and inclusion of more mass sensitive observables in the classification processes can improve the classifying quality and also we have shown that muons and electrons energy density can be considered as primary mass sensitive observables in primary mass classification. Also it must be noted that this study is performed for Tehran observation level without considering the details of any certain EAS detection array.     

高压球形气瓶焊缝结构设计与焊接工艺

研究了气瓶赤道焊缝区的结构优化设计和焊接工艺改进措施,焊缝区渐变补强设计提高了焊缝区的应变协调性,改进电子束与焊缝作用方式解决了内部飞溅问题,采用优化的电子束工艺参数进行焊接。结果表明:焊接接头质量达到了GJB1718A—2005《电子束焊接》标准Ⅰ级焊缝,焊缝及热影响区力学性能与母材相当,气瓶进行鉴定试验,性能指标满足设计要求。气瓶焊缝结构优化设计,降低了焊缝处应力水平,减少应力集中,通过改进焊接工艺提高了电子束焊缝质量。     

化学模型对数值模拟等离子体流动的影响研究

针对典型再入飞行试验条件,基于求解化学非平衡N-S方程的数值方法,对再入体非平衡等离子体绕流进行数值模拟,比较分析了两种典型化学模型对电子数密度数值模拟结果的影响。研究发现,7组分化学模型的电子数密度模拟结果具有较好的一致性,而11组分化学模型的数值模拟结果则存在较大差异,产生差异的主要机制在于不同模型中氧原子的电离效应,总体上Park模型的数值模拟结果与飞行测量结果具有较好的一致性。     

Imaging Global Electron Content backwards in time more than 160 years ago

The Global Electron Content, GEC, represents the total number of electrons in the spherical layer over the Earth restricted by orbit of Global Positioning Satellite system (20,200 km). GEC is produced from Global Ionospheric Map of Total Electron Content, GIM-TEC, transformed to the electron density varying with height using the International Reference Ionosphere and Plasmasphere model, IRI-Plas. The climatologic GEC model is developed from GIM-TEC maps for a period 1999–2012 including the solar activity, annual and semiannual cycles as the most important factors affecting daily GEC variation. The proxy R_zp of the international sunspot numbers, R_i, is used as a measure of solar activity composed of 3 day smoothed R_i, 7 day and 81 day backwards mean of R_i scaled to the range of 1–40 proxy units, p.u. The root mean square error of the GEC climatologic model is found to vary from 8% to 13% of GEC. Taking advantage of a long history of sunspot numbers, the climatologic GEC model is applied for GEC reconstruction backwards in time for more than 160 years ago since 1850. The extended set of GEC values provides the numerical representation of the ionosphere and plasmasphere electron content coherent with variations of solar activity as a potential proxy index driving the ionosphere models.     

Active space debris charging for contactless electrostatic disposal maneuvers

The remote charging of a passive object using an electron beam enables touchless re-orbiting of large space debris from geosynchronous orbit (GEO) using electrostatic forces. The advantage of this method is that it can operate with a separation distance of multiple craft radii, thus reducing the risk of collision. The charging of the tug–debris system to high potentials is achieved by active charge transfer using a directed electron beam. Optimal potential distributions using isolated- and coupled-sphere models are discussed. A simple charging model takes into account the primary electron beam current, ultra-violet radiation induced photoelectron emission, collection of plasma particles, secondary electron emission and the recapture of emitted particles. The results show that through active charging in a GEO space environment high potentials can be both achieved and maintained with about a 75% transfer efficiency. Further, the maximum electrostatic tractor force is shown to be insensitive to beam current levels. This latter later result is important when considering debris with unknown properties.