A New Magnetic Sensor Concept for Nondestructive Evaluation of Deteriorated Prestressing Strand

This article describes proof-of-concept testing of a sensor based on magnetic field detection to estimate the remaining effective cross-sectional area in corroded prestressing strands inside prestressed concrete beams. The primary corrosion mode is rusting of the strand. The magnetic properties of rust are vastly different from those of steel, thus making a magnetic sensor theoretically feasible. An electromagnet system with Hall sensors has been designed. The electromagnet induces a magnetic field in the specimen by magnetizing it from one side, and at a particular distance from the electromagnet's pole face. At near magnetic saturation, for various diameters and distances of up to 2 in from the magnet face, the induced magnetic field is reliably related to the effective cross-section of the steel bar. Experiments with steel rods and prestressing strands of different diameters conducted in a laboratory are presented. Initial results confirm that by using an appropriate electromagnet based on the magnetic-field technique, in-situ detection of remaining effective cross-sectional area is possible. Challenges in making this technique practical are discussed. If the follow-up research confirms the practicality of the proposed magnetic sensor, there is a potential to substantially improve the state-of-the-art in bridge inspection in terms of accuracy and convenience.     

腐蚀极化曲线的微机测试系统

从腐蚀极化曲线测试的特点及要求出发,用微机和普通恒电位仪组成其测试系统,由计算机通过Ｄ／Ａ转换产生所需的波形电压,代替波形发生器工作,然后用两路Ａ／Ｄ分别采集腐蚀电流和腐蚀电位,并同步显示腐蚀极化曲线,本研究在提高腐蚀极化曲线测试水平方面进行了成功的尝试。     

钢芯铝绞线中的电偶腐蚀行为

钢芯铝绞线中不同金属接触容易产生电偶腐蚀.通过测量Fe和Al分别与纯Zn、镀Zn、5%Al-Zn合金、2%Mg-Zn合金、55%Al-Zn合金在1 mol/L NaCl溶液中的电偶电流,判断不同金属接触时的腐蚀程度,从而选择钢芯镀层,达到最佳匹配,减轻电偶腐蚀.结果表明:Fe与55%Al-Zn合金镀层的电偶电流最小,腐蚀程度最轻;含Mg的热镀Zn层与Al形成的电偶比纯热镀Zn层与Al形成的电偶的腐蚀程度轻.     

内齿珩轮的计算机辅助几何造型

内啮合珩齿工艺是一种高效低耗的齿轮精加工工艺,所用刀具是内齿珩轮,珩轮齿面形状为渐开线螺旋面的包络面.由于该包络面形状复杂,使珩轮基体齿面形状的设计和制作成为一个难题.针对这一难题,该文提出用计算机辅助几何造型方法设计珩轮齿面.首先,根据机床要求和被加工齿轮情况确定内齿珩轮的齿数、外径、高度以及珩轮与被加工齿轮的轴距和轴交角;其次,构建内齿珩轮和被加工齿轮的运动模型,并用拉伸构型法构造齿轮的实体模型,用圆柱构造珩轮毛坯的实体模型;然后,利用几何造型技术中的集合操作,对珩轮毛坯作循环差操作,直至形成准确的珩轮模型.最后,通过沿珩轮齿宽取断面的操作,得到珩轮齿面各部位的断面形状,并标注尺寸.     

钢芯铝绞线的铝线在NaCl溶液中的腐蚀行为

钢芯铝绞线正常运行温度达80℃,受到环境中盐离子的严重腐蚀。采用Tafel直线外推法、电化学阻抗谱法及加速腐蚀试验法,研究了钢芯铝绞线的铝线在不同浓度NaCl溶液中的腐蚀行为,利用SEM和XRD等表征了其腐蚀表面状态及产物形貌。结果表明:随着NaCl浓度的升高,铝线的自腐蚀电位负移,极化电阻变小,腐蚀速率增大,当NaCl为70 mg/L时腐蚀速率急剧增加,是10 mg/L NaCl时的40倍;腐蚀产物及钢芯表面镀锌层可抑制铝线的腐蚀,铝线腐蚀后的表面出现大量的"麻点"及腐蚀坑,白色的腐蚀产物主要由Zn0.64Al0.36(OH)2(CO3)0.18.0.86H2O组成。     

计算机辅助互楞纸箱设计

介绍研制的软件CADCB,采用人机交互式对话操作方式,能迅速地依据用户要求选择出最佳纸箱结构造型,精确地计算出该纸箱结构尺寸,并能进行纸箱强度分析和排料方案设计等等。另外.数据图形的输入输出多样化,且配有可扩充的瓦楞纸箱数学模型库和图形库。     

计算机画法几何解题系统的初步探索

以 AutoCAD 2000i为图形支撑平台,构建一种计算机辅助画法几何方法以直观、精确、高效地求解三维空间几何度量与定位问题。提出一种微直径的线实体和微厚度的面实体处理方法,用以实现高精度的线面求交、面面求交。文章中介绍的计算机画法几何解题系统适合于传统画法几何求解,也可用于曲柄滑块机构的行程、运动轨迹等内容的设计。     

计算机辅助选材系统EI

介绍了计算机辅助选材系统，提出了综合选材中的归化和加权方法，给出了综合选材的最优化方程，以达到利用材料数据库和知识库选择最符合要求的材料。     

Computer Aided Design of Experiments

A computer oriented method which assists in the construction of response surface type experimental plans is described. It takes into account constraints met in practice that standard procedures do not consider explicitly. The method is a sequential one and each step covers the experimental region uniformly. Applications to well-known situations are given to demonstrate the reasonableness of the procedure. Application to a ‘messy” design situation is given to demonstrate its novelty.     

Computer Aided Model for Casting Aluminium Using Die-Casting

Computer aided casting of aluminum using die-casting was developed. A piston, which is an automobile part and very important in internal combination engine, was chosen for the research. Pistons are made of aluminum alloy. Models of the products were developed to aid the casting process. Mathematical models that show the dimensions of the casting were also developed. Since the project is about using computer to aid casting process, a program using visual basic （VB） Language was developed. The program was used to incorporate die-casting process into computer system. The written program was tested and the model of the casting product （piston） was displayed. The result shows that computer which is faster with accurate result can be used as an aid in the production of aluminum piston using die-casting process, for accurate planning in the manufacture of the product.     

Computer Aided Composition Design of Prehardened-Mould Steel for Plastic

The improvement of machining behavior of prehardened-mould steel for plastic is realized by using computer-aided composition design in this work. The results showed that the matrix composition of large sectional prehardened mould steel for plastic markedly influences the precipitation of non-metallic inclusion and the control of composition aided by Thermo-Calc software package minimizes the amount of detrimental oxide inclusion. In addition the modification of calcium is optimized in the light of composition design.     

轴承径向游隙计算机辅助测试系统

应用计算机技术，在现有测微仪的基础上，对轴承径向游隙的检测过程进行改进，可消除测量时的人为误差，并提供更多的测量信息，同时提高了计量和测试管理的自动化水平。     

单层及双层手性吸波涂料的计算机辅助设计

本文给出了计算涂料型手性吸波材料反射性能的公式，结合实例分别讨论了手性参数的实部和虚部对手性吸波材料性能的影响。数值分析结果表明，选择适当的手性参数，手性吸波材料和普通材料相比性能可有所提高。通过改变手性在数的虚部能改变单层涂料的工作频带；对双层手性吸波材料来讲，手性参数的实部不但影响材料的吸波性能，也影响材料的工作频率，虚部对材料的性能几乎没什么影响。     

换热器计算机辅助设计

把换热器的设计和计算机辅助设计的概念相结合，提出了换热器设计的一个系统模型，考虑到换热器结构形式的多样性及影响换热性能因素的复杂性，较好地解决了人机互补问题及与绘图软件ＡＵＴＯＣＡＤ的相结合问题，对空冷式换热器进行了具体实现。整个系统分成两部分；辅助设计计算部分和辅助设计制图部分。具有良好的适应性和人机友好性。     

计算机辅助构造PRS工具的实现

通过对企业活动之间基本联系方式的分析以及过程规则集基本类型研究，借助功能－功能矩阵ＦＦＭ（Ｆｕｎｃｔｉｏｎ－ＦｕｎｃｔｉｏｎＭａｒｔｒｉｘ）及其操作算法，建立了计算机辅助构造过程规则集（ＰｒｏｃｅｄｕｒａｌＲｕｌｅＳｅｔ，ＰＲＳ）工具－ＣＡＢＰＲＳ，并在其基础上将ＰＲＳ自动转化成０－０表达和行为关系图（ＢｅｈａｖｉｏｒＲｅｌａｔｉｏｎｓｈｉｐＧｒａｐｈ，ＢＲＧ）以验证ＰＲＳ的一致性和完整性，以及实     

铝稀土涂层在海洋防腐中的腐蚀行为

通过电化学交流阻抗谱(EIS)技术研究了铝稀土涂层在铜加速醋酸盐雾试验中的腐蚀行为,建立了等效电路模型并分析了相关电化学参数随时间的演变规律.结合扫描电镜、能谱分析了涂层腐蚀后的形貌及成分,阐释了电化学参数的演变规律.结果表明,盐雾试验第一阶段,铝稀土涂层由2个容抗弧组成,高频段对应致密层阻抗,低频段对应铝稀土涂层电化学反应阻抗;盐雾试验第二阶段,多孔层开始影响铝稀土涂层的电化学行为.     

履带钢计算机辅助孔型设计系统的开发

针对履带钢断面是非对称轴的复杂断面型钢特点,探讨了履带钢计算机辅助孔型设计系统。该系统可直接调用AutoCAD实现参数化绘制孔型图,通过计算机数值模拟,辅助于物理模拟,实时修改孔型图,提高孔型设计精度,减少试轧次数,同时实现了良好的图形交互界面,为实际生产的履带钢孔型设计提供了良好的辅助工具。