利用计算机对飞剪电控部分进行改造

重点介绍我厂铝带旋转式飞剪机控制系统由原数控装置改为计算机自动定尺控制系统的改造过程,包括旋转式飞剪简介,计算机自动定尺控制系统的组成,数学模型的建立和程序设计,现场应用效果。     

基于DSP的自动跟踪飞锯机控制系统设计

探讨了将先进的DSP技术应用于自动跟踪定尺飞锯机控制系统,设计其硬件电路及软件流程。DSP技术适时性好,控制精度高,采用DSP技术,可以提高锯切定尺精度。     

薄板开卷校平定尺横切控制系统

文章分析了薄板开卷校平定尺横切机组传统送料控制系统存在的问题。研究提出了新的控制系统,实现了双反馈随时切换,即伺服电机编码器反馈与测量编码器反馈,其具有定尺精度高、运行效率高、使用安全可靠、维护简单的特点,深受用户好评。     

非接触式定尺切割系统在连铸机上的应用

介绍了非接触式定尺的原理、控制系统的组成与功能、使用效果和改进措施.     

冷弯轧制线定尺剪切的PLC控制

本文叙述了冷弯轧制线的控制原理及实施方法，着重介绍了轧制线定尺剪切的ＰＬＣ控制系统。     

飞锯机随动系统的运动分析

飞锯机由随动系统和锯切系统组成,其随动系统直接影响到锯切焊管的定尺精度。本文对随动控制系统进行了运动分析,并给出了运动方程,在此运动方程下随动系统既无刚性冲击又无柔性冲击,飞锯机在不增加伺服电机驱动力矩的情况下,快速返回,提高了定尺精度。     

伦茨交流伺服系统在钢板横剪中位置全闭环的应用

在卷材横剪机组中,定尺送料控制系统是非常重要的组成部分。本文以钢板横剪机组为例,针对定尺控制的工艺要求,提出了伦茨（LENZE）伺服控制系统位置型全闭环应用的方案。实践证明,这些方案是可行的,并可靠地应用在大量的卷材横剪机组中。     

气缸拖动飞锯的微机控制系统

本文介绍的微机控制系统定尺精度达到±5 mm,一次投资为“DDS”系统的1/6。     

飞剪机控制方式初探

描述了飞剪机定尺控制系统的组成,着重从飞剪机伺服电机的转速、刀刃的运行轨迹、工作制和运行方式三个方面详细介绍了飞剪机的控制技术.并通过建立飞剪机在同步区运动的数学模型,得到带材送进到同步区内任意位置时,飞剪机曲拐轴的相应转角和角速度.从而对飞剪机高速高精度定尺剪切的基本原理进行了初步探讨.     

钢管排锯机新型定尺机构及其锁紧装置

管排锯机组的定尺锯切是保障钢管成品率的重要因素,目前采用的悬臂翻摆式定尺挡板结构,因其存在刚性差,易变形,且锁紧不可靠等问题。本文设计了一种新型龙门式定尺机构并采用齿条锁紧装置,改善了定尺挡板的受力情况,实现了定尺挡板的可靠锁紧,保证了成排钢管的定尺精度。实践应用证明,新型定尺机构及其锁紧装置使用效果良好。     

Elucidation of the relationship between the electrochemical migration susceptibility of SnPb solders for PCBs and the composition of the resulting dendrites

Electrochemical migration occurs via electrochemical processes. When a water film forms on the electric circuit and then a bias voltage is applied, the metallic ions dissolve from the anode and move to the cathode. At the cathode, the metallic ions react with the electrons and then form dendrites. Thus, a short circuit failure of the electronic components occurs. This study focuses on the relationship between the electrochemical migration (ECM) susceptibility of SnPb solders and the composition of the dendrites on the basis of electrochemical techniques. It was found that the ECM susceptibility of SnPb solder alloys was affected by the chloride and sulfate ions. After the water drop test, the composition of the dendrites was primarily Pb mixed with Sn, regardless the dissolution/composition ratio of the solder alloys. However, only Sn was detected in the dendrites formed in the acidic solution. The dissolution of the metal from the anode influenced the failure time, and the pH of the corrosion environment significantly changed the composition of the dendrites formed on the cathode. The composition of the dendrites was proven to be closely related to the cathodic deposition efficiency of the ions dissolved from the anode.     

Application of the wavelet transform and the enhanced Fourier spectrum in the impact echo test

The objective of this study is to develop a reliable and effective method to analyze the signal of the impact echo test. The impact echo test is a nondestructive testing technique for civil structures. In the test, the surface response of the target structure due to an impact is measured. Then, the Fourier transform is adopted to transform the signal from the time domain to the frequency domain. Owing to the multiple reflections induced by cracks, voids, or other interfaces, peaks will form in the Fourier spectrum. The frequencies of the peaks can then be used to determine the size of the structure or the location of the defect.

Several difficulties are encountered when applying the Fourier transform to impact echo data. Because the impact echo data are non-stationary and contains multiple reflections, ripples and multiple peaks appear in the Fourier spectrum, which may mislead the follow-up diagnosis. Furthermore, the existence of the high-energy surface wave and structural vibrations often complicates the spectrum and makes the data interpretation even more difficult.

To overcome these difficulties, this research adopts the wavelet transform in the analysis of impact echo data. Theoretically, the wavelet transform can avoid ripple and multiple-peak phenomena. Furthermore, the frequency range and time span of surface wave can be observed in the wavelet scalogram. However, the spectral resolution of the wavelet marginal spectrum is inferior to that of the Fourier transform. Therefore, two approaches are proposed in this paper. One is to combine the Fourier spectrum and the wavelet marginal spectrum to determine the precise location of the echo peak. The other is to take the product of the two spectra to establish the enhanced Fourier spectrum. As such, the interference in the Fourier spectrum is suppressed while the peak is enhanced. Numerical and experimental tests were performed to verify the effectiveness and reliability of the proposed approaches.     

Temperature dependence of the ultrasonic transmission through electrical resistance heated imperfect metal–metal interfaces

Because of surface roughness, the area of contact between real surfaces is less than the geometrical area. For this reason the known rules of acoustic reflection and transmission have to be modified for real interfaces. Ultrasonic transmission through imperfect interfaces is commonly described in terms of the contact stiffness model which assumes distributed springs between the surfaces in contact [Proc. R. Soc. Lond. A 202 244; J. Acoust. Soc. Am. 89 (1991) 503ff; J. Acoust. Soc. Am. 68 1516; J. Nondestr. Eval. 4 177; J. Geophys. Res. 94 (1989) 17681ff].Several authors [Trans. ASME 123 8ff; J. Acoust. Soc. Am. 103 657ff; Ultrasonics 38 513] theoretically and experimentally show the pressure and frequency dependence of the ultrasonic transmission through such interfaces. Our paper will document, that the temperature of the interface has significant influence on the ultrasonic transmission as well.In the experimental approach, a CuSn8-rod was clamped between the electrodes of a resistance welding unit. Either longitudinally or transversally polarised ultrasonic pulses were generated by a transmitter built in the upper electrode. The transmitted ultrasonic signal was subsequently detected by the receiver integrated in the lower electrode. After the welding current was turned on, a strong decrease in ultrasonic transmission has been observed due to resistance heating of the interfaces between the welding electrodes and the rod.To explain this extraordinary strong temperature effect, a simple quasistatic analytical thermal–electrical model of the contacting area was used to give a rough estimation of the maximum interfacial temperature and the temperature distribution during the flow of the welding current. In a second step, the temperature dependence of the material data in the acoustic contact stiffness model was used to calculate the changes in ultrasonic transmission caused by the welding current. It is shown, that the observed decrease in ultrasonic transmission with increasing temperature is mainly caused by the temperature dependence of the elastic constants of the metals and is much stronger than expected for ideal interfaces.The calculated ultrasonic transmission is in very good agreement with the experimental data and seems to be interpreted correctly by the acoustic contact stiffness model.     

Porosity reduction in CO2 laser welding of aluminium alloys ‐ Influence of penetration,joint, oxygen gas and oxide films

This study aims to ensure the safety of nuclear power plants. The accidents involving leaks from the welded zones at the pipe penetration part of a reactor vessel or at a coolant pipe are reported at home and abroad. One of the main causes is the welding residual stress. So, it is important to know the welding residual stress for maintaining high safety of the plants, the estimation of plant's life cycle and the plan of maintenance. The welded joints of the nuclear power plants have complex shapes, and the welding residual stresses also have complex distributions three-dimensionally. In this study, the inherent strain method combined with finite element method is used to measure the welding residual stresses accurately.

The mock-up is idealized for the welded joint at the pipe penetration part of the actual reactor vessel. The inherent strain method is applied to measure the residual stresses. In this method, the inherent strains are unknowns. When the residual stresses are distributed complexly in a three-dimensional stress-state, the number of unknowns becomes very large. So, the inherent strains are expressed with some functions to decrease the number largely. The theory, the experiment process and the analysed results are explained. The characteristics of the distributions of residual stresses and their production mechanisms are discussed. The inherent strain method gives the most probable values and the deviations of the residual stresses. The deviations are small enough for the most probable values. It assures the high reliability of the estimated results.     

调制周期对CrAlN/ZrN纳米多层膜韧性的影响

目的研究调制周期对纳米多层膜性能的影响。方法采用磁控溅射方法制备了CrAlN与ZrN的固定厚度比为2.6,不同调制周期(Λ为6,8,10,20 nm)的CrAlN/ZrN纳米多层膜。利用场发射扫描电镜(FESEM)表征薄膜的形貌、结构。用Dektak150型台阶仪测薄膜表面粗糙度。用Agilent Technologies G200纳米压痕仪检测涂层的硬度和弹性模量。用划痕仪测薄膜/基材的结合力,同时,引入抗裂纹扩展系数(CPR)表征纳米多层膜的韧性。结果 CrAlN/ZrN纳米多层膜断面皆为穿晶柱状结构,调制周期为20 nm时,多层膜层与层之间的界面清晰;多层膜表面呈致密的花椰菜状,厚度均约为2μm。调制周期为8 nm时,硬度为20.4 GPa,进一步增大调制周期,硬度下降。调制周期为8 nm的多层膜临界载荷L_(c2)为18 N,CPR值为73.2,L_(c2)与CPR值均高于其他调制周期的多层膜。在临界载荷L_(c2)处,裂纹扩展导致薄膜发生了严重的片状剥落,露出了亮白的热轧钢基底,薄膜失去了保护作用。结论实验表明,在多层膜厚度、调制比不变的条件下,改变调制周期能够改变多层膜的韧性。随着调制周期的增大,韧性呈先上升、后下降的趋势。调制周期为8 nm时,纳米多层膜的硬度最高,韧性最好,综合性能良好。     

嵌入式共固化阻尼复合材料十字型加筋板的自由振动

为大幅度地提高嵌入式共固化复合材料阻尼结构固有频率,优化其刚度,以嵌入式共固化阻尼复合材料薄板为研究对象,利用有限元的方法对比分析了该结构薄板及十字加筋薄板固有振动特性,并得到了筋材薄壁宽度和高度对结构固有频率的影响规律。结果表明：加强筋大大提高了薄板结构的固有频率和刚度,加筋薄板结构的各阶固有频率随着加强筋高度增大而增加,其中一阶固有频率增加幅度最大。增加加强筋宽度可以提高薄板结构的各阶固有频率,随着加强筋宽度的增加,固有频率的增加幅度减小。     

工艺因素对纳米四方多晶氧化锆浆料固化的影响

水基凝胶流延成型工艺是1种薄片式材料制备新技术，主要是利用陶瓷浆料中有机单体聚合反应形成三维空间的网络结构，将陶瓷颗粒填充于网络骨架中形成具有较高强度的结构均匀的陶瓷坯体。主要研究四方多晶氧化锆薄膜制备过程中，有机单体溶液浓度和pH值对纳米四方多晶氧化锆浆料固化反应的影响。结果表明：随浆料中有机单体浓度的增加，浆料聚合反应速率显著提高，为保证合适的固化时间，有机单体浓度可控制存10％～40％(质量分数)范围内；浆料的PH值对聚合反应速率有显著的影响，随PH值的增大，聚合反应速率降低，合适的pH值范围为9～10；在高于35℃温度范围内，聚合反应速率变化显著，适当的成型温度范围为35℃～45℃；引发剂和催化剂用量增加，反应速率大大提高，为获得较好的成型性能，浆料的引发剂用量应控制在0．15％～0.30％(体积分数，下同)的范围内，催化剂用量在0．20％左右为宜。     

连铸管坯质量对钢管内折缺陷的影响

在对连铸管坯晶区进行划分的基础上阐述了连铸管坯穿孔特有的“隔墙”现象,探讨了连铸管坯的低倍组织及主要化学成分等对钢管热轧的常见缺陷——内折的影响和连铸管坯的各区域及柱状晶的大小与内折之间的关系,同时通过回归分析法得出碳当量与内折率的关系式。     

材料去除过程中Rehbinder效应的研究进展

精密机械加工过程中,利用Rehbinder效应对工件表面特性的影响,可以更好地控制零件表面质量。不同工程材料的Rehbinder效应的微观表现形式有所差异,但宏观结果都是降低工件表面硬度,使材料去除过程更容易进行。回顾了Rehbinder效应概念的提出和发展过程并对其内涵和应用范围进行了阐述,为加工过程中的材料去除方法提供思路,对材料表面完整性的形成具有指导意义。列举了近年来科研人员对Rehbinder效应的相关研究成果,分析对比其在硬脆材料和塑性材料加工过程中的表现形式和微观作用机理,总结Rehbinder效应的影响因素,如极性分子的吸附活性、工件材料的晶粒尺寸等。揭示了Rehbinder效应中极性分子的吸附作用,以及吸附作用后的扩散、位错和间隙三种促进机制,并综述离散元法、有限元法和分子动力学等数值仿真方法对宏观尺度和微观尺度Rehbinder效应机理的研究。Rehbinder效应可以看作是一种对加工表面的改性机制,研究Rehbinder效应作用下的表面活性剂与被加工表面的匹配机制是提高材料表面完整性的关键,对推动精密制造工艺的发展有重要意义。     

超声振动磨削无线电能传输系统特性分析

为研究超声振动磨削无线电能传输系统特性,对原边匹配电容、原/副边之间的不同距离、轴向力大小、线圈匝数、导线直径等进行了研究。实验表明原边并联电容值越大,电路中电流越大;电路中电流随着原/副边距离的增加,电流呈先下降,后基本不变,再下降的趋势;轴向力越大,电路中电流越大;线圈匝数越大,电流越小;同等条件下,线圈导线直径越小,电路中电流越大。研究结果为实际生产应用提供了参考。