含缺陷钢结构焊接接头检测与评估

由于焊接热过程的作用,焊接接头较容易产生组织性能劣化、残余应力、应力集中以及各种焊接缺陷。焊接缺陷的存在严重影响了焊接结构件的质量和安全使用,因此对含缺陷焊接接头进行安全性评估具有重要的工程应用价值。基于综合考虑含缺陷焊接接头的缺陷检测手段和BS 7910缺陷规则化表征处理的方法,对BS 7910中失效评估图的级别以及相应级别下针对含缺陷焊接接头评估点坐标确定过程中所涉及的应力种类和修正因子进行探讨,为工程实际利用BS 7910对焊接接头进行评估时的缺陷检测手段选择、缺陷规则化表征处理以及失效评估图级别的选择、评估点坐标的确定提供参考。     

R60702钨极氩弧焊焊接工艺评定

R60702焊接过程中容易出现气孔和氧化等缺陷，缺陷的产生与原材料和焊接工艺有直接关系。因此，通过对材料的焊接性进行分析，选择合适的焊接材料和焊接工艺，注重焊前处理、焊中保护和焊后处理，使焊接接头满足使用要求。     

低合金高强度钢压力容器焊接的质量控制

介绍低合金高强度钢压力容器焊接过程和焊后常出现的缺陷，分析其产生的因素，并从焊接前准备、焊接过程、焊接后检验三个方面对低合金高强度钢压力容器焊接接头的质量进行控制。     

关于钢轨移动式气压焊焊接塌角问题的探讨

针对采用YHGQ-1200型气压焊轨车在现场焊接过程中钢轨接头出现塌角缺陷的问题,以博小线换轨施工焊接再用轨为例,根据型检过程中与现场实际出现的问题,对钢轨接头塌角缺陷的产生原因进行了分析,归纳总结出钢轨接头塌角缺陷的解决方案。现场实测表明,该方案可以有效地解决钢轨焊接接头塌角的问题,对钢轨焊接具有一定的参考意义。     

基于"生死单元"技术的焊缝缺陷模拟

应用有限元方法，计算分析带几何缺陷焊接接头力学性能。通过杀死焊接接头有限元模型中相应位置的单元，模拟存在的几何缺陷。计算分析带有气孔或咬边缺陷的焊接接头应力分布特性和应力集中程度，验证了应用生死单元模拟几何缺陷的有效性。通过对建模方法的比较，表明生死单元技术能够灵活模拟缺陷。     

氨制冷压力管道焊接接头质量检测及分析

氨制冷系统中压力管道是特种设备安全监管的核心,管道的焊接接头质量将直接影响整个氨制冷系统的运行安全。对氨制冷压力管道焊接接头进行缺陷及显微组织检测,分析焊接缺陷产生的原因以及对氨制冷管道服役安全造成的危害,并提出提高氨制冷管道焊接质量的建议。     

低温使用状态的奥氏体不锈钢焊接

论文针对了奥氏体不锈钢的焊接特点及易出现的焊接缺陷,主要介绍了对应用在低温环境下的奥氏体不锈钢焊接时,在不增加焊接接头中铁素体体积含量的前提下,如何采取措施防止焊接接头产生热裂纹,从而保证其接头的低温韧性。     

压力容器常用几种有色金属焊接产生气孔的分析和对策

1引言随着工业的发展，一些具有特殊性能的有色金属广泛地应用于制造压力容器。但是，这些有色金属在焊接过程中容易产生一些缺陷，特别是气孔，而气孔的存在会大大降低焊接接头疲劳强度，甚至无损探伤检查不出的小气孔对疲劳强度都会产生明显的不利作用。实验表明，气孔能使接头疲劳强度降低一半甚至四分之三。有鉴于此，必须分析这些有色金属焊接易产生气孔的原因，从而采取相应的措施加以防范。2造成工业纯钛焊接气孔的主要原因气孔是工业纯钛焊接时最常见的焊接缺陷，往往在熔合线附近形成。而这些气孔的形成主要是氢引起的。因为氢在钛…     

氢气瓶定期检验与缺陷分析

本文对氢气瓶进行定期检验,通过对焊接接头进行磁粉检测,发现表面裂纹,对裂纹成因分析,裂纹产生是由焊接缺陷和焊接内应力共同作用,在制造过程中可以采取相应措施避免焊接缺陷产生,同时提出了定期检验重点检验部位。     

塔筒T型接头焊接裂纹成因及控制

“T”型焊缝接头是风电塔筒较为薄弱之处,而焊接裂纹则是“T”型接头最危险的工艺缺陷。该文通过对风电塔筒“T”型接头焊接裂纹形成的原因进行分析,发现采用增大焊缝成形系数、选择合理的焊接参数等工艺方法,可有效预防焊接裂纹的产生。     

Single-molecule avidin-biotin association reaction studied by force-clamp spectroscopy

Using single-molecule force-clamp spectroscopy, where the distance between the AFM tip and the sample surface is fixed and a few parallel avidin-biotin complexes are kept stretched by a certain force, we were able to observe the formation of single avidin-biotin bonds. Perspectives to use such an approach to study association reactions at single-molecule level in the conditions resembling those characteristic for some processes in vivo (e.g. virus-cell membrane attachment) are briefly discussed.     

Near-field visualization of dynamical processes of semiconductor surface

The near-field images calculation method for semiconductor surface with inhomogeneous electron distribution, formed by strong focused laser pulse, was proposed. Calculation is performed using Green function method. The main characteristic of the proposed approach is maximal usage analytical computations. The near-field images for the surface of GaAs were obtained at different points of time. Developed approach is universal and could be able to find with experimental data on time-resolved near-field microscopy some parameters of semiconductor surface such as diffusion constant and relaxation time.     

General three-dimensional image simulation and surface reconstruction in scanning probe microscopy using a dexel representation

The ability to image complex general three-dimensional (3D) structures, including reentrant surfaces and undercut features using scanning probe microscopy, is becoming increasing important in many small length-scale applications. This paper presents a dexel data representation and its algorithm implementation for scanning probe microscope (SPM) image simulation (morphological dilation) and surface reconstruction (erosion) on such general 3D structures. Validation using simulations, some of which are modeled upon actual atomic force microscope data, demonstrates that the dexel representation can efficiently simulate SPM imaging and reconstruct the sample surface from measured images, including those with reentrant surfaces and undercut features.     

数字现场工艺纪律管理系统

介绍了利用ASP.NET技术开发一套基于B/S模式的数字现场工艺纪律管理系统的方法,实现了对现场工艺纪律的数字化和动态化管理。同时对系统的体系结构、功能特点和技术难点进行了介绍。     

Blind estimation of general tip shape in AFM imaging

The use of flared tip and bi-directional servo control in some recent atomic force microscopes (AFM) has made it possible for these advanced AFMs to image structures of general shapes with undercut surfaces. AFM images are distorted representations of sample surfaces due to the dilation produced by the finite size of the tip. It is necessary to obtain the tip shape in order to correct such tip distortion. This paper presents a noise-tolerant approach that can for the first time estimate a general 3-dimensional (3D) tip shape from its scanned image in such AFMs. It extends an existing blind tip estimation method. With the samples, images, and tips described by dexels, a representation that can describe general 3D shapes, the new approach can estimate general tip shapes, including reentrant features such as undercut lines.     

A.C.Cleland公式在氨制冷循环最佳中间温度求解中的应用

以A．C．C1eland公式为基础，实现了氨双级压缩制冷循环最佳中问温度的计算机求解，并给出了多种工况下的最佳中间温度的结果。     

双分散型两相润滑剂的润滑性能及机理的研究

本文研究了二氧化硅和石墨或MCA粒子双分散型两相(液—固)润滑剂的摩擦磨损特性,这种双分散型的两相润滑剂的抗磨性能均较基础油为优。其中二氧化硅和石墨双分散型的几种油样的抗磨性能极其近似,说明抗磨性能与粒子含量无关。其摩擦系数随载荷的提高而显著下降,但达到一定的临界载荷值后,又趋于平稳,根据这些实验现象,笔者着重研究了双分散型润滑剂不同种粒子的协同作用方式,建立了相应的物理模型,并以此模型来分析实验现象产生的机理。     

Novel carbon nanosheets as support for ultrahigh-resolution structural analysis of nanoparticles

The resolution in transmission electron microscopy (TEM) has reached values as low as 0.08 nm. However, these values are not accessible for very small objects in the size range of a few nanometers or lower, as they have to be placed on some support, which contributes to the overall electron-scattering signal, thereby blurring the contrast. Here, we report on the use of nanosheets made from cross-linked aromatic self-assembled monolayers as TEM sample supports. When transferred onto a copper grid, a single 1.6-nm-thick nanosheet can cover the grid and is free standing within the micron-sized openings. Despite its thinness, the sheet is stable under the impact of the electron beam. Micrographs taken from nanoclusters onto these nanosheets show highly increased contrast in comparison to the images taken from amorphous carbon supports. In scanning transmission electron microscopy with nanosheet support, a size analysis of sub-nanometer Au clusters was performed and single Au atoms were resolved.     

High-resolution wave field reconstruction using a through-focus series of images taken under limited electron dose

The three-dimensional Fourier filtering method and Schiske's Wiener filtering method are compared with the aim of high-resolution wave field reconstruction of an unstained deoxyribonucleic acid (DNA) molecular fiber using a through-focus series of images taken under a limited electron dose. There were some definite differences between the two reconstructed images, although the two kinds of processing are essentially equivalent except for the dimension and the filter used for processing. Through theoretical analyses together with computer simulations, the differences were proved to be primarily due to specimen drift during the experiment. Although the observed structure of the DNA molecular fiber was heavily damaged by electron beam irradiation, reconstructed images by the three-dimensional Fourier filtering method provided higher resolution information on the molecular structure even when relatively large specimen drift was included in the through-focus series. In contrast, in Schiske's Wiener filtering method, the detailed information of the structure was lost because of the drift, although the reconstructed image showed a higher signal-to-noise ratio. The three dimensional Fourier filtering method seems to be more applicable for observing radiation-sensitive materials under an extremely low electron dose, because specimen drift cannot be completely avoided.     

A phenomenological model of fluctuation electron microscopy for a nanocrystal/amorphous composite

Fluctuation electron microscopy (FEM) is a quantitative electron microscopy technique in which we use the variance V of spatial fluctuations in nanodiffraction as a function of the diffraction vector magnitude k and real-space resolution R to detect medium-range order in amorphous materials. We have developed a model for V(k, R) from a nanocrystal/amorphous composite, which is an idealized form of the medium-range order in various amorphous materials found by previous FEM measurements. The resulting expression for V(k, R) as a function of the nanocrystal size, nanocrystal volume fraction, and the sample thickness connects the FEM signal to well-defined aspects of the material's structure, emphasizes the need for samples of controlled thickness, and explains in some cases the relative height of peaks in V(k). We give an example of interpreting FEM data in terms of this model using recent experiments on amorphous Al88Y7Fe5.