起重机钢结构脆性破坏的控制与预防

分析了环境温度、应力大小、类型及板厚等影响因素对钢结构的脆性破坏的影响，介绍了材料的选择及设计和制造环节如何避免脆性破坏，提出了起重机钢结构脆性破坏的控制和预防措施。     

关于钢结构脆性破坏的认识与分析

钢结构作为一种新型建筑结构体系，因其自身特有的优越性，近几年发展迅速，但其在低温环境、内外缺陷和其他条件下容易发生毫无征兆的脆性破坏，后果严重。本文主要介绍钢结构脆性破坏的特征和类型，并从多个方面分析破坏因素，最后针对工程实际存在的隐患，提出预防钢结构脆性破坏的措施。     

优化焊接工艺 防止焊件低温脆性破坏

主要阐述焊接残余应力与低温脆性的关系,提出钢结构输电杆基础在焊接过程中所采取的减小残余应力、预防低温脆性破坏的主要措施,以期为寒冷地带钢结构产品焊接提供借鉴。     

脆性破坏及COD准则

关于钢结构的脆性破坏事故的记载可以追溯到1879年或更早一些。而随着材料强度的提高以及焊接工艺的应用,脆性破坏的事故也在增多。因此对脆性破坏进行了广泛的研究。铁素体钢存在着二种断裂机理,即以沿一定的结晶学平面解理的解理断裂和以显微孔隙的产生和聚集为机理的范性断裂。在温度由高而降低时,就由范性断裂逐步转变到解理断裂。考查脆性破坏事故可以看到具有下述的特点:破坏时的名义应力较低,通常是低于设计应力或材料的屈服强度;破坏前没有或者只有局部的极小的塑性变形;断口是平直而光亮,即一般称为解理断口;破坏一旦发生便以极高的速度扩展     

化工设备低应力脆性破坏的防治

研究化工设备低应力作用下突发性脆性破坏的规律,分析影响脆性破坏的因素,提出了防治措施.     

试论钢结构稳定性

钢结构的稳定性会很直接的影响到工程质量和施工人员的人身安全，本文就钢结构稳定问题和强度问题以及钢结构的设计概念进行浅析，目的是为了避免设计过程中发生不必要的失稳破坏，就要求设计人员在在实际设计中，熟悉了解钢结构的性能后进行设计，从而保证钢结构的稳定性。     

石油化工压力管道的破坏和无损检测

在材质、工艺和环境等因素的影响下,石油化工压力管道极易发生破坏现象,其中以腐蚀、疲劳、蠕变和脆性等破坏形式为主,严重制约了石油化工行业的良性发展。本文结合实践经验,浅析石油化工压力管道的破坏和无损检测。     

浅论桥梁钢结构的完整性设计

随着我国经济的快速发展，国家加快了公路、桥梁等基础设施的建设步伐，钢结构桥梁越来越多得出现在工程建设中。但是近几年国内外发生的多起桥梁钢结构破坏事故引起设计者对焊接结构安全性能的关注，同时也引发了对如何保证桥梁钢结构完整性的思考。本文通过分析钢结构完整性设计的理念以及桥梁钢结构损坏的主要表现，探讨研究了桥梁钢结构完整性设计的方法。     

圆管状钢结构节点的应力集中因子研究现状

管状结构由于优良的结构性能和简洁的外观,被广泛应用于海上设施、桁架、高层建筑、航站楼、火车站、大型体育场、避雷针、道路信号杆等。应力集中会引起脆性材料断裂,使物体产生疲劳裂纹,从而造成构件破坏。在管状钢结构的焊接节点的疲劳设计中,应力集中现象应着重考虑。应力集中因子反映了应力集中的程度,是一个大于1的系数,它的大小取决于节点的几何形状、焊缝尺寸及加载情况。就迄今为止一些学者对管状钢结构应力集中因子所做的研究进行整理,并进行总结与探讨,着重讨论了圆形空心截面管状钢结构应力集中因子的确定及其评估方法,对一些学者推导出的应力集中因子公式的准确性及适用性做了简要对比,并提出了下一步的研究方向。     

化工设备压力容器破坏原因与预防策略探讨

本次研究对化工设备压力容器相关情况浅谈，对化工设备压力容器常见破坏原因加以分析，主要分析压力容器蠕变破坏、压力容器腐蚀破坏，以及压力容器疲劳裂纹破坏、压力容器韧性破坏和压力容器脆性破坏的原因。此后，对化工设备压力容器破坏不良影响研究，经研究发现，化工设备压力容器破坏对设备运行状态、环境均会构成严重影响，而且危险系数非常高需引起重视。最后，对化工设备压力容器破坏预防对策进行刍议，可以联系上述常见的化工设备压力容器破坏问题采用相应的预防措施处理。     

MICROMILLING IN MINIMUM QUANTITY LUBRICATION

This study investigates micromilling of 316 L stainless steel under minimum quantity lubrication. A laser-based technique was developed to measure spindle runout and assist tool setting for fragile micro cutting tools. Thresholds were established to help select cutting parameters and avoid catastrophic tool failure. Computational fluid dynamics was used to simulate flow of lubricant microdroplets around a rotating tool. When properly applied to wet the tool and workpiece, minimum quality lubrication reduces the build up edge on a cutting tool and increases the tool life up to 100 times compared to dry micromilling of 316L and stainless steel.     

Macroscopic electrical field distribution and field-induced surface stresses of needle-shaped field emitters

One major concern since the development of the field ion microscope is the mechanical strength of the specimens. The macroscopic shape of the imaging tip greatly influences field-induced stresses and there is merit in further study of this phenomenon from a classical perspective. Understanding the geometrical, as opposed to localized electronic, factors that affect the stress might improve the quality and success rate of atom probe experiments. This study uses macroscopic electrostatic principles and finite element modelling to investigate field-induced stresses in relation to the shape of the tip. Three two-dimensional idealized models are considered, namely hyperbolic, parabolic and sphere-on-orthogonal-cone; the shapes of which are compared to experimental tips prepared by electro-polishing. Three dimensional morphologies of both a nano-porous and single-crystal aluminium tip are measured using electron tomography to quantitatively test the assumption of cylindrical symmetry for electro-polished tips. The porous tip was prepared and studied to demonstrate a fragile specimen for which such finite element studies could determine potential mechanical failure, prior to any exhaustive atom probe investigation.     

一种改进的敏感数字水印技术

首先介绍了数字水印的基本原理并对图像数字水印技术进行了总结,然后提出了一种改进的基于离散Haar小波变换和量化编码的敏感数字水印技术.针对原技术的缺陷,在改进技术中,离散Haar小波变换没有进行归一化处理;此外,对量化函数和水印嵌入公式进行了修改.理论和实验证明,这些改进使得该敏感数字水印技术可以更容易地实现,消除了原有的缺陷.最后,结合纠错编码技术提出了一种在验证水印时无需原水印信息的方法.     

基于双向渐进结构优化法的柔性机构设计

基于双向渐进结构优化法提出一种面向柔性机构的拓扑优化设计策略。由于采用0/1离散拓扑设计变量和启发式变量更新机制,双向渐进结构优化法一般适用于结构刚度相关的凸优化设计问题。柔性机构以最大化驱动端的位移为设计目标,属于典型的非凸优化问题,难以直接应用该方法开展相应的设计。针对于此,通过定义一种由驱动位移和刚度特性（柔顺度）加权平均的优化目标函数,实现基于双向渐进结构优化法的柔性机构设计。该优化目标函数具有双重功效：（1）通过逐步（设计迭代步）衰减刚度特性的贡献,实现优化问题由刚度设计向驱动设计的动态演化,可应用双向渐进结构优化法开展机构的拓扑构型设计;（2）通过调节加权系数,实现对设计机构的驱动性能和刚度特性的灵活匹配调控,可有效抑制铰链的形成、防止应力集中引起的失效。典型算例的设计结果显示,提出的发展的演化式设计策略可实现稳健且高效的柔性机构设计。     

The preparation of fragile protoplasts for electron microscopy

A method is described whereby highly fragile protoplasts may be successfully prepared for electron microscopy.     

A Simple Sectioning Technique For Use in Conjunction With Scanning Electron Microscope Examination of Polymer-Treated Textile Materials

A technique is described which allows relatively thick but fragile assemblies to be examined without damaging their internal structure.     

Comparison of cleaning methods for delicate insect specimens for scanning electron microscopy

The objective of the present study was to compare cleaning methods for delicate insect specimens for investigations with scanning electron microscopy (SEM). As typical specimens we used aquatic larvae of mosquitoes, springtails, larvae of mayflies and caterpillars because they are very fragile and large parts of their body consist of soft tissue. Additionally their cuticle is very often covered with dirt, soil particles or other materials. Cleaning with ultrasonic sound, as the most common cleaning method used for SEM, will destroy fragile insects. Therefore we tested different procedures to remove the dirt particles. In a first approach we compared cleaning with Potassium hydroxide (KOH), Proteinase K, and Triton X in aquatic larvae of flies, which were available in numbers and kept under the same conditions. As our results showed that the treatment with KOH gives the best results we treated in a second approach springtails, larvae of mayflies and caterpillars only with KOH. The springtails and caterpillars were largely free of particles after treatment with KOH; however, the larvae of mayflies were still covered with remnants of diatoms and precipitates of calcium carbonate of the algae. KOH dissolves organic impurities, on the other hand silicon dioxide and lime crusts are not solved. With this limitation, treatment with KOH is a simple technique for routine use as cleaning method for fragile insect specimens for SEM.     

Real-time confocal imaging, during active air abrasion – substrate cutting

Air abrasion cutting, using particulates accelerated in a controlled compressed gas stream, is currently being re-evaluated as a precision tissue removal technique for dental cavity preparation. The minimal vibrations and heat generated during cutting commend the technique for use in the shaping of fragile or brittle materials that are vulnerable to vibrations and thermal stresses.
Traditional air abrasion studies have relied solely upon post-procedure imaging, and cutting process details have been inferred from the nature of the residual surface. In this paper, however, a real-time confocal microscopic imaging method is described, which for the first time has allowed prior target structure characterization with subsequent imaging of cutting interactions and substrate failure patterns. Using internally focusing long working distance Hill objective lenses, focusing deep to a protective microscope slide and adhesive interfaces, unhindered remote image sampling within the bulk of specimens such as tooth tissue, acrylic and brittle ceramics was possible.
Moreover, areas of active cutting and inactive regions were identified within air abraded cavities during their creation. The characteristics of the finished cut surfaces were demonstrated and confirmed the findings of previous SEM studies. The method allowed direct control over all the known variables influencing cutting with particulate streams.     

切屑形成的基本理论与屑形控制

论述了金属切削过程中切屑变形与卷曲的基本原理 ,分析了塑性金属与脆性金属切屑的不同形成机理 ,提出了控制切屑形状的基本原则     

Application of a laser scalpel to sectioning fragile tissues prior to optical sectioning microscopy and 3D reconstruction

A method is described for the cutting of fragile material with a laser scalpel which minimizes damage to friable materials, making the interior of structures accessible for optical sectioning microscopy or for high resolution X-ray microtomography followed by 3D reconstruction.