混凝土中钢筋锈蚀检测的探讨

桥梁混凝土中钢筋锈蚀是影响桥梁混凝土结构耐久性的一个重要问题,也是桥梁安全鉴定过程中经常遇到的问题.结合工程结构安全检测实践,通过对混凝土中钢筋锈蚀、保护层厚度、碳化深度、密实度进行检测,进一步证明了钢筋锈蚀的影响因素同混凝土保护层厚度、密实度、碳化深度有着直接的关系,并对提高混凝土中钢筋锈蚀概率大小和结构锈蚀性判断的可靠程度进行了探讨.     

钢筋保护层测量仪检测中常见问题分析

钢筋保护层测量仪在工程质量验收中作用重大,本文阐述了该仪器在依据规范进行检测中常见的几个问题,并展开分析讨论。     

混凝十桥梁钢筋保护层厚度检测刍议

本文通过介绍钢筋保护层厚度的检测方法及注意事项，列举施工阶段及养护运营阶段之间相应规范对钢筋保护层厚度的评定标准，并进行了保护层评定的实例分析，指出了当前不同规范对保护层厚度评定结论间的冲突，提出了各规范间结论协调一致的要求及进一步研究的建议。     

钢筋保护层厚度取值的对比研究

本文分析了钢筋保护层厚度的重要性；对国内外规范中对钢筋保护层厚度的取值进行了对比；提出我国应适当提高钢筋保护层厚度的取值；对预应力钢筋和非预应力钢筋的钢筋保护层厚度分别规定；钢筋保护层厚度的取值应考虑施工偏差。     

钢筋保护层厚度测量仪标准块的研制

标准块是实现钢筋保护层厚度测量仪量值溯源准确可靠的重要保证。针对目前市面上还没有按JJF 1224—2009《钢筋保护层、楼板厚度测量仪校准规范》要求设计的标准块正式销售的情况,通过对标准块结构、钢筋直径及保护层厚度、保护层材质、制作工艺等的设计,研制出钢筋保护层厚度测量仪校准标准块,并通过上级溯源及标准块的重复性和稳定性试验考核合格,可以方便、可靠的实现钢筋保护层厚度测量仪校准,完善了本地区钢筋保护层厚度测量仪的量值溯源体系。     

控制钢筋保护层厚度的有效措施

在桥梁结构中,钢筋不断锈蚀,宵效截面不断减小,桥梁结构承载力不断下降,钢筋混凝土构件丧失基本承载能力。控制好钢筋保护层厚度有利于防止钢筋锈蚀,保证混凝土结构耐久性和使用寿命。本文结合工程实际,通过四控一检,在钢筋保护层厚度控制方面作如下简述。     

基于电磁学原理的钢筋保护层厚度测量法不确定度分析方法研究

介绍了用于混凝上结构工程质量检测和工程验收的基于电磁学原理的钢筋保护层厚度测量(仪)法,分析了该类测量仪器地不同和所依据的不同标准带来的差异.提出了统一的测量方法、以不确定分析方法统一对该类测量法进行评定.     

海工结构服役寿命及保护层开裂模式细观数值模拟

通过在钢筋与混凝土交界面处施加时变边界位移建立非均匀锈蚀钢筋锈胀模型,其中混凝土损伤本构采用指数应力软化模型,时变边界位移采用Faraday定律对氯离子浓度积分计算得到.参数化分析保护层厚度、钢筋位置、钢筋直径等因素对服役寿命及保护层开裂模式的影响.研究结果表明,服役寿命随保护层厚度增加而增长,而且增加幅度逐步增大,而钢筋直径变化对服役寿命影响较小,角部钢筋锈蚀则导致结构服役寿命缩短;中部钢筋的锈蚀使得保护层出现三条主裂缝,当保护层较小,保护层破坏模式为凸起式破坏,保护层较大时则将出现层裂;同时,角部钢筋锈蚀将在保护层内形成两条主裂纹,最终导致角部保护层脱落.     

混凝土保护层胀裂时刻钢筋锈蚀深度的理论模型

钢筋锈蚀产物产生的膨胀力往往会引起钢筋混凝土结构中混凝土保护层的开裂,为了研究混凝土保护层胀裂时刻钢筋的锈蚀深度,在假设钢筋为均匀锈蚀的前提下,以c/d0(c为混凝土保护层厚度,d0为钢筋的原始直径)作为控制指标,分别基于弹塑性力学和断裂力学的基本理论,建立了混凝土保护层开裂时刻钢筋临界锈蚀深度的理论计算模型。通过已有文献的多组试验数据对计算模型进行了验证,结果表明理论模型计算结果与试验结果能够较好地吻合。     

浅析建筑钢材的锈蚀及防止措施

建筑钢材可分为钢结构用钢材和钢筋混凝土结构用钢筋两类。钢材的锈蚀,指其表面与周围介质发生化学反应而遭到的破坏。在钢筋混凝土中,由于钢筋的锈蚀,将使混凝土的保护层膨胀出现裂纹,严重时混凝土保护层脱落,钢筋脱离,使钢筋和混凝土之间的粘结应力损失或完全丧失,危急结构的安全,因此钢筋的锈蚀对钢筋混凝土结构的使用寿命有很大的影响。     

感光材料分辨力测定实验研究

使用ＰＩ－Ｃ感光材料分辨力测定仪,测定了感光材料分辨力。测定试验不仅证明感光材料分辨力测定仪器操作稳定可靠、重复性好,而且测定实验加深了对感光材料的感光影象特性的研究。实验表明,最佳焦面实际集中在各种胶片乳剂层表层。     

Sur quelques facteurs intervenant dans le bombardement de couches pulvérisées

The voltage distributions of the discharges employed in sputtering are reviewed. In bias sputtering the voltage difference between the substrates and the discharge plasma is used to obtain film bombardment by charged particles during growth. This voltage difference, which is the effective bias, is related to the externally applied bias and to the voltage distribution for the discharge in various sputtering systems. It is shown that the effective bias is generally different from the external bias and may even exist without it; this makes the externally applied bias illusory as a process controlling parameter. Both positive and negative biasing is discussed. Due to the inconvenience of using positive values of the effective bias in film deposition, only negative values of the effective bias are dealt with when discussing the measurement of the effective bias and the energy distribution of ions bombarding the films.     

Electron Beam Bias for Thin Capacitor Web Coating

Electron beam induced bias was applied for high speed, high quality coating of ultra thin capacitor web. Electron beam charging applies a static charge to the film and allows higher bias voltages than conventional bias systems. Using a numerical calculation of the electrical and thermal forces at work it can be shown that electron beam bias results in better cooling and lower peak temperatures of the film. The advantages for the film coating process are higher possible coating speeds and/or better film quality. Further, the effect of pinholes during coating is much reduced.     

抽样引起的测量不确定度评定

若测量值定义为抽样目标中的分析物浓度,那么与抽样相关的不确定性必然导致最终测量结果的不确定度。抽样不确定度主要来源于抽样目标的不均匀性、抽样方案不明确、抽样和样品制备过程中引入的交叉污染、分析物损失等。以欧洲分析化学会的指南为基础,介绍了抽样不确定度评定的经验方法,该方法将测量不确定度来源区分为抽样过程和分析过程中的随机效应与系统效应。通过实例说明了如何通过重复实验和方差分析来量化抽样和分析过程中的随机效应,从而评估抽样和样品制备所引入的不确定度。     

利用线阵CCD非接触测量材料变形量的方法

用线阵CCD作为光电传感器非接触测量材料拉伸过程中的变形量，不但比常规的引伸计测量的方法更客观，而且可以测量材料拉伸变形到断的全过程。该方法能在X和Y两上方向上同时测量材料变形量，可以获得材料在实验的全过程中两上方向的“应力－应变”关系曲线。采用CCD拼接技术，测量精度可达到1μm，测量范围80mm。     

The Grid Method for In‐plane Displacement and Strain Measurement: A Review and Analysis

The grid method is a technique suitable for the measurement of in‐plane displacement and strain components on specimens undergoing a small deformation. It relies on a regular marking of the surfaces under investigation. Various techniques are proposed in the literature to retrieve these sought quantities from images of regular markings, but recent advances show that techniques developed initially to process fringe patterns lead to the best results. The grid method features a good compromise between measurement resolution and spatial resolution, thus making it an efficient tool to characterise strain gradients. Another advantage of this technique is the ability to establish closed‐form expressions between its main metrological characteristics, thus enabling to predict them within certain limits. In this context, the objective of this paper is to give the state of the art in the grid method, the information being currently spread out in the literature. We propose first to recall various techniques that were used in the past to process grid images, to focus progressively on the one that is the most used in recent examples: the windowed Fourier transform. From a practical point of view, surfaces under investigation must be marked with grids, so the techniques available to mark specimens with grids are presented. Then we gather the information available in the recent literature to synthesise the connection between three important characteristics of full‐field measurement techniques: the spatial resolution, the measurement resolution and the measurement bias. Some practical information is then offered to help the readers who discover this technique to start using it. In particular, programmes used here to process the grid images are offered to the readers on a dedicated website. We finally present some recent examples available in the literature to highlight the effectiveness of the grid method for in‐plane displacement and strain measurement in real situations.     

Numerical and experimental investigation on temperature distribution of the discontinuous welding

The main objective of this study is to generate new understanding and improve computer methods for calculating the thermal cycles and temperature distribution of 5A06 aluminum alloy structure during discontinuous welding. Predicting the thermal cycle also provides an estimate of the weld penetration and weld width. The submodeling technique was used to save computing time and improve calculation accuracy. The arc heat input was applied in the weld zone using different forms of surface, volumetric and combined heat flux distribution functions. In order to validate the thermal simulation model, temperature distribution at the weld backside was precisely measured by infrared thermography during the welding process. The simulation results showed that the model is quite sensitive to the energy distribution during the welding process, the effects of the pre-heating and re-heating are significant. The present simulation model can be used as a proper tool to investigate the effect of different metal inertia gas (MIG) process parameters.     

Root cause analysis during process development using Joint-Y PLS

The original purpose of the JYPLS model was to aid product transfer and scale-up. This work demonstrates that the JYPLS model is also well suited to analyze data from a process in development where the number and type of sensors and sensor locations are also being decided. The specific application in this case was to determine the root cause for a bias found during the development of a multivariate calibration model for a Near Infrared (NIR) instrument. The calibration model was built in parallel with the development of the manufacturing process itself. Each time the calibration model was tested with data from a new batch run, a non-explained bias was observed. Laboratory results on samples gathered from the process show that the NIR signal itself was biased and not the actual concentration of the constituent. Data on the processing conditions were collected for all the batches and included in the JYPLS model along with NIR and lab results. The loadings and scores from the JYPLS model were interpreted to isolate the root cause of the observed drift in the calibration model. This work discusses the general approach and presents the sequence of diagnostics used to analyze the different campaigns during process development. This should be applicable to other scenarios in process development where the data has the same architecture.     

Numerical and Experimental Investigations on Deep Drawing of G1151 Carbon Fiber Woven Composites

This study proposes to simulate the deep drawing on carbon woven composites in order to reduce the manufacturing cost and waste of composite material during the stamping process, The multi-scale anisotropic approach of woven composite was used to develop a finite element model for simulating the orientation of fibers accurately and predicting the deformation of composite during mechanical tests and forming process. The proposed experimental investigation for bias test and hemispherical deep drawing process is investigated in the G1151 Interlock. The mechanical properties of carbon fiber have great influence on the deformation of carbon fiber composites. In this study, shear angle–displacement curves and shear load–shear angle curves were obtained from a bias extension test. Deep drawing experiments and simulation were conducted, and the shear load–displacement curves under different forming depths and shear angle–displacement curves were obtained. The results showed that the compression and shear between fibers bundles were the main deformation mechanism of carbon fiber woven composite, as well as the maximum shear angle for the composites with G1151 woven fiber was 58°. In addition, during the drawing process, it has been found that the forming depth has a significant influence on the drawing force. It increases rapidly with the increasing of forming depth. In this approach the suitable forming depth deep drawing of the sheet carbon fiber woven composite was approximately 45 mm.     

时差法测频问题分析与修正

针对现行的JJG 292-2009《铷原子频率标准检定规程》中采用时差法测量得出相对平均频率偏差的方法在两种特殊情况下可能会出现错误的问题,从原理上分析了产生错误的原因,推导得到了满足各种情况的计算公式,并通过具体数值例子说明本文讨论的必要性。