Lightning ablation suppression of aircraft carbon/epoxy composite laminates by metal mesh

Three-dimensional finite element (FE) models of carbon/epoxy composite laminates with copper mesh and aluminum mesh protection were established subjected to lightning strike, in which different mesh spacing was selected. Effectiveness of numerical method was verified and impulse current waveforms with different current peaks were applied according to aircraft lightning zones. Thermal-electrical material parameters varying with temperature were added into numerical models. Element deletion method was used to deal with lightning ablation elements of composite structures. The results show that ablation area and depth of composite laminates with metal mesh protection are significantly smaller, which proves good protection effectiveness of metal meshes on anti-lightning strike. The denser the mesh spacing, the better the anti-lightning strike will be. Protection of composite laminates with copper mesh has better effects than that of aluminum mesh. Considering the effect of mesh spacing variation on composite structural weight and anti-lightning strike, the ideal mesh spacing was obtained.     

Werkstoffverhalten und Werkstoffauswahl unter dem Gesichtspunkt der kühlwasserseitigen Korrosionsbeanspruchung von Wärmetauschern

Materials Performance and Materials Selection under the Aspect of Cooling Water Corrosion of Heat Exchangers For the chemical process industry cooling water corrosion problems are of special importance. Of the known corrosion phenomena nearly all can be observed with heat exchangers depending on water quality and material used. By appropriate water treatment, favourable design measures and optimum materials selection the corrosion problem on the cooling water side of heat exchangers can be solved. Water treatment and design measures are only casually delt with in this paper which emphasizes the aspects of materials selection. Using the proper material is of special importance for once-through cooling systems. For this reason the performance of various materials is described, e. g. unalloyed steel, unalloyed steel protected by organic coatings, austenitic 18 Cr-9 Ni-steels, ferritic Cr-steels, ferritic-austenitic steels, copper and copper alloys, titanium. For a variety of operating conditions the materials selection criteria are described. Finally, some aspects of corrosion economics in selecting materials are discussed.     

Anodischer Schutz durch Legierungsmaßnahmen

Anodic protection through alloying. The very heavy demands made on the resistance to corrosion of the metallic materials used in the chemical industry has at all times resulted in attempts to improve this property through special alloying techniques. In such techniques an important part is played by alloying elements which favourably influence the passivation of metals, the reason for this being that most of the materials used owe their resistance to the passive layers which are formed at their surfaces. Those elements which, by reducing over voltages, enable the cathodic reaction to be intensified are particularly important in this connection. They enable the passivating current to be raised and thus have effects similar to those of anodic protection. The effects of such elements, especially of Pt and Pd, on the corrosion behaviour of ferritic and austenetic stainless steels, of titanium, and of lead alloys, and also the opportunities for technical application, are described.     

Korrosionsverhalten von SiC-partikelverstärkten Aluminiumlegierungen

Corrosion Behavior of SiC Particle Reinforced Aluminium Alloys Since two decades Metal Matrix Composites (MMC'S) are a major topic in research and development. They show features, which are superior to those of conventional materials. As in any other composite material the interface metal matrix/reinforcing material is the weak point of these materials. Therefore information on their corrosion behavior is necessary before estimating their possible range of application. The purpose of this project is to gather information on the corrosion behavior of SiC particle reinforced aluminium alloys. The materials examined were alloys of the series 6XXX and 2XXX with varying amounts of SiC particle in comparison to the widely used aluminium alloy 2024. Experiments were performed with uncoated specimens and with specimens protected by a typical aircraft coating. Looking at the uncoated specimens the high copper MMC-alloy has a greater corrosion susceptibility than its matrix alloy. The coating on the MMC's examined has a better corrosion protection effectiveness than the same coating on the matrix alloy AA 2024.     

柔性石墨接地体与金属接地体的耐腐蚀性对比

传统金属接地体受到土壤的电化学腐蚀严重,为此,选择一种新型接地材料——柔性石墨接地体,与钢、铜等常用金属接地体的耐腐蚀性进行对比。根据5种常见土壤的腐蚀特性,采用室内腐蚀模拟试验,通过制备土壤模拟液和细砂模拟我国几种典型土质,对几种接地材料的腐蚀特性进行了研究。同时,针对接地材料腐蚀对接地电阻的影响,分别对相同长度及直径的铜、钢和石墨复合接地体3种接地材料腐蚀前后的接地电阻进行了对比测试。研究表明:石墨复合接地材料不受土壤条件的限制,其防腐蚀特性优于现行的钢、铜等金属接地材料;石墨复合接地材料腐蚀前后,其接地电阻基本无变化。     

Entwicklung einer niedrigschmelzenden Legierung und deren Applikation zum Korrosionsschutz hochfester Stähle

Development of low‐temperature galvanizing and its application for corrosion protection of high‐strength steels Apart from reliability and quality, vehicle safety and cost efficiency are the decisive criteria for automobile manufacturers. Corrosion protection plays a decisive role because it increases the service life. The ultra‐high‐strength steels are materials which exhibit high lightweight potential as well as a very good energy absorption capacity because of their mechanical properties. In connection with the possibility of hot forming, they are predestined for the fabrication of complicated, load‐compatible shapes in the crash‐relevant frame and body construction. The application of these steel qualities has been carried out in structural parts which are protected from corrosion by a hot‐dip coat of FeAl7 – the so‐called Usibor. However, at the moment there is no ready‐for‐production solution for later corrosion protection of already hot‐formed parts. Therefore, a corrosion protection system on the basis of conventional low‐temperature galvanizing processes has been developed and utilized. First, the softening behavior of the highly‐resistant 22MnB5 substrate was analyzed. Afterwards, a galvanizing system was developed and applied. The corrosion protection coatings were characterized with regard to their structure and corrosion protection potential. As a result, a significant improvement of the corrosion behaviour has occurred.     

Electrochemical corrosion monitoring of steel fiber embedded in cement based composites

Steel fibers are commonly used in cement based materials for many applications such as floors, structural elements, repairing works, etc. The chloride-induced corrosion via ingress of seawater may become a risk for performance of the steel fiber reinforced cement based composites. Despite of few studies that have dealt with the corrosion behavior of steel fibers embedded in cement based composites, there are lack of information about the chloride-induced corrosion of steel fibers embedded with sufficient cover in non-cracked matrixes, reactive powder concrete, and especially polymer-modified cement based mortars. The open-circuit potential and corrosion current density of single steel fibers embedded in various cement based matrices were monitored after 200, 400, 600, 1200 wetting-drying cycles in 3.5% NaCl solution. The corrosion and microstructure analyses revealed that the steel fibers can be protected by a well-designed mixture, non-cracked matrix and sufficient cover. However, it could be corroded in long terms depending on the type and the dosage of the polymer latex used. In addition, the residual stresses in the deformed regions of the hooked-end steel fibers is critical in terms of the protection against to chloride-induced corrosion.     

Optimizing survivability of multi-state systems with multi-level protection by multi-processor genetic algorithm

In this paper we consider vulnerable systems which can have different states corresponding to different combinations of available elements composing the system. Each state can be characterized by a performance rate, which is the quantitative measure of a system's ability to perform its task. Both the impact of external factors (stress) and internal causes (failures) affect system survivability, which is determined as probability of meeting a given demand.In order to increase the survivability of the system, a multi-level protection is applied to its subsystems. This means that a subsystem and its inner level of protection are in their turn protected by the protection of an outer level. This double-protected subsystem has its outer protection and so forth. In such systems, the protected subsystems can be destroyed only if all of the levels of their protection are destroyed. Each level of protection can be destroyed only if all of the outer levels of protection are destroyed.We formulate the problem of finding the structure of series–parallel multi-state system (including choice of system elements, choice of structure of multi-level protection and choice of protection methods) in order to achieve a desired level of system survivability by the minimal cost. An algorithm based on the universal generating function method is used for determination of the system survivability. A multi-processor version of genetic algorithm is used as optimization tool in order to solve the structure optimization problem. An application example is presented to illustrate the procedure presented in this paper.     

金属间化合物的高温腐蚀与防护

综述了有序金属间化合物，主要是Ｎｉ－Ａｌ，Ｔｉ－Ａｌ和Ｆｅ－Ａｌ系金属间化合物高温腐蚀与防护方面的研究结果，包括它们的氧化腐蚀机理、合金元素对其氧化腐蚀性能的影响以及它们所需的高温涂层等。     

Optimal multilevel protection in series–parallel systems

This paper considers vulnerable systems that can have different states corresponding to different combinations of available elements composing the system. Each state can be characterized by a performance rate, which is the quantitative measure of a system's ability to perform its task. Both the impact of external factors (attack) and internal causes (failures) affect system survivability, which is determined as the probability of meeting a given demand.In order to increase the system's survivability a multilevel protection is applied to its subsystems. This means that a subsystem and its inner level of protection are in their turn protected by the protection of an outer level. This double-protected subsystem has its outer protection and so forth. In such systems, the protected subsystems can be destroyed only if all of the levels of their protection are destroyed. Each level of protection can be destroyed only if all of the outer levels of protection are destroyed.In such systems, different protections play different roles in providing for the system's survivability. Subject to budget limitations a question arises which protections should be applied to obtain the desired survivability. An algorithm for solving the protection cost minimization problem subject to survivability constraint is presented in the paper. The algorithm is based on a universal generating function technique used for system survivability evaluation and on a genetic algorithm used as an optimization engine.Illustrative example is presented.     

海底生物燃料电池中304不锈钢(06Cr19Ni10)阴极腐蚀保护作用研究

以304不锈钢(06Cr19Ni10)作为阴极构建海底生物燃料电池装置,研究了该电池对其海水腐蚀的阴极保护作用。自然腐蚀状态下不锈钢电位为-260 mV,阴极保护试样为-340 mV。荧光显微镜(FM)和扫描电镜(SEM)观察结果表明,两组试样的表面微生物附着情况差别不大,阴极保护试样表面腐蚀程度较低。电化学阻抗法及极化曲线测试表明,通电保护试样的阻抗值随时间增加逐渐增大,腐蚀电流密度Icorr逐渐减小,保护试样的抗腐蚀能力增强,电池装置对不锈钢阴极起到一定的保护作用。     

Hot Corrosion of Protective Coatings

Improvement in efficiencies of gas turbine engines requires a significant increase of gas inlet temperatures. This results in an increased service temperature for blade materials and consequently in enhanced oxidation and hot corrosion attack of the blade coatings, which are usually of MCrAlY type where M is Ni, Co or NiCo. This type of coating can provide protection against oxidation and hot corrosion and act as a bond coat for thermal barrier coating systems. In both cases slow growth rates and optimum adherence of the alumina scales forming on the MCrAlY coatings during high temperature exposure are significant for component life. The above mentioned properties for the alumina scales strongly depend on the coating base composition as well as on the presence of minor alloying elements. In the present paper the performance of existing superalloys during hot corrosion is briefly described followed by the results obtained on hot corrosion of MCRAlY type coatings explaining the effect of trace elements on the life of coatings in the presence of NaCl and vanadium containing environments. Optimum thickness to improve the life of superalloys with NiCoCrAlY as a bond coat and yttria stabilized zirconia thermal barrier coatings has been identified. Based on the results, an electrochemical mechanism is proposed and shows that hot corrosion of protective coatings is an electrochemical phenomenon. Hence electrochemical techniques appear to be quite useful in evaluating the coatings for hot corrosion resistance.     

油气管线钢腐蚀研究现状

管道运输以其经济成本低、安全性及自动化程度高等显著优势,被广泛应用于油气领域。管线钢是一类运输油气资源的特种钢材,表现出较为优异的服役性能。腐蚀作为影响材料的三大主要因素之一,会对管道材料产生巨大影响,进行管线钢腐蚀行为和机理研究极具意义。管线钢服役环境繁杂,既用于埋地管道铺设,也在海洋环境中具有较大发展潜力。影响管线钢耐蚀性能的因素主要包括材料自身性质、服役环境（土壤及海洋）、单一酸性气体、油气性质、缓蚀剂和外加载荷等。不同因素之间存在一定程度的协同与拮抗作用,相比于单因素作用,多因素之间的耦合效果会大幅改变管线钢的腐蚀情况。概述了管线钢最新腐蚀研究现状,阐述了单因素的单独作用和多因素之间的耦合作用,简要分析了管线钢在腐蚀研究方面所面临的困难,以及对未来研究的展望,以期为管线钢腐蚀防护提供一定的思路和解决措施。     

不同防护形式复合材料板雷击损伤分区特性

基于A+B+C+D 4种标准雷电流波形的联合作用,开展了不同防护形式复合材料板雷击试验。考虑放电通道物理特性,分析放电通道与复合材料表面间的作用过程,将复合材料表面损伤区域分解成初始附着区、附着传导区、附着扩展区、二次附着区和扫掠损伤区,并对未防护基准件、局部喷铝、全喷铝防护件及铜网防护件4类板的各区域进行了损伤特性分析。结果表明:复合材料表面损伤是强电磁场条件下放电通道热电物理特性与复合材料表面热电特性及电荷分布的共同作用结果;复合材料表面铝层喷涂方式、厚度以及均匀程度均影响表面损伤的对称性和损伤分区特性;铜网防护造成复合材料板表面粗糙使得表面损伤分区复杂;表面电荷累积特性和分布的均匀程度直接影响二次附着区和扫掠损伤区的分布;复合材料表面雷击损伤包括纤维升华、断裂、起毛,基体炭化熔融、烧蚀,材料分层、剥落以及防护材料的熔融汽化和断裂等。分析结果可以用于复合材料雷击防护定性设计。     

Fire protection systems for building floors made of pultruded GFRP profiles – Part 2: Modeling of thermomechanical responses

A recently developed thermomechanical model to predict the time-dependent thermal and mechanical responses of pultruded glass fiber-reinforced polymer (GFRP) profiles subjected to fire was extended to include the beneficial effects of passive fire protection systems. The model extension was validated by comparing predicted and measured thermomechanical responses of pultruded GFRP tubes subjected to four-point bending and exposed to an ISO834 fire from their underside. The profiles were protected using passive and active methods, including a calcium silicate board, a vermiculite/perlite-based mortar, and a water-cooling system. Variations resulted mainly from the unavailability of accurate time-dependent thermophysical properties for the protection materials. The benefits provided by the fire protection systems could be quantified and the model therefore can be used for the selection and design of passive fire protection measures.     

用于地下金属管网的智能控制阴极保护装置

为了解决在自然条件下地下管网容易受腐蚀的问题,采用基于腐蚀电化学原理的防腐层缺陷检测技术和控制技术并应用于阴极保护装置中通过对被保护金属管道施加阴极电流,使其电极电位负移,减弱金属由原子态自发变为离子态的趋势,因而从根本上抑制了腐蚀的发生．应用智能控制算法使被保护管道达到最佳保护电位．通过人工模拟区域性阴极保护现场实验,被保护管道电位达到国家标准的保护电位．该阴极保护装置采用了二级计算机控制管理系统、双脉冲电源系统以及无线遥测系统等设计思想.     

Protection Survivability Importance in Systems with Multilevel Protection

This paper considers systems that can have different states corresponding to different combinations of available elements constituting the system. Each state can be characterized by a performance rate, which is the quantitative measure of a system's ability to perform its task. Both the impact of external factors (attack) and internal causes (failures) affect system survivability, which is determined as the probability of meeting a given demand. In order to increase the system's survivability a multilevel protection is applied to its subsystems. This means that a subsystem and its inner level of protection are in turn protected by the protection of an outer level. This double‐protected subsystem has its outer protection and so forth. In such systems, the protected subsystems can be destroyed only if all of the levels of their protection are destroyed. Each level of protection can be destroyed only if all of the outer levels of protection are destroyed. In such systems, different protections play different roles in providing for the system's survivability. The evaluation of the relative influence of the protections' survivability on the survivability of the entire system provides useful information about the importance of these protections. The protection survivability importance index is introduced in order to evaluate this influence and an algorithm for evaluating the index is presented. The relevancy of protection is also considered. Illustrative examples are presented. Copyright © 2004 John Wiley & Sons, Ltd.     

Factors affecting cathodic-protection interference

A 3D theoretical simulation and analysis of DC stray-current corrosion (SCC) is introduced. The use of boundary element analysis system (BEASY) has allowed cathodic protection (CP) interference to be assessed in terms of the normal current density, which is directly proportional to the corrosion rate. Different real structures consisting of pipelines and/or well casings are simulated to investigate the factors affecting four types of CP interferences, namely, anodic, cathodic, combined and induced, with special emphasis on the cathodic one. The results reveal that the application of impressed current CP systems creates DC SCC on other nearby unprotected structures. This is an inherent potential problem with the application of such systems which dominates with decreasing soil conductivity, and/or increasing the anode current density and its proximity to the protected structures. On the contrary, SCC can be reduced by using multi-groundbed anodes. In addition, it is found that the cathodic interference is more serious than anodic one, and the combined and induced interferences can also cause severe corrosion. Finally, it can be concluded that the BEASY software is a very helpful tool for future planning before installing any structure, where it gives the possible CP interferences on any nearby unprotected metallic structures.     

Effect of Ammonia and Sulphide Environment on 90/10 and 70/30 Cupronickel Alloy

Copper nickel alloys 90/10 and 70/30 are used extensively in saltwater systems operating on marine platforms and offer high corrosion and biofouling resistance. However, systems using these materials were reported to fail prematurely. Preliminary investigations revealed pollution of harbor waters with tangible levels of ammonia and sulphides which was reported to be the primary cause of failure. The present author(s) have performed laboratory and field investigations to identify the stress-material-environment interaction of the copper nickel alloys extensively in use on seawater system of marine platforms. Results obtained point to the fact that polluted seawaters can affect the material properties of the alloy leading to premature failure(s) of systems at stresses well below the designed stress. The paper presents the correlation of the results of the laboratory and field tests of 90/10 and 70/30 copper–nickel alloys in seawaters polluted with ammonia and sulphide pollutants.     

含盐体系中有机铜缓蚀剂的研究进展

叙述了含盐体系中各种有机类铜缓蚀剂的国内外研究进展,阐述了有机类铜缓蚀剂的缓蚀机理和协同作用机理,并展望了铜缓蚀剂新的研究和发展方向。认为应利用现代先进的分析测试技术从分子和原子的水平上研究缓蚀剂在铜表面的行为和作用机理,加强现有缓蚀剂品种的复配技术和绿色环保型缓蚀剂研究。