GC—4超高强度钢应力腐蚀裂纹扩展特性

采用BL-WOL楔力加载平面应变断裂试样,研究了GC-4(40 CrMnSiMoVA) 超高强度钢在3.5％NaCl溶液和蒸馏水中的应力腐蚀裂纹扩展特性,测定了不同试验条件下的应力腐蚀开裂门槛值K_(ISCC)和裂纹扩展速度(da/dt)_(II)。结果表明,在环境介质中的应力强度因子门槛值K_(ISCC)仅及该钢断裂韧性K_(IC)的1/5～1/4。介质成份、电极电位、环境温度及热处理规范等都对裂纹扩展速度(da/dt)_(II) 有显著影响。分析表明,氢脆是导致GC-4.钢应力腐蚀开裂的重要原因之一。     

力学-电化学交互作用下E690钢的腐蚀疲劳裂纹扩展速率理论模型

基于腐蚀疲劳中力学-电化学交互作用过程的能量转换,利用能量守恒、电化学热力学及腐蚀电化学原理,研究在腐蚀疲劳体系中动能、势能以及阳极溶解电化学能的变化,建立E690高强钢的腐蚀疲劳裂纹扩展速率理论模型,并通过腐蚀疲劳裂纹扩展试验验证该理论模型的准确性。结果表明：质量分数3.5%NaCl溶液会加速E690高强钢疲劳裂纹初期的扩展,降低疲劳寿命,应力比的提高会明显加速腐蚀疲劳裂纹扩展,同时降低裂纹扩展门槛值;理论模型计算得到疲劳裂纹扩展速率与试验结果基本吻合,相对误差小于10%,说明该模型可以很好地描述E690高强钢的腐蚀疲劳裂纹扩展行为。     

环境断裂动力学及寿命控制

提出了环境断裂动力学的概念，阐述了其分类与研究方法，以腐蚀疲劳长裂纹扩展为例，提出宏观裂纹扩展动力学与局部扩散，迁移动力学，化学和电化学反应动力学，以及力学条件改变所致物质对流动力学的联系，通过实验证实了其合理性，从断裂控制正是控制这些动力学过程及其限制性因素的观点出发，用外加极化电位的方法控制腐蚀疲劳长裂纹扩展过程的结果证实了其正确性，以此思路，根据具体特征可实现环断裂的全寿命控制。     

船用螺旋桨铜合金的腐蚀疲劳性能

本文模拟船用螺旋浆的受力状态及工作环境,采用小试样,低应力的高周疲劳进行裂纹扩展试验,来研究螺旋浆铜合金材料的腐蚀疲劳性能。重点测定裂纹扩展速率da/dN,并通过da/dN来估算疲劳裂纹扩展寿命,评定五种铜合金的优劣。探讨了它们的常规力学性能与腐蚀疲劳能之间的关系。对腐蚀疲劳断口进行了分析。同时比较了黄铜的锌当量及晶粒度对腐蚀疲劳性能的影响。     

LD10CS腐蚀疲劳裂纹扩展速率评价的可靠性模型

腐蚀损伤会加速疲劳载荷下的飞机铝合金结构裂纹的萌生和扩展,威胁结构安全性。针对腐蚀影响下的疲劳裂纹扩展的随机性本质,对预腐蚀LD10CS合金的预腐蚀疲劳试验进行了数据分析,提出了基于可靠性的腐蚀裂纹扩展速率表征方法,与试验结果对比表明,该方法可以给出LD10CS腐蚀疲劳裂纹扩展速率的上下限,进而给出该种材料铝合金构件的疲劳裂纹扩展寿命的上下限,为评估铝合金构件的寿命提供了依据。     

应力比对S135钻杆钢腐蚀疲劳行为的影响

利用疲劳试验机和扫描电镜研究了在弱碱性介质(质量分数为3.0%的KCl溶液)中不同应力比R(0.1,0.3,0.5,0.7)对S135钻杆钢腐蚀疲劳行为的影响,并得到了该钻杆钢腐蚀疲劳裂纹扩展表达式和疲劳裂纹临界撕裂点的应力强度因子幅值ΔK与R的关系式。结果表明:随着R的增大,试样裂纹扩展临界撕裂点和最终撕裂点对应的ΔK逐渐减小(R和临界撕裂点的ΔK值之间呈明显的线性关系),试样的腐蚀疲劳裂纹扩展速率增大,腐蚀疲劳相对寿命减小,裂纹开裂由疲劳条带扩展机制转化为解理扩展机制。     

加载频率对航空铝合金腐蚀疲劳裂纹扩展速率的影响

提出腐蚀疲劳频率影响因子概念,建立了考虑加载频率影响的LC9铝合金腐蚀疲劳裂纹扩展速率模型,并进行了试验验证。结果表明:腐蚀疲劳频率影响因子随加载频率的变化可以用指数形式表达,能够反映出加载频率对于腐蚀疲劳裂纹扩展的影响;腐蚀损伤会显著降低裂纹扩展门槛值;基于该模型得到处于稳态扩展区的腐蚀疲劳裂纹扩展速率的预测值与试验结果吻合程度良好,对于航空铝合金构件腐蚀疲劳寿命评估具有参考价值。     

腐蚀预损伤对铝合金小裂纹行为影响研究

研究了不同腐蚀预损伤对新型高强铝合金小裂纹行为的影响。小裂纹试验采用单边缺口拉伸试样（SENT）,在试样半圆形缺口根部预制直径大小为100—300μm的单腐蚀坑,后在空气环境进行疲劳小裂纹实验,实验在R=0．5恒幅载荷下,采用复型法观测小裂纹的萌生及扩展情况。结果表明,与预腐蚀24h试样相比,预腐蚀240h试样产生的裂纹数量较少,裂纹萌生与扩展较快。预腐蚀240h试样裂纹绝大多数萌生于腐蚀坑处而预腐蚀24h试样并未出现类似特性。预腐蚀240h试样未显现明显的小裂纹效应,预腐蚀24h试样有较明显的小裂纹效应出现。文中还通过引入参数aT对腐蚀时间与小裂纹受微观组织影响程度的关系进行了描述。相较预腐蚀24h试样预腐蚀的240h试样的aT更短,小裂纹受微观组织影响也更小。     

预腐蚀7A09铝合金腐蚀坑处萌生疲劳裂纹扩展深度的估算

含初始缺陷铝合金结构的寿命评估方法大多需要用到裂纹扩展深度这一难以直接测得的参数,为了找到其与表面裂纹长度之间的关系,对预腐蚀7A09铝合金进行疲劳试验,并利用扫描电镜结合能谱仪进行疲劳断口分析,发现了腐蚀坑处萌生裂纹沿着深度方向的扩展规律。结果表明:7A09铝合金的疲劳断口多呈脆性断裂特征,富集的增强相反而会成为脆性相,降低材料的塑性变形能力;对于单一裂纹源主导的疲劳断裂,其内部扩展深度与表面裂纹长度之间存在线性关系,通过检测构件中裂纹的表面长度可以获得其扩展深度,对于结构剩余寿命的估算具有参考价值;对于多源疲劳,裂纹扩展长度与深度间无确定的关系。。     

腐蚀环境对飞机梁结构连接件疲劳寿命和裂纹扩展的影响

借助腐蚀环境谱与疲劳载荷谱交替作用来模拟沿海飞机停放-飞行-停放过程。以飞机梁结构连接件的下壁板为主要研究对象,采用标记载荷法和详细目视检测法监测其裂纹的扩展状况,并采用GE5显微镜观测断口形貌。分析了腐蚀环境对梁结构连接件疲劳寿命与裂纹扩展的影响。试验结果表明:在形成穿透裂纹的初始阶段,试验件受到表面的防护漆以及连接处的密封胶保护,腐蚀环境在该阶段对梁结构连接件的疲劳寿命影响不明显,与非腐蚀试验相比, 该阶段的寿命仅缩短了5.5％;在穿透裂纹的扩展阶段,腐蚀环境加速了穿透裂纹的扩展过程,同时还加剧了穿透裂纹扩展过程的分散性,与非腐蚀试验相比,穿透裂纹的扩展寿命缩短了23.1％。     

民用飞机电气线路防火研究

根据民用飞机相关适航规章要求,针对各防火区域的环境特点,从防火区域电气线路设计的方法和注意事项、电气线路安装可靠性分析等方面进行了论述,分别指出了几种防火区域防火工作的重点,可为电气线路防火设计提供参考和借鉴。     

民用飞机电气线路防火研究

根据民用飞机相关适航规章要求,针对各防火区域的环境特点,从防火区域电气线路设计的方法和注意事项、电气线路安装可靠性分析等方面进行了论述,分别指出了几种防火区域防火工作的重点,可为电气线路防火设计提供参考和借鉴。     

Effect of Imidazolium Ionic Liquid Additives on Lubrication Performance of Propylene Carbonate under Different Electrical Potentials

Three different ionic liquids (ILs), 1-octyl-3-methylimidazolium tetrafluoroborate ([OMIm]BF₄), 1-octyl-3-methylimidazolium hexafluorophosphate ([OMIm]PF₆) and 1-decyl-3-methylimidazolium hexafluorophosphate ([DMIm]PF₆), were used as additives in the base ester propylene carbonate (PC) for the lubrication of AISI 4340 steel surfaces. Ball-on-disk friction tests were done under different electrical potentials to investigate the synergetic effect of IL concentration and electrical potential on lubrication performance, and electrochemical and ellipsometric tests were conducted to explore the adsorption of IL additives at different potentials. The friction reduction and anti-wear performance of the tested three IL/PC solutions illustrated similar dependence on electrical potential. In the potential range from ?0.6 to +0.6 V, friction coefficient increases rapidly. When the potential is more negative than ?0.6 V, friction coefficient is at the lower level of about 0.13. When the potential is greater than +0.6 V, friction coefficient is at the higher level of about 0.2. The electrochemical test results show that [DMIm]PF₆/PC solution is the lowest in corrosion against AISI 4340 steel among the three tested lubricants. The wear of steel surface in 0.5 mM [DMIm]PF₆/PC solution is reduced when electrical potential is shifted to ?1.0 V comparing with that at open-circuit potential. The potential-dependent friction and wear behaviors are explained in terms of the variation of the adsorbed ion species and the surface concentration of the adsorbed ions under different additive concentration and electrical potential conditions.     

EDM放电位置在线检测的电位差法研究

本文深入地研究了在电火花加工过程中利用电位差法在线检测放电位置的方法，推导了电位差与放电位置的关系式，绘制了关系曲线，并与实验结果进行了对经，证明该检测方法的灵敏度只与电极材料及电极形状和结构有关，不受脉冲宽度，供电分支导线长度的影响。     

化工企业用电接地故障危害及防范措施研究

故障电流或电压、PE、PEN线接线端子连接不实等低压配电系统的电气线路和设备的接地故障会诱发电气火灾、经济和财产损失以及人员伤亡事故。文中对低压配电系统的接地形式、接地故障保护的条件、电位联结以及安全检测和管理制度进行了分析。     

新型能量回收式液压举升系统

作者开发了一种带有能量回收功能的重物举升液压系统,已成功地应用于“摇头飞椅”游艺中。该系统在上升过程中通过液压系统将电能转变为机械势能,在下降过程中则将机械势能变成电能输回电网。该系统不仅可以节约能量,而且在重物很重时不用大量散热。     

Semiconductor devices "from inside"

Operation of any semiconductor device can be presented by unique configuration of the electrical field (potential) and charge (doping) distribution within the device. More specifically, the status of operation is described by the quasi-Fermi energy (QFE) profile across the device. Visualization of the dynamic operation of the device and quantitative measurements of the QFE profile is provided by differential voltage contrast (DVC), which is a modification of the secondary electron imaging in a scanning electron microscope (SEM). The DVC consists of storing two images of a tested semiconductor device. Exposed to the electron beam is a cross section, for example, of a field effect transistor (FET). The first image, covering the entire inside of the FET from source to drain, is taken when the device is not biased. The second image of the same area is taken when the transistor is biased. The secondary electron signal is enhanced or retarded by actual distribution of a potential across the tested device. Subtraction pixel by pixel of the two carefully aligned images removes morphologic contrast from the screen, takes away surface features and contamination of the sample, and reveals the contribution of the electrical field to the changes of contrast. The calibration procedure allows measurement of the potential distribution with a precision of 0.05 V. The first derivative of a potential profile provides for distribution of the electrical field and the second derivative gives the doping profile across the tested device. A variety of semiconductor devices such as p-n junctions, Zener diodes, MOSFET's, MESFET's, solar cells and optical detectors, quantum well lasers, etc., were tested. Videotaping of the tested devices allows us to observe the changes in the electrical field and charge distribution as the device operates in a wide range of electrical or optical signals.     

Influence of different electrical boundary conditions on the elasticity solutions of piezoelectric plane beam

Influence of different electrical boundary conditions (BCs) on the elasticity solutions of piezoelectric plane beam (PPB) is investigated using analytical technique. The first case is considering electrical displacement of the two longitudinal sides of PPB. The second case is electrical potential. Firstly, the unified equations to obtain the elasticity solutions of PPB corresponding to these two cases are given briefly. Secondly, two examples are given to verify the correctness of the theoretical formulations presented in this paper. Finally, the responses of PPB acted by the same mechanical loads but with different electrical BCs are compared.     

Comparative measurement of the breakup length of liquid jets in airblast atomisers using optical connectivity,electrical connectivity and shadowgraphy

A comparative examination of the optical connectivity, electrical connectivity and shadowgraphy techniques for the measurement of the break-up length of atomising liquid jets from a co-axial airblast atomiser is presented. The atomiser was operated over air-to-liquid Momentum Ratios between 27 and 335 and Momentum Flux Ratios between 0.67 and 8.27. Shadowgraphy records instantaneous images of the shadow of the atomising liquid jet when it is back-illuminated by a light source. The electrical connectivity uses the continuity of an electrically conducting atomising liquid jet to measure the potential during the presence of an electrical connection between the spray nozzle and a probe further downstream. The optical connectivity visualises the atomising liquid jet, doped with a fluorescing dye, as it is illuminated from within the nozzle using a laser beam. Comparison of the measured breakup lengths with time resolved shadowgraphy, optical connectivity and electrical connectivity, following the proposed novel processing of the time-dependent potential, showed that the mean values are all within ±15% of each other. The advantages and limitations of each technique are discussed.     

Fatigue testing and evaluation for coated stell belts based on electrical method

Based on analyzing the reasons leading to electrical resistance change of an in-service steel wire rope, an experimental system is developed to determine the potential strength degradation of coated steel belts by monitoring the encapsulated ropes’ electrical resistance as well as environmental temperature. The temperature is used to compensate the electrical resistance and get an identical evaluation criterion under an assumed temperature. Research results demonstrate that electrical resistance of ropes will increase as the fretting wear and fatigue damage become more serious with reciprocating cycles increasing. A model of resistance variance with the cycles has been established. Experiments proved that measured electrical resistance of ropes inside the belts could effectively fulfil the fatigue evaluation and lifespan prediction for the belts.