Changes in epoxy-coated aluminium due to exposure to water

An investigation was performed of the changes that occur in a typical epoxy-coated aluminium system due to exposure to water. The adhesion of the epoxy coating upon exposure to water was evaluated for different exposure temperatures and periods. The adhesion test results showed an initial loss of adhesion of the coating but after this the adhesion improved again and even significantly exceeded adhesion prior to exposure. The amount of adhesion improvement and the speed with which adhesion improvement occurred was found to be larger for higher exposure temperatures. The changes that occur in the epoxy-coated aluminium system due to exposure to water were investigated using a number of different analytical techniques. Based on this, a model was proposed for the processes that take place during exposure and which can explain the adhesion test results. First, the adhesion of the epoxy coating is lost upon exposure due to the accumulation of a significant amount of water at the interface. The water at the interface causes formation and growth of a thin oxyhydroxide layer underneath the epoxy coating. After some time, this oxyhydroxide layer re-establishes contact with the epoxy coating and forms a new, water-stable bond, hence explaining the improvement of the adhesion after its initial loss.

The temperature-dependence observed in the adhesion test results is explained by the fact that at a higher exposure temperature, more water accumulates at the interface, the oxyhydroxide layer grows faster and also attains a larger limiting thickness.     

Holographic Deformation Measurement by a Spatial Carrier Fringe Technique

A carrier fringe techrtique for measuring surface deformation is described and verified by experiments. In contrast to conventional holography and fringe analysis, this holographic system is based on fibre optics and automatic spatial carrier fringe pattem analysis techniques Single-mode optic fibres are used to transfer both the object and reference beams. Carrier fringes are generated by simply translating the object beam between two exposures The Fourier transform is applied to the carrier fringe pattern to convert it to the spatial frequency domain, where it is processed The results are given for a centrally loaded disk, including a 3-D perspective plot of the out of plane deformation field, phase map, grey level map and contour map.     

硫化机硫化外胎露线原因剖析和改进措施

叙述硫化外胎胎冠花纹沟露线、胎冠中心线露线、胎肩露线、胎圈露线以及胎里露线等问题的特征和弊端，提出结构设计、生产工艺和设备条件各方面的预防和改进措施：同一规格、不同花纹的轮胎要用不同的胎面挤出口型，胎肩曲线、内衬层厚度等设计要合理；压延、挤出、成型和定型、硫化各工序要严格执行工艺规程；要经常检查硫化设备运行状况，对磨损和老化部件及时更换。     

UV固化胶辐射能量与固化深度的关系

不同的紫外光固化胶,在同种类型的UV灯照射下,其固化性能有所差异。采用临界曝光量和透射深度2个特性参数来表征光固胶的光敏性,探讨临界曝光量和透射深度之间的数学关系,并研究临界曝光量和透射深度的测定方法,从而指导UV胶的配方设计。     

Experimental and numerical study on compressive performance of perforated brick masonry after fire exposure

This paper discusses the compressive performance of perforated brick masonry after fire exposure. Compressive strength tests of the mortar, clay perforated brick, and perforated brick masonry specimens were performed in accordance with ISO834 fire tests of different durations. The temperature distribution of the masonry materials and specimens was simulated using the finite element software ABAQUS, with the thermal parameters of masonry materials recommended by European standard Eurocode 6 and related literature. The compressive strength reduction factors of mortar and clay perforated brick exposed to different fire durations were calculated via the layered method suggested by European standard Eurocode 1. In addition, the compressive strength reduction factors after cooldown were obtained from the experimental data of the masonry materials, and by considering further reductions in the compressive strength after cooling from high temperatures. Experimental data of the masonry specimens were compared with the numerical results obtained using the reduction factors proposed in this work. The comparison revealed an overall acceptable approximation. Thus, the method presented in this paper can be used to evaluate the residual capacity of masonry structures after fire.     

射流卷吸边界层内相干结构的实验研究

在轴对称水射流实验台上,采用单帧长曝光图像法,测量了出口Reynolds数在1849~2509范围内的卷吸边界层内流场结构。发现在流向距离L=2D~3.5D,径向距离H=D~1.25D的区域内,流场中吞噬作用和侵蚀作用两种卷吸模式交替出现。分析得到,当Re>1915时,吞噬作用所占的比例随着Re的增大而增大,当Re>2311之后,Reynolds数对该结构发生概率的影响降低;通过快速傅里叶变换得到该相干结构发生的频率在10～19Hz之间;吞噬作用发生的同时在流场中观测到一些特殊涡结构。同时采用运动单帧长曝光图像法对射流流场进行拉格朗日法观测,发现射流流场中的涡结构一般存在于湍流与非湍流界面附近。     

MATLAB环境下的对数螺旋锥齿轮啮合接触分析

根据齿轮啮合原理,通过一种求解齿面瞬时接触区域的数值算法,推导出对数螺旋锥齿轮的齿面接触区域方程,再结合对数螺旋锥齿轮的三维模型,利用MATLAB软件对其进行仿真分析,得到了对数螺旋锥齿轮啮合接触区的变化规律,实现了接触区域的可视化仿真。最后,以一对对数螺旋锥齿轮样轮的齿面接触试验为例,将试验结果与仿真分析结果进行对比,验证了接触区域仿真结果的正确性,为后续对数螺旋锥齿轮齿面进行TCA分析奠定了理论基础。     

贫铀合金的大气腐蚀特性研究

通过对贫铀合金在沿海、内地的户外暴露试验和库内露置试验，研究并得到了贫铀合金的大气腐蚀特性，分析了大气中SO2、Cl-及相对湿度腐蚀贫铀合金的原因与结果.      

ͭ��ǥ����ͷ����ʴ��Ϊ�о�

 含Zn-Sn钎料的铜铝过渡线夹在服役过程中易发生腐蚀失效。应用扫描电镜、能谱和XRD系统分析了不同工艺制备的钎焊接头在盐雾暴露环境下的腐蚀行为,并以拉剪试验评价其残余抗剪强度,初步揭示了腐蚀发生的规律及其对抗剪强度的影响。研究表明,在盐雾环境下钎料层首先被腐蚀,其次铝基体被腐蚀,而铜的腐蚀较少。盐雾暴露环境下接头的残余抗剪强度腐蚀时间延长逐渐降低。总体而言,线夹整体耐腐蚀性能的高低主要取决于钎料耐腐蚀性能,而工艺参数对腐蚀行为的影响不大。钎焊电流为12 A、时间为10 s的工艺制备的接头经腐蚀试验残余强度最高。     

GH3230合金焊接板材长期热暴露后组织和性能研究

研究了GH3230合金焊接板材在经过不同温度(700～1000℃)、不同时间(1000～2000 h)的长期热暴露处理后显微组织和力学性能的变化。结果表明：热暴露处理后熔化区铸态组织的枝晶成分偏析程度显著降低,并且随着热暴露温度的升高,降低效果更明显,逐渐形成晶粒组织。在800℃以上长期热暴露后,室温抗拉强度和屈服强度有所降低,延伸率逐渐上升,主要是由于热影响区小颗粒状(CrW)₂₃C₆碳化物回溶和W₆C碳化物粗化导致的。随热暴露温度升高,高温持久断裂时间明显降低,而持久塑性有所升高,母材晶粒尺寸较小和碳化物粗化是焊接板材断裂在母材处的原因。