Enhanced Strength and Corrosion Resistance of Mg–2Zn–0.6Zr Alloy with Extrusion

The microstructure, mechanical properties and corrosion behavior of Mg–2 Zn–0.6 Zr alloy under the as-cast and asextruded conditions were investigated. Microstructure analysis indicated the remarkable grain refinement by extrusion, as well as notable reductions in volume fraction and size of precipitate phases. As compared with the as-cast alloy, the asextruded alloy exhibited better mechanical performance, especially in yield strength which was promoted from 51 to 194 MPa. Refined grains, dispersive precipitate phases and texture were thought to be the main factors affecting the improved performance in strength. The electrochemical measurement and immersion test revealed the corrosion rate of Mg–2 Zn–0.6 Zr alloy by extrusion decreased from 1.68 to 0.32 mm/year. The reasons for the enhanced corrosion resistance were mainly attributed to the decreased volume fraction and Volta potential of the precipitate phases, the refinement of the grain size, as well as the formation of more protective corrosion film.     

Assessment of vitrified CBN wheels for precision grinding

Methods of measuring topographical features of grinding wheels are reviewed. Each technique has advantages and limitations for resolution, measuring depth, ease of application, data analysis and interpretation. Results obtained vary according to the method and instrument employed. Advantages and difficulties experienced with different techniques are discussed. Different replication techniques and materials are compared and suggestions made. A set of parameters that describe the wheel and grain characteristics is defined. Experimental studies with grinding wheels having different structures are carried out in terms of observations and measurements of changes in wheel topography. Experimental results are analysed and discussed in relation to theoretical understanding of abrasive wear and loading.     

基于无人机的建筑立面裂缝检测

为准确、全面检测建筑立面裂缝,提出一种基于无人机近景摄影测量和计算机视觉的裂缝检测方法。首先根据建筑立面高度和结构特点,结合无人机自动航线飞行和手动贴近飞行进行影像数据采集,并基于此构建针对建筑裂缝的影像数据集。其次,借助基于深度残差神经网络的识别方法对建筑立面进行识别以提取出墙面上的裂缝区域。进一步地,构建基于坐标转换的无人机影像像素解析度计算方法,建立数字图像处理驱动的裂缝几何信息提取方法。最后,以上海市同济大学四平路校区内中德楼为例进行裂缝检测实验,实验结果表明利用本文方法可对高层建筑立面进行影像采集,重建后影像精度达到亚毫米级(0.5mm/pixel),并能在此基础上准确地进行建筑立面裂缝检测(精确率99%),同时可以合理判断裂缝的长度,检测成果可以反映裂缝在墙面上的分布和走向,为后续建筑立面裂缝病害类型的判断提供支撑,具有良好的应用价值。     

地下室深基坑降水井封堵技术研究

地下工程施工过程中,为了减少地下水位过高给施工带来的不利影响,通常需在基础底板中设置降水井,将地下水位降至设计水位,确保基坑的稳定性.如果降水井口的封堵方式不当,容易造成地下室底板渗漏水,还会影响地下室的使用功能,增加后期维护费用.本项目根据现场实际情况,采用了一种用于地下室底板降水井的封堵装置,通过封堵装置的设计与安...     

浙江财富金融中心

本文介绍了浙江财富金融中心项目概况,并从设计意向、整体构思、形体、功能等方面,概括阐述了约翰·波特曼的设计思想。     

旋挖钻机设备油液智能分析与健康监测

为了对直升机盒段件入水载荷进行分析,开展了模型垂直入水冲击试验,同时采用有限元-光滑粒子流体动力学（finite element method-smooth particle hydrodynamics,简称FEM-SPH）耦合数值方法进行仿真分析,计算了不同材料构型和速度下的过载、压力及应变结果。与试验结果进行对比表明,仿真结果与试验值吻合较好,预测的结构失效破坏模式与试验结果基本一致,可为真实直升机入水冲击的结构设计提供参考。     

Numerical simulation of friction stir-assisted incremental forming with synchronous bonding of heterogeneous sheet metals

Friction stir-assisted incremental sheet forming with synchronous bonding is developed as a novel variant of incremental sheet forming, by which the two sh     

薄壁弱刚性钛合金结构件制造工艺

随着新型材料冶金技术的发展与进步,钛合金作为“崛起的第三代金属”已完全替代了铝镁合金和钢构件,成为航天飞行器上应用范围最广的材料之一。从某新研制航天飞行器外部结构件用钛合金材料的特性及切削特点入手,针对薄壁弱刚性钛合金结构件在实际加工过程中遇到的诸多难点,提出了相应的解决办法,并重新设计了零件工装。结果表明,改进措施不仅保证了零件质量,而且提高了零件加工效率,使单件零件的生产周期缩短了近10h。     

新型聚合物改性水泥砂浆材料研究

为解决沙漠化和边坡失稳带来的环境问题和经济损失,研究了高水灰比、低聚灰比的新型聚合物水泥砂浆。实验结果表明,聚氨酯和聚丙烯酸钠各以水泥质量的5%复配掺入到水泥砂浆中后,抗压强度平均提高约15%,抗折强度提高约20%,水泥基材料的韧性明显增强,吸水保水功能强。现场应用效果明显。     

加气混凝土砌块生产中应注意的问题

1概述．建材工业“十一五”规划提出了新型墙体材料的比例达到40％的要求，即新型墙体材料总产量为3000亿块（折标准砖），而实心黏土砖的总量由2000年的5400亿块。控制在4500亿块以内，所压缩的9．00亿块黏土实心砖被近14亿m^3，的新型墙体材料所代替。