Effects of sheet thickness and material on the mechanical properties of flat clinched joint

Frontiers of Mechanical Engineering - The flat clinching process is attracting a growing attention in the joining field of lightweight materials because it avoids the geometric protrusion that...     

Solar kiln dryers for timber and agricultural crops

Most of the available equipment for drying agricultural produce is too expensive and complicated for the majority of farmers in the world. The aim of the study was to design cheap and efficient methods of drying timber and agricultural crops with solar energy. The importance of solar kiln dryers for agricultural produce is discussed. Two solar kiln dryers built in the Department of Forest Resources Management, University of Ibadan, Nigeria, are described. One dries' timber and agricultural crops and the other dries only agricultural crops. The results show that the kilns dry the produce with no degradation in quality. Cost-benefit analyses are performed to determine economic feasibility.     

小户型设计研究

本文通过对中国小户型现状及政策背景的归纳分析,得出保障性住房供应结构将从以售为主向租售并举、以租为主转变,小户型将成为主流这一结论。文章在分析国内外小户型案例以及我国现存小户型不足之处的基础上,以国家政策与人的根本需求为指导,探索小户型设计的基本原则及处理手法。在保证结构无大变动的情况下,分别从平面以及空间两个方面进行设计,满足1代至3代人居住的不同需求。对细节设计及组合体设计进行深入研究,最终提出实现产业化、标准化、工业化、单元化的拼接,从根本上降低公租房成本,这一主要结论与观点。     

一种铅锭搬运机器人真空吸附夹具的设计与分析

设计了一种基于真空系统原理的工业机器人真空吸附夹具,用于铅锭搬运,取得了良好的效果。介绍了真空吸附夹具的结构组成。阐述了真空回路和真空发生器的工作原理及技术特点。对真空吸盘、真空发生器和电磁阀等主要组成元器件进行计算和选型,并设计了夹具支架,运用Solidworks软件对夹具支架进行了有限元分析。     

一种新型燕尾槽导轨设计及其调整的方法实现

为了满足飞机垂尾加载试验设备在倾斜悬挂状态下沿导轨平稳运动,采用变形燕尾槽结构设计了一种新型导轨。导轨内设可调斜铸块,易于加工安装和调整间隙,抗震耐磨,具有更好的承受倾斜力及倾覆力矩的能力。该设计利用设备自身的伺服驱动器驱动加载设备移动,根据驱动电流曲线指导导轨的安装调整,使驱动电流峰值减少22%,提高了导轨的装配精度。     

浅谈汽车底盘纵梁冲孔加工设备的应用与前景

对汽车底盘纵梁加工设备进行简要介绍、对比,对市场上新涌现的冲孔工艺设备进行重点介绍,对相关工艺路线进行了简介说明。     

Analysis of internal crack in a six-ton P91 ingot

P91 is a new kind of heat-resistant and high-tensile steel. It can be extruded after ingot casting and can be widely used for different pipes in power plants. However, due to its mushy freezing characteristics, a lack of feeding in the ingot center often generates many defects, such as porosity and crack. A six-ton P91 ingot was cast and sliced, and a representative part of the longitudinal section was inspected in more detail. The morphology of crack-like defects was examined by X-ray high energy industrial CT and reconstructed by 3D software. There are f ive main portions of defects larger than 200 mm~3, four of which are interconnected. These initiated from continuous liquid f ilm, and then were torn apart by excessive tensile stress within the brittle temperature range(BTR). The 3D FEM analysis of thermo-mechanical simulation was carried out to analyze the formation of porosity and internal crack defects. The results of shrinkage porosity and Niyama values revealed that the center of the ingot suffers from inadequate feeding. Several criteria based on thermal and mechanical models were used to evaluate the susceptibility of hot crack formation. The Clyne and Davies' criterion and Katgerman's criterion successfully predicted the high hot crack susceptibility in the ingot center. Six typical locations in the longitudinal section had been chosen for analysis of the stresses and strains evolution during the BTR. Locations in the defects region showed the highest tensile stresses and relative high strain values, while other locations showed either low tensile stresses or low strain values. In conclusion, hot crack develops only when stress and strain exceed a threshold value at the same time during the BTR.     

监控量测在浅埋地下大断面平顶框架结构施工中的应用分析

城市浅埋大断面地下结构因其结构和建设的复杂性往往成为工程建设的重点和难点。施工中如何利用监控量测技术实时监控围岩、支护结构、中间构造结构等之间的受力转换往往成为施工关键。结合北京城市快速轨道交通东直门车站地下方厅工程实例,探讨和分析了应用浅埋平顶群洞暗挖法施工过程中监控量测技术和方法,并对监测结果进行了比较分析,验证了施工方法的合理有效性。     

复合斜面铣削分析

铣削复合斜面 ,若工件受到装夹位置和方向的限制 ,工件或工件和立铣头 ,要转 2个方向的角度或各转 1个角度 ,可利用机床本身的附件进行铣削。若工件的装夹方向不受限制 ,就只需按斜面与基准面之间的夹角θ及斜面与基准面相交线的方向用倾斜一个角度θ来铣削 ,即相当于加工单斜面进行铣削     

LSI低成本制备Cf/SiC复合材料工艺研究

采用一次性液相硅浸渍法(LSI)制备低成本的Cf/C-SiC复合材料。以PAN基平板碳毡为增强体,在酚醛树脂溶液中添加碳化硅微粉,探讨添加碳化硅浓度、浸渍压力及保压时间等因素对一次液相浸渍效果的影响。通过显微分析,当压力为1.2 MPa,浸渍时间为60 min时,可以获得最大的致密度,最终复合材料密度达2.64 g/cm3。