Thermo-plasticity of high-strength and high-ductility 7050 aluminum ingot

Thermo-plasticity of homogenized 7050 aluminum ingot was investigated by instantaneous tensile tests conducted at different temperatures. The results show that, with the increase of testing temperatures, the strength decreases, and the plasticity increases firstly and then decreases in homogenized 7050 ingot. When the studied alloy is deformed between 380 °C and 420 °C, the deformation resistance is lower and plasticity is better. And the actual heating temperature for ingot before hot extrusion should be controlled between 360 °C and 400 °C. At low tensile temperatures, the deformation structure is mainly composed of dislocation substructure. With the increase of testing temperatures, transgranular fracture transforms into intergranular fracture progressively during deformation. At high tensile temperatures, the grain boundaries are weakened, deformation is concentrated at the grain boundaries and the re-orientation of equilibrium phases at grain boundaries appears.     

Influence of subsequent curing on water sorptivity and pore structure of steam-cured concrete

Steam-cured condition is found to cause larger porosity and worse properties of concrete compared with normal curing condition. For the sake of seeking effective measurements to eliminate this bad effect of steam-cured condition on concrete, the water sorptivity and pore structure of steam-cured concretes exposed to different subsequent curing conditions were investigated after steam-curing treatment. The capillary absorption coefficient and porosity of the corresponding concretes were analyzed, and their mechanisms were also discussed. The results indicate that water sorptivity and pore structure of steam-cured concrete are greatly influenced by the curing condition used in subsequent ages. Exposure steam-cured concrete to air condition has an obviously bad effect on its properties and microstructures. Adopting subsequent curing of immersing steam-cured concrete into about 20 °C water after steam curing period can significantly decrease its capillary absorption coefficient and porosity. Steam-cured concrete with 7 d water curing has minimum capillary absorption coefficient and total porosity. Its water sorptivity is decreased by 23% compared with standard curing concrete and the porosity is 9.6% lower. Moreover, the corresponding gradient of water sorptivity and porosity of steam-cured concrete both decrease, thus microstructure of concrete becomes more homogeneous.     

重载对沥青路面车辙及疲劳寿命的影响

为分析重载条件下沥青路面易产生车辙及疲劳病害的成因,基于弹性层状体系理论,利用ABAQUS有限元软件,分别通过车辙量和剪应力、基层疲劳模型表征路面车辙和疲劳寿命,研究了超重交通荷载对沥青路面车辙及疲劳寿命的影响。结果表明,当基层模量为0.4GPa,轴载从100kN增加到200kN时,压密变形量增加了29.82%,路面内最大剪应力增加了24.7%,基层疲劳寿命缩减了95.30%;而当基层模量为2.0GPa时,上述指标分别为27.67%,39.2%,99.26%。由此可知,重载对沥青路面结构破坏影响显著,且随着基层模量的增加,车辙和疲劳病害更加严重。研究结果有助于解释重交通路段沥青路面车辙及疲劳病害的成因。     

蜀河水电站厂房灌浆排水廊道坝基帷幕加深补强处理

蜀河水电站下闸蓄水后,厂房灌浆排水廊道坝基渗漏水量较大,严重影响大坝安全和水电站的安全稳定运行。针对此情况进行了坝基帷幕加深灌浆补强处理。处理后坝基渗漏水量明显降低,效果十分明显,排水孔排水畅通,扬压力和渗漏水量满足设计要求。     

基于ANSYS的拱坝建模及网格划分

随着拱坝体型的复杂化,拱坝的建模及网格划分的难度也越来越大。以某拱坝为例,通过实体建模,介绍了ANSYS的APDL参数化建立拱坝的方法、过程与特点;采用ANSYS中的Extend(线的延伸)、Extrude(面的拉伸)和Divide(体切割)功能为该模型划分网格,解决了U型拱坝等边划分出的网格比例不当的问题。结果表明:APDL参数化建模的方法方便、快捷、易学习、易交流修改。采用切割等功能划分出的网格形状合理、比例恰当,并且可根据具体要求变更网格的密度,因此能对类似体型复杂、划分要求较高的有限元模型的划分具有很好的借鉴作用,也为此后的拱坝仿真计算打下坚实的基础。     

Self-diagnosis method for faulty modules on wireless sensor node

In order to diagnose the working status of each module on sensor node and make sure the wireless sensor networks (WSN) work properly, the components of sensor node and their working characteristics are studied. An on-line fault self-diagnosis method for sensor node is proposed. First, a flexible fault sensing circuit is designed as a state detection module on sensor node. Second, a self-diagnosis algorithm is proposed based on the hardware design and the failure analysis on sensor node. Finally, in order to ensure the WSN reliability, the voltage changes of each module working statuses can be observed using the state detection module and the faulty module will be found out timely. The experimental results show that this self-diagnosis method is suitable to sensor nodes in WSN.     

钢丝网钢纤维砂浆加固钢筋混凝土梁试验研究

钢丝网钢纤维砂浆加固钢筋混凝土梁在提高构件的承载力、刚度和耐久性方面有明显的效果,且加固成本低,具有良好的工程应用前景.通过一根对比梁和两根加固梁进行了一次受力的四点弯曲试验,试验量测了梁的挠度和钢筋的应变.试验结果表明,钢丝网钢纤维砂浆加固方法能显著提高普通钢筋混凝土梁的开裂荷载,极限荷载的提高则不明显;此外,该方法能有效的抑制裂缝的开展,延缓裂缝形成的时间,提高梁的刚度.     

Hot compressive deformation behavior and constitutive relationship of Al-Zn-Mg-Zr alloy with trace amounts of Sc

Abstract： The hot deformation behaviors of AI-Zn-Mg-Sc-Zr alloy were investigated in a temperature range of 340-500℃ and a strain rate range of 0.001-10 s 1 using uniaxial compression test on Gleeble-1500 thermal simulation machine. The results show that the flow stress increases with increasing strain and tends to be constant after a peak value. The flow stress increases with increasing strain rate and decreases with increasing deformation temperature. The phenomenon of dynamic recovery and dynamic recrystallization can be observed by microstructural evolutions. Based on the hyperbolic Arrhenius-type equation, the true stress-true strain data from the tests were employed to establish the constitutive equation considering the effect of the true strain on material constants （α, β, Q, n and A）, which reveals the dependence of the flow stress on strain, strain rate and deformation temperature. The predicted stress-strain curves are in good agreement with experimental results, which confirms that the developed constitutive equations are suitable to research the hot deformation behaviors of Al-Zn-Mg-Sc-Zr alloy.     

基于搜索引擎优化的《网页设计与制作》课程改革

《网页设计与制作》作为计算机专业的核心专业课程,不但要培养学生的网页设计与制作的方法和技巧,还要依据搜索引擎优化的理念来设计和制作网页,以提高网站或网页在各类搜索引擎中的排名．通过分析《网页设计与制作》课程教学中存在的问题,并根据搜索引擎优化的技术优化该课程内容,采用三阶段递进的教学模式,以培养出符合社会需求的网页设计与制作专业人才．