海水对混凝土断裂能及强度的影响

为研究海水对混凝土断裂能及强度的影响,通过三点弯曲试验和稳定的楔形劈裂试验对海水浸泡混凝土、水浸泡混凝土和全干燥混凝土试件进行测试,并利用CONSOFT软件对三组试件的力-变形曲线进行拟合.与水浸泡混凝土的断裂能和强度作了相应对比.试验表明海水使浸泡后的混凝土断裂能减少,其强度也随之降低.从表面能及表面张力的观点分析了断裂能和强度降低的原因.     

风扇传动带盘成形模设计

分析了风扇传动带盘的工艺特性和工序,设计了模具结构,论述了其特点和工作原理.该模具的凹模由固定部分和活动部分组成,浮动凹模镶块和滑块部分由双向斜楔控制、套环定位,保证了横向和纵向压料的精度,满足了零件质量要求.采用浮动定位块使橡胶压缩成形,同时作出件器,简化了模具结构.     

与环境协调的城市地下工程开挖问题分析

伴随着全球经济的发展和城市化进程的加快,地下空间作为一种新资源的开发和利用,已经进入空前发展的时期.但是,地下空间的大规模开发、利用,给人类生存环境造成了一系列的消极影响.随着环保意识的加强,人类逐渐认识到"先污染、破坏,后治理、恢复"的老路已经不再适应当今社会的发展.当今社会是一个注重人类活动与环境和谐的社会.基于此,文章提出了与环境协调的地下开挖,围绕如何使地下开挖对周围环境造成的损害最小,展开了一些探索性的研究,其目的在于使地下开挖与周围环境相协调,确保地下开挖与环境系统达到最优化.     

基于数字散斑相关的封装热机械耦合效应测量

利用数字散斑相关方法(DSCM),对COB封装结构在热循环状态下的表面热机械耦合效应进行了测量.利用CCD摄像机采集封装芯片在不同温度场中的散斑图像,对比采集到的图像,获取封装芯片在温度场作用下的面内变形.根据三角法测量技术原理,将离面位移的测量转化为面内位移的测量,从而获得了芯片受热后的翘曲形变和弹性应变分布.将实验测量与有限元模拟以及理论计算的结果进行了对比,3种结果吻合得比较好,表明了实验方法的有效性和可行性.     

Error compensation for tool-tip trace during cutting of laminated paper for rapid prototyping

Laminated object manufacturing (LOM) is one of the commercialized rapid prototyping (RP) processes, where a focused laser is usually used to cut the cross-section contours of a 3 D part and the grid hatchings of the part-exterior region on a sheet paper stack-wise. Using a laser beam as a cutter can be costly, and the thermal burning of a sheet paper along a laser scanning path can also cause an environment-polluting smoke. This paper presents a paper laminating RP system using a knife as the paper cutter instead of a laser beam. The knife holder is mounted through a radial bearing on the X-Y positioning mechanism in such a way that the knife tip is eccentric to the bearing axis by a small distance (so-called offset). Therefore, the knife tip, which engages into the sheet paper during cutting, tends to follow the path of the XY-driven bearing axis by the error that depends on the path tangential and the eccentricity of the knife tip. A tractrix model is applied to describe the kinetic motion of the knife tip and a method is formulated to compensate for the tracing error of the eccentric knife tip by modifying the original cross-section contours of the part for each layer based on the tractrix equation. A study has also been performed regarding the effect of the knife tip geometry on the cutting notch of the sheet paper and on the roughness of the finished part.     

Formation of micro-grooves under impact loading in elliptical contacts with surface ridges

This paper is focused on the effect of impact loading on micro-deformation of asperities in elliptical elastohydrodynamic contacts. Based upon isothermal Newtonian numerical analyses, it is elucidated that a micro-groove, which appears in the ridge under impact loading in elliptical contacts, is brought about by two different mechanisms. One is the smooth surface local pressure difference across the virtual ridge and the other is the macroscopic pressure difference along the ridge. The formation of the micro-groove due to the former mechanism is influenced by the shape, size and orientation of the ridge, and the smooth surface pressure distribution depending on the initial impact gap and loading speed, and that due to the latter is markedly influenced by the loading speed.     

一款多功能清洁机的创新设计

针对户外广告去除难的问题，设计并介绍了一款清洁机的总体设计思想，分析了清洁机的设计结构，阐明了清洁机的工作原理。针对初步设计的清洁机，展示了其优点与不足，并提出了未来改进的方向。     

气浮+BAF工艺用于污水处理回用的试验研究

采用气浮-BAF工艺对齐齐哈尔污水厂A+A/O工艺二级出水进行深度处理。当气水比为3∶1,回流比为2∶1时,气浮-BAF工艺有很好的有机物去除和脱氮效果;在保证脱氮效果的情况下,投加35 mg/L PAC,出水TP小于0.5 mg/L。结果表明,气浮-BAF工艺出水水质符合回用标准。     

Pullout performance of GFRP anti-floating anchor in weathered soil

Anchors are often used as anti-floating reinforcements in civil engineering structures. However, conventional steel bars present disadvantages concerning corrosion and poor adaptability to aggressive environments. Glass fiber-reinforced polymer (GFRP) components could provide a solution to these problems. In this paper the feasibility of GFRP anti-floating anchors is evaluated. Four full scale pullout tests were performed in moderately decomposed granite (MDG). Bare Fiber Bragg grating (FBG) sensors were embedded into the specimens during the pultrusion process to monitor the stress–strain distribution along their lengths. Based on the results the behavior of the anchors was assessed, including the relationships between the pullout force and the head displacement, the axial strain along anchors and the shear stress at the GFRP-grout interface. The stress distribution of anchors showing interlaminar shear failure was then analyzed based on a maximum shear stress criterion. It was proved that the load transfer mechanism of GFRP and steel anti-floating anchors differs significantly. GFRP anti-floating anchors reach failure due to interlaminar shear failure, while conventional steel anchors generally fail as a result of shear at the grout–soil interface. The test results also showed that the embedded FBG technique is reliable for monitoring the stress–strain state of an anisotropic material.     

基于CPLD技术的PC104总线多功能扩展卡设计

介绍了一款PC104总线多功能扩展卡设计。采用了复杂可编程逻辑器件(CPLD)技术,集成了多路模拟量输入/输出、带光电隔离的开关量输入/输出及一个正交解码电路,接口协议与台湾研华PC工控机ISA总线板卡兼容,满足了嵌入式控制系统高集成度的设计要求,在实际应用中获得了良好的效果。