十字轴万向节串联轴系传动特性研究

分析了多个十字轴万向节串联轴系的传动规律,建立串联轴系从动轴转速、角加速度、转矩的动力学模型,得出同步传动的条件,运用Matlab软件编程进行分析十字轴万向节串联轴系从动轴转速、角加速度、转矩的动态特性,分析的结果可用于指导万向节串联轴系的布置设计,并对轴系的减振降噪设计提供参考。     

纵向地震作用下系杆拱桥与引桥间碰撞响应研究

地震作用下,作为主跨的系杆拱桥与连接跨处容易发生碰撞和落梁现象,本文以双自由度简化分析模型为研究对象,考虑梁间伸缩缝处的碰撞。分析结果表明:周期比是影响碰撞力的主要因素,碰撞对伸缩缝两侧结构地震反应的影响与结构周期相关,周期相近的主跨和边跨碰撞力较小,周期比在0.3~0.4时,峰值碰撞力最大,碰撞可以减低柔性墩柱剪力,减小主跨和边跨之间的相对位移,碰撞力一般随伸缩缝间隙增加而减小。     

UHPC 湿接缝浇筑在排水工程中的施工应用控制

预制拼装技术是水务结构施工工艺的重要发展趋势,接缝处理是当前预制拼装技术的关键技术难点。超高性能混凝土（UHPC）具有强度高、韧性大、耐久性好等技术优势,成为解决预制拼装结构接缝连接的有效途径。考虑到该技术在水务工程领域应用相对较少,根据实际工程开展了相关的研究。首先,针对UHPC湿接缝在排水结构的适用性问题、临时支撑的快速周转、高温与低温施工等难点进行了分析研究,通过全尺寸UHPC浇筑工艺试验,对施工参数进行了探索,并提出了高温与低温条件下浇筑策略。研究保证了UHPC湿接缝浇筑施工的顺利进行,有效提高了预制拼装施工效率,提升了湿接缝浇筑质量。     

Inconel 600复合钢板焊接接头结构的改进

焊接复合钢板时,对焊接接头的坡口形式有特殊要求,若坡口形式不当,当先焊接基层时,焊缝金属中可能熔入复层合金元素导致基层焊缝脆化;当先焊接复层时,焊缝金属中可能熔化基层使焊缝金属稀释,降低复层的耐蚀性。采用台阶式坡口形式。使基层和复层的焊接截然分开,避免第一道焊缝金属的互熔,是防止上述问题发生的最好措施。文中对原图样设计的焊接接头坡口形式存在的问题进行了分析,将改进后的台阶式坡口形式应用在设备的焊接上,取得了良好的效果。     

薄板焊接变形高精度预测方法的研究

采用固有应变方法预测焊接变形时,传统方法是把纵向收缩、横向收缩和角变形这三成分作为接头的固有变形来估算焊接变形。但是,由于薄板的刚度低,在纵向方向上的弯曲变形也较明显,采用传统方法会影响薄板焊接变形的预测精度。为提高精度,文章对传统的方法进行了改进,开发了包括考虑纵向弯曲在内的四成分固有变形数值计算方法来预测薄板焊接变形。数值模拟结果表明:运用该方法预测薄板的焊接变形时,比传统的方法有更高的精度,而且预测结果与热弹塑性有限元的模拟结果十分吻合。     

Three Dimensional Numerical Simulation Study on the Tensile Test of the Embedded Components in Segment Joints of Deep Buried Storage and Drainage Shield Tunnels北大核心CSCD

The numerical simulation was carried out based on tensile test of the embedded components in segment joints of the deep buried storage and drainage shield-driven tunnel in Shanghai in order to study the numerical approach for mechanical analysis of segment joints of the tunnel. Using the concrete damage plasticity model and nonlinear springs, the 3D refined numerical model was established, in which the embedded components with complex geometries and the bond-slip behaviors between the concrete and bars were taken into consideration. Three kinds of embedded component models with different degrees of refinement were established and simply loaded. By comparing the calculation results and considering the spent time and the accuracy of calculation, the simplified form of the embedded components used in the overall model was determined. Nonlinear springs between anchor bars and concrete were set in the model in order to simulate the bond-slip behavior between them. In addition, two contrast models were also established using binding constraint and face-face contact constraint between concrete and anchor bars respectively. The three types of models were loaded in accordance with the test conditions. Comparing the results of the numerical calculation with the test results, it is shown that the "nonlinear spring model", which takes the bond-slip behavior into consideration, is more consistent with the test results than the "face to face contact model" and "binding model". And the model also reflects the failure mode very well. It indicates that the three dimensional refined modeling method used in this paper is applicable for similar tensile tests. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

欧美通用小型汽油机排放法规介绍

通用小型汽油机排放法规主要包括分类、测试循环、限值及耐久性要求等方面;美国先行一步,欧洲与美国基本一致。     

通用小型汽油机美国EPA与欧洲排放计算差异分析

分析美国EPA通机排放法规(EPA40CFRPART90)与欧洲关于通用小型汽油机排放的指令(Directive2002-88-EC)中推荐的计算方法之间的差异及其对排放数据的影响。     

盾构管片接头抗弯刚度影响因素研究

研究目的:推导盾构隧道管片接头抗弯刚度计算公式,研究不同影响因素作用下接头抗弯刚度的变化规律.研究结论:管片接头的接触面有效高度和接触面偏心距对管片接头抗弯刚度的影响显著,因此管片结构设计中,通过改变管片接头构造尺寸来调整管片接头刚度是一种有效的手段.     

浅谈公路桥梁伸缩缝施工质量控制措施

桥梁伸缩缝是桥梁上部构造的薄弱部位,直接承受车荷反复冲击作用,从选定产品施工工艺等方面,对伸缩缝施工提出几点技术建议。