施工中遇到的混凝土和砂浆强度评定问题

针对质量检测工作中经常遇到的一些实际问题,如只有一组混凝土和砂浆诫块、同一部位不同养护条件、危险强度、粉煤灰混凝土等特殊情况下,如何评定其强度等问题进行探讨,并以规范标准的原则、理念为基础,结合实际具体情况,提出了相应的处理办法。

不同临壁火源条件下聚苯乙烯的火灾特性

建立了不同临壁火源条件下聚苯乙烯外保温材料壁面火灾的理论模型。通过设计中尺寸实验,得到不同火源尺寸、火源与外墙间距等因素对壁面火灾蔓延速率的影响规律,得到8种工况条件下材料表面燃烧速率较快。依据温度上升速率,提出了"危险强度"的概念,对壁面材料的危险性等级进行了计算和划分。为完善外墙保温施工现场防灭火技术提供指导。

一种基于四关节式结构的机械臂传动结构解决方法

选择基于四关节五自由度的整体机械臂结构,设计一种基于仿人手臂结构及转动结构基础上增加平动传动结构的组合模型。组合中使用传动结构与动力源相结合,无极电机作为动力源,通过减速箱节制速度,并稳定增大扭矩。从材料力学层面计算论证45号钢传动轴在配合使用中的可靠性,阐述设计中各部件配合减速箱形成传动结构,完成传动工作流程回路。重点论证设计冗余缩小计算及进行大臂传动轴的危险断面强度检核。仿真数据在控制范围内,实际模型定制工作效果是稳定实现等比例设计中机械臂对重物的抓取与释放。

Intensity measures for seismic liquefaction hazard evaluation of sloping site

This work investigates the correlation between a large number of widely used ground motion intensity measures(IMs) and the corresponding liquefaction potential of a soil deposit during earthquake loading. In order to accomplish this purpose the seismic responses of 32 sloping liquefiable site models consisting of layered cohesionless soil were subjected to 139 earthquake ground motions. Two sets of ground motions, consisting of 80 ordinary records and 59 pulse-like near-fault records are used in the dynamic analyses. The liquefaction potential of the site is expressed in terms of the the mean pore pressure ratio, the maximum ground settlement, the maximum ground horizontal displacement and the maximum ground horizontal acceleration. For each individual accelerogram, the values of the aforementioned liquefaction potential measures are determined. Then, the correlation between the liquefaction potential measures and the IMs is evaluated. The results reveal that the velocity spectrum intensity(VSI) shows the strongest correlation with the liquefaction potential of sloping site. VSI is also proven to be a sufficient intensity measure with respect to earthquake magnitude and source-to-site distance, and has a good predictability, thus making it a prime candidate for the seismic liquefaction hazard evaluation.

微型客车后驱动桥多轴耦合疲劳试验仿真

汽车行驶时悬架系统承受着来自路面的载荷冲击,保证其耐久性是汽车设计中非常重要且急需解决的关键问题之一,多轴向加载的室内道路模拟疲劳试验被广泛采用。为了进一步缩短汽车研发周期,降低研发成本以提高市场竞争力,该文建立了后驱动桥的动态有限元模型,依照实验室道路模拟疲劳试验的基本原理,通过编制MATLAB程序实现了系统频响函数识别、根据目标信号和频响函数反求动态载荷、计算动态响应与目标信号的误差等功能。仿真结果表明：后驱动桥目标信号测点的应力应变时间历程复现综合误差均在5%以内,并预测出该悬架系统的疲劳强度危险点位于截面尺寸突变的区域。