软弱地基适用的一种处理方法

本文根据某机场软弱海相沉积淤泥地基采用堆载预压法的处理情况,对该类地基堆载预压处理的有关情况进行了推介,供类似工程参考。     

浅谈尺寸工程在汽车开发中的应用

随着我国近几年汽车产业的蓬勃发展,车企之间的竞争日益激烈,汽车在外观上满足不同顾客的需求,来提高市场的竞争力和市场的覆盖率,如何降低成本、提高产品质量和缩短开发周期已成为各车企的生存和发展的关键,尺寸工程也逐渐被各大车企接受并开展。文章主要简单描述尺寸工程在汽车开发过程中各节点的设计和应用。     

Numerical simulation of fluid flow caused by buoyancy forces during vacuum arc remelting process

The metallurgical structure and composition of ingots which depend critically on the fluid motion within the molten pool during the vacuum arc remelting (VAR) process have important effect on the subsequent mechanical processes like forging, rolling and welding. In order to determine the fluid motion of molten pool, a 2D finite element model is established using ANSYS10.0 software, combined with the turbulent fluid flow and heat transfer. The fluid motion caused by thermo buoyancy forces is investigated at different VAR processes in the present study. The results indicate that the fluid flows symmetrically along the axis of the molten pool and clockwisely along the circle at the right pool’s profile. It is also shown that the maximum velocity increases with increasing melting rate and a direct proportional relationship exists.     

《北京城区行人和非机动车交通系统设计导则》编制思路与技术要点

为改善行人和非机动车交通环境、促使城市交通模式由“车本位”向“人本位”转变,北京市自2006年开展了相关研究工作,并于2010年6月发布了《北京城区行人和非机动车交通系统设计导则》(以下简称《导则》).以上述工作为基础,介绍了《导则》编制的总体思路,分析行人和非机动车交通系统的基本要求及设计体系构成.结合北京市相关调查...     

基于IC卡数据的轨道公交接驳特征分析

针对当前轨道接驳研究侧重人工调查或理论分析、利用大数据进行公交接驳准确分析的研究相对较少问题,提出以IC卡数据为数据源的轨道公交接驳比例、接驳距离等相关指标的计算模型,并利用该模型计算北京市现状轨道站点的公交接驳相关指标.基于轨道站点设计阶段所能获取的站点属性信息将北京市轨道站点分为末端站、市区普通站、市区换乘站、郊区普通站、郊区换乘站5类,在该分类结果基础上对北京市轨道公交接驳特征进行分析.基于IC卡数据对轨道公交接驳特征进行准确分析,可为轨道站点的外部接驳设计、接驳公交布设、提高轨道交通服务水平等补充相关数据资料.     

Asymmetric deformation of near hemispherical diaphragm under uniform surface load

The asymmetric deformation and eccentricity problems of near hemispherical diaphragm under the uniform surface load are quantitatively characterized in the paper. The analysis is based on a 3D finite element analysis (FEA) model established according to elastic-plasticity and large displacement nonlinear finite element method. Besides, the deformation experiments are taken to validate the reliability of FEA model which shows that the simulation results are in good agreement with the experimental results. Then, three angle parameters, deflection angle β, circumvolving angle θ and distributing angle γ, are introduced and expressed to characterize the asymmetric deformation and eccentricity quantitatively. According to the angle parameters, the inversion processes of uniform thickness diaphragm and varying thickness diaphragm are calculated respectively. The inversion process of varying thickness diaphragm is much steadier than that of uniform thickness diaphragm. The present results show that the asymmetric deformation process can be characterized by curve of three angle parameters (β, θ, γ) exactly, the degrees of eccentricity can be indicated by the final value of deflection angle and the eccentricity position can be characterized by the final values of the three angle parameters.     

Effect of remelting current on molten pool profile of titanium alloy ingot during vacuum arc remelting process

The performance of vacuum arc remelting (VAR) ingot depends largely on ingot structure and chemical uniformity, which are strongly influenced by molten pool profile that is influenced by VAR process. To better understand the effect of remelting current on molten pool profile of titanium alloy ingot during VAR process, a 3D finite element model is developed by the ANSYS software. The results show that there are three remelting stages during VAR process when the remelting current is 2.0 kA. The molten pool depth increases gradually from 30 to 320 s, then the change of molten pool depth is very small during the steady state stage from 320 to 386 s, and lastly the molten pool depth becomes shallow after 386 s. The melting rate and temperature of superheat increase with the remelting current increasing, which leads to the augment of molten pool volume. In the end, the total remelting time and steady state molten pool time decrease with the melting current from 1.6 to 2.8 kA.     

Numerical analysis of material properties in deformation of near hemispherical shells

In this paper, the effects of hardening exponent, yield strength and elastic modulus on the deformability of near hemispherical shells are investigated by means of finite element method and orthogonal experiment design. The largest eccentric angle during the deformation process and thickness reduction after the deformation are introduced to estimate the deformability quantitatively according to the deformation characteristics of near hemispherical shells. The results indicate that the hardening exponent is the most influential parameter, followed by elastic modulus and yield strength. The shell exhibits good deformability when the hardening exponent and elastic modulus are in the range of 0.1–0.125 and 70–108 GPa, respectively.     

引入“低碳”的道路交通工程仿真应用体系研究

该文从道路交通工程需求和交通仿真功能出发,研究常规仿真评价指标的同时引入"低碳"评价指标,建立交通仿真应用体系,为规范交通仿真的应用和建立交通仿真评价体系提供基础研究。该项研究分为三个层次,首先对工程中常用的交通仿真功能进行分类整理并引入交通环境评价功能,且提出关键应用指标;其次分析各类工程对交通仿真的需求特点并对工程类型进行梳理;最后建立涵盖"低碳"的交通仿真应用体系,作为建立交通仿真平台的基础研究。     

仿真求解城市快速路交织区合理长度

城市快速路交织区长度的合理设置对于提高交织区的通行能力和服务水平,减少对快速路非交织段交通流的影响具有重要意义。对菱形立交先入后出式出入口进行数据收集,利用该数据标定和验证VISSIM微观仿真模型,建立城市快速路交织区仿真模型。通过仿真试验结果分析,得出城市快速路先入后出式出入口交织区长度建议值。