全液压推土机行驶静压驱动系统参数设计与校核

全液压推土机行驶静压驱动系统参数的选择与匹配决定了其液压系统及整机性能的发挥，对全液压推土机行驶静压驱动系统的关键参数进行了设计和计算分析，并对一些关键参数进行了校核。     

串联式混合动力汽车APU优化控制方法

对于串联式混合动力汽车,功率跟随控制策略虽然可以显著提高燃油经济性,但也因此加剧了APU动态变化,这样,在整车控制策略中必须对APU的动态行为进行优化。本文以APU的动态响应为目标,基于J1939协议,对发动机采用CAN总线直接控制,提高了发动机的动态响应速度。     

汽车前轴机加新工艺

汽车前轴系长杆类对称零件(如图1),在其冷加工过程中,要解决的关键问题集中在两主销孔与锁销孔的加工上.首先,要保证两主销孔上下端面对主销孔轴线的垂直度达到0.05 mm;其次,要保证主销孔与锁销孔两十字孔相贯的位置尺寸公差达到±0.1 mm.     

土体宽度非对称基坑变形特性分析

采用MIDAS/GTS有限元软件对邻近有地铁车站形成的两侧土体宽度非对称的基坑开挖进行数值模拟,详细分析一侧为半无限土体,另一侧土体宽度由有限土体逐渐变为半无限土体的基坑变形特性,并与现场监测数据进行对比分析。结果表明:在厦门地区地层条件下,基坑有限土体侧的变形明显小于半无限土体侧,基坑有限土体侧土体宽度对基坑变形的影响范围为1.5倍左右基坑开挖深度。具体表现为随着基坑有限土体侧土体宽度的增大,基坑坑底隆起值增大,基坑半无限土体侧地表沉降量、桩体水平位移量减小,基坑有限土体侧地表沉降量、桩体水平位移量增大,基坑两侧变形逐渐变化至基坑两侧均为半无限土体时的变形量。     

Wall Thinning Characteristics of Ti-3Al-2.5V Tube in Numerical Control Bending Process

A finite element(FE) model for the numerical control(NC) bending of Ti-3 Al-2.5 V titanium alloy seamless tube is established, considering the variation in the contractile strain ratio(CSR) and elastic modulus(E). The wall thinning characteristics of Ti-3 Al-2.5 V tube under different geometric and process conditions were investigated. The results showed that the CSR-E variation can change the wall thickness, but has no remarkable effect on the change characteristics. The reasonable parameter ranges are as follows: a bending-radius range not less than 1.5 times the outer diameter, a bend angle up to 180?, and a mandrel extension of 0-3 mm. The friction coefficient between the pressure die and the tube should be in the range of 0.20-0.35, and between the bending die and the tube should be in the range of 0.05-0.15. As long as the performance meets the requirements, the relative push-assistant speed should be as small as possible.     

Numerical evaluation method of lightning rod protection probability北大核心CSCD

［Objectives］Aiming at the current situation in which it is difficult to efficiently evaluate protection probability through traditional lightning rod evaluation methods, an efficient numerical evaluation algorithm is developed on the basis of an electrogeometric model (EGM) and attractive volume to realize the efficient calculation of lightning protection probability at any point in space.［Methods］This method first determines the attractive volume boundary of the lightning rod and protection object according to the interception process of the upward and downward leaders. The collection surface and exposure arc of the lightning stroke distance are then calculated, enabling the attractive risk and interception effect of the lightning rod to be quantified. Finally, the attraction and interception characteristics of the lightning rod are integrated to establish a numerical evaluation model of protection probability. To verify the accuracy of this method, the general rule of lightning rod protection probability is analyzed and the results compared with the existing analysis method.［Result］The evaluation results of this method show good agreement with those of classical leader progression model (LPM) theory.［Conclusions］ The method proposed herein has a high degree of quantification and can realize the efficient calculation of lightning protection probability at any point in space, which can provide useful references for lightning protection design work. © 2023 Authors. All rights reserved.