Numerical Simulation and Analytical Solution of Hydraulic Fracturing in Sedimentary Rock Tunnels北大核心CSCD

In the whole process of survey, construction and operation of rock tunnels, hydraulic fracturing is a mechanical mechanism that needs to be focused. In this paper, numerical simulation for fracture damage constitutive model and analytical formula were used to study the hydraulic fracturing of stratified sedimentary rocks. Based on multi-field coupling finite element analysis software, and combining the linear elastic fracture criterion with the damage constitutive model, a seepage-stress-rock damage coupling model is redeveloped, in which micro cracks can be characterized, and applied to study the hydraulic fracturing of rock mass in the saturated seepage process. By introducing dispersed parallel micro cracks for simulating the beddings of sedimentary rocks, the sedimentary rock cylinder model was established to simulate the hydraulic fracturing behaviors under injecting water into apertures and acting of confining pressure, in order to study the fracturing failure modes and seepage distribution patterns. In addition, the quantitative relationship between the critical water pressure for initial cracking and the confining pressure, the pore diameter of specimens was discussed by changing the pore diameter and confining pressure. In order to verify the cracking initiation pressure law obtained by numerical simulation, based on the seepage theory and the basic equation of elastic mechanics, and combined with the tensile failure mode obtained in the simulation, the formula of critical water pressure for cracking initiation in the rock cylinder with uniform linear elastic seepage was derived. The results of analytical solution and numerical calculation show that the cracking initiation pressure obtained by the two methods is in good agreement with the deviation within 3%. The larger the confining pressure, the larger the cracking initiation pressure, with the approximate linear relationship. The smaller the aperture, the larger the cracking initiation pressure, with the approximate negative slope linear relationship in a certain range. At the same time, the cracking initiation pressure by the analytical solution is always slightly greater than that of the numerical solution, which reflects the impact caused by the difference of the basic material hypothesis between the analytical method and the numerical method. When the material property parameters are consistent, the cracking initiation pressure based on the assumption of ideal linear elastomer will be greater than that of the material introduced into the initial damage bedding. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

造船企业压缩空气管网水力计算分析

对某大型造船公司的压缩空气管网进行合理简化,得出可以用于管网水力计算的拓扑图,在此基础上建立各管段的压降方程、节点流量方程和环路能量方程等基本数学方程,最后选择几种基本的调度方案进行模拟计算,并分析和提出降低电能消耗可以采取的措施。     

重卡驾驶室液压翻转机构翻转缸悬置状态仿真分析

针对某重卡驾驶室液压翻转机构出现的泄漏等问题,对其翻转缸在悬置状态进行了基于AMESim的建模与仿真.考虑翻转缸缩回至活塞处于缸筒扩孔区,且活塞杆随驾驶室一起做微幅振动的状态,分析了振动频率、幅值、等效缝隙值对于翻转缸两腔压力的影响,及振动过程中两腔的流量变化.分析结果显示,悬置状态翻转缸会产生缸内负压,造成气穴乃至气...     

ESC液压控制单元设计与选型举例

文章根据整车系统和基础制动系统参数,以及AEB系统对ESC系统理论仿真的TTL要求,逆向计算,校验ESC系统液压控制单元的蓄能器参数、进液阀孔径、出液阀孔径、柱塞泵直径、偏心距、电机功率等,是否可以满足ESC增压能力,蓄能器回油能力等要求,以期达到整车性能表现。     

液驱混合动力车辆控制系统的开发

介绍了液驱混合动力车辆控制系统的开发流程及相关研究。根据制定的开发流程,对控制单元的软硬件进行了设计,并开展了一系列试验,包括控制单元实验室硬件功能调试、物理层控制单元初步调试以及决策层控制单元处理器在环仿真调试。结果表明:所开发的控制系统能够实现目标控制功能,为进一步的实车调试奠定了良好的基础。     

车用液力减速器制动性能试验研究

论述了典型液力减速器的结构及工作原理，并对适用于某车辆的某型液力减速器进行了制动性能试验研究。介绍了试验设备及性能、试验方法。试验结果表明，该液力减速器在高转速和大充油量的条件下制动效果较好。     

Heave-Pitch-Roll Dynamics of Flexible Vehicle in Variable Velocity Run

Analysis for response statistics evaluation of a flexible vehicle travelling with variable velocity over nonhomogeneously profiled flexible track is presented with a heave-pitch-roll model. The vehicle body is idealised as a flexible member with variable cross-section, inertia, damping and stiffness distributions. The vehicle may also have variable section slender elastic attachments. Coupled dynamics with rigid body heave-pitch-roll modes and elastic bending-torsion modes of the vehicle body along with coupled bending-torsion modes of the attachments are considered. Equivalent linear suspension system characteristics are employed for developing the analysis. Numerical results are presented for an aircraft with tricycle landing gear arrangements and comparison is made with other models.     

液压分配阀在全地形车制动系统中的应用

在全地形车制动系统中采用了液压分配阀设计,通过试验及相关验算,该设计简化了制动管路,可方便调整前后轮制动力分配系数,满足全地形车的制动要求,为全地形车制动系统的设计提供了一种新的思路。然而,该设计也存在主泵负担加重、管路压强加大等不利因素,在设计过程中应加以注意和风险防范。     

KZT-150型调速器在丹江电厂的运用

本文详细介绍了KZT-150型调速器以及在丹江口水力发电厂运行过程中优点,给出了DT型调速器和KZT-150型调速器静特性试验结果,对运行过程中存在的不足,给出了解决方案,对KZT-150型调速器的生产和使用具有参考意义。     

基于AMESim-Simulink的船舶液压推进系统仿真研究

为理清油液体积弹性模量、管路长度和补油压力等参数对船舶液压推进系统动态特性的影响,运用AMESim软件建立了液压推进仿真模型,利用Simulink软件建立了螺旋桨负载模型,二者联合进行仿真分析。结果表明,相比于补油压力,油液体积弹性模量和管路长度对航速动态响应影响较大,但三者对航速的最终稳定值影响较小。因此,对于实际的船舶液压推进系统应尽量缩短管路长度,适当提高补油压力,并保证油液冷却良好。