Poroelastodynamic responses and elastic moduli of a transversely isotropic porous cylinder under forced deformation test

Existing transversely isotropic poroelastodynamics solutions are limited to infinite domains and without experimental validation. Furthermore, there is a lack of analytical simulations for the elastic moduli dispersion of fluid-saturated porous cylinders. To address these three limitations and investigate the mechanisms of moduli dispersion, we present the analytical solutions of the poromechanical responses and the elastic moduli dispersion of a transversely isotropic, fluid-saturated, finite porous cylinder subjected to a forced deformation test. Through an example, we demonstrate the effects of loading frequency, boundary conditions, and material's anisotropy, dimension, and permeability on the responses of pore pressure,force, displacement, and dynamic elastic moduli of the cylinder. The specimen's responses are significantly influenced by the frequency of the applied load, resulting in a drained state at low frequencies and an undrained state at high frequencies. At high frequencies, the sample behaves identically for an open or a closed lateral boundary, and permeability has insignificant effects. The dynamic elastic moduli are mainly controlled by the loading frequency and the ratio of the sample's radius to its height. Lastly,we show excellent matches between the newly derived analytical solution and laboratory measurements on one clay and two shale samples from Mont Terri.

Dynamic responses of a multilayer piezoelectric hollow cylinder under electric potential excitation

The dynamic responses of a multilayer piezoelectric infinite hollow cylinder under electric potential excitation were obtained. The method of superposition was used to divide the solution into two parts, the part satisfying the mechanical boundary conditions and continuity conditions was first obtained by solving a system of linear equations; the other part was obtained by the separation of variables method. The present method is suitable for a multilayer piezoelectric infinite hollow cylinder consisting of arbitrary layers and subjected to arbitrary axisymmetric electric excitation. Dynamic responses of stress and electric potential are finally presented and analyzed.

Dynamics of the Moving Ring Load Acting in the System“Hollow Cylinder+Surrounding Medium”with Inhomogeneous Initial Stresses

This paper studies the influence of the inhomogeneous initial stress state in the system consisting of a hollow cylinder and surrounding elastic medium on the dynamics of the moving ring load acting in the interior of the cylinder.It is assumed that in the initial state the system is compressed by uniformly distributed normal forces acting at infinity in the radial inward direction and as a result of this compression the inhomogeneous initial stresses appear in the system.After appearance of the initial stresses,the interior of the hollow cylinder is loaded by the moving ring load and so it is required to study the influence of the indicated inhomogeneous initial stresses on the dynamics of this moving load.This influence is studied with utilizing the so-called threedimensional linearized theory of elastic waves in elastic bodies with initial stresses.For solution of the corresponding mathematical problems,the discrete-analytical solution method is employed and the approximate analytical solution of these equations is achieved.Numerical results obtained within this method and related to the influence of the inhomogeneous initial stresses on the critical velocity of the moving load and on the response of the interface stresses to this load are presented and discussed.In particular,it is established that the initial inhomogeneous initial stresses appearing as a result of the action of the aforementioned compressional forces cause to increase the values of the critical velocity of the moving load.

Quantitative analysis of deformation in hollow cylinder tests on anisotropic clay formations

A series of triaxial laboratory experiments are performed on thick-walled hollow cylindrical samples of boom clay.The aim of this testing program is to better understand the anisotropic deformation during the excavation.The testing conditions are similar to those to be experienced by host rocks around disposal galleries for radioactive waste.X-ray computed tomography is performed at different steps for each test with the samples remaining inside the loading cell.Initial analysis of the tomography images allows of the observation of the deformation of the central hole.In addition,particles manual tracking and 3D volumetric digital image correlation processing methods are considered being used to analyze the particles displacements and the boundary deformation of the sample quantitatively.An unsymmetrical damaged zone is induced around the hole,with a reverse deformation trend being found at the boundary after unloading,which indicates that the significant anisotropic deformation of boom clay can be induced by mechanical unloading.

TRANSIENT THERMAL STRESSES IN AN ORTHOTROPIC HOLLOW CYLINDER FOR AXISYMMETRIC PROBLEMS

For the thermoelastic dynamic axisymmetric problem of a finite orthotropic hollow cylinder,one comes closer to reality to involve the effect of axial strain than to consider the plane strain case only.However,additional mathematical difficulties should be encountered and a different solution procedure should be developed.By the separation of variables,the thermoelastic axisymmetric dynamic problem of an orthotropic hollow cylinder taking account of the axial strain is transformed to a Volterra integral equation of the second kind for a function of time,which can be solved efficiently and quickly by the interpolation method.The solutions of displacements and stresses are obtained. It is noted that the present method is suitable for an orthotropic hollow cylinder with an arbitrary thickness subjected to arbitrary axisymmetric thermal loads.Numerical comparison is made to show the effect of the axial strain on the displacements and stresses.

机械反馈式伺服阀流量测试动态缸参数选用分析

相比电反馈伺服阀动态特性可直接通过阀芯位移响应测试获得,机械反馈式流量伺服阀的动态特性,通常需利用动态缸作为流量传感器间接测量获得。测试结果受动态缸泄漏、阻尼、质量惯性等固有非理想化因素的影响,通常无法准确表达伺服阀本身的性能指标。基于一套实际阀控缸系统,建立Matlab-Simulink仿真模型,解析获得的频带宽结果相比实测结果误差小于0.5%,由此建立了可准确表达阀与缸性能特性的仿真模型。在此基础上,理论给出了伺服阀本身的频率特性指标,即无泄漏无阻尼及无限刚度动态缸条件下的系统频率特性。以此为依据,分析了实际动态缸活塞质量、活塞粘性阻尼以及泄漏变化情况下,阀控缸系统频率特性偏离理想条件的变化规律。

空腹混凝土坝振动响应试验研究

针对平原地区土层条件较差和地形条件有限的情况,提出一种新型坝——空腹混凝土坝。采用振动台模型试验技术,研究加速度峰值、库水位及防渗墙对该新型坝动力响应的影响。结果表明:(1)在自由场坝基中设置结构可以降低坝基的超孔压响应,削减坝基液化程度。(2)非自由场工况中,加速度峰值的增大加强了坝基的振动幅度,加剧液化程度;坝体上游库水位的存在增加了坝基的有效应力从而降低液化程度;坝基中防渗墙的存在增加了孔压的消散从而降低液化程度。总体来说,加速度峰值对液化程度影响最大,库水位影响次之,防渗墙影响最小。(3)库水位的存在增加了坝体的受力程度导致坝体水平位移响应大于空库工况,防渗墙的存在降低了坝基中的水力梯度导致坝体响应低于无防渗墙工况。但在试验过程中坝体并没出现明显的水平位移变化。

柴油机活塞环润滑油膜厚度超声波测量方法研究

活塞组件-缸套摩擦副位置处良好润滑状态能够保障柴油机的稳定运行,润滑油膜厚度能够对其润滑状态进行判断。因此本文以润滑油膜厚度为测量目标,基于等效弹簧模型超声波测量原理对活塞环位置处润滑油膜厚度开展实验研究。搭建了润滑油膜厚度超声测量实验平台,通过实验证实了超声方法的测量能力。构建了柴油机活塞环润滑油膜厚度测量方案,设计并搭建了活塞环润滑油膜厚度动态测量系统,对不同转速下的润滑油膜厚度进行了实验测量。通过对实验数据进行处理,在活塞环处测得了2.2~3.9μm的润滑油膜厚度,并且随转速增加,油膜厚度呈现增大趋势,证实了该方法的可行性。

冶金高频响高精度伺服液压缸性能测试系统软件开发

采用LabVIEW与MATLAB函数结合的方法,开发了冶金高频响高精度伺服液压缸性能测试系统。根据生产冶金高频响高精度伺服液压缸对其动静态性能指标要求,该测试系统功能模块包含最低起动压力测试模块、带载动摩擦力测试模块、阶跃响应测试模块、频率响应测试模块、偏摆测试模块,各项测试结果通过研华数据采集卡PCI-1742U、PCI-1723与SSI-RS485电流变送器转换采集MST位移传感器信号与AB相脉冲传感器信号;该测试系统能够对测试的数据进行实时跟踪显示、存储或查询;此外,该系统还具有数据导出、打印实验报告等辅助功能。实验证明,该测试系统具有较高的实时性与可操作性,填补了其他系统所空缺的针对于大直径冶金高频响高精度伺服液压缸的偏摆测试模块,同时该测试系统具有更高的稳定性,解决了技术人员对原有测试系统操作复杂的难题,实现“傻瓜式”操作,更加智能化、可视化、及时化。

HGC液压缸测试平台设计

详细介绍某HGC液压缸测试平台的结构,以及HGC液压缸出厂前的测试方法,实例介绍测试内容。

气缸套部件机械疲劳试验方法研究

本文提供了一种具有通用性的气缸套部件机械疲劳试验设计思路和方法,该方法能够同时考虑气体爆发压力和活塞侧向力对气缸套疲劳寿命的影响。以某型发动机为研究对象,首先基于曲柄连杆机构动力学、运动学计算,获取原发动机工作状态下最大气体作用力和最大侧向力对应的曲轴转角时刻及其相对应的活塞位移,以此作为气缸套部件机械疲劳试验时的载荷和位移约束边界。其次,根据上述载荷和位移约束边界设计了部件疲劳试验中的关键结构参数。最终,通过试验对侧向力进行了标定,证明了侧向力加载的正确性。在此基础上完成了1000万次加载的气缸套部件疲劳试验考核,经渗透探伤检查,气缸套无裂纹,表明其满足可靠性设计要求。

透析器溶血试验方法改进研究

目的对当前的溶血试验方法进行优化,使其可甄别有不良事件发生的透析器。方法从两方面优化现有的溶血试验方法,一方面将中空纤维与红细胞悬液的静态接触时间从60min增加到100min,另一方面增加静态接触后将中空纤维在红细胞悬液中滑动20次的动态接触。用改进后的方法对2种有不良事件发生过的透析器及另外3种透析器进行溶血试验。结果2种有不良事件发生透析器的溶血率远大于其余3种透析器,改进后的溶血试验方法可甄别出2种不良事件透析器。结论优化后的溶血试验方法对高危透析器有一定的甄别作用。

6 500 kN液压冲击试验机刚性冲击特性分析

针对6500 kN大吨位液压冲击试验机在刚性冲击过程的安全性问题,基于撞击动力学建立了冲击油缸液压油与活塞杆中应力波波动方程,采用Ls-dyna显示动力学分析模块,对冲击油缸刚性冲击过程进行数值模拟。研究结果表明:刚性冲击过程中,施加载荷产生的应力波传递到结构边界位置会发生叠加,导致载荷激增;两次载荷突变位置分别对应冲击油缸液压油与活塞杆刚性边界位置,数值计算结果与理论分析相符合;根据分析结果可知,超大吨位液压冲击试验机应采用防刚性冲击保护装置进行保护,防止出现刚性冲击载荷过大造成自损问题。研究结论可为设计液压冲击试验机极限承载能力提供理论依据。

极低速伺服油缸摩擦力与磨损

基于黏着理论对油缸活塞密封件的工作过程进行瞬态动力学仿真。结果表明:摩擦力和运行速度与介质压力正相关,介质压力和运行速度对磨损影响较小,油缸磨损主要取决于位移。研制液压测试系统,测试伺服油缸在极低速下运行的摩擦力。结果表明:摩擦力与介质压力正相关,与速度负相关。

轧机AGC液压缸智能检测系统平台研发

针对轧机AGC液压缸静动态特性性能指标测试技术第三方验证的重要性,开发一套人机交互式AGC液压缸试验台检测系统,采用厂级ERP企业管理系统,实时远程控制与测试,实现第三方与生产厂家的轧机AGC液压缸性能指标测试数据的检定、校准工作与报告生成。结果表明:该系统平台可有效提高轧机AGC液压缸性能指标测试数据准确性,测试功能满足第三方需求。

升船机钢丝绳-缓冲油缸防撞装置的动力学计算方法

钢丝绳-缓冲油缸防撞装置目前已在多座升船机中得到应用,其防撞吸能是一个较为复杂的动力学过程,目前还未有研究涉及。根据钢丝绳-缓冲油缸防撞装置的工作原理,在考虑水体对船舶的水动力作用、钢丝绳弹性变形、缓冲油缸溢流阀的限载功能等因素的条件下,建立包括船舶和钢丝绳-缓冲油缸防撞装置的两阶段二阶非线性动力学模型,提出对升船机钢丝绳-缓冲油缸拦阻吸能装置关键性能参数进行分析的数值计算方法和防撞装置安全性评估方法。应用提出的方法对向家坝升船机钢丝绳-缓冲油缸防撞装置进行了动力学数值仿真计算,并与向家坝升船机实船撞击试验结果进行了比较分析,说明提出的动力学计算方法与实船试验结果基本吻合且偏于安全,可为钢丝绳-缓冲油缸防撞装置的设计和校核提供参考。

GDS空心圆柱仪动力试验能力探讨

为更好地模拟多向应力和主应力轴旋转等复杂应力路径,与英国GDS公司合作研发了能施加轴向和扭矩动载的空心圆柱仪。文中介绍了该仪器的工作原理和性能,分析对比了其与传统单向动三轴仪试验结果,并探讨该空心圆柱仪所完成的5组典型动力荷载及一组不规则随机波动力试验能力。动力加荷时,通过调整设定刚度参数,实测波形与设定波形误差较小。该仪器能很好地模拟地震、波浪和交通荷载引起的应力,为研究复杂应力状态下土体动力本构关系提供了很好的工具。

原状海洋土动泊松比的试验研究

利用空心圆柱扭剪(HCA)仪,针对原状海洋粉质黏土,通过循环三轴及循环扭剪试验,得出相应的杨氏模量、剪切模量和动泊松比,探讨了有效固结围压、固结应力比对动泊松比的影响。试验结果表明:土体的动泊松比随着广义剪应变的增大而增大;有效固结围压、固结应力比均对动泊松比有显著的影响,动泊松比随着有效固结围压、固结应力的增大而逐渐减少;且随着广义剪应变的增大,两者对动泊松比的影响减小,当广义剪应变增大到1.8×10-2左右,试验终止,此时土体动泊松比约为0.48。试验中未出现动泊松比大于0.5的现象,说明土体未出现剪胀现象,试验所采用的粉质黏土在循环荷载作用下具有较好的稳定性。

砂土非共轴特性的本构模拟

传统的本构理论隐含了应力和塑性应变率的共轴条件,无法客观描述主应力轴旋转试验中的非共轴现象。因此,在已有的本构模型中引入非共轴塑性流动理论来描述这种非共轴现象,并对形状函数进行了修正。通过对真三轴试验、单剪试验和空心圆柱试验进行数值模拟,表明修正后的形状函数能够更好地描述砂土在真三维状态下的变形特性,更重要的是非共轴理论的引入使得模型能够合理预测主应力轴旋转过程中主应力和主应变率的方向变化规律。

加载路径对粗粒土非共轴性影响的试验研究

采用空心圆柱扭转仪,对Portaway砂进行排水试验,研究粗颗粒砂土主应力和主应变增量的非共轴性,以及应力路径(历史)对砂土非共轴性的影响规律。试验分两个系列,系列1中试件在排水固结后直接沿着固定的主应力方向进行加载,系列2中试件在排水固结后先进行轴向压缩,再沿着与系列1同样的加载路径剪切。试验进一步验证了颗粒材料的非共轴特性。试验结果显示:非共轴度与材料的加载方向密切相关,加载历史对于非共轴度有一定的影响;随着试件接近破坏状态,主应力和主应变增量趋于共轴。