高层中间层隔震结构的非线性动力分析

采用时程分析方法,分析高层隔震结构在罕遇地震作用下的响应.主要包括结构的塑性变形和塑性发展情况,结构的层问位移及楼层加速度响应.结果表明,在罕遇地震作用下,隔震结构进入塑性的程度较轻,震后稍加修复即可继续使用.塑性铰最先出现在结构底部,逐渐向上层开展.塑性铰均产生在梁端,柱端始终未出铰.楼层位移主要集中在隔震曾层,但上...     

超限倾斜结构的弹塑性动力分析

结合克拉玛依市科技博物馆工程,对超限倾斜结构设定性能设计目标,并针对性能目标提出抗震措施及抗震构造措施.考虑结构材料的非线性属性,采用静力非线性分析方法,分析倾斜框架-剪力墙结构在地震作用下的响应,尤其是结构在罕遇地震作用下的非线性动力特性基于罕遇地震的弹塑性时程分析表明,最大层间位移角满足1/100的限值条件.结构在...     

致密砂岩油层改造压力作用下双筒液压封隔器弹塑性承载能力三维数值分析

采用三维弹塑性有限元法,对双筒液压封隔器在油层改造压裂液压力作用下的变形行为进行计算和分析,得到在给定的工作压力下封隔器心轴各处的应力分布和塑性应变分布.主要的结论有:(1)在给定的95 MPa(13 775 psi)的压力下,最大等效应力达到102 MPa(14 800 psi),远远超过初始塑性屈服极限,表明结构中部分材料点进入塑性变形状态.(2)等效塑性应变的最大值为1.6%,分布在螺纹沟槽的底部.穿压孔两侧有明显的塑性变形区.(3)当载荷达到额定工作压力95MPa(13 775 psi)的60%时,应力开始达到初始塑性屈服极限,塑性应变开始出现,其出现的区域部位处于螺纹沟槽底部,环向位置大致在2个穿压孔中间位置上.该数值分析结果可为封隔器液压承载能力的确定提供参考.     

锚固承载层作用下巷道围岩稳定性分析

针对现有巷道围岩稳定性控制方法是将锚杆支护阻力均匀作用于巷道表面,较少考虑锚杆与围岩耦合形成的锚固承载层的等效支护力问题,通过分析围岩力学模型得出锚固承载层等效支护力的解析表达式及巷道围岩在锚固承载层作用下的弹性区与塑性区应力、塑性区半径和巷道围岩表面位移的解析表达式。算例分析结果表明:(1)锚杆长度增加时,锚固承载层厚度随之增大;锚杆长度一定时,随着锚杆排距的增加,锚固承载层厚度减小;锚固承载层等效支护力随着锚固承载层厚度的增大而增大。(2)在塑性区中,相对于不考虑锚固承载层的Fenner解,考虑锚固承载层的本文解下的围岩切向应力较大,应力峰值位置更接近巷道中心位置;在弹性区中,相对于Fenner解,本文解下的围岩切向应力较小,径向应力较大。(3)随着锚固承载层等效支护力的增大,塑性区半径呈下降趋势;随着锚固承载层等效支护力的增大,Fenner解与本文解下的巷道围岩表面位移减小,且Fenner解下的位移变化量比本文解下的大。利用Flac3D软件对锚固承载层作用下的巷道围岩应力、塑性区半径和巷道表面位移进行数值模拟,数值模拟结果与算例分析结果基本一致,锚固承载层作用下巷道围岩稳定性更为可靠。     

压电纳米控制器

正(2015-19-俄罗斯-4)1.压电纳米控制器PSF-3纳米控制器PSF-3是一种3轴控制系统,由操纵杆或计算机控制,集高分辨率(~0.4nm)、持续温度稳定(在20℃情况下,漂移小于2nm/h)和大位移(每轴10mm)于一体。结构的技术诀窍在于外方开放的压电马达PM-20R及其控制原理。当电机断电时,它可以自动锁定运动,几乎没有死角和漂移。技术性能指标:位移范围10 mm最小步0.4 nm漂移(20°C情况下)2 nm/h速度范围(步–连续)5нм/s-500мкм/s压电冲击(位移/加速)1-40мкм/g最大承载能力1.5 k G     

秭归县典型高切坡稳定性评价

通过有限元软件ABAQUS对秭归某高切坡进行数值模拟,以塑性应变区贯通、位移突变和计算不收敛作为失稳判据,用强度折减法求出边坡稳定性系数。计算结果表明该高切坡在天然状态下稳定性良好,在降水影响后稳定性系数略高于安全系数,整体稳定性较好,但需要局部加固。     

UNIX／XENIX操作系统关机命令的使用技巧

一、问题的提出 在UNIX/XENIX多用户操作系统中,各个用户都是通过注册名和口令在各自的注册帐户下行使自己的系统权限的。系统对每个文件实行了三级保护(文件的所有者、同组用户、其他用户)和三种权限(读、写、执行),从而大大加强了文件的保密性和安全性。 我们都知道,UNIX/XENIX操作系统之所以庞大(对PC机而言),是因为工作时要调度在系统中工作的各个用户的进程、管理系统,以便对各个用户的运行程序提供最佳的系统资源。所以,当我们开机,进入UNIX/XENIX系统时,就不会像进入DOS系统那样,很快地进入工作状态,而是需要稍作等待,让系     

让Vista也有开机修复

Windows 7集成了Win RE(Windows Recovery Environment,恢复环境)的"开机修复功能",开机时按下F8功能键可以进入高级引导界面,排列在最顶端的是"Repair Your Computer"(修复电脑)引导项(见图),利用该项可以在系统出现问题时进行修复。将这一恢复系统移植到Vista下进行使用,岂不更爽?     

直接数字频率合成器的FPGA设计与实现

在节约成本的前提下,为了提高主频频率,实现复杂的调制功能并具有良好的实用性,由相位概念出发,利用高性能的现场可编程门阵列(FPGA)器件(ACEXEP1K50)设计符合自己性能指标的要求的直接数字频率合成(DDS)电路,实现直接数字频率合成器的设计。对设计工作原理、电路结构进行了详细介绍,对设计的性能指标进行严格测试,同时提出了优化方法更好的提高了性能指标。设计结果达到预期效果,性能指标优良。     

虚共存细胞结构纵横加工向量机上向量无冲突存取方法

本文讨论虚共存细胞结构纵横加工向量机上无冲突的向量位移的有关性质,在此基础上对各种无位移冲突的向量的自动访问和对压缩、还原、扇出、复置等特殊的向量处理给出了实现的具体方法,并给出了用于N~(1/2)×N~(1/2)方块向量的高效并行算法的数据调度方法。文中提出的方法位移步数少,控制信息需要的计算量小,从而使虚共存机面向的主要数据调度能高效实现。     

Distinct element method analysis of a retaining wall using a steel frame and fill materials

A technique is developed to clearly establish the shear resistance of a cellular structure, retaining wall composed of a steel frame and fill materials with both continuous and discontinuous characteristics. To overcome the limitation of the existing analysis approach based on continuum mechanics, in which the shear behavior and interaction between the frames and fill material of this type of structure are difficult to describe, this paper introduces displacement incremental analysis into the distinct element method. The results obtained by using the proposed approach are compared with experimental results to verify its accuracy. The results show an internal friction angle of fill materials and overburdening load are major factor determining the shear resistance of a retaining wall with a cellular structure type. From the results of the parametric study on the shear behavior of this type of structure, this paper also proposes a shear resistance moment-shear displacement formula for designing a retaining wall with a cellular structure type.     

Design of high-bandwidth high-precision flexure-based nanopositioning modules

This paper presents the design of a single degree-of-freedom high-bandwidth high-precision nanopositioning module for high-throughput nanomanufacturing applications. Compared with widely used lumped-compliance mechanisms (using notch-flexure hinges) and distributed-compliance mechanisms (using compliant flexure beams), this nanopositioning module adopts a hybrid compliant-notch-flexure-based structure. This flexure design decouples the performance requirements for the structural bandwidth and parasitic accuracy that are correlated in the lumped-compliance mechanisms and distributed-compliance mechanisms. The parallelogram hybrid compliant-notch-flexure-based structure enables simultaneous achievement of a higher structural bandwidth and a smaller parasitic motion. The behavior of the nanopositioning module is analyzed theoretically with respect to its design parameters and performance objectives. Finite element analysis is adapted to study the dynamic responses and parasitic displacement of the designed nanopositioning module. The results from the theoretical and FEA analysis demonstrate the effectiveness of the hybrid compliant-notch-flexure design over commonly used lumped-compliance mechanisms and distributed-compliance mechanisms, especially when a high structural bandwidth is required for high-throughput nanomanufacturing applications.     

Using genetic algorithm for the optimization of seismic behavior of steel planar frames with semi-rigid connections

Beam-column connections have a significant role in the results of the analysis and the design of steel frames. In this paper, a genetic algorithm has been used for the non-linear analysis and design of steel frames. For minimizing the weight of frames, while satisfying the applied constraints and restraints such as the limits of normal and combined stresses, criteria such as target displacement(s) and the number and locations of plastic hinges were used. To analyze and design the frame elements, I and box-shaped standard sections were used for beams and columns, respectively. Finally, some clues for finding optimizing semi-rigid connection stiffness values for beam-to-column connections have been obtained. The degrees of these rigidities are obtained by a genetic algorithm during the procedure of optimization in order to reach a frame with the minimum weight. SAP2000 structural analysis program was used to perform modal analysis and linear and non-linear static solutions as well as the design of the elements. A MATLAB program was written for the process of optimization. The procedure of optimization was based on a weight minimization carried out for 9 steel frames. Thus, the optimum connection stiffness could be obtained for minimizing the weight of the structure. The results show that the non-linear analysis gives less weight for short period frames with semi-rigid connections compared to those of linear ones. However, by increasing the periods of frames, much less weights are obtained in the case of non-linear analysis with semi-rigid connections.     

An interface finite element for the simulation of localized membrane-bending deformation in shells

The folding of thin shells around localized lines occurs in several situations of engineering interest, such as in buckling induced deformation, as the consequence of crash, in industrial processes like metal forming, in the deployment of folded membranes, in packaging related processes. In this paper an interface element, allowing for displacement and rotation discontinuities, to be placed between two adjacent 4-node Mindlin–Reissner shell finite elements, is developed for a computationally effective simulation of this type of localized deformation. The large displacement and rotation kinematics of the interface element is discussed, arriving at a rigid-rotation free element tangent stiffness matrix. An adaptive dynamic relaxation scheme is proposed for the evolutionary analysis of the quasi-static structural response. To test the element formulation, a simple coupled membrane-bending elastoplastic behavior is assumed. The element is used for the simulation of few examples taken from the literature, where the structural response is characterized by the formation of plastic hinges, exhibiting good accuracy and computational effectiveness.     

On the importance of cross-sectional flexibility on gross response

Most nonlinear analyzers like ACTION and PLANS do not account for cross-sectional flexibility of thin-walled frame members. They do however, permit simulation of plastic hinges. Judging by the excellent correlation between theory and experiment, such analyzers appear quite adequate in predicting reasonably accurately gross response parameters of thin-walled frame structures even though they may undergo severe cross-sectional deformations.     

Wind turbine integrated structural and LPV control design for improved closed-loop performance

An iterative redesign algorithm is proposed to integrate the design of the structural parameters and a linear parameter-varying (LPV) controller for a three-bladed horizontal-axis wind turbine. The LPV controller is designed for an eighth-order lumped model of the wind turbine consisting of blades, drive-train and the tower. The lumped model response is matched with detailed open-loop numerical simulations using the Fatigue, Aerodynamics, Structures and Turbulence (FAST) code. The controller is scheduled in real-time based on the mean wind speed to account for the varying system dynamics. The objective is to track the operating trajectory meanwhile minimise the H _∞ performance index from the wind turbulence to the controlled output vector consisting of pitch angle, blade tip deflection, and the generator speed and torque. Sensitivity analysis of the closed-loop performance index with respect to the structural parameters of the system is examined. The integrated design problem is formulated as an iterative sequential controller/structure redesign to obtain the structural parameters and controller matrices corresponding to a local optimal performance index. Each step of the iterative procedure is formulated as a linear matrix inequality (LMI) optimisation problem that can be solved efficiently using available LMI solvers. The evolution of the structural parameters and performance index through the integrated design is illustrated. The FAST closed-loop simulations for two selected designs with the smallest values of the performance index demonstrate the improved performance of the overall system through the integrated structure/control redesign in both minimising the effect of the wind disturbance on the generator output power, and reducing the structural loads on the wind turbine.     

Optimal design of a micro-positioning Scott-Russell mechanism by Taguchi method

In this paper, main features in kinematics of a micro-positioning Scott-Russell (SR) mechanism associated with two flexure hinges are its displacement amplification and straight-line motion, which are widely needed in practical industries. Without increasing the radial displacement, the SR mechanism is optimally designed by Taguchi method to obtain a maximum amplification of a small displacement driven by a lead zirconate titanate (PZT) actuator. According to kinematic characteristics of the SR mechanism the control factors include the direction, radius, width and offset of flexure hinges. It is found that the directions and offsets of flexure hinges have obvious effects on the amplifying factor and linearity ratio. The software ANSYS is utilized to obtain the numerical simulations, which are compared with the experimental results for the SR mechanism with and without offset of flexible hinges. Finally, some conclusions about the effects of control factors on the performance of the SR mechanism are drawn.     

武器装备维修服务质量的灰色模糊综合评判

文章介绍了服务质量评价的理论并综述了维修服务质量评价研究,结合武器装备维修行业的具体情况,构建了多指标、多层次的武器装备维修服务质量指标体系,以企业A和企业B为案例,运用灰色模糊综合评判法对其服务质量指标体系进行了评估,评估结果表明该指标体系适用广,增强了评价结果的准确性和客观性.