共查询到20条相似文献，搜索用时 197 毫秒
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利用弯曲振动法测取了纤维板的声振动参数并进行了分析比较,结果表明:密度大的纤维板其振动加速度较大,振动能量损耗较低,声反射能力较强,但声辐射能力较弱;厚度小的纤维板其振动加速度较大,声反射及声辐射能力均较强,但振动能量损耗较高. 相似文献
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在进行噪声和振动的主动控制中,压电作动片因其具有重量轻、安装布置容易等优点,越来越受到重视.本文研究了压电复合纤维板的弯曲特性,对不同的边界条件、复合纤维板的不同纤维角度、不同的电压、压电作动片的不同厚度,具体分析了复合板的纵向位移.仿真结果显示了不同的边界条件对智能结构静态形状控制的影响. 相似文献
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为研究广甘高速公路边坡岩体在动荷载作用下的力学参数,分别对广甘路边坡岩块（体）开展室内和室外声波测试试验,通过试验测试的纵横波波速计算岩体动力学参数,在此基础上统计分析了岩体动力学参数与饱水程度、节理条数和岩体质量之间的关系。分析认为：水对岩体的动力学参数影响十分显著,饱水过程中,动弹性模量逐渐降低,泊松比逐渐变大;弱风化条件下,岩体动弹性模量受节理发育程度影响较明显,平均动弹性模量和节理条数之间可用公式Ed=-4.97n＋37（Ed为平均动弹性模量,n为节理条数）表述;而强风化条件下,节理条数对动弹性模量影响较小,其原因是岩体结构体受风化影响较为严重,节理对岩体动弹性模量的影响被相对弱化;同一岩体质量下,岩体动弹性模量和动泊松比的离散性均较大,但从大量数据的统计结果来看,Ⅳ级岩体的动弹性模量较大,动泊松比较小。 相似文献
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动与静是事物状态的两个方面,动中有静, 静中寓动,它们互相依存,并在一定条件下互相转化,在解题中,既要善于动中觅静,以静制动, 也要能够静中思动,以动求静,直到动静结合. 相似文献
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我在多头复式班的讲台上已度过了整整二十二个春秋.经过反复的试验摸索,对复式教学中一些带规律性的东西有了初步的认识。我感到,是遵循还是违背这些规律,是复式教学成败的关键。一、静与动怎样安排三个年级坐在一个教室,由同一个老师授课,必然有静有动。静与动如何安排,直接影响各年级的教学效果。这里的所谓动,是指有教师直接参与的教与学的活动;静则是指学生独立地学习.静与动都是相对而言的。在一个三头复式班里,教学上的静与动可分为三种情况,即静动静、动静静、静静动。动安排在中间的年 相似文献
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《浙江大学学报(A卷英文版)》2021,(9)
目的:目前的道面承载力评价需要在航班结束后进行,存在难以找到合适时间进行测试和模拟加载的缺陷。本文旨在通过分析飞机滑行过程中道面的振动响应,建立道面振动基频与承载力的关系,以实现飞机运行情况下道面承载力评价。创新点:1.根据飞机的真实运营情况,考虑升力的影响,确定了飞机的随机动荷载;2.分析了道面全宽度及11 m深度内的振动响应,确定了振动响应变化规律以及对振动基频影响最为显著的因素。方法:1.通过理论推导,建立飞机-道面系统平衡方程;考虑升力的作用,并结合边界条件,求解飞机的动荷载。2.通过仿真模拟,分析了全部道面范围内振动基频的变化规律及道面远端振动基频的影响因素。3.通过现场测试,验证测试方法的有效性和可行性。结论:1.当飞机的滑行速度超过15 m/s时,在升力的影响下,飞机的随机动荷载随着飞机滑行速度的增加持续下降;当飞机的滑行速度固定时,随着道面平整度变差,动荷载增大。2.沿横断面方向,道面中心处的振动基频仅比远端大2%;从面层至土基,振动基频不变,仅振幅逐渐减小。3.土基动回弹模量对道面远端振动基频的影响最为显著,可达43%左右,其次是面层厚度与基层厚度,而面层弹性模量与基层回弹模量对振动基频的影响最小。 相似文献
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Ultrasonic wave testing was applied to investigate the quality and weathering status of rock specimens obtained in two borings
situated in the Xishan Buddha rock slope in Taiyuan, China. This paper pays special attention to the distribution of bulk
density, dynamic parameters and static parameters of rock specimens as well as the relationship between static and dynamic
parameters. The results illustrate that the distribution of both parameters is identical along the depth of two drilled holes
in the rock slope. When the hole depth increases, the density of rock mass, saturated compression strength and static elastic
modulus, dynamic elastic modulus and wave velocity also show increase tendency. The weathering degree in the rock mass ranging
from the surface of cliff to the depth of 2.5 m is the highest while the rock mass is unsalted and more rigid when the depth
is larger than 3.0 m. The relationship between dynamic elastic modulus, sonic wave velocity and horizontal depth indicates
that dynamic elastic modulus is more sensitive than sonic wave velocity. Conversely, by comparing quantity relationship between
static elastic modulus and sonic wave velocity, it is found that the composition of rock has a great influence on the relationship
between static and dynamic parameters, that is, inequality of rock composition will lead to dispersion and abnormality of
the distribution of static and dynamic parameters. 相似文献
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利用ABAQUS有限元软件,开展不同材料微型桩—土动力相互作用的影响研究,桩身材料分别选为C40普通混凝土、C60普通混凝土、钢管混凝土、RPC混凝土。分析结果表明,由于弹性模量发生变化,不同材料微型桩的桩身弯矩存在明显差异;桩身材料的弹性模量过大会使微型桩的变形减弱;与静力荷载作用不同的是,动力荷载作用下的微型桩在上、下土层范围分别出现了一正一负两个较明显的桩周土反力峰值点。相关研究结论对指导微型桩的设计具有参考价值。 相似文献
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Firmness evaluation of melon using its vibration characteristic and finite element analysis 总被引：2，自引：1，他引：2
Nourain J Ying YB Wang JP Rao XQ Yu CG 《Journal of Zhejiang University. Science. B》2005,6(6):483-490
INTRODUCTION Researchers continue to develop non-destructive methods to evaluate the effect of their impact on ag-ricultural products using high-tech methods. Non-destructive techniques sensing has been applied for obtaining fruit and vegetable quality index. Non-destructive method for measuring firmness us-ing sonic or vibration characteristics applied in pre-vious investigations was recently reviewed by Arm-strong (1989) and Liljedahl and Abbott (1994). The sonic vibration technique u… 相似文献
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再生混凝土力学性能的研究 总被引：1，自引：0，他引：1
对再生混凝土力学性能的研究进行了综述，主要包括再生混凝土力学性能的抗压强度、弹性模量、干缩与徐变。研究表明，和普通混凝土相比，再生混凝土力学性能的抗压强度低，弹性模量小，干缩与徐变较大。最后提出了再生混凝土力学性能需要进一步研究的问题。 相似文献
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Numerical Analysis of Quality Inspection of Anchorage System 总被引：4，自引：0，他引：4
ZHANGYongxing XUMing 《重庆大学学报(英文版)》2002,1(1):42-46
Sonoprobe method has been applied in non-destructive inspection of anchorage project.The fundament is that dynamic transient excitation causes the elastic vibration of an anchor bar,and flaws can be estimated or deduced by determining transient response of the anchor bar.FEA numeric solution of hyperbolic equation indicates that deductions must comply with acoustic parameters such as velocity of sound,vibration range,wave shape etc when inspecting interior flaws in the grout of an anchor bar,Based on wavelet packet analysis,the energy eigenvector is a flaw vector,which could be regarded as the basis in the nondestructive inspection of anchors,As a non-linear dynamical system,artifical neural networks dealing with quality insection of gray system have been proved efficient. 相似文献
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高压输电线路导线跌落非线性动响应分析(英文) 总被引：1，自引：0，他引：1
为了研究机械性故障对高压输电线路耦合体系的受力影响,建立了输电线路耐张段的非线性耦合体系模型,通过导线找形非线性静力计算确定了耐张段的初始平衡状态.采用瞬态动力分析方法计算了导线、绝缘子破坏失效危险工况下的输电线路耦合体系非线性动响应.分析结果表明,上横担一组导线断裂失效对邻近端导线张力没有明显影响,对邻近端的绝缘子及铁塔横担构件的受力有较大的影响;上横担一组绝缘子破坏失效后,破坏档未破坏端导线的张力超过了技术规程中的设计值;导线的跌落对破坏档未破坏端的上横担绝缘子受力有较大的影响,而对上横担铁塔杆件没有明显的影响;在架空送电线路的设计中应该考虑绝缘子断裂的荷载工况.研究成果可为输电线路结构设计提供理论依据. 相似文献
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Numerical Derivation of Strain Rate Effects on Material Properties of Masonry with Solid Clay Bricks
In this paper, numerical method is used to study the strain rate effect on masonry materials. A typical unit of masonry is selected to serve as a representative volume element (RVE). Numerical model of RVE is established with detailed distinctive modeling of brick and mortar with their respective dynamic material properties obtained from laboratory tests. The behavior of brick and mortar are characterized by a dynamic damage model that accounts for rate-sensitive and pressuredependent properties of masonry materials. Dynamic loads of different loading rates are applied to RVE. The equivalent homogenized uniaxial compressive strength, threshold strain and elastic modulus in three directions of the masonry are derived from the simulated responses of the RVE. The strain rate effect on the masonry material with clay brick and mortar, such as the dynamic increase factor (DIF) of the ultimate strength and elastic modulus as a function of strain rate are derived from the numerical results. 相似文献
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ZHANG Gang YU Lie XIE You-bai School of Electromechanical Engineering Automation Shanghai University Shanghai China Xian Jiaotong University Xian China 《上海大学学报(英文版)》2000,(Z1)
1 IntroductionThe great majority of docUments about magneticbearings dealt only with the characteristics when thejournal was concentric with the radial magnetic bearing inthe past, and few research involved the ones when thejournal was eccotic with the radial magnetic bearing.For example, the bulk of documents suPPosed thecomponents Fx and F. of magnetic force depended onlyon the cUrred in x and y direchons respeGtively, bac theair gap thickness and the curvatUre of suiface shape werenot co… 相似文献
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This paper is based on the example of a radial magnetic bearing possessed of eight-pole, and derives the calculation formulas of
static and dynamic mechanical characteristics of the bearing, in which the shape and curvature of surface, eccentricity and tilt of the journal
are taken into account. Variations of the static and dynamic characteristics of the radial magnetic bearing versus static tilt parameters of
journal are discussed. The outcomes show that the static tilt of the journal has influence on the mechanical characteristics of radial magnetic
bearing, and change the static load capacity between two radial magnetic bearings and exert coupling effect between them. To study the
dynamics of a practical rotor-magnetic bearing system, at least six stiffness coefficients in each radial magnetic bearing must be considered
in ideal case, and twelve stiffness coefficients must be considered in general case of tilting journal. Such a find can be used for the coupled
electromechanical dynamics analysis of rotor system equipped with magnetic bearings. 相似文献
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钢桥面铺装用热固性环氧沥青混合料动态模量试验研究（英文） 总被引：1，自引：0，他引：1
为了研究热固性环氧沥青混合料的动态性能,对环氧沥青混合料的动态模量进行了试验研究.首先,通过简单性能试验（SPT）测试了不同温度与加载频率下的环氧沥青混合料动态模量,并分析了温度与加载频率对动态模量的影响.然后,分别对环氧沥青混合料的静态模量及其他常用沥青混合料的动态模量进行了试验测试,并将其与环氧沥青混合料的动态模量做了对比.最后,利用时温等效原理建立了环氧沥青混合料动态模量主曲线.研究结果表明：环氧沥青混合料的动态模量随加载频率的增加而增加,随加载温度的升高而降低;更符合实际车辆作用的环氧沥青混合料的动态模量较静态模量大得多;环氧沥青混合料的动态模量较SBS改性沥青混合料与普通沥青混合料大.研究成果可为钢桥面铺装的设计及力学分析提供理论依据. 相似文献