饱和土地基的单质点模型参数解答

基于饱和土动力柔度系数的解析解,计算了相应的实用化质—弹—阻参数,结果表明,饱和土参数与相同条件下非饱和弹性半空间的数值有明显差异,宜乘以提高系数予以修正。

堆石体碾压密度值附加质量法测试研究

文章介绍了附加质量法测定碾压堆石体密度值的基本原理,通过附加质量法密度测试参数的选择对测试结果(附加质量法与坑测法结果比较)的影响,对选择合适的参数提出建议。结合洪家渡水电站、长河坝水电站大坝堆石体现场密度试验测试结果,两种检测方法相关性进行比较。

BISQ model based on a Kelvin-Voigt viscoelastic frame in a partially saturated porous medium

Taking into account three important porous media mechanisms during wave propagation （the Biot-flow, squirt-flow, and solid-skeleton viscoelastic mechanisms）, we introduce water saturation into the dynamic governing equations of wave propagation by analyzing the effective medium theory and then providing a viscoelastic Biot/squirt （BISQ） model which can analyze the wave propagation problems in a partially viscous pore fluid saturated porous media. In this model, the effects of pore fluid distribution patterns on the effective bulk modulus at different frequencies are considered. Then we derive the wave dynamic equations in the time-space domain. The phase velocity and the attenuation coefficient equations of the viscoelatic BISQ model in the frequency-wavenumber domain are deduced through a set of plane harmonic solution assumptions. Finally, by means of numerical simulations, we investigate the effects of water saturation, permeability, and frequency on compressional wave velocity and attenuation. Based on tight sandstone and carbonate experimental observed data, the compressional wave velocities of partially saturated reservoir rocks are calculated. The compressional wave velocity in carbonate reservoirs is more sensitive to gas saturation than in sandstone reservoirs.

动力机器基础振动与设计若干问题的讨论

讨论了《动力机器基础设计规范》(GB 50040-96)中的若干问题,包括质-弹-阻模型、地基动力参数、荷载组合和基础的构造要求等几个方面。对动力响应,基于弹性半空间理论定义质-弹-阻模型中引入的各个参数(频变),基于该模型计算稳态荷载或暂态荷载作用下基础的动力响应;引入承载力、变形和稳定性等的验算,并在基础的形状尺寸、埋深、材料、配筋等构造方面为设计人员提供指导;对基础的重要程度进行分类,对重要基础,特殊场地条件下的基础,建造时宜考虑沉降等观测手段,及可改变基础固有特性和加固维修等相关的措施。

Vertical human-induced vibration of pedestrian bridge

The double degrees-of-freedom（DOFs）parallel model is adopted to analyze static vertical human-induced vibration with the finite element analysis（FEA）method.In the first-order symmetric vibration mode,the periods of the spring-mass model gradually decrease with the increase in K1 and K2,but they are always greater than the period of the add-on mass model.Meanwhile,the periods of the spring-mass model decrease with the decrease in m1 and m2,but they are always greater than the period of the hollow bridge model.Since the human＇s two degrees-of-freedom vibrate in the same direction as that of the bridge mid-span,the existence of human＇s rigidity leads to the reduction in the rigidity of the spring-mass model.In the second-order symmetric vibration mode,the changes of rigidity K2 and mass m2 result in the disappearance or occurrence of some vibration modes.It can be concluded that compared with the spring-mass model,the results of the add-on mass model lean to lack of safety to the structure;besides,the DOF with a smaller ratio of mass to rigidity plays the chief role in the vibration of the structure.

成层地基与浅埋结构物动力相互作用的简化分析

基于任意侧向位移下挡土墙地震土压力理论,建立了新的地基-浅埋式结构物相互作用力与其相对位移之间的关系,并对该关系加以推广,应用到成层地基及深基础情形。提出了一种实用的求解成层地基-浅埋式结构物动力相互作用的简化质-阻-弹模型,该方法概念简单合理,参数确定简便,不需迭代,计算量小,可适用于以下情形:1) 结构物可视为粘弹性介质;2) 地基和浅埋式结构物可简化为一维运动;3) 结构物运动对土体运动的影响忽略不计。

变刚度地基—浅埋式结构物动力相互作用的简化分析方法

提出了一种求解变刚度地基－浅埋式结构物动力相互作用的简化质－阻－弹模型，并基于张建民等提出的任意侧向，位移下挡土墙地震土压力理论，建立了该模型所需的土体－结构相互作用力与相对位移之间的关系，由此而形成的简化分析方法可透用于以下情形，（1）结构物可视为粘弹性介质，（2）地基和浅埋式结构物可简化为一维运动，（3）结构物运动对土体运动的影响忽略不计，通过对变刚度地基中结构物的动力响应的计算分析，表明该方法合理，收剑性好，计算量小，具有较强的实用性。

Porous-grain–upper-boundary model and its application to Tarim Basin carbonates

Most of the carbonates in the Tarim Basin in northwest China are low-porosity and low-permeability rocks. Owing to the complexity of porosity in carbonates, conventional rock- physics models do not describe the relation between velocity and porosity for the Tarim Basin carbonates well. We propose the porous-grain-upper-boundary （PGU） model for estimating the relation between velocity and porosity for low-porosity carbonates. In this model, the carbonate sediments are treated as packed media of porous elastic grains, and the carbonate pores are divided into isolated and connected pores The PGU model is modified from the porous-grain-stiff-sand （PGST） model by replacing the critical porosity with the more practical isolated porosity. In the implementation, the effective elastic constants of the porous grains are calculated by using the differential effective medium （DEM） model. Then, the elastic constants of connected porous grains in dry rocks are calculated by using the modified upper Hashin-Shtrikman bound. The application to the Tarim carbonates shows that relative to other conventional effective medium models the PGU model matches the well log data well.

Firmness evaluation of melon using its vibration characteristic and finite element analysis

The “Huang gua” melons were measured for their physical properties including firmness and static elastic modulus. The vibrational characteristics of fruits and vegetables are governed by their elastic modulus (firmness), mass, and geometry. Therefore, it is possible to evaluate firmness of fruits and vegetables based on their vibrational characteristics. Analysis of the vibration responses of a fruit is suggested for measuring elastic properties (Firmness) non-destructively. The impulse response method is often used to measure firmness of fruits. The fruit was excited using three types of balls (wooden, steel and rubber) and the vibration is detected by an accelerometer. The Instron device was used to measure the static elastic modulus of the inner, middle and outer portions of melon flesh. Finite element (FE) technique was used to determine the optimum excitation location of the chosen measurement sensor and to analyze the mode shape fruits. Four types of mode shapes (torsional or flexural mode shape, first-type, second-type spherical mode and breathing mode shape) were found. Finite element simulation results agreed well with experimental results. Correlation between the firmness and resonant frequency (r2=0.91) and between the resonant frequency and stiffness factor (r2=0.74) existed. The optimum location and suitable direction for excitation and response measurement on the fruit were suggested.

庙子坪岷江大桥地震反应分析

文章主要介绍在桥梁抗震中 ,地基与基础相互作用的分析方法及集中质量法在连续刚构桥抗震中的应用。

Fluid-solid interaction of resistance loss of flexible hose in deep ocean mining

The resistance loss of transportation was studied and the influences of buoyancy layout,mineral content and elastic modulus of flexible hose were investigated based on three-dimensional finite element model of fluid-solid interaction by MSC.MARC/MENTAT software.The numerical results show that the resistance losses increase with the increase of mineral content Cv and velocity of internal fluid v and decrease with the increase of elastic modulus E of flexible hose.The buoyancy layout and the velocity of internal fluid have greater impacts on the resistance losses than the elastic modulus of flexible hose.In order to reduce the resistance losses and improve the efficiency of the deep-ocean mining,Cv and v must be restricted in a suitable range (e.g.10%-25% and 2.5-4 m/s).Effective buoyancy layout (such as Scheme C and D) should be adopted and the suitable material of moderate E should be used for the flexible hose in deep-ocean mining.

Real-time Animation Technique for a Kind of Non-rigid Objects

A real-time animation technique for a kind of non-rigid objects, flexible and thin objects, is proposed, which can update with stability the state of n mass points of the mass-spring (MS) modei with time complexity of O (n ). The new implicit numerical integration technique of the authors, which is based on a simple approximation of the linear system, has great advantages over the existing implicit integration methods. Moreover, experiment shows that the new technique is highly efficient in animating a kind of non-rigid objects, and suitable for the draping module of the 3D garment CAD system.

Modeling the Tensile Properties of Soybean Protein Yarns

The tensile properties of a series of soybean protein yarns are tested in USTER THINKPAID Ⅲ. A nonlinear viscoelastic model has been proposed to describe the tensile behavior of soybean protein yarns. The model is composed of a Maxwell element, a linear spring and a nonlinear spring. The tensile properties of soybean protein yam are analyzed. The stress-strain curves of the yams are fitted. The average breaking tenacity and specific work of rupture are calculated using the average breaking strain. Comparisons indicate that theoretical predictions conform the experimental results very well.

A Study of Intermediate Energy Proton-^16O Elastic Scattering Based on the α-Particle Model

In the framework of KMT multiple scattering theory, an optical potential for the intermediate energy proton-160 elastic scattering is presented based on the α particle model of 160. The differential cross sections, the analyzing powers, and the total cross sections of the intermediate energy proton-160 scattering have been calculated by using the obtained optical potential. The main features of the measured angular distributions of the cross section and the analyzing power can be well described. The calculated total cross sections are in good agreement with the experimental data at energies below 0.7 GeV and underestimate the data about 8% at higher energies.

NUMERICAL SIMULATION OF ATTENUATION OF LOVE-TYPE CHANNEL WAVES IN VISCOELASTIC MEDIA

Proceeding from wave equations, the paper strictly deduced the dispersion relation equation of Love-type channel waves in Standard Linear Solid model. The e quation is a complex one with its real part signifying the dispersion characteristics of the channel wave while the imaginary part, the attenuation characteristics. In calcu lating the attenuation value, the author has set up a mathematical model of a horizon tal symmetric sequence (a three layer sequence of rock-coal-rock), given out some physical parametersl and adopted the dichotomy method that is more of ten used in root resolving of an equatlon. The calculation indicates that the influence of non-elas tic absorption on the attenuation of the propagation of channel wave varies with the frequency. In the frequency band of the Airy phase, the attenuation increases steep like, which is unfavorable for the channel wave seismic prospecting. The study of channel wave attenuation has provided a theoretical basis for the compensation of at tenuation.

Model updating based on incomplete modal data

The objective of model updating is to improve the accuracy of a dynamic model based on the correlation between the measured data and the analytical (finite element) model. In this paper, we intend to update the mass and stiffness matrices of an analytical model when only modal frequencies or spatially incomplete modal data are available. While the proposed method is systematic in nature, it also preserves the initial configuration of the analytical model, and physical equality and/or inequality constraints can be easily incorporated into the solution procedure. Numerical examples associated with a simple 5-DoF (degree of freedom) mass-spring system are chosen to illustrate the detailed procedure and the effectiveness of the proposed method. Numerical scenarios ranging from the updating for stiffness terms only to that for all mass and stiffness terms based on various kinds of incomplete modal data are studied. The obtained model updating results are excellent when the measured modal data are noise-free. Uncertainty studies are also conducted based on simulations of corrupted modal data, but a thorough theoretical analysis of the noise effect on the proposed method is still needed.

A mass abrasion model with the melting and cutting mechanisms during high-speed projectile penetration into concrete slabs

In this study,ogive-nose projectile penetration into concrete slabs was tested at initial projectile impact velocities ranging from 1325.0 m/s to 1425.0 m/s.The depth of penetration and mass loss of the projectiles were measured,and the residual projectiles were recovered after the penetration tests.Scanning electron microscopy and metallographic microscopy of the microstructures were performed on various sections and outer surfaces of the projectiles taken from different locations of the residual projectiles,to analyze the intrinsic mechanisms of mass abrasion.The analysis results reveal that,during high-speed projectile penetration,projectile abrasion is caused by multiple mechanisms.Based on the cavity expansion theory,a projectile penetration model was established by considering the two main mass loss mechanisms observed in the microscopic tests.The theoretical predictions of the penetration depth,mass loss rate,and change of projectile head are consistent with the experimental results obtained both in this study and previous research.