Application of Ambient Stress Parameters to Short-Term Prediction of the 2004, M_S5.0 Shuangbai, Yunnan Earthquake

Based on the data recorded by the regional digital seismic network of Yunnan and using new methods, the short-term variations of the ambient stress field of Yunnan and its adjacent areas are monitored in real time. With the in-depth analyses of the spatial-temporal evolution of the ambient stress field prior to the 2004, Shuangbai M_S5.0 earthquake, concrete procedures for predicting the three elements of the earthquake are presented.

Determination of effective stress parameter of unsaturated soils:A Gaussian process regression approach

This article examines the capability of Gaussian process regression(GPR)for prediction of effective stress parameter(χ)of unsaturated soil.GPR method proceeds by parameterising a covariance function,and then infers the parameters given the data set.Input variables of GPR are net confining pressure(σ_(3)),saturated volumetric water content(θ_(s)),residual water content(θ_(r)),bubbling pressure(h_(b)),suction(s)and fitting parameter(l).A comparative study has been carried out between the developed GPR and Artificial Neural Network(ANN)models.A sensitivity analysis has been done to determine the effect of each input parameter onχ.The developed GPR gives the variance of predictedχ.The results show that the developed GPR is reliable model for prediction ofχof unsaturated soil.

Relationship among Parameters Evaluating Stress Corrosion Cracking

The threshold stress, σc, for sulfide stress corrosion cracking (SCC) of seven pipeline steels and five other steels, the critical stress, Sc, for seven pipeline steels and two drill rod steels with various strengths and the susceptibility to SCC, IRA or σf(SCC)/σf, for four pipeline steels, two drill rod steels and five other steels were measured. The results showed that there are no definite relationships among σc, Sc and IRA or σf(SCC)/σf.The threshold stress for hydrogen induced cracking (HlC) during charging with loading in the H2S04 solution, σc(H), decreased linearly with logarithm of the concentration of diffusible hydrogen c0, i.e., σc(H)=A-B Inco for four pipeline steels. σc(H) obtained with a special cathodic current ic, which was corresponding to the diffusible hydrogen concentration during immersing in the H2S solution, were consistent with /c for sulfide SCC for four pipeline steels. Therefore, σc for sulfide SCC can be measured using dynamically charging in the H2SO4 solution with the special cathodic current ic.

Advances in experiments and numerical simulations on the effects of stress perturbations on fault slip

Laboratory experiments and numerical simulations on rock friction perturbations,an important means for understanding the mechanism and influencing factors of stress-triggered earthquakes,are of great significance for studying earthquake mechanisms and earthquake hazard analysis.We reviews the experiments and numerical simulations on the effects of stress perturbations on fault slip,and the results show that stress perturbations can change fault stress and trigger earthquakes.The Coulomb failure criterion can shed light on some questions about stress-triggering earthquakes but cannot explain the time dependence of earthquake triggering nor be used to investigate the effect of heterogeneous stress perturbations.The amplitude and period are important factors affecting the correlation between stress perturbation and fault instability.The effect of the perturbation period on fault instability is still controversial,and the effect of the high-frequency perturbation on earthquakes may be underestimated.Normal and shear stress perturbation can trigger fault instability,but their effects on fault slip differ.It is necessary to distinguish whether the stress perturbation is dominated by shear or normal stress change when it triggers fault instability.Fault tectonic stress plays a decisive effect on the mode of fault instability and earthquake magnitude.Acoustic emission activity can reflect the changes in fault stress and the progression of fault nucleation,and identify the meta-instability stage and precursor of fault instability,providing a reference for earthquake prediction.

Physiological and Biochemical Responses of Wheat Subjected to Water Deficit Stress at Different Phenological Stages of Development

Proline has been proposed to be an osmoprotector and scavenger of reactive oxygen species in plants subjected to water deficit. The aim of this work was to study the effects of drought on each wheat phenological stage （tillering, booting, heading, flowering and grain-filling） using stress parameters such as the relative water content （RWC）, membrane stability index （MSI）, lipid peroxidation through malondialdehyde levels （MDA） and determination of proline content （PRO）. The Brazilian commercial elite cultivar Triticum aestivum cv. CD 200126 was submitted to eight days of water deficit stress at each stage. The perception of stress was low at tillering and high at the final stages of growth, as verified by the reduction in the MSI and RWC. However, an increase in the MDA was clearly observed. We observed a high proline accumulation when stress was applied, although it was not sufficient to prevent damages. These results indicate that the relevant stages to evaluate the effect of water shortage during wheat plant development are booting, heading and flowering.

Yield criterions of metal plasticity in different stress states

Five types of tensile tests were conducted to study the yield .behavior of 2A12-T4 aluminum alloy. Parallel finite element models were built for each test and solved with ABAQUS with different yield criterions. The result shows that any of the four criterions： von Mises yield criterion, Tresca criterion, Twin-Shear criterion and yon Mises criterion with hydrostatic pressure correction, overestimates the yield strengths of the specimens. Rather than hydrostatic pressure, Lode stress parameter is the key factor that affects the differences between experimental and simulation results. Based on this concept, a new yield model with Lode dependence modified from yon Mises criterion is postulated. Although one more parameter needs to be confirmed, the simulation results of this yield model are better than those of other criterions.

矿用减速器直齿轮强度动态有限元分析

传统的齿轮接触应力和弯曲应力是利用理论计算进行静强度校核。为了提高齿轮传动中接触应力和弯曲应力的计算精度与效率,利用Creo2.0软件快速建立了某矿用减速器直齿圆柱齿轮的参数化模型,并使用ABAQUS软件及其子模型技术对齿轮最大接触应力和齿根最大弯曲应力进行动态分析,从而为齿轮的设计及优化提供一种新的设计方法。

The Effects of Post-Stenotic Dilatations on the Flow of Couple Stress Fluid through Stenosed Arteries

The flow of incompressible couple stress fluid in a circular tube with stenosis and dilatations has been investigated. The stenosis was assumed to be axially symmetric and mild. The flow equations have been linearized and the expressions for the resistance to the flow, velocity, pressure drop, wall shear stress have been derived. The effects of various parameters on these flow variables have been investigated. It is found that the resistance to the flow and pressure drop increase with height of the stenosis and decrease with post stenotic dilatation. Pressure drop decreases with couple stress fluid parameter for both stenosis and post stenotic dilatation. Further, the wall shear stress increases with height of the stenosis and couple stress parameter but decreases with post stenotic dilatation and couple stress fluid parameter.

The space and time distribution characteristics of the shear stress field for the sequence of the Wuding earthquake

Follow Chen and Duda's model of spectral fall-off of ω~3, the dependence of peak parameters of ground motion, peak displacement d_m, peak velocity vin and peak acceleration a_m, upon the environment stress τ_o-values are studied using near source seismic digital recordings for the sequence of the Wuding, Yunnan, M = 6.5 earthquake, in which, as a new thought, the peak parameters are assumed to be related to the medium Q-value. Three formulae for estimating the environment stress τ_o-values by the peak parameters of three types of ground motions are derived. Using these formulae, the environment stress τ_o-values are calculated for the sequence of the Wuding earthquake. The result show that τ_o-values calculated by the three formulae are constant largely, the averages of τ_o are in the range of 5.0-35 MPa for most earthquakes. It belongs to the high-stress earthquakes sequence: the high-stress values are restricted to the relatively small area closely near to the epicenter of the main shock. The fine distribu tion structure for the contours of the environment stress τ_o-values is related closely to the strong aftershocks. The analysis of spatial and temporal feature of To-values suggests that the earthquakes sequence in a rupture process generated at the specific intersection zone of seismo-tectonics under high-stress background.

采用Solidworks的对数螺旋锥齿轮结构设计与力学分析

对数螺旋锥齿轮是机械传动机构中的重要零部件,运用SolidWorks软件结合C语言编程,建立了参数化齿轮数值表,并基于尺寸驱动参数化方法,创建了一对对数螺旋锥齿轮的三维模型。通过对齿轮进行啮合装配和运动分析,验证了所设置的齿轮参数的结构合理性。此外,利用Solidworks模块Simulation进行网格划分,进行了实体网格的非线性有限元分析。研究重点在于探究不同转矩载荷下螺旋锥齿轮啮合部位的最大接触应力、接触强度和接触应变等方面。这些研究结果能够确保设计的螺旋锥齿轮具备足够的强度和可靠性。经校核,对数螺旋锥齿轮的接触强度在最佳转矩范围内低于60.5 N·m,其啮合最大应力值小于材料的屈服极限,结果为对数螺旋锥齿轮的结构设计和传动强度提供了可靠的参考和方法,这对于相关领域的工程实践和齿轮设计具有重要的指导意义。

压力容器开孔区基于线性化结果的响应面优化分析

为确定经济、合理的结构,对承受交变载荷的压力容器开孔部位进行优化分析。将开孔部位结构尺寸设置为输入参数,将通过最大应力强度节点的线性化结果、交变应力幅、质量、应力集中系数等设置为输出参数,采用响应面优化方法,合理设置优化目标,确定出优化结果候选点。经分析和验证,响应面优化计算值与模型分析值偏差≤2.62%,实现了结构的优化设计,并能够对参数间的敏感性进行分析。

基于螺栓法兰连接系统的垫片应力分析

所建立的参数化三维有限元模型,充分考虑了法兰螺栓联接系统的应力集中、垫片材料非线性特性以及各元件的接触非线性,研究了螺栓法兰连接系统各元件之间的相互作用,分析了预紧力、密封介质内压力等因素对垫片应力的影响。结果表明垫片应力在径向随着节点半径的增大而增大,随着预紧力的增大而增大,随着内压力的增大而减小,在周向螺栓附近的应力明显大于其它处应力。当垫片最外侧应力低于了密封所要求的最低应力时,螺栓法兰连接系统发生泄露。

自增强超高压容器残余应力分析

为分析自增强超高压容器的残余应力,利用ANSYS的APDL语言开发了筒形超高压容器的参数化有限元模型,利用该模型并采用多载荷步法对容器自增强处理的加载过程和卸载过程进行了仿真。通过改变端部边界条件和材料参数研究了容器端部形式和材料参数对容器残余应力的影响。研究结果表明:端部形式对容器中部的周向应力和径向应力影响很小,对轴向应力影响较大,使轴向应力在内壁附近有较大的差别;切线模量不同,最大周向残余应力所在位置不同,大的卸载切线模量可以增大内壁处的周向残余应力。在ANSYS的BKIN材料模型下定义两种温度应力-应变曲线以分别模拟材料加载和卸载时的机械性能,准确地模拟了这类材料的应变硬化和鲍辛格效应,提高了残余应力预测的精度。

CFS/GFS混杂加固RC梁界面应力的参数化分析

采用非线性有限元方法对混凝土梁FRP粘胶层的界面力学性能进行参数化研究,并将所得的界面应力与解析解对比,吻合较好.在此基础上建立了CFS/GFS混杂加固梁界面有限元模型,并将其与双层CFS加固梁进行数值对比研究,结果表明:混杂加固可以有效地控制纤维布末端的界面剪应力,并且界面正应力也有所降低,这种加固方式具有优良的界面混杂效应.文中还就荷载、胶层弹性模量、胶层厚度、纤维布宽度对界面力学性能的影响进行了对比分析,计算结果表明:随着荷载与胶层弹性模量的增加以及胶层厚度的减小,端部界面应力成比例增加,而纤维布宽度在一定范围内变化时,端部应力基本上没有变化.

蒸发器异型管板有限元分析及优化设计

针对某异型管板蒸发器无设计标准可依,工程设计中管板较厚的问题,对该蒸发器管板的稳态温度场、机械场和热应力场进行三维有限元分析。分析结果表明,温度对蒸发器异型管板的应力强度影响较大,对现有管板工程设计进行优化。

剖分式卡箍的强度分析与结构优化

通过卡箍危险截面处结构模型,得到卡箍应力计算公式,并在ANSYS Workbench集成开发平台环境下,对卡箍参数化建模,进行优化分析,得到各参数对应力值影响的曲线图,分析各参数对应力值影响程度的大小,使得应力分布更加合理,优化后将卡箍最大等效应力控制在允许范围内.

制冷装置蒸发器异型管板的有限元分析

基于制冷装置蒸发器异型管板无设计标准可依的现状,对该系列蒸发器管板的稳态温度场和热应力场进行三维有限元分析。运用Visual Basic和ANSYS二次开发工具APDL,实现了管板的参数化有限元分析,并对该系列不同布管方式的3种管板进行了分析比较。分析结果表明,该系列蒸发器管板布管形式在一定范围内对管板强度影响不大,现有管板工程设计偏于保守,可进一步进行优化设计。

基于Solid Works的槽轮机构的建模及应力分析

以包装机械中常用的外槽轮机构的设计为例,利用Solid Works建立了槽轮机构参数化设计的模型;利用Solid Works中嵌入的COSMOSXpmss插件,对槽轮机构的零件进行应力分析,提高了槽轮机构的设计效率。

海气动量通量研究综述

海气界面动量通量也称为风应力,是海流和表面海浪的主要驱动力,是海洋从大气获得动量的重要途径。因此,合理可靠的海洋表面风应力的参数化对于海洋、大气和波浪以及气候模式的准确预报都具有非常重要的科学意义和实用价值。对风应力拖曳系数的参数化是风应力参数化的主要内容。近来的观测发现,风应力拖曳系数随着风速的增加出现了先增后减的趋势,同时还与海面的波浪状态以及海流有关。基于观测或理论分析,目前已经得到了一系列的风应力拖曳系数计算方法或公式,有的考虑了海浪的作用,有的没有,但这些方案大都是适合中低风速,在高风速下的适用性还有待检验。本文回顾了目前在海气动量通量观测和参数化方面的研究进展,并建议应增加高风速下风速、海流以及海浪等的同步观测,以进一步完善风应力参数化方案。

海面风应力拖曳系数参数化方案对风暴潮数值模拟的影响

为了比较不同的海面风应力拖曳系数参数化方案在风暴潮数值模拟中的效果,采用9种不同的风应力拖曳系数参数化方案对湛江附近海域15个热带气旋风暴潮进行数值模拟。模拟结果表明,不同风应力拖曳系数参数化方案对热带气旋风暴潮增水最大值的数值模拟效果不完全相同,在风暴潮数值模拟中要选择合适的风应力拖曳系数参数化方案;文中Smith(1980)、Yelland和Taylor(1998)风应力拖曳系数参数化方案增水最大值模拟的误差较小,这也说明两种参数化方案在风暴潮数值模拟中外推到热带气旋高风速范围内是可行的。另外,数值模拟结果也表明,在选择合适海面风应力参数化方案情况下,文中采用的风暴潮模式对强热带气旋增水的数值模拟效果较好。