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(句末括号内是相关的国家标准)1.题名:不超过20个汉字,中英对照,反映论文内容,包含尽可能多的关键词。避免非公知的字符和长的公式。(GB 7713)2.作者:中文及拼音(姓前名后,均不缩写)。国外作者按国际惯例。(GB/T 16159)3.作者单位:中英对照,数码编号与作者的上标一致,单位全称,所在省市及邮政编码,英文中加国家名。4.作者简介:第一作者的姓名,职称,最高学位,研究方向,Email。     

山西省中条山喀斯特发育特征及兴建水库工程可行性初探

中条山分布着大片的碳酸盐岩层。年降水量740mm, 年平均气温14℃。气候条件和多次的构造运动, 控制和决定了中条山喀斯特的发育程度、地貌景观, 以及岩溶地下水的赋存和运移特征。在水利水电建设中, 渗漏成了非常突出的工程地质问题, 对坝址选择产生了一定的影响。     

纳米晶体铝在单轴拉伸下的位错堆积对微裂纹扩展的影响

摘要：针对纳米晶体材料,研究了单轴拉伸载荷作用下纳米晶体铝中的裂纹与裂纹尖端发射的位错所形成的滑移面之间的相互作用。通过分布位错法,将裂纹和滑移面等效为均匀分布的连续位错,获得了裂纹面上应力场。并引入裂纹尖端的无位错区,研究了裂纹尖端无位错区对微裂纹的萌生和主裂扩展之间的影响。结果表明,不考虑裂纹尖端无位错区时,裂纹长度较短,会先在晶界处形成微裂纹,主裂纹较长时,主裂纹会直接穿晶扩展。滑移面与裂纹尖端夹角较大时,会增加裂纹尖端发射的位错个数,从而抑制主裂纹的扩展。考虑裂纹尖端无位错区时,无位错区先于晶界处出现微裂纹,通过主裂纹与微裂纹之间位错的相互发射,导致裂纹与尖端处微裂纹汇合,有效加速了主裂纹的扩展。     

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正在投稿、稿件处理、发表等过程中,作者需注意如下问题:1.稿件是作者独立取得的原创性研究成果,无抄袭,无一稿多投,未在国内外公开发表过。2.稿件无政治错误,不涉及保密和拟申请专利的内容,已经过作者单位保密审查。3.作者署名和排序无异议,单位署名和排序无争议,且无知识产权纠纷。在稿件处理过程中,如有作者或单位署名变更,需有全体作者亲笔签名和全部单位盖章同意的书面声明。4.稿件由编辑部组织审稿。自收稿之日时,编辑部将在4个月内反馈处理结果。若超过4个月未答复的,作者有权     

极端地质灾害与风险

极端地质灾害与风险是本文提出的一个概念。在地球演进过程中,极端地质灾害被认为是小概率事件。但这并不意味这种小概率的自然灾害只发生在遥远的未来,也不能排除这种事件发生在我们现在或者未来不久几代人中间。2008年汶川8.0级强震,吞噬了数万人的生命,大量的建筑被损毁,就是这种极端自然灾害的典型实例。它再一次向人类发出警告,一旦产生,后果将非常可怕。因此作者呼吁工程地质学家们要注意并研究这种极端灾害与风险。科学地判识可引发极端地质灾害的自然营力级别,为灾害预测提供基础,是工程地质工作的基本目标之一。地圈动力过程的区域研究将对实现这一目标有所帮助。评价一个地方的潜在风险,灾害影响区域的估计方法非常重要,同时对破坏结果和破坏对象易损性相关关系的进一步分析,可以得到一个灾害风险性级别。风险管理的策略中,预警措施和警告要受到足够重视,而不仅仅是工程防护。在极端风险减灾中,公众意识和对灾害的预备程度也同样重要。一系列的减灾的战略措施可以相应地制定出来,这不同于普通的安全设计标准和非工程措施。随着社会和技术的进步,在不久的将来,人类减少和管理极端自然灾害的能力必将大大提高。     

重庆大学工程力学系简介

重庆大学1978年设置应用力学专业,1985年创建工程力学系。1981年获固体力学硕士学位授权点,1986年获固体力学博士学位授权点,是全国较早获得硕士学位和博士学位授权点的单位之一。2003年获力学博士学位授权一级学科,2004年建立力学博士后流动站。2000年固体力学成为重庆市重点学科,2006年力学一级学科成为重庆市重点学科。     

有限元表面应力计算

用有限元[1]通用程序进行结构计算时,最常用的是位移法,因而计算得到的位移有较高的精度。由位移计算应力时,有限元法应用的是应力-应变关系和应变-位移关系,其中应变-位移是微商关系。在数值计算中,微商只能转化为差商等用插值近似处理。这样,虽然位移精度高,但应力的计算精度就被大打折扣。本文应用弹性力学辛体系理论[2],解析求解了位移和应力的影响函数。利用有限元程序计算得到的位移,由功互等定理,不需要微分插值,就可以得到指定点的应力,应力精度大大提高。工程实际中有许多问题的最大应力往往发生在构件表面。针对表面应力问题,本文给出了半平面表面应力的影响函数,进行了数值算例计算。计算结果表明,用本文提出的影响函数法求解一点的应力,其精度明显提高,并且计算结果有很好的稳定性。用本文的影响函数法编制成子程序,可作为有限元软件应力计算的一个模块,可以更好地发挥有限元程序的功效。     

基于滑动元法的连续拉索滑移分析

实际工程中,拉索在索撑节点处滑移十分普遍。考虑滑移的影响,索撑节点不能简单地用铰接模拟。现有的拉索滑移分析方法往往需要迭代,计算过程复杂且收敛性无法保证。本文提出一种拉索滑移分析新方法——滑动元法,以预应力鱼腹梁为例进行理论推导,介绍了滑动元法的基本原理和计算步骤。结合有限元软件,利用滑动元法对算例进行计算分析,结果表明,滑动元法计算快速无需迭代,可以较为准确地分析拉索滑移。     

考虑碳纳米管非均匀分布的复合材料电导率计算

碳纳米管作为导电相在机敏复合材料中广泛应用,但碳纳米管为团簇材料,在基体中很难均匀分散。本文考虑碳纳米管的非均匀分布特性,提出了计算碳纳米管复合材料电导率的数值方法。通过引入随机谐和函数,建立了碳纳米管体积分数的三维随机场模型。基于细观力学的有效介质理论、Mori-Tanaka方法和H-S界限理论,考虑碳纳米管之间的隧穿效应,发展了复合材料微小体积单元的电导率计算方法。在此基础上,构建了考虑碳纳米管非均匀分布的复合材料等效电导率三维有限元计算模型。数值分析结果与试验值能够很好吻合,表明这一方法可以准确计算碳纳米管复合材料的电导率。本文进一步分析了碳纳米管非均匀分布对复合材料电导率的影响。     

混凝土构件中钢筋非均匀锈胀应力研究

研究钢筋锈蚀引起混凝土保护层开裂的机理,对于评估受锈蚀影响的混凝土结构剩余寿命具有重要意义。本文提出了一种求解钢筋非均匀锈蚀应力场的解析方法。基于Muskhelishvili的复变函数法和Verruijt共形映射公式,利用基于冯·米塞斯分布的钢筋非均匀锈蚀模型作为位移边界条件,得到了钢筋非均匀锈胀应力的解析解。通过与基于ANSYS有限元模拟结果的比较,验证了解析解的有效性。对比了不同锈蚀模式下引起的应力,发现非均匀锈蚀引起的最大应力远大于均匀锈蚀引起的最大应力。通过实例探讨了影响钢筋锈胀力的各个因素,研究表明：钢筋直径越大,锈胀力越小,混凝土保护层越容易开裂;混凝土保护层厚度越大,锈胀力越大;混凝土强度等级越高,钢筋锈胀力亦越大。为易受锈蚀影响的钢筋混凝土构件设计提供了科学依据。     

A STUDY OF THE CATASTROPHE AND THE CAVITATION FOR A SPHERICAL CAVITY IN HOOKE’S MATERIAL WITH 1/2 POISSON’S RATIO

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A reduced-order model manifold technique for automated structural defects judging using the PGD with analytical validation

Automation is conquering new fields on a daily basis. Aiming for faster and more reliable products, industrials as well as researchers are oriented into automation. Non-destructive testing as well as defect quantification is not an exception. In fact, decisions with minimum allowable error are sought in real-time when facing any potential defect. In this work, we suggest a comprehensive method based on model order reduction techniques to judge if a structure shall be salvaged. The real-time decision is based on multidimensional parametric simulation, performed offline, using the Proper Generalized Decomposition (PGD). The PGD is a model order reduction technique that allows circumventing the curse of dimensionality by using domain decomposition. Therefore, the 6D simulation illustrated in this paper is performed within a few minutes on a standard laptop. Later on, a stress concentration manifold is built and used online for decision-making. The manifold is validated on a few selected solutions solved analytically using an analytical procedure. The aforementioned procedure is developed, in this paper, to calculate the tangential stress around circular holes of different sizes, in an infinite isotropic plate containing any number of holes and subjected to in-plane pressure loading at the tip of the infinite plate. The procedure is based on determining two Muskhelishvili complex potentials in terms of complex Fourier series, and applying the Schwartz alternating method repeatedly until the boundary conditions on the contour of every hole are satisfied.     

A study of directionality of latent hardening behavior in aluminium single crystals

By defining the yield stress in a latent hardening test as the first deviation from the elastic straight line, the yielding and hardening behavior on a latent system in the positive and negative slip direction was studied in aluminium single crystals. It is shown that the yield stresses on both the positive and negative latent systems are about equal to or a little lower than the maximum resolved shear stress in the primary test, but much higher than that of the active system. The influence of relative orientation and prestrain on latent hardening and initial work-hardening in the secondary test was also investigated, and it was found that there is a considerable effect on initial work-hardening, but none on latent hardening. With reasonable approximation, a hardening rule for single crystal could be proposed from the experimental results, that is, except for the yield stress on the system negative to the active system that is very low, hardening on the other systems is nearly the same as self-hardening.     

ANALYSIS OF GROUNDING CHARACTERISTICS AND STRAIN ENERGY OF RADIAL TIRES WITH RADIAL STIFFNESS1)

利用轮胎综合试验机对径向刚度下子午线轮胎进行性能试验,采用正交试验法针对不同胎压、垂向载荷下轮胎的接地特性进行分析,结合仿真软件ABAQUS与试验进行对比。结果表明,橡胶材料Mooney-Rivli模型也具有一定的适用性,胎压增大时径向刚度发生线性变化,胎面印痕由椭圆形转变成近似矩形,印痕面积略微增大;随着胎压的不断增大,胎面印痕的面积显著减小,接触面的压力主要集中在胎肩,胎冠处也有所增加;胎压一定时,垂向载荷逐渐增大时,整个印痕面的应力呈对称分布,印痕面应力由内高外低逐渐向外高内低变化。建立数学模型与有限元软件同时对轮胎进行应变能分析,发现在低胎压150 kPa下受载荷时轮胎容易发生微小侧向位移同时发生变形,此时极易引起迟滞损失并造成应变能急剧增加。     

The onset of convection in a shallow box occupied by a heterogeneous porous medium with constant flux boundaries

The effects of hydrodynamic and thermal heterogeneity, for the case of variation in both the horizontal and vertical directions, on the onset of convection in a horizontal layer of a saturated porous medium uniformly heated from below, are studied analytically using linear stability theory for the case of weak heterogeneity. Attention is focused on the case of constant flux upper and lower boundaries, a case for which the critical horizontal wavenumber is zero, and attention is also concentrated on the case of a shallow layer. It is found that the effect of such heterogeneity on the critical value of the Rayleigh number Ra based on mean properties is of second order if the properties vary in a piecewise constant or linear fashion. The effects of horizontal heterogeneity and vertical heterogeneity are then comparable once the aspect ratio is taken into account, and to a first approximation are independent. The combination of permeability heterogeneity and conductivity heterogeneity can be either stabilizing or destabilizing for the present case.     

THICKNESS-SHEAR VIBRATION OF CIRCULAR CRYSTAL PLATE IN CYLINDRICAL SHELL AS PRESSURE SENSOR

Based on the theory for small fields superposed on relatively larger fields in an electroelastic body, & theoretical analysis is performed on a circular plate thickness-shear crystal resonator sealed in a circular cylindrical shell for pressure measurement. A simple expression is obtained for pressure induced frequency shifts in the resonator, which is examined for design optimization. Numerical results show that the frequency shifts depend linearly on the pressure, and that a pressure sensor with a softer outer shell or a smaller thickness ratio of the crystal plate to the outer shell has higher sensitivity.     

铝单晶体潜在硬化的指向性行为研究

应用高纯铝单晶体，采用偏离弹性线法定义其在潜在滑移系统在屈服应力，研究了潜在滑移系在正负两个滑移方向上的屈服及应变硬化行为。结果表明，潜在滑移系负行为的差异要远远小于动滑移系的Ｂａｕｓｃｈｉｎｇｅｒ效应，其正负方向的屈服应力一般均等于或略小于预应变时的最大分切应力，大大高于动滑移系的负向屈服应力，潜在滑移系和原始滑移系的相对取向及预应变的大小对单晶体潜在移系在潜在硬化的影响不大，但对其起始过渡区应     

Methods of Solving Nonlinear Problems of Hydrodynamic Impact in Bounded Regions

The plane problem of separation impact on a plate floating on the surface of an ideal incompressible fluid in a bounded vessel is considered. In this problem the zone of contact between the body and the fluid is not known in advance and must be determined together with the fluid flow. As a result, the problem formulated is nonlinear and belongs to the class of free-boundary problems. The effect of vessel walls of different shapes on the fluid particle separation zone formed on the plate surface is studied. As examples, the problems for a layer or a truncated circular meniscus are considered.     

一种新的并行自适应网格有限元算法

给出了一种新的适用于流体力学问题的并行自适应有限元算法。首先，基于初始稀网格上获得的事后误差估算值，应用反复谱对剖分方法对初网格进行划分，使各子域上总体误差近似相等，从而解决并行自适应计算中的负载平衡问题。然后在各处理器上独立地求解整体问题，并进行指定子域上的网格自适应处理。最后将各子域上的自适应网格组合成一个整体网格，应用基于粘接元技术的区域分裂法在该网格上获得最终解。文末给出了数值实验结果。     

Asymmetric Surging of Ships in Following Seas and its Repercussions for Safety

A comprehensive investigation of an asymmetric longitudinal motion of ships displayed in long and steep following waves is presented. The focus is on the strongly nonlinear response, on the verge of the so called surf-riding condition, where a ship could be performing large-amplitude longitudinal oscillations around a mean forward speed. Expressions, in closed form, describing transient surge motion on the phase-plane are derived. For steady-state in particular, is shown that it is possible to determine an explicit analytical solution in the time-domain. Simple prediction formulae for the higher limit of asymmetric surging (threshold of global surf-riding) are derived on the basis of two alternative methods. Also, we investigate the effect of asymmetric surging on a ship's tendency for capsize in the neighborhood of wave crests where restoring capability is often reduced. The paper includes, as an Appendix, a review of types of ship instability and a summary of the historical roots of the field. For a better introduction to the subject we include, as Appendix A, a historical note on the evolution of the theory ship stability together with a summary of known types of ship instability distinguished on the basis of the angle of encounter between ship and waves.