齿根初始裂纹倾角对圆柱齿轮疲劳寿命的影响

用有限元方法模拟圆柱齿轮齿根处疲劳裂纹的扩展过程.分析齿轮中疲劳裂纹的扩展路径和扩展形貌,依此设定合适的寿命积分路径,对齿轮的疲劳寿命进行预测,分析初始裂纹倾角对齿轮中疲劳裂纹的扩展形貌以及齿轮疲劳寿命的影响.结果表明:萌生于齿根处的疲劳裂纹,在齿廓面上朝着齿顶方向倾斜扩展,在齿端面上,从一侧齿根以圆弧状的扩展路径朝着对侧齿根扩展;对于相同的初始裂纹深度,初始裂纹的倾角较大,齿轮易发生轮缘断裂,其疲劳寿命相对较长,相反,初始裂纹的倾角较小,齿轮易发生齿根断裂,其疲劳寿命相对较短.     

地铁列车减速器直齿轮弯曲疲劳有限元分析与试验

为研究地铁列车减速器小齿轮齿根部受力情况及弯曲疲劳裂纹萌生的机理,通过建立齿轮副有限元模型,对齿轮啮合过程进行瞬态动力学分析,得到了齿轮啮合过程中齿根处的应力-时间历程进而对齿根弯曲疲劳行为进行了试验研究。瞬态动力学分析表明,小齿轮齿根处在啮合过程中受到脉动循环载荷的作用,最大拉应力出现在齿轮啮合至分度圆时;且齿根处最大主应力的方向为沿齿根切线方向。齿根弯曲疲劳试验结果表明,裂纹在齿根弧线的中间位置萌生,方向为齿根切线的垂直方向。结合有限元分析结果可发现,齿根处裂纹在最大拉应力幅值位置萌生,其扩展行为受最大拉应力的主导。为进一步优化齿轮的设计、制造工艺及材料的选择提供了依据。     

基于ANSYS的减速机齿轮有限元分析

采用有限元法研究齿轮轮齿在受到不同载荷的情况下,其齿根弯曲应力和应变的变化情况。结果表明,在静载荷的作用下,齿轮齿根处的最大弯曲应力和最大应变都在许可的范围之内;而当齿轮受到冲击,在动载荷作用下,齿根处的应力大于齿轮材料的屈服极限。结合对断齿形貌的分析,可推断出轮齿的断裂是在出现疲劳裂纹后受冲击载荷作用而产生的过载断裂。     

基于扩展有限元法的齿根裂纹扩展规律

探讨基于扩展有限元法的齿轮裂纹扩展计算方法,开展齿根初始裂纹扩展规律研究。借助Abaqus软件,分析齿根初始裂纹长度、方向和位置对裂纹扩展路径的影响规律,并与传统有限元法所得结果进行比较。研究结果表明:对于本文模型,齿根裂纹均为先朝深入轮缘的方向扩展,后朝向齿根位置扩展,总体呈现朝轮齿周向扩展至轮齿断裂的趋势;相对初始裂纹位置,其长度和方向对裂纹扩展路径的影响较小,不同长度和不同方向的初始裂纹的扩展路径没有显著差别;随着初始裂纹位置向齿顶趋近,裂纹扩展路径也整体向齿顶偏移;本文结果与传统有限元法所得结果基本一致,但仿真效率大大提高,为齿轮疲劳裂纹扩展及疲劳寿命的高效分析和精确预测提供一种新途径。     

机车电动机悬挂装置主动齿轮断裂分析

通过对提前破坏的电动机悬挂装置主动齿轮的宏观断裂形态、微观组织形貌、齿面硬度、轮齿受力状况的检查分析,发现齿轮折断是由于热处理工艺不当,导致齿根存在淬火裂纹以及局部齿面硬度不足,逐渐磨损失效,发生疲劳断裂.提出生产中应严格检查和控制齿轮热处理工艺,保证齿面硬度,避免淬火裂纹产生.     

基于动载荷谱的齿轮弯曲疲劳寿命预测

为了探讨齿轮弯曲疲劳寿命计算问题,将齿轮疲劳总寿命分为两个阶段,即疲劳裂纹萌生寿命和裂纹扩展寿命。通过 ADAMS 软件仿真实验齿轮的工作情况,使其接近真实状况,得到齿轮载荷谱。根据齿轮载荷谱,利用有限元ANSYS 软件分析在齿轮齿根危险截面处的最大应力。采用断裂力学、雨流法和 Miner 疲劳损伤累积模型,对考虑动载荷情况下的齿轮弯曲疲劳寿命进行预测,推导了齿根裂纹萌生期和扩展期的疲劳寿命计算公式。在高频疲劳试验机上对算例齿轮进行了双齿脉动加载齿根弯曲疲劳寿命实验研究,理论计算结果与实验结果基本吻合,验证了本文理论分析的正确性。     

基于动载荷谱的齿轮弯曲疲劳寿命预测

为了探讨齿轮弯曲疲劳寿命计算问题,将齿轮疲劳总寿命分为两个阶段,即疲劳裂纹萌生寿命和裂纹扩展寿命.通过ADAMS软件仿真实验齿轮的工作情况,使其接近真实状况,得到齿轮载荷谱.根据齿轮载荷谱,利用有限元ANSYS软件分析在齿轮齿根危险截面处的最大应力.采用断裂力学、雨流法和Miner疲劳损伤累积模型,对考虑动载荷情况下的齿轮弯曲疲劳寿命进行预测,推导了齿根裂纹萌生期和扩展期的疲劳寿命计算公式.在高频疲劳试验机上对算例齿轮进行了双齿脉动加载齿根弯曲疲劳寿命实验研究,理论计算结果与实验结果基本吻合,验证了本文理论分析的正确性.     

斜齿轮传动过程的力学性能及疲劳寿命预测

根据齿轮传动中轮齿折断和齿面点烛疲劳破坏现象,基于齿轮啮合原理,对斜齿轮啮合过程的力学性能及疲劳寿命预测进行研究,结合实例分析计算齿轮传动过程中齿面接触应力变化规律和齿根弯曲应力变化规律;利用ANSYS建立斜齿轮副有限元模型,分析齿面接触应力和齿根弯曲应力,将其与理论计算结果比较,验证有限元分析方法的正确性;利用FE-SAFE中的名义应力分析法对斜齿轮副的危险部位进行疲劳寿命预测.     

EHL下矿场用重载齿轮的喷丸及疲劳性能分析

弹流润滑（ＥＨＬ）条件下,石油矿场用大模数重载齿轮的承载能力得到提高,齿面接触疲劳失效与齿根弯曲疲劳断裂则成为其主要的失效形式．喷丸强化是改善齿轮表层种种缺陷的有效而简便的方法,喷丸产生的硬化层残余压应力场和显微组织相变是提高齿轮接触疲劳强度的重要因素．从单齿弯曲疲劳,齿面接触疲劳,接触疲劳裂纹萌生与扩展,表层显微硬度,残余奥氏体情况,表层残余应力及亚组织结构等方面讨论了喷丸对齿轮接触疲劳性能的影响．     

齿根裂纹的闭合效应对齿轮疲劳寿命的影响

考虑裂纹闭合效应对裂纹扩展的影响,将裂纹闭合力转化为裂纹表面之间的恒定牵引力引入齿根裂纹,利用有限元方法对齿根裂纹的扩展过程进行模拟.与不考虑裂纹闭合效应时齿根裂纹扩展过程进行了对比分析,结果表明:考虑裂纹闭合效应时,裂纹扩展过程中的KⅠ的值比不考虑裂纹闭合效应时低;裂纹闭合效应对齿根裂纹扩展路径没有显著影响,但能阻碍裂纹的扩展,有效延长了齿轮的疲劳寿命.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

海南岛地体及其毗邻陆缘晚中生代—新生代古地磁研究和构造演化

本文叙述了对海南岛及其毗邻大陆边缘白垩纪到第四纪地层岩石进行古地磁研究的全部工作过程。通过分析岩石中剩余磁矢量的磁偏角及磁倾角的变化,提出海南岛白垩纪以来经历的构造演化模式如下:早期伴随顺时针旋转而向南迁移,后期伴随逆时针转动并向北运移。联系该地区及邻区的地质、地球物理资料,对海南岛上述的构造地体运动提出以下认识:北部湾内早期有一拉张作用,主要是该作用使湾内地壳显著伸长减薄,形成北部湾盆地。从而导致了海南岛的早期构造运动,而海南岛后期的构造运动则主要是受南海海底扩张的影响。海南地体运动规律的阐明对于了解北部湾油气盆地的形成演化有重要的理论和实际意义。     

Exciton Seebeck in Molecular Systems

Various applications relevant to the exciton dynamics,such as the organic solar cell,the large-area organic light-emitting diodes and the thermoelectricity,are operating under temperature gradient.The potential abnormal behavior of the exicton dynamics driven by the temperature difference may affect the efficiency and performance of the corresponding devices.In the above situations,the exciton dynamics under temperature difference is mixed with     

Achieving Unusual States of Matter Under High Pressure

The elongation method,originally proposed by Imamura was further developed for many years in our group.As a method towards O(N)with high efficiency and high accuracy for any dimensional systems.This treatment designed for one-dimensional(ID)polymers is now available for three-dimensional(3D)systems,but geometry optimization is now possible only for 1D-systems.As an approach toward post-Hartree-Fock,it was also extended to     

《Chinese Science Bulletin》SUBJECT INDEX TO VOLUME 59(2014)

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An on-line scaling method for improving scalability of a database cluster

The explosive growth of the Internet and database applications has driven database to be more scalable and available, and able to support on-line scaling without interrupting service. To support more client's queries without downtime and degrading the response time, more nodes have to be scaled up while the database is running. This paper presents the overview of scalable and available database that satisfies the above characteristics. And we propose a novel on-line scaling method. Our method improves the existing on-line scaling method for fast response time and higher throughputs. Our proposed method reduces unnecessary network use, i.e. , we decrease the number of data copy by reusing the backup data. Also, our on-line scaling operation can be processed parallel by selecting adequate nodes as new node. Our performance study shows that our method results in significant reduction in data copy time.     

An improved R-tree based on childnode''s probability

R-Tree is a good structure for spatial searching. But in this indexing structure,either the sequence of nodes in the same level or sequence of traveling these nodes when queries are made is random. Since the possibility that the object appears in different MBR which have the same parents node is different, if we make the subnode who has the most possibility be traveled first, the time cost will be decreased in most of the cases. In some case, the possibility of a point belong to a rectangle will shows direct proportion with the size of the rectangle. But this conclusion is based on an assumption that the objects are symmetrically distributing in the area and this assumption is not always coming into existence. Now we found a more direct parameter to scale the possibility and made a little change on the structure of R-tree, to increase the possibility of founding the satisfying answer in the front sub trees. We names this structure probability based arranged R-tree (PBAR-tree).     

Integrating GIS Web services based on mediating architecture

The geographic information service is enabled by the advancements in general Web service technology and the focused efforts of the OGC in defining XML-based Web GIS service. Based on these models, this paper addresses the issue of services chaining,the process of combining or pipelining results from several interoperable GIS Web Services to create a customized solution. This paper presents a mediated chaining architecture in which a specific service takes responsibility for performing the process that describes a service chain. We designed the Spatial Information Process Language (SIPL) for dynamic modeling and describing the service chain, also a prototype of the Spatial Information Process Execution Engine (SIPEE) is implemented for executing processes written in SIPL. Discussion of measures to improve the functionality and performance of such system will be included.