基于剩余强度衰减退化的非线性累积损伤准则及其可靠性定寿

零件的疲劳破坏是一个损伤逐步累积、承载能力逐步下降的过程,其疲劳强度随其承受的载荷和频次而不断衰减.通过研究疲劳过程中材料剩余强度衰减退化的规律,从疲劳损伤的定义出发,把剩余强度退化通过一个衰减系数引入到损伤的定义中,提出考虑材料强度性能退化的非线性累积损伤模型来修正Corten-Dolan理论模型.该模型不但考虑了载荷间的相互作用效应,而且还考虑了载荷加载历史引起的强度退化的影响.同时提出了一种基于剩余强度衰减退化的零件疲劳寿命可靠性分析方法,即在假设剩余强度分布服从对数正态分布下,用零件的剩余疲劳损伤强度计算疲劳可靠度和预测零件疲劳可靠性寿命.通过基于修正Corten-Dolan模型的疲劳寿命预测和算例对比分析,该模型完善了传统Corten-Dolan理论模型的适用范围,提高了预测精度.以恒幅载荷作用下的疲劳可靠性描述为例,通过对比模型分析值和实验值,证实了基于剩余强度衰减退化的疲劳寿命可靠性分析模型的可行性,并可以推广至多级载荷作用下的疲劳可靠性寿命的预测.     

混凝土疲劳损伤累积神经网络模型

针对混凝土疲劳累积损伤的发展受荷载、材料性质等多种因素影响、很难用显式的数学函数表达的难题，基于神经网络方法提出了一个考虑变幅疲劳的级数和加载顺序影响的混凝土疲劳损伤累积模型，采用神经网络技术描述了其与材料性能、荷载应力间复杂的非线性映射关系，准确反映了混凝土疲劳损伤演变的真实过程，并运用离散系统仿真原理构造了退凝土变幅疲劳寿命预测的智能化仿真系统．该系统可用于结构抗疲劳设计和疲劳可靠性分析、有损结构损伤评估及维修决策．     

考虑非线性累积损伤的桥梁疲劳寿命分析

为了准确反映桥梁非线性累积损伤,建立了桥梁非线性累积损伤模型,并分析了模型中主要参数对桥梁疲劳寿命的影响.首先,基于损伤力学理论,引入桥梁非线性累积损伤模型和对应的等效应力幅计算公式.然后,分析模型中主要参数对结构疲劳性能的影响.最后,用桥梁非线性累积损伤模型和Miner模型分析大连某大桥的疲劳性能.研究发现,随着材料参数α的减小,结构损伤增大,并且等效应力幅是影响结构损伤的主要因素.桥梁非线性累积损伤模型能准确反映实际的非线性累积损伤过程,而Miner模型偏保守.     

复杂载荷下轴流压气机叶片疲劳损伤数值研究

为提高叶片的服役寿命,针对压气机叶片疲劳损伤进行了数值研究。在获取叶片表面气动压力及强度分布的基础上,结合非线性连续损伤力学模型,得到叶片多级加载损伤累积方程,提出了开展结构寿命预测和损伤评估的数值计算方法。对轴流压气机叶片在典型工况转速下受离心、气动复杂载荷作用下的应力分布规律和疲劳损伤行为进行了分析。计算结果表明:叶片排气侧4%叶高处有明显的应力集中,容易发生疲劳失效;在叶片疲劳加载过程中,损伤累积速率逐渐增大,加载周期的末期易发生瞬时断裂;考虑载荷顺序对损伤累积行为的影响,和Miner线性损伤模型相比,多级加载损伤模型体现了损伤演化过程的非线性,计算结果更为准确。     

混凝土高频疲劳加速寿命试验

车载循环作用下的混凝土疲劳强度问题越来越受到人们的重视,而针对混凝土高频疲劳性能的研究不是很多,将高频疲劳试验方法引入到岩石类非金属材料的试验中,针对混凝土圆柱试件进行高频疲劳加速寿命试验研究.通过分析疲劳频率变化曲线的规律,解释混凝土高频疲劳的破坏机理,建立混凝土的轴向压缩非线性疲劳损伤累积模型.同时考虑到存活率,得出混凝土疲劳加速寿命失效概率的P-lgS-lgN双对数疲劳方程.     

基于动态剩余S-N曲线的线性疲劳寿命预测模型

为估算结构在变幅载荷下的疲劳寿命,在动态剩余S-N曲线的基础上,结合材料的退化规律,对材料受载过程中的累积疲劳损伤进行了量化,提出了一种预测变幅载荷下线性疲劳损伤预测模型。根据热轧16Mn钢和20Cr2Ni4A标准圆柱齿轮多级载荷下疲劳寿命试验数据,对提出模型的疲劳寿命预测能力进行了验证。结果表明：基于强度退化的线性疲劳寿命预测模型相对传统Miner法则和材料记忆退化累积模型的预测结果更接近试验结果,具有较高的预测精度。     

冻融后预应力混凝土构件疲劳损伤模型

通过7根预应力混凝土梁进行不同冻融循环次数后的疲劳试验,研究冻融环境下构件由于疲劳累积损伤而造成的刚度衰减规律,试验结果表明冻融作用对构件在疲劳荷载下挠度的发展起加剧作用,且随着冻融次数增多作用愈明显.在冻融循环和疲劳荷载的共同作用下,试验梁的剩余刚度在弯曲疲劳过程中呈现三阶段衰减规律,并且在第2阶段近似呈线性衰减,构件发生疲劳破坏时,其剩余刚度衰减至初始刚度的66%左右.根据损伤理论得到试验梁基于刚度衰减的累积损伤值D与循环寿命比n/Nf之间的关系模型,该模型考虑了冻融效应对疲劳累积损伤的影响,可为寒区预应力混凝土梁疲劳寿命预测提供有价值的参考.     

钢筋混凝土桥面板疲劳寿命评估

为确保桥梁使用安全,对混凝土桥面板进行疲劳寿命评估十分迫切.基于疲劳损伤累积理论和混凝土桥面板车轮移动疲劳加载下试验数据,并引入模型相关系数,用来考虑桥面板实际寿命和试验寿命的差异,建立了混凝土桥面板疲劳寿命预测模型,对混凝土桥面板的疲劳寿命进行评估.分析比较了采用英国BS5400、欧洲规范Eurocode和美国AASHTO规范中标准疲劳车评价混凝土桥面板疲劳寿命的差异性,以及车辆超载对桥面板使用寿命的影响.计算结果表明:疲劳标准车技术参数对混凝土桥面板的疲劳寿命影响较大,应研发适用于桥面板疲劳分析的车辆荷载模型;在没有实桥调查数据情况下,建议优先采用BS5400规定的车轮活载频谱值;当车辆超载20％以上时桥面板寿命下降显著,超载40％以上时桥面板寿命将低于10年,因此在桥梁运营中应严格禁止超载20％以上车辆的通行.     

CFL增强RC梁的疲劳累积损伤模型

通过碳纤维薄板(CFL)增强钢筋混凝土(RC)梁的三点弯曲疲劳试验,得到了构件疲劳寿命曲线及其跨中挠度、抗弯刚度的演化规律;采用增强梁的剩余抗弯刚度来定义损伤变量,建立了描述其损伤、断裂过程的疲劳累积损伤模型,并对CFL增强RC梁的疲劳损伤演化历程进行了数值分析.结果表明,文中提出的疲劳累积损伤模型能够准确地描述包括混凝土开裂、CFL与混凝土剥离、钢筋屈服等破坏模式在内的CFL增强RC梁的疲劳损伤、破坏过程.     

基于非线性累积准则的汽轮机转子可靠性定寿

采用可靠性设计方法，对汽轮机转子的非线性损伤累积准则进行了研究。在对一个实例的应用中，分别采用线性和非线性损伤累积准则评价其寿命损耗过程，结果表明，线性损伤累计准则与非线性准则具有较大差别，线性准则更偏于安全，同时，应用非线性准则确定的检修探伤期更加符合实际损伤的发展情况，基于此，提出了一种基于非线性累积准则确定转子疲劳损伤极限的方法，可用于检修期的科学选择。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

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.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

A computer generator for randomly layered structures

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

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

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。     

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.     

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

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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