高强钢动态力学性能本构模型研究（英文）

为了研究高强钢材料在动态加载过程中的力学响应,采用分离式霍普金森压杆对材料进行了不同应变率(3000到12000s-1)和不同温度(20℃到800℃)单轴压缩实验.实验结果表明:高强钢的动态力学行为受应变率和温度的强烈影响.流动应力随着应变率的升高而增加,随着温度的升高而降低.提出了一个经验型本构模型来描述材料的加工硬化和温度软化行为.该本构模型预测的应力——应变曲线与实验结构较好吻合,表明该本构模型可进一步用于高强钢动态变形过程的数值模拟研究.     

40Cr钢的塑性流动应力特征及本构关系

为了研究高速冷滚打过程中工件材料40Cr钢的动态力学特性,利用分离式Hopkinson压杆试验装置对40Cr钢进行了压缩试验,获得40Cr钢在不同应变率(600～5 000 s-1)和不同温度(20～400℃)条件下的应力-应变情况。试验结果表明:40Cr钢对应变率呈现出一定的敏感性和应变率强化效应,塑性变形过程中产生的绝热升温对材料具有热软化作用。基于位错动力学理论,通过试验数据,建立了40Cr钢的动态本构模型。模型计算结果和试验结果对比表明:该模型可以较好地预测40Cr钢在不同应变率和温度条件下的塑性流动应力。     

基于逆向拟合法的H13钢J-C本构修正模型

为了简化材料J-C本构模型的建立过程,提出一种基于自定义函数确定本构模型参数的逆向拟合法;通过准静态拉伸实验和霍普金森压杆实验获得H13钢在应变率为1～15 000 s-1,温度为298～1 073 K条件下的真应力-真应变曲线;在总结不同的H13钢J-C本构模型并确定各材料参数范围的基础上,利用J-C本构函数对真应力-真应变曲线进行自定义函数逆向拟合,从而获得H13钢J-C本构模型在不同条件下的材料参数,并进一步建立材料参数关于温度和应变率的关系函数,确定H13钢在大应变率和高温条件下的J-C本构模型。研究结果表明:本文建立的修正型J-C本构模型能够真实地反映H13钢的流变行为。     

应变率在3×10~3S~(-1)范围内LC_(4CS)铝合金的动力学性态

借助于SHPB和SHTB实验技术,在环境温度-50℃～+200℃和应变率低于3×10~3s~(-1)条件下,对穿甲弹用弹托材料LC_(4cs)铝合金的动态力学行为进行了实验测试分析,给出了材料在不同温度、不同应变率下的应力—应变曲线,确立了其本构关系,并利用自己编制的OEff-1D有限差分程序对该本构关系应用的可靠性进行了数值模拟检验,结果表明它能令人满意地再现该材料的动力学行为。     

300 M高强钢高温流变行为及本构方程

通过Gleeble 3500高温热模拟压缩实验,研究300M高强钢在变形温度900~1 150℃、应变速率0.01~10 s-1条件下变形温度和应变速率对材料流动应力的影响规律,建立高温热变形材料本构方程。研究结果表明:变形温度和应变速率对300M钢材料流变应力都有显著的影响,随着变形温度的降低和应变速率的增加,材料流动应力增加;建立了材料常数α,n,ln A和激活能Q与真应变之间的非线性四项式函数关系;所建立材料本构方程预测值与实验值具有较好的一致性,说明该本构方程能够准确地描述300M钢热变形条件下的材料流变行为。     

单轴冲击载荷下基于塑性细观力学的冻土本构模型研究

随着寒区工程建设成为中国基础建设的又一大热点,对于冻土冲击动态力学性能及其本构模型的研究已显得十分必要。不同冻结温度的冻土试样通过采用分离式霍普金森压杆(SHPB)进行了不同应变率下的单轴冲击压缩实验。实验结果表明:冻土的弹性模量随着冻结温度的降低而升高,没有明显的率相关性;冻土的强度随着冻结温度的下降和加载应变率的升高而增大。基于实验结果,采用平均化方法推导了与冻结温度相关的冻土等效弹性常数的表达式。同时,采用基体各向同性化的切线模量法建立了冻土的动态塑性细观力学模型。进而,引入与冻结温度和加载应变率相关的连续损伤演化模型构建了冻土的冲击动态本构模型。相应的模拟结果表明,该模型能够很好地描述冻土的动态力学行为。     

花键冷敲成形本构关系研究

花键冷敲成形归结于材料的动态塑性变形过程,为了研究该过程材料动态响应特性,对三种常用冲击载荷下材料本构模型进行理论解析,并根据花键冷敲成形工艺参数对JC本构模型进行修正改进;通过三种本构模型在不同应变率和温度条件下的应力情况,使用流动应力预测值和实验值之差来评估模型误差值。最终结合成形过程物理机制、工艺参数和误差对比,结果表明:在大范围应变率和温度条件下,各本构模型均有其在一定范围内的适用性和精度,但对于花键成形应变率和温度范围内,PTW模型的误差率最小,能够较好预测金属流动应力。     

热镀锌双相钢DP590力学特性及其本构模型

通过单轴拉伸试验及液压扩胀试验,分析了热镀锌双相钢DP590准静态条件下力学特性及大应变力学行为,同时利用高速电液伺服试验机及分离式Hopkinson拉杆试验机测试了该材料中高应变率下的动态力学特性.试验数据表明,DP590呈现微弱的各向异性,同时其动态等效应力应变曲线簇具有随应变增加而渐进收敛的特性.在此基础上提出了一个基于YLD2003各向异性屈服准则的混合流动硬化收敛型黏塑性本构模型,并提供了模型参数的识别方法.利用该本构模型对一薄壁管梁结构的轴向冲击试验过程进行了数值模拟,结果表明,采用新本构的仿真模型可以准确模拟试验结果,因而该本构更适用于工程精细仿真的需要.     

SHPB实验及其在合金材料中的应用研究

钛、铝合金材料在航空航天等工程领域中得到了广泛应用,对其动态冲击力学性能的研究需借助分离式Hopkinson压杆(split Hopkinson pressure bar,SHPB)实验完成。比较并分析了SHPB实验装置及其在该两种合金材料研究上的应用,研究了影响SHPB实验结果的因素,如弥散效应、均匀性问题、惯性效应及端面摩擦效应等。通过对钛合金、铝合金材料冲击动态力学性能及其本构模型进行研究发现:钛合金和铝合金材料的流动应力和屈服强度往往会随着应变率的升高而升高,随温度的升高而降低。对钛合金和铝合金材料的冲击动态力学性能进行了比较,Johnson-Cook本构模型可以合理描述两种材料的冲击动态力学行为。     

Fe-6.5％Si钢中温变形过程本构方程

利用Gleeble 3500开展了Fe-6.5%Si(质量分数)钢在变形温度300,400,500,600℃及应变速率为0.05,0.5,5s^-1条件下的单道次压缩实验.在初始均匀塑性变形阶段,加工硬化作用使流动应力迅速增加,随着变形继续动态软化机制启动,流动应力增加量减弱.随着温度升高和应变速率降低,应变硬化指数减小.提出了通过变形温度、应变速率描述应变硬化指数的方法构建Fe-6.5%Si钢中温变形过程本构方程.构建的本构方程对不同变形条件的应力预测结果和实测值吻合良好,平均相对误差约为5.35%,预测精度较高.     

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.     

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.     

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.     

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.     

A computer generator for randomly layered structures

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

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.     

Jane Eyre——A Feminist In The 19th Century

In the 19th century the society was controlled by men, and women were just appendants of them, they had not any rights and freedom. But Jane was an exception, she showed some characteristics of early feminist. Jane showed her characteristics of feminism in three aspects: rebellion, equality, and independence. These characteristics were helpful to her success, and feminism is the only way out for women of that time.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-