相变诱发塑性钢的流动应力模型

在Eshelby等效夹杂理论和Mori-Tanaka平均场理论的基础上,建立了TRIP(transformation induced plastici-ty)钢单向拉伸代表体单元模型,分析了TRIP钢单向拉伸变形中各组成相的弹塑性变形行为,获得了考虑相变诱发塑性效应的TRIP钢流动应力计算模型,并将计算结果与试验结果进行了比较分析.该模型建立了由相变引起各微观相体积比的变化与TRIP钢宏观流动应力之间的内在联系.计算结果与试验结果的比较表明,该模型正确地预测了TRIP钢的流动应力,将为TRIP钢材料性能的描述及相关的数值仿真技术提供参考.     

耦合TRIP效应的TRIP型多相钢本构模型及其在冲压中的应用

提出了一个耦合TRIP(Transformation Induced Plasticity)效应和考虑材料各向异性的TRIP型多相钢的本构模型.TRIP效应通过与应力状态和塑性应变相关的马氏体动力学方程来描述.把所建立的TRIP钢本构模型在商业有限元软件中进行二次开发,对TRIP型多相钢的应力应变关系和成形性能进行了仿真计算,仿真结果与实验结果符合很好.由于TRIP效应减小了材料的弹性模量,因此在回弹仿真中考虑到弹性模量变化来提高回弹预测的精度,与传统的认为弹性模量在成形过程中保持不变的仿真结果相比,所建立的模型能够很好地说明TRIP钢回弹大的主要原因,为提高TRlP钢的成形性能和精度打下了理论基础.     

不同温度和应变速率下TRIP钢的流动应力

对相变诱发塑性钢TRIP780进行了298,333,363 K温度下且应变速率为10-4,10-2,100,102,103 s-1时的单向拉伸试验.分析了TRIP780钢的流动应力对温度和应变速率的敏感性,并讨论了Johnson-Cook(JC)和Khan-Huang-Liang(KHL)流动应力模型对TRIP780钢的适用性.结果表明:TRIP780钢的流动应力呈现对应变速率的正向敏感性和对温度的负向敏感性,且在高应变速率下流动应力对应变速率的敏感性降低;JC模型对TRIP780钢流动应力拟合在小应变水平下比KHL模型更加准确,而KHL模型在大应变水平下有更高的精度.     

先进高强度汽车钢板的研制

阐述传统相变塑性（transformation induced plasticity,TRIP）钢在成分设计上存在的不足,利用偏聚热力学和动力学设计新型TRIP钢的成分.依据扩散动力学估算TRIP钢经亚临界区等温退火后的最慢冷速,取平衡计算和偏平衡所得T₀温度的平均值作为过时效温度,依据Hillert模型估算贝氏体增碳所需时间,以上述估算所得的参数通过与大量实验室数据对比后均获证实.以热力学探讨TRIP钢热镀锌的条件,进行系列的焊接性能试验,并在上述基础上进行TRIP钢的大生产.以Dumay所提供参数,估算孪晶诱发塑性（twin induced plasticity,TWIP）钢中组元对奥氏体层错能（stacking fault energy,SFE）的影响,以及不同成分TWIP钢的层错能.根据形成六方马氏体所需层错能,设计TWIP钢的成分,经不同处理后获得应变诱发六方马氏体与淬火马氏体,探讨不同方法获得的马氏体对力学性能的影响.所设计钢经处理后,性能最佳者的抗拉强度达1GPa,延伸率为60%,完全满足第三代汽车用钢的要求.     

形变过程中TRIP效应的相变热动态研究

采用拉伸与测温试验同时进行的方法,将应力应变曲线与热能曲线相结合,动态研究热轧TRIP钢拉伸过程中的相变热.研究表明:热轧TRIP钢在拉伸过程中材料增加的热能由部分转变的塑性功和马氏体相变热组成,因此,拉伸过程中实际测得的试样热能高于由塑性功转变的热能.利用平均综合热能损失系数对低速拉伸的TRIP钢的热能进行补充,通过计算与推导,证实了试样在刚进入塑性变形时,一定数量的较不稳定残余奥氏体首先集中发生马氏体相变,随着应变的进一步加大,剩余的较稳定的残余奥氏体根据其稳定情况发生马氏体相变的数量逐渐减少,在试样均匀延伸结束前绝大部分残余奥氏体已转变为马氏体.结合相变热变化可动态描述热轧TRIP钢形变过程中马氏体相变的情况.     

应力状态对TRIP钢残余奥氏体稳定性的影响

通过单向拉伸、平面应变和双向等拉实验研究了宏观应力状态对相变诱发塑性(TRIP)钢中残余奥氏体稳定性的影响.实验中残余奥氏体在不同应变量的体积分数通过X-射线衍射法测量,并引入应力三维度水平来表征不同应力状态.结果表明,不管何种变形模式,TRIP钢中残余奥氏体的体积含量都随塑性应变的增大而减少,而且应力三维度水平越高,TRIP钢的相变速率越快,残余奥氏体的力学稳定性越差.基于此,给出了能够表征不同应力状态的应变诱发马氏体相变动力学方程.     

低碳含硅TRIP钢断裂机理的研究

对试验用低碳含硅TRIP钢断裂机制进行静、动态观察研究,并用扫描电镜定性测量了其中组织颗粒的化学成分.实验表明:应变时等轴铁素体(F)内部产生与拉应力方向呈45°滑移带,随着应力加大,形成按一定取向扩展的微孔,微孔逐渐贯通形成裂纹.裂纹遇到硬质相贝氏体(B)时沿其边缘行走;当遇到残余奥氏体(RA)时,产生的相变诱发塑性松弛了集中应力,导致裂纹钝化、扭折.试验用TRIP钢断口花样为韧窝花样,属塑性断裂.     

无硅TRIP钢力学性能的研究

无硅TRIP钢采用临界区加热等温淬火热处理,获得铁素体,贝氏体及大量稳定残余奥氏体的三相组织·通过对其显微组织观察,断口形貌分析,与高硅TRIP钢力学性能的相互比较,探讨了无硅TRIP钢相变诱发塑性的行为·结果表明:无硅TRIP钢在拉伸变形过程中,应变诱导相变,相变诱发塑性;其拉伸断口形貌呈韧性断口特征;经790℃加热在400℃等温5min时,抗拉强度达到754MPa,延伸率达到36%,综合性能(强塑积)达到27144MPa%的最高值·     

两相区退火温度对高铝低硅TRIP 钢组织性能的影响

对高铝低硅TRIP钢进行两相区退火,通过分析退火后实验钢的微观结构和力学性能,建立了加工硬化指数与相组成的关系,探讨了残余奥氏体稳定性对力学性能的影响.结果表明,随着两相区退火温度的升高,实验钢中贝氏体含量逐渐降低,残余奥氏体含量先增大后降低,并在930℃退火时达到最大.随着两相区退火温度的升高,实验钢的抗拉强度逐渐降低,延伸率先增大后降低,930℃退火时抗拉强度为665MPa,延伸率达到最大,为30%,强塑积约为20GPa·%.EBSD统计和拉伸试验的结果表明,两相区退火温度为930℃时,残余奥氏体稳定性适中,从而在拉伸过程中不断地提供加工硬化,推迟颈缩的发生,大幅度提高塑性.     

低碳Si-Mn系TRIP钢的动态拉伸性能

在气动式间接杆杆型冲击拉伸实验机上对工业生产的两种低碳Si-Mn系TRIP钢不同应变率下的高速冲击拉伸性能进行了研究,并和静态拉伸性能进行了比较.结果表明,两种钢的室温拉伸性能随应变率变化具有相同趋势,但动态下的应变率敏感性比静态下的要高得多.由于TRIP钢组织中残余奥氏体的变形诱发向马氏体的转变显著改善了材料的塑性.     

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.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

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.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

橡胶颗粒沥青混合料低温抗裂性试验研究

以AC-13级配为基础,将橡胶颗粒代替部分集料掺入混合料中,以低温弯曲试验为评价方法对不同橡胶颗粒掺量下沥青混合料的低温抗裂性进行研究,并引入应变能密度值对混合料的低温抗裂性进行综合评价.试验结果表明:橡胶颗粒沥青混合料试件的破坏微应变均超过2 300,满足冬寒区的技术指标;无论是否掺加橡胶颗粒,随着温度的下降,沥青混合料破坏时的最大弯拉强度增大,弯拉应变降低,劲度模量增大;弯曲应变能密度在胶粒掺量为1%左右时具有较大的弯曲应变能密度值,此时橡胶颗粒沥青混合料具有较好的低温抗裂性.     

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。     

Quantitative trait loci （QTLs） for quality traits related to protein and starch in wheat

Quality traits in wheat （Triticum aestirum L.） were studied by quantitative trait locus （QTL） analysis in a recombinant inbred line （RIL） population, a set of 131 lines derived from Chuan 35050 × Shannong 483 cross （ChSh）. Grains from RILs were assayed for 21 quality traits related to protein and starch. A total of 35 putative QTLs for 19 traits with a single QTL explaining 7.99-40.52% of phenotypic variations were detected on 10 chromosomes, 1D, 2A, 2D, 3B, 3D, 5A, 6A, 6B, 6D, and 7B. The additive effects of 30 QTLs were positive, contributed by Chuan 35050, the remaining 5 QTLs were negative with the additive effect contributed by Shannong 483. For protein traits, 15 QTLs were obtained and most of them were located on chromosomes 1 D, 3B and 6D, while 20 QTLs for starch traits were detected and most of them were located on chromosomes 3D, 6B and 7B. Only 7 QTLs for protein and starch traits were co-located in three regions on chromosomes 1D, 2A and 2D. These protein and starch trait QTLs showed a distinct distribution pattern in certain regions and chromosomes. Twenty-two QTLs were clustered in 6 regions of 5 chromosomes. Two QTL clusters for protein traits were located on chromosomes 1D and 3B, respectively, three clusters for starch traits on chromosomes 3D, 6B and 7B, and one cluster including protein and starch traits on chromosome 1D.     

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…