ZrC/奥氏体相界面形变诱导铁素体相变的研究进展

介绍了国内外超细晶粒钢的研究现状,阐述了含ZrC颗粒的此类钢在过冷奥氏体形变过程中,ZrC颗粒对形变诱导铁素体相变的热力学条件、动力学关系和铁素体晶粒细化的影响;指出了外加第二相颗粒等增加聚集形变能缺陷的新方法是我国在现有装备轧制能力不足的条件下获得超细晶粒低碳钢中厚板的关键技术,以及今后低碳钢形变诱导铁素体相变晶粒细化的研究方向。     

组织特征对980MPa级先进超高强钢成形性能和拉伸行为的影响

以CP980钢、DP980钢、QP980钢为研究对象，采用单轴拉伸试验并结合数字图像相关技术，研究了组织特征对980 MPa级先进超高强钢单轴拉伸行为以及全局、局部成形性的影响。结果表明：QP980钢由马氏体、铁素体、残余奥氏体组织组成，在均匀变形阶段奥氏体相变产生的相变诱导塑性效应使该钢具有最优的全局成形性，但是新生马氏体相与其他相的硬度差较大，导致其局部成形性最差并形成准解理断裂；DP980钢由铁素体和马氏体组织组成，其强化机制以马氏体硬相强化和铁素体位错强化为主，全局成形性居中，同时因铁素体和马氏体之间具有一定的协调变形能力，其局部成形性较好，断裂形式主要为韧性断裂；CP980钢为铁素体、贝氏体、马氏体的多相组织，各相硬度差小，协调变形能力较强，局部成形性最好，断裂形式为韧性断裂。     

铌微合金钢形变连续冷却过程中的相变

在Thermecmastor-Z型热模拟试验机上对20MnSiNb和20MnSi钢进行了单向压缩试验,用热膨胀技术结合组织观察的方法,建立了它们的静态和动态的连续冷却转变曲线,研究了在连续冷却过程中冷却速率、铌及形变对钢γ→α相变过程的影响规律.结果表明:随着冷却速率的增加,铁素体转变开始温度降低,铁素体晶粒得到细化;20MnSiNb钢中析出的Nb(C,N)促进了γ→α相变,并使铁素体晶粒进一步得到细化;形变对铁素体相变也有促进作用.     

奥氏体晶粒细化的研究

在Gleeble1500热模拟机上以SS400钢为研究对象，用冷加工 回火再结晶和冷加工 a→γ逆相变等工艺，研究了冷变形对马氏体(铁素体)再结晶行为的影响以及奥氏体晶粒细化的方法。结果表明：低温变形对板条马氏体的再结晶行为有一定影响，并且由于低温变形后快速升温的铁素体回复、再结晶与奥氏体(铁素体)相变等相继发生，从而得到比较细小的奥氏体晶粒。     

变温循环相变超细化后00Cr13Ni7Co5Mo4Ti马氏体时效不锈钢的组织与性能

研究了00Cr13Ni7Co5Mo4Ti马氏体时效不锈钢的变温循环相变晶粒超细化工艺及其细晶处理后的组织与力学性能。结果表明:经过变温循环相变处理后,马氏体时效不锈钢的晶粒尺寸由180μm细化至6μm,得到细小的等轴晶粒;马氏体板条被多个小马氏体簇切割成多段而碎化,使马氏体组织进一步细化;与传统高温固溶后时效处理工艺相比,经变温循环相变处理后钢的屈服强度提高170MPa,抗拉强度提高100MPa,伸长率提高了18%,断面收缩率提高13%。     

440MPa级高强IF钢的连续冷却相变规律

利用膨胀仪和热模拟试验机测定了440MPa级高强度IF钢的静态和动态CCT曲线,并对其相变规律进行了分析。结果表明:在静态和动态转变的开始阶段均出现了铁素体组织,随冷速的提高出现了贝氏体铁素体组织,使转变产物晶粒细化;与静态转变相比,动态转变提高了奥氏体向铁素体转变的开始温度,促进了铁素体相变,使转变产物晶粒细化。     

低碳钢临界奥氏体区的变形行为

在Gleeble-3500型热模拟试验机上对Q235钢进行了单向压缩试验，研究了不同温度下低碳钢的变形特征以及形变诱导铁素体的演变行为和在保温过程中的变化。结果表明：降低变形温度有利于低碳钢的组织细化，但变形温度低于Ar3时，得到混晶组织，并使珠光体成务状分布；随着变形的进行，形变诱导铁素体首先在晶界形核，然后在相界上反复形核；铁素体数量随着应变量的增加而增加，但存在一个极限值；应变量较高时，将会发生铁素体的动态回复和再结晶；形变诱导铁素体在变形后的保温过程中发生了逆相变并伴随着铁素体晶粒的粗化。     

ZrC粒子对低碳钢形变诱导相变热力学条件的影响

采用单向压缩热模拟实验,研究了ZrC粒子对低碳钢形变诱导铁素体相变热力学条件的影响。研究结果表明:将适当粒径和体积分数的ZrC粒子作为形变和再结晶核心,能提高相变的开始温度,降低相变的临界变形量,从而提高α-Fe形核率,使铁素体晶粒超细化;ZrC粒子的数量对形核的促进作用存在某一临界值,过量的粒子不利于组织细化。基于相变热力学理论,制定了实验室轧制工艺,获得了铁素体晶粒尺寸达3.9μm的低碳钢中厚板,所得材料的综合性能显著提高。     

形变热处理工艺对低碳微合金管线钢晶粒细化的影响

以管线钢X52为研究对象，在Gleeble1500热模拟机上，进行了奥氏体未再结晶区不同形变速度、形变量和冷却速度对X52的相变行为及显微组织影响的研究。通过光学显微镜、扫描电镜分析可以发现，随变形速率、形变量和冷却速度的增加，晶粒明显变细。同时，低碳钢不同的是在奥氏体未再结晶区扎制时，第二相的析出可以抑制再结晶，并且析出物的存在不仅阻碍位错的运动，而且全造成位错的增殖，因而微合金钢细化昌粒的机理主要有：形变诱导铁素体、铁素体的动态再结晶和第二相的析出抑制晶粒长大使晶粒细化。     

Nb微合金低碳钢表层超细晶中厚板的研制

应用中间坯加速冷却-轧制-轧后加速冷却工艺轧制的10mm表层超细晶(1～5 μm)Nb微合金高强度钢板,超细晶层厚度为0.5～2.0 mm,其屈服强度达到640 MPa,抗拉强度740 MPa,伸长率达到27%,-40℃冲击吸收功大于130 J.利用光学电镜、扫描电镜和透射电镜观察分析组织,得到如下结论:铁素体晶粒超细化的机制是过冷奥氏体应变诱导铁素体相变,先共析和应变诱导的铁素体动态再结晶;强化机制为细晶强化,Nb析出物的弥散析出强化,位错及亚结构强化;在实施中间坯加速冷却前通过再结晶区轧制得到细化的奥氏体晶粒,或未再结晶区轧制获得形变奥氏体晶粒,或在中间坯加速冷却后增大轧制压缩比,和降低轧后加速冷却的终冷温度均有利于获得表层超细晶粒,同时增大整个厚向超细晶粒比例.     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

Quantum Cooperative Robotics and Autonomy

The intersection of Quantum Technologies and Robotics Autonomy is explored in the present paper.The two areas are brought together in establishing an interdisci...     

考虑进油孔有限长滑动轴承油膜力的近似解析解

针对具有进油孔的有限长滑动轴承油膜力求解问题,采用变分原理和分离变量法,求得了有限长滑动轴承油膜压力分布的近似解析表达式。将油膜压力分布的近似解析表达式在油膜存在区域上进行积分,即得到了油膜力。将提出的计算有限长滑动轴承油膜力方法与无限长轴承模型、有限元方法的计算结果进行了比较,发现了提出的方法与有限元方法的计算结果很接近。最后,研究了进油孔位置和进油压力对油膜存在区域、油膜力等的影响,研究结果表明进油孔位置和进油压力对油膜存在区域和油膜力有较大的影响。     

三绕组变压器的双绕组等效建模及在Matpower中的应用

针对实际电网存在着大量的三绕组变压器,但国际上一些著名商业软件,如BPA仿真软件、Matpower这一权威潮流计算开源软件,均只提供双绕组变压器模型,限制了其在具有三绕组变压器的电力系统中的应用的问题,潮流计算是自主开发的电力系统各种应用软件的核心模块,因此依托国际权威开源程序进行二次开发,是一种较好的选择。对Matpower要求的数据格式进行了归纳,对变压器的一般的等值电路及带理想变压器的等值电路和带标幺值的等值电路进行了分析研究,提出了三绕组变压器转换为双绕组等效模型的建模方法,使得原先只适应双绕组变压器的潮流计算软件可以适用于三绕组变压器电网的潮流计算;最后以Matpower软件为例进行了案例计算,并用PSASP仿真软件进行对比验证。研究结果证明,所提出的建模方法是有效的。     

On the Relation of Load to Average Gap in the Contact Between Surfaces with Longitudinal Roughness

A computer simulation model for the contact between longitudinally-oriented rough surfaces has been formulated. This model closely duplicates the actual surf ace contact deformation behavior by taking into account the elastic interactions between the asperities. There were no assumptions made about the shapes, or any deformation behavior of the asperities, except for their obeying the laws of elasticity. The plastic deformations on the high asperity peaks were taken into account by setting a ceiling on their contact pressures at the material hardness value. The simulations used real surface profiles which were digitized from unworn circumferentially ground steel surfaces. Each pair of these profiles was mathematically combined to form an equivalent rough profile pressing against an infinitely rigid flat and having the appropriately adjusted elastic modulus. A total of 28 different pairs of profiles were used in the simulations. Each contacting pair was subjected to 30 different load levels and the local contact pressures and deformations were calculated. The contact simulations yielded some important mathematical relationships between parameters, such as the real area of contact, average gap, and average asperity load through statistical curve fitting. Two analytical functions were generated to relate the average load to average gap and the real area of contact to load.     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Fifth International Summer School on Screw-Theory Based Methods in Robotics

正3-11 September,2014University of Bologna,Bologna,Italy www.summerscrews.org summerscrews2014.ing.unibo.it SUMMER 20SCREWS 14In 2014,our screw-theory school comes to the world's oldest university.In early September,Summer Screws'14 will gather six experts in the application of screw theory in robotics and up to 40 participants at the University of Bologna,Bologna,Italy.The school will teach attendees how to apply existing methods and empower them to develop new ones in their own research.The basic theoretical notions will be introduced in a rigorous manner,emphasizing examples,applications,and exercises.Scholarships are available.     

电站锅炉模糊风险评价方法研究与应用

针对电站锅炉风险等级评价问题,将模糊综合评价技术应用到电站锅炉风险等级评价中。开展了电站锅炉失效影响因素及模糊评价因素的重要程度分析,建立了一套科学合理适于在线评价的电站锅炉风险评价体系,提出了模糊综合评价技术与改进的模糊层次分析法相结合的模糊风险评价方法,利用改进的模糊层次分析法计算了指标体系中各层指标权重。对某一台电站锅炉的实际运行工况影响子因素进行了模糊风险评价,采用模糊合成算子进行模糊综合运算得到电了站锅炉运行工况影响子因素的评价向量。研究结果表明:电站锅炉的运行工况影响子因素的风险评价等级为第6级,失效可能性等级为小,该电站锅炉运行工况良好。     

INDUSTRIAL ENGINEERING AND VISUALISATION-A PRODUCT DEVELOPMENT PERSPECTIVE

Taking the actual project of teaching and researching process for example, the relationship between the industrial engineering and product development is discussed. And use the novel visualization technology to support the industrial engineering and product development. How to use the new computer modeling and simulating technologies to support the product development and industrial engineering, is introduced especially. The support includes both domestic products and industrial systems. The visualization and computer technologies take a very important role in some system or multi-direction modeling, those technologies mentioned above can help the industrial engineers study the effect of design on the whole life circle, including the producing steps. So the engineers can avoid making the wrong decision which may cause bad effects on the whole industrial engineering.     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...