新型叶片式电液伺服马达定子过渡曲线的研究

本文针对一种新型叶片式电液伺服马达，讨论了定子过渡曲线在提高马达性能中的作用和设计准则，并从改善曲线的力学特性和动态特性两方面着重探讨了高次曲线在提高马达性能方面所具有的优越性，试验结果证明了高次曲线有利于提高马达的性能。     

基于小波分析的B样条曲线的光顺

小波为曲线的多分辨率表示提供了一个很好的数学方法，它可以很方便的将曲线分解为高分辨率部分和低分辨率部分，分解后的低分辨率部分即为光顺后的曲线。本文先介绍了基于小波的B样条曲线的多分辨率分解，并提出了一种根据光顺容差来控制逼近误差的算法。     

通过挤压或安装钢丝螺套提高压铸铝合金螺纹孔的性能

以AlSi12(Fe)(a)高压压铸件为对象，对于挤压成形螺纹孔，测量螺纹的过扭矩值并输出曲线，测量螺纹的拉脱力值并输出曲线；对于安装钢丝螺套的螺纹孔，测量螺纹的过扭矩值并输出曲线，测量螺纹的拉脱力值并输出曲线。结果表明，挤压成形和安装钢丝螺套均可提高压铸铝合金螺纹的性能。     

活塞异型截面曲线数控加工中的一种逼近方法

针对发动机活塞截面曲线的非标准性，提出了采用最少的圆弧段逼近加工曲线的方法，详细地分析了用圆弧段逼近非标准随圆曲线的过程，并对逼近误差进行分析，满足加工拟合曲线的要求。此种方法计算简单，精度较高。     

曝光曲线计算法及曝光量估算

从射线衰减方程出发，推导了曝光曲线计算方法，并与曲线拟合方法得到的公式进行比较，两者结果相近。再用一台在役X射线探伤仪曝光曲线与计算法所得结果比较，误差较小，印证了该计算方法的可行性。在此基础上，给出现场射线探伤工件厚度变化时曝光量的估算方法。曝光曲线计算法大大减少了常规制作曝光量曲线的工作量，并对现场射线探伤有一定的指导意义。     

过冷奥氏体等温转变曲线数据库的建立

本文用三次样条函数描述钢的过冷奥氏体等温转变曲线，在微机上建立了ＴＴＴ曲线数据库，实现了ＴＴＴ曲线的数据形式存储与动态调用，操作简单，直观，占用计算机存储空间小，并进一步等温转变动力学公式计算出过冷奥氏体等温转变过程中任意转变量曲线，与手册中的曲线吻合得很好。     

湿型砂力学本质特征曲线的研究

用自制的型砂多项性能测试仪，获得了型砂抗压、松弛、抗剪和抗拉测试过程中的应力-应变本质特征曲线，并对它们进行了深入研究，在特征曲线上确定了反映型砂本质性能的8项性能参数，考察了膨润土含量和紧实率对型砂本质特征曲线和型砂性能参数的影响。型砂力学本质特征曲线决定于型砂的内部微观组织结构，反映出型砂的粘弹性和粘塑性等本质性能，体现出型砂在受力变形过程中的微变形本质特征。     

基于MMC准则的双相高强钢HC820/1180DPD+Z断裂失效模型分析

对超高强双相钢HC820/1180DPD+Z的断裂失效模型开展研究，并分析了其微观组织和力学性能。基于MMC断裂失效准则，设计了5种失效试样，采用万能试验机和DIC获得了5种试验的断裂临界塑性应变和力-位移曲线，采用Swift和Hockett-Sherby混合硬化模型拟合并获取了材料的外延硬化曲线，并得到混合模型的最佳加权系数和5种试样的仿真模型，基于仿真模型获得5种应力状态下的应力三轴度和临界塑性应变。最后，基于MMC断裂失效模型拟合获得材料的失效曲线，并采用防撞梁落锤冲击试验与仿真对比分析，验证了断裂失效模型的准确性和精度。结果表明：混合硬化模型对材料硬化曲线的拟合精度较高，加权系数α为0.3时各断裂失效试样的最大力值误差小于3%;未应用断裂失效模型的加速度-时间曲线与试验曲线明显不符，误差较大，而应用MMC断裂失效模型的断裂形貌与试验结果相符，断裂时刻和加速度最大值时的误差分别为2.5%和1.7%,说明模型的精度较高，可以应用于整车碰撞仿真分析。     

先进高强双相钢板破裂失效B-W预测模型

为研究先进高强双相钢不同型号板料的应力三轴度与断裂应变的断裂特性，建立不同应力状态下的应力三轴度与断裂极限应变B-W关系曲线，研究B-W曲线与钢种材料参数的关系，设计了4种先进高强双相钢的拉伸、剪切与胀形断裂试验，求解了应力三轴度和等效塑性应变，采用Hill′48正交各向异性模型和Modified Mohr-Coulomb破裂失效模型对拉伸、剪切与胀形断裂进行了数值模拟，建立了从剪切到双拉范围内的B-W曲线，并通过研究B-W曲线与材料参数的相关性，建立了B-W曲线与材料参数的表达式，以减少标定B-W曲线的困难。通过拉弯试验与仿真验证了所建立模型的准确性和有效性。     

Solid Works环境下的齿轮精确三维造型设计

详细介绍了在Solid works中实现圆柱齿轮精确三维造型的方法和技巧。重点讨论了齿廓曲线的计算方法及其与齿轮加工刀具的关系，分别讨论了齿廓曲线渐开线部分和齿根过渡曲线部分的曲线方程。并编制出了齿廓曲线的计算程序。最后在Solid works中绘制出了直齿圆柱齿轮的精确三维模型。     

Computation of isothermal transformation diagrams of 42CrMo4 steel from dilatometer measurements with continuous cooling

Abstract

To generally predict the mechanical properties of steels following heat treatment, the isothermal time–temperature–transformation (TTT) diagrams must be known. The isothermal kinetics of the phase transformation is influenced by the austenitisation conditions and the deformation processes. Owing to the requirements of the process chain 'integrated heat treatment following hot-forging', the steels are austenitised at a comparatively high temperature and deformed before quenching. The TTT diagrams found in the literature only treat limited austenitisation temperatures and do not generally consider different deformation levels. However, the measurements of the corresponding TTT diagrams are both costly and time consuming. In addition to this, the isothermal transformations of low alloyed steels, which transform very quickly, cannot be measured using those dilatometers which are readily available.¹ In this paper, the TTT diagrams of the 42CrMo4 steel austenitised at 1200^°C and deformed at different levels are computed from the dilatometer measurements with continuous cooling using the methods developed by Buza et al.² and Rios.³     

含铌石墨铸钢的制备与热处理

利用现代铸造技术以及等温球化处理,使球状石墨铸钢的力学性能达到最佳组合,这是一项既经济又有发展前景的成果.这些钢的最大使用潜力与其制造技术和特征技术参数有关,其中最重要的一项是冷却曲线图(TTT曲线).在本试验中,冶炼了3炉不同铌含量(0.0%、0.5% 和1.0%)及其它元素名义成分(质量分数)为1.0%C、2.3%Si、0.4%Mn的石墨铸钢.用热膨胀试验测定了TTT曲线,各组试验用钢的试样都进行了等温淬火.将试样进行了硬度测试及用光镜和扫描电镜进行了组织观察,并进行了拉伸、无缺口试样冲击及磨损试验.结果表明,铌的加入明显改变了TTT曲线, 随着铌含量的增加,使得珠光体转变鼻尖右移,贝氏体转变鼻尖左移.这些合金的抗拉强度都很高,在1700 MPa左右,含1%铌的合金的冲击值为45 J,含0.5%铌合金的为49 J,不含铌的无缺口试样没有被冲断.     

THEORETICAL PREDICTION OF THE KINETICS CURVES OF PEARLITIC TRANSFORMATION IN HYPO-PROEUTECTOID STRUCTURAL STEELS

1.IntroductionDuringthepastseveraldecades,researchonpeaxlitictransformationhasbeenfocusedonpearlitegrowthmechanism.In1938,Mehl[IJsuggestedthatthegrowthrateofpearlitedependsoncarboncontentgradientandcarbondiffusionrate.In1946,basedonthegeneraltheoryofdiffusion,Ze.e.[2]proposedanequationtodescribethepearlitegrowthrate.Soonafterwards,Zenner,BrandtandWagner[3]wereawareofthefactthattheGibbsThomsoncapillarityaffectsboththe7--aand7-Fe3Cboundaxiesandrevisedthekineticsequation.Lateronsin1957,based…     

稀土对0.27C—1Cr钢TTT图的影响

通过测量不同温度下的等温转变曲线,建立了0.27C—1Cr钢的TTT图,研究了稀土对TTT图的影响,结果表明,加入稀土后,奥氏体晶粒细化,晶粒长大速率变慢,Ac_2不变,Ac_3升高;先共析铁素体和贝氏体相变的孕育期缩短,珠光体和贝氏体相变完成所需时间延长,理论计算结果与实验值一致     

Weld metal microstructure prediction from fundamentals of transport phenomena and phase transformation theory

Abstract

Modelling the evolution of weld metal microstructure requires knowledge of cooling rates at various locations in the fusion zone. In the recent past, significant advances have been made in the calculation of transient three-dimensional temperature fields, considering convective heat transfer and fluid flow in the weld pool. However, very little effort has been made to use these accurate cooling rates to understand fusion zone microstructures. The present paper demonstrates the advantages of microstructure calculations using fundamentals of transport phenomena and phase transformation theory. The velocity and temperature fields, the shape and size of the fusion zone, and the cooling rates at different locations were calculated by solution of the equations for conservation of mass, momentum, and energy in three dimensions. The time-temperature transformation (TTT) diagrams were calculated for a series of steels with varying carbon and manganese contents using a phase transformation model. The TTT diagrams and the computed cooling rates were then used to obtain the continuous cooling transformation (CCT) diagrams and the microstructures. The computed volume fractions of the various microstructural constituents were then compared with the experimental results. Good agreement between the computed and the experimental results indicates significant promise for predicting weld microstructure from the fundamental principles of transport phenomena and phase transformation theory.     

钢的过冷奥氏体等温转变图（TTT）的计算机绘制

ＴＴＴ图是制定钢的热处理工艺的重要依据。本软件对所测相变数据进行分段抛物处理，实现了曲线的拟合，用ＢＡＳＩＣ语言设计出具有在半对数坐标系下绘制ＴＴＴ图的软件，该软件再与ＡＵＴＯＣＡＤ联接，在ＣＡＤ绘图软件支持下，可自动绘出精确、实用、美观的ＴＴＴ图。     

THEORETICAL PREDICTION OF PROEUTECTOID FERRITIC TRANSFORMATION IN HYPO-PROEUTECTOID STRUCTRAL STEELS

1.IntroductionInordertodevelopnewtypeofsteels,itisveryimportanttoderiveamuchgeneralruleoftheaustenitedecompositionfromexperimentaldataofknownsteels.Recently)someworkhasmadeencouragingprogressinthisfieldtl--6].Butdifficultiesandsuspicionsarestillobyiousbecausethethermodynamicaldataofmulticomponelltsteelarescatteredanddisordered.PuremathematicalsimulationmaybeusedtocalculateTTTandCCTc...es[4],butithasapremisethatsomespecialpointsofTTTcurvessuchasthenosepointmustbeknowninadvance,whichprevents…     

Influence of Steel Grade on Surface Cooling Rates and Heat Flux during Quenching

Immersion quenching is one of the most widely used processes for achieving martensitic and bainitic steels. The efficiency and quality of quenching are generally tested using standard quench probes for obtaining the cooling curves. A host of parameters like quenchant type, steel grade, bath agitation, section thickness, etc., affect the cooling curves. Cooling curve analyses covered under ASTM standards cannot be used to assess the performance of a quenchant for different grades of steel, as they use a common material for the probe. This article reports the development of equipment, which, in conjunction with mathematical models, can be used for obtaining cooling curves for a specific steel/quenchant combination. The mathematical models couple nonlinear transient inverse heat transfer with phase transformation, resulting in cooling curves specific to the steel grade-quenchant combination. The austenite decomposition models were based on an approach consistent with both the TTT diagram of the steel and Fe-C equilibrium phase diagrams. The TTT diagrams for the specific chemistry of the specimens and the thermophysical properties of the individual phases as functions of temperature were obtained using JMatPro software. Experiments were conducted in the laboratory for computing surface temperature and heat flux at the mid-section of a 25-mm diameter by 100-mm-long cylindrical specimen of two types of steels in two different quenchants. A low alloy steel (EN19) and a plain carbon steel (C45) were used for bringing out the influence of austenite transformation on surface cooling rates and heat flux. Two types of industrial quenchants (i) a mineral oil, and (ii) an aqueous solution of polymer were used. The results showed that the cooling curves, cooling rate curves, and the surface heat flux depended on the steel grade with the quenchant remaining the same.     

45钢淬火三维瞬态温度场与相变的计算机模拟

应用非线性三维瞬态温度场与相变耦合有限元算法,对４５钢淬火冷却过程进行计算机模拟,得到直观的三维图象,计算结果与实测值比较接近。本文采用的ＴＴＴ曲线数值化方法,不仅便于计算机存贮和调用,也便于将现有的ＴＴＴ图进行处理,得出与工件实际成分相对应的ＴＴＴ曲线,从而提高相变计算的精度。议事中讨论了相变量计算值与实测值出现偏差的原因,并指出用Ａｖｒａｍｉ公式计算等温转为能得到合理的结果,但在应用它计算连续