充型过程中自由表面的数值模拟

对ＳＯＬＡＶＯＦ法进行了改进， 克服了传统的ＳＯＬＡＶＯＦ中的“施体受体”法在处理三维自由表面时易出现计算误差和时间步长小的缺点， 所建立的“三维施受体法”成功地用于充型过程中自由表面的数值模拟。在自由表面压力边界条件中采用新的压力插值函数， 解决了三维情况下因出现相互交叉或相互重叠的自由表面而导致的同一表面单元存在几个插值单元的情形， 用该插值函数不需确定自由表面的法向方向。     

铸件充型过程数值模拟的实验验证及工程应用

采用ＳＯＬＡ－ＶＯＦ法,开发了Ｗｉｎｄｏｗｓ９８／ＮＴ环境下的铸件充型过程数值模拟软件ＦＴ－ＦＬＯＷ,模型中考虑了紊流流动。用标准测试件和阶梯试件对软件进行了验证,实验结果与数值模拟结果比较吻合。目前,铸件充型过程数值模拟软件ＦＴ－ＦＬＯＷ已经在许多厂家的实际生产中得到了应用。     

低压铸造铝合金轮毂充型与凝固模拟

在低压铸造过程温度场及流场实验的基础上,开发了基于ＳＯＬＡＶＯＦ算法的充型与凝固过程数值模拟软件,对７２－４６轮毂铸件进行了模拟分析。结果表明,低压铸造充型过程中降温明显,准确的凝固模拟必须首先考虑充型。针对轮毂铸件的充型特点,开发了简化充型模拟软件。简化模拟得到的初始温度场与采用ＳＯＬＡＶＯＦ算法的模拟结果基本吻合,实现了为后续凝固模拟提供正确的初始温度场的设计目标。     

THE ESTABLISHMENT OF CALCULATION FORMULA FOR CASTING－ROLLING FORCE OF VISCOUS FLUID AND THE INFLUENCE OF TECHNOLOGICAL FACTORS

ＴＨＥＥＳＴＡＢＬＩＳＨＭＥＮＴＯＦＣＡＬＣＵＬＡＴＩＯＮＦＯＲＭＵＬＡＦＯＲＣＡＳＴＩＮＧ－ＲＯＬＬＩＮＧＦＯＲＣＥＯＦＶＩＳＣＯＵＳＦＬＵＩＤＡＮＤＴＨＥＩＮＦＬＵＥＮＣＥＯＦＴＥＣＨＮＯＬＯＧＩＣＡＬＦＡＣＴＯＲＳ￥Ｓｕｎ，Ｂｉｎｙｕ；Ｚｈａｎ...     

HARDENING OF RAPID SOLIDIFICATION Al－Fe－V－Si ALLOY EXPOSED AT ELEVATED TEMPERATURE

ＨＡＲＤＥＮＩＮＧＯＦＲＡＰＩＤＳＯＬＩＤＩＦＩＣＡＴＩＯＮＡｌ－Ｆｅ－Ｖ－ＳｉＡＬＬＯＹＥＸＰＯＳＥＤＡＴＥＬＥＶＡＴＥＤＴＥＭＰＥＲＡＴＵＲＥ￥ＸｕＹｉｈｅｎｇ；ＬｏｎｇＣｈｕｎｇｕａｎｇ；ＬｉＳｏｎｇｒｕｉ；ＬｉＷｅｎｘｉａｎ；ＹａｎｇＳｈｉｂ...     

INFLUENCE OF ADDITIVES ON SLAG－IRON SEPARATION DURING DIRECT REDUCTION OF COAL－BASE HIGH－IRON－CONTENTREDMUD

ＩＮＦＬＵＥＮＣＥＯＦＡＤＤＩＴＩＶＥＳＯＮＳＬＡＧ－ＩＲＯＮＳＥＰＡＲＡＴＩＯＮＤＵＲＩＮＧＤＩＲＥＣＴＲＥＤＵＣＴＩＯＮＯＦＣＯＡＬ－ＢＡＳＥＨＩＧＨ－ＩＲＯＮ－ＣＯＮＴＥＮＴＲＥＤＭＵＤＱｉｕＧｕａｎｚｈｏｕ；ＬｉｕＹｏｎｇｋａｎｇ；Ｊｉａｎｇ...     

TiC－PHASE DIFFUSION LAYER FORMATION IN TITANIUM CLAD STEEL COMPOSITE HAVING AN INTERMEDIATE LAYER OF α－Fe

ＴｉＣ－ＰＨＡＳＥＤＩＦＦＵＳＩＯＮＬＡＹＥＲＦＯＲＭＡＴＩＯＮＩＮＴＩＴＡＮＩＵＭＣＬＡＤＳＴＥＥＬＣＯＭＰＯＳＩＴＥＨＡＶＩＮＧＡＮＩＮＴＥＲＭＥＤＩＡＴＥＬＡＹＥＲＯＦα－ＦｅＸｉａＣｈａｎｇｑｉｎｇ；ＪｉｎＺｈａｎｐｅｎｇ（Ｄｅｐａｒｔｍｅｎ...     

INVESTIGATIONS ON THE FORMATION OF INITIAL CRACKS IN THERMAL BARRIER COATINGS PREPARED BY EB－PVD

ＩＮＶＥＳＴＩＧＡＴＩＯＮＳＯＮＴＨＥＦＯＲＭＡＴＩＯＮＯＦＩＮＩＴＩＡＬＣＲＡＣＫＳＩＮＴＨＥＲＭＡＬＢＡＲＲＩＥＲＣＯＡＴＩＮＧＳＰＲＥＰＡＲＥＤＢＹＥＢ－ＰＶＤＳ．Ｋ．Ｇｏｎｇ;Ｌ．Ｄｅｎｇ;Ｆ．Ｓ．ＬｉｕａｎｄＨ．Ｂ．Ｘｕ（Ｄｅｐａｒｔｍｅｎ...     

薄壁件反重力充型的Simple-守恒标量法数值模拟研究

采用ＳＩＭＰＬＥ法结合Ｖａｎ－Ｌｅｅｒ格式开发了铸件三维弃数值模拟计算程序。用单相ＳＩＭＰＬＥ方程同时求解气液两相流动,用Ｖａｎ－Ｌｅｅｒ格式处理自由表面控制方程用薄壁铸件的反重力充填试验做了验证,并对立方体反重力充填进行了计算。     

一种新型高效节能抗磨剂研制成功

一种新型高效节能抗磨剂研制成功ＳＵＣＣＥＳＳＦＵＬＤＥＶＥＬＯＰＭＥＮＴＯＦＡＮＥＷＨＩＧＨＬＹＥＦＦＥＣＴＩＶＥＥＮＥＲＧＹ－ＳＡＶＩＮＧＷＥＡＲ－ＲＥＳＩＳＴＡＮＴＡＧＥＮＴ成都无缝钢管厂成功地研制出了“托力多”抗磨节能剂。该产品在成都无缝钢管厂...     

基于新S型速度规划的B样条曲线算法研究

为使基于LinuxCNC开放式焊接机器人系统具有精确轨迹运行和加工自由曲线的能力,提出了新型速度控制算法,并基于该新型速度控制算法完成B样条曲线的数学模型及其插补原理分析,提出了3次B样条曲线瞬时速度插补算法,分析了LinuxCNC的Motion层原理,给出了在LinuxCNC系统中实现B样条曲线算法的设计步骤。实验仿真结果表明:B样条插补算法能在LinuxCNC系统中实现自由曲线的轨迹运行,并在预览界面中显示出较好的曲线行走效果。     

飞机叶片焊接修复中的三维测量重构技术

提出一种基于NURBS理论的叶片点云处理和曲面重构的方法.飞机涡轮叶片是结构、气动、强度等多学科优化设计的结果,其外形为复杂的自由参数曲面.用最小二乘法将拓扑后的点云局部曲面拟合对异常点去噪,依据曲率阈值点云分割.将双三次Coons的B-spline形式曲面作为基面,散乱点云无约束曲面逼近,利用优化理论迭代得到曲面控制点从而确定B-spline曲面方程.根据NURBS理论对曲面拼接修剪,复原磨损叶片的三维模型,为后续的焊接修复提供精确三维模型.     

铝合金铸件充型过程及氧化膜卷入的数值模拟

对于直接有限差分法，提出了单元表面无量纲距离、表面充填比率和体积充填比率，以描述铸件充型过程中自由表面的形状，建立了相应的充型过程数学模型，考虑了自由表面形状对动量、质量和能量传输的影响；提出了充型过程自由表面碰撞中表面氧化膜破碎，及其后破碎氧化膜流动的计算模型。对实验铝合金铸件进行了模拟应用，通过实际铸件充型过程的特殊X射线实时观察和记录。及实际铸件的气孔、收缩缺陷分布的检测，对模拟结果进行了验证分析。结果表明：充型过程模拟结果与X射线实时观察结果吻合较好，尤其是自由表面的变化；氧化膜卷入模拟结果与实际铸件气孔、收缩缺陷的分布存在一定的对应关系。     

Atomistic Monte Carlo simulations on the influence of sulphur during high-temperature decarburization of molten iron–carbon alloys

We report a Monte Carlo simulation study of the molten Fe–C–S system with the aim of developing a theoretical understanding of the influence of sulphur during decarburization reactions in Fe–C alloys. Focussing specifically on the role played by free surfaces, computer simulations were based on the hexagonal atomistic model of Fe–C–S system using isotropic atomic interaction parameters; free surfaces were characterized by a missing layer of atoms. Three geometrical configurations, namely a liquid bath, a prismatic block and a spherical droplet, were investigated. Simulations were carried out as a function of melt carbon and sulphur concentration, temperatures and surface/volume ratios of the simulation cell. Sulphur atoms were found to preferentially concentrate in the top few layers, with the second layer showing the highest amounts of sulphur; very little sulphur was observed in the bulk liquid. This trend was observed in all three simulation configurations over a wide carbon/sulphur concentration range and temperatures. Significant levels of iron were observed in the top surface layer. The influence of free surfaces on atomic concentration profiles was found to be a strong function of the surface/volume ratio. The surface segregation of S was more pronounced for small exposed surfaces and was much smaller for liquids with large exposed surfaces. The presence of surface-active sulphur resulted in a major re-distribution of carbon. Carbon tended to concentrate deeper in the bulk, with the surface region being severely depleted of carbon. In addition to several new findings and a better understanding of liquid surfaces, these simulations have helped overcome major limitations of Sain and Belton’s model. Key experimental results on decarburization have been explained within the framework of our simulations. These simulation results have significant implications for surface decarburization reactions and carbon-boil phenomena in smelting technologies.     

Five-axis milling mechanics for complex free form surfaces

Accurate and fast prediction of machining forces is important in high performance cutting of free form surfaces that are commonly used in aerospace, automotive, biomedical and die/mold industries. This paper presents a novel and generalized approach for prediction of cutting forces in five-axis machining of parts with complex free form surfaces. Engagement simulations between cutter and part are performed precisely along the tool path by a recently developed boundary representation method. Moreover, mathematical model for five-axis milling mechanics is developed for any given solid model of parts with complex free form surfaces. Theoretical simulations and experimental validations show that cutting forces are predicted fast and precisely for five-axis machining of complex free form surfaces.     

细论直线的逐点比较法插补

在目前的普通高等教育机电类数控技术课程有关教材中，关于直线的逐点比较法插补原理，只总结出了起点在原点的直线、在采取终点坐标绝对值形式条件下的插补计算方法。本文则归纳出了该类直线在采取终点坐标代数值形式下的插补计算方法，以及起点不在原点的直线和其他坐标面内的直线的逐点比较法插补计算方法。     

Simulation of mold filling and prediction of gas entrapment on practical high pressure die castings

Element parameters including volume filled ratio, surface dimensionless distance, and surface filled ratio for DFDM (direct finite difference method) were proposed to describe shape and location of free surfaces in casting mold filling processes. A mathematical model of the filling process was proposed specially considering the mass, momentum and heat transfer in the vicinity of free surfaces. Furthermore, a method for gas entrapment was established by tracking flow of entrapped gas. The model and method were applied to practical ADC1 high pressure die castings. The gas entrapment prediction was compared with the fraction and maximum size of porosities in the different casting parts. The comparison shows validity of the proposed model and method. The study indicates that final porosities in high pressure die castings are dependent on both gas entrapment during mold filling process and pressure transfer within solidification period.     

基于曲率自适应的自由曲面测量点分布

针对自由曲面测点布置问题,采用曲率自适应形状特征的测点自适应分布。分析自由曲面的数学模型,为自由曲面参数化建模提供数学基础;研究自适应形状特征法,采用曲面形状函数的采样算法,使测点自适应分布;设计曲面,进行实际测点的布置,得到自适应测点分布图,并对测点数据进行CMM检测验证。     

激光深熔焊中匙孔形成过程的动态模拟

为了准确的模拟出激光深熔焊接中匙孔变化的动态过程,根据匙孔内激光的能量吸收机制,采用射线跟踪法产生热源,建立了激光深熔焊接过程中气、液、固三相统一的数学模型,并采用了VOF方法追踪自由液面,模型中考虑了表面张力、热浮力和反冲压力的作用,通过数值计算得到了匙孔变化的动态过程与相应的温度分布.结果表明,匙孔形成的主要驱动力是反冲压力,在加热初期,激光主要用来加热金属基体,随着激光辐照时间的增加,熔池表面温度急剧升高,金属进而汽化,产生匙孔.针对304不锈钢的工艺试验表明计算结果与实际相符合.     

Machining accuracy improvement in five-axis flank milling of ruled surfaces

The aim of this study is to develop a new adjustment method for improving machining accuracy of tool path in five-axis flank milling of ruled surfaces. This method considers interpolation sampling time of the five-axis machine tools controller in NC tool path planning. The actual interpolation position and orientation between G01 commands are estimated with the first differential approximation of Taylor expansion. The tool swept volume is modeled using the envelope surface and compared with the design surface to determine the deviation, which corresponds to the machining error induced by the linear interpolation. We propose a feedrate adjustment rule that automatically controls the tool motion at feedrate-sensitive corners based on a bisection method, thus limiting the maximum machining errors and improving the machining accuracy. Experimental cuts are conducted on different ruled surfaces to verify the effectiveness of the proposed method. The result shows that it can enhance the machining quality in five-axis flank milling in both simulation and practical operation.