挤压模具型腔轮廊曲线优化拟合分析

采用三次样条函数插值和Bezier曲线拟合两种方法来完成挤压模具型腔轮廓形状的优化设计 ,以挤压表面载荷沿凹模型腔轮廓表面均匀分布来提高模具寿命为优化目标 ,运用刚塑性有限元分析和修正的序列二次规划算法相结合的方法 ,获得了各自优化了的凹模型腔轮廓曲线。通过有限元软件验证了优化结果的有效性和可行性。将这些方法应用于气门及其他类似零件的生产 ,证明了优化的凹模型腔轮廓曲线对提高模具使用寿命有显著效果     

A201铝合金针孔形成机制的探讨

本研究的目的为藉由完整的试验,找出铝合金中针孔与铝合金凝固期间热参数之间的关系,进而于铸造实际处理时,可为铸造方案设计及金属凝固提供参考。A201铝合金有127℃的凝固范围,适合作为研究对象;经由有系统的改变冒口大小,及平板铸件的长度及厚度,并浇注于两种不同的砂型中,通过变化铝合金凝固时的各种热参数,例如:局部凝固时间、冷却速率、液相前进速度及热梯度等,经计算针孔量,可得出热参数与针孔量间的关系。试验结果显示,A201铝合金的针孔量减少与补充参数值G/VSt1.10增大有一定的关系。     

UBET-based numerical modeling of bulk deformation processes

The paper summarizes the development of numerical procedures for modeling bulk deformation process and preform designing techniques based on the upper bound elemental technique (UBET). UBET has a unique place where an approximate, but faster solution is needed for decision making. In designing and optimizing multistage forging and profile ring-rolling processes, an approximate solution can be used to identify the most influential process parameters. Once an optimum combination of process conditions are determined, computationally intensive, but more accurate finite element analysis can be used to verify and refine results. In this paper, UBET procedures for closed-die forging and profile ring rolling are high-lighted. Experimental investigations are used to validate the model predictions. Also, the UBET-based preform design tool is presented as a process and die design tool for multistage forging processes. Application of these techniques is presented with evidence of effective material usage and extended overall die-life.     

KBE技术在铝型材挤压模具设计中的应用

将KBE技术应用于铝型材挤压模具设计中，通过充分利用多来源的领域知识对铝型材模具设计提供最大限度支持，提高工程决策有效性。本文介绍了铝型材挤压模具KBE原型系统框架及其关键技术。     

填料粒子成型对泡沫铝合金孔结构的影响

在实验的基础上 ,绘制出填料粒子成型时的体积与泡沫铝合金的孔隙率相对应的变化曲线 ,并应用力学的基本原理对泡沫铝合金孔结构的成形机理进行了研究。确定填料粒子成型时的体积变化应在 0 %～ 12 %之间 (此时泡沫铝合金的孔隙率应在 41.6 %～ 47.6 %之间 ) ,才能稳定填料粒子尺寸 ,从而更好地控制泡沫铝合金的孔径尺寸 ,提高成型质量 ,稳定泡沫铝合金的使用性能。     

Ultrasonic technique for measuring porosity of plasma-sprayed alumina coatings

Porosity is an important factor in plasma-sprayed coatings, especially ceramic coatings. Excessive poros-ity can adversely affect the performance of the coated component in various ways. An ultrasonic nonde-structive measurement technique has been developed to measure porosity in plasma-sprayed alumina coatings. The technique is generic and can be extended to other ceramic coating systems. To test the tech-nique, freestanding alumina coatings with varying levels of porosity were fabricated via plasma spray. Samples with varying porosity, obtained through innovative fabrication techniques, were used to gener-ate a calibration curve. The ultrasonic velocity in the low-frequency range was found to be dependent on the density of freestanding coatings (measured via Archimedian techniques). This dependence is the basis of the development of a technique to measure the density of coatings.     

316不锈钢藕状多孔结构的选区激光烧结制备

研究了一种新型的制备金属藕状多孔结构技术——选区激光烧结，着重说明该技术的基本原理和工艺过程，并利用此制备技术成功获得了藕状多孔试样。利用SEM分析了316不锈钢藕状多孔试样的微观孔隙特征，并测定其孔隙率，结果表明其孔径大小分布均匀（2-4μm），平均孔隙率约为60％，孔隙贯通性良好；初步探讨了选区激光烧结制备316不锈钢藕状多孔结构的成形机制。     

Oxidation behavior of 2.25Cr-1Mo steel with prior tempering at different temperatures

The oxidation behavior of a normalized 2.25Cr-1Mo steel tempered previously for 10 hr at different temperatures between 873 and 1023 K has been studied up to a maximum duration of 1000 hr in air at 773–973 K. The oxidation resistance of the steel was found to decrease significantly with the temperature of tempering. Tempering of this steel is reported to cause microstructural changes involving precipitation of Cr as carbides and a decrease in the effective (free) Cr contents, that could influence the oxidation resistance of the Cr-containing alloys. Relative compositions across the thickness of the oxide scales, as analyzed by SEM/EDX and SIMS, suggest that a less Cr-rich (and less protective) and thicker scale on the steel formed because previous tempering caused extensive depletion of free Cr.     

热连轧机工作辊热辊形仿真研究

采用差分法建立了轧辊二维瞬态温度场及热辊形的预报模型 ,可用于实际生产的在线热辊形预报 ;利用实际生产参数模拟轧制和空冷过程中的工作辊热辊形 ,计算结果与实测值相符 ;就不同条件下工作辊热变形规律进行了分析 ,对热轧生产的工艺安排、组织和热磨辊具有实际意义     

齿轮箱体铸造工艺优化

新型齿轮箱体铸件形状特殊,在箱体铸件局部存在多壁交叉形成的几何热节,初次开发时在几何热节产生缩孔和分散的缩松缺陷。通过分析缺陷形成原因,提出可行性工艺方案,优化铸造工艺,增设成型冷铁加强局部热节凝固时散热,从而消除铸造收缩缺陷,进行渗透检测和探伤检测达到客户技术要求,铸件实现批量生产。