模具渐开线齿形的电火花线切割加工

电火花线切割加工模具或齿轮渐开线齿廓之前,需先作曲线拟合,以便计算线切割编程数据.文章给出高精度的渐开线齿廓线曲线二点拟合法以及电火花线切割加工模具齿形和内齿精度简易检测方法.该方法对各种模具和圆柱齿轮的渐开线齿形加工均适用.     

已知型值点一阶,二阶导数的曲线拟合方法—五次多项式法

本文提出用五次多项式函数来拟合已知型值点一阶、二阶导数的曲线方法，这对某些曲线零件的廓形设计具有较大实际意义。五次多项式函数具有构造简单、系数求取方便的优点，并可根据实际需要对型值点及其一阶、二阶导数进行方便的调整，与一般常用的三次样条曲线拟合方法相比，本方法具有更大的灵活性。     

汽轮机静叶片内背弧型线优化设计与研究

汽轮机静叶片装配内背弧型面的加工是汽轮机静叶片关键工序之一.针对汽轮机静叶片内背弧型面的型线结构与加工特点,应用三次样条曲线、多项式插值曲线拟合内背孤型线,以内背弧型线的原始数据为基础,进行数值计算得出拟合后的型值点,从而得出拟合型线.通过拟合误差分析结果表明:相对于模糊的NURBS曲线形式,拟合后的型线确定为三次样条曲线(C3型),且具有较小的轮廓误差,保证了设计时零件的精度及表面粗糙要求,同时型线具有良好的光滑性、连续性.     

一种改进B样条曲线拟合算法研究

曲线拟合技术广泛应用于图像处理、逆向工程等领域。工程上常用的B样条曲线拟合方法具有局部性、连续性等优点,但拟合所得曲线不通过型值点,拟合精度较低;曲线插值算法所得曲线通过型值点,但缺乏局部性,且需要补充端点条件。为了改进B样条曲线拟合算法不能满足精度要求,曲线插值算法不易于实时局部修改的缺点,提出一种改进B样条曲线拟合算法。该算法结合B样条曲线拟合和曲线插值的优点,通过增加型值点使得曲线通过所有的原始型值点,且保证曲线具有局部性。经实例验证,该算法原理正确,技术可行,且具有较高的拟合精度。     

曲线曲面的B3样条拟合及其实现

在计算机辅助几何设计(CAGD)中,曲线、曲面拟合多采用多项式作为基函数,本文通过几种曲线、曲面生成算法分析,提出了一种B3样条的拟合方法.它具有B样条的主要优点,耳通过所有型值点,这一方法适用于自由曲线、曲面的设计.还结合拱坝体形设计实例说明了用此方法进行造型设计的技术.     

单螺杆泵定子型腔模芯靠模曲线的设计

本文主要阐述螺杆泵定子型腔模芯靠模曲线的计算机辅助设计，讨论定子腔模芯靠模曲线型值点的计算方法；解决橡胶的收缩率引起的误差；消除在仿形切削时产生的误差，并采用圆弧样条曲线拟合计算的型值点，保证一阶导数连续，加工的型腔曲面光顺。     

砂轮修整对成形磨齿齿廓偏差的补偿

为了提高成形磨齿齿轮的精度,研究了一种通过修整砂轮廓形来补偿齿廓偏差的方法。首先说明了研究此方法的必要性,然后介绍了此方法的原理:用三次B样条曲线对齿形测量数据点进行拟合,求出拟合后的曲线方程,并在此基础上建立了真实的齿面方程求解模型,提出了针对齿廓偏差补偿的用于计算砂轮截形的假想齿面方程。基于同一个齿轮不同齿的测量数据,可得到不同的砂轮截形,为此将所有的砂轮截形组成线族,对线族中的离散点采用最小二乘法进行拟合,拟合之后的砂轮截形为补偿齿廓偏差的最佳截形。最后,通过实验试磨分析,加工出的齿轮经测量齿廓偏差由5级精度提高到了3级精度,并且同时补偿了齿廓倾斜偏差与齿廓形状偏差。     

三坐标测量机在凸轮快速测量中的应用

基于三坐标测量机的边界扫描方式,提出一种在工件型面上直接采点的凸轮快速测量方法。基于点方法生成B-样条曲线函数拟合测头中心轨迹,构造偏置曲线函数,对球形测头进行半径补偿,并利用UG／OPEN GRIP软件生成凸轮的实际轮廓线和升程曲线。试验结果表明,该方法能高效、准确、方便地实现凸轮检测。     

用双圆弧法作列表曲线的编程数据处理

数控加工编程时，双列表曲线数据采用分段求切线法进行双圆弧拟合处理，可获得一阶导数连续，型值点处不产生尖角的圆滑廓线。     

弧齿锥齿轮仿真加工齿面的NURBS重构及优化方法

针对仿真加工输出的弧齿锥齿轮模型齿面精度较低的缺陷,结合非均匀有理B样条(NURBS)方法在CAD/CAM中的优势和特点,提出NURBS齿面重构和优化的方法。首先,基于仿真加工齿面形状的分析,提取初始型值点并对其进行优化选取,将由工作齿廓、过渡圆角、齿根组成的端面齿廓曲线作为v线,齿面的过渡圆角线作为u线,分别进行其曲线的NURBS拟合。然后,基于拟合的基本曲线,采用蒙面法进行了弧齿锥齿轮的NURBS齿面重构。最后,以重构齿面为基面提出了以牛顿迭代与最小二乘法为主的多种齿面优化方案,以完成齿面的精确拟合。结合相关算例的齿面精度对比分析,表明提出的重构及优化方法具有良好的实用性。     

基于样条曲面描述的大变形有限元数值模拟关键技术探索

模具型腔描述、锻件有限元网格划分、界面接触约束是制约三维复杂体成形有限元数值模拟技术应用的3个关键性问题。以3次B样条曲面描述为基础,对三维复杂工具表面离散、变形体三维网格自动划分、变形体边界节点与模具接触状态判断的一体化技术进行了研究。利用B样条曲面的直观性、局部性、通用性、造型灵活性等特点,构造复杂模具型腔曲面及变形体边界,提出三维网格样条生成法、改进的分块样条生成法及接触判断的区域层次搜索技术。     

An experimental study of contact pressure distribution in panel stamping operations

This paper presents an analysis of the dynamic contact pressure distribution at the sheet metal-tooling interface in normal and defective panel stamping operations. Specifically, the stamping of a 1.27?×?20?×?15?cm rectangular aluminum alloy panel has been simulated using finite-element modeling methods. The modeling results are leveraged to determine the forces acting on sensors embedded in the die structure. Based on these results, a customized stamping test bed has been designed, which incorporates an array of force sensors embedded into the stamping die to enable online measurement of the forces in the die. The force measurements are processed by the thin plate spline numeric surface interpolation method to evaluate a continuous contact pressure distribution map of the die cavity. The pressure distribution in the die cavity in normal and defective scenarios has been presented along with a suggested volume thresholding method for automated defect detection. By leveraging the numeric surface generation method to analyze experimental data, the present study establishes the basis for intelligent tooling and in-process monitoring for improved observability in sheet metal stamping.     

扁挤压筒过渡曲面建模

为改善铝型材挤压过程中金属流动状况,通过引入流函数法建立基于流曲线的扁挤压筒型腔到模口之间过渡曲面的边界条件;同时采用保角映射方法,描述扁挤压筒型腔及模口处轮廓分别向单位圆的映射关系,构造过渡曲面入口和出口复杂图形的解析函数,解决了复杂三维模型向准三维对称模型的转换问题。两者结合得到过渡曲面上各点的流线方程,完成对过渡曲面的数学描述。为验证新构建曲面的合理性,对一矩形壁板成形过程进行模拟。结果表明：流线型过渡曲面有利于金属流动,并且有利于降低型腔面上的法向压力,可减少磨损、提高模具寿命。     

一种基于离散数据的自由曲面建模方法

提出一种基于离散数据的自由曲面建模方法。该算法采用平行网格构造曲面，利用三次样条函数和参数样条对列表点进行行列两个方面的插补，采用局部回弹法进行曲线光顺，从而构造出适于数控加工的网格曲面，由于采用参数样条进行插补，可保证插值曲线通过所有型值点，曲线具有一、二阶导数连续的性质，可保证曲线的整体连续平滑。该方法的特点是方便了直角坐标下平行行切加工的数控编程。     

不可展开空间曲面模具表面精密加工方法研究

弧面凸轮轮廓为复杂而不可展开的空间曲面,在毛坯等温挤压过程中,为使材料顺利地充满凹模型腔以及成形后脱模顺利,通过在弧面凸轮曲面上加盖敷料及在各连接处采取圆弧过渡,以制得高精度的近似净形零件毛坯件;并通过对弧面凸轮HALF凹模型腔表面加工方法的研究,以提高等温挤压工艺模具在弧面凸轮毛坯成形的使用寿命.     

锉刀柄部六方锥形体辊锻模具型面的3D共轭造型

基于空间啮合原理建立了锉刀柄部六方锥形体辊锻模型腔表面方程 ,推导了型腔表面端、轴截形的数学表达式 ,并在计算实例中计算了数控加工模具型腔所需的截形坐标点数据     

A study on precision forging of spur gear forms and spline by the upper bound method

Precision forging is an important manufacturing procedure of spline and spur gear forms. It has advantages of improved strength, good tolerance, saving billet material, dispensing with the cutting, etc. In this paper, a mathematical model using an upper bound method is proposed for forging of spur gear forms and spline to investigate the plastic deformation behavior of billet within the die cavity. The material of solid billet was assumed as rigid–plastic and the shape of the tooth profile was accounted for the mathematical modeling of the kinematically admissible velocity field assumed for the plastic zone. The non-uniform velocity was employed for simulating the inhomogeneous deformation and the effect of barreling during the forging. Using the present model, various effects of forming parameter such as the friction factor, reduction, number of teeth, etc. upon the non-dimensional forging pressure, forging force and barreling of the spur gear forms and spline were analyzed systematically and the results compared with those of other researcher's analytical and experimental work. It is shown that the present modeling of the process improves knowledge of the process design performance for the precision forging of spur gear form and spline.     

基于三次样条函数与c++ Builder的盘型凸轮反求设计

依据三次样条函数和曲线拟合理论,采用c++Builder语言开发了盘形凸轮轮廓CAD系统。该系统适用于凸轮反求设计,其结果可自动生成AutoCAD存档文件,并可直接提供数控加工所需参数。实际应用证明,该系统为凸轮设计和制造提供了有效、快捷和高精度的手段。     

冲压成形中凹模入口角曲线优化

冲压成形时,凹模入口角的形状对模具与工件之间的摩擦、冲压件表面质量以及模具使用寿命均有着重要的影响。为能获得最优的凹模入口角,提出了采用三次样条曲线作为凹模入口角曲线的新工艺方法。以板料与凹模入口角处的摩擦力做功为研究对象,基于响应面和试验设计方法,在满足成形质量前提下,优化凹模入口角曲线。结果表明:采用优化后的三次样条曲线进行凹模入口角设计,可以减小凹模入口角处的摩擦力做功,且摩擦力做功分布较均匀;可延长模具使用寿命,并可以提高工件表面质量。     

Analysis of simulated scanning of atomic-scale silicon surface by atomic force microscopy

This study constructs a contact-mode atomic force microscopy (AFM) simulation measurement model with constant force mode to simulate and analyze the outline scanning measurement by AFM. The simulation method is that when the probe passes the surface of sample, the action force of the atom of sample received by the atom of the probe can be calculated by using Morse potential. Through calculation, the equivalent force on the cantilever of probe can be acquired. By using the deflection angle equation for the cantilever of probe developed and inferred by this study, the deflection angle of receiving action force can be calculated. On the measurement point, as the deflection angle reaches a fixed deflection angle, the scan height of this simulation model can be acquired. By scanning in the right order, the scan curve of the simulation model can be obtained. By using this simulation measurement model, this study simulates and analyzes the scanning of atomic-scale surface outline. Meanwhile, focusing on the tip radii of different probes, the concept of sensitivity analysis is employed to investigate the effects of the tip radius of probe on the atomic-scale surface outline. As a result, it is found from the simulation on the atomic-scale surface that within the simulation scope of this study, when the tip radius of probe is greater than 12 nm, the effects of single atom on the scan curve of AFM can be better decreased or eliminated.