Analysis of ribbed-strip rolling by rigid-viscoplastic FEM

The rolling of ribbed-strips is analysed in the paper using the slightly compressible rigid-viscoplastic finite element method. The energy functional and the rigid-plastic finite element equations for the ribbed-strip rolling process are derived. The simulation results are compared with those obtained by experiments and found to be in good agreement with the latter.     

三辊行星轧制空间模型建立研究

根据三辊行星轧机的运动规律和轧辊设计原理,利用坐标变换的方法,建立起既有倾斜角β又有偏转角α的空间轧辊模型,研究了三辊行星轧机轧辊建模和定位的方法,确定了轧辊和轧件接触点计算的方法和轧件模型,在此基础上建立了三辊行星轧制空间模型.     

Analysis of asymmetrical sheet rolling by a genetic algorithm

Slab analysis of asymmetrical sheet rolling is presented by considering non-uniform normal and shear stress profiles across the section of product. An important phenomenon considered in this paper is the deflection of plate at entry to the deformation zone and the amount of which is predicted by using a genetic algorithm (GA). In the utilized GA, the elimination/replacement operator and a new operator called “the adaptive mutation” are developed in order to increase the efficiency of the search. Shear stresses are taken into account in applying the Von-Mises yield criterion, and it is shown that this improves the accuracy of the model. Rolling force and pressure distribution predicted by the present model are shown to be in good agreements with the experimental and theoretical results of other investigators.     

Modified slab analysis of asymmetrical plate rolling

In this paper the general case of asymmetrical plane strain rolling due to unequal roll diameter, unequal surface speed of the rolls and different contact friction is considered. An analytical model based on the slab method of analysis was used and further developed to obtain the characteristics of asymmetrical sheet rolling and to predict strip curvature. This method describes an enhancement to the rolling theory where friction becomes an integral part of deformation mechanics in the roll gap. To verify the validity of the proposed analytical model, the analytical rolling force, torque and curvature were compared with experimental and analytical results of other investigators. Very good agreements are found. Capability as well as the simplicity of the proposed model in predicting more accurate theoretical results for the rolling force, torque and curvature makes it suitable for the online control application.     

滚锥齿超环面行星传动零件的三维建模

通过对滚锥齿超环面行星蜗杆传动中,行星轮、蜗杆和定子的坐标分析,得到了各零件的建模曲线方程。在此基础上,利用VB编程语言及Solidworks软件对其三零件完成了三维实体参数化建模。     

Rigid-plastic finite-element method for analysis of three-dimensional rolling that requires small memory capacity

At present, caliber rolling is analyzed using the three-dimensional rigid-plastic finite-element method. In this paper, a new method of analysis which requires less memory capacity than the conventional method is proposed. In the conventional method, the shape of the whole region is updated after the functional of the region is minimized, whereas in the proposed method, the shape of part of the region (large region) is updated after the functional of the large region is minimized. The load, torque, material shape, hydrostatic stress and equivalent strain rate obtained using the proposed method agree with those obtained using the conventional method within the allowable range of convergent error. Also, although the computation time for the proposed method is rather long compared with that for the conventional method, the memory capacity required for the proposed method is small compared with that for the conventional method. Finally, analysis of various types of caliber rolling in which the number of finite elements in the large region coincides with that in the whole region in analysis using the conventional method is carried out and reasonable stress and strain distributions are obtained.     

冷轧机板形控制系统弯辊力预设定模型开发

针对某公司六辊冷轧机,采用影响函数法建立了辊系变形计算模型并开发了相应的计算程序。利用所建辊系变形模型结合轧机的板形控制策略,建立了针对轧机的理论和在线两种弯辊力预设定模型。实例计算表明,所开发模型精度符合实际要求,可用于生产实际,为提高轧机板形控制预设定精度,改善轧机产品的板形质量提供了理论依据。     

Simulation of Mannesmann piercing process by the three-dimensional rigid-plastic finite-element method

Simulation of the Mannesmann piercing process is performed for the first time by the three-dimensional rigid-plastic finite-element method. Firstly, a method of analysis is proposed for the steady-state formulation in the case that the sides of the finite elements cannot be made to coincide with the streamline of the material flow. Secondly, the simulation of the Mannesmann piercing process is performed under the variation of rolling conditions such as the feed angle, the minimum roll gap, the maximum plug diameter, the plug advance and the guide shoe diameter, and the effects of the rolling conditions on various rolling properties such as the outer diameter, the inner diameter, the roll force, the mandrel force, the equivalent strain distribution and the equivalent strain rate distribution are demonstrated. Finally, the results of the analysis are compared with the results of an experiment using Plasticine. The dimension in the rolling condition of the experiment is scaled to one-third of the dimension in the rolling condition in an actual Mannesmann piercing process. The analytical results agree with the experimental results and the validity of the method of analysis is confirmed.     

A low cost 3D shape measurement method based on a strip shifting pattern

We present a simple, low cost but fast 3D shape measurement method. There is no limitation on the object's material and texture. We use a projector to project a strip shifting pattern on the object, and a digital camera to record videos of the scene. The distortion of the strip shadow on the object is used to get the object's 3D information. A novel space-time edge finding method is introduced to position the shadow edge accurately. This edge finding method overcomes the effect of inter-reflection and high light. Using this space-time information, we can calculate the pixels' 3D coordinates. To get the 3D shape of an object with black texture, we improve the black strip pattern to a 3-color strip pattern. The bad data are filtered by a post-processing 3D filter, which makes full use of the neighborhoods' geometric constraints and the view point constraint. Meanwhile, our measurement method is fast, regardless of the complexity of the shape.     

A theoretical study on the application of asymmetric rolling for the estimation of friction

In this work, a method for the estimation of friction coefficient is proposed based on the asymmetric rolling operation. Asymmetry is produced by operating the lower and upper rolls at different speeds. A slab method based computer code is developed for estimating the curvature of the rolled sheet under asymmetric rolling conditions. Strain-hardening behavior of the material has been incorporated and Wanheim and Bay's friction model is employed. The developed code is used for solving the inverse problem of estimating the coefficient of friction by measuring the curvature of the rolled sheet under known operating conditions. The simulations show a good potential of the method.     

环件辗扩加工的控制方法

建立了辗扩环件的数学模型,确定加工控制尺寸,提出了辗扩设备的整体控制方案,为辗扩设备控制系统的研制、改进提供参考和依据。     

光学三维测量技术与应用

光学三维测量技术是一种可视化的测量技术,能完成复杂形体的点、面、形的三维测量,能实现非接触测量,在制造业和航空航天领域得到广泛应用。航空三维激光扫描与摄影测量技术利用激光测距原理和航空摄影测量原理,与基于全球定位系统(GPS)和惯性测量装置(IMU)的机载定位定向系统(POS)联接,可以快速获取大面积地球表面三维数据。本文对光学三维测量技术和航空三维激光扫描技术做一简单介绍,给出三维激光扫描技术在航空航天领域的几个应用。     

反求工程中基于图像灰度信息的三维曲面重构

基于物体表面图像灰度信息的三维几何形状反求(由明暗恢复形状),已成为工业界和学术界研究的热点问题之一。首先给出描述该问题的数学物理模型,并利用变分原理将其转化为一个泛函的极小化问题,然后应用有限差分思想和非线性最小二乘方法,将该泛函极小化问题归结为求解线性方程组。最后利用该算法产生的迭代公式对合成图像进行计算,并应用曲面造型软件CAXA(制造工程师)进行曲面重构,从而验证了该方法的有效性和可行性。     

三维模型检索中手绘草图轮廓特征的应用研究

为了能够在大量的三维模型中高效地检索出需要的模型,提出了基于手绘草图的轮廓特征实现三维模型检索的方法.首先对输入的草图进行预处理,提取草图平滑的轮廓;然后利用傅立叶变换对提取的草图轮廓进行降维处理,生成具有平移、旋转、比例缩放不变性的特征向量.利用动态时间规整方法计算特征向量的距离,比较手绘草图和3D模型之间的相似性.实验表明该方法具有较好的检索效率和检索效果.     

Inspection of weld shape based on the shape from shading

The weld bead shape is crucial for weld quality. Automatic inspection on the 3D shape of a weld bead is achieved by recording the image of the weld bead with an optical sensing method and then calculating the 3D shape parameters with a shape-from-shading technology based on a single image in the computer-vision domain. The paper first introduces a method of shape from shading based on a single image and puts forward its implementation. It then presents the improved measures of the original algorithm according to the defects of the computed results and finds accuracy compared with the former method by a synthetic image. Finally, the improved algorithm is applied to the surface height reconstruction of weld bead successfully .     

基于形状特征的管路接头测量和三维重建方法

针对复杂管路系统中的接头同步测量和三维重建的难题,提出一种基于形状特征的管路接头测量和三维重建方法。该方法通过接头CAD模型边缘轮廓和实物图像边缘轮廓进行形状特征匹配来实现接头空间位姿的测量。首先通过建立虚拟相机"视点球"获取接头CAD模型边缘轮廓的投影图像,经过金字塔分层组成接头的形状特征图库;然后与获取的接头实物图像边缘轮廓进行对比匹配;最后利用最小二乘法迭代求解接头的空间位姿,并重建接头的三维模型。开发了管路多目视觉测量系统并进行了接头位姿测量和管路三维重建实验,实验表明该方法的接头测量和三维重建时间可控制在1min内,位置误差为0.654mm,姿态误差为0.73°,测量和重建的效率与精度满足工程要求。     

基于Deform 3D的钻削力仿真研究

采用大型有限元分析软件Deform 3D对普通麻花钻的钻削力进行了仿真研究。给出了仿真中涉及的相关技术与关键参数的设置原则,进行了钻削测力试验,并以试验数据为基准,将仿真数据和传统经验公式的计算数据进行了对比与分析。结果表明:有限元法对钻削力的仿真数据已接近试验值。     

3D RIGID－PLASTIC FINTEELEMENT ANALYSIS OF BACKWARD SPINNING OF CYLINDRICAL WORKPIECE

３ＤＲＩＧＩＤ－ＰＬＡＳＴＩＣＦＩＮＴＥＥＬＥＭＥＮＴＡＮＡＬＹＳＩＳＯＦＢＡＣＫＷＡＲＤＳＰＩＮＮＩＮＧＯＦＣＹＬＩＮＤＲＩＣＡＬＷＯＲＫＰＩＥＣＥ３ＤＲＩＧＩＤ－ＰＬＡＳＴＩＣＦＩＮＴＥＥＬＥＭＥＮＴＡＮＡＬＹＳＩＳＯＦＢＡＣＫＷＡＲＤＳＰＩＮＮ...     

浅谈3D技术在个性化产品定制中的应用

定制个性化的产品已经越来越受到人们的关注与向往,个性化的产品的定制离不开先进的3D技术,在定制过程中,需要综合运用产品测绘、三维扫描、工业设计、3D建模、设计变更与优化、数据处理及转换等技术来把个性化的产品进行呈现,然后通过3D打印技术将产品模型数据打印出来,实现产品的个性化定制。     

Java 3D在虚拟现实中的应用

Java 3D是基于Java平台面向对象的三维图形应用程序接口,便于在网上实现三维图形的显示、浏览.Java语言具有结构中立性、网络分布性等优点,它的3D图形API在开发Internet及WWW上的图形网络应用程序时有极大优势,因而得到了迅速地推广和应用.介绍了Java 3D的功能、数据结构并组建了一个虚拟三维场景的网上发布系统的基本体系结构.