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渐消失曲面,是沿主体曲面走势延伸至某处自然消失的曲面,它能体现速度感和流畅感,是曲面增强设计效果的一种常用手段。渐消失曲面的构建:首先是创建出主体曲面;然后创建投影曲线、边界曲线和ISDX曲线作为骨架线;最后由边界曲线产生渐消失曲面。在渐消失曲面的创建过程中,如何创建高质量的ISDX曲线是创建高质量曲面特征的关键。除此之外,还有一个重要的因素影响ISDX曲面质量,这就是相邻曲面间的连接形式。通过设置相切或曲率连接方式,使两个相邻曲面间光滑过渡。 相似文献
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参数曲面的三角化算法是有限元分析和数控机床路径规划的基础。文中提出了一种新的基于分层递推思想的三角化算法,直接在曲面上生成三角网格。根据曲面微分几何定义相对保守的曲率球概念,将局部曲面近似成曲率球面,在球面上建立三角形边和面片的误差模型和递推关系,计算三角形各个顶点在欧式空间以及参数空间的坐标。然后采用逐层递推的方法,从曲线边界开始,逐层生成三角形网格,直至满足收敛准则。文章最后将此算法用C++程序语言编程并通过NURBS曲面进行实例验证,结果表明该算法能够较好的对参数曲面进行三角网格划分。 相似文献
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传统的基于三角片模型雕刻曲面数控加工中,只有少量的三角片参与每个刀位点计算,大量的工作是在全体三角片中搜索刀具投影区覆盖的三角片.为克服上述缺点,提出了一种矩形包络法,快速滤除了绝大多数刀具投影区外的三角片.在一次搜索过程中,将刀具投影区覆盖的三角片独立保存,避免了进一步计算时搜索整个STL文件.针对与刀具投影区叠加的每个三角片,计算其平面、顶点、三条边与刀具的接触点来计算最终的刀位点,得到刀具运动轨迹.给出了利用该方法得到的刀具轨迹仿真实例,验证了算法的可行性. 相似文献
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Pro/E的曲面模块Pro/Surface是功能强大的曲面建模工具,但对外形曲面较复杂的产品用Pro/Surface进行建模,方法较为繁琐,有时需要构造复杂的三维曲线,甚至经过多次投影产生所需曲线,最后再构建成面,对于多个曲面过渡处更难处理,修改时也受到父子关系的约束.Pro/E提供一种高效、灵活的自由形式曲线曲面创建工具--造型Style,笔者以手持式电钻壳体曲面建模为例,阐述在进行复杂曲面建模时如何灵活运用Style,并着重分析复杂曲面的主要建模思路. 相似文献
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阐述SiemensNX的等弧长投影曲线的原理,探讨创建曲面图样的原理及其加工应用,并在曲面上加工曲面图样。 相似文献
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基于强度约束的基底桥连接体数字化设计 总被引:1,自引:0,他引:1
为解决基底桥数字化设计中连接体生成和截面强度检测的问题,结合计算机辅助设计技术,提出了基于强度约束的基底桥连接体的数字化设计方法先将连接体截面模板投影到相邻的基底冠和桥体上,得到投影曲线作为连接体的边界曲线;然后在2条投影曲线间利用蒙皮剖分算法生成网格曲面,同时计算连接体中间截面的横截面积以检测强度是否符合设计要求。设计过程中,若连接体强度不足或形态不符合要求,可通过编辑投影曲线控制点实时改变连接体形状。结果表明,通过蒙皮剖分算法可快速生成连接体曲面,对曲面中截面面积的计算实现了对截面强度的检测。 相似文献
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在采用组合函数法构造过渡曲面方法的基础上,提出了一种在基曲面上构造G1连续的过渡切触线的方法。该方法只需给定曲面上的一组点列及其点上的切矢,在此基础上构造一条空间曲线,并基于正交投影法将这条曲线投影到基曲面上得到一条G1连续的过渡切触线,使得设计人员可以根据需要直接在基曲面上确定过渡曲面与基曲面的切触线的位置,并以此为边界构造过渡曲面。还提出了新的构造过渡辅助面和重新参数化局部基曲面的方法,以适应过渡切触线为分段曲线的情况,并将其应用于翼身融合面的构造中,实例证明了该方法的可行性,效果令人满意。 相似文献
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针对三角网格模型,提出了一种基于隐式曲面的等距算法.该算法首先对三角网格模型进行拓扑重建,然后对顶点进行八叉树采样,由采样点及采样点的单位法矢点来构建隐式曲面,将隐式曲面等距,最后将原模型的顶点投影到等距曲面得到投影点,根据先前建立的拓扑关系,将投影点三角网格化得到等距后的三角网格模型.该算法在一定数值范围内避免了等距模型自交问题,而且等距模型三角网格均匀,质量高. 相似文献
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反求工程中基于边界扩展的三角网格构造 总被引:1,自引:0,他引:1
针对非接触式方式测量的大规模散乱点云数据建模,提出一种三角剖分算法,该算法适用于多张自由曲面片构成的曲面物体,尤其适用于含内孔的曲面对象。算法过程包括两个阶段:第一阶段,采用一种空间栅格装点法来进行初始点云数据精简,精简比率通过栅格小正方体单元尺寸控制;第二阶段,构造种子三角形,通过连接已剖分网格区域的边界边与最优扩展点采形成三角网格,从而向外延展,也可以时一个带有内孔的复杂自由曲面直接进行三角剖分,无需人工分区。实验结果表明该算法可以快速、有效地从三维数据点云建立几何模型。 相似文献
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在逆向工程应用中,对于带有孔洞的散乱测量数据,给出了孔洞自动识别算法,通过提取孔洞邻域的局部数据进行三角网格划分和网格化简,得到带有孔洞的基网格.提出了基网格孔洞三角划分方法进行孔洞填补,在此基础上采用最小二乘方法进行Loop细分曲面拟合得到光滑的细分曲面片.以孔洞边界为基准,给出了细分曲面裁剪算法去除拟合曲面的多余部分,最后得到精确的孔洞填补数据. 相似文献
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In-Hugh Choi Min-Yang Yang Won-Pyo Hong Tae-Sung Jung 《The International Journal of Advanced Manufacturing Technology》2005,25(3-4):325-333
Finish machining of a curved surface is often carried out by an NC system with curve interpolation in the field. This function, called a NURBS interpolation, adopts a feedrate optimizing strategy based on both the geometrical information of the curved path and dynamic properties such as the curvature of the curve, the allowable acceleration and the time constant. However, in the case of a finish cut using a ball-end mill, the curve interpolator needs to take the machining process into account for improved surface roughness, while reducing the polishing time. This surface roughness on high-speed machining is theoretically defined by the feed per tooth and the pickfeed at the given radius of the tool. In this study, the effect of low machinability at the bottom of a tool on surface roughness is also considered. A curve interpolation algorithm is proposed for generating particular feedrate commands that are able to control the roughness of a curved surface. The simulation of the machined surface by the proposed algorithm was carried out, and experimental results are presented. A feedrate scheme that depends on the inclination angle has important potential application in part finishes consistent with prescribed surface roughness. The results show that the proposed algorithm is potentially useful for roughness-controlled machining of curved surface products. 相似文献
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提出了一种新的曲面求交算法,采用精度好、效率高、计算稳定的迭代方法求得等参数网格线在曲面上的交点,并通过跟踪获得两曲面的交线。本算法由三个子算法组成,一个是求曲面上到固定点距离最近的点,一个是求参数网格线与曲面的交点,一个是求曲面与曲面的交点。为保证不遗漏交点,利用第一个算法对参数网格点进行分类,跟踪交点时利用第三个求下一个交点。与离散法求交相比,本算法具有计算稳定性、可靠性好,速度快,精度高的优点 相似文献
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为了降低承载传动误差波动产生的振动激励,提出了成形磨人字齿轮直线型对角修形优化设计。根据ISO对角修形定义,计算齿顶、齿根修形起始线在旋转投影面上的螺旋角,将修形曲线设计为直线型,给定最大修形量,确定对角修形的齿面方程。利用齿面接触分析和轮齿承载接触分析,以工作载荷下人字齿轮承载传动误差波动量最小为优化目标,采用遗传算法优化对角修形参数。确定以目标修形齿面法向偏差的平方和最小的目标函数,以螺旋角、模数、压力角为设计变量,采用遗传算法分别对齿顶和齿根修形区域进行逼近,从而实现对角修形的成形磨加工。结果表明,人字齿轮直线型对角修形可以将承载传动误差波动量降低到36.65%;采用三截面砂轮成形磨的理论误差控制在1μm以内,获得较高的齿面精度;试验人字齿小轮齿的检测结果控制在4级精度以内,并进行了齿轮副的滚检试验,从而验证该方法的有效性。 相似文献
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ZhuCheng Li Young Chang Kang Jun-Hee Moon Heui Jae Pahk 《The International Journal of Advanced Manufacturing Technology》2013,67(5-8):1597-1607
A solder bump is regarded as a specular-dominant shiny component that distorts the height profile and causes poor repeatability during the bump height measurement. In this paper, we analyze the relationship between the projection angle and other factors based on the general reflectance mechanism of the specular surface. An optimum projection angle exists, such that can produce the best repeatability of the bump height measurement; therefore, we propose a convenient experimental system with a circular motion guide that can evaluate the optimum projection angle experimentally. The experimental results show that best repeatability is obtained with the optimum projection angle. The proposed method to find the optimum projection angle in this paper can therefore be applied to the many cases of measurement for ball grid array samples having specular-dominant shiny component. 相似文献
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S. KumarAuthor VitaeZ. AhmadAuthor Vitae T. MansoorAuthor Vitae 《Flow Measurement and Instrumentation》2011,22(3):175-180
Conventional weirs are inherited with afflux and submergence of area upstream of the weir. Various weirs of modified plan form have been suggested in the past to enhance their discharging capacity and to restrict the afflux. Presented in this paper are results of the experimental study carried out to investigate the discharging capacity of a sharp-crested triangular plan form weir under free flow conditions in a rectangular channel. The efficiency of the triangular plan form weirs is better than the normal weir and also high for low vertex angle and decreases with the increase of ratio of head over the crest of the weir and crest height due to interference of the water jets downstream. The computed discharge using the proposed equation is within ±5% of the observed ones. Sensitivity of the weir, i.e., change of discharge due to unit change in head is also carried out which indicates that the weir is more sensitive at the low head and low vertex angle. 相似文献
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A new camera calibration method based on triangular primitives for solid grid sphere objects are proposed in this work to address the contradiction among the number of cameras, calibration accuracy, and algorithm stability in the current camera calibration process. In the proposed method, a sphere is used as the base, and the surface coverage curve of the sphere forms a calibration object as the grid based on triangular primitives. We use the absolute quadratic curve and vanishing point to calculate the intrinsic and extrinsic parameters of the camera, respectively. The proposed method can simplify the element correspondence in the calibration and calibrate multiple cameras in different positions simultaneously. Experimental results show that the new 3D calibrator exceeds the calibration accuracy and stability of traditional algorithms. Moreover, the comprehensive evaluation of the algorithm is improved significantly. 相似文献