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结构优化设计的解析灵敏度算法 总被引:6,自引:0,他引:6
以二维单元为例,推导给出线性静力结构优化设计中解析灵敏度算法的计算公式,以有限元分析程序ADINA为基础实现了解析灵敏度算法的计算功能,并通过算例验证了其精度。 相似文献
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金属垫片接触应力分布解析算法 总被引:1,自引:1,他引:0
金属垫片密封是压力容器和管道中常见的密封形式,其失效极少是因强度不足引起的,泄漏是连接系统失效的主要原因.在真实螺栓法兰金属垫片连接结构中,垫片的局部接触应力对螺栓法兰连接结构密封性能的影响较垫片的平均压紧应力更大.笔者在Warters法的基础上,考虑了操作压力的影响,对法兰变形进行理论分析,推导了法兰偏转角的计算公式.根据法兰偏转角和金属垫片力学性能,提出了金属垫片接触应力分布的解析算法.解析计算得到的平均应力与数值模拟结果较为接近,但垫片外缘的最大应力小于数值模拟值,金属垫片接触应力的解析计算方法可作为一种保守的工程算法,可用于真实螺栓法兰金属垫片连接结构的设计. 相似文献
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冗余驱动具有刚度大、承载能力强和运动特性好等优点,设计了10-6、10-5两类构型的10支链Stewart衍生构型,构建了一种数值法和解析法相结合的位置正解半解析算法,并分析了两类构型的工作空间.通过引入虚拟支链,两类构型可进一步衍生为同一种12支链台体型拓扑构型.推导了12支链构型的协调方程,并运用Newton-Raphson法得到虚拟支链的数值解;构建了12支链构型位置正解的全解析数学模型.运用区间分析法研究了两类构型的位置工作空间和姿态工作空间.结果表明,10-5构型的工作空间较规则,且具有良好的对称性. 相似文献
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关于不借助数据库,根据质谱自动地从头开始解析聚糖结构(包括单糖组成、排列信息和单糖之间的连接信息)已有多年研究,然而,如何快速准确地得到结果仍然面临诸多挑战。为了降低时间复杂度,现有的方法要么采用贪心法或者启发式算法,这些算法本身就是不精确的,难以保证得到结果的准确性;要么采用剪枝法或者动态规划之类的精确算法,但是这类算法不仅时间复杂度较高,而且其中大量使用的假设和理想化模型忽视了许多对结果有影响的实验细节。诸如打分函数中对不同候选结构重复使用相同谱峰进行评分的问题,先前的精确算法常常选择回避和无视,这些被忽视的细节最终导致结果的不准确。本工作提出了基于迭代增长的方法“自底向上”地利用谱图解析聚糖结构的算法。与以往迭代方法不同,该算法中增长的单位不再是单糖,而是在算法中产生的子结构,这使得算法的运行速度大大加快。在将各种实验细节纳入算法流程的基础上,通过对20种聚糖的二级质谱图解析以及与先前算法的比较,证实了该算法具有较高的准确性(75%聚糖的正确结构被算法解析为第一)。 相似文献
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研究带约束六杆机构的优化设计问题,针对其在机翼中的特殊构造,提出解析求解该机构的一种新算法。以该算法求解输出和期望输出构成最小二乘为目标函数,以六杆机构3个可动铰点坐标值为设计变量,建立满足其在飞机副翼操纵系统中约束的优化模型。利用复合形法求解该模型,并通过典型算例的验证,表明优化模型的合理与该新算法的可靠、高效。 相似文献
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成形车刀刃形精确设计通用算法理论解析 总被引:4,自引:0,他引:4
对斜装或正装成形车刀刃形的精确设计通用算法进行了理论解析和公式推导。该算法的提出,将为成形车刀的刃形和CAD设计提供精确的设计计算方法和通用的精确数学模型。 相似文献
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针对6自由度并联机构的正运动学无全解析解或全解析解推导困难的现状,提出1种11-6台体型Stewart冗余并联机构,并构建了1种区别于传统全解析法和数值法的半解析算法。首先,通过构建虚拟支链,将11支链构型转换成具有低耦合度的12支链的并联机构,并基于特征点的尺度关系,推导出转换机构的全解析解;然后,运用Newton-Raphson法,数值求解了6个杆长协调方程,并分析了72种情况下迭代次数与初值偏差的关系,据此得到求解不同支链时的最优方程。 相似文献
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针对目前.NET技术应用范围的不断扩大,通过,NET构架,充分利用.NET的快速开发能力,开发了基于Managed DirectX的三维建模器,作为下一步基于三维建模器的虚拟产品技术的基础和平台,在此系统的开发过程中研究了Managed DirectX的开发技术及相关三维图形算法。 相似文献
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在Denavit-Hartenberg参数法建立的机器人末端位姿变换方程的基础上,利用机构通用精度算法建立了机器人末端位姿误差模型。通过矩阵运算,建立了机器人末端位姿误差与各杆件运动学参数误差之间的函数关系式。在SCARA机器人上的实验表明,用此方法建立的误差模型进行误差标定和补偿,可以提高机器人的定位精度。 相似文献
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Larsen L Griffin LD Grässel D Witte OW Axer H 《Microscopy research and technique》2007,70(10):851-863
Polarized light imaging (PLI) is a method to image fiber orientation in gross histological brain sections based on the birefringent properties of the myelin sheaths. The method uses the transmission of polarized light to quantitatively estimate the fiber orientation and inclination angles at every point of the imaged section. Multiple sections can be assembled into a 3D volume, from which the 3D extent of fiber tracts can be extracted. This article describes the physical principles of PLI and describes two major applications of the method: the imaging of white matter orientation of the rat brain and the generation of fiber orientation maps of the human brain in white and gray matter. The strengths and weaknesses of the method are set out. 相似文献
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E. Teimoury M. Modarres A. Kazeruni Monfared M. Fathi 《The International Journal of Advanced Manufacturing Technology》2011,52(1-4):235-244
In this paper, a method to determine the optimal tool orientation to make a more perfect impeller blade surface using a five-axis flank milling machine is presented. Verification of surface geometric accuracy using a 3D coordinate measuring machine is also shown. A mathematical formula is derived which includes the parameters of tool and curved surface to calculate the appropriate tool orientation, whose direction is named the optimal tool orientation. The 3D CAD software Unigraphics (UG) is used to plot models which include the curved surface and the tools of optimal tool orientation and other orientations. The reasonable overlap between curved surface and tool is obtained (overcutting) by checking the interference from the UG, its tool orientation is the optimal tool orientation. According to the optimal tool orientation and position at all cutting points on curved surface, a cutting location source file is derived, which can transform into the NC code for the five-axis tool machine to make the centrifugal impellers of various types. These impellers are measured by using the 3D Coordinate Measuring Machine to verify blade to be free of flaws, and with accurate geometry and the tool, marks are removed from its surfaces. 相似文献
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Weiming Wang Xiuping Liu Ligang Liu 《Journal of Mechanical Science and Technology》2014,28(7):2469-2477
In general, the upright orientation of a model is beneficial for human to recognize this model and is widely used in geometry processing and computer graphics. However, the orientation of the model obtained by existing technologies, such as 3D scanning systems or modeling, may be far away from the right orientation. In order to solve this problem, a robust and efficient upright method is needed. We observe that when the model is aligned with the three axes, the rank of the three-order tensor constructed by this model is the lowest usually. Inspired by this observation, we formulate the alignment of the 3D model with axes as a low-rank tensor optimization problem which is a global and unsupervised method and the genetic algorithm (GA) is used to solve this optimization problem. After the 3D model has been aligned with the three axes, some geometric properties can be used to pick out the best upright orientation from the six candidate supporting bases easily. The three-order tensor is constructed by voxelizing the bounding box of the 3D model, and then filling the voxel element with zero or one based on whether it contains the points of the model or not. The experimental results demonstrate that our method is robust, efficient and effective for all kinds of the models (manifold or non-manifold, man-made or non-artificial, or point cloud). 相似文献