摆动输出活齿凸轮机构传动及齿廓方程

融合活齿传动和凸轮机构两种传动形式的优点,提出了摆动输出活齿凸轮机构,并分析了其结构及传动原理。作为一种新颖的传动形式,该机构具有齿数灵活、全齿啮合、摆角范围宽,可按简谐曲线、等加速度曲线以及无停留修正梯形曲线等多种既定规律摆动输出的特点。借助凸轮曲线位移的已知性建立了输入、输出凸轮转角在任意时刻的对应关系以解决传动比不恒定而无法直接创建传动关系的问题,进而推导出了输入、输出凸轮的理论齿形方程和工作齿廓方程。在理论分析的基础上,给定设计参数并绘制输入、输出凸轮的理论齿形与工作齿廓啮合线以及机构啮合位形,皆未发生干涉现象,验证了方程推导的正确性,为以后进一步的研究及应用提供了分析基础。     

一种摆线针轮传动多齿啮合接触特性分析方法

为有效地揭示齿廓修形、弹性接触及负载变化对摆线针轮传动多齿啮合接触动态特性的影响规律,基于多体动力学和弹性接触理论提出了一种可精确预估摆线针齿动态啮合对数、确定接触点位置并获取接触载荷的动力学分析方法。首先,建立了摆线针轮系统刚体多体动力学模型;其次,在数值计算的任一时刻,循环判断摆线齿廓的离散点与各个针齿之间是否满足接触条件,确定最大接触深度并计算法向接触载荷;最后,将摆线针齿接触载荷等效为系统广义力,建立了含多齿啮合接触关系的摆线针轮传动系统动力学方程。在此基础上,以某一针摆传动系统为算例,分析齿廓修形、弹性接触及负载变化对摆线针轮传动多齿啮合接触动态特性的影响。研究结果表明,摆线针轮传动的实际传力针齿数由齿廓修形和负载特性决定。该方法对于具有不同传动比的摆线针轮传动系统,均能高效准确地完成齿廓修形和负载变化条件下的传力针齿数预估和接触载荷计算。     

A frontal Delaunay quad mesh generator using the L ∞ norm

In a recent work, a new indirect method to generate all‐quad meshes has been developed. It takes advantage of a well‐known algorithm of the graph theory, namely the Blossom algorithm, which computes in polynomial time the minimum cost perfect matching in a graph. In this paper, we describe a method that allows to build triangular meshes that are better suited for recombination into quadrangles. This is performed by using the infinity norm to compute distances in the meshing process. The alignment of the elements in the frontal Delaunay procedure is controlled by a cross field defined on the domain. Meshes constructed this way have their points aligned with the cross‐field directions, and their triangles are almost right everywhere. Then, recombination with the Blossom‐based approach yields quadrilateral meshes of excellent quality. Copyright © 2013 John Wiley & Sons, Ltd.     

多波束测深系统中的海底地形可视化技术研究

针对直接使用大数据量的离散深度数据实现海底地形可视化时,基于不规则三角网的海底地形建模速度慢、稳健性低的问题,提出一种联合矢积测试的子网合并双向缝合算法,设计了一种基于二叉树的动态分块合并机制。该算法能够避免相交三角形或线形三角形的产生并使缝合后新生成的初始三角形形状趋于最优,提高了子网合并速度与整个构网程序的稳健性,实现了基于快速Delaunay构网的海底地形建模和三维可视化。实验结果表明,该算法能够明显提高子网合并速度与程序稳健性,适用于大数据量离散测深数据的海底地形绘制。     

基于ADAMS少齿数齿轮啮合力的仿真

结合geartrax对少齿数齿轮的造型,利用ADAMS软件强大的分析能力,对一般齿轮的啮合以及少齿数齿轮的啮合进行仿真,分别仿真一般齿数齿轮和少齿数齿轮在某一驱动作用下的的啮合力的大小。     

用杠杆法计算行星齿轮机构的啮合效率

以5HP-24自动变速器行星齿轮机构传动为例,通过采用杠杆法计算行星轮系的啮合效率,杠杆法不但对求多排并联行星轮传动比比较简单,通过杠杆图建立转速图和受力图,可以方便判断各行星轮的啮合功率流向,是计算行星轮系传动啮合效率很有效的方法.     

φ139.7mm×7.72mm J55 LC套管脱落失效分析

某油田定向井的二开套管在作业时发生脱扣事故。对套管失效部位进行综合分析和讨论。结果表明：失效的主要原因是内外螺纹啮合有效扣数〈22扣,另外材料性能较低也是套管脱落的原因之一。     

基于LED道路照明的偏光透镜设计

基于非均匀网格划分法设计了一种用于LED道路照明的偏光透镜。该透镜能够把LED发出的光线更多地投射在路面上。这种偏光透镜设计减少了道路外的光污染,同时有效提高了路面的光线利用率。在光学软件Lighttools的模拟中,测得整个光学系统照度均匀度为77.6%。并且充分考虑材料的吸收损失和界面的反射损失后,光能利用率高达84.5%。在照明仿真软件Dialux中对该偏光透镜的配光曲线IES模型导入后在模拟道路中进行计算仿真,得到其亮度总均匀度为0.74,并且眩光限制阈值增量控制在9%。所以,该偏光透镜的亮度均匀度、照度均匀度及眩光控制等指标都很好地满足了我国《城市道路照明设计标准》的要求。     

半切顶插齿刀的精确设计和Y7125半切顶角度的调整计算

用平面啮合原理通俗地介绍了目前广泛应用的半切顶插齿刀的设计方法与步骤,导出了半切顶插齿刀主切削刃与半切顶切削刃的交点半径的通用计算公式,从而解决了半切顶插齿刀的精确设计,和半切顶齿形的测量。从Y7125型磨齿机的磨齿原理进行分析,从设计半切顶插齿刀中所获得的两个基圆中,求取磨制半切顶插齿刀的半切顶修整角的调整。     

Three-steps-meshing based multiple crack identification for structures and its experimental studies

Multiple crack identification plays an important role in vibration-based crack identification of structures. Traditional crack detection method of single crack is difficult to be used in multiple crack diagnosis. A three-step-meshing method for the multiple cracks identification in structures is presented. Firstly, the changes in natural frequency of a structure with various crack locations and depth are accurately obtained by means of wavelet finite element method, and then the damage coefficient method is used to determine the number and the region of cracks. Secondly, different regions in the cracked structure are divided into meshes with different scales, and then the small unit containing cracks in the damaged area is gradually located by iterative computation. Lastly, by finding the points of intersection of three frequency contour lines in the small unit, the crack location and depth are identified. In order to verify the effectiveness of the presented method, a multiple cracks identification experiment is carried out. The diagnostic tests on a cantilever beam under two working conditions show the accuracy of the proposed method: with a maximum error of crack location identification 2.7% and of depth identification 5.2%. The method is able to detect multiple crack of beam with less subdivision and higher precision, and can be developed as a multiple crack detection approach for complicated structures.