Efficient and accurate worm grinding of spur face gears according to an advanced geometrical analysis and a closed-loop manufacturing process

Worm grinding has been applied to manufacture gears to pursue high accuracy and fine surface finish.When the worm used to grind face gears is manufactured with multi-axis computer numerical control(CNC)machining,the machining accuracy is usually improved by increasing the number of tool paths with more time cost.Differently,this work proposes a generated method to improve the efficiency by dressing the worm surface with only one path,and a closed-loop manufacturing process is applied to ensure the machining accuracy.According to an advanced geometric analysis,the worm surface is practically approximated as a swept surface generated by a planar curve.Meanwhile,this curve is applied as the profile of a dressing wheel,which is used to dress the worm surface.The practical machining is carried out in a CNC machine tool,which was originally used to grind helical gears.Finally,a closed-loop manufacturing process including machining,measurement,and modification is proposed to compensate the machining errors.The proposed method is validated with simulations and practical experiments.

A NOVEL METHOD FOR NETWORK WORM DETECTION BASED ON WAVELET PACKET ANALYSIS

Objective To detect unknown network worm at its early propagation stage. Methods On the basis of characteristics of network worm attack, the concept of failed connection flow (FCT) was defined. Based on wavelet packet analysis of FCT time series, this method computed the energy associated with each wavelet packet of FCT time series, transformed the FCT time series into a series of energy distribution vector on frequency domain, then a trained K-nearest neighbor (KNN) classifier was applied to identify the worm. Results The experiment showed that the method could identify network worm when the worm started to scan. Compared to theoretic value, the identification error ratio was 5.69%. Conclusion The method can detect unknown network worm at its early propagation stage effectively.

Contact analysis and load distribution of double-envelop hourglass worm gearing affected by errors and load

An approach for the contact analysis and load distribution of double-envelop hourglass worm gearing is presented, which is based on a 3-D elastic contact finite element method (FEM) model that accommodates the influence of errors and load. As compared with existing tooth contact analysis model that assumes rigidity for the contacting surfaces, the proposed model provides a more realistic analysis on the contact patterns, the distribution of contact load and transmission errors. It is also capable of exploring the influence of different errors on meshing performances, the contact deformation, the shift of the contact zone and load share among the meshing tooth-pairs under different load.

Optimal Design for an End Face Engagement Worm Gear with Multiple Worm-wheel Meshing

To solve the problem for lacking a special mechanical transmission that could provide multiple outputs with high transmission efficiency and good lubrication in the modem industrial, a novel worm gear, named end face engagement worm gear, with multiple worm-wheel meshing is proposed for the first time. The essential parameters for the worm gear are optimized to enhance lubrication and meshing properties. Moreover, analysis of variance（ANOVA） is applied to determine the optimum levels and to determine the influence of parameters. The ANOVA results show that the novel end face engagement worm gear with multiple worm wheels provides high lubrication（the lubrication angle is more than 89~） and meshing performance（the induce normal curvature is less than 0.0002 mm ＇）. The interaction between center distance and roller slant distance most strongly influences the lubrication angle（contributed 51.6%）, followed by the parameters of center distance（contributed 25.0%）, roller slant distance（contributed 16.4%）, tooth angle of gear, gear ratio, and roller radius. In addition, roller radius most strongly influences the induced normal curvature（contributed 39.4%）, followed by roller slant distance（contributed 15.2%）, tooth angle of the gear（contributed 9.0%）, center distance, and gear ratio. The proposed worm gear helps to enrich the no-backlash high precision worm drive and the optimal design method can provide a useful reference on performance improvement of other worm gear.

Modification Design Method for an Enveloping Hourglass Worm Gear with Consideration of Machining and Misalignment Errors

The influences of machining and misalignment errors play a very critical role in the performance of the anti-backlash double-roller enveloping hourglass worm gear(ADEHWG).However,a corresponding efficient method for eliminating or reducing these errors on the tooth profile of the ADEHWG is seldom reported.The gear engagement equation and tooth profile equation for considering six different errors that could arise from the machining and gear misalignment are derived from the theories of differential geometry and gear meshing.Also,the tooth contact analysis(TCA) is used to systematically investigate the influence of the machining and misalignment errors on the contact curves and the tooth profile by means of numerical analysis and three-dimensional solid modeling.The research results show that vertical angular misalignment of the worm wheel(Δβ) has the strongest influences while the tooth angle error(Δα) has the weakest influences on the contact curves and the tooth profile.A novel efficient approach is proposed and used to minimize the effect of the errors in manufacturing by changing the radius of the grinding wheel and the approaching point of contact.The results from the TCA and the experiment demonstrate that this tooth profile design modification method can indeed reduce the machining and misalignment errors.This modification design method is helpful in understanding the manufacturing technology of the ADEHWG.

Temperature Field Simulation and Experimental Study of Anti‑backlash Single‑Roller Enveloping Hourglass Worm Gear

In gear transmission,temperature rise has a non-negligible impact on the accuracy,noise and transmission efficiency.However,there is no relevant research on the temperature rise of the anti-backlash single-roller enveloping hourglass worm(ASEHW)gear.To solve this problem,based on tribology principle and Hertz contact theory,the thermal power calculation method of the ASEHW gear was proposed for the first time and thermal analysis was carried out by Ansys software.The bulk temperature of the ASEHW gear under four different rotating speed(300 r/min,600 r/min,900 r/min,1200 r/min)is calculated.The main factors causing temperature rise of the ASEHW gear are analyzed theoretically.Meanwhile,an experimental study is performed to verify the simulation results and validate the theory methods.The theory presented in this paper provides a solution for the thermal power calculation of ASEHW gear.This research provides a theoretical basis for further optimization of ASEHW gear.

New method for calculating face gear tooth surface involving worm wheel installation errors

The machining principle and realization method for the continuous generative grinding face gear by a worm wheel are introduced. Based on a five-axis linked CNC grinding machine, a new method is presented to deprive the equation of face gear error tooth surface by assuming the tool surface as the error surface, where actual tool installation position error is introduced into the equation of virtual shaper cutter. Surface equations and 3-D models for the face gear and the worm wheel involving four kinds of tool installation errors are established. When compared, the face gear tooth surface machined in VERICUT software for simulation based on this new method and the one obtained based on real process(grinding face gear by using a theoretical worm wheel with actual position errors) are found to be coincident, which proves the validity and feasibility of this new method. By using mesh planning for the rotating projection plane of the face gear work tooth surface, the deviation values of the tooth surface and the difference surface are acquired, and the influence of four kinds of errors on the face gear tooth surface is analyzed. Accordingly, this work provides a theoretical reference for assembly craft of worm wheel, improvement of face gear machining accuracy and modification of error tooth surface.

DIRECT DIGITAL DESIGN AND SIMULATION OF MESHING IN WORM-GEAR DRIVE

A direct digital design method （DDDM） of worm-gear drive is proposed. It is directly based on the simulation of manufacturing process and completely different from the conventional modeling method. The loaded tooth contact analysis （LTCA） method is analyzed, in which the advanced surface to surface searching technique is included. The influence of misalignment errors and contact deformations on contact zone and transmission error （TE） is discussed. Combined modification approach on worm tooth surface is presented. By means of DDDM and LTCA, it is very conven- ient to verify the effect of worm-gear drive＇s modification approach. The analysis results show that, the modification in profile direction reduces the sensitivity of worm-gear drive to misalignment errors and the modification in longitudinal direction decreases the TE. Thus the optimization design of worm-gear drive can be achieved prior to the actual manufacturing process.

圆柱及环面蜗杆传动副承载能力分析与试验

针对某工程机械的实际运行工况和设计参数要求,建立蜗杆传动副优化设计目标函数及工况约束。设计并优化圆柱蜗杆传动副和环面蜗杆传动副,分析2类蜗杆传动副在工作载荷和静态自锁载荷下的齿面接触特性;研制对应2种类型蜗杆副传动样机,搭建传动副样机性能测试试验台,开展传动副的负荷运转试验并对比考察齿面磨损情况。结果表明:在相同的设计参数、加载方法和加载载荷下,环面蜗杆副相较于圆柱蜗杆副,同时接触齿对较多,齿面等效应力和等效应变较小,齿面磨损较轻,承载能力更高。

点接触共轭渐开线蜗杆副啮合理论及性能分析

点接触共轭渐开线蜗杆传动可以降低蜗杆副对制造、装配等误差的敏感性,并能保证传动精度。基于微分几何和齿轮啮合原理,构建了含有制造和安装误差的点接触共轭渐开线蜗杆传动数学模型,研究了螺旋角、模数、压力角等主要设计参数对啮合性能的影响规律,并进行了传动副对制造和安装误差敏感性的研究。通过仿真实验验证了接触区的分布情况。研究结果表明,含有制造和安装误差时,传动副的瞬时传动比恒定;选取适中的螺旋角、较小的模数及较小的压力角会增大接触区的面积,提高传动副的重合度;传动副对制造和安装误差均不敏感,但应尽量减小或避免制造和安装轴交角造成的误差。通过仿真分析得到接触区和重合度与理论计算结果一致,验证了所提理论的正确性。

考虑时滞影响的无线传感网络蠕虫病毒自适应检测方法

无线传感网络中的蠕虫病毒攻击存在着一定的时滞情况,攻击检测难度较大。为了准确检测无线传感网络中的蠕虫病毒,提出一种考虑时滞影响的无线传感网络蠕虫病毒自适应检测方法。采集大量无线传感网络流量数据,对全部数据进行降维处理。在网络蠕虫病毒攻击存在时滞的情况下,将PGM-NMF算法和聚类分析方法相结合,实现无线传感网络节点的异常检测及分类,判断蠕虫攻击的类型,实现蠕虫病毒自适应检测。仿真结果表明:蠕虫病毒攻击时滞为12 ms时,所提方法检测蠕虫病毒的漏报率为9.3%,成功率为95.50%,误报率为0.69%,漏检率为2.9%,蠕虫病毒自适应检测耗时平均值为5.0 s。

蜗杆传动蜗杆轴向力判定新方法教学实践

为实现机械设计基础课程的教学目标,激发学生学习兴趣,降低学习难度,创新教学方法,以有效解决蜗杆轴向力方向判定的问题,在蜗杆受力分析的基础上,由圆柱齿轮切向力方向判定出发,结合基于SolidWorks Motion软件的蜗杆旋转运动仿真,根据轮齿运动时序状态分析,确定轮齿的感觉运动方向,得出蜗杆轴向力与其感觉运动方向轴向分量相反的结论,最终提出了基于感觉运动的蜗杆轴向力方向判定方法,并通过了基于“左右手定则”的对比实例验证。将该方法应用到工业设计专业2017级、汽车服务工程专业2020级的教学当中,学生平均成绩相对于采用传统方法教学的行政班,优秀率提高,不及格人数减少,齿轮受力分析题的成绩有所提高,课程实践取得了良好的教学效果,研究为机械设计基础教学方法的创新提供了一定的参考。

基于多体理论的蜗轮蜗杆精密转台精度设计研究

为了提高蜗轮蜗杆式精密型回转工作台的工作精度需求,文章基于多体系统动力学理论,结合该转台的结构及运动机理,建立了蜗轮蜗杆精密转台误差传递的数学模型,分析了各项误差对精度的影响,提出了蜗轮蜗杆精密转台误差灵敏度的分析方法,通过函数微分法,识别了蜗轮蜗杆精密转台的主要误差源,为后续的误差设计和精度分配提供了坚实的理论支撑,促进了精密转台的产业化应用。

汽车EPS斜齿轮蜗杆传动优化设计研究

基于现代先进汽车电动助力转向(Electric Power Steering,EPS)系统对转向传动的特殊要求,传动平稳、噪声小、成本低的尼龙斜齿轮钢蜗杆传动得到大量应用,但由于其材料特殊,传统的蜗轮蜗杆设计方法准则并不适用。通过分析尼龙斜齿轮钢蜗杆传动的特殊情况,综合考虑性能、结构、成本等因素,借助Kisssoft软件对给定条件下的斜齿轮蜗杆传动机构的结构参数、安全系数进行了设计分析;按照易加工、不失效、等强度的原则,提出了其合理变位系数的取值及斜齿轮蜗杆各参数的设计方法,并利用Workbench软件对设计出的模型进行了仿真验证。结果表明,优化后的尼龙斜齿轮钢蜗杆传动满足设计要求,综合性能较优。

银锭浇铸装置自动化改造及应用

文章介绍了银锭浇铸装置的工作原理及现场使用存在的问题,通过对问题的分析确定了改造措施。经过改造后,浇铸装置实现了由原有的手动操作蜕变成了自动化操作,降低了操作人员的劳动强度,避免了浇铸银锭时,温度高达1000℃的高温溶液对操作人员的高温辐射伤害,同时,提高了浇铸装置的自动化水平,生产效率也大幅提升。

多模数ZI蜗杆斜齿轮传动设计与有限元分析及其应力预测

为解决传统渐开线蜗杆斜齿轮副在开式传动或传动比过大时斜齿轮容易发生齿根断裂的情况,提出一种新型的基于不等模数不等压力角设计的渐开线蜗杆副,使斜齿轮的模数与压力角同时提高,大幅提高斜齿轮的齿根强度。通过对此种蜗杆副的传动特性的分析,得到特殊的啮合角与中心距计算方式。另外,通过对同传动比、同蜗杆情况下基于不等模数设计的ZI蜗杆斜齿轮副和传统ZI蜗杆斜齿轮副的建模与有限元分析,得出在较大模数比情况下的斜齿轮齿根强度约为传统斜齿轮齿根强度的2.956倍,增大了渐开线蜗杆的应用范围。后续使用灰色预测,对比出误差平方和(Sum of Squared Errors,SSE)最小模型,予以验证预测的准确性,另外进行蜗杆施加不同转矩下的斜齿轮啮合齿受拉力处最大应力σ_(1max)的数据预测,为相应的工程分析与必要的校核设计给出了依据。

一种基于网状关联分析的网络蠕虫预警新方法

通过对网络蠕虫行为模式的分析,提出一种基于网状关联分析的网络蠕虫预警的新方法,并设计了预警算法,建立了网络蠕虫预警模型和基于预警算法的原型系统,最后给出相关实验数据和分析结果。与现有的网络蠕虫检测方法相比校,新方法更加有效,而且能够预警未知的网络蠕虫。

旋毛虫成虫cDNA文库免疫筛选及序列分析

目的 为获得旋毛虫成虫抗原基因。 方法 应用免疫血清和人工感染血清对旋毛虫成虫cDNA文库进行免疫筛选、克隆测序及核苷酸序列数据库 (GenBank)查寻比较 ,采用DNAstar软件进行基因序列分析。 结果 免疫筛选成虫cDNA文库 ,获得 9个阳性克隆。对其中的Ts87进行测序 ,又采用 5′ RACE ,获取全长为 1172bp的cDNA片段 ,该基因编码 3 47个氨基酸。序列分析表明 ,克隆Ts87是个尚未见报道的旋毛虫基因序列 ,存在预测的抗原表位。 结论 获得具有抗原性的旋毛虫抗原新基因。

大豆对斜纹夜蛾抗性的遗传分析及相关QTL的定位

以大豆组合皖82-178×通山薄皮黄豆甲衍生的重组自交系群体(RIL)为材料,以斜纹夜蛾幼虫重为抗性鉴定指标,应用主基因+多基因的混合遗传模型对大豆抗虫性进行遗传分析。结果表明,该群体对斜纹夜蛾的抗性遗传符合两对主基因+多基因的混合遗传模型,主基因的遗传率为89.85%。以该群体构建的遗传连锁图谱为基础,利用软件CartgrapherV.2.0采用复合区间作图法检测到2个与抗虫有关的QTL,分别位于wt-11和wt-12连锁群上,其在对应连锁群的端距离分别为5.51cM和11.51cM,加性效应估计值分别为-0.0619和-0.0419,对性状变异的解释率分别为17.22%和8.60%。

基于坐标检测的蜗杆齿形精密测量分析

分析了几种常见蜗杆类型与测量有关的参数计算方法,阐述了测量蜗杆齿形时干涉误差产生的原因和计算方法。分析计算结果表明:对渐开线蜗杆,其测量干涉误差值为0;对法向直廓蜗杆和阿基米德蜗杆,其测量干涉误差值随蜗杆螺旋线升角的增大而急剧增加,愈接近蜗杆齿根,干涉误差值愈大。因而提出用坐标测量系统测量精密蜗杆齿形时,应根据实际蜗杆螺旋面参数及探头参数计算不同测量点的干涉误差值,并消除其对测量结果的影响。