大型直齿锥齿轮的铣削加工方法

直齿锥齿轮一般要在专用机床上加工 ,但能够加工大型直齿锥齿轮的生产企业极少。在龙门铣床上铣削加工大型直齿锥齿轮方法简单易行 ,加工精度能够满足一般使用要求 ,运行平稳。     

面向寿命终结阶段的机械产品设计绿色多准则优化

针对机械产品设计过程中通常考虑产品寿命终结阶段(End-of-life,EOL)报废处理过程的可拆卸性、再制造性、环保性等单个绿色质量因素影响,导致机械产品的回收拆解中可重用、回收零部件由于拆解过程费事、费力、经济性差无法回收重用或因回收重用价值不大导致零部件被直接废弃,造成严重的环境污染.从回收拆解作业效率、回收拆解...     

精密伺服机构微型齿轮啮合刚度的有限元辨识

基于微型齿轮重合度大的特点,首先利用齿轮啮合刚度、轮体刚度以及轮齿刚度间的串联关系,建立单齿啮合的有限元模型,计算出单齿啮合时齿轮的啮合刚度以及主、从动轮轮体刚度和轮齿刚度;再引入重合度的影响系数,得到微型齿轮的平均啮合刚度;进一步分析齿轮平均啮合刚度在中心距误差范围内的变化规律,发现当中心距从标准中心距处开始逐步减小时,齿轮平均啮合刚度缓慢增加;当中心距从标准中心距处开始逐步增大时,齿轮平均啮合刚度显著减小。     

Influence of tooth modifications on tooth contact in face-hobbed spiral bevel gears

In this study the influence of tooth modifications induced by machine tool setting and head-cutter profile variations on tooth contact characteristics in face-hobbed spiral bevel gears is investigated. The concept of face-hobbed spiral bevel gear generation by an imaginary generating crown gear is applied. The modifications of tooth surfaces are introduced into the teeth of both members. The lengthwise crowning of teeth is achieved by applying a slightly bigger radius of lengthwise tooth flank curvature of the crown gear generating the concave side of pinion/gear tooth-surfaces, and by the variation of machine tool settings in the generation of pinion/gear teeth. The ease-off in the tooth height direction of meshing tooth surfaces is achieved by applying a head-cutter whose profile consists of two circular arcs, instead of a straight-line. The method of tooth contact analysis applied determines the path of contact, the potential contact lines, the separations along these lines, and the transmission errors. A computer program implements the method. By using this program the influence of the variation of machine tool settings and of head-cutter geometry on tooth contact is investigated and discussed.     

透过运营数据看AMT的价值

变速箱正在走向自动变速,AMT作为一种省油的自动变速技术正在走向成熟。透过AMT公交样车载客运营基本数据,分析了AMT技术在整车经济性、可靠性、营运效率等方面的价值和优势,从而使得人们对AMT的价值判断更加全面、更加具有说服力。     

某齿轮传动系统生产基地工业设计加工部分

齿轮传动系统作为机械装备的动力传动主体及核心零部件,是国家鼓励发展的产业.详细地论述了某齿轮传动系统生产基地加工部分的工业设计.介绍了该基地建设设计中的主要产品加工工艺流程、主要加工设备选择等加工工艺设计关键技术.该基地已投入生产,技术设备先进,工艺布局合理,具有国内领先水平.     

Diagnosis of involutometric issues in flat rolling of external helical gears through the use of finite-element models

High-volume production of precision external-involute helical gears using flat-rolling is impeded by a number of quality issues. Experimental resolution of these issues is expensive and time consuming. The present study utilizes finite-element models (FEM) to diagnose three of these quality issues and to explore possible solutions. Two- and three-dimensional (2D and 3D) ABAQUS models were developed for a specific gear-manufacturing process and resulting geometries were not satisfactory. Subsequently, 3D DEFORM simulations were developed for the same process. Numerically predicted geometries were benchmarked against actual results obtained through designed experiments. Finite-element modeling and experimental results were correlated and the models were validated. Possible solutions were simulated and analyzed through additional modeling. Results obtained from the initial pass of the 3D models have been promising although progress has been limited by the excessive computational time needed. Frequency of re-meshing, high number of elements due to fine mesh, and changing re-mesh criteria contribute to the computational difficulties.     

FATIGUE CRACK GROWTH PREDICTION IN SPECIMENS SIMILAR TO SPUR GEAR TEETH

Abstract— The problem of fatigue crack propagation in surface treated specimens similar to gear teeth is analysed. Experimental fatigue tests were carried out on carburized, and carburized and shot peened, specimens. In order to predict crack propagation and to consider the effect of the treatments, different models of the cracked specimens were realized. Two numerical approaches were followed: the finite element method and the weight function technique. Two- and three-dimensional finite element models were constructed, and the stress-intensity factors were evaluated by considering the effect of both the load and the residual stresses due to the treatments. The agreement between these and those obtained through the weight function technique is good. The weight function approach was used directly in the computer software package (which allows crack propagation predictions) and considered the effects of hardness and residual stresses. The comparison between theoretical predictions and experimental results validated the approach followed.     

A multi-mesh MPM for simulating the meshing process of spur gears

A numerical scheme is presented to simulate the meshing process of spur gears, based on the material point method (MPM). To allow engagements at successive contact points and subsequent separation between neighboring gear teeth, a contact/sliding/separation procedure in a multi-mesh environment without using master/slave nodes is proposed so that the no-slip contact constraint inherent in the existing MPM can be released. Individual drive members rotate around corresponding axes, through which simulated angular velocity transmission is in good agreement with the analytical solution. It appears from the simulation results presented here that the multi-mesh MPM could become a robust spatial discretization tool for gear design problems that involve large rotation, contact/sliding and separation.     

Rim Thickness Effects on Gear Crack Propagation Life

Analytical and experimental studies were performed to investigate the effect of gear rim thickness on crack propagation life. The FRANC (FRacture ANalysis Code) computer program was used to simulate crack propagation. The FRANC program used principles of linear elastic fracture mechanics, finite element modeling, and a unique re-meshing scheme to determine crack tip stress distributions, estimate stress intensity factors, and model crack propagation. Various fatigue crack growth models were used to estimate crack propagation life based on the calculated stress intensity factors. Experimental tests were performed in a gear fatigue rig to validate predicted crack propagation results. Test gears were installed with special crack propagation gages in the tooth fillet region to measure bending fatigue crack growth. Good correlation between predicted and measured crack growth was achieved when the fatigue crack closure concept was introduced into the analysis. As the gear rim thickness decreased, the compressive cyclic stress in the gear tooth fillet region increased. The retarded crack growth and increased the number of crack propagation cycles to failure. This revised version was published online in August 2006 with corrections to the Cover Date.