Optimum design on lobe shapes of gerotor oil pump

A gerotor pump is suitable for oil hydraulics of machine tools, automotive engines, compressors, constructions and other various applications. In particular the pump is an essential machine element that feeds lubricant oil in an automotive engine. The subject of this paper is the theoretical analysis of internal lobe pump whose the main components are the two rotors. Usually the outer one is characterized by lobes with a circular shape, while the inner rotor profile is determined as a conjugate to the other. For this reason the first topic presented here is the definition of the geometry of the rotors starting from the design parameters. The choice of these parameters is subject to some limitations in order to limit the pressure angle between the rotors. Now we will consider the design optimization. The first step is the determination of the instantaneous flow rate as a function of the design parameter. This allows us to calculate three performance indexes commonly used for the study of positive displacement pumps: the flow rate irregularity, the specific flow rate, and the specific slipping. These indexes are used to optimize the design of the pump and to obtain the sets of optimum design parameter. Results obtained from the analysis enable the designer and manufacturer of the oil pump to be more efficient in this field.     

Influence of cylinder curvature on the maximum shear stress at contact

Analysis of the plane stress state of an elastic circular cylinder under coating pressure yields approximate dependences of the maximum shear stress (over the depth) on the cylinder radius. The applicability of classical Hertz–Belyaev solutions in the contact of elastic cylinders is investigated (in terms of the smallness of the contact area).     

高重合度行星齿轮系参数优化设计

高重合度齿轮设计参数较多,各参数的取值相互制约且均受各种约束条件的限制.研究了高重合度齿轮的实现方法,通过减小压力角、增大齿项高系数、增加齿数和改变变位系数等方法可获得高重合度.采用优化设计的方法,建立以体积最小和重合度最大的多目标优化模型,设计了高重合度行星齿轮传动系统.设计的高重合度行星齿轮传动系统结构紧凑,承载能力较强,传动较平稳.     

Fatigue design of various type spot welded lap joints using the maximum stress

Recently, a new issue in designing spot welded structures such as automobile and train car bodies is to predict an economical fatigue design criterion. One of the most typical and traditional methods is to use a ΔP—N_f curve. However, since the fatigue data on the ΔP—N_f curve vary according to the welding conditions, materials, geometry of joint and fatigue loading conditions, it is necessary to perform the additional fatigue tests for determining a new fatigue design criterion of spot-welded lap joint having specific dimension and geometry. In this study, the stress distributions around spot welds of various spot welded lap joints such as in-plane bending type (IB type), tension shear type (TS type) and cross tension type (CT type) were numerically analyzed. Using these results, the ΔP—N_f curves previously obtained from the fatigue tests for each type were rearranged into the Δσ -N _f relations with the maximum stresses at the nugget edge of the spot weld.     

回转窑剖分式滚圈结构设计与接触应力分析

针对目前回转窑整体式滚圈在铸造、运输、安装及拆卸等过程中存在的难度,提出设计剖分式滚圈的设想,以解决整体式滚圈存在的问题.在剖分式滚圈的基本结构尺寸与整体式滚圈尺寸相同的情况下,校核其滚圈的刚度、强度.通过分析滚圈受力以及破坏失效原因可知,接触应力是引起滚圈破坏的主要因素.运用ANSYS软件分析了滚圈分体相对于托轮位于不同位置时的受力情况,并以此来校核其设计是否合理.     

深沟球轴承钢球温度变形对最大接触应力的影响

根据热传导原理得出深沟球轴承钢球瞬态温度分布,利用热弹性理论得出钢球瞬态应力、应变及位移的解析解,计算了钢球热变形产生的等效温度载荷,用赫兹接触理论计算了钢球和轴承内外圈之间的最大接触应力。滚动轴承钢球温度随着时间增加趋于稳定,钢球外表面比中心温度升高快。轴承钢球径向和切向应力在温升开始时刻和球心附近变化剧烈,随着时间的增加趋于0。轴承钢球径向位移在温升开始时刻和球心附近变化剧烈,钢球各点的径向位移和半径呈线性关系。采用拟合公式计算不同工作温度下深沟球轴承内外圈最大接触应力误差小于3.98%。接触应力拟合公式为深沟球轴承的合理设计和选用提供依据。     

弹子排加压机构的等应力参数设计与有限元仿真

弹子排加压机构在重载车辆的全盘式机械制动器中应用广泛,弹子与弹子槽之间的接触状态受控于二者的几何参数,为了控制二者间的接触应力,提高系统的使用寿命,以分布半径不等的弹子排加压机构为研究对象,基于赫兹应力理论,以接触应力峰值均一化为目标,对弹子槽曲率半径进行了参数优化,并在ANSYS平台上进行了有限元仿真,验证了优化结果...     

Optimal contact design and allowable limit on spindle assembly of aluminum hot rolling process

Aluminum sheet ingots go through the hot rolling process to be converted into coils with a gauge suitable for the cold rolling process or plates. The top spindle, end coupling and slipper metal are main components of the hot roll process and used for transmission of rotational power with heavy-duty load. The top spindle connected to the motor and end coupling connected to the roller are combined with the slipper metal which acts as a bearing and joint. The contact surface between end coupling and slipper metal is subjected to stress concentration, and life cycles of slipper metal is reduced. This study aims to minimize the mechanical problems which might happen in the production process. The load condition for hot rolling processes is derived under load condition that is conducted for a hot rolling process under slipper metal combination types and operation situations. A structural analysis is performed by applying mechanical characteristics, combination type, and rotational boundary condition of top spindle, end coupling and slipper metal. Optimal design is performed for contact surface between end coupling and slipper metal. Interference analysis is studied to reduce the stress concentrations. Kinematics simulation is performed by applying the various combination type and dynamic boundary condition of the mill spindle assembly. The interference does not occur on the top spindle and slipper metal, so actual driving of the hot mill spindle assembly can operate in the normal operation condition.     

Enhancement of a simplified model for maximum stress prediction

A simplified model for rapid estimation of maximum subsurface stress was previously reported by the authors. That model was found to predict the upper bound of the maximum von Mises stress in each layer below any surface with good accuracy. In this work, the model is enhanced by quantifying the difference between the predicted upper bound and the maximum stress for a specific rough surface. This is done by evaluating stress predictions for real rough surfaces, sinusoidal surfaces, ideal textured surfaces, and real rough surfaces with imposed computer generated texture. The difference between the predicted upper bound and the surface-specific maximum stress is found to be related to that surface’s roughness. The origin of this relationship is investigated in terms of apparent contact area. The enhanced simplified model provides an efficient means of estimating maximum stress in rough surface contact.     

Optimising the design of textured surfaces for reducing lubricated friction coefficient

Under operating conditions which are unfavourable for lubrication, such as high load and low velocity, the use of textured surfaces significantly promotes the formation of a thick lubricant film and an improvement of the friction coefficient. This paper relates to the manufacture of textures using a photolithography and chemical etching process. Different surface geometries, texturing densities and depths were designed to analyse the influence of these parameters. The friction coefficient was measured in a ball‐on‐disc tribometer under different lubrication regimes, and the results have been used to develop an artificial neural network with texturing optimisation potential. © 2016 The Authors Lubrication Science published by John Wiley & Sons Ltd.     

基于MATLAB汽车发动机配气凸轮的型线设计与接触应力分析

在汽车发动机配气凸轮的型线设计过程中,通过选用合适型线函数,设定预期从动件运动边界条件,推导凸轮接触应力计算公式,进而通过MATLAB编程,可生成预设的从动件升程、速度、加速度和凸轮接触应力曲线。文中所涉及的MATLAB程序以期快速完成凸轮设计和分析凸轮接触应力为目的,应用此方法可显著提高配气凸轮设计的速度和精度,并为凸轮机构的优化提供理论依据。     

基于模糊遗传算法的二自由度PID控制器优化设计

针对一般遗传算法中交叉概率和变异概率存在的选择困难问题，利用模糊推理系统来自适应估计交叉概率和变异概率，提出了模糊遗传算法（FGAs），并用于二自由度PID控制器参数寻优设计。仿真和实验表明，所设计的二自由度PID控制器可以使系统同时具有良好的目标值跟随特性和干扰抑制特性。     

基于模态分析的转鼓优化设计

利用Pro/Engineer建立离心机转鼓的实体模型和虚拟样机模型,在Abaqus环境下,采用有限元方法进行了模态分析,得到了转鼓的多阶固有振动频率、振型等参数值.根据仿真结果,分析了转鼓的危险位置和振型.提出以转鼓频响特性为优化设计目标,用Abaqud软件对转鼓进行模态分析与数据采样,得到25种方案的前6阶固有频率,用MATLAB软件对采样数据进行分析处理,得到转鼓系统优化设计的重点参数.为离心机结构设计提供有价值的理论参考.     

Principle of maximum entropy for reliability analysis in the design of machine components

Frontiers of Mechanical Engineering - We studied the reliability of machine components with parameters that follow an arbitrary statistical distribution using the principle of maximum entropy...     

Optimal design of multiple stress constant accelerated life test plan on non-rectangle test region

For optimal design of constant stress accelerated life test(CSALT) with two-stress, if the stresses could not reach the highest levels simultaneously, the test region becomes non-rectangular. For optimal CSALT design on non-rectangle test region, the present method is only focused on non-rectangle test region with simple boundary, and the optimization algorithm is based on experience which can not ensure to obtain the optimal plan. In this paper, considering the linear-extreme value model and the optimization goal to minimize the variance of lifetime estimate under normal stress, the optimal design method of two-stress type-Ⅰ censored CSALT plan on general non-rectangular test region is proposed. First, two properties of optimal test plans are proved and the relationship of all the optimal test plans is determined analytically. Then, on the basis of the two properties, the optimal problem is simplified and the optimal design method of two-stress CSALT plan on general non-rectangular test region is proposed. Finally, a numerical example is used to illustrate the feasibility and effectiveness of the method. The result shows that the proposed method could obtain the optimal test plan on non-rectangular test regions with arbitrary boundaries. This research provides the theory and method for two-stress optimal CSALT planning on non-rectangular test regions.     

Head and media design considerations for reducing thermal asperity

Recent use of magnetoresistive (MR)/giant-magnetoresistive (GMR) heads in disk drives requires tighter control on particle contamination that may generate thermal asperities at the head/disk interface. In this study, the effects of slider air bearing surface (ABS) design and media on TA reduction capability are investigated. The motion of particles at the head/media interface is simulated numerically. Drive level TA tests are performed using a particle injection chamber. It is observed that a new ABS design, that has an aerodynamic U-shaped rail and a central airflow passage, is beneficial in reducing the particle contamination on the slider. Scratch-resistance of the media surface is correlated to TA reduction capability of the media; more scratch-resistant media produced less TA. On the other hand, the adhesion properties of the media have minor effects on TA reduction, as the particles that usually generate TA in a drive are too small to spin off the media.     

Zinc oxythiomolybdate (ZnMoO2S2) powder as a solid lubricant for high-temperature rolling contact applications

Conventional liquid lubricants being used in today's gas turbine engines will not be able to operate effectively in the hostile bearing environments expected in future turbine engines. The expected high operating temperatures (500–800°C) mandate new and innovative lubrication schemes to achieve success. Recent studies have demonstrated that a new class of solid lubricants, the complex chalcogenides or metal ocythiomolybdates, have good potential for high temperature lubrication. This paper describes the friction, wear and rolling contact endurance of three high-temperature bearing materials using a zinc oxythiomolybdate (ZnMoO₂S₂) powder lubricant. Rolling contact tests were conducted using VIM-VAR M50, micromelt T15 tool steels and silicon nitride (Si₃N₄) at temperatures ranging from 23°C to 649°C, using a modified ball-on-rod type rolling-contact fatigue tester. Significant improvements in friction, endurance and wear were observed at all test temperatures, and with all three materials evaluated, when ZnMoO₂S₂ was used as a lubricant. Overall, silicon nitride exhibited the best frictional and antiwear performance. The lubricant powder exhibited the best tribological performance with T15 and M50 specimens between 177°C and 316°C. Energy Dispersive X-Ray Analysis (EDAX) of wear tracks showed the presence of iron (Fe) on the Si₃N₄ specimens as well as the presence of zinc (Zn) on both the T15 and the M50 specimens.     

Optimal torso design selection for dual 7-DOF robot arm using von Mises stress and workspace analysis

Journal of Mechanical Science and Technology - This paper presents a unique optimal torso design selection technique for the dual seven-degree-of-freedom robot arm. This optimal design enhances the...     

Optimal target selection for unbalanced tolerance design

In many manufacturing processes, unbalanced tolerance design is a common occurrence. It occurs when the deviation of a quality characteristic in one direction is more harmful than in the opposite direction. The failure mode in these two directions is usually different. Furthermore, automatic inspection and measurement technology are widely used by the industries. The non-conforming part will be detected automatically. Thus, a truncated asymmetrical quadratic loss function is assumed for the unbalanced tolerance design. Traditionally, the manufacturer would either choose the smaller tolerance as the tolerance for both sides, or would set the process mean at the middle of the tolerances. Both methods fail to minimise the expected quality loss. The purpose of this paper is to find out the optimal manufacturing setting such that the expected quality loss is minimised. The results show that the process mean should be shifted a little from the target value.