Quasi-Static and Dynamic Behaviors of Helical Gear System with Manufacturing Errors

Time?varying mesh stiffness(TVMS) and gear errors include short?term and long?term components are the two main internal dynamic excitations for gear transmission. The coupling relationship between the two factors is usually neglected in the traditional quasi-static and dynamic behaviors analysis of gear system. This paper investigates the influence of short?term and long?term components of manufacturing errors on quasi?static and dynamic behaviors of helical gear system considering the coupling relationship between TVMS and gear errors. The TVMS, loaded static transmission error(LSTE) and loaded composite mesh error(LCMS) are determined using an improved loaded tooth contact analysis(LTCA) model. Considering the structure of shaft, as well as the direction of power flow and bearing location, a precise generalized finite element dynamic model of helical gear system is developed, and the dynamic responses of the system are obtained by numerical integration method. The results suggest that lighter loading conditions result in smaller mesh stiffness and stronger vibration, and the corresponding resonance speeds of the system become lower. Long?term components of manufacturing errors lead to the appearance of sideband frequency components in frequency spectrum of dynamic responses. The sideband frequency components are predominant under light loading conditions. With the increase of output torque, the mesh frequency and its harmonics components tend to be enhanced relative to sideband frequency components. This study can provide effective reference for low noise design of gear transmission.

Effect of Manufacturing Errors on Static Characteristics of Externally Pressurized Spherical Air Bearings

Externally pressurized spherical air bearings are the key component of the three-axis air bearing table, and the manufacturing errors of the bearing affects the performance of the air bearing table. However, the manufacturing errors are unavoidable, and the pursuit to enhance the manufacturing accuracy will increase the cost greatly. In order to provide some theoretical guideline for the tolerance choice in the design of the externally pressurized spherical air bearings with inherent compensation, the effects of several manufacturing errors on the static characteristics of the air bearing are studied. Due to the complex geometry of the computational domain, an unstructured meshing technology is used for mesh generation. A finite-volume method is adopted to discretize the three-dimensional steady-state compressible Navier-Stokes equations. A modified SIMPLE algorithm which is suitable for compressible flows is applied to solve the discretized governing equations. The effects of the dimension error and the roundness error of the ball head and the ball socket on the static characteristics are investigated. The investigation result shows that the positive dimension error and the oblate spheroid-type roundness error of the ball head as well as the negative dimension error and the prolate spheroid-type roundness error of the ball socket can improve the bearing capacity and static stiffness of the air bearings by reducing the mass flow. The calculation method proposed in this paper fits well for the general principle, which can be extended to the characteristics analysis of other air bearings.

Locating Error Considering Dimensional Errors Modeling for Multistation Manufacturing System

Multistation machining process is widely applied in contemporary manufacturing environment. Modeling of variation propagation in multistation machining process is one of the most important research scenarios. Due to the existence of multiple variation streams, it is challenging to model and analyze variation propagation in a multi-station system. Current approaches to error modeling for multistation machining process are not explicit enough for error control and ensuring final product quality. In this paper, a mathematic model to depict the part dimensional variation of the complex multistation manufacturing process is formulated. A linear state space dimensional error propagation equation is established through kinematics analysis of the influence of locating parameter variations and locating datum variations on dimensional errors, so the dimensional error accumulation and transformation within the multistation process are quantitatively described. A systematic procedure to build the model is presented, which enhances the way to determine the variation sources in complex machining systems. A simple two-dimensional example is used to illustrate the proposed procedures. Finally, an industrial case of multistation machining part in a manufacturing shop is given to testify the validation and practicability of the method. The proposed analytical model is essential to quality control and improvement for multistation systems in machining quality forecasting and design optimization.

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.

TWO-COORDINATE DUAL-SERVO CONTOURERROR COMPENSATION TECHNOLOGY FOR ULTRA-PRECISION MANUFACTURING

A technology of two-coordinate dual-servo(TCDS) is proposed. Using this technology which is based on error compensation, workpieces of higher contour accuracy could he turned on ultra-precision machine tool with Poor dynamic performances. The principle, constitute and operation of a TCDS system are described. Mathematical proof and experiments are achieved in addition.

Attitude Optimization Algorithm of GFIMU with Installation Errors

Taking the accelerometer installation errors into consideration, the attitude optimization algorithm of Gyro Free Inertial Meastement Unit （GFIMU） is studied in the high spinning condition in this paper. A ten-accelerometer configuration is designed so as to establish a mathematical model to acquire the angular speeds in the case of installation errors. Precision of the algorithm is evaluated by using damping GaussNewton method. A large amotmt of sinmlation results show that ff the accelertlmter＇s angleinstallation errors main-tain small （〈5°）, the errors of attitude angles can be limited within ±1°. Hence, the algorithm has a great applicable value in engineering.

Influence of Bed Temperature on Heat Shrinkage Shape Error in FDM Additive Manufacturing of the ABS-Engineering Plastic

In case of manufacturing hexahedral ABS (Acrylonitrile Butadiene Styrene) plastic components using a FDM (Fused Deposition Modeling)-based 3D printer, undesirable shape errors occur in the product due to heat shrinkage. This paper experimentally ob-served the influence of the bed temperature change on the deformed shape errors of a hexahedral specimen of 100 × 50 × 50 mm3 produced by using a 3D printer. During printing work, the head nozzle temperature was kept at 240?C and the head speed was set at 50 mm/s. The chamber was enclosed with a PC-plate. 3D printing was conducted at four different bed temperatures;50?C, 70?C, 90?C, and 110?C. After the produced specimens naturally cooled down to room temperature, their deformed shape errors were measured. As a result, the higher the bed temperature, the lower the deformed shape errors of the specimens were. However, if the bed temperature had exceeded 120?C, laminating adhesion became poor. That seems to occur because of the material phase change and can make 3D printing work very hard as a consequence. Results of this study can be helpful to set optimum bed temperature condition in FDM additive manufacturing.

A New Finite Element Model with Manufactured Error for Additive Manufacturing

Additive manufacturing(AM),adding materials layer by layer,can be used to produce objects of almost any shape or geometry.However,AM techniques cannot accurately build parts with large overhangs,especially for the large features close to horizontal,hanging over the void.The overhangs will make the manufactured model deviate from the design model,which will result in the performance of the manufactured model that cannot satisfy the design requirements.In this paper,we will propose a new finite element(FE)analysis model that includes the manufacturing errors by mimicking the AM layer by layer construction process.In such FE model,an overhang coefficient is introduced to each FE,which is defined by the support elements in the lower layer.By mimicking the AM process from the bottom layer to the top layer,all the FE properties are updated based on their overhang coefficients,which makes the computational model be able to predict the manufactured model with manufacturing errors.The proposed model can be used to predict the performance of the AM objects in the design stage,which will help the designers to improve their design by the simulation results.

Calibration and compensation methods of installation error of electronic compass

Installation error angle is one of the factors that affect the accuracy of electronic compass used for geomagnetic navigation.To solve this problem,the calibration and compensation methods for installation error angle are studied.By analyzing the generation mechanism of installation error angle of electronic compass,an installation error model is established,compensation formulae are derived,and calibration scheme is proposed.To verify the correctness of the calibration and compensation methods,the verification experiment is conducted by computer simulation.The simulation results show that the proposed calibration and compensation methods are effective and practical.

Investigation of stress distribution and damage behavior caused by forced installation of a composite bolted joint with a hole-location error

In this paper,the influence of forced installation caused by a hole-location error on the 3D stress distribution and damage of a composite bolted joint is investigated.An analytical model of stress distributed on composite holes is promoted,in view of non-uniform extrusion caused by forced installation.At first,non-uniform extrusion of the hole edge caused by forced installation is analyzed.According to the contact state,expression of hole deformation is given.Then,based on Hertz theory,the maximum extrusion load is obtained with help of deformation expression.By constructing an elastic foundation beam model,3D stress distributed on a hole could be analyzed according to the extrusion load.Then,stress distribution predicted by the above analytical method is compared with that provided by FE considering composite damage.Finally,a forced installation experiment is carried out to analyze the damage distribution of the joint.Results show that a central-symmetrically distributed stress is introduced by the hole-location error.With an increment of the error,strength of composite decreases due to extrusion damage.Therefore,stress presents a concave distribution on the hole.As the hole-location error exceeding 3%,stress decreases gradually due to failure of composite.Damage of holes does not exhibit a centrosymmetric distribution.Serious damage is mainly distributed on the entrance of the hole at the lower sheet.

Practical Calculation of Thermal Deformation and Manufacture Error in Surface Grinding

The paper submits a method to calculate thermal deformation and manufacture error in surface grinding. The author established a simplified temperature field model, and derived the thermal deformation of the ground workpiece. It is found that there exists not only a upwarp thermal deformation, but also a parallel expansion thermal deformation. A upwarp thermal deformation causes a concave shape error on the profile of the workpiece, and a parallel expansion thermal deformation causes a dimension error in height. The calculations of examples are given and compared with presented experiment data.

Smooth Operation with Manufacture Error and Modification of Cycloidal Pin Gearing

The paper considers the modification or the manufacture error of cycloidal gear, then analyzes the relationship of pin circle meshed with the modified cycloidal gear, discuases the amount of error that leads to destroying conjugate action and results in the changes of tbe instantaneous velocity ratio and so as to affect the smooth operation of cycloidal pin gearing. The idea of the relationship between amount of modification aud manufacture error and the smooth operation can be gotten from the curve diagrams of the instantaneous velocity ratio. Therefore, the directions for improving the reature of the cycloidal pin gear transmission are clear.

Effect of Measurement Error on the Multivariate CUSUM Control Chart for Compositional Data

Control charts(CCs)are one of the main tools in Statistical Process Control that have been widely adopted in manufacturing sectors as an effective strategy for malfunction detection throughout the previous decades.Measurement errors(M.E’s)are involved in the quality characteristic of interest,which can effect the CC’s performance.The authors explored the impact of a linearmodel with additive covariate M.E on the multivariate cumulative sum(CUSUM)CC for a specific kind of data known as compositional data(CoDa).The average run length(ARL)is used to assess the performance of the proposed chart.The results indicate that M.E’s significantly affects themultivariate CUSUM-CoDaCCs.The authors haveused theMarkov chainmethod to study the impact of different involved parameters using six different cases for the variance-covariance matrix(VCM)(i.e.,uncorrelated with equal variances,uncorrelated with unequal variances,positively correlated with equal variances,positively correlated with unequal variances,negatively correlatedwith equal variances and negatively correlated with unequal variances).The authors concluded that the error VCM has a negative impact on the performance of themultivariate CUSUM-CoDa CC,as the ARL increases with an increase in the value of the error VCM.The subgroup size m and powering operator b positively impact the proposed CC,as the ARL decreases with an increase in m or b.The number of variables p also has a negative impact on the performance of the proposed CC,as the values of ARL increase with an increase in p.For the implementation of the proposal,two illustrated examples have been reported formultivariate CUSUM-CoDaCCs inthe presence ofM.E’s.Onedealswith themanufacturingprocessof uncoated aspirin tablets,and the other is based on monitoring the machines involved in the muesli manufacturing process.

考虑制造误差和油膜作用力的齿轮敲击动力学分析

为准确评估变速器空套齿轮受角加速度激励的敲击表现,采用集中参数法建立了模拟变速器敲击台架试验的10自由度扭转动力学模型;在包含时变啮合刚度、间隙非线性和拖曳力矩的基础上,进一步考虑齿轮制造误差和润滑油膜作用力。敲击台架试验结果表明包含楔入和挤压效应的润滑油膜作用力模型能正确反映变速器的敲击响应;数值分析结果表明润滑油膜可以减少制造误差位移激励和时变啮合刚度参数激励产生的齿面敲击,敲击强度随制造误差幅值的增加呈凹函数变化,当制造误差的幅值增加到某一数值时,齿轮副在无角加速度激励时亦产生敲击现象。润滑油温度对敲击的影响与角加速度激励有关:无角加速度激励时,低温时较低幅值的齿轮低频圆周误差通过改变油膜作用力方向产生敲击;油膜作用力产生的敲击响应频率比齿面接触的敲击响应频率更低;当存在角加速度激励时,敲击强度随温度的升高呈凸函数增加。

衍射仪的机械制造误差对拟合可信度极限的影响

全谱结构拟合是获得研究对象精细结构的一种重要方法,X射线多晶衍射仪测试的角度准确度直接影响全谱结构拟合的正确性和可信度,而测角仪的机械制造误差是影响测量角度准确度不可忽视的因素。该文采用模拟计算方法对由蜗轮蜗杆系统的制造误差造成的X射线多晶衍射全谱拟合结果的可信度进行了分析,结果表明对theta-theta衍射仪而言,机械制造的角度准确度至少要达到±0.003°,拟合结果才是有可信度的,所以只有采用直接在衍射仪轴上安装有高准确度的圆光栅的方式,才能提供符合当前物质结构分析的要求。该文具体给出了圆光栅的准确度要求。

真空环境下小孔节流径向气浮轴承特性研究

单轴气浮台中的涡流力矩主要是由径向气浮轴承的制造误差引起的。采用CFD软件首先研究了真空环境对小孔节流径向气浮轴承的承载力、耗气量的影响规律,其次对比研究了真空环境下简化和实测常见制造误差对涡流力矩的影响规律。在常压和真空环境下,进、出口压力差相同时,常压环境下静态承载能力优于真空环境;当出口压力逐渐越接近真空时,承载力下降趋势更加突出;在真空环境下的平均耗气量要比常压下小。对简化的制造误差进行分析时,涡流力矩出现正弦周期性变化,其峰值出现规律与制造误差的相对位置有关。依据实际误差测量数据进行建模分析,发现涡流力矩在一定范围内波动,这是轴颈制造误差与节流孔直径制造误差共同作用的结果,峰值数量和位置与节流孔的数量和相对位置一致,且节流孔直径制造误差也会对峰值时的涡流力矩结果产生影响。

基于CREAM方法的海上风机安装人因可靠性评估

采用认知可靠性和差错分析法(Cognitive Reliability and Error Analysis Method,CREAM)对固定式海上风机安装作业的人因可靠性进行评估,并引入结构熵权法和马尔可夫方法对传统CREAM进行改进,实现人因差错概率、平均人为差错时间等人因可靠性指标的定量计算。在充分结合现实条件的情况下,考虑海上风机安装的天气、海浪和操作水平等环境和人为因素的影响,针对固定式海上风机安装作业的要求和特点,结合作业人员可靠性评估结果,从操作素质、组织管理、环境改善等方面提出发展建议。

光学元件磁流变加工不确定度误差工艺方法

为减少磁流变抛光过程中误差对加工精度的影响,实现光学元件磁流变高精度加工,采用一种不确定度误差工艺方法对加工中的误差进行抑制。通过对磁流变加工过程中的位置误差和去除函数误差进行不确定度分析,在理论分析与实验分析的基础上进行验证实验。由仿真与实验结果可知,加工中面形误差与中频误差均存在3.5 nm的不确定度误差值,通过验证实验,得到了加工后的面形误差RMS值为20 nm,中频误差RMS值为14 nm。结果表明,采用误差不确定度的方法可优化加工工艺流程,减少误差对加工过程的影响,可以达到不确定度下的面形精度。该方法为磁流变高精度确定性加工以及面形误差与中频误差的抑制问题提供了一种解决方案。

大行程位移台干涉测距系统的误差补偿

双频激光干涉仪作为常用的精密光学非接触式测量设备,具有精度高、抗干扰能力强、灵活性好等优点。然而环境温度变化、机械振动等因素可能会影响其测量结果的准确性,并且影响程度会随着测量光程的增加而增大。针对基于双频激光干涉仪的大行程位移台测距系统,首先研究了位移台测距系统的测量原理,然后针对系统存在的各项误差进行了分析和补偿,最后,对系统进行综合误差补偿实验,短时间补偿量达到10-8 m量级,且时间越长补偿效果越好。该方法较现有的误差补偿方法更为完整,补偿量更大。

叶片加工误差对压气机性能影响研究综述

叶轮叶片在实际加工过程中会难免出现误差,从而导致实际叶轮与理论设计叶轮产生性能差异。基于叶轮叶片轮廓度及粗糙度加工误差,研究不同类型误差对压气机性能影响。首先,分析不同轮廓度偏差形态对压气机性能影响,以及不确定性分析、低速模拟等各种研究方法探究,实现加工误差对压气机性能影响的真实判断,并指出局部轮廓度加工误差,需特别关注叶轮叶片前缘部分对压气机性能影响。其次,叶片表面粗糙度误差则需根据实际设计情况、加工成本确定精度范围。综合考虑各种影响因素,而后在设计过程中,使用误差补偿技术有意识调整,从而降低加工误差对压气机性能的影响。