基于数据拟合的加荷速率测量算法

加荷速率是材料试验过程中的一个重要控制参量。当存在噪声时，加荷速率能否准确测量将直接影响控制过程与试验质量。中提出基于数据拟合的加荷速率测量算法，通过拟合的直线方程求其斜率得到加荷速率，使该算法具有良好的抑制噪声能力，提高了加荷速率的测量精度，保证了控制系统的稳定性和材料试验的质量。误差分析、仿真与实际应用都证明了这一结论。     

轴线不平行度对人字齿轮齿面啮合性能的影响分析

人字齿轮传动由于加工安装误差、轴承支撑布置无法对称等条件,不可避免会产生轴线的微量不平行。因人字齿轮齿宽较大、啮合刚度高、标准渐开线齿面线接触等特点,微量的轴线不平行度就会导致严重的齿面偏载,影响齿轮传动的平稳性和可靠性。因此,采用了小轮较大轴向浮动的轴承支撑结构,并研究了小轮轴向浮动的人字齿轮齿面承载接触仿真(LTCA)方法,通过大、小轮轴向固定和小轮轴向浮动两种不同轴承支撑结构的仿真比较,说明小轮轴向自位浮动可以有效改善齿面偏载,为人字齿轮传动系统的设计提供了参考。     

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 convenient 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.     

Digital twin modeling for loaded contact pattern-based grinding of spiral bevel gears

To distinguish with the conventional tooth flank grinding only considering geometric accuracy, an innovative digital twin modeling is proposed for loaded contact pattern based grinding of spiral bevel gears. Where, data-driven grinding simulation, sensitivity analysis strategy, adaptive decision and control are developed. Focusing on loaded contact pattern optimization, numerical loaded tooth contact analysis (NLTCA) considering noncentrosymmetric problem and tooth flank roughness is developed for data-driven relationship establishment. Then, an adaptive data-driven tooth flank grinding decision and control model is established. Where, the universal motion concept (UMC) machine settings is selected as the optimal design variable. It is actually an infinite approximation to the target tooth flank in form of an adaptive control system. Moreover, with point-to-point material removal distribution, the different optimization strategies are proposed for accurate tooth flank grinding. In particular, the overcutting problem on the tooth flank grinding programming is investigated. Finally, Levenberg-Marquardt method is applied to solve the established nonlinear lease square model for the accurate machine tool settings having modification variations. Thus, this accurate data-driven digital twin modeling can achieve loaded contact pattern-based grinding. The provided numerical and test instances can verify the proposed digital twin modeling.     

Analysis on Isothermal Elastohydrodynamic Lubrication of Orthogonal Face Gear

Face-gear drives have been applied in aviation transmissions, in particular, helicopter transmissions, and the lubrication characteristics are an important indicator for estimating the load-carrying capacity of face-gear teeth. In order to analyze the lubrication performance of the face gear under load, equations for the contact path of the face gear loaded tooth contact analysis (LTCA) were established on the basis of the load equivalent error of alignment (LEEA) and the load distribution among the teeth was calculated. Then a method for calculating the contact area and tooth surface velocity of face-gear drives was studied. Face-gear isothermal elastohydrodynamic lubrication (EHL) dimensionless equations are presented. A multigrid algorithm was used to complete the solution of the minimum film thickness and film pressure of face-gear drives. The lubricant film thickness and film pressure variation in the mesh cycle are expressed using example calculations that provide a theoretical basis for face-gear lubrication design.     

加载测向天线阵列的统一网络模型研究

该文首先建立联系天线阵元和加载网络的统一网络模型,把路与场统一于广义矩阵型欧姆定律之中。基于统一网络模型理论,采用矩量法(MoM)分析了加载匹配补偿网络的五元圆形测向天线阵列(FCADF)。研究表明,电路网络的加载,引入了新的路与场相互作用,可有效补偿天线单元之间的互耦影响,改善方向图不圆度特性,并实现阻抗匹配,从而提高了测向精度。此外,测向天线阵列中的局域谐振现象,通过加载网络也被有效抑制。     

金属切削机床基础的设计

介绍了金属切削机床基础设计的步骤和要点,并阐述了基础设计的重要性。     

基于误差的摆线锥齿轮动态加载接触分析方法(上)

基于摆线齿锥齿轮轻载接触分析，考虑齿轮副弹性变形、支承系统变形、制造安装误差及机床调整参数误差等因素，建立起一套在载荷作用下考虑误差的针对摆线锥齿轮副的加载接触分析方法，可以求解齿轮副承载传动时的真实接触区、运动误差曲线、载荷分配等关键指标，并进行了仿真实例计算。     

The control of diameter of carbon nanotube over Co-loaded Zeolite Y

This study examined carbon nanotubes (CNTs) with various outer diameters produced by the catalytic decomposition of acetylene over Co-loaded zeolite Y. The CNTs were grown at differed reaction temperatures, reaction times, and acetylene concentrations. In addition, the effect of the amount of Co dispersed over zeolite Y used as a support was determined. The shape and diameter of the synthesized CNT were identified by SEM and TEM analyzers. As a result, CNTs with various outer diameters were synthesized successfully. The average outer diameter of the synthesized CNTs increased with increasing amount of Co dispersed over zeolite Y regardless of the reaction temperature and reaction time. The outer diameter did not change with acetylene concentration, and the acetylene concentration was fixed to 10 cm³/min. Most of the CNT had large surface areas, >400 m²/g. The surface area increased with increasing outer diameter of the CNT until the outer diameter reached 60 nm but decreased with further increases in outer diameter.     

高负荷氦气压气机的气体流动特点与改型设计

从氦气工质的特点入手,分析了氦气压气机设计参数选取区别于以空气为工质的压气机的特殊之处,重点分析了提高氦气压气机负荷的参数选择特点.由于氦气热物性与空气差别较大,气流经过压气机时的马赫数通常较低,造成单级压比较低,所以,氦气压气机的通流尺寸通常变化较小.为了提高单级负荷,减少压气机级数,需提高各级反动度.本文以多级氦气压气机为例,通过数值模拟分析了该压气机的三维流动特点,并进行了改型设计.