扭转刚度对双输入圆柱齿轮分流传动系统动力学均载系数的影响

建立了双输入圆柱齿轮分流传动系统的弯扭耦合动力学模型,模型中考虑了各齿轮副间的时变啮合刚度、齿侧间隙、啮合误差、啮合阻尼等因素.结合闭环结构特点,利用齿轮啮合线的相对位移和传动轴扭转位移消除方程中的刚体位移.采用4阶Runge-Kutta法求解系统动力学方程,获得了系统均载系数.结果表明:系统均载系数受输入轴扭转刚度影响小;分流级和并车级均载系数对双联齿轮轴的扭转刚度敏感,减小双联齿轮轴的扭转刚度可以改善系统的均载性能,当双联齿轮轴的扭转刚度小于1.1×105（N·m）/rad时,可将系统均载系数控制在1.06以内;输出轴扭转刚度的变化对分流级和并车级均载系数基本没有影响.      

单元体结构发动机总体结构尺寸控制与分析

在单元体结构发动机中,在各小的维修单元体或大的单元体内部,通过逐级控制一些关键尺寸,来满足单元体本身互换性要求,同时满足发动机总体结构设计的要求,这也是单元体发动机设计和装配中需重点关注的问题。以国外某发动机为例,通过尺寸链的分配和必要时在内部设置调整环,使单元体内部的这些关键的总体结构特征尺寸达到一定的精度要求,贯穿至发动机总体结构设计和协调、传装及总装装配的各环节中,使发动机总体结构尺寸如转、静子轴向间隙等更加合理可靠,避免发生干涉等问题。     

Numerical investigation of windage heating within shrouded rotor-stator cavity system with central inflow

The rotating disk surface temperature rise due to windage heating effect by numerically modeling the turbulent flow within a rotor-stator cavity which is available with a peripheral shroud and imposed through airflow was dealt with. The windage heating may be defined as viscous friction heating caused by relative velocity differences across the boundary layers between the fluid and the rotating disk surface. The kinetic energy dissipation process could transform the rotating shaft power into thermal heating. Commercial finite volume based solver, ANSYS/CFX was employed to numerically simulate this physical process by using the shear stress transport (SST) turbulence model. CFD results include the rotating disk surface temperature axial distribution and tangential velocity distribution of the fluid domain. The velocity difference between the result obtained by particle image velocimetry (PIV) experiments and CFD simulation are within 5%. The adiabatic disk temperature rise can be calculated by the tangential velocity of disk and fluid in large gap ratio and turbulent parameter. CFD temperature distribution results and those estimated via velocity differences are within 10%.     

叶栅安装角异常的非定常流场数值模拟

采用商用软件NUMECA对叶栅安装角异常进行二维流场定常和非定常数值模拟,并进行对比分析,得到了因叶栅安装角异常造成通道堵塞对该叶片以及相邻叶栅通道流场结构和非定常气动力的影响.结果表明:安装角异常角度大于0°时,主要对沿吸力面方向叶栅通道流场结构影响较大,随着安装角异常角度的增大,气流不断恶化,出现大面积的附面层分离,尾涡脱落主频率随着安装角异常角度的增大而减小,次频率随着安装角异常角度的增大而增大;并导致叶片非定常气动力相对脉动量迅速增大,这可能是导致叶片疲劳破坏的原因之一.     

A fuzzy PID-controlled SMA actuator for a two-DOF joint

Shape memory alloy(SMA) actuator is a potential advanced component for servosystems of aerospace vehicles and aircraft. This paper presents a joint with two degrees of freedom(DOF) and a mobility range close to ±60 when driven by SMA triple wires. The fuzzy proportional-integral-derivative(PID)-controlled actuator drive was designed using antagonistic SMA triple wires, and the resistance feedback signal made a closed loop. Experiments showed that, with the driving responding frequency increasing, the overstress became harder to be avoided at the position under the maximum friction force. Furthermore, the hysteresis gap between the heating and cooling paths of the strain-to-resistance curve expanded under this condition. A fuzzy logic control was considered as a solution, and the curves of the wires were then modeled by fitting polynomials so that the measured resistance was used directly to determine the control signal. Accurate control was demonstrated through the step response, and the experimental results showed that under the fuzzy PID-control program, the mean absolute error(MAE) of the rotation angle was about 3.147. In addition, the investigation of the external interference to the system proved the controllable maximum output.     

A numerical model for bird strike on sidewall structure of an aircraft nose

In order to examine the potential of using the coupled smooth particles hydrodynamic(SPH) and finite element(FE) method to predict the dynamic responses of aircraft structures in bird strike events, bird-strike tests on the sidewall structure of an aircraft nose are carried out and numerically simulated. The bird is modeled with SPH and described by the Murnaghan equation of state, while the structure is modeled with finite elements. A coupled SPH–FE method is developed to simulate the bird-strike tests and a numerical model is established using a commercial software PAM-CRASH. The bird model shows no signs of instability and correctly modeled the break-up of the bird into particles. Finally the dynamic response such as strains in the skin is simulated and compared with test results, and the simulated deformation and fracture process of the sidewall structure is compared with images recorded by a high speed camera. Good agreement between the simulation results and test data indicates that the coupled SPH–FE method can provide a very powerful tool in predicting the dynamic responses of aircraft structures in events of bird strike.     

直升机蜂窝夹层结构缺陷验收准则验证技术研究

蜂窝夹层作为一种特殊的复合材料结构,具有比强度、比刚度较高,性能易设计且便于大尺寸整体成型等诸多优点,广泛应用在航空器的结构设计中。但蜂窝夹层结构在制造、使用和维护过程中易出现脱／漏粘、冲击、磕碰等内在缺陷或外来损伤,可能导致结构强度的降低,从而危及结构安全。基于强度理论制定了一种直升机蜂窝夹层结构的静强度、疲劳强度和剩余强度综合验证思路与方法。针对典型结构的构型、缺陷类型和工程可检缺陷参数尺寸,设计了模拟真实蜂窝夹层结构的验证样件和缺陷预制技术,通过强度性能的试验和研究,获得了带有脱／漏粘缺陷、冲击／磕碰损伤等缺陷的结构强度缺陷容限值,为其缺陷验收准则的制定提供了技术依据。     

基于数控切齿的弧线齿面齿轮啮合特性研究

研究了弧线齿面齿轮的数控切齿及其啮合特性.基于假想产形齿轮的概念,同时考虑了刀具法向截面的修形,推导弧线齿面齿轮的齿面方程;以坐标变换为工具,建立其机床加工模型,确定各运动轴的多项式表达式;在此基础上,建立了考虑安装误差的弧线齿面齿轮副接触分析模型.计算结果表明:通过面齿轮的齿面修形,可以降低啮合转换点处的传动误差幅值,并获得较好的传动误差曲线.      

基于ANSYS的整体叶盘结构优化设计

为保证整体叶盘结构在安全工作条件下质量最轻,基于ANSYS优化平台,建立了整体叶盘三维参数化模型及结构优化设计数学模型,完成了整体叶盘结构的优化设计.首先结合相关静强度设计准则及方法,在给定轮缘分布载荷条件下对轮盘子午面进行优化.然后建立整体叶盘三维模型,并对子午面优化中未考虑的轮缘关键尺寸如轮缘厚度、喉道倒角、叶根倒角进行三维局部优化.在三维优化中总结出了盘喉道和叶根最大等效应力与各优化参数之间的关系.分两步实施的整个轮盘优化过程仅需3~4h.      

一种提高UDP可靠性的数据传输方法研究

针对传统的UDP协议数据传输效率高但可靠性差的特点,提出了一种基于分区确认的分包与重组方法,使用自适应拥塞控制机制,并提出乘性增加减性减少（multiplicative increase reduced decrease,MIRD）算法对超时间隔进行处理,实现了音频数据的实时可靠传输,满足了特定场合下大量数据的传输实时性强和可靠性高的要求,提高了带宽利用的公平性和稳定性,拓展了UDP协议的使用范围。实验验证了该方法的可行性．音频数据传输的可靠性得到了提高。