考虑运动副间隙的剪式线性阵列可展结构动力学分析

为了精确研究剪式线性阵列可展结构的动力学性能,在该机构的运动副中引入间隙,通过含间隙转动副元素之间的运动规律建立了该运动副的运动学模型。基于Gonthier接触力模型和修正的Coulomb摩擦力模型分别计算了含间隙转动副元素之间的法向与切向接触力。进一步把该接触力转换到间隙运动副所联接的杆件与滑块的质心处,并将其集成到剪式可展结构动力学模型的广义力中,从而成功地将关节间隙效应引入到可展结构中。采用一种新的违约校正法直接对系统的坐标和速度进行修正,避免了数值结果的发散并可确保将违约控制在给定的精度范围内。通过数值分析预测了运动副间隙对剪式线性阵列可展结构动力学性能的影响,为研究可展结构的运动精度和机构设计提供了参考和依据,拓展了间隙碰撞模型的应用范围,有利于工程实际应用。     

A330前登机／勤务门应急开门系统的一起特殊故障分析

通过分析前登机／勤务门的应急开门系统的原理,解析了实际工作中发生的因部件之间的间隙过大而引发的一起特殊故障。     

Tip-leakage flow loss reduction in a two-stage turbine using axisymmetric-casing contouring

In order to reduce the losses caused by tip-leakage flow, axisymmetric contouring is applied to the casing of a two-stage unshrouded high pressure turbine（HPT） of aero-engine in this paper. This investigation focuses on the effects of contoured axisymmetric-casing on the blade tipleakage flow. While the size of tip clearance remains the same as the original design, the rotor casing and the blade tip are obtained with the same contoured arc shape. Numerical calculation results show that a promotion of 0.14% to the overall efficiency is achieved. Detailed analysis indicates that it reduces the entropy generation rate caused by the complex vortex structure in the rotor tip region, especially in the tip-leakage vortex. The low velocity region in the leading edge（LE） part of the tip gap is enlarged and the pressure side/tip junction separation bubble extends much further away from the leading edge in the clearance. So the blocking effect of pressure side/tip junction separation bubble on clearance flow prevents more flow on the tip pressure side from leaking to the suction side, which results in weaker leakage vortex and less associated losses.     

高空通风活门内流场特性数值模拟和试验验证

为准确掌握大通风量条件下高空通风活门工作特性,以高空通风活门为研究对象开展流场特性数值仿真分析技术研 究,对不同膜盒间隙的高空通风活门内部流场进行对比分析,获得了不同入口质量流量条件下高空通风活门的压降特性曲线。结 合滑油系统附件试验器改造,利用小量程与大量程体积流量计组合形式实现纯空气体积流量的测量,开展了高空通风活门压降试 验,并将试验结果与数值仿真分析结果进行对比验证。结果表明：仿真分析结果与试验结果吻合较好,流场特性仿真分析方法可 用于高空通风活门压降特性预测,现有高空通风活门在不同膜盒间隙下内流场特性相似,其压降主要集中于膜盒间隙处,改善膜 盒间隙处结构,可有效降低压降。     

Bolt insertion damage and mechanical behaviors investigation of CFRP/CFRP interference fit bolted joints

Interference fit has advantages in improving fatigue behaviors of composite bolted joints; however, interference fit bolt insertion tends to cause damages in laminates weakening joint mechanical properties. Therefore, an experimental study was conducted to investigate bolt insertion damages of Carbon Fiber Reinforced Polymer (CFRP)/CFRP interference fit bolted joints. Mechanical behaviors of joints were also evaluated experimentally under both quasi-static loads and cyclic loads. Scanning Electron Microscope (SEM) and high-resolution X-ray micro-CT scan were used to examine micro damages in laminates. Damage and failure behaviors of joints were characterized. The results demonstrated that the hole entrance in upper laminate and the laminate boundary near the hole wall were the most critical regions for damages during bolt insertions. However, the influence of those damages on quasi-static failure loads and fatigue failure modes of joints was minimal. Delamination and matrix cracking occurred first in laminates following fiber and matrix fracture in quasi-static tensile tests. Interference fit could improve the fatigue resistance of the laminate hole; however, the bolt seemed to suffer a more critical local fatigue loading condition. This paper can contribute to composite structure designs, especially in understanding damage and failure behaviors of composite bolted joints.     

基于空基平台的激光通信技术研究和展望

深低温阀门多为常温设计，低温服役。宽温域引起的结构变形将诱发阀门导向卡滞、密封泄漏等安全问题。采用有限元分析方法获取阀门导向副配合部位变形量，提出迭代镜像补偿方法解决深低温服役的阀门导向副变形超差问题。经分析，在深低温工况下阀门配合间隙均超出设计允许值，导向行程最大时配合间隙减小17.95%至16.41 μm；补偿后导向副配合间隙变形量控制在1 μm内，满足深低温工况下阀门形状设计要求，验证了迭代镜像补偿方法的有效性。     

高温环境下角接触球轴承磨损寿命分析

针对高温环境下轴承材料性质和润滑状态变化，造成轴承磨损加剧，过早丧失精度的问题。首先开展高温环境下轴承用材料的摩擦磨损试验，获取材料的磨损系数。在此基础上，考虑温度、润滑、轴承材料属性等对轴承磨损性能的影响，建立高温角接触球轴承磨损模型，通过数值求解探讨工况参数和结构参数等对轴承磨损性能的影响，并评估轴承的磨损寿命。结果表明：对于高温轴承材料无磁合金GH05，在高温300 ℃摩擦状态下平均磨损系数为2.5×10^-7 mm²/N；随着载荷、转速、温度的增加，轴承内、外滚道的磨损率均不断增大，其中内圈磨损率大于外圈，内圈磨损特性决定着轴承的磨损寿命；载荷和转速是决定轴承磨损寿命的主要因素，轴承主结构参数对磨损寿命具有重要影响，通过结构优化可提高轴承磨损寿命。     

PBT固体推进剂低温力学性能研究

为考察PBT固体推进剂低温力学性能，采用单轴拉伸实验方法研究了固化参数、交联参数、固化时间三种因素对PBT固体推进剂-40℃下力学性能的影响。玻璃化温度测试结果表明，全部样品玻璃化温度处于-51.3～-53.6℃，推进剂在-40℃下处于高弹态；单轴拉伸测试结果表明：PBT固体推进剂在低温状态下硬度、抗拉强度与固化参数、交联参数、固化时间呈正相关，伸长率与固化参数、交联参数、固化时间呈负相关。低温力学性能受固化参数、交联参数影响显著性低于常温力学性能；低温下固化参数在1.00～1.05内与伸长率呈现一定线性关系。     

叶顶间隙偏差对叶片气动性能影响的不确定性研究

在压气机叶片加工过程中，实际加工得到的叶片外形与设计叶型不可避免会存在一些偏差。为研究叶片叶顶间隙尺寸波动对性能的影响，以Rotor37为研究对象，采用三维定常数值模拟方法，基于非嵌入式混沌多项式中二维正态分布变量产生方法，分别对叶片前缘叶顶间隙和尾缘叶顶间隙进行尺寸波动干扰，研究了叶顶间隙不确定性对气动性能和流场的不确定性影响，评估了公差带内叶顶间隙偏差与气动性能变化的相关性，并探究了叶顶间隙变化对叶片稳定裕度的影响机理。研究发现，叶顶间隙偏差对等背压条件下叶片质量流量、等熵效率和总压比的平均水平几乎不会造成影响；叶顶间隙偏差所造成的气动性能分布标准差随工况点向不稳定边界的逼近而逐渐增大。同时，叶顶间隙不确定性会导致样本稳定裕度均值有所降低，不确定性分析中稳定裕度均值相对原型叶片下降了2.42%。流场结构方面，叶顶间隙偏差主要影响80%叶高以上部分流场；叶顶间隙偏差对叶顶区域泄漏流产生的影响，导致了叶片稳定裕度的变化。