Generation of Accelerated Stability Experiment Profile of Inertial Platform Based on Finite Element

The residual stress generated in the manufacturing process of inertial platform causes the drift of inertial platform parameters in long-term storage condition.However,the existing temperature cycling experiment could not meet the increased repeatability technical requirements of inertial platform parameters.In order to solve this problem,in this paper,firstly the Unigraphics(UG) software and the interface compatibility of ANSYS software are used to establish the inertial platform finite element model.Secondly,the residual stress is loaded into finite element model by ANSYS function editor in the form of surface loads to analyze the efficiency.And then,the generation based on ANSYS simulation inertial platform to accelerate the stability of experiment profile is achieved by the application of the analysis method of orthogonal experimental design and ANSYS thermal-structural coupling.The optimum accelerated stability experiment profile is determined finally,which realizes the rapid,effective release of inertial platform residual stress.The research methodology and conclusion of this paper have great theoretical and practical significance to the production technology of inertial platform.     

Investigation of Surface Integrity on TC17 Titanium Alloy Treated by Square-spot Laser Shock Peening

Laser shock peening(LSP) is an innovative surface treatment method,which has been shown to greatly improve the fatigue life of many metallic components.This work investigates surface integrity of TC17 titanium alloy treated by LSP with innovative square laser spot.Nd:glass laser with duration of 30 ns and spot size of 4 mm×4 mm is applied.The surface morphology and surface residual stress of the TC17 titanium alloy,treated with varying peening parameters such as laser power density and overlapping ratio,have been studied in detail.The results show that laser pulse energy greatly influences surface morphology and surface residual stress around single-spot treated areas,and compressive residual stresses are saturated as laser pulse energy is over 55 J.There are significantly different surface morphologies and residual stress distributions at the overlapped areas with different overlapping ratios.A relative smooth surface is produced with uniform compressive residual stress distribution at an overlapping ratio of 8 %.The experiment of residual stress relaxation is implemented by measuring residual stress at the center of four overlapped spots and by four point bending fatigue test at the frequency of 105 Hz.The compressive residual stresses induced by LSP are found to relax quite slowly under cyclic fatigue loading.     

镍基高温合金GH4169磨削参数对表面完整性影响

研究了用单晶刚玉砂轮磨削镍基高温合金GH4169时,磨削参数对表面完整性中的表面特征(表面粗糙度、表面形貌、表面显微硬度和表面残余应力)的影响,以期优化磨削参数.砂轮速度依次选择15,20,25m/s,磨削深度分别选择50,100,150μm,工件速度分别选择5,10,15m/min.研究结果表明:表面粗糙度对工件速度的变化最敏感,表面显微硬度对砂轮速度变化最敏感,表面残余应力对砂轮速度变化最敏感;同时表明了磨削参数对磨削表面形貌、显微硬度梯度、微观组织、残余应力梯度的影响,揭示了表面完整性中的变质层形成规律.其塑性变形层在5～10μm,显微硬度变化影响层为80～100μm,残余应力影响层厚度为80～200μm,其为磨削镍基高温合金表面完整性控制研究提供相关的实验数据基础.      

横流不稳定性转捩预测模型

由于Langtry和Menter提出的γ-Re_θt边界层转捩模型只能预测流向的边界层转捩现象,因此继续改进该转捩模型使其具有横流不稳定性转捩的预测能力显得非常必要。通过对经典Falkner-Skan-Cooke (FSC)三维边界层相似解的理论分析和数值求解,结合Thwaites压力梯度因子与当地后掠角构建的函数关系来求解复杂构型的当地Hartree压力梯度因子β_H以及形状因子H₁₂,采用由试验数据标定的C1准则关系式获得横流转捩位移厚度雷诺数,从而建立能够对复杂构型进行横流不稳定性转捩预测的转捩判据。应用所建模型对30°前缘后掠角的ONERA-M6机翼和变前缘后掠角的DLR-F5机翼以及标准6:1椭球标模进行了横流不稳定转捩数值模拟,计算结果显示转捩位置均与试验数据吻合较好,证明了该模型的合理性和实用性。     

小流量下转静系盘腔传热特性

采用热敏液晶(TLC)瞬态传热实验技术对小流量下的中心进气转静系盘腔传热特性进行研究,介绍了同步触发拍摄系统,考察了流量与转速变化对动盘面传热的影响.结果表明:在所研究工况范围内,流量变化对动盘面中低半径处传热影响较大,对高半径处影响较小;转速升高使动盘面传热效果整体增强;当湍流流动参数较小时,动盘面中高半径区域努塞尔数随半径增大而增大;采用湍流流动参数对动盘面平均努塞尔数进行归纳,实验结果与雷诺相似分析结果的偏差小于15%,一定程度上验证了雷诺相似对转静盘腔传热问题的适用性.      

柔片式密封数值计算及性能分析

针对高速转子柔片式密封系统,建立了密封区域流场的数学模型,采用一种修正的压力耦合方程组的半隐式方法(Semi-Implicit Method for Pressure-Linked Equations Revised, SIMPLER)算法和有限差分法对数学模型进行数值求解,构建了柔片式密封性能分析程序,得到密封系统的压力场分布、速度场分布及泄漏量等,研究了不同结构参数和工况参数对密封性能的影响.分析结果表明:泄漏量随密封压差的增大呈线性增长趋势,而随转子转速的增大略有减小;增加柔片宽度、减小柔片长度、减小前/背板-转子间距均对降低密封系统的泄漏量有益,而柔片安装角度的变化则对密封系统的泄漏量影响不明显.基于流场的结果,柔片和转子的动力学响应将被研究.      

基于ANSYS的齿根应力和齿面变形的合理分析

根据齿轮啮合原理,准确求出复杂的齿廓曲线;采用MATALB—APDL混合建模方法,创建精确的齿轮有限元模型。在不同网格密度等级下,分别对齿轮的齿面变形、齿根应力分布进行分析。对照经验公式的计算结果,得出如下结论：在齿轮数值模拟中,由于有限元软件计算中舍入误差的存在,网格划分合理与否将直接影响仿真程度的高低;网格密度等级对齿面最大变形的仿真结果有较大影响,而对齿根应力影响甚微。     

超临界压力下航空煤油RP-3在水平细圆管内对流换热特性实验研究

为探究超临界压力下碳氢燃料在水平管内的对流换热规律,文章针对超临界条件下航空煤油RP-3在水平细圆管内的对流换热,分析了热流密度、进口雷诺数及浮升力对对流换热的影响。研究表明:沿流动方向,管内表面传热系数随热流密度的增大先减小后增大;在低进口温度及低进口雷诺数情况下,管内换热均出现先恶化后强化的现象,而随着进口温度和雷诺数的增加,此现象消失;浮升力对换热的影响随热流密度的增加而增加;浮升力对下表面换热的加强使得入口效应的影响在下表面先于上表面结束;受浮升力影响,上下壁最大温差可达50 K;质量流速的增加会抑制浮升力对换热的影响;准则数Grq/Grth可以很好地反映浮升力的变化趋势。以上研究结果可为采用碳氢燃料作冷却介质的各类飞行器主动热防护技术方案提供技术支撑。     

战斗机模型大迎角风洞实验的雷诺数影响实验研究

介绍了两个战斗机模型大迎角风洞实验雷诺数对实验数据的影响,分析了造成这种影响的原因以及为获得能反映高雷诺数流动特点的稳定气动数据所采用的实验模拟技术,重点描述了雷诺数对大迎角俯仰力矩、零侧滑偏航力矩和滚转力矩的影响,探讨了零侧滑偏航力矩（Ｃｎ０）对不同的模型头部构型随侧滑角变化的迁移情况。对于大迎角飞行的歼击机,雷诺数的影响不只在风洞实验中存在,在飞机试飞过程中也存在,地面模拟设备应最大限度地提高模拟能力,准确预测雷诺数的影响,给出稳定可靠的实验数据。     

Estimation of sediment settling velocity in estuarine and coastal waters using optical remote sensing data

A robust method has been developed for estimating sediment settling velocity (w_s) from high resolution optical remote sensing data in estuarine, coastal and harbor waters. This method estimates settling velocity as a function of the drag coefficient (C_d), Reynolds number (Re), grain size (D₅₀), specific gravity (Δ_SG) and grain shape (in terms of the Corey Shape Factor – CSF). These parameters were derived from the particulate inherent optical properties such as backscattering (b_bp), beam attenuation (c_p), suspended sediment concentration and turbidity using Landsat 8 OLI and HICO data. Preliminary results for the Gulf of Cambay in the eastern Arabian Sea and Yangtze river estuary in the East China Sea, showed that satellite-retrieved settling velocities (m?s^?1) varied from very low values in clear oceanic waters, intermediate values in coastal waters, to very high values in river plumes and sediment-laden coastal waters. The remote sensing retrievals of sediment properties and their settling velocities were generally consistent with the field and laboratory results, which indicate that the proposed methodology will have important implications in various coastal engineering, environmental and management studies.