EFFECT OF HEAT TREATMENT ON INTERMEDIATE TEMPERATURE STRESS RUPTURE PROPERTIES OF ALLOY K403

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SYNTHETIC STRESS LIFE TESTING OF MECHATRONIC PRODUCTS UNDER VARIABLE STRESS SPECTRUM

Mechatronic products usually endure the variable stress spectrum when they operate in certain operational condition and environmental condition, which obey the Weibull distribution. In accordance with the features of mechatronic product, this paper analyzes the failure mode, its corresponding sensitive stress and the design principles of life testing profiles. Based on the above analyses, this paper presents a synthetic stress life testing method based on the hybrid Weibull distribution and its statistical method under variable stress spectrum to evaluate the reliability and life indices of mechatronic products. Because the mechatronic products have many characteristics such as high price, long life and small testing samples, the synthetic stress life testing method under variable load spectrum can simulate the real various spectra, decrease the life testing time and reduce the testing samples. So it is effective to carry out the life testing to mechatronic products. The application results of hydraulic pumps indicate that this method can easily handle the experimental data under variable amplitude spectrum, obtain the high precision parameters point estimation and confidence interval estimation and reduce the testing cost greatly.     

基于某型振动式干燥机应力集中问题的强度分析

针对某型振动式干燥机模梁的应力集中问题,运用有限元理论和电测法对横梁进行了强度分析,找出了其产生破坏的原因。     

胶接连接件应力分析新模型与新方法

在工程梁理论基础上根据力法变分原理得到薄壁结构胶接接头应力分布的解析闭合解,克服依照传统剪滞理论所得之结果不能满足边界条件的缺点,指出使胶接接头失效的真正原因是接头端部的剥离正应力,从而为胶接接头设计提供正确依据。     

一种面向星载计算机的功能级功耗估计方法

在星载计算机的软硬件协同设计过程中需要解决处理器功耗估计问题.现有的工具和方法主要面向ARM或DSP处理器,缺乏可用于LEON3处理器的软件功耗估计方法.针对这一不足,基于功能级功耗分析方法进行功耗估计,重点解决LEON3处理器的功耗建模问题.提出了从C代码中提取模型参数的方法,并且对序贯最小优化支持向量回归算法进行了改进,提高模型的精度.在数值试验部分,通过常用的C语言算法试验对估计方法进行了验证.结果表明功耗估计误差小于3%,能够满足星载计算机软硬件协同设计的需要.     

Direct Numerical Simulation of Secondary Breakup of Liquid Drops

This article studies numerically a familiar important phenomenon in spray combustion which is deformation and breakup of liquid drops in gas flow. The SIMPLER method is used to solve the two-dimensional (2D) unsteady axisymmetric Navier-Stokes equations for both the drop and the ambient gas flow. The level set method is applied to capturing the liquid/gas interface. Through calculation are obtained four typical breakup modes-oscillation, bag breakup, sheet stripping breakup and shear breakup governed by four non-dimensional numbers which are gas Weber number (Weg), liquid Reynolds number (Rel), gas Reynolds number (Reg) and density ratio (γ) . Their effects upon each mode are analyzed. The results indicate that among the four numbers, Weg is of the highest importance with Rel, Reg and γfollowing up. By widening the range of the density ratio up to 1 000, the breakup mode is discovered to be so complicated that a new one called multimode breakup mode turns up. This mode contains the shearing breakup and piercing breakup, which successively happen. The calculation results agree well with what is observed from the experiments.     

基于层次分析法的直扩信号安全性能评估模型

在综合直扩信号风险分析、截获方法的基础上，率先对直扩信号安全性能评估模型进行了研究，建立了基于AHP（AnalyticHierarchyProcess，层次分析法）的直扩信号安全性能评估模型，详细给出了直扩信号安全指数的计算过程，并对多种直扩信号的安全指数进行了仿真。仿真结果袁明：评估方法有效；提出的模型可以定量评价不同直扩信号的安全性能，为直扩信号的安全性设计提供定量的依据。此外，还提出了卫星测控直扩信号的安全等级分类原则和卫星安全等级要求。     

芯子宽厚比对铝蜂窝夹层结构平压强度的影响

用正六边形代替实际蜂芯,推导了夹层结构的平压强度与芯子宽厚比的关系,并对八种规格的芯子平压强度进行统计,统计结果虽然与推导的结果有偏差,但规律却是一致的,即蜂窝夹层结构的平压强度随着芯子宽厚比d/t_s增大呈负指数减小。     

北斗D2导航电文解析和完好性性能分析

为评估北斗D2导航电文对系统空间信号完好性影响，对D2导航电文结构和内容进行研究。首先，通过基本导航信息的解析，给出了确定卫星位置和用户位置过程所需的信息和时间，并对受卫星星历和时钟影响的用户测距误差做了说明，介绍了电离层误差、对流层误差改正模型。然后，通过增强服务信息的解析，论述了完好性信息（RURA、UDRE）及格网电离层延迟的计算方法。最后给出了使用完好性信息、用户局部误差获取用户定位误差保护级的算法。     

Aeroacoustic and aerodynamic optimization of propeller blades

It is of great significance to develop a high-efficiency and low-noise propeller optimization method for new-generation propeller aircraft design. Coupled with free form deformation method, dynamic mesh interpolation technology, optimization algorithm, surrogate model, aerodynamic calculation and aeroacoustic prediction model module, the integrated aerodynamic and aeroacoustic design method of propeller is built. The optimization design for the six-blade propeller is carried out. The non-reduction in efficiency, thrust coefficient and the minimum of aerodynamic noise is treated as the optimization design objective. The spatial vorticity distribution of the propeller before and after the design is also analyzed by using unsteady computational fluid dynamics method. The results show that the optimized propeller can effectively reduce the aerodynamic noise level. The maximum total sound pressure level can be reduced by 5 dB without reducing its aerodynamic performance. The developed method has good application potential in low-noise optimization design of propeller and other rotating machinery.