数字全息测量超高速撞击碎片云实验研究

在中国空气动力研究与发展中心(CARDC)超高速碰撞中心(HIRC)7.6 mm超高速碰撞设备的基础上，搭建纳秒级脉冲激光数字全息系统。提出滤波片和衰减片组合布置，减弱超高速碰撞等离子体自发光、提高信噪比的方法。实验获得了2.25 mm铝球弹丸以4.0 km/s的速度撞击0.5 mm厚铝板形成碎片云的全息图。采用小波变换算法对碎片云全息图进行重建，得到超高速撞击碎片云的三维结构和碎片大小。碎片云的轮廓呈椭球型，分为碎片云的前端、核心和外壳，碎片主要分布在弹丸破碎形成的碎片云核心，存在大碎片，且分布较集中，对后板的损伤也严重     

浅谈水洗发动机对大修成本的影响

通过对深圳航空公司CFM56-7B发动机水洗方法改进前后的发动机进厂大修数据进行比较,主要分析HPT导向器报废率的变化,说明改进的发动机水洗方式对于延长发动机在翼时间、降低HPT导向器报废率、节约大修成本起到良好促进作用。     

直流发电机并联供电平衡性探讨

主要介绍了某型飞机直流发电机并联供电的原理、供电时负载变化对平衡性的影响以及不平衡产生的原因,分析了影响并联供电的一般规律,并结合实际提出了预防不平衡供电的具体措施和建议。。     

数理统计方法在部件故障控制中的应用研究

机载部件的可靠性直接影响航空器的安全运行。本文通过对机载部件使用寿命的统计和失效分析,对部件的故障提出了有效的控制方法,并举例说明了此方法在维护中的使用。     

Availability modeling for periodically inspection system with different lifetime and repair-time distribution

Availability is a main feature of design and operation of all engineering system. Recently,availability evaluation of periodical inspection systems with different structures is at the center of attention due to the wide application in engineering. In this paper, an analytical and probabilistic availability model for periodical inspection system is proposed by a new recursively algorithm,which can achieve limiting average availability and instantaneous availability of periodical inspection system under arbitrary lifetime and repair-time distributions. Then three application examples are presented, the systems lifetime and repair-time are respectively fellow exponential/exponential,Weibull/normal and Weibull/lognormal distribution. Finally, a Weibull/lognormal system is studied to analyze the dynamic relationship between inspection period and availability. The results indicate that the proposed approach can provide the technology support for improving system availability and determining reasonable inspection period.     

Aircraft nonlinear stability analysis and multidimensional stability region estimation under icing conditions

Icing is one of the crucial factors that could pose great threat to flight safety,and thus research on stability and stability region of aircraft safety under icing conditions is significant for control and flight.Nonlinear dynamical equations and models of aerodynamic coefficients of an air craft are set up in this paper to study the stability and stability region of the aircraft under an icing condition.Firstly,the equilibrium points of the iced aircraft system are calculated and analyzed based on the theory of differential equation stability.Secondly,according to the correlation theory about equilibrium points and the stability region,this paper estimates the multidimensional stability region of the aircraft,based on which the stability regions before and after icing are compared.Finally,the results are confirmed by the time history analysis.The results can give a reference for stability analysis and envelope protection of the nonlinear system of an iced aircraft.     

A new structural reliability index based on uncertainty theory

The classical probabilistic reliability theory and fuzzy reliability theory cannot directly measure the uncertainty of structural reliability with uncertain variables,i.e.,subjective random and fuzzy variables.In order to simultaneously satisfy the duality of randomness and subadditivity of fuzziness in the reliability problem,a new quantification method for the reliability of structures is presented based on uncertainty theory,and an uncertainty-theory-based perspective of classical Cornell reliability index is explored.In this paper,by introducing the uncertainty theory,we adopt the uncertain measure to quantify the reliability of structures for the subjective probability or fuzzy variables,instead of probabilistic and possibilistic measures.We utilize uncertain variables to uniformly represent the subjective random and fuzzy parameters,based on which we derive solutions to analyze the uncertainty reliability of structures with uncertainty distributions.Moreover,we propose the Cornell uncertainty reliability index based on the uncertain expected value and variance.Experimental results on three numerical applications demonstrate the validity of the proposed method.     

基于ALE法的水陆两栖飞机船体着水性能分析

水陆两栖飞机的着水性能是体现其综合性能的重要因素之一.应用ALE法对三种水陆两栖飞机船体截面进行入水仿真计算,从着水载荷、喷溅性能及运动响应三个方面对着水性能进行综合评估.对比分析了直线型、带舭弯弧形、复合型三种构型截面在不同速度、不同重量下的压力分布、喷溅性能以及运动响应,得到了三种截面横向压力分布规律.计算结果显示相同状态下,喷溅性能复合型优于带舭弯弧形、带舭弯弧形优于直线型;过载复合型远大于带舭弯弧形,带舭弯弧形稍大于直线型,综合看来带舭弯弧形截面着水性能最佳.     

Theoretical aspects of selecting repeated unit cell model in micromechanical analysis using displacement-based finite element method

Repeated Unit Cell(RUC)is a useful tool in micromechanical analysis of composites using Displacement-based Finite Element(DFE)method,and merely applying Periodic Displacement Boundary Conditions(PDBCs)to RUC is almost a standard practice to conduct such analysis.Two basic questions arising from this practice are whether Periodic Traction Boundary Conditions(PTBCs,also known as traction continuity conditions)are guaranteed and whether the solution is independent of selection of RUCs.This paper presents the theoretical aspects to tackle these questions,which unify the strong form,weak form and DFE method of the micromechanical problem together.Specifically,the solution’s independence of selection of RUCs is dealt with on the strong form side,PTBCs are derived from the weak form as natural boundary conditions,and the validity of merely applying PDBCs in micromechanical Finite Element(FE)analysis is proved by referring to its intrinsic connection to the strong form and weak form.Key points in the theoretical aspects are demonstrated by illustrative examples,and the merits of setting micromechanical FE analysis under the background of a clear theoretical framework are highlighted in the efficient selection of RUCs for Uni Directional(UD)fiber-reinforced composites.     

维修方案项目优化的可靠性分析方法

通过可靠性管理对民用航空器维修方案的动态监控,实施对维修方案项目执行情况的跟踪和可靠性分析,以机队实际运行数据为背景,提出对维修方案项目管理系统性的优化和管理方法,以使航空公司的维修方案更加符合机队的实际使用和维护特点,进一步提高机队的运行效率、降低维修成本和提高航班准点率。