钢焊丝脉冲GMA焊最佳熔滴过渡形式的参数模型

基于磁流体微扰动“失稳”的原理,建立了钢焊丝脉冲GMA焊最佳熔滴过渡形式的参数模型。通过试验对比,验证了该模型的工程实用性。     

重力扰动对SINS水平姿态的影响

为研究动基座下捷联惯导系统(Strapdown Inertial Navigation System, SINS)水平姿态误差角与水平重力扰动间的关系,推导了南北方向、东西方向匀速直线运动时,SINS纯惯性解算的水平姿态误差与水平重力扰动间的传递函数,并分析了传递函数的零极点分布;推导了组合导航模式下,水平姿态误差角与水平重力扰动间的传递函数;通过仿真分析了纯惯性解算和组合导航模式下传递函数的幅频特性。组合导航相对于纯惯性解算模式,截止频率更大,SINS姿态误差角受更多高频重力扰动信号的影响,因此,组合导航模式需要更高分辨率的重力扰动数据来进行重力扰动补偿。此外,在对高精度SINS进行重力扰动补偿时,对于重力扰动分辨率的需求是有限度的,过于精细的重力扰动数据只会带来测量和存储压力,不能提高SINS的姿态精度。     

Effect of friction stir processing on mechanical properties and heat transfer of TIG welded joint of AA6061 and AA7075

Tungsten inert gas (TIG) welding is the most commonly used joining process for aluminum alloy for AA6061 and AA7075 which are highly demanded in the aerospace engineering and the automobile sector, but there are some defects occur during TIG welding like micro-crack, coarse grain structure, and porosity. To improve these defects, the TIG welded joint is processed using friction stir processing (FSP). This paper presents the effect of friction stir processing on TIG welding with filler ER4043 and ER 5356 for dissimilar aluminum alloy AA6061 and AA7075. The mechanical characterization, finite element formulation and mathematical equations of heat transfer of TIG + FSP welded joints are investigated using ANSYS Fluent software by adjusting process parameters of FSP. The results show that the maximum compressive residual stress 73 MPa was obtained at the fusion zone (FZ) of the TIG weldment with filler ER4043, whereas minimum compressive residual stress 37 MPa was obtained at stir zone (SZ) of the TIG+FSP with filler 5356. The maximum heat flux 5.33 × 106 W/m2 and temperature 515 ℃ have observed at tool rotation 1600 rpm with a feed rate of 63 mm/min. These results give a satisfactory measure of confidence in the fidelity of the simulation     

Hazard evaluation of ignition sensitivity and explosion severity for three typical MH2 (M＝Mg,Ti, Zr) of energetic materials

MgH2, TiH2, and ZrH2 are three typical metal hydrides that have been gradually applied to composite explosives and propellants as additives in recent years. To evaluate ignition sensitivity and explosion severity, the Hartmann device and spherical pressure vessel were used to test ignition energy and ex-plosion pressure, respectively. The results showed that the ignition sensitivity of ZrH2, TiH2 and MgH2 gradually increased. When the concentration of MgH2 is 83.0 g/m3 in Hartmann device, the ignition energy attained a minimum of 10.0 mJ. The explosion pressure of MgH2 were 1.44 times and 1.76 times that of TiH2 and ZrH2, respectively, and the explosion pressure rising rate were 3.97 times and 9.96 times that of TiH2 and ZrH2, respectively, through the spherical pressure vessel. It indicated that the reaction reactivity and reaction rate of MgH2 were higher than that of TiH2 and ZrH2. In addition, to conduct in-depth theoretical analysis of ignition sensitivity and explosion severity, gas production and combus-tion heat per unit mass of ZrH2, TiH2 and MgH2 were tested by mercury manometer and oxygen bomb calorimetry. The experimental results revealed that MgH2 had a relatively high gas production per unit mass (5.15 mL/g), while TiH2 and ZrH2 both had a gas production of less than 2.0 mL/g. Their thermal stability gradually increased, leading to a gradual increase in ignition energy. Furthermore, compared with theoretical combustion heat, the combustion ratio of MgH2, TiH2 and ZrH2 was more than 96.0%, with combustion heat value of 29.96, 20.94 and 12.22 MJ/kg, respectively, which was consistent with the explosion pressure and explosion severity test results.     

基于"姿态矩阵"量测的机载导弹传递对准技术

"速度+姿态"量测匹配方案是目前比较理想的机载导弹传递对准技术.采用"姿态"量测时存在矩阵计算量大等缺点,在具体工程应用时更会受到计算机速度的限制,尤其是需要快速进行卡尔曼滤波计算时.引入了一种与"姿态"量测具有相同特点的"姿态矩阵"量测方案,设计了快速对准卡尔曼滤波器,并进行了仿真分析.结果表明是一种具有工程意义的实用快速传递对准技术.     

某高炮火控系统滤波器设计

对目前高炮火力控制系统目标滤波与预测进行了分析与研究。在此基础上结合工程实际设计了一种α-β滤波器,该滤波器的原理是把在连续系统中频率域的要求和在离散系统中Z域的要求转换成时域中在典型信号激励下的时间响应的特征值的要求,从而在时间域中以特征值的要求进行综合,再把综合的结果转换回Z域中,最终得到所确定的α-β滤波器,给出了α-β滤波器的Z传递函数、分析了α-β滤波器参数的确定,对α-β滤波器的静态误差进行了研究,对设计方案进行了计算机仿真和实际应用。     

基于马尔可夫分析的人才拥有量研究

基于马尔可夫分析理论,给出了人才拥有量预测的马尔可夫模型,并且讨论了模型中转移概率的确定及模型的预测质量等问题.     

捷联惯导大失准角误差模型在快速传递对准中的应用

针对快速传递对准中主子惯导相对姿态存在大角度的情况,推导了捷联惯导大失准角误差模型.该模型采用欧拉角表示姿态误差,并用欧拉运动方程准确描述其传播规律.鉴于该模型中的姿态观测方程是复杂的非线性函数,采用无需求导的UKF算法,并采用奇异值分解(SVD)解决方差阵的病态问题.仿真结果表明,该算法在小角度误差条件下滤波精度优于线性模型,并且适用于大角度误差条件.     

HALLO进气系统对柴油机燃烧的影响分析

利用燃烧分析方法,对TBD620V12柴油机的缸内压力曲线进行了放热规律分析.根据分析结果,研究了HALLO进气系统对燃烧过程的影响,确定了TBD620V12柴油机燃烧过程的特征参数.结果表明,采用HALLO进气系统,既保证了低负荷下形成良好的可燃混合气,使柴油机可在低负荷下良好地工作,又保证了高负荷下进气量,使高负荷下燃油充分燃烧.     

基于ISM的油库安全事故成因分析

分析油库安全事故成因，划分事故成因类型，对于有效控制事故发生、保障油库运行安全是极其重要的。运用系统工程思想，对油库安全事故成因要素的相互关系进行分析，建立了油库安全事故成因多层递阶解释结构模型（ISM）。分析和计算结果表明：油库安全事故成因大致可分为根本原因、直接原因和间接原因三个类型（层次）。针对不同层次结构的事故成因，可以制定相应的预防和控制措施，为军用油库抓住安全管理重点、有效防止事故发生提供理论依据。