【作者】 张冬梅；

【导师】 高世桥；

【作者基本信息】 北京理工大学 ， 机械工程， 2016， 博士

【摘要】 随着侵彻弹药的发展,弹引系统结构的设计面临严峻的极端冲击过载环境的挑战。通常认为弹体受到的冲击环境就是引信体的冲击环境,但实际上,由于弹引连接处的冲击传递以及引信体复杂的结构,导致引信体受到的过载环境要比弹体的过载环境复杂得多。正是这个原因,侵彻过程中过载测试信号的成分极其复杂,其中既包含了目标作用在弹体上的刚体过载(由牛顿定律确定与系统结构无关的过载)也包含了弹引系统各结构的振动及各部件间的碰撞响应。基于以上背景,本文以弹引系统侵彻混凝土目标为研究对象,通过理论建模、试验测试、数值仿真计算以及信号时频分析等手段,对高速侵彻过程中弹引结构受到的极端过载及引信体与弹体间典型螺纹连接结构冲击传递的弹性和碰撞特性进行了研究。本文的主要研究内容及创新性研究成果如下:(1)提出了基于改进模糊模型的侵彻过载在线实时识别方法。为了获得高速侵彻混凝土目标过程中弹体受到的极端过载,建立了改进模糊模型,并基于该模型提出了一种能够描述整个侵彻过程并可以实时识别侵彻过载的理论计算方法;另外,为了实现在线计算,提出了着靶速度在线计算方法,给出了模型参数在线识别和修正方法,并通过已有的试验数据对提出的计算模型和方法进行了验证。同时,对弹体侵彻混凝土目标的过程进行了试验研究和有限元仿真分析,将理论计算与试验测试及仿真分析进行比较,结果的一致性验证了基于改进模糊模型的侵彻过载在线识别方法的可靠性。(2)为了实现极端过载测试信号的快速实时处理,提出了一种实时分段小波滤波方法。针对该方法中的小波分解层数和分段长度的选择,首先确定了滤波截止频率,并根据该频率给出了小波分解层数的选取方法;然后,通过对比不同段长的分段小波滤波结果,给出了分段长度的选择方法,并通过过载测试数据对这些方法进行了验证。(3)考虑到螺纹轴向载荷分布的不均匀性,首次提出了弹引螺纹连接结构间冲击传递的弹性模型。为了分析弹引连接结构的冲击传递过程,针对弹体与引信体典型的螺纹连接结构,在充分考虑了螺纹轴向载荷分布不均匀特性的条件下,提出了螺纹连接结构的弹性模型,并给出了一种计算螺纹轴向载荷分布、螺纹连接结构刚度以及螺纹连接结构固有频率的新方法。同时,进行了螺纹连接结构拉伸过程的有限元仿真分析和试验研究。通过结果的对比和分析发现螺纹连接结构的刚度明显低于材料本身的刚度,这说明通常分析中将螺纹连接结构视为固连结构是不合理的。另外,通过对不同材料和尺寸的螺纹连接结构进行分析,得出了杨氏模量、螺距、螺纹旋合长度等对螺纹上的载荷分布和螺纹连接结构刚度影响的规律。在侵彻过载测试信号的时频分析结果中明显地存在与螺纹连接结构的固有频率一致的振动信号,并且该频率成分的信号幅值很高,对过载信号具有很大的影响,这也验证了弹性模型的正确性。(4)在螺纹连接结构间冲击传递的弹性模型基础上,率先提出了弹引螺纹连接结构间冲击传递的碰撞模型。针对侵彻过程中的弹引连接结构,提出了弹引螺纹连接结构间冲击传递的碰撞模型,并推导出了螺纹碰撞力和碰撞时间表达式。通过对由螺纹连接的弹引系统侵彻混凝土目标过程的有限元仿真,得到了冲击载荷作用下螺纹上的应力传递规律以及与静载荷作用下螺纹轴向载荷分布的区别。同时通过对比不同碰撞速度、螺距和长径比情况下螺纹碰撞力,给出了弹体与引信体连接螺纹尺寸的选择方法。最后通过侵彻过载测试数据对碰撞模型进行了验证,结果发现螺纹碰撞产生的碰撞信号频率明显高于螺纹弹性产生的振动信号的频率,并且振动信号和碰撞信号的幅值都很大。这些结果证实了由于弹引连接处的冲击传递,通过螺纹连接在弹体上的引信体的冲击环境要比弹体本身的冲击环境复杂得多。本文获得的研究成果不但可以为深入认识高速硬目标侵彻过程中弹引结构的极端过载环境以及弹引结构间的冲击传递特性提供数据和方法参考,同时也可以为硬目标侵彻弹引结构的可靠性设计提供技术信息。更多还原

【Abstract】 With the development of penetrator,the design of projectile-fuse system is facing severe challenge of extreme impacting overload.It is generally accepted that the impact environment of projectle is the impact environment of fuze.In fact,the impact environment under the fuze is more complicated than projectile due to the impact transmission on projectile-fuze connections and the complex structure of fuze.It’s just because of this reason that the components of measured overload are very complex.The measured overload at any location on projectile is consisted of rigid-body overload of projectile,vibration response of structure and collision of between parts.According to the background discussed above,the extreme overload and impact transmission on projectile-fuze system during high-speed penetration were studied by using theoretical modeling,experimental research,numerical simulation and signals time-frequency analysis.(1)In order to obtain the extreme overload of projectile into concrete target,the improved fuzzy model was builded.Based on this model,a calculation method which can well describe the entire penetration process and identify the real-time penetration overload was developed.In addition,we proposed methods calculating the striking velocity and gave the method about the on-line identification and correction for parameters in model.All of the model and methods were verified by measured overload.At the same time,the experiments and finite element analysis for the projectiles penetrating into concrete targets were conducted.The calculated results by model are in reasonably good agreement with the measured data from experiments and finite element analysis.(2)In order to realize the fast and real-time processing for the measured extreme overload,we presented real-time segment wavelet filtering.For the decomposition level and segment length in this method,firstly,the threshold frequency for filtering was determined and the level of wavelet decomposition was determined based on the frequency.Then,by comparing the filering results with different segment length,the choosing method for segement length of segment wavelet filtering was determined.Finally,these methods were verified by measured overload.(3)Considering the ununiformity of load distribution on screw,the elastic model for threaded connection was established.According to elstic deflection of the thread,the axial load distribution of engaged threads was determined,the thread stiffness and natural frequency of threaded connection were calculated.Finite element analysis for thread connection stiffness was performed by building the 3-D model.A set of tensile tests were exerted to validate the accuracy of the suggested model.A good agreement was obtained when the analytical results were compared with FEA results and experimental data.Results reveal that the stiffness of thread connections is obviously lower than that of thread body.In addition,the influence law about Young’s modulus of material,the engaged length and thread pitch for the thread stiffness was obtained.There are the vibration signal caused by the elastic of thread in the frequency components of measured overload and the amplitude of the signal is very high,which verified the correctness of elastic model for threaded connection.(4)Based on the elastic model for threaded connection,the collision model for the threaded connection between projectile and fuze under impact load was proposted,and the calculational method of collision time and collision force were given.Through the finite element analysis for the process of projectile-fuze system penetrating into concrete target,we obtained the law of load distribution on screw and the difference with static load.Meanwhile,by comparing the collision force with different collision velocity,pich and length to diameter ratio(The ratio of the length of the thread and the nominal diameter,L/D),the choice method for screw size was given.Finally,the collision model was verified by measured overload.It is seen that the frequency of collision signal is obviously higher than vibration signal caused by elasticity of threaded connection.The amplitude of the vibration signal caused by elasticity and collision of threaded connection is very high and has great influence on the measured overload.The results well illustrated that the impact environment under fuze is more complex than projectile.The findings of the research in this paper not only can provide significant data and reference for the further knowledge of extreme overload and impact transmission of projectile-fuze system during high speed penetration,but also can provide technical information for the design of projectile-fuze system structures.更多还原