【作者】 何玲；

【导师】 徐诚；

【作者基本信息】 南京理工大学 ， 机械工程， 2011， 博士

【摘要】 自动机是枪械的关键部件,其寿命直接影响着枪械的整体寿命。对自动机部件失效原因的研究表明,冲击疲劳是影响其寿命的重要因素。目前,国内枪械设计的冲击疲劳理论尚未形成,实验数据也很少。而研究自动机冲击疲劳寿命的变化规律,必须建立专业的实验系统。现在市面没有适用于自动机关重件冲击疲劳的实验机,为满足自动机关重件冲击疲劳实验需求,本文设计开发了一种冲击疲劳实验系统,并进行了相关理论与实验研究。基于机构运动可靠性和低成本原则,本文提出了一种自动机关重件冲击疲劳实验机总体方案,主机采用机械式结构。由于自动机冲击疲劳实验对冲击脉冲幅值、幅宽和频率均有严格要求,作为实验机主机关键部件的加载机构是本文的难点之一。针对实验系统的加载要求,提出了含弹簧振子让位装置的曲柄滑块机构、含拨叉的曲柄连杆机构、直动滚子凸轮机构和双凸轮-滑块机构4种加载机构方案。运用数值仿真计算方法分析4种机构运行情况,分析4种机构的优缺点,最终确定加载机构方案为特殊的双凸轮-平底滑块机构。建立了双凸轮平底滑块加载机构数值仿真模型,得到机构在最高转速条件下的工作特性。建立了加载机构多目标优化模型,用基于Pareto最优理论的多种群遗传算法得到了加载机构优化方案。冲击疲劳实验中对试件的冲击加载由力脉冲发生器完成,力脉冲发生器中的冲头与试件直接接触,冲头的形状与材料特性对冲击接触过程有重要影响作用,从而影响着实验系统的运行情况。本文建立了冲头和试件两构件间的冲击接触仿真模型,计算2种形状、3种材料的冲头在2种冲击条件下冲击钢试件的过程,得到冲击力-时间、冲击力-变形、冲击冲量-变形和冲击冲量-时间的变化规律,分析并获得了超弹性体-弹性体、弹性体-弹性体和弹塑性体-弹性体间的冲击过程与冲头形状和材料的关系。本文建立了一种基于非线性弹簧阻尼理论的冲击接触力工程模型,用于求解在不同冲击质量和冲击速度条件下,特殊材料、特殊形状的冲头向试件提供的冲击接触力、冲击作用时间、变形量和冲击冲量。使用落锤式冲击实验机对3种材料、2种形状的冲头进行冲击实验。对冲击接触工程模型进行修正,得到超弹性体-弹性体、弹性体-弹性体和弹塑性体-弹性体间在2种冲头形状下的冲击接触力修正模型,修正模型结果与实验数据吻合较好。另外,本文为提高冲击接触有限元模型的计算精度,引入指数型接触约束条件,通过调整接触约束条件中的关键参数,使有限元计算结果与实验值吻合较好。建立了冲击疲劳实验机整机有限元仿真模型,利用仿真计算结果进行工作特性分析。为分析整机性能稳定性,建立了整机多体动力学虚拟样机仿真模型。以导轨工作面间隙、滑块体运动行程、冲击速度、冲头形状和冲头材料为变量,以保证滑块体运动和冲击脉冲的重复性为目标,分析4个变量对整机性能稳定性的影响。由数值计算结果可知,稳定性受导轨工作面间隙和滑块体运动行程影响,而冲击速度、冲头材料和形状仅对冲击脉冲产生影响。以冲击质量、冲击速度、冲头材料和冲头形状为变化因素,以4个因素对冲击脉冲的影响为目标,利用正交实验法进行正交敏感性分析,结果表明冲击速度对冲击脉冲影响最大,冲击质量对其影响最小,冲头材料和冲头形状的影响居中。本文建立了自动机典型关重件的冲击疲劳寿命仿真分析模型,采用局部应力应变法分析了12.7mm狙击步枪枪机、12.7mm狙击步枪节套、95式5.8mm步枪拉壳钩、95式5.8mm步枪击针和12.7mm航空机枪闭锁片的冲击疲劳寿命,所得寿命估算值略大于10000次,与实际工程实验结果基本一致。研制了国内首套大吨位高频枪械自动机关重件冲击疲劳实验样机,样机运行稳定可靠,能够模拟自动机关重件实际工况,为自动机关重件实验提供了有力的技术手段。更多还原

【Abstract】 The automatic mechanism is one of the most important components of firearms and its life affects the overall life of gun directly. The researches on failure results of automatic mechanism components indicate that impact fatigue is a critical factor. At present, the theory of firearms design in domestic field is undeveloped and the testing data of impact fatigue of the components is insufficient. It is essential to set up the impact fatigue testing system in order to study the viariation principle about impact fatigue life of the components. However, the impact fatigue testing machine specially designed for the components has not been manufactured on the current market. In this paper, a variety impact fatigue testing system is designed to satisfy the requirements of automatic mechanism components.The main machine of impact fatigue testing system is designed to be mechanical-structured in consideration of movement reliability of mechanism and cost. The most difficult part in this system is to design the loading mechanism of impact fatigue testing machine as the automatic mechanism impact testing has high requests for the amplitude, width and frequency of impact pulse. In this study, there are four mechanisms to be considered:crank-slipper mechanism making up of spring mass, crank connecting rod mechanism containing shifting fork, direct motion roller cam mechanism and double cams mechanism. The advantages and disadvantages of these mechanisms are compared and analied through simulating caculating. Finally, the special double cams flat slipper mechanism is adopted to be the loading mechanism. It is a modeled simulation model of the loading mechanism to analyse movement status of mechanism under the highest rotation velocity condition. A multi-objective optimization model is built, with the multi-population genetic algorithm based on the Pareto optimal theory, an optimization scheme is obtained.The force-pulse generator executes the impact loading on the sample in the impact fatigue testing through its punch. The contact between punch and sample influences the operation of system significantly. Modeling the two components both punch and sample finite element models and computing the impact process of punch with two shapes and three material, the variety principles of force-time, force-displacement, impulse-displacement and impulse-time about impact pulse are obtained, the relationships between the shape of punch and impact process of hyperelasto-elastic, elastic-elastic and elastic-plastic are analyzed.This paper sets up the engineering model of impact contact basing on nonline spring damping theory, and it is used to analyze the impact force, impact time and impulse of special material and shape under different impact mass and velocity. It is executed the impact testing on three materials of two shapes. The engineering model is modified according to the testing data and the results of correct model matches the testing data. The finite element model is built and introducted type of index numbers contact constraint conditions and the results of correct model match the testing data through adjusting the key parameters under constraint conditions.The testing machine finite element model is modeled. The simulation analysis results are used to operating characteristic analysis. The virtual engine model of the overall machine is built to analyses the stability of machine movement. Taking the clearance of guide rail working surfaces, the movement distance of slipper, impact velocity, punch shape and material as the analysis factors, taking the repetition of displacement of slipper and impact pulse as the analysis objects, the stability of impact fatigue testing machine is analized. The simulation numerical results indicate that the clearance of guide rail working surfaces and the movement distance of slipper affect the stability and others analysis factors only influence the impact pulse. The conclusion of orthotropic sensibility analysis which adopts the orthotropic experimentation is:the impact velocity has the most important influence and impact mass has the least influence on the impact pulse.The simulation model of impact fatigue life of automatic mechanism key components is built and local stress-strain method is adopted to estimate impact fatigue life of the bolt and barrel extension of 12.7mm sniping rifle, the extractor and firing pin of 95 type 5.8mm rifle and the locking plate of 12.7mm aerial machine gun. The life of components is estimated to about 10000 times and the results are consistent to the actual engineering experiment.The domestic first set of great tonnage and high frequence impact fatigue testing model machine of automatic mechanism components has developed. The mechanism movement is stable and reliable. The mechanism can simulate the actual working conditions of critical components of automatic mechanism of firearms, so it provides the powerful technological means for impact fatigue test of the critical components of automatic mechanism of firearms.更多还原