Structural optimization for multiple structure cases and multiple payload cases with a two-level multipoint approximation method

This paper is to address structural optimization problems where multiple structure cases or multiple payload cases can be considered simultaneously. Both types of optimization problems involve multiple finite element models at each iteration step, which draws high demands in opti-mization methods. Considering the common characteristic for these two types of problems, which is that the design domain keeps the same no matter what the structure cases or payload cases are, both problems can be formulated into the unified expressions. A two-level multipoint approxima-tion (TMA) method is firstly improved with the use of analytical sensitivity analysis for structural mass, and then this improved method is utilized to tackle these two types of problems. Based on the commercial finite element software MSC.Patran/Nastran, an optimization system for multiple structure cases and multiple payload cases is developed. Numerical examples are conducted to ver-ify its feasibility and efficiency, and the necessity for the simultaneous optimizations of multiple structure cases and multiple payload cases are illustrated as well.     

考虑结构完整性和装填分数的星形药柱形状优化

在固体火箭发动机药柱设计过程中,装填分数较大的药柱结构完整性很难满足要求。利用PCL对商用有限元软件MSC Patran/Marc进行二次开发,建立星形药柱发动机的二维参数化有限元模型。在此基础上,采用遗传算法对星形药柱进行了形状优化,以结构完整性最优为优化目标,以装填分数为约束条件,得到了Von mises应变最小且面积装填分数不小于0.85的药柱形状。所提出的方法可方便地应用于各种固体火箭发动机装药设计。     

固体推进剂药柱松弛模量随机粘弹性有限元分析

为了研究性能参数的分布对药柱结构完整性的影响，以不可压缩粘弹增量有限元和摄动法为基础，采用局部平均方法对随机场进行离散，发展了一种松弛模量随机粘弹有限元方法，讨论了模量的随机性对结构分析的影响。对药柱进行随机模拟，程序实施简单，计算效率和精度较高。     

Preliminary design and optimization of slotted tube grain for solid rocket motor

In this paper,design and optimization technique of slotted tube grain for solid rocket motors has been discussed.In doing so,the design objectives and constraints have been set,geometric parameters identified,performance prediction parameters calculated,thereafter preliminary designs completed and finally optimal design reached.Geometric model for slotted tube grain configuration has been developed.Average thrust has been taken as the objective function with constraints of burning time,mass of propellant,fixed length and diameter of chamber case.Lumped parameter method has been used for calculating the performance prediction parameters.A set of preliminary designs has been completed and an analysis of these results conducted.Although all the preliminary results fulfill the design requirements in terms of objective function and constraints,however in order to attain the optimal design,Sequential quadratic programming optimization technique has been adopted.As the slotted tube grain geometry is totally dependent upon various independent variables and each of these variables has a bearing on explicit characteristic of grain designing,hence affects of the independent variables on performance parameters have been examined,thus variation laws have been developed.Basing on the variation laws and the analysis of preliminary design results,upper and lower limits have been defined for the independent geometric variables and an initial guess provided for conducting optimization.Results attained exhibits that an optimal result has been attained and the value of objective function has been maximized.All the design constraint limits have also been met while ensuring sound values of volumetric loading fraction,web fraction and neutrality.This methodology of design and optimization of slotted tube grain for solid rocket motors can be used by engineers as a reference guide for actual design and engineering purposes.      

固体推进剂药柱不确定结构分析及方法比较

针对复合固体推进剂力学性能参数的不确定性对固体火箭发动机药柱结构分析的影响,使用软件ANSYS parametric design language(APDL)建立了受固化降温载荷和压力载荷联合作用下药柱结构的参数化有限元模型.在此基础上,分别应用蒙特卡洛法和响应面法,研究了复合固体推进剂热膨胀系数与初始泊松比的随机分布对药柱结构有限元分析的影响,并对两种方法得到的概率分析结果进行了对比.结果表明:复合推进剂热膨胀系数和初始泊松比微小的变化会对结构分析结果产生较大的影响;药柱结构响应对初始泊松比更为敏感.在药柱结构有限元分析时考虑推进剂力学性能参数的不确定性十分必要.通过对两种不确定结构分析方法的比较发现,响应面法得到的分析结果与蒙特卡洛法得到的分析结果十分接近,且分析效率远高于蒙特卡洛法.      

Design and optimization of solid rocket motor Finocyl grain using simulated annealing

The research effort outlined the application of a computer aided design(CAD)-centric technique to the design and optimization of solid rocket motor Finocyl(fin in cylinder) grain using simulated annealing.The proper method for constructing the grain configuration model,ballistic performance and optimizer integration for analysis was presented.Finocyl is a complex grain configuration,requiring thirteen variables to define the geometry.The large number of variables not only complicates the geometrical construction but also optimization process.CAD representation encapsulates all of the geometric entities pertinent to the grain design in a parametric way,allowing manipulation of grain entity(web),performing regression and automating geometrical data calculations.Robustness to avoid local minima and efficient capacity to explore design space makes simulated annealing an attractive choice as optimizer.It is demonstrated with a constrained optimization of Finocyl grain geometry for homogeneous,isotropic propellant,uniform regression,and a quasi-steady,bulk mode internal ballistics model that maximizes average thrust for required deviations from neutrality.     

基于蚁群算法的固体火箭发动机总体参数优化

为建立一种支持连续域、离散域混合变量的优化算法以用于固体火箭发动机总体参数优化,改进了基本蚁群算法,融入"网格划分"、"哑元化"和"变尺度局部搜索"三种策略,以改进算法的寻优性能和使用范围,其中局部搜索算法仍采用蚁群算法。使用了几个较具欺骗性的经典测试函数对改进蚁群算法进行了测试,计算结果表明改进蚁群算法找到全局最优值的概率较大。应用改进蚁群算法对固体火箭发动机总体设计中的两个重要总体参数——燃烧室工作压强和喷管面积比,进行了优化求解,获得了满意结果。诸算例的优化结果表明,该改进蚁群算法具有支持混合变量,全局寻优性能稳定和搜索精度高的优点,对工程优化设计问题具有较好的寻优性能和更强的适用性。     

High-precision shape approximation low-thrust trajectory optimization method satisfying bi-objective index

The shape approximation method has been proven to be rapid and practicable in resolving low-thrust trajectory; however, it still faces the challenges of large deviation from the optimal solution and inability to satisfy the specific flight time and fuel mass constraints. In this paper, a modified shape approximation low-thrust model is presented, and a novel constrained optimization algorithm is developed to solve this problem. The proposed method aims at settling the bi-objective optimization o...     

固体装药结构界面应力分析

研究了基于热黏弹性接触理论计算固体装药结构界面应力的数值方法,给出了一种快速判断界面是否脱黏的工程实用方法.以某固体装药结构为例,采用接触算法模拟固体装药多层结构复杂的边界条件,计算了挂飞工况下固体装药结构应变场特征,研究了壳体/绝热层界面应力的分布规律,结果表明:应变场云图符合工程实际,壳体/绝热层界面黏接良好,不会发生脱黏现象.      

含硼推进剂固冲发动机补燃室响应面优化设计

影响含硼推进剂固体火箭冲压发动机补燃室燃烧效率的因素很多,且各因素对燃烧效率的影响很难用精确的解析函数式来表示.首先建立了发动机补燃室内两相湍流燃烧数值模拟模型,然后提出了选用基于正交多项式的响应面方法来解决含硼推进剂固体火箭冲压发动机补燃室结构优化问题.这种方法可以减少为得到近似函数式而对补燃室流场进行计算的次数,能比较方便地对固体火箭冲压发动机补燃室各个参数进行优化与分析.      

HTPB推进剂湿热老化规律及损伤模式实验

通过HTPB推进剂湿热老化实验,采用测定单轴定速拉伸条件下标准哑铃形试件声发射(AE)信号的方法,结合扫描电镜(SEM)断面观察结果,对HTPB推进剂的湿热老化规律和损伤模式进行了研究,给出了一个描述湿热老化性能变化规律的三阶段模型。实验研究表明:声发射信号累积计数对时间的导数的大小对应基体开裂、脱湿和宏观断裂三种损伤模式;同时水份破坏粘合剂和氧化剂的界面是导致脱湿关键因素,且水份在推进剂中的浓度与脱湿严重程度呈正相关。     

固体推进剂药柱泊松比随机粘弹性有限元分析

为了研究泊松比的分布对固体推进剂药柱结构分析的影响，发展了一种地不可压缩材料的粘弹增量有限元方法，进行了泊松比随机粘弹性有限元的研究，要用局部平均方法对随机场进行离散，给出了二阶摄动有限 元变异方程。算例表明，对药桩进行随机模拟，计算效率和精度较高。     

HTPB固体推进剂老化性能检测新方法

引入了光致正电子湮灭分析方法 （PIPA,Photon Induced Positron Analysis）,对HTPB固体推进剂老化性能进行检测研究。介绍了PIPA的原理、PIPA试验平台的搭建以及PIPA的数值处理方法,并用511KeV能谱的FWHM值ε（半高宽,Full Width Half Maximum）表征HTPB固体推进剂老化引起的微观变化,所得结论与固体推进剂的常规测试一致,证明了PIPA用于固体推进剂老化性能无损检测的可行性。     

推力室结构力学分析与优化设计

针对某液体火箭发动机推力室建立了参数化模型,使用有限元方法分析结构固有频率和振型,并进行了模态试验验证.采用最优拉丁超立方法进行计算机数值试验设计,得到了结构质量和1阶固有频率对于设计变量的敏感性,对于优化设计过程具有指导意义.使用NSGA-Ⅱ算法开展多目标优化设计,得到了同时满足静力学与动力学设计要求的推力室结构最优设计方案.最优设计方案的推力室质量减轻了9.1%,1阶固有频率值提高了22.6%,结果表明该方法能有效提高推力室的力学性能.      

含裂纹药柱老化结构分析

为讨论不同贮存年限的含裂纹固体火箭发动机药柱的稳定性,基于黏弹性断裂力学,采用有限单元法,于药柱星角裂纹尖端处设奇异裂纹元,计算了弹射和点火情况下的J积分,对比了不同形状和不同贮存年限裂纹J积分的变化.结果表明:发动机在弹射工况下,裂纹J积分随贮存年限的增加而减小,裂纹的扩展机会越小;在点火工况下,裂纹J积分随着贮存时间的增加而增大,裂纹的扩展机会越大,裂纹不稳定.      

复杂型面固体装药结构的快速建模技术

高质量的有限元网格是保证计算精度的前提和基础。固体装药结构型面极其复杂,这给有限元的离散带来了很大的困难,为此需要开展快速建模技术研究。快速建模思想是针对固体装药结构具有循环对称的特点,基于CAE软件,对于其中子结构将其分割成具有单一几何拓扑型式的组合体,方便地实现拉伸、映射或者扫掠操作,获得精度较高的结构化网格。针对某一典型星形内孔固体装药结构,详细阐述了快速建模的核心技术,数值模拟了固化降温过程中固体装药结构的应力应变场特征。快速建模技术对于其他类似的固体装药结构有限元离散具有很好的借鉴和参考价值。     

降低颗粒粘结高燃速推进剂初始压强峰的途径

为降低颗粒粘结高燃速推进剂发动机试验时的初始压强峰,分别采用降低点火药量,改变燃喉比、燃通比,内外表面涂钝感剂和控制内、外燃通比之比小于1等方法进行了发动机试验,获得了每种条件下的压峰比数据。分析结果表明,采用控制内、外燃通比之比小于1的装填条件,可使其高燃速推进剂的压峰比小于1 3。     

基体特性对HTPB推进剂力学性能的影响

按工程生产工艺要求,制得hydroxyl terminated polybutadiene (HTPB)固化胶片,通过控制试验环境温度（-50、-35、-20、0、20、35℃）,得到了基于Prony级数形式的具有不同松弛特性的复合基体材料的松弛行为描述,为细观模型的建立提供了必要参数。随后基于分子动力学方法,结合具有内聚本构的黏接单元,建立了推进剂的细观计算模型。为验证所建数值模型的准确性,对固体推进剂在常温条件下进行宏观松弛力学试验,将仿真结果与试验数值的对比,试验结果与仿真结果相差在20%范围之内。最后对具有不同随机分布及不同基体松弛特性的推进剂细观模型进行有限元计算,结果表明:颗粒随机性不影响推进剂的宏观力学行为,而基体松弛特性显著影响固体推进剂的宏观力学性能,基体松弛特性获取环境温度与推进剂的宏观初始模量、延伸率以及强度均呈指数型关系。      

基于混合优化算法的固液发动机装药优化设计

为了减小固液发动机工作过程中氧燃比的变化导致的比冲等性能损失,提出基于差分进化和克隆选择的混合优化算法,建立装药优化问题的优化模型和优化流程,采用惩罚函数处理约束条件,对某型固液发动机进行了装药优化和分析.结果表明该优化算法和流程性能良好,优化后发动机的性能得到了明显提高,减小了余药质量分数和工作压强,改善了燃烧室和喷管的工作环境,且平均比冲提高了1.2%.      

提高高燃速丁羟推进剂低温伸长率研究

运用单向拉伸、交联密度测试、动态力学分析(DMA)等实验手段，研究了IPDI丁羟高燃速推进剂低温伸长率偏低的问题。结果表明：由于固化剂IPDI的分子结构特点和低反应活性造成粘合剂体系固化反应速度上的差别，加上防老剂H的刚性和物理交联作用使该类推进剂低温抗拉强度过高，是造成该类推进剂低温伸长率偏低的主要原因。在此基础上，通过添加网络调节剂，改善了推进剂粘合剂相的网络结构，解决了该问题。