2018级

硕士毕业论文

论文题目：飞艇内置氦气囊非饱和形态试验与数值分析
研究生：邹鹏宇
指导老师：陈务军 教授
学科专业：结构工程
摘要
        飞艇在起飞、巡航与降落时，氦气囊会受环境因素和控制因素影响发生形态变化，引起浮力大小和浮心位置改变，进一步地会影响艇身姿态和飞行控制。为研究硬式飞艇内置氦气囊的形态特征和变化规律，通过充气与泄气试验模拟飞艇起飞与降落过程中氦气囊的形态变化，并对氦气囊泄气试验开展了数值模拟分析。
        首先，针对一种新型氦气囊囊体材料的应用需求，开展了一系列力学性能试验，包括单轴拉伸强度试验、单轴循环拉伸试验、双轴循环拉伸试验和双轴剪切试验，建立了正交各向异性线弹性材料本构模型。试验测得：材料经向单轴拉伸强度为10.90N∙mm^-1，单轴拉伸极限应变为23.71%，弹性模量为53.62N∙mm^-1，泊松比为0.12；材料纬向单轴拉伸强度为9.92N∙mm^-1，单轴拉伸极限应变为30.44%，弹性模量为45.61N∙mm^-1，泊松比为0.10；材料剪切模量为12.49N∙mm^-1；以上材料力学参数可为工程设计应用提供参考。
        其次，设计并研制了双半椭球体氦气囊及其试验装置，提出了氦气囊浮力测量方法和充盈度控制方法，完成了氦气囊充气与泄气试验。试验结果表明：充气过程中，上下半椭球膜面先向上升起，随后上半椭球膜面沿环向膨胀至饱满形态，最后下半椭球膜面下沉并沿环向膨胀至饱满形态；泄气过程中，下半椭球膜面先沿环向收缩并向上升起，随后上半椭球膜面开始沿环向收缩，最后上下半椭球膜面同时向下塌陷；试验揭示了氦气囊浮力作用机理与非饱和形态变化规律。
        最后，基于向量式有限元法提出了飞艇氦气囊非饱和形态分析方法，考虑几何大变形、边界非线性和压力梯度，对双半椭球体氦气囊进行了结构动力学分析。分析结果表明：氦气囊泄气模拟结果与试验结果一致，该方法能够有效地模拟氦气囊泄气过程的非饱和形态。
关键词：内置氦气囊；飞艇；非饱和形态；充盈度；向量式有限元法
 
UNSATURATED MORPHOLOGY TEST AND SIMULATION OF AIRSHIP INSIDE HELIUM BAG
Abstract
        During the air ship ascent, cruise and landing process, the helium bag will undergo morphology changes due to environment factors and control factors, causing changes in the value of buoyancy and the position of the buoyancy center, which will further affect the hull attitude and flight control. In order to study the unsaturated morphology characteristics and change rules of rigid airship inside helium bags, the helium bag morphology changes of air ship ascent and landing process were simulated through the inflation and deflation test, and numerical simulation analysis was carried out for the helium bag deflation test.
        First, for the application requirements of a new type of helium bag material, the study on the mechanical properties was carried out, including uniaxial tensile strength test, uniaxial cyclic tensile test, biaxial cyclic tensile test and biaxial shear test. And the constitutive model of orthotropic linear elastic material was established. The test results show that in the warp direction, uniaxial tensile strength is 10.90N∙mm^-1, the uniaxial tensile ultimate strain is 23.71%, the elastic modulus is 53.62N∙mm^-1, and the Poisson's ratio is 0.12; in the weft direction, the uniaxial tensile strength is 9.92N∙mm^-1, the uniaxial tensile ultimate strain is 30.44%, the elastic modulus is 45.61N∙mm^-1, and the Poisson's ratio is 0.10; the shear modulus of the material is 12.49N∙mm^-1. The above material mechanics parameters can provide references for engineering design and applications.
        Secondly, a double semi-ellipsoid helium bag and its test device were designed and manufactured, the buoyancy measurement method and filling degree control method of helium bag were proposed, and the helium bag inflation and deflation tests were carried out. The tests results show that during the inflation process, the upper and lower semi-ellipsoidal membranes first rise upward, and then the upper semi-ellipsoidal membrane expands to a full form in the ring direction, and finally the lower semi-ellipsoidal membrane sinks down and expands in the ring direction to a full form; during the deflation process, the lower semi-ellipsoid membrane first shrinks in the ring direction and rises upward, then the upper semi-ellipsoid membrane surface begins to shrink in the ring direction, and finally the upper and lower semi-ellipsoid membranes collapse downward to the vacuum state at the same time. The tests revealed the buoyancy mechanism of the helium bag and the change rules of unsaturated morphology.
        Finally, based on the vector finite element method, an unsaturated morphological analysis method of the airship helium bag was proposed. Considering the large geometric deformation, boundary nonlinearity and pressure gradient, the structural dynamics analysis of the double semi-ellipsoid helium bag was carried out. The analysis results show that the simulation results of helium bag deflation process are consistent with the test results, and this method can accurately simulate the unsaturated morphology of the helium bag deflation process.
Key Words: inside helium bag; air ship; unsaturated morphology; filling degree; vector finite element method
 
论文题目：SMA弹簧驱动空间柔性操控臂结构设计与研究
研究生：滕亚军
指导老师：陈务军 教授
学科专业：结构工程
摘要
        柔性机械臂灵活性好、运动范围广和可以在非结构化环境中工作，有越来越广阔的研究与应用前景。本文在研究形状记忆合金（shape memory alloy, SMA）弹簧性能的基础上，研制了一种SMA弹簧驱动柔性操控臂，并对柔性操控臂运动学和动力学分析以及实验研究。
本文使用形状记忆合金弹簧设计了新一代的柔性操控臂体系，基于几何法建立了运动学模型，基于拉格朗日法建立了动力学模型，制作了单节柔性操控臂样机并测量了其在电流作用下的转动角度，制作了多节的柔性操控臂样机并通过对特定SMA弹簧通电实现了S和J型运动姿态。
        首先，基于Tanaka系列模型推导了一维SMA弹簧剪切应力应变关系（SMA的剪应力、剪应变和温度之间的关系），结合弹簧的力学性能和电流加热升温公式，得到了SMA弹簧力、变形与通电时间的关系。采用SMA弹簧无应力状态的实验验证了所得的SMA弹簧本构模型的正确性，1.25A和1.5A理论与实验值相差最大分别为7.9%和14.6%。
        其次，将由智能材料驱动的柔性机器人与正八面体可变几何桁架体系结合起来，采用正八面体可变几何桁架体系为理论基础，将以并联SMA弹簧作为结构驱动体系，设计了单节柔性操控臂，将单节的柔性操控臂首尾相连设计了柔性操控臂机构。基于设计的柔性操控臂机构，建立了其单节与多节正逆向运动学关系。用MATLAB计算了在关节转动时SMA弹簧的长度变化，在限定关节角度的工作空间，研究了多节柔性操控臂的逆运动学解法。
        再次，分析了单节柔性操控臂的动能、弹性势能和重力势能，基于拉格朗日法得到了动力学方程。针对单节柔性操控臂，通过MATLAB编程计算得到单节柔性操控臂中SMA弹簧的弹簧长度、驱动力、马氏体体积分数等，分析了SMA弹簧在关节转动下的动力响应。通过Adams仿真，仿真与理论对比得到：转动角度与理论计算相差9％与7.5％。对于SMA弹簧长度，三根SMA弹簧仿真计算值与理论值分别相差最大为1.3％、1.9％与3.6％。通过算例分析SMA弹簧在不同关节转动下的动力响应，为后续SMA弹簧控制和柔性操控臂实验研究奠定基础。
        最后，制作了单节柔性操控臂样机得到了在电流为0.8A、1.0A和1.2A时柔性操控臂的转动角度随通电时间的变化情况，0.8A时最大转动角度约为40°，1.0A与1.2A最大转动角度约为80°。设计并制作了多节柔性操控臂，设计了其硬件控制系统，通过对特定SMA弹簧通电实现了S和J型运动姿态。实验测得了J姿态通断电时X、Z轴的坐标与时间的关系，X向的最大变化量为265.4 mm，Z向最大变化量为140 mm。
关键词：形状记忆合金（SMA）；柔性操控臂；运动学；动力学；Adams
 
STRUCTURE DESIGN AND RESEARCH OF FLEXIBLE MANIPULATOR ACTIVATED BY SMA SPRING
Abstract
        The flexible manipulator has attracted considerable attention in recent decades because of its flexibility, wide range of motion and the capability of working in unstructured environment. In this paper, a new flexible manipulator is designed and activated by parallel shape memory alloy (SMA) springs. The kinematics and dynamics of the flexible manipulator are established and experimental research on the flexible manipulator prototypes are carried out.
Firstly, based on Tanaka constitutive of SMA, a one-dimensional shear stress-strain relationship of SMA spring is simplified. Combined the mechanical properties of spring and the heating formula of current heating, the relationship between SMA spring force, deformation and electrifying time is obtained. The correctness of the constitutive model of SMA spring is proved by the experiment in stress-free state.
        Secondly, combined the flexible manipulator robot with the octahedral variable geometry truss system, a flexible unit is designed and activated by parallel SMA springs. The flexible manipulator is designed by connecting the flexible unit head to end. The forward and inverse kinematics models of the driving space and the joint space， the joint space and the operation space are established. The workspace of the flexible manipulator is studied, and the multi-section inverse kinematics solution based on the geometric and the trajectory planning method is given.
        Thirdly, the kinetic energy, elastic potential energy and gravity potential energy of a flexible unit are analyzed, and the dynamic equation is obtained based on Lagrange method. The dynamic characteristics of the flexible unit are analyzed. The length, driving force and martensite volume fraction of SMA spring are obtained by MATLAB programming. The dynamic response of SMA spring under joint rotation is analyzed. The results of ADAMS simulation are in good agreement with theoretical calculations.
        Finally, fabrication and structure of the flexible manipulator are described. The prototype of the single-section flexible manipulator is built and the rotation angle under electric current is measured. A multi-section flexible manipulator is built and its motion mode is studied.
Key Words: Shape memory alloy (SMA); kinematics; Flexible manipulator; dynamics; Adams

博士毕业论文

论文题目：大跨度气承式膜结构风振响应与流固耦合特性研究
研究生：阴悦
指导老师：陈务军 教授
摘要
        近年来，气承式膜结构凭借其装卸速度快、内部空间大且连续、造型优美、气密隔绝性好、节能环保等优势逐渐在大型体育场馆、展览场馆等民用建筑和仓储类建筑、污染处理类建筑、煤棚等工业建筑中得到广泛应用。然而，目前针对大跨度气承式膜结构的设计理论还不够成熟，其结构风振响应和结构动力性能有待进一步研究。规范中建议设计方法未考虑该结构显著的流固耦合效应，计算结果与实际工程经验存在一定差异。设计方法的不足和不合理的设计方案将导致工程安全事故和经济性缺失。因此，本文结合气承式膜结构实际工程，开展了现场监测与分析、风振响应模拟与流固耦合研究，以提高对大跨度气承式膜结构风振响应特性的认识，并完善其设计方法。
        首先，本文以斜向交叉索网加劲的大跨度气承式膜结构为对象，设计、开发、并建成了专门针对该结构的健康监测系统，对该结构进行了长期、全面的风振响应监测。其次，基于台风作用下的结构响应结果，分别采用时域和频域分析方法研究了气承式膜结构的风振响应特点，揭示了结构变形和钢索应变的风致动力响应规律。然后，基于多种环境激励模态识别方法，识别了频率、阻尼比等重要的模态信息，并建立流-固耦合预应力模态分析模型验证，研究结构模态振型特征以及内压、附加气动力、加劲索网对结构模态的影响。
        接下来，基于由现场监测结果分析得到的结构风振响应特点，结合k-ε湍流模型和线性模态叠加时程分析法，提出可面向工程应用的大跨度气承式膜结构风振响应计算方法，以相对简化的方式考虑了流固耦合效应对结构风振响应的影响，研究了结构整体动力响应特点以及监测难以测量的结构力学性能（如膜面应力、索网拉力等）。  
最后，为了解决上述简化方法无法反映脉动风空间湍流特征的问题，对数值分析模型进行精细化建模，运用大涡模拟和分区弱耦合双向求解的流固耦合方法对大跨度气承式膜结构在非定常流中的瞬时风致动力行为进行了数值模拟，从时域和频域两个维度详细分析了气承式膜结构在不同风速的来流作用下的瞬态流固耦合特性，为后续进一步探索气承式膜结构内压动态控制方案奠定了基础。
        本文的相关研究结果不仅有助于提高对大跨度气承式膜结构风振响应和流固耦合特性的认识，亦可为大跨度气承式膜建筑的结构分析方法、设计理论和技术规程完善提供有益参考。
关键词：气承式膜结构，风振响应，结构健康监测，模态分析，流固耦合
STUDY ON WIND-INDUCED RESPONSE AND FLUID-STRUCTURE INTERACTION PROPERTY OF LARGE-SPAN AIR-SUPPORTED MEMBRANE STRUCTURES
Abstract
        Due to the unique advantages containing fast installation and disassembly, spacious and continuous internal space, air tightness, graceful appearance, as well as excellent performance in energy saving and environmental protection, air-supported membrane structures have been widely applied in spatial structures with large-span over recent years including public facilities like stadiums and exhibition halls, as well as industrial buildings for storage and pollution treatment. However, current design theories for large-span pneumatic structures are not fully developed and wind-induced response, and dynamic structural properties need to be further investigated. In addition, as for the wind-induced response of air-supported structures, calculation theory recommended in the codes does not consider the significant fluid-structure interaction effects, thus some discrepancies have been discovered between observation results in engineering practice and calculated results using current codes for air-supported membrane structures. Deficiency of design methods or unreasonable design plans lead to safety accidents or lack of economy. Therefore, based on an actual engineering of air supported membrane structures, this study carries out systematic monitoring and analysis, wind-induced response simulation and fluid structure coupling research to reinforce the understanding of the wind-induced response of air-supported membrane structures, and also to improve the design methods.
        At first, a typical large-span air-supported structure with diagonal reinforced cable nets is selected to investigate in this research. A comprehensive structural health monitoring system for these kinds of structures were specially developed and installed. Then a full-scale and long-term monitoring was carried out. Based on the monitoring records under the effects of typhoon, different methods in both time and frequency domains were used to perform research on wind-induce response of the air-supported structure. Results reveal the dynamic properties of structural deformation and cable strain of the structure under unsteady wind loads. Moreover, different kinds of operational model analysis methods were adopted to identify critical mode information including natural frequencies and damping ratios. Numerical modal analysis considering prestress and fluid-structure interaction (FSI) was developed to verify the identification results based on monitoring data. In this way, full information of modal shapes is obtained. The effects of internal pressure, additional aerodynamic force, and cable nets on structural dynamic properties are also studied.
        Based on the wind-induced vibration response characteristics obtained from the analysis of monitoring results, k-ε turbulence model and linear modal superposition method were combined to propose a approach, which can be applied for engineering practice, to analyze the wind-induced response of pneumatic structures. This method takes the effects of FSI effects on the wind-induced structural response into account in simplified way. By this model, overall structural response and structural properties which are difficult to be directly monitored can be investigated with lower computational cost, especially membrane stress and axial force of wire rope nets.
Finally, in order to solve the problem that spatial turbulence features of gust wind can not be accurately reflect in the simplified model, a partitioned, weak, two-way FSI model using large eddy simulation strategy was proposed to study the transient wind-induce response of air-supported structure under unsteady flow. This model is finely established taking into account the characteristics of actual flow domain and structure features. Transient FSI performance of the structure under the unsteady flow with different velocity was completely analyzed in both time domain and frequency domain. Relative conclusions lay a foundation for further exploration concerning the dynamic control scheme of internal pressure of air supported membrane structures.
        Overall, results and conclusions in this research can not only help deepen the knowledge of the wind-induced dynamic response of air-supported structures, but also be useful reference for the development of analysis method and design theory for this kind of structures, as well as the improvement of standards and codes.
Key Words: air-supported membrane structures, wind-induced response, structural health monitoring, modal analysis, fluid-structural interaction