2014级

2014级 硕士毕业论文
论文题目：四枚缎纹编织复合材料力学性能试验与多尺度有限元分析
研 究 生：康雄建
指导老师：陈务军 教授
学科专业：结构工程
 
中文摘要:
  织物复合材料具有超强的可设计性、均匀的面内性能、结构的稳定性，作为一种高性能复合材料，广泛应用于航空航天、船舶、汽车、建筑等领域。
  本文以四枚缎纹织物复合材料为研究对象，运用试验和有限元数值计算等方法对织物复合材料的力学行为进行了研究。主要内容包括单轴拉伸强度试验研究、单轴拉伸循环试验研究、面内剪切试验研究、四点弯曲试验研究以及单胞结构多尺度有限元数值分析。
   首先，对四枚缎纹编织复合材料进行了单轴拉伸强度试验和低周循环拉伸试验。针对具有波浪状表面的编织材料，提出了用每根纱线能承受的拉断强力和单位宽度所能承受的拉断强力来表征材料的强度。在低周循环试验中，分别研究了织物材料的初次加载弹性模量和后续加载弹性模量，并考察了在不同循环次数下，滞回环面积的变换情况。试验结果对材料的工程设计具有参考价值。
   其次，为研究四枚缎纹编织复合材料的面内剪切性能，首次设计并制作了适用于极薄复合材料面内剪切测试的夹具，并提出了相应的试验方案。试验得到了复合材料的面内剪切刚度。
   再次，对四枚缎纹编织复合材料进行了四点弯曲试验。得到了材料的弯曲刚度和失效时的曲率，结果表明同一种编织密度的复合材料的经、纬向试件在发生失效时的曲率基本一致。
   最后，采用金相显微照相技术，得到了四枚缎纹编织复合材料的横截面细观结构图像；基于对图像的分析，得到了四枚缎纹编织结构纱线束截面几何形状尺寸、纱线束间距、材料厚度等信息，并以此为依据建立单胞有限元模型。采用域分解方法对整体域和纤维域在空间位置和网格节点进行耦合，在整体域边界上施加周期性边界条件，保证了有限元单胞模型的变形协调和位移连续。通过对单胞模型施加单位应变，数值计算了单胞模型的刚度矩阵，并利用试验结果验证刚度矩阵的主对角元素。最后利用得刚度矩阵数值计算了相应结构的力学响应。
   关键词：四枚缎纹编织复合材料，单轴拉伸强度试验，低周循环试验，面内剪切试验，四点弯曲试验，细观结构，单胞多尺度有限元分析
 
 
 
Experimental study and multi-scale FEM analysis of 4-harness satin woven composites
ABSTRACT 
 
   Woven composites have good properties of designability, uniform in-plane properties and structural stability. As an advanced composite material, woven composite is widely used in aerospace, ship, auto and building industry.
4-harness satin woven composite is studied in this paper, experiment method and FEM method are performed to investigate mechanical property of the composite. Main content of this paper includes uniaxial tensile strength test, cycle tensile test, in-plane shear test, 4-point bending test and FEM analysis of a unit cell which can be representative of the whole structure.
   Firstly, the uniaxial tensile strength test and cycle tensile test are performed. In case of the woven composite with undulate surface, the ultimate force of yarn andultimate force per unit width are proposed to be used for characterizing the tensile strength of the woven composite.First loading elasticity modulus and subsequent loading elasticity modulusare studied during cycle tensile test, and the change of hysteresis loop areas is investigated during cycle tensile test. The results of tests are valuable to practical engineering application.
   Secondly, the in-plane shear property of 4-harness satin composite is studied. The composite is extremely thin, existing test fixture can’t be applied to the single-layer composite. Based on the principle of shear test,
an in-plane shear test fixture that can be applied to the extremely thin composite is designed for the first time, and a relevant test program is also proposed. And in-plane shear test is performed using the designed fixture.
Subsequently, 4-point bending test is carried out to investigate the bending mechanical property. Bending stiffness and the curvature when local buckling appears are gained. The results show that curvatures of warp and weft specimen when local buckling appears are almost the same.
   Finally, mesostructure image of cross section of the 4-harness satin woven composite is obtained by optical microscopy. By studying the mesostructure image, geometric information is obtained, such as the geometrical dimensions of cross section of warp and weft tows and the distance between tows along warp direction and weft direction. Based on the obtained geometric information, arepresentative unit cell is modeled by ABAQUS. Domain decomposition method is used to guarantee that global domain and fiber domain are coupled in spatial position and mesh nodes. Periodic boundary conditions are applied to the global domain, which guarantee that deformation is coordinating and the displacement is continuous between the corresponding nodes. A unit strain is applied in each case, thus one column of the ABD matrix is obtained. Finally whole ABD matrix is obtained and the results of experiment are used to verify the principal diagonal elements of ABD matrix. Finally, ABD matrix is used to calculatesome structures.
 
 KEY WORDS: 4-harness woven composite, uniaxial tensile test, cycle tensile test, in-plane shear test, 4-point bending test, mesostructure, FEM analysis of unit cell

论文题目：形状记忆材料的力学性能研究与盘绕式空间伸展臂的研制
研 究 生：游晋
指导老师：陈务军 教授
学科专业：结构工程
 
中文摘要:
  智能材料与结构是一门新兴的综合科学，是当前发展的国际前沿学科之一，受到人们越来越多的关注。形状记忆材料是智能复合材料的主要组成部分之一，具有形状记忆效应，可作为新型航天材料应用于空间可展开结构。本文针对应用于空间可展开结构的形状记忆材料开展研究，表征了形状记忆聚合物、形状记忆合金基本力学性能，重点考察了四枚缎纹编织增强环氧树脂复合材料的动态力学性能。在此基础上，完成了基于形状记忆合金形状记忆效应的主动器设计、研制和初步性能验证。根据某探测器论证，设计了一种新型盘绕式伸展臂，对其进行了结构设计和模态分析。
  首先，作者利用研制的形状记忆聚合物，分别进行了动态力学性能试验和常温下的单轴拉伸力学性能试验，得到了储能模量（E）、损耗角正切值（tanδ）与温度（T）的关系曲线，利用DIC数字散斑技术测得了形状记忆聚合物的应力场和位移场，计算得到了泊松比和剪切模量。
  其次，对三种四枚缎纹编织增强复合材料分别进行了动态力学性能试验，试验表明该复合材料相变前后储能模量相差超过一个量级，具有良好的形状记忆能力。在环氧树脂中植入碳纤维织物增强复合材料会导致玻璃化转变温度（Tg）、tanδ降低，而E显著增强，同一种形状记忆复合材料经、纬向的Tg、tanδ基本相同，但E相差很大，比较了由tanδ和El曲线峰值确定的Tg之间相互关系。
再次，对形状记忆合金分别进行了示差扫描热分析试验和单轴循环拉伸力学性能试验，基于形状记忆合金设计了一种智能复合材料主动器，并进行了初步功能试验，对试验存在的不足进行了分析。
  最后，根据某探测器论证，设计了一种分段展开的盘绕式伸展臂，阐明了伸展臂各部分相互关系，分析了加劲索、加劲索预应力、杆件截面对模态的影响，对组装的伸展臂进行了模态试验，测得了三种激励模式下的模态和固有频率，可为工程设计提供依据。
 
  关键词：形状记忆材料，可展开结构，四枚缎纹碳纤维织物，动态力学性能试验，单轴拉伸试验，单轴循环拉伸试验，示差扫描热分析试验，盘绕式空间伸展臂
 
 
     DEVELOPMENT OF A COILABLE SPACE MAST AND STUDY ON MECHANICAL
            PROPERTIES OF SHAPE MEMORY MATERIALS
                    ABSTRACT
 
  Intelligent Materials and Structures is a new comprehensive science, it is one of the international advanced subjects and gets more and more attentions. Shape memory material is one of the main components of intelligent composites. It has shape memory effect and can be used as a new space material for deployable space structures. This thesis discuss on shape memory materials, characterized shape memory polymer and shape memory alloy fundamental mechanical properties, focuses on the dynamic mechanical properties of 4-harness stain carbon fiber weave reinforced composites. On this basis, a shape memory actuator was designed, fabricated, a preliminary performance was demonstrated. Otherwise,on the basis of particular space probe mission requirement, designed a new high precession coilable space mast and analysed the influencing factors of modal.
  First of all, uniaxial tensile tests underconstant temperature andthe dynamical mechanical analysis tests of shape memory polymer were carried out respectively.The storage modulus-temperature and the tangent of loss angle-temperature curves were obtained. The author was used VIC-2D digital speckle technique in uniaxial tensile process for obtainingthe displacement field and strain field. Based on the displacement field, calculated the shear modulus and the Poisson ratio of shape memory polymer.
  Secondly, three different kinds of 4-harness satin carbon fiber weave reinforced composites were carried out the dynamical mechanical analysis test respectively. The experimental results indicate that 4-harness satin carbon fiber weave reinforced composites have good memory capacity. The SMP involved with carbon fiber weave reinforced composites will lead to Tg and tanδ reduced, but E is significantly enlarged. Tg and tanδ of the same 4-harness satin carbon fiber weave reinforced composites are almost in common, but E differ greatly in its warp direction and weft direction. The author compared the value ofTg, which was calculated by the maximum value through the curve of tanδ and El.
  Thirdly, differential scanning calorimetry test and uniaxial cyclic tensile test of shape memory alloy were carried out respectively. The author designed an intelligent composites actuator, which based on shape memory alloy’s effect. The author carried on the preliminary test and analysis to the test existence problems.
  Finally, on the basis of particular space probe mission requirement, proposed a three-staged sequence extending coilable mast and illustrated the relationship and the function of each part. The author analysed the influence factors of modal, included the size of stiffening cables, the pre-stress of stiffening cable and cross section of horizontal and vertical bars. The modal test of the assembled coilable mast is carried out, and measured the modal and natural frequencies of the three kinds of excitation modes. The presented work is valuable to the engineering designing.
 
  KEY WORDS:Shape memory material, deployable structure, 4-harness carbon fiber weave, dynamical mechanical analysis test, uniaxial tensile test, uniaxial cyclic tensile test,differential scanning calorimetry test, coilable space masts


论文题目：柔性充气操控臂的数值模拟与试验研究
研 究 生：刘彧
指导老师：陈务军 教授
学科专业：结构工程
中文摘要:
  充气膜结构是一种典型的张拉整体结构：外膜承受拉力，内充气体承受压力。在过去的几十年里，因为充气膜结构的一些诸如轻质、可压缩到很小的体积、较低的成本等优点，它的运用越来越流行。充气膜结构被广泛地应用于建筑、船艇、空间大型可展开天线和飞艇等许多的工程应用领域，而基于充气结构的操控臂是近些年发展起来的一种新的应用。这种柔性机械臂可以克服传统机械臂的缺点，并具有质量轻、易于储存收纳、抗冲击性好、物理碰撞安全、成本低等优点。
  本文提出一种新型柔性充气操控臂，直臂段和带有褶皱构造的关节均为充气膜结构。关节褶皱构造的几何形状类似于波纹式宇航服的关节，这种特殊的关节有着很好的柔性且可以实现较大的转动角度。针对这种新型充气操控臂结构的力学性能，本文进行了一系列试验和数值模拟研究。
首先，进行新型柔性充气操控臂的设计，包括整体概念设计，具有褶皱构造的充气关节的详细设计及实现方法，以及驱动充气操控臂转动的绳索驱动系统的详细设计及实现方法。
其次，对试验中制作样机所选定的柔性PVC膜材进行双轴拉伸和双轴剪切试验。鉴于直臂段的膜材处于双向张力状态而关节处的膜材处于褶皱状态，所以采用了不同的加载比例并用正交异性的假设计算得到了膜材在不同应力状态下的材料参数。利用Abaqus建立充气操控臂有限元模型并针对关节褶皱的成型过程及气臂的力学性能进行数值模拟和参数分析，模拟结果表明褶皱构造有效地降低了关节的驱动力矩，实现了其设计目标。
  再次，研制了与有限元模型具有相同几何尺寸的充气操控臂样机，并用弹簧、渔轮和高强渔线简易实现了关节驱动滑轮组。对充气操控臂样机开展功能和性能试验，试验与有限元的结果吻合很好，这样有限元建模的合理性和结果的准确性得到了验证。
  最后，基于体积控制法，利用LS-DYNA的airbag模型进行充气结构在瞬态载荷作用下的内压动态响应模拟。在实现ETFE气枕恒压模拟的基础上，进行了气枕在上表面作用阶梯正负压外载荷时的内压动态响应数值模拟，得到的内压波动曲线与试验曲线吻合较好。这样，恒压模拟方法的可行性得到了验证，且根据气枕上表面作用正负压（模拟实际结构受到风压或风吸作用）时上下层膜面的最大应力过程，分别提出了针对实际结构在风压或风吸工况下考虑膜材强度安全的设计原则。而充气操控臂在恒压条件下的内压动态响应也利用了此方法进行数值模拟。
  关键词：柔性充气操控臂，褶皱关节，双轴试验，驱动力矩，数值模拟，体积控制法，恒压模拟，内压动态响应
 
Numerical and Experimental Studies on Mechanical Behavior of a Novel Flexible Inflatable Manipulation Arm
ABSTRACT
 
  Inflatable membrane structure satisfies the principle of tensegrity, where the fabric skin is subjected to tension, while the inner pressurized air bears compression. Over the past few decades, owing to their unique mechanical properties, e.g. light weight, capable of being compressed into small packages, and low cost, the applications of inflatable structures are more and more popular. Inflatable structures have been widely used in many engineering applications such as buildings, boats, balloons, space antennas, and airship. Recently, the application of inflatable membrane structures has been extended to the area of robot manipulators and these flexible robot arms can overcome limitations of traditional ones because of their inherent features, e.g. light weight, low cost, and good crash safety.
  The current paper proposed a novel kind of inflatable manipulator which consists of inflatable tubes and inflatable joints with creases structure to allow flexible and large angle rotation. The geometric shape of inflatable joints proposed here looks like the bellows-type elbow of spacesuit. The current work carries out numerical and experimental studies to evaluate the mechanical performance of the inflated arm structure.
Firstly, the design of this novel inflatable manipulator is proposed, including the overall conceptual design, detailed design and implementation method of the special inflatable joint with creases structure. The arrangement and working principle of the tendon driven system are also described.
  Secondly, the biaxial tensile and shear tests are carried out to evaluate the elastic constants of the PVC-coated fabric membranes of the inflatable arm. Different load ratios are applied to evaluate the material properties of fabrics under various stress states. Hence, the material parameters of the PVC membrane under biaxial tension and wrinkle conditions are calculated based on the assumption of orthogonality. Finite element models are developed by the software Abaqus to simulate the forming process of the joint with creases and study the mechanical behavior of inflated arm structure. Results show that the creases structure can effectively reduce the actuation moment of the joint and therefore the design goal is achieved.
Thirdly, a prototype of the inflatable arm which has the same geometrical dimensions as the precious finite element model is designed and made to perform an experimental investigation on its mechnical performance. The accuracy of the numerical predictions is validated by the test data.
  Finally, based on the control volume method, the dynamic response of internal pressure of inflatable structure under transient load is simulated by using the airbag model of the software LS-DYNA. On the basis of the achievement of constant pressure simulation of ETFE cushion, the dynamic response of cushion internal pressure under external loads is simulated. Its results agree well with the experimental results, and therefore the feasibility of the simulation method of constant pressure is verified. According to the maximum stress process of the upper and lower membrane surface of the ETFE cushion, the design principle under wind pressure or wind suction condition is proposed respectively. And the dynamic internal pressure response of the inflatable manipulator under constant pressure condition is also simulated by this method.
KEY WORDS: Flexible inflatable manipulator, joint with creases, biaxial tensile and shear test, actuation moment, numerical simulation, control volume method, constant pressure simulation, dynamic response of internal pressure

论文题目：飞艇蒙皮织物膜材的力学性能试验研究
研 究 生：何世赞
指导老师：陈务军 教授
学科专业：结构工程
 
中文摘要:
  平流层飞艇在生态保护、水文监测、城市规划、高空预警与侦查、卫星中继等军用和民用方面都有巨大的价值。为了加快平流层飞艇的相关技术推进，我国制定了一系列的相关发展规划。为了保证平流层飞艇发挥最大效能，艇体需要做的很大，并且其工作环境平流层复杂多变，需要性能更高的新型蒙皮膜材才能满足使用要求。
本文以多种新型飞艇蒙皮织物膜材为研究对象，开展单轴拉伸、单轴循环、双轴拉伸、双轴剪切、DIC数字散斑技术等试验，对膜材进行全面的试验分析，综合利用理论模型对试验数据展开深入研究，同时对单、双轴试验异同、不同测量方式的差异进行了对比。
  首先，依据行业标准对膜材Uretek5876进行单轴拉伸强度试验和单轴循环试验，探究了不同形状、尺寸的试件对单轴强度和破坏形态的影响；验证了层合板正交各向异性理论对织物膜材的适用性和预测的准确度。
  其次，介绍了DIC数字散斑技术的基本原理和数学模型，提出了一种新的制作散斑的方法—水转纸散斑，对水转纸散斑和喷漆法散斑这两种散斑制作方法进行了对比，并对差异进行了分析。在四种不同类型的膜材上验证了水转纸散斑的有效性，同时得到了这四种膜材在拉伸、剪切试验中初始、中段、末段三个过程中的应变场。
  再次，进行膜材4297E双轴拉伸试验，选取七种基本应力比组合的基础上，同时考虑6种高应力比和3种低应力比，测得各应力比状态下弹性模量，通过单轴循环试验和DIC数字散斑技术测得膜材4297E的弹性模量和泊松比，进行了单双轴试验测得弹性常数的对比。
  最后，对新型飞艇蒙皮膜材4494ET进行了0.5 kN/m、1 kN/m、1.5 kN/m、2 kN/m、2.5 kN/m五种剪应力下的剪切循环试验，得到了剪应变加载时间变化曲线、剪应力-剪应变曲线、剪切模量；使用DIC数字散斑技术测得了剪切应变场，对于分析褶皱发展和结构变形具有重要参考价值。对单、双轴两种不同试验方法得到的剪切模量进行对比和分析。
 
关键词：织物膜材，单轴拉伸，弹性模量，数字散斑，剪切模量，双轴拉伸，双轴剪切，应变场
      EXPERIMENTAL STUDY ON MECHANICAL PROPERTIES OF
           ENVELOPE MATERIALS FOR AIRSHIPS
 
ABSTRACT
 
  The stratospheric airship has great value in the military and civil aspects such as ecological protection, hydrological monitoring, urban planning, high altitude warning and reconnaissance, satellite relay and so on. In order to promote the development of stratospheric airship, our country has formulated a series of related development plans. Because the stratospheric airship needs to be made very big and the working environment is complex, the performance of the membrane material of the airship is put forward higher request.
  In this paper, a variety of new type of airship skin fabric is studied, which is used to carry out the experiment of uniaxial tension, uniaxial cycle, biaxial tension, biaxial shearing, DIC digital speckle technique, etc.. Comprehensive test is used to analysis membrane material. Based on the theoretical model, the experimental data is studied deeply. The difference between single and double axis measuring method is compared.
  First, the uniaxial tensile strength and uniaxial cyclic test of the membrane material Uretek5876 are done based on industry standards to explore the effects of different shapes and sizes on the uniaxial strength and failure mode. The applicability and prediction accuracy of the laminate are verified by the theory of orthotropic laminates.
  Secondly, the basic principle and mathematical model of DIC digital speckle technique are introduced in this paper, this paper presents a new method for the manufacture of speckle, the difference of displacement field and strain field is compared with the method of making different speckle patterns. The effectiveness of water transfer paper was validated on four different types of membrane materials, four kinds of membrane materials of strain field is measured in the initial, middle and late process.
  Again, Biaxial tensile test is done on material 4297E, seven kinds of basic stress ratio combinations are selected, and 6 kinds of high stress ratio and 3 kinds of low stress ratio are considered. The elastic modulus under different stress ratio is obtained. The elastic modulus and Poisson's ratio of 4297E were measured by uniaxial cyclic test and digital speckle technique, the comparison of the elastic constants measured by uniaxial and biaxial tests was carried out.
  Finally, shear cyclic tests on the 4494ET of a new type of membrane material are carried out under five shear stress. The shear strain curves, shear stress shear strain curves and shear modulus are obtained. Comparison and analysis of shear modulus is done between uniaxial and biaxial test.
 
  KEY WORDS: Fabric membrane, uniaxial tension,elastic modulus,digital speckle, shear modulus, biaxial tensile test, biaxial shear test, strain field