【作者】 吴迪；

【导师】 任露泉； 庄庆伟；

【作者基本信息】 吉林大学 ， 工程硕士（专业学位）， 2018， 硕士

【摘要】 随着船舶、高铁、大飞机和卫星等领域的不断发展,工程装备的大型化和高速化的趋势对结构和材料的创新提出新的要求。在满足强度的情况下,减轻质量相当于降低能耗,提高生产经济性。具有高孔隙率的点阵结构,以其高比强度、优秀的散热能力和吸收声波等特点在越来越多的领域得到应用。尼龙材料的聚合方法和增强技术不断地发展,其力学性能已经可以比拟金属材料,在润滑不良或者易锈蚀的环境中,代替金属材料制造服役载荷不高的齿轮和轴承等部件。对尼龙材料点阵结构力学响应的试验研究将为点阵结构的优化设计和广泛应用起到一定的参考作用。本文综合分析点阵结构力学性能的国内外研究进展情况,提出三种胞元沿圆周阵列的环形点阵结构与相同截面积的管状结构进行对比,三种胞元分别是三角型、四边型和圆型,介绍了试件的形状和尺寸。借助有限元软件ANSYS Workbench分析每种结构受正应力和切应力时的应变响应,选取相同的取样点进行对比。接着以四边型点阵结构为例,以最小应变为优化目标对胞元尺寸进行多目标参数优化,得出胞元尺寸变化对应变响应的影响并分析了不同参数变化对应变响应的灵敏度。结合软件所用拟合方法的原理,推导出点阵结构的相对密度与应变响应的函数关系。优化后模型的拉伸应变降低了3.59%,扭转应变降低了1.39%。通过对比国内外材料测试技术与仪器的研究进展发现,现有的力学性能测试仪器多数需要对被测试对象进行取样,很少开展针对结构的力学性能测试。本文介绍了自主研发的多载荷多物理场耦合材料力学性能测试装置的功能、各个模块的布局方式、加载的主要指标和拉-扭复合加载实现方法,对测试装置的夹具进行改进,拓展了装置的测试范围,方便原位观测的实现。更换夹具后,对装配同轴度进行调整,同时验证了传感器的线性度和准确性。试验分析位移测量光栅尺的数值与试件实际变形的函数关系,修正装置测得的拉伸曲线。指出原位观测一端固定一端移动的拉伸测试需要装置观测平台具有自动跟随和观测距离补偿的功能,采用灰度梯度算法判断图像是否清晰并控制电机进行调整来实现这个功能。完成前述工作后,本文应用自主研发的多载荷多物理场耦合材料力学性能测试装置首先对激光选区烧结工艺制备的矩形截面试件和管状试件进行重复拉伸测试,统计测试后得出的弹性模量、抗拉强度和伸长率等参数结合断口形貌得出试验重复性较好,试件没有整层断裂,具有稳定的力学性能。然后对激光选区烧结工艺制备的环形点阵结构试件进行拉伸、扭转和预拉伸扭转加载测试。四边型点阵结构的等效弹性模量为40.736MPa,抵抗变形的能力优于其它三种结构,圆型点阵结构的抗拉强度为14.225MPa,为四种结构中最优。四边型点阵结构的平均切应变为1.66%,抵抗切应力变形的能力优于其它两种点阵结构。应用数字散斑分析四种结构扭转应变的大小并对应变分布进行对比。最后,对每种结构在不同预拉伸力作用下的扭转曲线进行对比,发现随着预拉力的增加,三种点阵结构的平均切应变具有减小的趋势,而原始管状结构的平均切应变先增加后减小的规律。更多还原

【Abstract】 With the continuous development of ships,high-speed railwa ys,large aircraft and satellites,the trend of large-scale and high-speed engineering equipment poses new requirements for the innovation of structures and materials.In the case of satisf ying the strength,reducing the qualit y is equivalent to reducing energy consumption and increasing production econom y.With the continuous development of pol ymerization and reinforcement technology of n ylon materials,the mechanical properties of nylon materials have been comparable to metal materials.In the environment of poor lubrication or eas y corrosion,it can replace metals to manufacture components with low service load,such as gears and bearings.The experimental research on the mechanical response of th e lattice structure made of nylon material can pla y a reference role in the optimization design and application of the lattice structure.In this paper,the research progress of the lattice structure ’s mechanical properties both here and abroad has been s y ntheticall y anal yz ed,and three kinds of circular lattice structure of cell element along the circular arra y have been proposed.The three kinds of cell elements are trigonometric,quadrangular and round.The tubular structure of the same sectional area ha s been compared,and the shape and size of the specimen were introduced.With the help of the finite element software ANSYS Workbench,the strain response of each structure under the stress and shear stress has been anal yzed,and the same sampling points w ere selected for comparison.Then the quadrangle lattice structure was taken as an example.The effect of cell dimension change on variable response of cell dimension can be obtained b y optimization of minimum strain as the optimization target.The sensiti vity of var ying parameters to variable response has been anal yz ed.Based on the principle of the fitting method used in the software,the relation between the relative densit y of the lattice structure and the response of the strain has been derived.After optimization,the tensil e strain of the model is reduced b y 3.59%,and the torsional strain is reduced by 1.39%.By comparing the research progress of material testing t echnology and instrument both here and abroad,it was found that most of the existing mechanical performance testing instrument needs to sample the tested objects,and few tests have been carried out for the mechanical properties of the structure.In this paper,it has been introduced that the functions,the la yout methods of each module,th e main indexes of loading and the realization method of tension torsion composite loading of the multi load and multi ph ysical field coupling material mechanics performance test device.The fixture of the test device has been improved,and the test range of the device has been expanded to facilitate the realization of the in-situ observation.After the fixture was replaced,the assembl y proper alignment has been adjusted,and the linearit y and accurac y of the sensor have been verified.The relationship betw een the numerical value of the grating ruler of the displacement measurement and the actual deformation of the specimen has been anal yz ed,and the tensile curve measured b y the device has been corrected.It was pointed out that the in-situ observation of t he tensile test mode with one side fixed and one side motion needs the function of automatic tracking and distance compensation,and the gra y gradient algorithm was used to judge whether the image is clear and control the motor to make adjustment.After th e completion of the previous work,independent research and development of multi load and multi physical field coupling material mechanical performance testing device has been used to test the repeated tensile test of the rectangular section specimens and t ubular specimen s made b y the material increasing method in this paper.The statistics of Young’s modulus,tensile strength and elongation can be found that the repeatabilit y of the test is good after the statistical test.The fracture morphology shows tha t the specimen has no whole fracture,so the specimen has stable mechanical properties.Then the tensile,torsion and pre tensile torsion loading tests of the annul ar lattice structure specimens made b y increasing material manufacturing technique have been carried out.The equivalent elastic modulus of the quadrilateral lattice structure is 40.736 MP a,and the abilit y to resist deformation is better than the other three structures.The tensile strength of the circular lattice structure is 14.225 MP a,which is the best in the four structures.The average shear strain of quadrilateral lattice structure is 1.66%,and the ability to resist shear stress and deformation is better than the other two lattice structures.The size of the torsional strain of four structu res has been anal yz ed and the corresponding variation distribution has been compared by three dimensional digital speckle.Finall y,the torsion curves of each structure under different pretension force have been compared.It is found that with the increase of pretension,the average shear strain of the three lattice structures has a tendenc y to decrease,while the average shear strain of the original tubular structure increases first and then decreases.更多还原