【作者】 邓志华；

【导师】 马云海；

【作者基本信息】 吉林大学 ， 农业机械化工程， 2011， 硕士

【摘要】 贝壳是常见的生物材料,具有复杂的微观结构和优良的力学性能。文蛤是常见的软体动物文蛤贝壳是一种天然生物材料,具有的分级结构和优异性能为高性能的复合材料和仿生材料的设计提供了新思路。研究生物原形的几何结构特征、材料的力学性能、材料的组成是研制仿生材料的基本前提。软体贝壳作为天然生物材料的一种,由于其优异的力学性能而受到材料设计和研究者的关注。本文以辽宁营口地区的文蛤为研究对象,用扫描电子显微镜和体式显微镜观察了其微观组织结构;采用精密切割机对文蛤贝壳进行分割,得出了不同部分的密度分布情况。用电子万能实验机对文蛤贝壳的力学性能进行了分析,并用ansys有限元分析软件对其结构所对应的优良力学性能进行模拟仿真。最后文蛤片结构和性能之间的关系进行了探讨。文蛤贝壳无机成分由方解石和文石两相所构成,表面的角质层是一层硬化蛋白,有机质成分复杂占总重量5%,主要由不可溶的多糖几丁质、富甘氨酸和丙氨酸的不可溶蛋白质、富天冬氨酸等酸性氨基酸的可溶性蛋白等三种生物大分子组成。对文蛤珍珠层和棱柱层进行浸润性测试,发现文蛤棱柱层表面、珍珠层表面均具有较强的亲水性,接触角大小与其表面微观结构有关,其中棱柱层表面微观结构润湿性能满足Wenzel模型。对不同含水量的贝壳进行压缩、剪切等力学性能实验的对比中,压缩实验中,垂直生长表面加载时最大应力从54.3Mpa-90.60Mpa,而且最大应力主要集中于55Mpa和80Mpa左右。沿着生长方向加载时,最大应力范围48.5Mpa—61Mpa之间,相对于垂直加载时稳定。棱柱层和珍珠层的压缩的最大强度明显高于整体压缩强度,分层压缩时的最大强度是整体压缩强度的2倍。当垂直于表面方向加载时表现出了陶瓷的特征。本研究采用精密划痕仪,对片状文石之间的临界载荷Lc₁文石层与棱柱层之间的临界载荷Lc₂,并比较了不同含水量下Lc₁、Lc₂的变化情况,讨论了临界载荷对材料的整体力学性能的影响;采用微观摩擦磨损实验机对文蛤贝壳的摩擦性能测量,实验表明文蛤贝壳在与不同粗糙程度的砂纸对磨时,实验因素对摩擦因数的影响大小依次为摩擦速度、对副种类、法向载荷。用1000目砂纸做摩擦速度和法向载荷的全面实验时发现,在载荷一定的条件下,摩擦因数随着滑动速度的增大迅速减小。随着滑动速度的增大,摩擦表面的温度升高,壳体材料软化,贝壳中的有机质将填充于表面微观结构之间,从而壳体材料变得相对平坦光滑,摩擦表面间微突体的啮合程度越来越小,微突体间的相互运动阻碍作用减弱,使微观切削抗力减小,在相同法向载荷条件下,宏观的摩擦阻力也就减小,从而使测量得到的摩擦因数降低。这种变化趋势同贝壳材料的结构有一定关系,贝壳最外层为角质层,由很硬的贝壳硬蛋白构成,中间层为棱柱层,由无机物和有机物交替排列组成。实验初期,角质层上凸起的生长线必然会阻碍摩擦的进行,摩擦力的增大导致测量的摩擦因数的增大。贝壳材料的主要磨损机理有疲劳磨损和粘着磨损两种。文蛤贝壳壳体与砂纸摩擦过程中以犁削为主,并出现犁沟和轻微的材料转移现象。对实验中采集和测量得到的数据进行处理,建立贝壳的层状结构以及棱柱层和珍珠层模型。采用ansys有限元分析软件,对文蛤贝壳在准静态加载和动态加载过程层状结构模型的应力分布情况位移情况。。更多还原

【Abstract】 Shell is a common biological materials with complex microstructure and excellent mechanical properties. Is a common mollusk clams clam shells is a natural biological materials with hierarchical structure and excellent performance for high-performance composite materials and biomimetic materials design provides a new idea. Study the biological characteristics of the prototype geometry, mechanical properties, material composition is the basic prerequisite for development of biomimetic materials. Software shell as a kind of natural biological materials, due to its excellent mechanical properties and material design, and researchers are concerned about.In this paper, Yingkou clams for the study area, with a scanning electron microscope and stereo microscope observation of its microstructure; using precision cutting machine segmentation of clam shells, obtained the density distribution of different parts. Electronic universal testing machine with a clam shell on the mechanical properties were analyzed, and used finite element analysis software ansys structure corresponding to its excellent mechanical properties of simulation. Last clams film the relationship between structure and properties were discussed.Clam shells and inorganic constituents of calcite and aragonite are two-phase composition, surface of the cuticle is a layer of hardened protein, organic matter complex composition of the total weight of 5%, mainly from the insoluble polysaccharide chitin, non-glycine and alanine-rich soluble proteins, and other acidic amino acids aspartic acid-rich soluble protein composed of three kinds of biological macromolecules. Of clams and prismatic layer of nacre invasive tests and found that clams prismatic layer surface, the surface nacre are strong hydrophilic, the contact angle on the size of its surface structure, surface structure in which prismatic layer wetting properties to meet the Wenzel model . Shells of different water content compression, shear and other mechanical properties of the comparison experiment, the compression experiments, the vertical growth from the surface of maximum stress loads 54.3Mpa-90.60Mpa, and the maximum stress mainly in 55Mpa and 80Mpa so. Along the growth direction of the load, the maximum stress range between 48.5Mpa-61Mpa, as opposed to vertical loading and stability. Prismatic layer and nacreous layer of the compression strength was significantly higher than the overall maximum compressive strength, maximum strength of layered compression of the overall compressive strength of 2 times. Direction perpendicular to the surface when the load curve showed the characteristics of ceramics. In this study, precision instrument scratches on the sheet between the critical load Lc1 aragonite aragonite prismatic layer between the layer and the critical load Lc2, and compare the different water content Lc1, Lc2 changes, discussed the critical load overall mechanical properties of materials influence.Micro-friction and wear test machine using clam shells on the friction performance measurement, results show that clam shells with different roughness of sandpaper on the ground, the experimental factors on the order of the friction factors for the friction velocity, and vice types, the normal load. 1000 grit sand paper to do with friction velocity and normal load of the full experiment found that under certain conditions in the load, the friction factor increases as the sliding velocity decreases rapidly. As the sliding speed increases, the friction surface temperature, the shell material softening, shell organic matter in surface structure will be filled in between the shell material to become relatively flat smooth, micro-friction and conflict between the body surface increasingly engaging small, micro sudden relative movement between the body hindered weakened, reduced resistance to micro-cutting, in the same normal load conditions, the macroscopic friction also decreases, so that the friction factors measured lower . This trend materials with the shell structure of a certain relationship between the outermost shells stratum corneum, the hard shell of a hard protein composition, the middle layer of prismatic layer, alternating the composition of inorganic and organic matter. Early experiments, the cuticle on the raised lines will necessarily impede the growth of the conduct of friction, friction causes the increase of the friction factors measured increases. The main wear mechanism of shell material fatigue wear and adhesive wear are the two. Clam shell case with sandpaper rubbing process to plow the main, and the emergence of a slight furrow and the material transfer phenomenon.The experiment data acquisition and processing measured, the establishment of the layered structure and the shell prismatic layer and nacreous layer model. Using finite element analysis software ansys, on clam shells in the quasi-static loading and dynamic loading process of the layered structure of the stress distribution model displacement.更多还原