功能梯度骨质生物材料的研究进展

功能梯度骨质生物材料为根据人体自然骨的特殊结构,结合金属材料和生物陶瓷材料各自的优点而制备的一类既具有仿生孔隙分布,又具有良好力学性能的骨质生物复合材料.简要介绍了功能梯度骨质生物材料的研究背景,评述了Ti基、316L不锈钢基、Co-Cr-Mo基、Ti4Al6V基四大类功能梯度骨质生物材料的研究进展.同时指出,相比其它制备方法,粉末冶金法由于其近净成形的特点在制备功能梯度骨质生物材料时具有更大的优势.     

从低维到高维的仿生材料制备及其应用进展

经过数十亿年的进化,自然界中的生物材料表现出许多卓越的性质和独特的功能。这些生物材料通常是由生物体内的有限组分在温和条件下组装而成,其优异的性能在很大程度上来源于复杂的多级结构,例如含邻苯二酚单元的贻贝粘附蛋白具有普适的强粘附力,珠-线结构的蜘蛛丝具有优异机械性能和集水能力,空心结构的北极熊毛发具有隔热保温作用,规则微纳结构的蝴蝶翅膀显示多彩的颜色,梯度多孔结构的柚子皮具有优异的阻尼减震效果等。以自然界的设计原理为灵感制造人工材料在材料科学和工程领域受到了极大关注,过去数10年,这方面的研究成果不胜枚举。总结了仿生材料在结构仿生方面的研究进展,选取了几个从低维到高维尺度上的典型例子概述了仿生材料的结构和功能之间的关系。     

生物功能材料的发展与应用

生物功能材料的发展可分为两个方面，即功能生物材料和仿生功能材料。功能生物材料的研究在于开发生物材料的物理、化学、生物特性的应用。本文着重叙述了生物组织电性能的研究及生物光电材料的应用；提出从生物活性材料活动规律研究入手，由生物模型简化为数学、物理模型从而设计出仿生功能材料的方法。举例说明了生物功能材料的发展对改变传统生产方式及对高科技产业的巨大影响，并对国民经济的发展有很大的促进作用。     

生物材料的仿生构思

过去30年里,生物材料的研究取得了显著成就,但从临床效果看,其与宿主相互作用亟待改善;哪怕是有些应用于长期埋植体内的替代物,常被机体视为异物,从而启迪人们不要仅着眼于从材料的物化性能方面构思生物材料。文章从蛋白质、糖类和脱氧核糖核酸与材料的关系出发,以细胞作为仿生生物材料的蓝本,从分子和细胞水平讨论了生物特异性材料设计,人工细胞外基质的仿生化途径以及通过材料对细胞编程凋亡的调控等方面的研究思路;试图从生命科学的广度和柔性出发,提出在不同层次和水平上进行仿生,从事生物材料设计,解决生物材料与生物体复杂接口问题,使生物材料向智能化和环境友好化发展。     

柔性工装的结构设计与应用研究

本文通过对柔性工装的结构设计与应用阐述,从概念、特点、作用、设计方法到实际应用入手,分析组合工装结构设计与拼装和工装结构模块化设计与制造的各自优势,以创新为主线,论述柔性工装的结构设计、制造、管理与快速换装的新思路、新方法。     

基于犰狳外壳仿生的SiC-超高分子量聚乙烯柔性防护板的试验测试和有限元模拟

个体防护装甲的发展对提高单兵作战能力具有重要意义,基于仿生研究可以为设计高性能装甲提供新的思路。犰狳外壳由六边形鳞片紧密拼接而成,采用分层结构设计,具有很好的柔性和防护能力。本文借鉴犰狳外壳的几何排列模式,采用SiC陶瓷片模仿硬质壳层,超高分子量聚乙烯(UHMWPE)热压板模仿软质壳层,按1∶1厚度比例设计制备仿生复合鳞片,将仿生鳞片紧密排列后封装制成一种新型柔性复合防弹插板。为了验证该种防弹插板的防弹性能并研究其破坏特征,进行弹道极限V0试验测试,结合有限元模拟分析其抗7.62 mm手枪弹侵彻的能力。结果表明:该柔性防弹插板不仅满足防弹性能要求,且具备较好的柔性,可为今后新型防弹插板的设计和优化提供参考。      

水下观测机器人推进器的动态结构仿生设计研究

目的 为了更好地实现水下机器人在海洋牧场观测环境中的低速稳定航行,设计一种水下观测机器人的仿生推进器。方法 结合结构仿生原理提出动态结构仿生设计方法,具体过程包括选择仿生对象、动态结构特征提取、生物特征与产品匹配、产品集成创新设计及设计评价。以水下观测机器人推进器为例,重点模仿蓝斑条尾魟胸鳍波动推进的形态与结构,分步骤完成仿生推进器造型和功能的动态结构仿生设计。结果 通过流体动力学仿真评估,得到波动鳍表面压力分布情况,结果表明波动鳍推进能够产生一定的推力,验证了动态结构仿生设计方法的可行性。结论 该仿生推进器具有低速稳定航行的特点,能够有效提升海洋牧场的观测能力,动态结构仿生设计方法对仿生推进器的结构设计具有借鉴意义。     

基于荷特征的概念车仿生设计研究

目的荷在开花与结果的生长过程中,呈现出不同的特征,挖掘各个生长阶段的特征,使其应用在概念车创新性设计中,为概念车仿生设计开辟新思维。方法利用仿生设计原理,从形态仿生、功能仿生、结构仿生、色彩仿生四方面,对荷与荷之关联的荷花、荷叶、藕进行形态、功能、结构、色彩的特征分析,让荷花、荷叶、藕的特征与概念车各部位的设计进行对比、分析与糅合。结论对荷的仿生特征进行分析,让其合理运用于概念车的形态、功能、结构、色彩创新设计中,提出了以荷特征为基础的概念车仿生设计方法,为创造出更具有自然特征的概念车提供了途径,为完善概念车仿生设计方法提供了思路。     

生物复合材料的特征及仿生的探讨

竹、木材、骨和贝壳等生物材料都是复合材料,在长期自然进化中具有优良的结构和特性,问题是人们如何在复合材料的设计和加工中吸取这些特性。本文概述了复合材料仿生的基本情况,研究了生物材料复合结构的优良特征、功能适应性原理以及树木和骨骼的创伤愈合,并对复合材料的结构仿生和自愈合作了初步的探讨。     

生物材料的离子束表面改性

随着表面处理技术的发展,国内我对如何改善现有的生物材料表面的各种性能,如耐蚀性,耐磨性,生物相容性等进行了研究。各种表面处理的方法受到高度重视,其中离子束表面改性技术,由于其对材料本体无负效应,已被证明是最为成功的一种。本文在综述离子束改性技术在生物材料及器械方面应用的同时,提出将梯度功能材料的新概念与离子束改性技术相结合,用以制备表面性能优异的仿生生物材料。     

Functional gradients and heterogeneities in biological materials: Design principles,functions, and bioinspired applications

Living organisms have ingeniously evolved functional gradients and heterogeneities to create high-performance biological materials from a fairly limited choice of elements and compounds during long-term evolution and selection. The translation of such design motifs into synthetic materials offers a spectrum of feasible pathways towards unprecedented properties and functionalities that are favorable for practical uses in a variety of engineering and medical fields. Here, we review the basic design forms and principles of naturally-occurring gradients in biological materials and discuss the functions and benefits that they confer to organisms. These gradients are fundamentally associated with the variations in local chemical compositions/constituents and structural characteristics involved in the arrangement, distribution, dimensions and orientations of the building units. The associated interfaces in biological materials invariably demonstrate localized gradients and a variety of gradients are generally integrated over multiple length-scales within the same material. The bioinspired design and applications of synthetic functionally graded materials that mimic their natural paradigms are revisited and the emerging processing techniques needed to replicate the biological gradients are described. It is expected that in the future bioinspired gradients and heterogeneities will play an increasingly important role in the development of high-performance materials for more challenging applications.     

Design of functionally graded dental multilayers

This paper presents the results of a computational and experimental effort to develop crack‐resistant dental multilayers that are inspired by the functionally graded dento‐enamel‐junction (DEJ) structure that occurs between dentin and enamel in natural teeth. The complex structures of natural teeth and ceramic crowns are idealized using flat‐layered configurations. The potential effects of teeth‐on‐teeth contact are then modelled using finite element simulations of Hertzian contact. The resulting stress distributions are compared for a range of possible bioinspired, functionally graded architecture. The computed stress distributions show that the highest stress concentrations in the top ceramic layer of crown structures are reduced significantly by the use of bioinspired functionally graded architectures. The reduced stresses are experimentally shown to be associated with significant improvements (～32%) in the pop‐in loads. The implications of the results are discussed for the design of bioinspired dental ceramic crown structures. The bioinspired functionally graded layers are also shown to promote improvements in the critical crack size.     

压电元件驱动的功能梯度弹性薄板的屈曲

考虑功能梯度薄板,其上下表面嵌有压电执行元件.根据逆压电效应将电压转换成作用于板上的等效电载荷.假设梯度材料的弹性参数为板厚度方向坐标的幂函数,基于经典板理论,导出了功能梯度弹性薄板小挠度屈曲平衡微分方程.利用双三角级数展开法,得到了四边简支具有压电元件的功能梯度矩形板的临界屈曲载荷,在此基础上通过数值例子讨论了弹性板的几何尺寸、材料梯度指数的变化对临界电压(载荷)的影响.研究结果表明,材料的梯度指数对临界电压有重要影响,并且通过调整作用于执行元件上的电压的大小和方向,可实现对结构稳定性的有效控制.     

Asymmetric flexural vibration and thermoelastic stability of FGM circular plates using finite element method

Here, asymmetric free vibration characteristics and thermoelastic stability of functionally graded circular plates are investigated using finite element procedure. A three-noded shear flexible plate element based on the field-consistency principle is used. Temperature field is assumed to be a uniform distribution over the plate surface and varied in thickness direction only. Material properties are graded in the thickness direction according to simple power law distribution. For the numerical illustrations, aluminum/alumina is considered as functionally graded material. The variation in critical buckling load is highlighted considering gradient index, temperature, radius-to-thickness ratios, circumferential wave number and boundary condition of the plate.     

Structural Design Elements in Biological Materials: Application to Bioinspiration

Eight structural elements in biological materials are identified as the most common amongst a variety of animal taxa. These are proposed as a new paradigm in the field of biological materials science as they can serve as a toolbox for rationalizing the complex mechanical behavior of structural biological materials and for systematizing the development of bioinspired designs for structural applications. They are employed to improve the mechanical properties, namely strength, wear resistance, stiffness, flexibility, fracture toughness, and energy absorption of different biological materials for a variety of functions (e.g., body support, joint movement, impact protection, weight reduction). The structural elements identified are: fibrous, helical, gradient, layered, tubular, cellular, suture, and overlapping. For each of the structural design elements, critical design parameters are presented along with constitutive equations with a focus on mechanical properties. Additionally, example organisms from varying biological classes are presented for each case to display the wide variety of environments where each of these elements is present. Examples of current bioinspired materials are also introduced for each element.     

磁电弹功能梯度材料板中的波动特性

假设材料常数和电、 磁常数沿板厚方向呈梯度变化, 将电磁功能梯度材料板沿厚度方向划分为层单元, 建立单元的控制方程, 然后根据单元之间的连续条件将单元控制方程装配成系统的控制方程, 求解控制方程, 得到不同模态波的弥散曲线, 分析了电磁参数对波的弥散特性的影响, 同时研究了材料梯度对弹性位移、 静电势和静磁势分布的影响, 并对磁电功能梯度材料中波的六个特征波面进行了分析。计算结果表明材料梯度引起弹性位移、 静电势、 静磁势的分布集中于材料参数梯度减少的方向, 材料为正交各向异性弹性材料。      

整合结构的仿生设计

自从1981年Cyril Stanley Smith基于系统方法学提出材料的功能、性能、结构与制造整合链模型以来，面向机器和临床实践的仿生设计得到广泛研究．整合结构的概念来源于生物科学，它表示将不同的结构组合在一起而成为一种新型的结构．典型的整合结构有梯度结构、多孔结构、分形结构与复合结构等．由于自然材料结构的几十亿年的进化，病毒、细菌、植物与动物组织的自然结构与人造机械结构相比，具有明显的优越性．     

Bioinspired design of dental multilayers

This paper considers the use of bioinspired functionally graded structures in the design of dental multi-layers that are more resistant to sub-surface crack nucleation. Unlike existing dental crown restorations that give rise to high stress concentration, the functionally graded layers (between crown materials and the joins that attach them to dentin) are shown to promote significant reductions in stress and improvements in the critical crack size. Special inspiration is drawn from the low stress concentrations associated with the graded distributions in the dentin-enamel-junction (DEJ). The implications of such functionally graded structures are also discussed for the design of dental restorations.     

具有压电元件的功能梯度弹性薄板的振动特性

考虑一功能梯度薄板,其上下表面嵌有压电执行元件。根据逆压电效应,将电场强度转换成作用于板上的等效电载荷。假设梯度材料的物性参数为板厚度方向坐标的幂函数,应用达朗贝尔原理,导出了具有压电元件的功能梯度弹性薄板的动力学方程。采用变量分离与Navier解,得到四边简支功能梯度板的固有特性与电场强度间的关系。并进一步通过数值例子讨论了电场强度、材料的梯度指数等对板固有特性的影响。研究结果表明,调整作用于执行元件上的电场强度可以实现对板的振动特性的控制,而材料的梯度化可影响板的固有频率,在设计中应予以考虑。     

Longitudinal vibration analysis of strain gradient bars made of functionally graded materials (FGM)

Longitudinal free vibration analysis of axially functionally graded microbars is investigated on the basis of strain gradient elasticity theory. Functionally graded materials can be defined as nonhomogeneous composites which are obtained by combining of two different materials in order to obtain a new desired material. In this study, material properties of microbars are assumed to be smoothly varied along the axial direction. Rayleigh–Ritz solution technique is utilized to obtain an approximate solution to the free longitudinal vibration problem of strain gradient microbars for clamped–clamped and clamped-free boundary conditions. A parametric study is carried out to show the influences of additional material length scale parameters, material ratio, slenderness ratio and ratio of Young’s modulus on natural frequencies of axially functionally graded microbars.