承受扭矩和剪切时开口多孔金属的孔棱失效

以高孔率的三维网状多孔金属(即开口多孔金属)为研究对象,建立其简化结构失效模型。分析多孔构件在扭转和剪切载荷形式作用下由于孔棱发生拉断、剪切和屈曲而引起的失效模式,系统地研究上述两种承载条件下这类多孔体构件受到载荷作用而导致孔棱失效时名义载荷与孔率的数理关系。在此基础上,进一步研究此类材料在不同载荷作用下发生各种孔棱失效模式的载荷条件。结果表明,这些失效模式与多孔金属的材质指标、孔率及承受的载荷大小等因素均有关系,这种关系也可以进行相应的具体数理表征。     

泡沫金属在双向承载条件下的力学性能

根据各向同性三维网状泡沫金属的简化结构模型,建立该类材料的双向拉伸力学分析模型.利用该力学模型推出泡沫金属在双向拉伸破坏时两向名义应力与孔率3者的数学关系式,并在此基础上进一步得出该类材料在承受双向载荷时的安全判据.当双向承受的名义应力相等时,还可得到泡沫金属在双向等荷承载条件下的载荷强度与孔率的数学关系.这些关系式通过泡沫镍为例的有关实验数据证明是相当实用的.而由本理论体系可得出对多孔体双向承载条件的安全性判断,这似乎是Gibson和Ashby的有关模型理论所未触及或难以做到的.     

泡沫金属在单双向拉压载荷作用下的表征分析

探讨泡沫金属的单向压缩以及双向拉压行为,并研究了该材料单双向拉伸性能,进一步分析该材料在承受各种单双向拉压载荷时的不同响应方式.结果表明:在泡沫金属材料受到不同的单双向拉压载荷作用而产生破坏时,其承受的各向名义应力大小与多孔体的孔率都可表达为一个统一的数理关系;对于一个确定的多孔体材料,其单双向压缩负载能力要分别大于其单双向拉伸负载能力.     

粉末冶金技术制备金属多孔材料研究进展

金属多孔材料既有金属的性质,又因为孔的存在,而具有一系列功能特性,诸如密度低、比表面积大、机械强度高、通透性好等,是一种性能优异的多功能工程材料,因而在工程中得到广泛的应用.本文阐述了粉末冶金技术制备金属多孔材料的最新研究进展,主要分析了生物金属多孔材料、形状记忆合金多孔材料、多孔钨电极、多孔不锈钢和多孔铜的制备及研究进展.     

脱合金法制备纳米多孔金属的研究进展

纳米多孔金属具有独特的物理、化学、力学性能,具有极大的科学与工程应用潜力.脱合金法是制备此类材料的有效技术,是实现其应用的关键.本文概述了脱合金法制备纳米多孔金属的原理,并从脱合金法制备纳米多孔金属的材料体系、初始材料的制备工艺以及纳米多孔金属的性能三方面综述了脱合金法制备纳米多孔金属的研究进展.     

泡沫材料在剪切载荷作用下的力学关系推演和分析

泡沫金属是一种兼具功能和结构双重属性的优秀工程材料,在作为工程构件时就可能遇到剪切载荷的作用。探讨泡沫材料在剪切载荷作用下其构件内部的力学行为,采用隔离分析的简单方式,通过数理推演得出此种承载状态下的力学关系表征。结果显示,泡沫金属材料受到剪切载荷作用而产生破坏时,其构件内部的最大名义切应力大小可用多孔体的孔率以及泡沫金属材料本身固有的特性参量来描述。通过这种数理关系,直接便捷得到该材料在此时的强度判据。     

生物相容的多孔钛和多孔镁的加工

泡沫金属是一类新材料，具有极低的密度与优良的机械、热、声学性能的独特组合。它们在很宽的范围内有应用可能，如：震动、冲击的能量吸收；尘及流体的过滤器；机械噪声消音器；多孔电极；高温填料，灭火器、加热器、热交换器、催化剂载体，结构材料及最重要的生物相容性植入体。因为其具有开放多孔状结构，允许新骨细胞组织在内生长及体液的传统。尤其吸引人的是多孔材料的强度及杨氏模量可以通过对孔隙率的调整同自然骨相匹配。 理想的代骨材料应该是骨诱导的，以便于与原生骨尽快成为一整体，并具有较高的生物降解及生物吸收速率，以便…     

泡沫材料在多向拉伸载荷作用下的力学模型

以各向同性的三维网状高孔率泡沫金属为研究对象,根据其简化结构模型,推导得出该类材料在多向拉伸破坏时3个名义主应力与孔率四者之间的数理关系。通过推演得出的有关关系式,还可进一步得出泡沫金属在多向受力状态下使用时的强度设计判据。     

煤气化技术用金属多孔材料研究进展

发展洁净煤技术,减少污染物排放,提高煤炭利用效率是我国,也是世界的一项重要的战略任务,而金属多孔材料是洁净煤技术使用不可缺的关键材料.本文重点阐述洁净煤技术用金属多孔材料的国内外研究现状和一些新的发展趋势,在这基础上分析了金属多孔材料所面临的机遇和挑战.     

泡沫金属力学性能的若干问题

泡沫金属在结构方面的应用口益增多，其力学性能随之显得越来越重要。本文列举了该材料的一些结构用途，在强化其力学性能研究意识的同时，提出了泡沫金属双向拉伸性能研究的基础性和必要性。并从其应用发展趋势、制备方法和结构特点出发，指出该材料双向力学性能与孔率关系研究的重要意义。     

Theoretical prediction of effective elastic constants for new intermetallic compound porous material

Based on microstructure analysis of the new Ti-Al intermetallic compound porous material, a micromechanics model of heterogeneous Plateau porous structure was established and calculation formulas of elastic constants (including effective elastic modulus, effective shear elastic modulus and effective Poisson ratio) were derived by the energy method for this porous material. Calculation results show that both the effective elastic modulus and effective shear elastic modulus increase with the increase of the relative density while the effective Poisson ratio decreases. Compared with the currently-existing hexagonal honeycomb model and micromechanics model of composite materials, the micromechanics model of heterogeneous Plateau porous structure in this study is more suitable for characterizing the medium-density porous material and more accurate for predicting the effective elastic constants of the medium-density porous material. Moreover, the obtained explicit expressions of the effective elastic constants in term of the relative density rather than the microstructural parameters for the uniform and regular Plateau porous structure are more convenient to engineering application.     

多孔金属结合剂CBN砂轮孔隙结构对磨料层胎体力学性能的影响

为解决多孔金属结合剂CBN砂轮在高孔隙率下的强度下降问题,采用球形尿素颗粒为造孔剂,制作孔径、孔形和孔隙可控的多孔金属结合剂砂轮磨料层胎体,研究不同载荷情况下的孔隙率和孔隙排布等孔隙结构因素,对多孔金属结合剂磨料层胎体力学性能的影响规律。结果表明:孔隙有序排布时的胎体弹性模量要小于孔隙无序排布的;胎体材料的屈服强度随孔隙率增大而下降;在相同孔隙率下,孔隙有序排布的胎体,在纵向受压、孔隙正向排布的情况下屈服强度更高。      

Additive manufacturing technologies of porous metal implants

Biomedical metal materials with good corrosion resistance and mechanical properties are widely used in orthopedic surgery and dental implant materials,but they can easily cause stress shielding due to the significant difference in elastic modulus between the implant and human bones.The elastic modulus of porous metals is lower than that of dense metals.Therefore,it is possible to adjust the pore parameters to make the elastic modulus of porous metals match or be comparable with that of the bone tissue.At the same time,the open porous metals with pores connected to each other could provide the structural condition for bone ingrowth,which is helpful in strengthening the biological combination of bone tissue with the implants.Therefore,the preparation technologies of porous metal implants and related research have been drawing more and more attention due to the excellent features of porous metals.Selective laser melting（SLM）and electron beam melting technology（EBM）are important research fields of additive manufacturing.They have the advantages of directly forming arbitrarily complex shaped metal parts which are suitable for the preparation of porous metal implants with complex shape and fine structure.As new manufacturing technologies,the applications of SLM and EBM for porous metal implants have just begun.This paper aims to understand the technology status of SLM and EBM,the research progress of porous metal implants preparation by using SLM and EBM,and the biological compatibility of the materials,individual design and manufacturing requirements.The existing problems and future research directions for porous metal implants prepared by SLM and EBM methods are discussed in the last paragraph.     

凝胶注模工艺制备医用多孔Ti-Co合金的性能

采用凝胶注模工艺制备含8%和12%Co(质量分数,下同)的多孔Ti-Co合金,研究获得均匀悬浮稳定浆料的分散剂加入量。采用扫描电子显微镜、X射线衍射、压缩和三点弯曲试验分别对多孔Ti-Co合金的显微结构和力学性能进行了测试和分析。结果表明,加入1%分散剂可获得分散效果最佳的悬浮浆料,所制备多孔Ti-Co合金的孔隙率在50%左右,孔隙呈三维通孔结构。与多孔纯钛相比,添加Co元素明显提高了多孔Ti的力学性能,其中压缩强度在68～378MPa之间,抗弯曲强度在53.68～169.17MPa之间,弹性模量在7～21GPa之间。固相体积分数为33%,在1100℃下烧结的多孔Ti-8%Co合金由于与成人骨的力学相容性最好,适合作为医用植入材料。     

空心球造孔制备的多孔金属结合剂金刚石砂轮的磨削性能研究

本实验采用青铜结合剂为胎体,通过添加氧化铝空心球并采用热压烧结法,制备出多孔金属结合剂金刚石砂轮,并采用所制备的砂轮对工程陶瓷和铸铁材料进行磨削加工试验.实验结果表明:随着孔隙率的增加,含空心球的多孔金属结合剂金刚石砂轮的磨削阻力减小,砂轮的锋利性、磨削比和被加工工件的表面质量均得到提高;当孔隙率超过30%时,随着孔隙...     

Development in applications of porous metals

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Porous titanium implants fabricated by metal injection molding

Sodium chloride (NaCl) was added as a space holder in synthesis of porous titanium by using metal injection molding(MIM) method. The microstructure and mechanical properties of porous titanium were analyzed by mercury porosimeter, scanning electron microscope(SEM) and compression tester. The results show that the content of NaCl influences the porosity of porous titanium significantly. Porous titanium powders with porosity in the range of 42.4%–71.6% and pore size up to 300 μm were fabricated. The mechanical test shows that with increasing NaCl content, the compressive strength decreases from 316.6 to 17.5 MPa and the elastic modulus decreases from 3.03 to 0.28 GPa.     

Determination of Young's modulus and Poisson's ratio for coatings

Designing thin-film coatings to meet engineering needs requires the knowledge of accurate mechanical properties of the coatings. Young's modulus and Poisson's ratio are two basic mechanical properties of materials, which should be conveniently measured. This paper reports a direct and non-destructive method for the measurement of the Young's modulus and Poisson's ratio of a thin-film coating and its substrate based on the extended Hertz theory for the contact of coated bodies. The theory is used to analyze load-displacement data from a spherical indentation in the elastic range, in which the substrate effect is intrinsically modeled. The Young's modulus and Poisson's ratio are determined at the same time through minimizing the difference between the measured and specially defined modified Young's moduli. Two sets of validation experiments are also reported. This new method does not require any assumptions on pressure distribution and Poisson's ratio and can be easily incorporated into current indentation analysis systems.