含磨粒润滑条件下3Cr13涂层加速磨损机理研究

提出3Cr13涂层加速磨损失效新的实验方法.采用该方法在MM200摩擦磨损试验机上,对高速电弧喷涂3Cr13涂层在含SiO_2磨粒的润滑条件下磨损失效开展了加速磨损试验,通过对比分析扫描电镜照片筛选合适的磨粒颗粒,并分析SiO_2磨粒加速涂层磨损可能的机理.结果表明:适合3Cr13涂层的加速磨损试验的磨粒粒度为微米级,通过磨损表面照片得出了磨粒在润滑条件下对涂层加速磨损作用主要表现为:微观切削、挤压和磨粒的聚集.     

Chitosan-nanodiamond composites for improving heart valve biological prostheses materials: preparation and mechanical trial

Abstract

Nanodiamond-chitosan composites of definite composition were prepared to modify heart valve biological prostheses materials. The final material is characterized by higher failure stress and Young modules. Moreover, primary modification of nanodiamonds with chitosan provides an additional strength to collagen-based final material.     

Novel transcatheter aortic heart valves exhibiting excellent hemodynamic performance and low-fouling property

Transcatheter aortic heart valves (TAHVs) have been widely used for aortic valve replacements, with less trauma and lower clinical risk compared with traditional surgical heart valve replacements. In the present study, composites of poly(ethylene glycol) diacrylate (PEGDA) hydrogels and anisotropic high-shrinkage polyethylene terephthalate/polyamide6 (PET-PA6) fabric (PEGDA/PET-PA6) were fabricated as artificial heart valve leaflets. Dynamic mechanical analyses (DMA) indicated that PEGDA/PET-PA6 composites possessed anisotropic mechanical properties (i.e., storage moduli ～23.30 ± 1.36 MPa parallel to the aligned fabric fibers and ～9.68 ± 0.90 MPa perpendicular to the aligned fibers at 1 Hz) that were comparable to aortic valve leaflets. The PEGDA/PET-PA6 composites with smooth surfaces were highly hydrophilic (contact angle ～41.6° ± 3.8°) and had low-fouling properties without platelet adhesion, suggesting a low risk of thrombogenicity when they interacted with blood. Furthermore, transcatheter aortic heart valves were fabricated using nitinol self-expanding frames and PEGDA/PET-PA6 composites as artificial leaflets, which presented excellent hemodynamic performance with a large orifice area (1.75 cm²) and low regurgitation (3.41%), thus meeting the requirements of ISO 5840-3 standard. Therefore, PEGDA/PET-PA6 composites had suitable mechanical properties, good biocompatibility, and low-fouling properties, indicating that they might be used for TAHVs in the future.     

耐磨料磨损材料数据库的设计与实现

介绍了材料数据库的基本特点及设计的一般过程与思路,并以此为依据,从系统的用户需求分析着手,预定了数据库的功能,然后进行了概念结构、逻辑结构、物理结构的设计,开发了耐磨料磨损材料数据库.进一步地,总结了该数据库的特点,展示了该数据库的开发实现界面,为本领域材料数据库的相继开发与建立提供极具价值的参考.     

In vitro hemocompatibility testing of new materials for mechanical heart valves

Biomaterials with improved wear properties, high resistance towards breaking, and better availability in comparison to the conventional material (PyroCarbon) may result in heart valve prostheses with prolonged lifetime and improved quality of life (no required lifetime anticoagulation). TiN-coatings as well as ceramic materials such as ZrO₂, and alternative carbon surfaces are considered as potential new materials. In order to determine hemocompatibility properties of these materials, a new test set-up without blood-air-contact has been built and successfully tested according to ISO 10993-4 : 1993 (EN 30993) within a first study for a series of materials.     

Engineering materials for artificial cells

The grand challenge of engineering a minimal artificial cell provides a controllable framework for studying the biochemical principles of life. Artificial cells contribute to an increased understanding of complex synthetic systems with life-like properties and provide opportunities to create autonomous cell-like materials. Recent efforts to develop life-like artificial cells by bottom-up approaches involve mimicking the behavior of lipid membranes to recapitulate fundamental cellular processes. This review describes the recent progress in engineering biomimetic artificial minimal cells and recently developed chemical strategies to drive de novo membrane formation from simple synthetic precursors. In the end, we briefly point out the challenges and possible future directions in the development of artificial cells.     

Cu对粉末冶金Fe3Al基复合材料性能的影响

研究了Cu含量对粉末冶金Fe3Al基复合材料的烧结性能和力学性能的影响,分析了施加载荷和改变转速对加入不同量铜粉末冶金Fe3Al基复合材料的摩擦磨损性能的影响,并借助电子显微镜和能谱分析了不同铜含量Fe3Al基复合材料的磨损机理.结果表明:加入12%的Gu可使Fe3Al基复合材料具有良好的烧结性能和力学性能;载荷和转速对复合材料的磨损形式受铜的加入量的影响;铜的加入影响复合材料的磨损形式和磨损机理,当含铜量较少时,复合材料以磨粒磨损为主,随加入铜的量的增多,其磨损形式变为磨粒磨损和轻微的粘着磨损形式,加入大量铜时,则以粘着磨损为主.     

人工心瓣热解炭涂层的密度和孔隙结构研究

研究了人工心瓣热解炭涂层的密度和孔隙结构。采用准稳态流化床化学气相沉积工艺制备出人工心瓣用高密度各向同性热解炭涂层,利用密度计、扫描电镜、透射电镜、压汞仪等分析了热解炭涂层的密度和孔隙结构。结果表明:高密度各向同性热解炭的孔隙主要是由类球形生长特性间0.83μm左右的较大孔隙和62nm左右的中等孔隙以及类球形生长特性内缠结体结构所形成的微孔隙构成,缠结体之间形成的微孔隙能够导致热解炭密度的降低,热解炭类球形颗粒的多少也会对高密度各向同性热解炭的密度造成影响。     

发动机气门失效分析

某发动机气门发生断裂失效,通过对失效气门杆端面和与其接触的摇臂进行宏观分析、扫描电镜分析、能谱分析、金相检验及硬度测试,找出了发动机气门失效的原因。结果表明:由于摇臂油孔存在制造偏差,导致气门杆端面与摇臂摩擦副之间润滑不良,从而造成该摩擦副之间发生了严重的磨粒磨损,使得气门杆端面与摇臂之间的间隙增大,过大的气门间隙又会导致气门锥面的落座力增大,造成气门颈部应力集中,并且萌生裂纹,裂纹不断扩展,最终造成气门断裂失效。     

玻璃纤维芯材真空绝热板使用寿命预测

从真空绝热板（VIP）的绝热机制出发,建立了VIP的使用寿命评估模型,利用该模型对玻璃纤维芯材VIP的使用寿命进行预测。基于Arrhenius定律,建立了VIP的加速寿命模型,通过试验确定加速寿命模型中的参数及VIP的激活能,利用该模型可以预测VIP在不同温度下的使用寿命。通过试验样品的长期跟踪数据来验证两种寿命模型的可靠性。探讨了提高VIP绝热性能及延长使用寿命的方法。本研究工作对VIP关键技术突破及工艺参数优化提供了一定的理论依据和技术支持。     

特大型空分设备配套阀门的研制

介绍特大型空分设备配套的三偏心蝶阀的研制内容、使用场合,以及特大型空分设备高压氧气输送管网中高压氧用截止阀、特种安全阀的开发内容和结构特点。     

A theory of pad conditioning for chemical-mechanical polishing

Statistical models are presented to describe the evolution of the surface roughness of polishing pads during the pad-conditioning process in chemical-mechanical polishing. The models describe the evolution of the surface-height probability-density function of solid pads during fixed height or fixed cut-rate conditioning. An integral equation is derived for the effect of conditioning on a foamed pad in terms of a model for a solid pad. The models that combine wear and conditioning are then discussed for both solid and foamed pads. Models include the dependence of the surface roughness on the shape and density of the cutting tips used in the conditioner and on other operating parameters. Good agreement is found between the model, Monte Carlo simulations and with experimental data.     

聚氯乙烯薄膜使用寿命预测

文中对聚氯乙烯(PVC)薄膜在实际应用环境中的使用寿命进行了快速可靠的预测。通过加速寿命试验,以断裂伸长率下降至其初始值的50%为失效指标,对PVC薄膜在户外环境因子(紫外光和热)协同作用下的老化动力学进行了研究,利用威布尔统计方程分析老化失效数据,并使用Temperature-non-thermal模型建立外推关系式,确立了PVC薄膜的寿命-环境因子统计学关系式,模拟了PVC薄膜寿命分布在环境因子(热和强紫外光)协同作用下的变化规律。最后,应用上述寿命-环境因子关系式,对PVC薄膜在上海地区的户外使用寿命进行了预测,得出150μm厚的PVC薄膜曝露于上海地区时,户外使用寿命为13个月。     

A literature review on planning and analysis of accelerated testing for reliability assessment

Accelerated testing has been widely used for several decades. Started with accelerated life tests with constant‐stress loadings, more interest has been focused prominently on accelerated degradation tests and time‐varying stress loadings. Because accelerated testing is crucial to the assessment of product reliability and the design of warranty policy, it is important to develop an efficacious test plan that encompasses and addresses important issues, such as design of stress profiles, sample allocation, test duration, measurement frequency, and budget constraint. In recent years, extensive research has been conducted on the optimal design of accelerated testing plans, and the consideration of multiple stresses with interactions has become a big challenge in such experimental designs. The purpose of this study is to provide a comprehensive review of important methods for statistical inference and optimal design of accelerated testing plans by compiling the existing body of knowledge in the area of accelerated testing. In this work, different types of test planning strategies are categorized, and their drawbacks and the research trends are provided to assist researchers and practitioners in conducting new research in this area.     

Accelerated LCF‐creep experimental methodology for durability life evaluation of turbine blade

This paper proposes an accelerated low cycle fatigue (LCF)‐creep experimental methodology in laboratory to investigate the durability life of turbine blades. A typical mission profile of the turbine blade was obtained by means of rain flow counting method, considering both the actual flight condition and ground test data. Finite element analysis (FEA) was conducted to obtain the stress and temperature fields of turbine blade. A test system was constructed to conduct LCF‐creep experiments of turbine blades, simulating the stress and temperature distributions of critical section properly. LCF‐creep experiments of full‐scale turbine blades were performed under a trapezoidal loading spectrum. Experiment results showed that the durability life of turbine blade based on numerical method was longer than that based on this experimental methodology, even an order of magnitude. Furthermore, this experimental methodology helped to extend the service life of this blade safely, and its validity was verified in actual service condition.     

浅析检测设备全生命周期管理的重要性

设备全生命周期管理是指以设备为对象,通过现代化的知识、理论和方法,建立健全制度,从设备管理和资产管理双向角度出发,贯穿设备生命周期中的各个环节,对设备的物质和价值运行轨迹进行全过程的科学有效管理,目的在于提高设备的可靠性和稳定性,追求更高的设备综合效率。     

Mechanical fatigue of an electronic component under random vibration

Electronic equipment, which is widely used in military applications, must be able to survive harsh environments. The endurance of such equipment is defined by the durability of their internal sensitive components. In this study, vibration induced fatigue life analysis of an axial leaded aluminium capacitor is performed. Three point bending tests are performed for the composite FR‐4 printed circuit boards (PCBs) material in order to determine bending modulus. Experimental modal analysis is used to validate a simulation model of the PCB. Step stress tests (SSTs) of reinforced and unreinforced capacitors which are mounted on the test PCBs are performed. It is found that the failure locations on the test PCBs are compatible among themselves and all the failures are due to flexure stress developed at the lead wires and solder joints. Numerical fatigue analyses are performed to define failure in terms of damage index. In addition, the Weibull model is used to define mean time to failure (MTTF) values. The comparison between MTTF values shows that the fatigue lives are strongly increased by the eccobond reinforcement. The last stage in this work is to focus on the influence of some design parameters on the fatigue life. An exponential equation is proposed to find the relation between lead‐wire diameter and the fatigue damage. It is shown that fatigue damage becomes a maximum for a square shaped PCB and it appears that component body diameter is more effective than the body length in increasing fatigue life.     

Bayesian Analysis of Step‐Stress Accelerated Life Test with Exponential Distribution

In this article, we propose a general Bayesian inference approach to the step‐stress accelerated life test with type II censoring. We assume that the failure times at each stress level are exponentially distributed and the test units are tested in an increasing order of stress levels. We formulate the prior distribution of the parameters of life‐stress function and integrate the engineering knowledge of product failure rate and acceleration factor into the prior. The posterior distribution and the point estimates for the parameters of interest are provided. Through the Markov chain Monte Carlo technique, we demonstrate a nonconjugate prior case using an industrial example. It is shown that with the Bayesian approach, the statistical precision of parameter estimation is improved and, consequently, the required number of failures could be reduced. Copyright © 2011 John Wiley & Sons, Ltd.     

聚醚醚酮及其改性的人工关节材料的摩擦磨损性能研究进展

聚醚醚酮(Polyetheretherketone,PEEK)优异的耐磨损性能为研发新一代高寿命人工关节提供了新希望。分别综述了采用常规摩擦学方法对纯PEEK、碳纤维增强PEEK、颗粒填充PEEK、等离子改性PEEK等作为人工关节材料,和采用模拟试验机方法对PEEK在人工髋关节、人工膝关节等假体关节面发挥耐磨损性能的应用和研究进展,最后展望了PEEK及其改性的人工关节材料摩擦磨损性能研究的发展趋势。     

电阻法测试钢动载磨料磨损参数的研究

电阻法测试钢动载磨料损参数的结果表明,电阻参数的变化规律反映了钢动载磨料磨损的特性。