钛合金表面双层辉光离子无氢渗碳层摩擦磨损性能研究

利用双层辉光放电离子渗碳原理,以格栅状高纯度固体石墨作为源极,钛合金作为阴极,氩气作为工作气体,依靠辉光放电和空心阴极效应在钛合金(Ti6Al4V)材料表面制备了具有特殊物理、化学性能的渗碳层;采用X射线衍射和辉光放电光谱分析了渗碳层的相组成及C元素分布;并考察了渗层的摩擦磨损性能.结果表明:复合渗碳层中形成了高硬相TiC及游离态C减摩相;渗层内C元素的含量呈梯度分布;经复合渗碳处理后材料的表面硬度大幅度提高,由表及里硬度成梯度降低;经渗碳处理后材料的减摩和抗磨性能显著改善,摩擦系数降低50%以上,比磨损率降低3个以上数量级.     

Ti6Al4V表面双层辉光离子渗Mo及其摩擦学性能的研究

利用双层解光离子渗金属技术在Ti6A14V合金表面渗Mo，用球—盘磨损试验机对试样的摩擦性能进行了研究．结果表明：Ti6A14V合金表面渗Mo可以形成均匀的表面改性合金层，合金层由沉积层和扩散层构成；合金层的硬度和弹性模量分别为10．86GPa和278．84GPa，较Ti6A14V有较大提高；渗Mo后的试样在干摩擦小滑动距离下表现出一定的减摩作用，耐磨性明显增强；在油润滑条件下，渗Mo改性层具有优异的减摩和耐磨性能．     

Ti6Al4V表面激光改性层重熔处理的微观组织特征及宽温域摩擦学性能研究

采用激光复合工程技术对Ti6Al4V基体表面进行强化耐磨处理,首先在Ti6Al4V合金表面进行激光氮化[Ti(N)]和氮氧化[Ti(N,O)]处理,然后在纯氩气气氛中分别对Ti(N)层和Ti(N,O)层进行激光重熔处理,制备了组织分布更为均匀的重熔氮化层[Re-Ti(N)]和重熔氮氧化层[Re-Ti(N,O)]. 组织结构分析揭示了Re-Ti(N)层主要由富氮αˊ-Ti和TiN_x组成,而Re-Ti(N,O)层则主要由富氧αˊ-Ti和TiN_xO_y组成. 相对于Ti6Al4V基体,Re-Ti(N)层和Re-Ti(N,O)层的硬度、弹性模量和磨损量降低了2倍以上,然而激光复合处理前后材料均表现出较大的摩擦系数. 相对于Re-Ti(N)层,氧原子的加入,不仅能够有效细化组织和提升强韧度,而且显著抑制了摩擦界面的黏着磨损. 通过磨屑结构分析进一步验证了基体黏着磨损机制和重熔改性层磨粒磨损机制.      

钛合金表面Ti-Al合金扩散层的摩擦性能研究

利用双层辉光离子渗金属技术,以纯铝作为源极,氩气为工作气体,利用不等电位空心阴极效应在钛合金(Ti6Al4V)表面渗铝,形成均匀致密的钛铝合金扩散层,采用WTM-1型球-盘摩擦磨损试验机对钛合金表面钛铝合金扩散层的摩擦性能进行研究,用显微硬度仪测量渗层的显微硬度,并用扫描电子显微镜和X射线衍射仪观察分析钛铝合金扩散层的截面形貌和相结构.结果表明:在Ti6Al4V合金基材表面形成厚20 μm的钛铝合金扩散层,其表面显微硬度达810HV;钛铝合金扩散层主要由金属间化合物Ti3Al和TiAl组成;钛铝合金扩散层可以显著提高钛合金表面的摩擦性能,摩擦系数从0.35左右降至0.15,抗磨损性能大幅提高.     

钛合金表面类金刚石碳梯度薄膜的摩擦磨损性能研究

与Ti6Al4V合金／超高分子量聚乙烯摩擦副对比,考察了Ti6Al4V合金表面类金刚石碳梯度薄膜／超高分子量聚乙烯摩擦副在干摩擦以及Hank’s溶液和生理盐水润滑下的摩擦磨损性能,采用扫描电子显微镜观察试样磨损表面形貌,并进而分析磨损机理。结果表明,类金刚石碳梯度薄膜具有良好的减摩抗磨性能,其体积磨损率约为相同条件下Ti6Al4V合金体积磨损率的50％,相应的超高分子量聚乙烯偶件的磨损率亦较低,类金刚石碳梯度薄膜的磨损呈现轻微磨粒磨损特征,而超高分子量聚乙烯可抑制类金刚石碳梯度薄膜的磨粒磨损。     

摩擦热对Ti6Al4V合金摩擦磨损性能的影响

在高速销-盘式摩擦磨损试验机上考察了Ti6Al4V销与GCr15钢盘摩擦副的干滑动摩擦磨损行为,并在线测量了销试样的摩擦接触温度,利用扫描电子显微镜、X射线衍射仪及透射电子显微镜分别对Ti6Al4V摩擦表面和次表层的微观形貌、组织成分、相结构进行研究.结果表明:Ti6Al4V的β相变点温度接近其摩擦系数和磨损率的转折温度;随着摩擦表面温度升高,在Ti6Al4V表面依次形成TiO、TiO2和V2O3;温度骤变促使Ti6Al4V表层析出纳米颗粒,高的摩擦温度使空气中的氮渗入表层而形成VN.上述结果共同对Ti6Al4V/GCr15摩擦副的摩擦磨损行为产生影响.     

摩擦-电化学噪声法研究Mo改性钛合金的腐蚀-磨损行为

利用等离子表面改性技术在Ti6Al4V合金基体上制备Mo渗镀复合改性层,考察改性层组织结构,利用微动摩擦学试验机并结合电化学噪声技术对比研究基材及改性层在0.5 mol/L NaCl溶液中的腐蚀-微动摩擦学行为,对腐蚀-摩擦过程中的噪声参数进行分析.结果表明:纯Mo改性层能够明显改善钛合金的耐磨和减摩特性;同时提高了合金在0.5 mol/L NaCl溶液中的自腐蚀电位及降低了腐蚀电流,改善了合金表面的腐蚀-摩擦学性能.     

磁过滤多弧离子镀C/C多层膜在模拟体液中的微磨粒磨损行为

采用磁过滤直流阴极真空弧源沉积技术在Ti6Al4V表面制备C/C多层DLC膜,利用纳米压痕划痕仪测试薄膜的纳米硬度和膜-基结合强度,采用微磨粒磨损试验机对C/C多层DLC膜在模拟体液环境中的磨损性能进行评价,并与Ti6Al4V的耐磨性能进行对比.结果表明:C/C多层DLC膜硬度达54.82 GPa,弹性模量和划痕临界载荷分别为342.27 GPa和0.52 N;在模拟体液环境中DLC膜的耐磨性能显著优于Ti6Al4V合金,DLC膜的磨损机制主要包括二体磨损及混合磨损;随着料浆浓度的增加,DLC膜的磨损机制从二体磨损向混合磨损过渡.     

纯钛与Ti6Al7Nb合金氮离子注入层在小牛血清溶液中的扭动微动磨损试验研究

文中主要研究了纯钛、Ti6A17Nb基体以及经过氮离子注入后的改性层的扭动微动磨损行为.氮离子注入采用高能离子注入机及增强沉积系统,加速电压为50 kV,注入剂量分别为1×l017、5×1017和9×1017cm-2.采用球/平面接触模式,对纯钛和Ti6Al7Nb合金/(Zr2O球(直径为25.2 mm),接触副在小牛血清介质条件下进行了纯钛和Ti6Al7Nb合金及其改性层的了扭动微动磨损试验.借助X衍射仪(XRD)、拉曼光谱(Raman)、三维形貌仪(3D)和扫描电镜(SEM)分析了两种材料及其改性层的化学成分、微动磨损磨痕形貌和微观组织结构,探讨了纯钛和Ti6Al7Nb合金基材和改性层的扭动微动运行行为和损伤机制.研究结果表明:用氮离子注入方法处理钛及其合金,生成的氮化物层能够改善材料表面的综合性能,提高其扭动微动磨损的耐磨性.纯钛和Ti6Al7Nb基体的磨损现象为氧化和剥落,其离子注入层的磨损现象为犁沟.     

在氮气介质中WC-Co/Ti6Al4V摩擦副的摩擦磨损性能研究

在THT07-135型高温摩擦磨损试验机上采用销-盘式接触形式,研究了WC-Co硬质合金/Ti6Al4V钛合金摩擦副在氮气介质中的摩擦磨损性能,并与空气介质中的摩擦磨损性能进行对比.结果表明:与空气介质相比,在氮气介质中WC-Co/Ti6Al4V摩擦副的摩擦系数稍低;WC-Co硬质合金比Ti6Al4V钛合金的磨损量低得多,氮气介质具有一定的减磨作用;钛合金材料的主要磨损机理为摩擦副之间产生较强的犁沟与挤压撕裂,而硬质合金的主要磨损机理为磨粒磨损与粘结剥落.     

The 7th International Conference on Fluid Mechanics May 24-27,2015,Qingdao,China

正http://www.icfm7.org First Announcement and Call for PapersThe objective of International Conference on Fluid Mechanics(ICFM)is to provide a forum for researchers to exchange new ideas and recent advances in the fields of theoretical,experimental,computational Fluid Mechanics as well as interdisciplinary subjects.It was successfully convened by the Chinese Society of Theoretical and Applied Mechanics(CSTAM)in Beijing(1987,     

INFORMATION FOR CONTRIBUTORS

Contributions： The Journal, Acta Mechanica Solida Sinica, is pleased to receive papers from engineers and scientists working in various aspects of solid mechanics. All contributions are subject to critical review prior to acceptance and publication.     

Preface

This special issue of PARTICUOLOGY is devoted to the first UK-China Particle Technology Forum taking place in Leeds, UK, on 1-3 April 2007. The forum was initiated by a number of UK and Chinese leading academics and organised by the University of Leeds in collaboration with Chinese Society of Particuology, Particle Technology Subject Group （PTSG） of the Institution of Chemical Engineers （IChemE）, Particle Characterisation Interest Group （PCIG） of the Royal Society of Chemistry （RSC） and International Fine Particle Research Institute （IFPRI）. The forum was supported financially by the Engineering and Physics Sciences Research Council （EPSRC） of United Kingdom,     

基于鲁棒滤波的捷联导引头视线角速度估计方法

针对捷联导引头无法直接获取视线角速度等信息的问题,研究了鲁棒滤波在大气层外飞行器捷联导引头视线角速度估计中的应用。为了建立非线性滤波估计模型,考虑目标视线角速度的慢变特性,采用一阶马尔科夫模型建立了状态方程;推导了视线角速度的解耦模型,并建立了量测方程;考虑到实际应用中存在系统噪声统计特性失准的问题,基于Huber-Based鲁棒滤波方法,设计了视线角速度滤波器,并完成了基于Huber-Based滤波方法和扩展卡尔曼滤波方法的数学仿真。仿真结果表明Huber-Based滤波方法的视线角、视线角速度及视线角加速度估计精度分别达到0.1140'、0.1423'/s、0.0203'/s2,而扩展卡尔曼滤波方法的视线角、视线角速度及视线角加速度估计精度仅分别为0.6577'、0.6415'/s、0.0979'/s~2。仿真结果证明了该方法可以有效地估计出相对视线角速度等信息,并且在非高斯噪声的条件下,依然可获得较高的估计精度,具有一定的鲁棒性。     

Guide for authors

正Each of the sections below provides essential information for authors.We recommend that you take the time to read them before submitting a contribution to Acta Mechanica Sinica.We hope our guide to authors may help you navigate to the appropriate section.How to prepare a submission This document provides an outline of the editorial process involved in publishing a scientific paper in Acta Mechanica     

Use specification of multiscale materials for life spanned over macro-, micro-, nano-, and pico-scale

Multiscale material intends to enhance the strength and life of mechanical systems by matching the transmitted spatiotemporal energy distribution to the constituents at the different scale, say—macro, micro, nano, and pico,—, depending on the needs. Lower scale entities are, particularly, critical to small size systems. Large structures are less sensitive to microscopic effects. Scale shifting laws will be developed for relating test data from nano-, micro-, and macro-specimens. The benefit of reinforcement at the lower scale constituents needs to be justified at the macroscopic scale. Filling the void and space in regions of high energy density is considered.Material inhomogeneity interacts with specimen size. Their combined effect is non-equilibrium. Energy exchange between the environment and specimen becomes increasingly more significant as the specimen size is reduced. Perturbation of the operational conditions can further aggravate the situation. Scale transitional functions and/or f_j/j+1 are introduced to quantify these characteristics. They are represented, respectively, by , and (f_mi/ma,f_na/mi,f_pi/na). The abbreviations pi, na, mi, and ma refer to pico, nano, micro and macro.Local damage is assumed to initiate at a small scale, grows to a larger scale, and terminate at an even larger scale. The mechanism of energy absorption and dissipation will be introduced to develop a consistent book keeping system. Compaction of mass density for constituents of size 10⁻¹², 10⁻⁹, 10⁻⁶, 10⁻³ m, will be considered. Energy dissipation at all scales must be accounted for. Dissipations at the smaller scale must not only be included but they must abide by the same physical and mathematical interpretation, in order to avoid inconsistencies when making connections with those at the larger scale where dissipations are eminent.Three fundamental Problems I, II, and III are stated. They correspond to the commonly used service conditions. Reference is made to a Representative Tip (RT), the location where energy absorption and dissipation takes place. The RT can be a crack tip or a particle. At the larger size scales, RT can refer to a region. Scale shifting of results from the very small to the very large is needed to identify the benefit of using multiscale materials.