Theoretical Modeling and Surface Roughness Prediction of Microtextured Surfaces in Ultrasonic Vibration-Assisted Milling

Textured surfaces with certain micro/nano structures have been proven to possess some advanced functions,such as reducing friction,improving wear and increasing wettability.Accurate prediction of micro/nano surface textures is of great significance for the design,fabrication and application of functional textured surfaces.In this paper,based on the kinematic analysis of cutter teeth,the discretization of ultrasonic machining process,transformation method of coordinate systems and the cubic spline data interpolation,an integrated theoretical model was established to characterize the distribution and geometric features of micro textures on the surfaces machined by different types of ultrasonic vibration-assisted milling(UVAM).Based on the theoretical model,the effect of key process parameters(vibration directions,vibration dimensions,cutting parameters and vibration parameters)on tool trajectories and microtextured surface morphology in UVAM is investigated.Besides,the effect of phase difference on the elliptical shape in 2D/3D ultrasonic elliptical vibration-assisted milling(UEVAM)was analyzed.Compared to conventional numerical models,the method of the cubic spline data interpolation is applied to the simulation of microtextured surface morphology in UVAM,which is more suitable for characterizing the morphological features of microtextured surfaces than traditional methods due to the presence of numerous micro textures.The prediction of surface roughness indicates that the magnitude of ultrasonic amplitude in z-direction should be strictly limited in 1D rotary UVAM,2D and 3D UEVAM due to the unfavorable effect of axial ultrasonic vibration on the surface quality.This study can provide theoretical guidance for the design and fabrication of microtextured surfaces in UVAM.

Grain structure and microtexture evolution during superplastic deformation of 5A90 Al-Li alloy

The microstructural evolution of banded 5A90 A1-Li alloy during superplastic deformation at 475℃ with an initial strain rate of 8× 10^-4 S^-1 was studied using EBSD technique. The results showed that, before deformation, the grain shape appeared to be banded, the most grain boundaries belonged to low-angle boundaries, and the initial sheet had a dominate of { 110}（112） brass texture. During deformation, there were grain growth, grain shape change, misorientation increasing and textural weakening. The fraction of high-angle boundaries increased rapidly once the flow stress reached the peak value. Corresponding deformation mechanism for various stages of deformation was suggested. Dislocation activity was the dominant mechanism in the first stage, then dynamic recrystallization occurred, and grain rotation was expected as an accommodation for grain boundary sliding （GBS）. At large strains, GBS was the main mechanism.

Microstructure and microtexture evolution of undercooled Ni-15%Cu alloy

Rapid solidification of undercooled Ni-15%Cu （mole fraction） alloy was studied using glass fluxing and cyclic superheating. To show the effect of cooling history on the microstrucyure and microtexture evolution, the as-solidified samples were either cooled naturally or quenched into water after recalescence. At low undercooling, grain-refined microstructure has a random texture and a highly oriented texture without annealing twins for the case of naturally cooling and quenching, respectively. At high undercooling, a fully random texture as well as a number of annealing twins are observed, and recrystallization and grain growth independently happen on the cooling history. Fluid flow and recrystallization play an important role in the microtexture formation for grain refinement at both low and high undercooling.

Surface Microtextures of Slipping Zone Soil of Some Landslides in the Three Gorges Reservoir District and Their Significance

The mineral assemblage and content and surface microtextures of slipping zone soil of several landslides in the Three Gorges Reservoir District have been analyzed using the scanning electron microscope (SEM) and X-ray diffractometer (XRD). All the mineral assemblages are similar in these landslides. The main minerals are montmorillonite, illite, kaolinite, chlorite, quartz and feldspar. There are two kinds of surface microtexture in the slipping zone soil, i.e., linear scratches and arcuate scratches. Based on analyses of the changes of the microtextures, one can obtain information about the number, directions and stages of landslide movements. The authors have also studied the mechanism of landslide formation, evaluated the stability of landslides and revival possibility of ancient landslides and forecasted the activity of similar landslides in different districts. The surface microtexture features of stable landslides and mobile landslides are summarized and it is concluded that the existence of filamentous bacteria may result in or increase movements of landslides.

Effects of micrite microtextures on the elastic and petrophysical properties of carbonate reservoirs

Apparent differences in sedimentation and diagenesis exist between carbonate reservoirs in different areas and affect their petrophysical and elastic properties.To elucidate the relevant mechanism,we study and analyze the characteristics of rock microstructure and elastic properties of carbonates and their variation regularity using 89 carbonate samples from the different areas The results show that the overall variation regularities of the physical and elastic properties of the carbonate rocks are controlled by the microtextures of the microcrystalline calcite,whereas the traditional classification of rock-and pore-structures is no longer applicable.The micrite microtextures can be divided,with respect to their morphological features,into porous micrite,compact micrite,and tight micrite.As the micrites evolves from the first to the last type,crystal boundaries are observed with increasingly close coalescence,the micritic intercrystalline porosity and pore-throat radius gradually decrease;meanwhile,the rigidity of the calcite microcrystalline particle boundary and elastic homogeneity are enhanced.As a result,the seismic elastic characteristics,such as permeability and velocity of samples,show a general trend of decreasing with the increase of porosity.For low-porosity rock samples(φ<5%)dominated by tight micrite,the micritic pores have limited contributions to porosity and permeability and the micrite elastic properties are similar to those of the rock matrix.In such cases,the macroscopic physical and elastic properties are more susceptible to the formation of cracks and dissolution pores,but these features are controlled by the pore structure.The pore aspect ratio can be used as a good indication of pore types.The bulk modulus aspect ratio for dissolution pores is greater than 0.2,whereas that of the intergranular pores ranges from 0.1 to 0.2.The porous and compact micrites are observed to have a bulk modulus aspect ratio less than 0.1,whereas the ratio of the tight micrite approaches 0.2。

A preliminary study on microtextures，structures and mineralizing processes of hydrothermal chimneys in Mariana Trough

Microtextures and struetures of 9 hydrothermal chimneys sampled on the small spreading ridge Of the Mari ana Trough during SONNE Cruise 57 (SO57) and 69 (SO69) in 1988 and 1990 were studied by means of scanning electron microscope. The results reveal that the two types of chimneys from the Mariana Trough. the 'silicic chimneys' containing Fe sulfide and the pure 'silica chimneys' without sulfide, vary distinctly not only in mineral and chemical compositions, but also in microtextures and structures. The silicic chimneys generally show three major types of microtextures.The inside of the chimneys is dominated by holocrystalline or semicrystalline idiomorphic and hypidiomorphic granular textures and the outwall by amorphous colloidal texture. In some of the silicic chimneys relict texture is observed. However,the pure silica chimneys show chiefly amorphous colloidal texture from the inside to the outwall. Microstructurally. theinside of the silicic chimneys is dominated by a 'silica-covering' structure and a 'voidfilling' structure, and the outwall by a chain-like or three-dimentional chain-network structure built up by individual opal globules, whereas the pure silica chimneys are mainly three-dimentional chain-network and the dense silica bands in structure. These variations suggest that not only mineralizing conditions but also processes differ distinctly during the formation of the two types of chimneys, and that hydrothermal mineralization in the Mariana Trough shows a multistage or multieplsodical nature.

Method of ameliorating the lubrication and friction performance of an engine based on different microtextures

A design of different microtextures on the surface of the crankpin bearing(CB)is proposed to ameliorate the lubrication and friction performance(LFP)of engines.On the basis of the CB s hydrodynamic lubrication model,the bearing surface of CB using different microtextures,such as wedge-shaped textures(WSTs),square textures(STs),circular textures(CTs),and combined square-circular textures(CSCTs),is simulated and assessed under various external loads of the CB at an engine speed of 2000 r/min.The pressure of the oil film,the frictional force,the force of the solid asperity contact,and the friction coefficient of the CB are used as objective functions.Results indicate that the bearing surface designed by the STs remarkably improves the CB s LFP in comparison with other structures of WSTs,CTs,and CSCTs.Particularly,the average values of the frictional force,solid asperity contact,and friction coefficient of the CB using the STs are greatly reduced by 28.5%,14.5%,and 33.2%and by 34.4%,26.3%,and 43.6%in comparison with the optimized CB dimensions and CTs,respectively.Therefore,the application of the STs on the CB surfaces can enhance the LFP of engines.

The Relationship between Microtexture Types and Indices of Physico-Mechanical Properties of Loess in China

The paper deals mainly with the relationship between the microtexture types and the indices of physicomechanical properties of loess. The results of study demonstrate that the study of microtextures of loess is of importance in the prediction and preliminary evaluation of engineering geological properties of loess in a region.

磁铁矿:研究方法与矿床学应用

磁铁矿在自然界普遍存在,其成岩和成矿作用研究备受关注。文章系统地总结了近年来磁铁矿的研究进展,介绍了磁铁矿的研究方法体系,并探讨了其在矿床学研究中的应用。磁铁矿的研究方法包括磁铁矿的年代学、显微结构、元素和同位素组成。在磁铁矿的方法学基础上,进一步探讨了磁铁矿Re-Os同位素定年在成矿年代学研究中的应用、磁铁矿有关的温度计和氧逸度计以及矿床类型判别等。此外,以铁氧化物-铜-金和铁氧化物-磷灰石矿床为例,讨论了磁铁矿微量元素组成对这些矿床成因的制约,并初步总结了磁铁矿微量元素组成在找矿勘查方面的应用。磁铁矿作为重要的矿床学研究对象,已助推矿床成因和找矿勘查研究,具有巨大的应用潜力,包括原位U-Pb年代学和非传统稳定同位素示踪(如V同位素)等。然而,磁铁矿中微量元素的赋存状态、分配行为以及磁铁矿地球化学数据库等是磁铁矿研究中较薄弱的环节,亟需进一步加强。

超高速干气密封微织构气膜润滑特性研究

针对航天航空领域,设备超高速、高压运转,干气密封稳定性问题,依据槽型织构优化设计,提出一种槽底微织构螺旋槽干气密封结构,以解决密封在超高速旋转过程中气膜稳定性问题。基于气体润滑理论,建模、划分网格,再导入FLUENT软件对流场进行仿真模拟;改变工况参数和槽型结构参数后,在超高速、高压工况下,相比于普通螺旋槽,槽底微织构螺旋槽干气密封的动压效果有显著提升。结果表明,槽深h_(g)=6μm,膜厚h_(0)=2μm,微织构槽深δ=2μm、微织构槽宽取3.97 mm,微织构槽位于螺旋槽底中间位置时,槽底微织构螺旋槽相比于普通螺旋槽可产生明显的动压效应。

微织构排布方式对水润滑轴承启停过程摩擦学性能的影响

梯度排布微织构在提升水润滑轴承摩擦学性能方面具有显著效果,然而梯度排布微织构在水润滑轴承中的应用仍缺乏系统性研究。为了探究梯度排布微织构对水润滑轴承启停过程摩擦学性能的影响,基于Greenwood-Tripp微凸体接触模型、Archard磨损模型求解轴瓦表面的磨损量。通过CFT-I材料表面性能综合测试仪对CNC雕刻机加工的织构化表面进行水润滑条件下的摩擦学试验研究。针对光滑、单一圆形织构、圆形与三角形以轴向交错平行■和周向交错平行分布(1212)方式梯度排布的表面,测量各个表面的磨损量和摩擦因数。通过立体显微镜、扫描电子显微镜对摩擦磨损试验前后的表面形貌和摩擦因数进行分析。数值模拟和试验结果显示,与光滑表面和单一织构化表面相比,梯度排布微织构化表面磨损量和摩擦因数显著降低;圆形与三角形以■方式的梯度排布微织构化表面摩擦学性能最佳,接触表面磨损量最小、表面摩擦因数最低。梯度排布微织构在流体润滑过程中相互影响,可以起到提高轴承表面举升力,减少表面接触,降低表面磨损和摩擦因数的作用。研究不同形状、排布方式下梯度排布微织构化表面的磨损量和摩擦因数的变化规律,可为舰船装备水润滑轴承研制阶段主动设计提供理论基础。

Mechanically driven assembly of biomimetic 2D-material microtextures with bioinspired multifunctionality

Nature provides a wealth of bio-inspiration for advanced material research.Assembling various nanomaterials into biomimetic microtextures with bioinspired functionalities has spurred increasing research interests and facilitated technological advances in various applications.In recent years,two-dimensional materials(2DMs)have emerged as important building block units in the biomimicry field due to their distinct chemical,physical,electrical,electrochemical,and catalytic properties.In this review article,various mechanically driven assembly approaches are summarized to fabricate various genealogies of biomimetic 2DM microtextures with bio-inspired multifunctionality.First,sequential deformation strategies are discussed to programmably construct higher dimensional 2DM microtextures,ranging from wrinkles/crumples(one-time deformation)to multiscale hierarchies(multiple deformations).Next,the current progress using higher dimensional 2DM microtextures to imitate different biological structures and/or induce bio-inspired multifunctionality is systematically summarized.Four showcases of bio-inspiration and biomimicry using different 2DM nanosheets are highlighted:(1)wrinkle patterns of an earthworm that spur the design of strain sensors with programmable working ranges and sensitivities,(2)wrinkle appearance of a Shar-Pei dog that motivates the fabrication of stretchable energy storage devices,(3)hierarchical scale textures of a desert lizard that inspire cation-induced gelation platforms for 2DM aerogels,and(4)wrinkle skin of an elephant that influences the development of 2DM protective skin for soft robots.Finally,challenges and future opportunities of adopting 2DM nanosheets to assemble biomimetic microstructures with synergistic functionalities are discussed.

非对称织构对YT15硬质合金刀具切削性能及其衍生切削的影响

为研究非对称织构对刀具的切削性能及其对衍生切削的影响,基于Johnson-Cook模型,利用有限元分别进行无织构刀具(NT)、正向非对称织构刀具(FT)和反向非对称织构刀具(RT)切削45钢的仿真分析,并进行相应的切削实验,对比分析了NT、FT和RT的切削力、切削温度、切屑形态、衍生切削和刀具磨损等。研究发现非对称织构刀具的切削性能要优于无织构刀具,但织构的存在同时会诱发衍生切削现象,对切削性能产生一定的负面影响,加剧刀具磨损。NT、RT和FT的平均主切削力分别为601.9、196.4和419.1 N,织构刀具的切削力较无织构刀具减少了约30.4%~67.4%。结果表明,引入织构后有利于增大剪切角、降低切削力、改善刀尖温度分布和减少切屑的黏附,提高切削稳定性;但织构诱发的衍生切削会加剧织构在切屑流出端的刀面磨损,会在一定程度上影响切削温度、增大切削力,织构与衍生切削的耦合作用使得RT的切削性能优于FT。

Microstructure and microtexture evolution characteristics of a powder metallurgy Ni-based superalloy during static recrystallization

Static recrystallization(SRX)characteristics of a powder metallurgy superalloy were investigated by isothermal compression at 1080–1170°C under strain rates of 0.01–0.1 s−1,strains of 0.1,0.22,or 0.5,and holding time of 0–300 s.The impacts of temperature,strain rate,holding time,and strain on the SRXed grain size,volume fraction,and microtexture were explored by electron backscatter diffraction technique.It was found that temperature played a key role in these processes.As SRX progressed,the<110>fiber parallel to the axis compression direction gradually weakened and was replaced by the<001>fiber because<001>was the preferred recrystallization orientation and grain growth direction for the Ni-based superalloy.Moreover,high temperatures and low strain rates promoted the formation of the<001>fiber.Three nucleation mechanisms during SRX process were found:grain boundary bulging,primary twin assistance,and subgrain coalescence.Grain boundary bulging occurred under all process conditions;however,at low temperatures and high strain rates,the latter two mechanisms could provide additional nucleation modes.In addition,SRX size and volume fraction models were established.

不同形状的表面织构刀具仿真车削Inconel 718合金研究

目的针对目前车削Inconel 718镍基高温合金主要面临的可加工性差和刀具磨损两个问题,提出表面微织构技术进行刀具设计与制备。方法首先建立微织构刀具的理论刀-屑接触长度模型,其次,利用理论刀-屑接触长度模型,建立表面织构刀具切削力的理论模型以及切削热的理论模型;最后,根据理论刀-屑接触长度的变化规律,对微织构刀具的切削力、切削温度进行理论分析,并最终建立有限元仿真模型。结果通过有限元仿真结果表明微织构刀具比硬质合金刀具的车削性能要好。结论与硬质合金刀具的切削力对比,微织构刀具的三向切削力均偏小;且轴向力、径向力在一定范围内波动,主切削力呈增长趋势。与硬质合金刀具的切削温度对比,微织构刀具可以降低切削过程中切削热,且圆形微织构刀具是3种微织构刀具中切削温度最低的;与硬质合金刀具对比,表面微织构可以降低刀具表面磨损问题,减少刀具与切屑的挤压作用和摩擦作用,且不同形状的表面织构产生的磨损深度不同。

微织构固结磨料抛光轮无水抛光熔融石英光学元件技术研究

抛光是精密光学元件制造的最后一道冷加工工序,当前采用的游离磨料抛光技术蕴含的不可控因素较多,且会在元件表面产生水合层并存在磨料浪费等问题。为了实现可控绿色抛光并确保光学元件达到所需的表面质量要求,固结磨料无水抛光技术以其独特的优势开始得到推广。然而,固结磨料抛光轮在加工时磨损剧烈,耐用性和散热性有所欠缺。因此,在抛光轮上构建螺旋形微织构图案,以压力、转速比、微织构纹理的曲率和条数作为影响因素设计了正交试验,得到了最佳抛光工艺参数。实验表明,与无织构普通抛光轮相比,螺旋形微织构抛光轮能够显著提高砂轮磨损性能,并且在加工过程中能够保证熔融石英元件材料去除率和表面粗糙度收敛。

微观织构表面质量对径向滑动轴承油膜承载性能的影响

研究滑动轴承的表面形貌及其表面质量对转子-滑动轴承的动压润滑承载力性能的影响。构建考虑轴瓦微观织构及其表面形貌的径向轴承动压润滑模型,采用自相关函数构建转子-轴承围观表面形貌,采用有限差分法数值求解考虑轴瓦微观织构表面形貌流体动压的雷诺方程。构建考虑转子轴承微观形貌的油膜承载性能的数值计算的模型,数值分析轴承的油膜压力分布及静特性,结果与经典结论高度一致,验证了算法的可靠性。结果表明:微观织构对滑动轴承油膜压力及承载力较光滑轴承有明显提高,且承载力随着织构高度及排布密集程度的增加而增加。转子轴承系统承载力随着转子轴承表面粗糙度增加而增加。进一步增加粗糙度,将破坏原转子轴承油膜轴向连续性,转子轴承系统的承载力将下降。构建的考虑轴瓦微观织构及其表面形貌的径向轴承动压润滑模型为转子轴承模型,为滑动轴承织构尺寸及其表面加工质量要求提供理论依据。

Microtextural Characteristics and Origin of Dolomites in the Tepearasi Formation, SW of Beysehir-Konya, Turkey

The Tepearasi Formation of the autochthonous Geyikdagi Group in the CentralTauride Belt, SE of Beysehir, is Dogger in age and consists dominantly of massive limestones andgreyish dolomites occurring within the middle to upper sections. The total thickness of thedolomitic levels ranges from 100-300 m and laterally extends 500-700 m. Three types of dolomite weredistinguished through petrographic analyses: homogeneous, mottled (saddle-crystalline) andjoint-filling dolomite, which were interpreted to have formed in two different stages, earlydiagenetic and late diagenetic. The homogeneous dolomite of the early diagenetic stage islight-coloured and monotonous-textured and shows the form of a dolosparite mosaic. The mottleddolomite formed in the late diagenetic stage is light- to dark-coloured and coarsely granularidiomorphic. The other type of late diagenetic dolomite, described as the joint-filling type,presents a crystal growth pattern from the joint walls towards the centre of the joint space. It isassociated with coarse calcite crystals as well as primary dolomite crystal clasts which were formedin the early diagenetic stage. In addition to these characteristics, cataclastic texture indicatingthe influence of tectonism is also observed. Microtexture-oriented scanning electron microscopy(SEM) studies indicate that mottled dolomites show zonal structures and contain secondarydissolution vugs. SEM studies also revealed the existence of some remains (calcite, clay etc.) injoint-filling dolomites. Analyses by energy dispersive spectrometry (EDS) indicate the existence ofclay minerals (likely to be illite) in the pores of dolomite. Isotope studies conducted to shedlight onto the origin of the dolomites of the Tepearasi Formation yielded the results of delta^18O=-2.48 to - 3.87 per thousand and delta^13C=0.93 to l.12 per thousand for the early diagenetichomogeneous dolomites. Mottled and joint-filling type dolomites of the late diagenetic stage, on theother hand, gave the results of delta^18O = -5.42 to -7.12 per thousand, and delta^13C= -2.29 and-5.70 respectively. X-Ray diffractometry (XRD) and energy dispersive analysis X-Ray (EDAX), atomicabsorption spectrometry (AAS) analyses, results of petrographic data, and delta^18O and delta^13Cvalues suggest that the early diagenetic dolomitization in the Tepearasi Formation occurred underthe control of hypersaline (rich in Mg) and fresh water mixing zone. The late diagenetic dolomitespartly developed under the control of tectonic thrusting.

GH4169高温镍基合金微织构刀具切削力优化设计及预测

为了研究微织构参数对切削力的影响规律,运用AdvantEdge专业切削有限元仿真软件对GH4169高温镍基合金进行微织构刀具二维切削仿真,用极差分析确定微织构参数对切削力的影响规律,使用SPSS软件构建二维微织构切削力预测模型。仿真结果表明,微织构参数对切削力影响顺序为间距>深度>刃边距>宽度,最佳水平是A_(2)B_(1)C_(2)D_(4),与无织构刀具相比,微织构刀具的切削力和切削温度明显降低,最佳水平A_(2)B_(1)C_(2)D_(4)具有良好的切削适应性,主切削力Fx和径向力Fy预测方程的拟合优度R2分别为0.999和0.929。

发动机缸孔椭圆开口偏置类抛物线微织构研究

为探究更有利于提高汽车发动机活塞环/缸套摩擦副性能的微织构,在某发动机活塞环/缸套摩擦副设计椭圆开口偏置类抛物线微织构,综合运用CCD实验设计和响应面优化理论,采用CFD方法研究该微织构特征参数对活塞环/缸套摩擦副摩擦因数和承载压力的影响规律;建立相应的数学模型,并运用鲸鱼优化算法对微织构参数进行多目标优化设计。结果表明:微织构参数对活塞环/缸套摩擦副摩擦因数程度由大到小依次为密度、长半轴、深度、偏置量、短半轴,对承载压力的影响程度由大到小依次为密度、深度、偏置量、长半轴、短半轴;所建相应数学模型具有足够的精度,可用于依据微织构特征参数对摩擦副相关性能的准确预测。得出的微织构最优参数为:椭圆长半轴390μm,短半轴108μm,偏置量139μm,深度42μm,织构密度0.69。与未织构摩擦副相比,按照最优微织构参数织构化的活塞环/缸套摩擦副的承载压力提升了2.67%,摩擦因数降低了32.1%。