Grain size and surface micro-texture characteristics and their paleoenvironmental significance of Holocene sediment in southern margin of the Gurbantunggut Desert,China

The southern margin of the Gurbantunggut Desert,China,is characterized by alternating layers of aeolian and alluvial deposits.Investigating the characteristics of arenaceous sediment in this area is of significant importance for understanding the interactive processes of wind and water forces,as well as the provenance of sediment.However,there are relatively few investigations on the characteristics of such sediment at present.In this study,we researched three aeolian-alluvial interactive stratigraphic profiles and different types of surface sediment on the desert-oasis transitional zone of southern margin of the Gurbantunggut Desert.Based on the optically stimulated luminescence(OSL)dating of aeolian sand and analyses of quartz sand grain size and surface micro-texture,we explored the aeolian-alluvial environmental change at southern margin of the desert in Holocene,as well as the provenance of sediment.The results indicated that the grain size characteristics of different types of sediment in the stratigraphic profiles were similar to those of modern dune sand,interdune sand,muddy desert surface soil,and riverbed sand.Their frequency curves were unimodal or bimodal,and cumulative probability curves were two-segment or three-segment,mainly composed of suspension load and saltation load.The quartz sand in the sediment at southern margin of the desert had undergone alternating transformation of various exogenic forces,with short transportation distance and time,and sedimentary environment was relatively humid.In Holocene,southern margin of the desert primarily featured braided river deposits,and during intermittent period of river activity,there were also aeolian deposits such as sand sheet deposits,stabilized dune deposits,and mobile dune deposits.The provenance for Holocene alluvial deposits at southern margin of the desert remains relatively constant,with the debris of the Tianshan Mountains being the primary provenance.Aeolian sand is mainly near-source recharge,which is formed by in situ deposition of fluvial or lacustrine materials in southern margin of the desert transported by wind erosion,and its provenance was still the weathered debris of the Tianshan Mountains.In addition,the sand in interior of the desert may be transported by northwest wind in desert-scale,thus affecting the development of dunes in southern margin of the desert.The results of this study provide a reference for understanding the composition and provenance changes of desert sand in the context of global climate change.

Cutting performance of micro-textured PCBN tool

To study the efect of micro-texture on the cutting performance of polyrystalline cubic boron nitide(PCBN)tools,five types of micro-textures(circular pits,eliptical grooves,transverse grooves,composite grooves,and wavy grooves)were applied to the rake surface of PCBN tools by an optical fber laser marking machine.Through a combination of three dimensional cutting simulations and experiments,the influences of micro-texture on chip-tool contact area,cutting force,chip morphology,shear angle,and surface roughness during the cuting process were analyzed.The results indicated that the chip--tool contact area and cutting force of both non-textured and micro textured tools increased with increasing cutting speed,while the shear angle decreased with increasing cutting speed.The chip-tool contact area and cutting force of the five types of micro-textured tools were smaller than those of the non textured tool The chip-tool contact area and cutting force obtained by the wavy-groove micro textured tool were the smallest.The chip radius produced by the five types of micro-textured tools was smaller than that produced by the non-textured tool,and the chip morphology was more stable.The transverse-groove micro-textured tool had a better chip breaking efect.The chip rnadius generated by the lliptical groove micro textured tool was 0.96 cm,while that generated by the wavy-groove tool varied from 0.55 cm to 1.26 cm.The presence of a micro-texture reduced the surface roughness of the workpiece by 11.73%-56.7%.Under the same cutting conditions,the five types of micro-textured tools gave a smaller chip--tool contact area,cutting force,chip radius,and surface roughness and a larger shear angle than the non-textured tool.In addition,the elliptical groove and wavy-groove micro-textured tools had better cuting performance.

Micro-textures in plagioclase from 1994-1995 eruption, Barren Island Volcano: Evidence of dynamic magma plumbing system in the Andaman subduction zone

A systematic account of micro-textures and a few compositional profiles of plagioclase from high-alumina basaltic aa lava erupted during the year 1994-1995, from Barren Island Volcano, NE India ocean, are presented for the first time. The identified micro-textures can be grouped into two categories： （i） Growth related textures in the form of coarse/fine-sieve morphology, fine-scale oscillatory zoning and resorption surfaces resulted when the equilibrium at the crystal-melt interface was fluctuated due to change in temperature or H20 or pressure or composition of the crystallizing melt; and （ii） morphological texture, like glomerocryst, synneusis, swallow-tailed crystal, microlite and broken crystals, formed by the influence of dynamic behavior of the crystallizing magma （convection, turbulence, degassing, etc.）. Each micro-texture has developed in a specific magmatic environment, accordingly, a first order magma plumbing model and crystallization dynamics are envisaged for the studied lava unit. Magma generated has undergone extensive fractional crystallization of An-rich plagioclase in stable magmatic environment at a deeper depth. Subsequently they ascend to a shallow chamber where the newly brought crystals and pre-existing crystals have undergone dynamic crystallization via dissolution-regrowth processes in a convective self- mixing environment. Such repeated recharge-recycling processes have produced various populations of plagioclase with different micro-textural stratigraphy in the studied lava unit. Intermittent degassing and eruption related decompression have also played a major role in the final stage of crystallization dynamics.

Attachment ability of combined biomimetic adhesive micro-textures of different shapes

There are various potential applications of biomimetic adhesive solutions including climbing robotic systems,mobile sensor platforms,and biomedical applications such as patches for external use.Achieving resistance to both normal and tangential loads,however,is a critical issue that still needs to be addressed.Some animals have developed exceptional attachment mechanisms based on combined fibrillar elements of different shapes and functions.Experimental investigation of combined biomimetic adhesive micro-textures on tribological performances such as adhesion,friction,and peeling resistance is needed to apply this idea to the design of an artificial texture having similar“biomimetic”properties.In the present study,we demonstrate that combinations of different shapes of biomimetic adhesive micro-textures show increased efficiency under different contact environments and enable long-term adhesive solutions.Our work sheds light on combinations of different element shapes inspired by nature and their adhesive efficiency as a function of the ratio of each biomimetic element,as well as their spatial repartition.

EBSD Characterization of Microstructure and Micro-texture in a Friction Stir-Welded DP600 Steel

The microstructure and micro-texture in different areas of a friction stir(FS)-welded DP600 steel were investigated by means of electron backscatter diffraction.The volume fraction of martensite and non-polygonal ferrite was evaluated based on the image quality(IQ)parameter.Analysis of grain boundaries revealed that the fraction of sub-grain boundaries as well as that of low-angle grain boundaries in the heat-affected zone(HAZ)and stir zone(SZ)was more than doubled compared to those in the DP600 steel base metal(BM).The micro-texture examination of the BM showed strong{112}<110>and{111}<112>components with an intensity 4.6 times of that random texture.The texture showed a memory effect in the HAZ,with a reduced overall intensity.Within the SZ,D_(1),D_(2) and E shear texture components together with a cube component were developed.Formation of these texture components of ferrite were attributed to the transformation of B and R texture components of prior austenite,which are evidences of continuous dynamic recrystallization mechanism in the SZ of the friction stir-welded DP600 steel.

Study on micro-texture and skid resistance of aggregate during polishing

The skid resistance performance of pavement is closely related to the micro-texture of pavement aggregate, while there is very few research on the relationship between micro-texture and the skid resistance. In this paper, the optical microscope is used to acquire the surface morphology of three types of aggregates including basalt, limestone and red sandstone respectively, where a total of 12 indicators are developed based on the surface texture information. The polishing effect on aggregate is simulated by Wehner/Schulze （W/S） device, during the polishing procedure, the skid resistance are measured by British Pendulum Tester （BPT）. Based on the results of independent T-test and the polishing resistance analysis, it shows that the surface texture of basalt is significantly different between limestone and red sandstone. Three indicators including the average roughness （Ra）, the kurtosis of the surface （Sku） and the mean summit curvature （Ssc） are selected to describe the characteristics of aggregate micro-texture based on the correlation analysis. The contribution of micro-texture to the skid resistance can be described with the secondary polynomial regression model by these indicators.

Surface micro-texture on sapphire fabricated by laser ablation trajectory regulation

Fabrication of the surface micro-texture on the C-plane sapphire is undertaken by a355 nm Ultraviolet(UV)pulsed laser.The surface micro-textures of sapphire with different laser scanning line spacing ranging from 10 lm to 100 lm are obtained,where the selection range of scanning line spacing is controlled in the range of the groove width and plasma width to obtain a surface of high Peak-Valley(PV)value.A reasonable processing order is proposed to manufacture different types of surface micro-textures on sapphire by laser ablation trajectory regulation.In the multiple-passes laser ablation of sapphire by the UV nanosecond pulsed laser,the scanning lines in each direction is treated as once scanning.On this basis,the multiple processing can be carried out to avoid the influence of the subsequent scanning on the machined groove.In addition,the effect of different scanning line spacing on the PV value is quantified and different types of surface microtextures on sapphire,including the squares,the rhombuses and the hexagons,are successfully fabricated,which can be applied in the friction reduction or anti-reflection field.

Numerical micro-texture optimization for lubricated contacts-A critical discussion

Despite numerous experimental and theoretical studies reported in the literature,surface micro-texturing to control friction and wear in lubricated tribo-contacts is still in the trial-and-error phase.The tribological behaviour and advantageous micro-texture geometries and arrangements largely depend on the contact type and the operating conditions.Industrial scale implementation is hampered by the complexity of numerical approaches.This substantiates the urgent need to numerically design and optimize micro-textures for specific conditions.Since these aspects have not been covered by other review articles yet,we aim at summarizing the existing state-of–the art regarding optimization strategies for micro-textures applied in hydrodynamically and elastohydrodynamically lubricated contacts.Our analysis demonstrates the great potential of optimization strategies to further tailor micro-textures with the overall aim to reduce friction and wear,thus contributing toward an improved energy efficiency and sustainability.

Microstructure and texture of electroformed copper liners of shaped charges

The microstructures of copper liners of shaped charges prepared byelectroforming technique were investigated by transmission electron microscopy (TEM). Meanwhile, theorientations distributing of the grains in the electroformed copper liners of shaped charges wasexamined by the electron backscattering Kikuchi pattern (EBSP) technique. TEM observations haverevealed that these electroformed copper liners of shaped charges have the grain size of about 1-3mu m and the grains have a preferential orientation distribution along the growth direction. EBSPanalysis has demonstrated that the as-formed copper liners of shaped charges exhibit amicro-texture, i.e. one type of fiber texture, and the preferred growth direction is normal to thesurface of the liners.

Contribution of underlying terrain to sand dunes: evidence from the Qaidam Basin, Northwest China

Underlying terrain strongly influences dune formation.However,the impacts of underlying terrain on the dune formation are poorly studied.In the present research,we focused on dunes that formed in the alluvial fans and dry salt flats in the Qaidam Basin,Northwest China.We quantified the dunes'sediment characteristics on different types of underlying terrain and the terrain's effects on the surface quartz grains by analyzing grain-size distribution,soluble salt contents and grain surface micro-textures.Results showed that barchan dunes were dominated by medium sands with a unimodal frequency distribution,whose peak corresponded to the saltation load.Linear dunes were mainly composed of fine sands with a bimodal frequency distribution,whose main peak represented the saltation load,and whose secondary peak represented the modified saltation or suspension load.Sand was transported from source area by running water(inland rivers)over short distances and by wind over relatively longer distances.Thus,quartz grains had poor roundness and were dominated by sub-angular and angular shapes.Surface micro-textures indicated that dune sands were successively transported by exogenic agents(glaciation,fluviation and wind).Soluble salt contents were low in dunes that developed in the alluvial fans,which represented a low-energy chemical environment,so the grain surface micro-textures mainly resulted from mechanical erosion,with weak micro-textures formed by SiO2 solution and precipitation.However,soluble salt contents were much higher in dunes that developed in the dry salt flats,which indicated a high-energy chemical environment.Therefore,in addition to micro-structures caused by mechanical erosion,micro-textures formed by SiO2 solution and precipitation also well developed.Our results improve understanding of the sediment characteristics of dune sands and the effects of underlying terrain on dune development in the Qaidam Basin,China.

Study on the Cutting Temperature of the Textured Tool by 3D FEA Simulation

Temperature plays an important role in the life of cutting tools.However,it is sometimes difficult to observe instantaneously because of limited data acquisition,especially for the textured tool.In this paper,the performance of microgroove textured cutting tools for three-dimensional(3D)oblique dry turning of AISI 1045 steel was studied by finite element simulation.The effects of width,depth and spacing of strip micro-texture on cutting temperature and the effect of cutting speed on cutting temperature of strip microtexture tool were studied.The results show that the maximum temperature of the tool and the tip temperature first increase and then decrease with the increase of micro-texture width.When the micro-texture depth increases,the maximum temperature and the tool tip temperature decrease first and then increase.The highest temperature and tip temperature of the tool gradually increase with the increase of micro-texture spacing.The highest temperature and tip temperature of the tool increase with the increase of cutting speed,feed speed and cutting depth.In addition,the effective mechanism of micro-texture parameter for the temperature was proposed.It provides profound guidance for optimizing the microstructure parameters and cutting process of cutting tools according to cutting temperature in this study.It also provides an effective and practical method for the design,innovation and development of microtextured tools.

Laboratory and field evaluation of asphalt pavement surface friction resistance

Pavement surface friction is a significant factor for driving safety and plays a critical role in reducing wet- pavement crashes. However, the current asphalt mixture design procedure does not directly consider friction as a requirement. The objective of this study was to develop a surface friction prediction model that can be used during a wearing course mixture design. To achieve the objective, an experimental study was conducted on the frictional characteristics of typical wearing course mixtures in Louisiana. Twelve wearing course mixtures including dense-graded and open-graded mixes with different combinations of aggregate sources were evaluated in laboratory using an accelerated polishing and testing procedure considering both micro- and macro texture properties. In addition, the surface frictional properties of asphalt mixtures were measured on twenty-two selected asphalt pavement sections using different in situ devices including Dynamic Friction Tester （DFT）, Circular Texture Meter （CTM）, and Lock-Wheel Skid Trailer （LWST）. The results have led to develop a procedure for predicting pavement end-of-life skid resistance based on the aggregate blend polish stone value, gradation parameters, and traffic, which is suited in checking whether the selected aggregates in a wearing course mix design would meet field friction requirements under a certain design traffic polishing.

Improvement of Surface Ridging Resistance of an Ultra-purified Ferritic Stainless Steel by Optimizing Hot Rolling Condition

The effects of the finisher entry temperatures（FETs） on the surface ridging behavior for an ultra-purified21%Cr ferritic stainless steel have been investigated. The results indicate that decreasing the FET facilitates the formation of in-grain shear bands in the hot rolled slab. The in-grain shear bands supplied recrystallization nucleation sites in grains during subsequent annealing through coalescence of subgrains, which is beneficial to refine the microstructures and intensify the {111}//ND textures. This effect will evolve to the final cold rolled and annealed sheet. The micro-texture analysis indicates that the formation of grain colony in the final sheet is weakened by decreasing the FET. Then, the surface ridging resistance of FSS is enhanced due to the optimizing of micro-texture distribution.