Texture Micro Research Articles

Influence of diamond-like carbon coatings and micro-texturing on friction and wear of seal interfaces: Experiment and simulation study

For mechanical seal friction vice in dry friction conditions, due to friction wear serious failure, is the slurry pump and other instruments in the operation of the process of the urgent need to solve the problem. In this paper, in order to optimize and enhance the friction and wear problem of mechanical seal end face of slurry pump. Surface treatment of mechanical sealing rings with diamond-like carbon (DLC) coating and surface microtexturing, and at different rotational speeds and normal forces, the surface hardness, wear coefficient and dry friction coefficient of the sealing rings were analyzed by experimental comparison, and the wear morphology was collected by electron microscopy, having analyzed the results of the sets of, the end face structure of the mechanical seal was optimized. Based on Archard wear model simulation calculations, the seal ring wear depth and wear quality were obtained. The results show: under dry friction conditions, the synergistic effect of the DLC coating and the surface micro-texture (MT), the coefficient of friction is reduced by approx. 68% and the quality and depth of wear is minimized. Excessive speeds and normal forces are more prone to wear behavior caused by abrasive wear. Simulation results of surface treatment groups, DLC / MT group maximum wear depth is the smallest; wear quality test and simulation of the maximum error within 15.7%. The results of the study can provide a basis for a phosphoric acid plant slurry pump mechanical seal design.

비등방성 로킹을 위한 금속의 하이브리드 마이크로 텍스쳐링 가공법

In this paper, a novel hybrid micro texturing method that combines laser beam machining and electrochemical etching was suggested. In this new machining process, tungsten anisotropic micro channel that was used for directional locking was fabricated. First, laser beam machining on a tungsten workpiece with tilted condition was adopted to rough texturing. Subsequently, a recast layer with tungsten oxide was generated that covered the original anisotropic channel shape, causing a low surface quality. For this reason, electrochemical etching was carried out to elute the recast layer into electrolyte. Moreover, EDS analysis that observed the atomic distribution of textured micro channel was performed to verify the principle of the suggested hybrid process. In the finally fabricated anisotropic micro channel after the hybrid texturing process, the interlocking force (maximum 133.44 N, 5×5 mm²) was measured using the load cell.

Experimental evaluation of surface generation and force time-varying characteristics of curvilinear grooved micro end mills fabricated by EDM

Conventional cutting fluids as coolants and lubricants are being widely used in various machining processes, but these cutting fluids give rise to biological and environmental problems. The advantages of implanting micro texture on macroscopic cutting tools have been proved widely in implementing sustainable machining. But seldom studies focused on preparing micro texture on the surface of micro end mill with diameter less than 1 mm. In this study, an attempt has been made to create curvilinear grooved micro textures on the rear surface of double helical micro end mills with diameter of about 800 μm by electrical discharge machining (EDM) method for lowering specific milling energy and forces. Then, dry micro milling experiments were performed on aluminum alloy material using micro end mills with or without curvilinear grooved micro textures. The surface generated mechanism, force time- varying characteristics, specific milling energy, chip capacity and tool wear form of curvilinear grooved micro end mills in dry micro milling are revealed. Besides, the effects of structural parameters of micro textures and process parameters on specific milling energy and dry micro milling forces are discussed. Experimental results disclosed that the average specific cutting energy involved in dry micro milling process of aluminum alloy material machined by micro end mill with curvilinear grooved micro textures is decreased by 21.35%. The normal and tangential forces are significantly reduced compared to ordinary micro end mill. The voids and stomatal located in micro textures fabricated by EDM method are found to be conductive to store and accommodate some extrusion chips. For micro end mill with curvilinear grooved micro textures, the oxidative wear is more serious but the adhesion wear is slighter than ordinary micro end mill. This research is expected to prepare and optimize micro textured micro end mills suitable for dry micro milling process, which has important theoretical significance and engineering application value.

INVESTIGATIONOF FRICTION COEFFICIENTOF DRAPERY FABRICS TREATED WITH DIFFERENT RATIO OF FLAME RETARDANT

As the security precautions with respect to new standards for the furnishing textiles in big platforms such as concert, theatre halls have increased, flame retardancy has become one of the vital required property for drapery fabrics. However, those kind of additional treatment processes may lead to some differences in fabric properties such as friction which should be considered for the consumers. This study aims to evaluate the influence of using different ratio of flame retardant chemicals (g/l) on friction coefficient of drapery fabrics. For this purpose, nine types of fabrics composed of three different weft density (9, 11, 13 threads/cm) were selected. The warp yarns were selected as 400/200 denier/filament while the weft yarns were selected as 800 /200 denier/filament textured micro polyester yarns. Three levels for flame retardant (0, 60 and 90 g/l) were determined as the finishing processes. After the dobby fabrics were woven and exposed to finishing treatments; Friction coefficient values were recorded with Labthink Param MXD-02. ANOVA tests were performed in order to evaluate the significant effect of weft density and flame retardant chemical ratio on friction properties of drapery fabrics. Additionally, SNK tests were conducted for the comparison of means of friction values of drapery fabrics produced at different weft density also of the samples treated with different flame retardant chemical ratio. Experimental results revealed that structural parameters and the finishing processes were influential factors on the surface frictional characteristics of the fabrics. It was clearly observed that surface friction coefficients of drapery fabrics decreased due to the flame retardant process.

Surface Microtexture Fabrication and Temperature Gradient Regulation of Micro Wankel Engine

Nowadays, micro engine miniaturization is one of the most challenging issues, especially for the design and fabrication of the high-power-density micro Wankel engine. With the decrease of the size of the micro engine, the problem of the heat deformation of the cylinder becomes more serious. In this paper, a micro Wankel engine with microtextures on the outer surface of the cylinder is designed and manufactured to diffuse the heat dissipation and regulate the temperature gradient, so as to increase the power output density. First, a series of finite element simulations are conducted to design a type of ideal surface microtexture. Then, the machining condition is optimized to fabricate microtextures by micro cutting on the cylinder surface by studying the processing parameters. Finally, the performance of the new micro Wankel engine in terms of the temperature gradient regulation and the mechanical power output is tested and compared with that of the un-textured micro engine. The comparison results show that temperature of the textured micro engine was dropped from 185 °C to 125 °C and the mechanical power output increased by 10.74% from that of its un-textured counterpart, verifying the proposed methods for temperature gradient regulation.

The performance and stability of three-lobe journal bearing textured with micro protrusions

The present research work deals with studying the steady state performance and dynamic stability of sliding element hydrodynamic bearings of the three-lobe type and provided with a bushing surface textured with uniform micro protrusions. A mathematical model has been put forward for the problem using the Reynolds equation governing the unstable fluid lubrication inside the bearing as well as the equations governing the dynamic movement of the journal. The equations have been put in their numerical forms suitable for computer solution using the finite difference method. Two types of three lobe bearings have been considered, one with its plain bushing and the other with bushing textured with uniform micro protrusions. This is in addition to other two plain journal bearings one with plain bushing and the other with textured bushing. This is for the purpose of carrying out a general comparison to include the steady performance of these bearings in terms of their load carrying capacity and the friction losses in their parts in addition to their dynamic stability. It was concluded in the present work that the inclusion of these textured micro protrusions in the bushing of bearings, whether they are plain or of the three-lobe geometry improves their performance in terms of reducing their friction losses and raising their load carrying capacity along. It was found that the three-lobe bearing with protruded bushing surface texture is superior to the other types of bearings considered in the present work as far as steady state performance is concerned. Regarding the margin of stability to small sinusoidal disturbances the protruded three-lobe bearing shows a relatively lower margin. Some useful recommendations for future research work in this field of study are given in this work and the most important one is to carry out extensive experimental studies on sliding bearings surfaces fitted with textured bushings of different micro protrusions designs.

Facial Expression Recognition From Depth Video With Patterns of Oriented Motion Flow

In this paper, we propose a novel feature representation method by a new feature descriptor, named patterns of oriented motion flow (POMF) from the optical flow information, to recognize the proper facial expression from the facial video. The POMF computes different directional motion information and encodes the directional flow information with enhanced local texture micro patterns. As it captures the spatial temporal changes of facial movements through optical flow and enables us to observe both local and global structures, it shows its robustness in recognizing facial information. Finally, the POMF histogram is used to train the expression model through the hidden Markov model (HMM). To train through the HMM, the objective sequences are produced by the generation of a codebook using the K-means clustering technique. The performance of the proposed method has been evaluated over the RGB and depth camera-based video. Experimental results demonstrate that the proposed POMF descriptor is more robust in extracting facial information and provides a higher classification rate than other existing promising methods.

Thermo-physiological comfort properties of double-face knitted fabrics made from different types of polyester yarns and cotton yarn

Double-face knitted fabrics with hydrophobic inner and hydrophilic outer layers are characterised by their advantageous thermo-physiological comfort property that facilitates the transport of sweat from skin to outer fabric layer where it can be evaporated easily. In this study, for the production of double-face knitted fabrics, cotton yarn as hydrophilic yarn type and five different polyester filament yarns consisting of standard polyester, hollow polyester, micro polyester, textured polyester and textured micro polyester as hydrophobic yarn type were used. In order to determine the thermo-physiological comfort properties of the fabrics, air permeability, water vapour permeability, thermal conductivity, thermal resistance and overall moisture management capacity were measured. The results were comparatively analysed using statistical methods. The experimental results demonstrated that the polyester-type yarns and the combinations of them with the cotton yarn in fabric layers affected the thermo-physiological comfort properties significantly. The fabrics with polyester-type inner face and cotton outer face showed the best moisture transmission properties.

Versatile strategies for improving the performance of diamond wire sawn mc-Si solar cells

Unlike conventional multi-wire sawn (CMWS) multi-crystalline silicon (mc-Si) wafers, diamond wire sawn (DWS) mc-Si wafers textured by conventional acidic solution of HF/HNO3 are not suitable for solar cells because visible saw marks set significant barriers in both cell performance and surface appearance. In this work, we have employed versatile strategies based on metal-assisted chemical etching (MACE) technique to eliminate the saw marks and realize effective surface textures on DWS mc-Si wafers, including nano-texture (N-T), micro-texture (M-T) and nano/micro-texture (N/M-T). Especially, benefiting from the tradeoff between optical gain and electrical loss, the efficiency of 18.45% for N/M-T based DWS mc-Si solar cells with a standard wafer size of 156×156mm2 is reported to be higher by an absolute 0.57% compared with that of CMWS mc-Si solar cells (17.88%). Our work provides ways of fabricating DWS mc-Si solar cells with high efficiencies and satisfactory visual appearance.

Oxidative Nanopatterning of Titanium Surface Influences mRNA and MicroRNA Expression in Human Alveolar Bone Osteoblastic Cells.

Titanium implants have been extensively used in orthopedic and dental applications. It is well known that micro- and nanoscale surface features of biomaterials affect cellular events that control implant-host tissue interactions. To improve our understanding of how multiscale surface features affect cell behavior, we used microarrays to evaluate the transcriptional profile of osteoblastic cells from human alveolar bone cultured on engineered titanium surfaces, exhibiting the following topographies: nanotexture (N), nano+submicrotexture (NS), and rough microtexture (MR), obtained by modulating experimental parameters (temperature and solution composition) of a simple yet efficient chemical treatment with a H2SO4/H2O2 solution. Biochemical assays showed that cell culture proliferation augmented after 10 days, and cell viability increased gradually over 14 days. Among the treated surfaces, we observed an increase of alkaline phosphatase activity as a function of the surface texture, with higher activity shown by cells adhering onto nanotextured surfaces. Nevertheless, the rough microtexture group showed higher amounts of calcium than nanotextured group. Microarray data showed differential expression of 716 mRNAs and 32 microRNAs with functions associated with osteogenesis. Results suggest that oxidative nanopatterning of titanium surfaces induces changes in the metabolism of osteoblastic cells and contribute to the explanation of the mechanisms that control cell responses to micro- and nanoengineered surfaces.

Color image retrieval using statistical model and radial basis function neural network

This paper proposes a new and effective framework for color image retrieval based on Full Range Autoregressive Model (FRAR). Bayesian approach (BA) is used to estimate the parameters of the FRAR model. The color autocorrelogram, a new version of edge histogram descriptor (EHD) and micro-texture (MT) features are extracted using a common framework based on the FRAR model with BA. The extracted features are combined to form a feature vector, which is normalized and stored in image feature vector database. The feature vector database is categorized according to the nature of the images using the radial basis function neural network (RBFNN) and k-means clustering algorithm. The proposed system adopted Manhattan distance measure of order one to measure the similarity between the query and target images in the categorized and indexed feature vector database. The query refinement approach of short-term learning based relevance feedback mechanism is adopted to reduce the semantic gap. The experimental results, based on precision and recall method are reported. It demonstrates the performance of the improved EHD, effectiveness and efficiency achieved by the proposed framework.

False-positive reduction in mammography using multiscale spatial Weber law descriptor and support vector machines.

In a CAD system for the detection of masses, segmentation of mammograms yields regions of interest (ROIs), which are not only true masses but also suspicious normal tissues that result in false positives. We introduce a new method for false-positive reduction in this paper. The key idea of our approach is to exploit the textural properties of mammograms and for texture description, to use Weber law descriptor (WLD), which outperforms state-of-the-art best texture descriptors. The basic WLD is a holistic descriptor by its construction because it integrates the local information content into a single histogram, which does not take into account the spatial locality of micropatterns. We extend it into a multiscale spatial WLD (MSWLD) that better characterizes the texture micro structures of masses by incorporating the spatial locality and scale of microstructures. The dimension of the feature space generated by MSWLD becomes high; it is reduced by selecting features based on their significance. Finally, support vector machines are employed to classify ROIs as true masses or normal parenchyma. The proposed approach is evaluated using 1024 ROIs taken from digital database for screening mammography and an accuracy of Az = 0.99 ± 0.003 (area under receiver operating characteristic curve) is obtained. A comparison reveals that the proposed method has significant improvement over the state-of-the-art best methods for false-positive reduction problem.

Effects of manufacturing errors on tribological characteristics of 3-D textured micro- thrust bearings

The performance sensitivity of textured micro- thrust bearings to manufacturing errors is investigated by means of Navier–Stokes Computational Fluid Dynamics simulations, for incompressible isothermal flow. Bearings of optimized geometry are modelled as three-dimensional micro-channels, consisting of a smooth moving wall, and a stationary wall exhibiting periodic rectangular dimples. Discrepancies in the size and shape of the texture geometry, as well as macroscopic errors in the stationary surface (concavity/convexity and waviness) are considered and parametrically modelled. The effects of manufacturing errors on the bearing load carrying capacity and friction coefficient are analyzed, for representative width-to-length bearing ratios. In a number of cases, manufacturing errors result in improved performance of textured micro- thrust bearings.