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Grinding performance improvement of laser micro-structured silicon nitride ceramics by laser macro-structured diamond wheels
摘要： Silicon nitride ceramics are widely used in various industrial ?elds because of their excellent characteristics: high hardness, high elastic modulus, abrasion resistance, and high heat resistance. Diamond wheel grinding is the predominant and most productive method to machine silicon nitride ceramics. However, a lot of heat is generated due to high friction between a diamond grinding wheel and extremely rigid silicon nitride during grinding. This causes surface/subsurface damage, wheel wear, etc., which impairs the surface quality of silicon nitride. This impairment can restrict the use of silicon nitride ceramic components. To improve the surface quality and service life of grinding wheels, a laser macro-micro combination structured grinding (LMMCSG) method was presented. The results indicated that the grinding force ratio and surface roughness when using LMMCSG were respectively 31% and 40% lower than the grinding force ratio and surface roughness when using conventional grinding. Moreover, the LMMCSG method e?ectively reduced the wheel wear and workpiece subsurface damage.
关键词： Macro–micro combination,Laser structured grinding,Wheel wear,Silicon nitride ceramic,Grinding force ratio,Surface roughness
更新于2025-09-11 14:15:04
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[Laser Institute of America ICALEO? 2015: 34th International Congress on Laser Materials Processing, Laser Microprocessing and Nanomanufacturing - Atlanta, Georgia, USA (October 18–22, 2015)] International Congress on Applications of Lasers & Electro-Optics - Laser powder deposition of WC particle reinforced metal matrix composites
摘要： Laser Powder Deposition (LPD) is an additive layered manufacturing process that can deposit near-net shape parts directly from metal powder. Metal Matrix Composites (MMCs) combine the merits of ductile metal matrix and hard ceramic reinforcement, providing enhanced properties including hardness and wear resistance. MMCs can be easily implemented in LPD process via blending the powders during deposition of coatings and 3-D parts. However, cracks induced by thermal stress and material embrittlement limit the application of MMCs in direct LPD processes. This study experimentally investigated the mechanical properties of MMCs deposited via LPD. Hardfacing alloy Stellite 6 and ductile alloy Inconel 718 were chosen as the matrix material, respectively, with spherical Tungsten carbide (WC) particles as the reinforcement. According to the experiment results, Inconel 718 was found to be a better choice for matrix material as it presented better compatibility with WC particles with acceptable wear resistance. Influence of direct age heat treatment of Inconel 718 matrix on mechanical properties was also investigated. Tensile tests showed that addition of WC particles in the matrix reduces both the ultimate strength and elongation. Microstructural observation of the tensile specimens indicated that WC particles are the preferable crack initiation sites, which significantly reduces the load-carrying capacity and ductility of the composite. Dissolution of WC into the matrix, which embrittles the matrix and further reduces the ductility of the composite, was proven by micro-hardness test and elemental analysis. Last, dry sliding test is conducted to evaluate the wear resistance of the MMCs. It was found that a small addition of WC particles can significantly increase the wear resistance.
关键词： Inconel 718,wear resistance,Laser Powder Deposition,Stellite 6,WC particles,Metal Matrix Composites
更新于2025-09-11 14:15:04
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Performance evaluation and multi-response optimization of grinding-aided electrochemical discharge drilling (G-ECDD) of borosilicate glass
摘要： Machining of advanced glass ceramics is of great importance and is a challenging task for the modern industries. In this study, a new hybrid technique of grinding-aided electrochemical discharge drilling (G-ECDD) is attempted which combines the grinding action of a rotating abrasive tool and thermal melting action of electrochemical discharges to perform drilling of borosilicate glass. G-ECDD is performed using a normal electrochemical discharge machine set-up with a provision for using a rotating diamond-coated drill tool. The tool used is a hollow diamond core drill rather than the traditional solid abrasive tool. A spring-fed tool system was designed and developed to provide the tool-feed movement which will also help to maintain a balance between grinding action of diamond grits and thermal melting action of discharges. Preliminary experiments are conducted to identify the optimum spring force of the spring-fed system and tool rotational speed which can facilitate a balanced ECDM and grinding action for material removal. The effect of machining parameters like voltage, duty ratio, pulse cycle time and electrolyte concentration on material removal rate (MRR) and hole radial overcut (ROC) is investigated using response surface methodology (RSM). Duty ratio and voltage are found to be the most significant factors contributing MRR. Voltage and pulse cycle time are identified as the main factors controlling radial overcut of the drilled holes. Second-order regression models for MRR and ROC are developed using the data collected from the experiments using RSM. Grey relational analysis was used to optimize this multi-objective problem. A voltage of 90 V, duty ratio of 0.7, cycle time of 0.002 s and an electrolyte concentration of 3.5 M are found to be the best combination for optimizing the responses. Deterioration of bonding material and dislodging of diamond grits are found to be the major modes of tool wear during G-ECDD. The use of high-frequency pulsed DC increased the tool wear rate due to the less time available for heat dissipation between discharge cycles. Moreover, the wear at the end face of the tool will be accelerated due to the concentration of current density at edges during high-frequency operation. From the microscopic images of the machined surface, the material removal mechanisms involved in G-ECDD are found to be a combination of thermal melting by discharges, grinding action of diamond grits and high-temperature chemical etching effect of the electrolyte.
关键词： Electrochemical discharge machining,Response surface methodology,Tool wear,Radial overcut,Grey relational analysis,Material removal rate,Material removal mechanism,Grinding
更新于2025-09-11 14:15:04
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A green single-tube sample preparation method for wear metal determination in lubricating oil by microwave induced plasma with optical emission spectrometry
摘要： A straightforward and rapid single-tube sample pretreatment for wear metals determination in used lubricating oils was developed in this work as an alternative to the reference pretreatment method (ASTM). A D-optimal mixture design on a three-component solution was performed. The optimal composition for the proposed sample preparation emulsion was 2 % v/v of xylene, 9.5 % v/v of Triton?X-114 and 88.5 % v/v of H2O. The determination of 18 wear metals was carried out by microwave induced plasma with optical emission spectrometer (MIP OES), and the results of the two sample preparations - conventional and proposed- were statistically compared. Also, a certified standard “wear metals in used lubricating oils” for pretreatment validation was used. The developed method was as effective as the reference method indicated by ATSM, similar in speed and simplicity, but superior from the environmental and economic point of view. The proposed pretreatment allowed Ag, Al, Ba, Ca, Cd, Cr, Cu, K, Mg, Mn, Mo, Ni, Pb, Si, Sn, Ti, V and Zn determination, with LOQ between 1.40 mg kg-1 for Ca and 6.34 mg kg-1 for Pb. The precisions established as the relative standard deviation (RSD) were better than 6.2%. The proposed method avoid sample handling, reducing contamination risks and analyte losses, affording significantly improvement on wear metal quantification.
关键词： Microwave induced plasma atomic emission spectrometry,Mixture experimental design,Wear metals,Green single-tube sample preparation,Used lubricating oils
更新于2025-09-11 14:15:04
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A novel algorithm for tool wear online inspection based on machine vision
摘要： To inspect the tool wear condition in the process of numerical control (NC) machining for difficult-to-cut material, an online inspection system for tool wear is developed based on machine vision. With the help of MATLAB software, a self-matching algorithm is proposed according to the characteristics of tool wear images. The corresponding user-friendly graphical user interface (GUI) of the algorithm is developed. The bottom edges are separated by the adaptive connecting domain labeling to analyze wear condition of each edge. Then, each edge is arranged regularly by the improved rotatory positioning. The cutting edge is extracted by the method of partial angle threshold to fit and calculate the bottom wear value. It is shown that the absolute values of errors on the maximum wear width are less than 0.007 mm by using the self-matching algorithm. In the case of severe wear and breakage, the absolute values of errors on the maximum wear width are less than 0.057 mm because of uneven reflected light. The system features high response speed, high inspecting accuracy, and anti-noise performance. It is proved to be able to increase the utilization of cutting tools and guarantee the quality of workpiece. This method is potential to guarantee the reliability of cutting tool in aerospace manufacturing.
关键词： Image processing,Tool wear,Machine vision,Self-matching algorithm,Online inspection
更新于2025-09-10 09:29:36
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The Effects of Heat Treatment on Microstructure and Mechanical Properties of Tribaloy 400 Coatings Deposited by Laser Cladding
摘要： The effects of heat treatment on the microstructure, microhardness, nanohardness and wear resistance of Tribaloy 400 coatings prepared by laser cladding on 304 stainless steel were studied in this paper. The results show that the microstructures of Tribaloy 400 laser cladding layer are cobalt matrix dendrites and eutectic structure. After the heat treatment at 1250 °C for 1 h, the eutectic structure disappears and the strip-like Laves phase is formed on the Co matrix. Meanwhile, the hardness is obviously improved. After the heat treatment at 1250 °C for 1 h and then 900 °C for 4 h, a small amount of e-Co appears, the strip-like Laves phases become coarser and blunter, and some of the strip structures combine together to form blocky structures, and the hardness is decreased. The wear resistance of the samples at 600 °C is better than that at RT since the hardness of the Laves phase increases with the rise in temperature.
关键词： Laves phase,wear resistance,hardness,heat treatment,Tribaloy alloy
更新于2025-09-10 09:29:36
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Corneal structure, transparency, thickness and optical density (densitometry), especially as relevant to contact lens wear—a review
摘要： Clinical instruments using Scheimpflug image-based methods to obtain optical sectional images of the cornea have been introduced in recent years along with proposals that it should be possible to routinely and reliably measure the optical density (referred to as the densitometry) of the human cornea in situ. Such a concept is reviewed from the perspective of what might be considered as the basic principles underlying the understanding of corneal transparency (from the 1950’s) and the progressive changes in these ideas from subjective slitlamp-based clinical observations from the late 1960’s, especially in contact lens wearers. Much more has been learned about the overall macrostructure (including corneal thickness) and the ultrastructure of the cornea from contemporary studies in the 1990’s, and these aspects of the cornea will be reviewed alongside consideration of the methods of assessing the optical characteristics of the cornea in the living eye. From these perspectives, in this review systematic consideration will be given to what objective (quantitative) output one of these Scheimpflug-based systems provides and how this information might be actually related to corneal transparency characteristics that might be observed clinically, particularly after long-term contact lens wear.
关键词： Corneal opacities,Corneal swelling,Contact lens wear,Corneal densitometry,Corneal oedema,Human,Corneal
更新于2025-09-10 09:29:36
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Laser cladding composite coating on mild steel using Ni–Cr–Ti–B <sub/>4</sub> C powder
摘要： The composite coating was fabricated by laser cladding on Q235 mild steel. The cross-section morphology, microstructure, phase, micro-hardness and wear resistance of the coating were investigated by scanning electron microscope, energy dispersive spectrometry, X-ray diffraction, Vickers micro-hardness tester and dry sliding wear testing machine, respectively. Results showed that composite coating was gained without cracks and bonded with substrate excellently because of the prominent metallurgical bonding. The composite coating was made up of Ni3Ti, Cr2Ti, Ni–Cr–Fe, TiB2 and TiC. Ceramic reinforcements existed in coating with eutectic and independent structures. The micro-hardness of coating was about 5 times the substrate. Compared with substrate, the coating showed superior wear resistance.
关键词： laser cladding,wear resistance,microstructure,Q235 mild steel,Composite coating
更新于2025-09-10 09:29:36
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Model of a Light Extinction Sensor for Assessing Wear Particle Distribution in a Lubricated Oil System
摘要： Light extinction based optical wear particle counters (OPCs) have been widely used in the industry for oil condition monitoring for several years, and while experiments have tested the benefits and drawbacks of the measurement principle, limited research has been conducted regarding a theoretical approach to evaluate opportunities and limitations of the measurement scheme. In this paper, we present a method for theoretically modelling the output of an OPC based on the light extinction principle in the regime of geometrical optics, with a special focus on the influence of sensor optical design, particle concentration and measurement noise. Moreover, we show that, if only signal amplitude is considered, an algorithm for evaluating sensor output can cause an erroneous assessment of particle contamination level.
关键词： optical particle counter,particle distribution,wear particle analysis,wear debris,oil condition monitoring,light extinction
更新于2025-09-09 09:28:46
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Investigation of reinforced performance of modified graphene oxide/high solid content polysiloxane nanocomposite coating films
摘要： Graphene oxide was modi?ed using long-chain silicone. The modi?ed graphene oxide (MGO) was obtained with a broader spacing of layers (1.45 nm) which means more bene?cial to polysiloxane entering into the laminates of MGO sheets. Then, MGO sheets were combined with polysiloxane which synthesized without any organic solvent to prepare nanocomposite coatings via cross-linking curing reaction. The solid content of polysiloxane can be reached up to 86%. Due to strong interfacial interaction and synergistic reinforcing between MGO sheets and polysiloxane, when blended with 1.00 wt% of MGO, the micro-hardness and elastic modulus of coating ?lms were increased by 57% and 24% comparing with pure polysiloxane coating ?lm, respectively. Subsequently, a 48% improvement of macro-scratch resistance can be achieved. Simultaneously, MGO/polysiloxane coating ?lm showed excellent wear resistance due to the unique two-dimensional geometry and low frictional coef?cient of MGO sheets at work in homogeneous dispersion system.
关键词： Polysiloxane,Scratch resistance,Wear resistance,Nanocomposite coatings,Graphene oxide
更新于2025-09-09 09:28:46