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Recovering waste metal without the need for remelting in solid-state recycling of metal chips can create green production. The overall process of solid-state recycling should be run at the lowest possible cost to remain competitive. High temperature and prolonged preheating time for billet's homogenization in hot extrusion to consolidate the chips conflicts with the aim of minimizing energy usage. Therefore, optimizing the effect of preheating temperature and time prior to hot extrusion is important. This study investigates the effects of preheating temperature and preheating time on the extrudates' quality. Milling chips of AA6061 were cold compacted and hot extruded through a flat-face die using preheating temperatures of 400, 500, and 550 °C for 1-6 h of preheating time. The mechanical and physical properties and microstructure of the extruded profiles were compared. The results revealed that higher acceptable strength and ductility were obtained at 500 °C with 2 h of preheating time. On top of that, temperature increase was the main criterion that results in the highest tensile strength; nevertheless, it was subjected to trade-off in ductility. The profile extruded at 500 and 550 °C had gained a close tensile strength. The study includes the prediction of the chip's welding quality through the damage evolution on the extrudate's structure. It was implemented with the help of DEFORMTM 3D finite element method (FEM) software, and the normalized Cockcroft and Latham (C & L) fracture criterion was chosen. The results of the simulations were compared and validated by the experimental results. [ABSTRACT FROM AUTHOR]

The demand for LCD (liquid crystal display) screens will maintain a rapid growth in the next decade. The high-speed edge-grinding process is important in this industry. One issue is the subsurface damage (SSD) induced by the edge-grinding. Glass is very sensitive to the micro-cracks of the processed surface. To investigate the SSD generated by the edge-grinding process, two grinding wheels with different grit sizes and bonding materials were employed to shape the edges of ultra-thin normal-glass panels and LCD-glass panels with 12 sets of grinding conditions. The cross-sectional microscopy, as a simple and direct assessment method, was utilized to measure the depths of subsurface cracks. It was found that bonding material, diamond concentration, and grit size imposed influences on the material removal mechanism of the edge-grinding process. The edge-grinding conducted using a wheel with grit size = 22-36 μm, diamond concentration = 100, and bonding material = resin induced little damage to the glass samples. With the smooth edge ground, the majority of the material was removed by plastic deformation. However, the subsurface damage of the LCD glass was smaller than that of the normal glass induced under the same grinding condition, and the LCD showed better machinability. The density of SSD of the LCD glass was also less than that of the normal glass. [ABSTRACT FROM AUTHOR]

Vibratory finishing has been widely used for surface polishing, burnishing, edge finishing, texturing, and cleaning with a wide variety of different media. Medium properties and their motions dominate material removal efficiency and surface treatment quality in the vibratory finishing process. In this study, medium kinematic model and movement simulation of vibratory finishing were developed. Medium motion simulation was verified through a digit video recorded by a high-speed camera. It was found that medium kinematic path line is a circular-feeding helical motion, which is determined by the angular velocity ratio between the rolling and feeding, the rotation direction, and vibratory finishing machine configuration. Material removal intensity model was further established based on the kinematic model in order to better understand the vibratory finishing process. The optimal fixing location and orientation of workpiece were obtained through the analysis of the kinematic model. Finishing experiments were further carried out for the Ti6Al4V test pieces which were fixed onto the wall of a vibratory bowl. The surface roughness, Ra values (with initial surface roughness of 1.50 μm), approached to 0.13 μm after processing time of 2.5 h and 0.10 μm after processing time of 6.0 h. Surface quality of finished test pieces has been significantly improved as compared with the existing method (i.e., loosed workpiece in the vibratory bowl), whereby the surface roughness, Ra values (with initial surface roughness of 1.50 μm), tapered off (saturated) to about 0.52 μm with the increase of processing time. [ABSTRACT FROM AUTHOR]

Fixed abrasive polishing has some advantages in generating good planarization surfaces with low defects. The surfaces after polishing have better uniformity, and the material removal rate is much higher than that of the traditional chemical mechanical polishing using loose abrasives. One of the most important factors that have significant effects on the uniformity of the polished surface is the pad wear profile. The pad wear profile after a long time of polishing is almost concave, and it has been challenging to create a flat surface. Therefore, there is a requirement for creating a better pad wear profile to improve quality of machined surfaces in chemical-mechanical polishing processes. In this paper, kinematic aspects of the effects of operation parameters on the pad wear profile are investigated, combining with conditioner sizes, pattern, and positions. Based on that, a new model, including new designs of the conditioner and pad, is proposed. This new model has created a convex pad wear profile instead of a concave one. According to the result of the new model, the pad shape after the conditioning process is more uniform than the old one conditioned by the old model. The result was validated by an algorithm which was validated by the experiments reported in our previous paper. [ABSTRACT FROM AUTHOR]

In the grinding of thin-walled and honeycomb-structured components made up of Hastelloy, undesired burrs are often created. The formed burrs negatively affect the quality of the products. Subsequent deburring increases overall manufacturing process time and cost. This work was focused on development of high-speed grinding process and grinding strategies to reduce burr size and improve ground surface quality. An electroplated Cubic Boron Nitride (CBN) wheel with miniature concave and convex asperities on its circumferential working surface was developed. Grinding performance with the designed CBN wheel was compared with a normal CBN wheel without surface asperities. Special fixtures with the function of adjusting honeycomb orientation (change of grinding direction) were purposely designed and fabricated. Design of experiment (DOE) was adopted for optimization of grinding parameters. It was found that less burr (even burr-free) grinding was achieved with the utilization of the specially designed CBN wheel with concave and convex asperities under optimal grinding conditions investigated, i.e., rotational speed of 5,000 RPM, depth of cut of 25 μm, and feed rate of 7,500 mm/min. [ABSTRACT FROM AUTHOR]

Fixed abrasive chemical-mechanical polishing (CMP) is an efficient surface finishing method. The non-uniformity of substrates after polishing is one of the most interesting things in current trends in research. One of the reasons for the non-uniformity is pad wear. The pad in this polishing process has abrasive grains embedded on the surface. Researching on the pad wear will help improve the pad conditioning process to get a better pad surface. Some studies have used kinematic motion to show the correlation between the cutting path density and the pad wear. However, the effect of contact time between the conditioner's grains and the pad surface on the pad wear non-uniformity has not been integrated yet. In this research, an analytical model was established by combining of the kinematic motions and the contact time to investigate the pad wear non-uniformity. The results indicated that the cutting path density and the contact time near the pad center are more than that near the pad edge. They could be the main reasons of the non-uniformity of the pad wear. The model results showed a good agreement with experiments. [ABSTRACT FROM AUTHOR]

Slurry plays an important role in the material removal of chemical mechanical polishing (CMP). However, the behavior of abrasive particles of the slurry in the interface between the wafer and the pad during CMP is not fully understood. In this paper, a new computational fluid dynamic (CFD) model was developed. It was a combination of multiphase and discrete phase modeling. The abrasive particles behavior and the slurry distribution in the interface were simulated using this model. The total numbers of particles in the gap were quantified to characterize their mechanical effects under different operating parameters. The simulation results showed that when the gap thickness increased and speeds of the wafer and the pad decreased, the total number of particles in the gap increased. It also found that the particles were non-uniformly distributed below the wafer. The results have the capacity of providing a deeper insight understanding of the material removal of the CMP mechanism. [ABSTRACT FROM AUTHOR]

Glass disk substrates are used in a wide range of portable devices because of their relatively high resistance to heat and shocks compared to aluminum substrates. Chemical mechanical polishing (CMP) with fixed abrasive pad is an alternative glass disk substrates finishing method to loose abrasive lapping and polishing with traditional pad. In this paper, we developed a chemical mechanical polishing process for 2.5-inch glass disk substrates using a fixed abrasive pad. A serial of CMP experiments were carried out under different polishing variables and conditioning modes (ex situ and in situ conditioning). The polishing performances were evaluated and analyzed in terms of surface roughness, surface topography, and material removal rate. The polishing characteristics were also discussed to reveal material removal mechanism and surface generation involved in fixed abrasive CMP for glass disk substrates. [ABSTRACT FROM AUTHOR]

Chemical mechanical polishing (CMP) experiments are performed to study the effects of four key process factors on the flatness and surface finish of the polished optical silicon substrates and on the material removal rate (MRR). The experimental results and analyses reveal that the pad rotational speed and polish pressure have significant effects on the MRR, the interaction of the polish head rotational speed and slurry supply velocity and the interaction of the polish pressure and polish head rotational speed have significant effects on the flatness, and the pad rotational speed has a significant effect on the surface roughness R of the optical silicon substrates polished. The optimal combination of the four factors investigated is a polish pressure of 9,800 Pa, a pad rotational speed of 20 rpm, a polish head rotational speed of 20 rpm, and a slurry supply velocity of 100 ml/min. A confirmation CMP experiment has been carried out using the optimal process parameter setting obtained from the design of experiments analyses. The goal to attain optical silicon substrates with nanometric surface roughness and micrometric flatness by an optimized CMP process with a high MRR simultaneously so as to reduce the polishing time to only 15 min from over 8 h has been achieved. [ABSTRACT FROM AUTHOR]

This paper proposes a new approach to predicting cutting forces in milling operations. The approach attempts to find the analytic relationship between cutting forces and the tangential direction of the tool path when a tool moves along an analytical curve, i.e., a Pythagorean-hodograph curve that describes a group of analytic curves with special properties, in a milling operation. In conventional methods for the prediction of cutting forces in milling operations, cutting forces are estimated by considering such cutting parameters as feed rate, depth of cut, and tool geometry. However, the change in the moving direction of the cutter, which has a major effect on cutting forces, is often neglected by previous researchers. This work aims to establish the theoretical basis to show how cutting forces along a curve can be predicted. Two case studies are used to illustrate the proposed cutting force prediction strategy. [ABSTRACT FROM AUTHOR]

This article presents an approach based on wavelet correlation modelling for health state monitoring of fluid dynamic bearings in brushless DC motors. This approach involves two stages: (1) extracting of features from the motor-stator current signatures by analysing discrete wavelet transform coefficients; and (2) building of the simplest correlation model between the extracted features and the bearing wear using a multivariable regression technique. The correlation model can be used to detect and predict the bearing wear of brushless DC motors. Experiments were carried out using brushless DC motors with fluid dynamic bearings to verify the proficiency of this approach. Good agreement between the prediction result and the real motor health condition demonstrated the viability of the approach for bearing prognostic applications. The correlation equations obtained have acceptable detectability and accuracy based on a desired 95% level of confidence. [ABSTRACT FROM AUTHOR]

This article discusses the recent developments in grinding of advanced materials. Eighty-four journal papers published recently are briefly introduced. The topics are advances in grinding of brittle materials, grinding of silicon, dressing/truing of grinding wheels, grinding fluids, grinding of mirrors and vibration-assisted grinding, measuring/monitoring of grinding, optimization of grinding, modelling and simulation of grinding, and size effect. Ductile mode grinding of brittle materials has been and will continue to be an intensive research area because of its increasing industrial applications and academic demands for fundamental understanding of the ductile mode grinding mechanism. Highly precision manufacturing of silicon substrates faces more and more new challenges. Grinding of silicon continues to be a popular research topic. Using lasers to true and dress grinding wheels has attracted great research interest, because it has significant advantages over mechanical processes. Environmentally friendly grinding fluids are increasingly highly demanded. Vibration-assisted grinding is promising. Monitoring, modelling and optimization of grinding processes help to understand grinding mechanisms and achieve better grinding performance. The size effect is more prominent in grinding than turning and can be used for obtaining a controlled work-hardening surface layer with higher wear resistance and hardness. [ABSTRACT FROM AUTHOR]

This paper proposes a new machining strategy to realize better dimensional accuracy as well as surface finish. The strategy attempts to keep cutting force and the material removal rate approximately constant and force the tool to move along a so-called Pythagorean-hodograph curve, which is a group of analytic curves with special properties, in a milling operation. In conventional milling operations, a constant feed rate is frequently used. This would invariably lead to higher material removal rates in concave regions and lower material removal rates in convex regions, and affects dimensional accuracy. This work aims to establish the theoretical basis to show how the above-mentioned phenomenon can be predicted. Additionally, chattering is a well-known problem in machining. In this work, it is postulated that keeping certain machining conditions approximately constant would help in reducing chattering during machining. A numerical example is given to illustrate the proposed machining strategy. [ABSTRACT FROM AUTHOR]

In this study, an adaptive space mapping technique based on response of objective was suggested for solving practical engineering problems. Response surface methodology was engaged in approximation of objective and constraint functions based on coarser model. The fine simulation model is not only used for correction of the coarser simulation model and validation of final solution but also for applied construction of space mapping expression. Finally, genetic algorithm (GA) was used to optimize updated metamodel according to coarse model. The proposed method combines the space mapping technology based on response of coarse model and modification of design of experiment. It guarantees that metamodel based coarser model is stepwise updated in the right searching direction. For demonstrating practicability of developed method, it was applied for optimization of geometric parameters of addendum surface, blank holder force and drawbead restraining force in sheet forming problems. It was confirmed that the corresponding problem can be optimized successfully in remarkably short computing time by proposed optimization method. [ABSTRACT FROM AUTHOR]

Thermally sprayed WC-Co coatings on steel rods were machined by grinding and turning using diamond tools, and thermally sprayed Inconel 625 coatings on steel rods were machined by turning using various WC tools. Four of these samples were selected for surface characterization using a stylus roughness tester. The results show that precision-machined WC-Co and Inconel-625 surfaces can be identified as self-affine fractals in the stochastic sense within the correlation length. The root-mean-square roughness ( R q ) depends on the scale of cut-off length (=sampling length in this paper) as a power law. The R q of the machined WC-Co surface was found to be dependent on the scale of cut-off length rather than the scale of evaluation length. The roughness exponent is a very useful parameter and can be used to predict the roughness value of the surfaces at any scale length, if the scale is within the correlation length and provided that one such value of a scale is known. It may be suitable to compare surfaces using roughness exponents, even if different cut-off lengths or scanning scales are used in the measurements to obtain roughness exponents. [ABSTRACT FROM AUTHOR]

In this study, the prediction of surface roughness heights Ra and Rt of turned surfaces was carried out using neural networks with seven inputs, namely, tool insert grade, workpiece material, tool nose radius, rake angle, depth of cut, spindle rate, and feed rate. Coated carbide, polycrystalline and single crystal diamond inserts were used to conduct 304 turning experiments on a lathe, and surface roughness heights of the turned surfaces were measured. A systematic approach to obtain an optimal network was employed to consider the effects of network architecture and activation functions on the prediction accuracy of the neural network for this application. The reliability of the optimized neural network was further explored by predicting the roughness of surfaces turned on another lathe, and the results proved that the network was equally effective in predicting the Ra and Rt values of the surfaces machined on this lathe as well. [ABSTRACT FROM AUTHOR]

In this study, diamond turning of an aluminium-based metal matrix composite (MMC) reinforced with SiC particles was conducted with the assistance of ultrasonic vibrations. A simple and small size vibration device was designed to mount a piezoelectric transducer and a diamond insert onto a CNC machine. Turning experiments were carried out using a factorial design to investigate the effects of vibration and turning conditions on the surface finish of the turned MMC samples. The experimental results show that surface roughness of the MMC sample turned with ultrasonic vibrations is better than that of the MMC sample turned without ultrasonic vibrations. Turning with vibrations creates regular surface profiles along the turning and vibration direction, resulting in a light dispersion phenomenon, which is not reported in other articles. This phenomenon can only be observed when the pitch of the regular profiles is within a particular range. The pitch is determined by the cutting speed when the vibration frequency is fixed. [ABSTRACT FROM AUTHOR]

In this study, theoretical analysis and experiments were carried out to investigate the effects of avalanche-point deviation and the deviation between the calibration and test-flying heights during the glide head calibration in the glide height tests for manufacturing hard disks. To obtain accurate glide height test results and improve the reproducibility of the test, flying height control should be carried out by limiting the acceptable deviation range of the flying heights of the glide heads. When the avalanche-point deviation is zero, the test results using different calibrated rails (or heads) are the same when they are used to detect the same defect. To avoid wrong test results due to avalanche-point deviation, the test-flying height should be the same as the calibration flying height because the difference of the output voltages of any two rails (or heads) is zero in this case. If these two deviations cannot be eliminated completely, the calibration and test-flying heights should be carefully selected because the error still can be minimised depending on the selection of the flying heights. [ABSTRACT FROM AUTHOR]

An atomic force microscope (AFM) scanning moiré technique has been developed and verified in preparation for the measurement of deformations of single point diamond-turned surfaces. It is a non-destructive measurement method without introducing external reference and specimen gratings. This technique has also been successfully applied to measure thermal deformations of electronics packages without introducing an external reference grating. The principle of the formation of an AFM scanning moiré and strain measurement using this technique is explained in detail. Several important issues in its applications such as the measuring errors, scanning directions and selection of the number of scan lines are also discussed. [ABSTRACT FROM AUTHOR]

By applying ultrasonic vibration to a single-crystal diamond tool-tip, ductile machining of fused silica can be achieved even for 2 μm depth of cut. The increase in the critical depth of cut is significant and is a function of the ratio of vibration speed to cutting speed. Surface roughness Ra of 100 nm was obtained for up to 2 μm depth of cut. [ABSTRACT FROM AUTHOR]