Form Of Material Removal Research Articles

Atomic surface achieved through a novel cross-scale model from macroscale to nanoscale.

Chemical mechanical polishing (CMP) is widely used to achieve an atomic surface globally, yet its cross-scale polishing mechanisms are elusive. Moreover, traditional CMP normally employs toxic and corrosive slurries, resulting in potential pollution to the environment. To overcome these challenges, a novel cross-scale model from the millimeter to nanometer scale is proposed, which was confirmed by a newly developed green CMP process. The developed CMP slurry consisted of hydrogen peroxide, sodium carbonate, sodium hydroxycellulose, and silica. Prior to CMP, fused silica was polished by a ceria slurry. After CMP, the surface roughness (Sa) was 0.126 nm, the material-removal rate was 88.3 nm min-1, and the thickness of the damaged layer was 8.8 nm. The proposed model was built by fibers, through integrating Eulerian and Lagrangian models and reactive force field-molecular dynamics. The results predicted by the model were in good agreement with those of CMP experimentally. A model for large-sized fibers revealed that a direct contact area of 11.12% was obtained for a non-woven polishing pad during the CMP experiments. Another model constructed via combining Eulerian and Lagrangian functions showed that the stress at the intersections of the fibers varied mainly from 0.1 to 0.01 MPa and was higher than the stress at other parts. An increase in viscosity led to a decrease in the areas with low stress, demonstrating that viscosity enhanced the stress and facilitated the removal of material. At the microscale and nanoscale, the stress of the abrasive surface exposed to the workpiece changed from 2.21 to 6.43 GPa. Stress at the interface contributed to the formation of bridging bonds, further promoting the removal of material. With increasing the compressive stress, the material-removal form was transformed from a single atom to molecular chains. The proposed model and developed green CMP offer new insights to understand the cross-scale polishing mechanism, as well as for designing and manufacturing novel polishing slurries, pads, and setups.

Force Prediction and Material Removal Mechanism Analysis of Milling SiCp/2009Al.

In recent years, medium- and low-volume fraction silicon carbide particle-reinforced aluminum matrix composites (SiCp/Al) have increasingly become a key material in the aerospace industry. Force prediction and material removal mechanism analysis of milling SiCp/Al are necessary to improve the surface integrity of products. An orthogonal experiment of SiCp/2009Al with a volume fraction of 20% was carried out, and the effect of the milling parameters on milling force was studied with the input parameters of milling speed, feed rate, and milling depth. Thereby, the empirical force model of milling SiCp/2009Al is established by fitting the experiential data based on the multiple linear regression analysis methods. Moreover, the effects of the milling parameters on the force were analyzed. Finally, the material removal mechanism of milling SiCp/Al is analyzed based on dislocation theory. The analyzed results reveal that the removal mechanism of the SiCp/Al composites includes plastic deformation of the aluminum matrix, cutting of particles, fragmentation, and deboning. Based on dislocation theory and maximum undeformed thickness theory, the effect of cutting parameters on the form of material removal was analyzed, which serves as a guide for selecting appropriate machining parameters to obtain improved machining quality of SiCp/Al composites.

Backside wear in total knee replacement: A new quantitative measurement method and a comparison of polished cobalt-chromium tibial trays with titanium tibial trays

Abstract

Parametric optimization of USM parameters by Taguchi and NSGA-II for the development of µ-channels on pure titanium

PurposeThis paper consolidates and presents the results of a work conducted to fabricate micro-channels on titanium grade-2 material by ultrasonic machining process (USM). In this research, the effects of important USM parameters, namely, kind of abrasives and its size, concentration of slurry, USM power rating and feed rate, have been probed on micro-channels quality for average surface roughness and process throughput in the form of material removal rate.Design/methodology/approachMultiple micro-channels on commercially pure titanium (i.e. Ti grade-2) have been fabricated in a single pass by employing micro-tool based USM process. Taguchi-based L18 (mixed level) OA has been selected for experimental design. Analysis of variance (ANOVA) study and regression modeling have also been done. Non-Dominated Sorting Genetic Algorithm (NSGA-II) has been used for process optimization to get optimum values of material removal rate (MRR) and surface roughness (SR).FindingsThe influence of important USM variables on SR and MRR have been investigated, and NSGA-II-based multi-response optimization has been done. The best surface roughness values obtained via NSGA-II solution for SiC and B4C are 0.354 µm and 1.303 µm, respectively. Scanned electron microscopic investigation proves the fabrication of micro-channels with smooth surfaces, and minimum burrs and other defects. The material removed from the surface was due to ductile fractures.Originality/valueMiniaturization is a modern trend these days to solve many precision, scientific and industrial problems. To manufacture precise micro-products, shapes and features, advanced and micro-machining processes can play a very prominent role. Micro-channels are typical micro-features required in micro-fluidic applications like micro heat exchangers and micro-pumps. Exhaustive review of existing research work indicated that precision micromachining of various materials can be effectively performed using USM, though not much work has been undertaken to explore the feasibility of multiple micro-channels in a single run using USM. The current work fulfills the gap, where multiple micro-channels on commercially pure titanium (i.e. Ti grade-2) have been fabricated in a single pass by employing micro-tool-based USM process.

Research on the Single Grit Scratching Process of Oxygen-Free Copper (OFC).

Single grit scratching is a basic form of material removal for many processes, such as grinding single point diamond turning and coating bonding performance tests. It has been widely used in the study of micro-scale and nano-scale material removal mechanisms. In this study, single grit linearly loading scratching tests were carried out on a scratching tester. A Rockwell indenter made of natural diamond was selected as the tool used, and the material of the workpiece was oxygen-free copper. Scratch topography was measured using a super-depth microscope to analyze the material deformation of the scratching process. A single grit scratching simulation has been developed by AdvantEdge™ to comprehensively study the material deformation of scratching processes. A material constitutive model and friction model were acquired using a quasi-static uniaxial compression experiment and a reciprocating friction test, respectively. These two models were used as the input models in the finite simulations. The simulated scratching forces aligned well with the experimental scratching forces, which verified the precision of the simulation model. Since only the scratching force could be obtained in the scratching experiment, the plastic strain, material flow, and residual stress of the scratching were further analyzed using simulations. The results showed that the plastic strain of the workpiece increased with the increase in scratching depth, and further analysis showed that the workpiece surface was distributed with residual compressive stress and the sub-surface was distributed with residual tensile stress in single grit scratching.

Viscous liquid expulsion in nanosecond UV laser ablation: From “clean” ablation to nanostructures

This paper reviews recent results on modeling UV nanosecond laser ablation. Particular attention is given to a viscous liquid flow driven by ablation pressure. Based on the analysis of the Navier-Stokes equation, various strongly different manifestations of this phenomenon are explained. These are (i) a “clean” laser ablation, when the laser spot has a clean sharp spot border free of resolidified melt dross; (ii) a new form of material removal in laser ablation, expulsion on a poly(methyl methacrylate) target of long (up to 1 mm) nanofibers with a radius about 150–200 nm to the exterior of the spot under the action of a single pulse of a KrF excimer laser; and (iii) a new method of laser surface nanostructuring, the formation of a surface foam having a structure of micropores interconnected by nanofilaments with diameters of about 100 nm as a result of single-pulse KrF laser ablation of biopolymer films.

Viscous flow and ablation pressure phenomena in nanosecond UV laser irradiation of polymers

Acceleration and expulsion of a laser-induced melt layer in laser ablation of polymers is studied based on a combination of a quantitative theoretical modeling of ablation pressure and viscous melt flow with an experimental technique of a precise nanoscale measurement of the resulting surface profile. For two particular examples corresponding to so-called ‘stationary’ and ‘non-stationary’ liquid layer flows the following results are obtained: (i) the kinematic viscosity of the laser-induced melt layer on the surface of poly(ethylene terephthalate) at extreme conditions of KrF laser ablation is found for the first time and (ii) a new form of material removal in laser ablation is explained – expulsion of long (up to 1 mm) nanofibers with a radius of about 150–200 nm when a poly(methyl methacrylate) target is irradiated with a single pulse of a KrF excimer laser.

Millimeter long PMMA nanofibers—a new form of material removal in laser ablation

A new form of material removal in laser ablation is explained. Long (up to 1 mm) nanofibers with a radius approximately 150–200 nm are obtained when a polymethylmethacrylate (PMMA) target is irradiated with a single pulse of a KrF excimer laser. The model suggests an expulsion of energetic droplets by an intense pressure of the plume to the exterior of the spot. For the transient melt of a polymeric viscous liquid resulting from UV laser excitation, such droplets provide the heads of the jets pulled from the melt bath, giving rise, after re-solidification, to nanofibers. The initial speed of fiber spinning is extremely high (840 m/s, maximum velocity) and unusual properties of the laser-produced nanofibers may be expected.

Influence of microstructure on the erosion of plain carbon steels

The solid particle erosion behavior of plain carbon steels was examined as a function of carbon content and microstructure: this work included steels in the pearlitic, martensitic, and tempered conditions. The results showed that erosion by solid particles impacting at 30° is accelerated with an increasing volume of brittle cementite in pearlitic steels of constant interlamellar spacing. Under these erosion conditions, thermally hardened martensitic structures exhibited an increased erosion rate when compared to pearlitic steels of the same carbon content, whereas tempering resulted in a decrease in the rate of erosion. A good correlation exists among the hardness, deformability, and erosive wear characteristics of plain carbon steels for the experimental conditions of the present study. Ductile alloys exhibited lower erosion rates, severely deformed surfaces, and considerable subsurface plastic deformation. In the hardened or brittle condition, the steels experienced higher erosive weight losses, suggesting that more of the kinetic energy from impacting particles was dissipated, primarily in the form of material removal rather than plastic deformation. The microstructural mechanisms of erosion also are considered in terms of some current theories.