High Rake Angle Research Articles

Neuro-fuzzy assessment of machined wood fibre–reinforced magnesium oxide composite

ABSTRACT High quality processing key to improving product quality and enterprise benefits. In this work, an adaptive network–based fuzzy inference system (ANFIS) was combined with milling experiments to understand the effects of tool geometry and milling parameters on the surface quality of wood fibre–reinforced magnesium oxide composite (WRMC). Specifically, changes in surface roughness (Ra) and damage of WRMC at different milling conditions were assessed using ANFIS and micro-analysis methods. Development of ANFIS models were confirmed to be reliable for predicting surface roughness. Changes in surface roughness at different milling conditions were determined, and the lowest surface roughness was obtained at the highest rake angle, highest cutting speed, and smallest milling depth. Furthermore, pitting-type damage irregularly distributed on the machined surface is attributed to the pulling out and debonding of wood fibres. Overall, high cutting speed, shallow cutting depth, and high rake angle is recommended for fine machining of WRMC where a smooth surface is desired. This study showcases how neuro-fuzzy models can be combined with conventional micro-analysis to optimize milling parameters for WRMC to minimize surface damage, and paves the way for future studies to optimize cutting tool life and energy consumption.

Numerical Analysis on Cavitation-noise and Fluid-structure Interaction of AU-Outline GAWN Series and B-Series Marine Propellers

Cavitation and cavitation-induced noise are harmful to both marine propellers and marine wildlife. Thus, it is required to reduce cavitation in marine propellers by developing the best design marine propellers. Moreover, proper material should be selected during the construction of marine propellers to withstand high-pressure loads. This paper presents an evaluation of the hydrodynamic characteristics such as cavitation and cavitation-induced noise of AU-outline GAWN series and B-series marine propellers at 0˚, 5˚, 10˚, and 15˚ rake angles using Computational Fluid Dynamics (CFD) analysis. Moreover, the study aims to find out the optimized propeller material among Nickel-Aluminum-Bronze (NAB), S2 glass, Aluminum 6061, and carbon fiber reinforced plastic (CFRP) materials. It is concluded that the lowest cavitation noises are 153.3 dB and 153.1 dB at a 10° rake angle for AU-outline GAWN series and B-Series marine propellers respectively. S2 glass is observed to be the optimum material at low rake angles, while CFRP is the optimum material at high rake angles compared to all other potential materials for both AU-outline GAWN series and B-series propellers.

Study of Cutting Power and Power Efficiency during Straight-Tooth Cylindrical Milling Process of Particle Boards.

The cutting power consumption of milling has direct influence on the economic benefits of manufacturing particle boards. The influence of the milling parameters on the cutting power were investigated in this study. Experiments and data analyses were conducted based on the response surface methodology. The results show that the input parameters had significant effects on the cutting power. The high rake angle reduced the cutting force. Thus, the cutting power decreased with the increase in the rake angle and the cutting energy consumption was also reduced. The cutting power increased with the rotation speed of the main shaft and the depth of milling induced the impact resistance between the milling tool and particle board and the material removal rate. The p-values of the created models and input parameters were less than 0.05, which meant they were significant for cutting power and power efficiency. The depth of milling was the most important factor, followed by the rotation speed of the main shaft and then the rake angle. Due to the high values of R2 of 0.9926 and 0.9946, the quadratic models were chosen for creating the relationship between the input parameters and response parameters. The predicted values of cutting power and power efficiency were close to the actual values, which meant the models could perform good predictions. To minimize the cutting power and maximize the power efficiency for the particle board, the optimized parameters obtained via the response surface methodology were 2°, 6991.7 rpm, 1.36 mm for rake angle, rotation speed of the main shaft and depth of milling, respectively. The model further predicted that the optimized parameters combination would achieve cutting power and power efficiency values of 52.4 W and 11.9%, respectively, with the desirability of 0.732. In this study, the influence of the input parameters on the cutting power and power efficiency are revealed and the created models were useful for selecting the milling parameters for particle boards, to reduce the cutting power.

A numerical approach for crack-induced damage in tungsten carbide cutting tools during machining

Cracking wear is one of the major phenomena that affect the lifetime of cutting tools. Delamination may be the last stage and the inevitable outcome of the propagation of cracks that may initiate anywhere in the coating or at the coating/substrate interface. To explore this phenomenon, the standard finite element analysis (FEA) FEM analysis was performed, in a first step, to calculate the energy necessary for crack deflection at the interface and penetration into the substrate. The numerical results showed that the cracks are more prone to deflect at the interface than penetrating into the substrate. This prediction was supported by microscopic observations. In a second step, a numerical model was developed based on the combination of the extended finite element method (XFEM) and the cohesive element method (CEM) formulations for different parameters in relation with machining performance improvements. The findings of the parametric study enabled to conclude that the low stiffness, large edge radius, large thickness and high rake angle of the coating protect the tool from cracking. In parallel, it was revealed that a substrate with lower rigidity results in the delay of the tool crack initiation.

RSM and MD—a roughness predictive model and simulation comparison of monocrystalline optical grade silicon

Silicon is a major material for manufacturing high-quality optical components, a process requiring silicon roughness to be below 8 nm. Lately, the popular choice for manufacturing these high-quality components has been the use of single-point diamond on ultra-high precision machines. Diamond properties such as clear grain structure, low coefficient of friction, and well-defined grain structure are well harnessed in this process. To achieve the demanded roughness level, there is a need for an appropriate choice of machining conditions which does not only ensure ductile regime machining but also form a good starting point for an improved prediction. The present study varied three well-known strong determinants of surface roughness, namely, rake angle, nose radius, and feed rate, as design input factors to facilitate Ra prediction. One important discovery made that constitutes the novelty of this research which to the best of our knowledge has not been reported before is that high negative rake angle reduces the negative influence of high feed rate on surface roughness. Simulation was carried out using MD and the result was compared with the experiment. High form accuracy with Ra values between 1.8 and 7 nm, close approximation of actual turning/prediction results, and the conformity of MD and experimental results attested to the success of the research.

Effect of Tool Rake Angle and Crystal Orientation on Ductile Mode Cutting of Hard/Brittle Materials

The effects of negative rake angles on the ductile mode cutting of soda glass and sapphire were studied. In addition, the machining mechanism was studied using a groove-cutting model based on the orthogonal cutting theory. It was found that the specific cutting forces in ductile mode cutting increase on both the soda glass specimen and on the sapphire specimen when the rake angle of the tool becomes negative. The difference between the experimental data and theoretical data of the specific cutting forces becomes large when the tool has a high rake angle on the negative side. This is attributed to effects of the roundness of the edge, the effects of the roundness of the nose, and the plowing mechanism, which causes plastic flow of the work material to both sides of the groove. The specific cutting force of sapphire depends on the cutting direction against the crystal orientation. The specific cutting force of sapphire depends on the cutting direction in terms of the crystal orientation. The anisotropy of the cutting force of sapphire also depends on the rake angle of the tool.

Simulation of machining of ductile polycrystalline aggregates using a remeshing framework

Simulating the cutting of soft, ductile polycrystalline aggregates like CP aluminum and annealed OFHC copper beyond the incipient stage is challenging because of the occurrence of extremely sinuous plastic flow, and the need to model microstructure, high interfacial friction, and transgranular failure. Here we present a general adaptive remeshing and mesh-to-mesh transfer scheme to simulate the cutting of such soft polycrystalline aggregates using a pseudograin model, with no restrictions on the friction, rake angle, or grain-size. Importantly, there is no need for a predefined separation line. The simulations successfully capture many experimentally observed aspects of the cutting of such ‘gummy’ metals, including sinuous flow, surface fold formation, thick mushroom-like type-I chips at low rake-angle, and thin, type-II chips with shear-plane like deformation at high rake-angle. The method also successfully replicates features like the formation of a stagnation zone ahead of the tool at high friction. Importantly, it permits accurate analysis of the cut surface, capturing the high strains, strain gradients, and deformed grain shapes in the wake of the tool. The presence of microstructure necessitates careful consideration of issues that do not arise in homogeneous remeshing simulations, including the need to model grain-splitting, grain-tracking, and mechanisms of material flow near the tool tip. The generality of the present approach makes it suitable to accurately model and simulate a wide range of machining processes.

Comparison of Flow Stress of Aluminum Alloy 6061-T6 Obtained From Chip Pulling Orthogonal Cutting and Kolsky Bar Testing

Machining can be used as a test for the flow stress of materials under conditions of high strain (ε > 1) and strain rate (102/s to 106/s). Constitutive models of metallic materials are conventionally obtained by dynamic compression tests such as the Split-Hopkinson (Kolsky) bar test at lower strain (ε < 0.3) and strain rate (103/s to 104/s). To compare the flow stress obtained from both tests under identical conditions, the strain in the primary shear zone (PSZ) in orthogonal cutting tests has been lowered using high rake angle (α = 45°) cutting tools to ε ≈ 0.8, and by adding chip pulling to ε ≈ 0.5. To our knowledge this is the first time that flow stress estimates are obtained from machining at such low strain values. With some modifications, the strain in Kolsky bar testing has been increased up to ε = 0.8, and the stress-strain curve obtained is compared to flow stress estimates from orthogonal cutting tests under the same strain and similar strain rates. The results work, show for the first time, that the flow stress measured from cutting tests agree closely with those obtained from Kolsky bar testing.

Molecular dynamic study of combined effects of diamond tool rake angle and d&lt;SUB align="right"&gt;uncut/R&lt;SUB align="right"&gt;edge ratio on nanomachining behaviour of monocrystalline optical silicon

Molecular dynamics (MD) of silicon ductility under contact loading due to the influence of edge radius, rake angle and undeformed (uncut) chip thickness to edge radius ratio was studied. The study showed that the stress state of silicon increased with increase in rake angle and decrease in undeformed chip thickness to edge radius ratio. Larger rake angle tool experienced stronger cutting resistance from the workpiece than the smaller rake angle, causing the specific cutting energy (SCE), cutting and thrust forces to increase. There was high kinetic friction at high undeformed chip thickness to edge radius ratio, reducing as the rake angle increases due to increase in thrust forces. The excessive negative effective rake angle at low undeformed chip thickness to edge radius ratio and high rake angle seems to be responsible for increase in phase change at the cutting region, decrease in chip length and thickness, increase in subsurface deformation.

Molecular dynamic study of combined effects of diamond tool rake angle and d&lt;SUB align="right"&gt;uncut/R&lt;SUB align="right"&gt;edge ratio on nanomachining behaviour of monocrystalline optical silicon

Molecular dynamics (MD) of silicon ductility under contact loading due to the influence of edge radius, rake angle and undeformed (uncut) chip thickness to edge radius ratio was studied. The study showed that the stress state of silicon increased with increase in rake angle and decrease in undeformed chip thickness to edge radius ratio. Larger rake angle tool experienced stronger cutting resistance from the workpiece than the smaller rake angle, causing the specific cutting energy (SCE), cutting and thrust forces to increase. There was high kinetic friction at high undeformed chip thickness to edge radius ratio, reducing as the rake angle increases due to increase in thrust forces. The excessive negative effective rake angle at low undeformed chip thickness to edge radius ratio and high rake angle seems to be responsible for increase in phase change at the cutting region, decrease in chip length and thickness, increase in subsurface deformation.

Experimental analysis of cutting edge effects on vibrations in end milling

The ability to minimize vibrations in milling by the selection of cutting edge geometry and appropriate cutting conditions is an important asset in the optimization of the cutting process. This paper presents a measurement method and a signal processing technique to characterize and quantify the magnitude of the vibrations in an end milling application. Developed methods are then used to investigate the effects of various cutting edge geometries on vibrations in end milling. The experiments are carried out with five cutting edge geometries that are frequently used in machining industry for a wide range of milling applications. The results show that a modest protection chamfer combined with a relatively high rake angle has, for the most of cutting conditions, a reducing effect on vibration magnitudes. Furthermore, dynamics of a highly positive versus a highly negative cutting geometry is explored in time domain and its dependency on cutting conditions is presented. The results give concrete indications about the most optimal cutting edge geometry and cutting conditions in terms of dynamic behavior of the tool.

Simulation of Sinuous Flow in Metal Cutting

Sinuous flow is a recently discovered mode of unsteady plastic flow in the cutting of metal involving large plastic strains, extensive material folding, and consequences ranging from paradoxically large cutting forces to poor surface finish. Here we use full-scale simulations to show how sinuous flow, and the concomitant redundant plastic deformation in cutting, are caused by microstructure-related inhomogeneity. The computations are carried out in a Lagrangian continuum mechanics framework using a simple, but effective, pseudograin model to represent metal as a polycrystalline aggregate. Our simulations successfully capture all experimentally observed aspects of sinuous flow in metals, including highly undulating, non-laminar streaklines of flow in the chip, folds, and mushroom-like features, and severely deformed high aspect ratio grains. The simulations also shed light on the mechanism of sinuous flow, and the effect of deformation geometry, explaining why it is suppressed at high rake angles. We find that folding and sinuous flow can occur even at low friction, for grain sizes as small as 25–50 microns, and at very low-cutting speeds. Our study clearly points at the critical importance of incorporating microstructure in cutting simulations of pure metals.

Reducing temperature elevation of robotic bone drilling

This research work aims at reducing temperature elevation of bone drilling. An extensive experimental study was conducted which focused on the investigation of three main measures to reduce the temperature elevation as used in industry: irrigation, interval drilling and drill bit designs. Different external irrigation rates (0 ml/min, 15 ml/min, 30 ml/min), continuously drilled interval lengths (2 mm, 1 mm, 0.5 mm) as well as two drill bit designs were tested. A custom single flute drill bit was designed with a higher rake angle and smaller chisel edge to generate less heat compared to a standard surgical drill bit. A new experimental setup was developed to measure drilling forces and torques as well as the 2D temperature field at any depth using a high resolution thermal camera. The results show that external irrigation is a main factor to reduce temperature elevation due not primarily to its effect on cooling but rather due to the prevention of drill bit clogging. During drilling, the build up of bone material in the drill bit flutes result in excessive temperatures due to an increase in thrust forces and torques. Drilling in intervals allows the removal of bone chips and cleaning of flutes when the drill bit is extracted as well as cooling of the bone in-between intervals which limits the accumulation of heat. However, reducing the length of the drilled interval was found only to be beneficial for temperature reduction using the newly designed drill bit due to the improved cutting geometry. To evaluate possible tissue damage caused by the generated heat increase, cumulative equivalent minutes (CEM43) were calculated and it was found that the combination of small interval length (0.5 mm), high irrigation rate (30 ml/min) and the newly designed drill bit was the only parameter combination which allowed drilling below the time-thermal threshold for tissue damage. In conclusion, an optimized drilling method has been found which might also enable drilling in more delicate procedures such as that performed during minimally invasive robotic cochlear implantation.

High Rake Angle Orthogonal Machining of Highly Ordered Pyrolytic Graphite Parallel to the Basal Plane

High rake angle orthogonal machining of highly ordered pyrolytic graphite (HOPG) parallel to the basal plane was carried out to synthesize few layers of graphene. The quality of the graphite sheets was found to be an alliance of any pre-existing defects in the HOPG and the nature of the machining process itself. Presence of pre-existing defects such as kinks and discontinuous layers were observed during the lateral examination of HOPG structure prior to machining. Evidence of flat, folded, and rolled structures were found in exfoliated graphite sheets in addition to defects such as two types of kink bands. Multiple spikes in measured cutting forces were seen during machining due to disturbances in tool movement. Molecular dynamic simulations were carried out to support the argument that specific pre-existing defects such as discontinuous layers cause the marked disturbances during machining.

Contributions of High-Speed Cutting and High Rake Angle to the Cutting Performance of Natural Rubber

This study investigates the contributions of high-speed cutting and a high rake angle to the improvement of the cutting performance of natural rubber. Orthogonal cutting experiments were conducted at cutting speeds ranging from 1.0 m/s to 141.1 m/s. The rake angles examined were 0°, 20° and 50°. The following results were obtained from the experiments. The cutting ratio is almost 1.0 regardless of the cutting speed and rake angle. The cutting force rises rapidly as the cutting speed increases. High-speed cutting or a high rake angle eliminates tear defects on the machined surface and reduces chipping defects at the entry edge of the workpiece. An uncut portion, however, always remains at the exit edge. The cross-sectional shape of the machined surface becomes concave. Besides, the machined surface comes into broad contact with the clearance face. These degradations in the shape accuracy arise from the large elastic distortion that occurs in the shear zone. Increasing the cutting speed improves the flatness of the machined surface. Although an analysis of the cutting mechanism reveals that the apparent stiffness of the material in the shear zone is enhanced with increasing the cutting speed, a very high cutting speed worsens the shape accuracy because of the development of shock waves. Depending on the rake angle, there is a critical cutting speed that should not be exceeded to maximize the cutting performance of natural rubber.

Soil translocation by narrow openers with various rake angles

Australian no-till farming often uses narrow point openers to open the soil and place seed and fertiliser in the furrow, in conjunction with spraying pre-emergence herbicides and using press-wheels to pack soil over seeds. At speeds above 6 km h −1 these openers can create excessive soil throw which creates problems for adjacent furrows, such as greater seeding depth and herbicide contamination, as well as increased weed germination and furrow seedbed moisture loss. This study evaluated the effect of 35°, 53°, 72° and 90° rake angles on the soil movement induced by a flat-faced narrow point opener operating at 120 mm depth and 8.2 km h −1 . Small cubic plastic tracers were used in a soil-bin environment to quantify soil movement by individual depth layer over the 0–120 mm range. Results of this study showed the large difference in action between low and high rake angle openers. A low rake angle opener was seen to move tracers placed deep in the soil up to the surface and to throw more soil and deeper soil out onto the furrow ridge. Conversely, a larger rake angle opener disturbed a smaller furrow size and achieved slightly more furrow backfill. The widest band within the furrow cleared of surface soil was achieved using the 53° rake angle. Lower rake angles increased the movement from deeper soil layers into the seed zone. These findings have implications for optimising no-till seeding practices such as deep moisture movement, pre-emergence herbicide incorporation and associated crop safety, as well as weed seed germination.

B23 粘弾性材の高速切削特性(OS6 切削加工(1))

High-speed cutting experiment of a natural rubber was carried out in order to clarify the characteristic of high-speed cutting of viscoelastic materials. Cutting speeds ranging from 1 m/s to 150 m/s were examined. The influence of the rake angle was also examined. The following findings were obtained. Large viscoelastic deformation ahead of the cutting edge degrades the geometrical accuracy of the machined surface regardless of the cutting speed and rake angel. Higher rake angle, however, diminishes the tear defects on the machined surface. Shear stress on the shear zone rises as the cutting speed increases. This is attributed to the increase of the viscous drag of a viscoelastic material.

Caracterização estrutural e petrológica do magmatismo pré-colisional do Escudo Sul-rio-grandense: os ortognaisses do Complexo Metamórfico Várzea do Capivarita

O Complexo Metamórfico Várzea do Capivarita situa-se na região de Encruzilhada do Sul, RS, e faz parte do Escudo Sul-rio-grandense (ESRG). Congrega rochas ortometamórficas de composição tonalítica, além de paragnaisses pelíticos e calciossilicáticos. Orto e paragnaisses são intercalados em fatias de 3 a 4m de espessura média e apresentam paragêneses e microestruturas compatíveis com metamorfismo de fácies granulito. A abordagem integrada de geologia de campo, geologia estrutural e petrografia permitiu discutir a história evolutiva do Complexo. Para a investigação dos ortognaisses foram obtidos também dados geoquímicos de elementos maiores e traços, o que tornou possível estabelecer as características do magmatismo gerador de seu protólito. As rochas do Complexo possuem bandamento de direção preferencial NNW e mergulho variável, para ENE e WSW, contendo lineação de estiramento geralmente de alta obliquidade. A atitude original do bandamento, retirados os efeitos de dobras, é interpretada como suborizontal. O empilhamento de sequências de composição e ambientes de formação distintos ao longo de estruturas originalmente suborizontais indica um regime tectônico do tipo cavalgamento, e o registro de paragêneses de alto grau orientadas segundo o bandamento em todos os tipos litológicos sugere que esta tectônica ocorreu em condições de fácies granulito. Os gnaisses tonalíticos são meta a peraluminosos e pertencem à série cálcio-alcalina. Sua composição e padrões de elementos traços sugerem que representam um magmatismo de arco continental, correlacionável ao Complexo Encantadas, uma associação de arco magmático paleoproterozóica do ESRG. Deste modo, os ortognaisses estudados, por sua similaridade composicional e estratigráfica com o Complexo Encantadas, são interpretados como parte do mesmo magmatismo de margem continental ativa. Presume-se que o metamorfismo de fácies granulito tem idade neoproterozóica e teria sido contemporâneo à tectônica de empurrão responsável por justapor litologias de idade e origem diversa, gerando o Complexo.

Study on Machining Characteristic of Aeronautical Material under Orthogonal Dry Cutting

From a series of experiments carried out in this study, the machining characteristic of aeronautical material, titanium alloy Ti6Al4V, under dry orthogonal cutting is determined by the relations among material removal rate (MRR), tool rake angle (), and the other nine parameters in orthogonal cutting concept. Continuous and serrated chip forms are observed and chip form is determined by the flow localization parameter (). It is found that the critical values of  in which serrated chip formed are ranging from  = 4.71 to  = 5.37 or at the chip load from 0.0045 to 0.006 mm2/min. The number of tooth (frequency) on serrated chip increases with cutting speed (V). The tool failure modes found in this study are normal flank wear, notch wear, chipping and catastrophic failure. Tool chip adhesion caused by adhesive wear mechanism and high rake angle weakened the tool cutting edge play important roles on the failure mode of the straight tungsten carbide cutting tool used in this study.

The influence of automobile windscreen rake on effective light transmittance

The theoretical transmittances at the installation angle of the windscreens of the ten best-selling cars in the UK in 2008 are investigated. The data show that the ten most popular cars on the UK roads have a windscreen rake that reduces transmittance to a value close to or below that specified in International Standards for normal incidence. British and International Standards for windscreen transmittance should be revisited by the relevant authorities in the light of the high rake angles that have become widespread in recent years. The problem is worsened considerably by tinted windscreens having become the default option in many models. It is also suggested that there may be good reason for all spectacles supplied to drivers for low light level driving to be untinted and anti-reflection coated.