Flat End Research Articles

Superequilibrium increase in the chemical reaction rate in the front and other effects of gas detonation numerically simulated in the channel by instant heating of the flat end

Gas detonation was calculated by the Monte Carlo method at the molecular level on the basis of non-stationary statistical simulation. The detonation was initiated by instant heating of the flat end of the channel. The efficiency of the method and the used block decomposition of the model space is shown. It turned out that an increase in the reaction threshold from 90kТ 1 to 400kТ 1 (k is the Boltzmann constant, and Т 1 is the initial temperature of the gas) resulted in the disappearance of the region of constant parameters behind the front of the detonation wave. The translational non-equilibrium formed in the detonation front strongly increases the rate of the reaction considered at the front edge. The further increase in the reaction threshold leads to the situation where no detonation occurs.

Experimental Study of Concrete Aging Effect on the Contact Force and Contact Time During the Impact Interaction of an Elastic Rod with a Viscoelastic Beam

AbstractIn the present paper, the low-velocity impact of an elastic rod with a flat end upon a viscoelastic Timoshenko type beam has been considered. Viscoelastic properties of the beam out of the contact zone are described by the standard linear solid model with integer derivatives, while inside this zone they are governed by the fractional derivative standard linear solid model. The contact force for a concrete target has been defined experimentally at the concrete age of 7, 14, 28, 56, and 91 days. It has been found that an average maximum of the contact force increases with concrete age, whereas the contact duration decreases. Moreover, the most remarkable changes of both, contact force and contact time, occur at the concrete age earlier than 14 days, after that the rate of changes slows down. Experimental results have a good coincidence with theoretical expectations.

Impact of udder and teat morphometry on udder health in Tharparkar cows under climatic condition of hot arid region of Thar Desert.

Prevention of subclinical mastitis (SCM) is an important tool for sustainable dairying and implementing higher production level in animals. The present investigation involved a total of 397 quarters of milk examination of 105 indigenous Tharparkar cows at Livestock Research Centre, Chandan located in the Jaisalmer district of Rajasthan in Thar Desert to study the impact of udder and teat morphometry on udder health. Udder health was examined by somatic cell count to check the status of subclinical mastitis while udder and teat morphometry of 90 udder and 386 quarters, i.e., udder shape and depth, teat end shape, teat length, and teat diameter were examined at individual animal level and quarter level. Data were collected from the record register maintained at the farm and data evaluated by parity (no. of lactation) and stage of lactation. On analysis of variance, result revealed the significantly (P < 0.05) higher incidence of SCM was for pendulous shape udder in respect of regular udder, as well as for inverted and flat teat end shape in respect of pointed teat end shape. Large teat length and upper depth animals had significantly (P < 0.05) more incidence of SCM as compared to small and medium teat length and udder depth group, respectively. Thick teat diameter group animals were significantly (P < 0.01) more prone to infection as compared to medium and thin teat diameter group animals. So, it can be concluded that selection for optimum udder and teat morphometry in breeding program may help to reduce susceptibility for intramammary infections in Tharparkar cows. Microbiological study of milk samples could be helpful in the nearby future for identification of subclinical mastitis.

Optimisation of tool path for wood machining on CNC machines

Peripheral pocket or contour milling in wood machining, using flat end milling tool, can be performed with different tool paths. Technology designers of multi axis CNC wood machining use their experience and intuition to choose some of the options offered by CAM systems that determine the final shape of tool path, thus the generated tool path largely depend on individual judgment. Minimum cutting force, maximum dynamic stability of the process and minimum tool wear are achieved, or some other technological requirements are met, by using optimal tool path. Tool path optimisation is based on analysis of possible tool paths and determination of cutting parameters which are dependable of chosen tool path and are affecting the main wood processing factors. Axial and radial depth of cut, engagement angle, feed and feed rate profile are identified as key parameters dependable of tool path, and their values and variations along the tool path influence the cutting speed, tool wear and cutting force. Knowledge of values and changes of those key machining parameters along the tool path is necessary for simulation and monitoring of the main cutting factors during the wood machining process. NC code transformation methodology and generation of tool path parameters necessary for calculating all elements needed for tool movement simulation from given NC programs are shown. Blank and tool mathematical description are used with tool movement information for simulation of wood machining process. Simulation of cutting parameters and their variation along the tool path, presented in this paper, can be used as bases for development of methodology for choosing the most adequate tool path for wood machining of given contour considering minimum cutting force and cutting force variation, minimum tool wear, maximum productivity or some other criteria.

Spectrum of the Dirac operator on manifold with asymptotically flat end

The spectrum of the Dirac operator is investigated on a Riemannian manifold one of whose end is asymptotically flat in some sense. It is proved that there is no non-zero eigenvalue and the essential spectrum is equal to R .

Finite element modeling for the cutting process of the titanium alloy Ti10V2Fe3Al

By producing of critical components in the aerospace industry is widely used the β-titanium alloy Ti10V2Fe3Al (Ti-1023) due to its extremely high ratio of strength to density, its great resistance to fatigue, its excellent resistance to corrosion and fracture toughness. This material is characterized by significant difficulties in machining. Substantial assistance in the study of the titanium alloy Ti-1023 machinability can provide a simulation of machining by numerical modeling. This paper presents the results regarding the creation of the FEM models for the cutting processes of the titanium alloy Ti-1023. The created FEM cutting models were constantly verified with experimental tests of the kinetic machining characteristics and analyses of the chip morphology by orthogonal and oblique cutting as well as flat end milling with different depths of immersion. A Johnson–Cook model was used as material model of the workpiece and the damage mechanism of the workpiece is reproduced with the Cocroft and Latham model. The parameters of material and fracture model were determined by DOE study. Comparing the experimentally established and the simulated kinetic machining characteristics and chip morphology confirms that the created FEM models are of a good quality. The size of error for simulating the chip dimensions does not exceed 10 % and ranges between 10 and 30 % for simulating the resultant forces.

Built-up-edge effects on surface deterioration in micromilling processes

Built-up edge (BUE) has been noted as a major cause for surface finish deterioration in micromachining processes—even a trace formation of hardened and brittle structure on the tool edge alters the chip load, creates ad hoc and irregular material flow patterns, and results in deposits and smeared regions on the machined surface. To date, few investigations have addressed the formation and effects of BUE in micromachining. This paper is one of the first experimental investigations of the BUE effects on surface quality and its prediction in micromachining. Experiments were conducted on a Haas OM2 CNC milling system with air bearing spindle. The experiments consisted of micromilling 12mm long thin channels on 316L stainless steel plates (30mm×40mm×0.5mm) using uncoated tungsten carbide micromills (from Performance Micro Tools with flat end and Φ0.406mm diameter) at 16 different settings of carefully selected combination of cutting speed and chip load with minimum quantity lubrication (MQL). The surface morphology including BUE distribution, as well as BUE formation on tool surfaces were studied ex situ via optical and scanning electron microscopy. We introduce two metrics to quantify the severity of BUE, namely, BUE density and its distribution entropy. These metrics capture, respectively, the extent and dispersion of BUE on the surface. We also conducted empirical studies to assess the extent to which these quantifiers can determine the variation in surface finish (Sa). Results suggest that the BUE is the major determinant of surface finish besides the chip load effect in micromachining. Statistical Granger-causality tests suggest also that estimation of the BUE density can help with improving the accuracy (R2) of surface finish Sa prediction from a negative value (poor fit) with conventional model to 0.4, i.e., 40% of Sa variation in the micromachining experiments can be attributed to the BUE effect.

Modeling and optimization of CNC milling of AISI 1050 steel by a regression based differential evolution algorithm (DEA)

Abstract The present study is aimed at finding an optimization strategy for the CNC pocket milling process based on regression analysis including differential evolution algorithm (DEA). Milling parameters such as cutting speed, feed rate and depth of cut have been designed using rotatable central composite design (CCD). The AISI 1050 medium carbon steel has been machined by a high speed steel (HSS) flat end cutter tool with 8 mm diameter using the zig-zag cutting path strategy under air flow condition. The influence of milling parameters has been examined. The model for the surface roughness, as a function of milling parameters, has been obtained using the response surface methodology (RSM). Also, the power and adequacy of the quadratic mathematical model have been proved by analysis of variance (ANOVA) method. Finally, the process design parameters have been optimized based on surface roughness using bio-inspired optimization algorithm, called differential evolution algorithm (DEA). The enhanced method proposed in this study can be readily applied to different metal cutting processes with greater and faster reliability.

Mechanistic Modeling of Five-Axis Machining With a Flat End Mill Considering Bottom Edge Cutting Effect

In five-axis milling, the bottom edge of a flat end mill is probably involved in cutting when the lead angle of tool axis changes to negative. The mechanistic model will lose accuracy if the bottom edge cutting effect is neglected. In this paper, an improved mechanistic model of five-axis machining with a flat end mill is presented to accurately predict cutting forces by combining the cutting effects of both side and bottom edges. Based on the kinematic analysis of the radial line located at the tool bottom part, the feasible contact radial line (FCRL) is analytically extracted. Then, boundaries of the bottom cutter-workpiece engagements (CWEs) are obtained by intersecting the FCRL with workpiece surfaces and identifying the inclusion relation of its endpoints with the workpiece volume. Next, an analytical method is proposed to calculate the cutting width and the chip area by considering five-axis motions of the tool. Finally, the method of calibrating bottom-cutting force coefficients by conducting a series of plunge milling tests at various feedrates is proposed, and the improved mechanistic model is then applied to predict cutting forces. The five-axis milling with a negative lead angle and the rough machining of an aircraft engine blisk are carried out to test the effectiveness and practicability of the proposed model. The results indicate that it is essential to take into account the bottom edge cutting effect for accurate prediction of cutting forces at tool path zones where the tool bottom part engages with the workpiece.

탄소섬유복합재 3축 밀링 알고리즘 개발

The simulation of Carbon fiber reinforced polymer (CFRP) machining facilitates the selection of optimal cutting parameter for high machining efficiency and better surface quality. In this study, This paper proposes a dual-dexel model to represent the fiber laminate with computational geometry method to calculate the fiber length removed per revolution and fiber cutting angles. A flat end milling simulation software is developed in C# to simulate and display the CFRP milling process. During simulation, fiber lengths, fiber cutting angle and engaged cutting angle can be displayed in real-time. A CFRP plate with different angles in different layer is used to compare the simulation results.

Hybridization effects on quasi-static penetration resistance in fiber reinforced hybrid composite laminates

Abstract Quasi static penetration tests (QSPT) were conducted on fiber reinforced hybrid composite laminates with a circular and cylindrical punch. Woven Carbon, Kevlar and S-glass fibers were used as reinforcing fibers for production of hybrid and non-hybrid composite laminates. Punch shear test procedures were employed until the perforation and complete plugging shear out of the laminate. During QSPT experiments, a flat end punch with diameter of 12.7 mm has been used for two different support spans (25.4 and 63.5 mm) to obtain two different support span (D s ) to punch diameter (D p ) ratios (SPR = D s /D p = 2 and 5). After the experiments, the extent of compression-shear and tension-shear based failure modes were characterized at constant punch displacements of 8 and 10 mm for SPR = 2 and 5, respectively. In addition to visualize of front and back side surfaces, composite samples were half sectioned at damage region to observe the amount of delamination and damage through the thickness of the laminate. It was found that hybridization effects were distinctly observed with dominated tension-shear damage mode at SPR = 5.

Extremal black hole initial data deformations

We study deformations of axially symmetric initial data for Einstein–Maxwell equations satisfying time-rotation (t–ϕ) symmetry and containing one asymptotically cylindrical end and one asymptotically flat end. We find that the t–ϕ symmetry implies the existence of a family of deformed data having the same horizon structure. This result allows us to measure how close the solutions are to the Lichnerowicz equation when arising from nearby free data.

Prediction and control of pillow defect in single point incremental forming using numerical simulations

Pillows formed at the center of sheets in Single point incremental forming (SPIF) are fabrication defects which adversely affect the geometrical accuracy and formability of manufactured parts. This study is focused on using FEA as a tool to predict and control pillowing in SPIF by varying tool size and shape. 3D Finite element analysis (FEA) and experiments are carried out using annealed Aluminum 1050. From FEA, it is found out that the stress/strain state in the immediate vicinity of the forming tool in the transverse direction plays a determinant role on sheet pillowing. Furthermore, pillow height increases as compression in the sheet-plane increases. The nature of in-plane stresses in the transverse direction varies from compressive to tensile as the tool-end geometry is changed from spherical to flat. Additionally, the magnitude of corresponding in-plane stresses decreases as the tool radius increases. According to measurements from the FEA model, flat end tools and large radii both retard pillow formation. However, the influence of changing tool end shape from hemispherical to flat is observed to be more important than the effect of varying tool radius, because the deformation zone remains in tension in the transverse direction while forming with flat end tools. These findings are verified by conducting a set of experiments. A fair agreement between the FEM and empirical results show that FEM can be employed as a tool to predict and control the pillow defect in SPIF.

Synthesis of Cone-Shaped Colloids from Rod-Like Silica Colloids with a Gradient in the Etching Rate.

We present the synthesis of monodisperse cone-shaped silica colloids and their fluorescent labeling. Rod-like silica colloids prepared by ammonia-catalyzed hydrolysis and condensation of tetraethyl orthosilicate in water droplets containing polyvinylpyrrolidone cross-linked by citrate ions in pentanol were found to transform into cone-shaped particles upon mild etching by NaOH in water. The diameter and length of the resulting particles were determined by those of the initial rod-like silica colloids. The mechanism responsible for the cone-shape involves silica etching taking place with a varying rate along the length of the particle. Our experiments thus also lead to new insights into the variation of the local particle structure and composition. These are found to vary gradually along the length of the rod, as a result of the way the rod grows out of a water droplet that keeps itself attached to the flat end of the bullet-shaped particles. Subtle differences in composition and structure could also be resolved by high-resolution stimulated emission depletion confocal microscopy on fluorescently labeled particles. The incorporation of a fluorescent dye chemically attached to an amine-based silane coupling agent resulted in a distribution of fluorophores mainly on the outside of the rod-shaped particles. In contrast, incorporation of the silane coupling agent alone resulted in a homogeneous distribution. Additionally, we show that etching rods, where a silane coupling agent alone was incorporated and subsequently coupled to a fluorescent dye, resulted in fluorescent silica cones, the orientation of which can be discerned using super-resolution confocal microscopy.

EXPERIMENTAL INVESTIGATION OF THE EFFECT OF THE INTERNAL TWO-PHASE FLOW AND THE BUBBLE SIZE ON THE EFFERVESCENT SPRAY CHARACTERISTICS

Reducing the pressurized atomizing gas in the effervescent atomizers with keeping fine spray is a desirable aim. This experimental study focuses on improving the characteristics of the effervescent spray (i.e. drop size and spray cone angle); while an in-out gas injection configuration atomizer operates under low gas-to-liquid ratios (GLR). These important characteristics are mainly affected by the internal two-phase flow pattern. Wherefore, shadowgraphy is utilized for visualizing and investigating the internal two-phase flow pattern directly upstream the exit orifice. The atomizer is operated at air gauge pressure of 0.6 Mpa and GLRs of (0.71% – 5.74%). For controlling the internal flow at the operating GLRs, two novel bubble breakers (BB) are designed and tested. The bubble breakers are fixed in the mixing chamber to affect the bubble size. The shadowgraph technique is utilized for visualizing and quantifying bubbles inside the atomizer, spray characteristics and the near nozzle spray. From the visualization and results, the internal two-phase flow patterns inside the mixing chamber vary from bubbly flow at the lowest three GLRs to a bubble-annular flow at the largest GLR, passing through an unsteady transition stage between these two patterns. Also, it is observed that the bubble breakers efficiently disintegrate large bubbles; the largest reduction percentage in the bubble size is 75.63% for the case of flat end BB at GLR of 2.21%. Also, the results showed that the drop size and spray cone angle are strongly affected by the bubble size (i.e. the internal flow structure) subsequently the presence of the bubble breakers. The largest reduction percentage in the droplet size is 68.88% for the case of the cone end BB at GLR of 0.77% and the largest increment percentage in the spray cone angle is 69.97% for the cone end BB at GLR of 0.77 %, all relative to the case of without BB.

Finite element analysis of surface milling of carbon fiber-reinforced composites

Despite increased applications of carbon fiber-reinforced plastic (CFRP) materials in many industries, such as aerospace, their machining is still a challenge due to their heterogeneity and anisotropic nature. In this research, a finite element model is used to investigate the cutting forces, chip formation mechanism, and machining damage present during the flat end milling of unidirectional CFRP. The material is modeled as an equivalent orthotropic homogeneous material, and Hashin’s theory is used to characterize failure in plane stress conditions. The friction coefficient between the tool and the composite material was assumed to be dependent on the carbon fiber orientation. A comparison of modeling and experimental results indicates that the model successfully predicts the cutting forces. The numerical model predictions of machining damage around the cutting area due to fiber compression damage and matrix cracking and the relation between damage extension and fiber orientation are confirmed through a comparison with SEM images of machined edges and surfaces.

Graphite saturable absorber based on the pencil-sketching method for Q-switching of an erbium fiber laser.

We experimentally demonstrate a practical and simple method for the preparation of a graphite-based, fiberized saturable absorber (SA). Our SA is prepared by using a low-cost graphite-core pencil that is commercially available from stationary stores to uniformly shade the flat end of a fiber ferrule. The saturable-absorption performance of the prepared SA was experimentally tested, and the feasibility of using the SA as a passive Q-switch was investigated through its incorporation into an erbium-doped-fiber ring cavity. The modulation depth of the SA is ∼1%, and the Q-switched pulses of a 1.98μs temporal width were readily obtained at a repetition rate of 46.08kHz.

티타늄 황삭가공에 있어서 절삭공구의 마모 특성에 관한 연구

The application of titanium has been gradually rising because the utilizing ranges for low weight and high strength are rapidly increased by the need for improving the fuel economy in production industries such as the aviation and automotive in recent. The purpose in this study is to investigate the appropriate cutting conditions on the life of flat and round end mills by measuring the maximum cutting temperature relative to the machining time, and calculating the wear rates of cutting tool with the spindle speed and feed rate of vertical machining center as a parameter in the titanium roughing cut machining which is widely used in critical parts of aircraft, cars, etc. When the wetted roughing cut machining of titanium with a soluble cutting oil is conducted by the flat and round end mills, the maximum cutting temperatures for a variety of spindle speed and feed rate are measured at ten-minute intervals during 60 minutes by an infrared thermometer, and the wear rates of cutting tool are calculated by the weight ratios based on tool wear before and after the experiment. It is found that the maximum cutting temperature and the wear rates of cutting tool are raised as the cutting amount per tool edge is increased with the rise of feed rate, in this experimental range, and as the frictional area due to the rise of contacting friction numbers between tool and specimen is increased with the rises of cutting time and spindle speed. In addition, the increasing rate of maximum cutting temperature in the flat and round end mills are the highest for the cutting time from 50 to 60 minutes, and the wear rate of cutting tool in the flat end mill is 1.14 to 1.55 times higher than that in the round end mill for all experimental conditions.

3D Parametric Modelling of Milling Cutter Geometry from Analytical Analysis

Numerical simulation of milling process needs an accurate model of cutting tool. In this paper, we describe the methodology developed to design flat and ball end mills in three-dimensional configuration. The geometry of these cutters is issued from an analytic study based on oblique cutting theory. The described model is performed by using parametric CAD software. Hence, it involves a big number of variables as the diameter, the helix, the rake and the clearance angles and the teeth number. Furthermore, the modelled cutters are compared to real scanned ones in order to validate the used methodology. The results show a good accuracy regarding the global three-dimensional shape.

A Unified Cutting Force Model for Flat End Mills Based on Cutter Geometry and Material Properties

A unified oblique cutting force model for flat end mills is developed. In this model, the cutting force is bridged among cutter geometry, material properties and cutting parameters. The cutter angles, material parameters and cutting parameters are the only inputs so that the model is applicable for different cutter-workpiece combinations and cutting parameters. The parameters in the model are solved by the geometric relations, applying Maximum Shear Stress Principle and Stabler’s chip flow rule. The material parameters are identified in a new method with orthogonal milling tests. The simulation results of the proposed model are in good agreement with experiments.