bluuebunny/crossref_metadata_2025 huggingface dataset:
Phase Transition in Niobophosphate Glass-Ceramic
Authors: Stunda Agnese , Mironova-Ulmane Nina , Borodajenko Natalija , Berzina-Cimdina Liga
Published: April 2011

Phase transition during crystallization of glass to glass-ceramic in system P2O5-CaO-Nb2O5-Na2O was studied. Several heating rates were compared – 1, 2, 5, 11 and 20°Cmin-1. DTA, XRD, FTIR and Raman analyses were performed. Niobophosphate glass-ceramic is found to form utterly different crystalline phases depending on maximal heating temperature, heating rate and time of maximal temperature maintenance. Crystallization temperatures of the same phases are strongly dependent on heating rate, while crystallinity of obtained phases is not. At lower temperatures poorly crystalline phosphates (Ca3(PO4)2, Ca10Na(PO4)7, Ca2P2O7) and niobates (NaNbO3 and Nb2O5) are identified. At higher temperatures a large amount of well crystalline niobophosphate (Na4(Nb8P4O32) and Ca2P2O7 forms. With increasing amount of Na4(Nb8P4O32), amount of NaNbO3 and Nb2O5 decreases.
Laser-Induced Modification of the Surface State and Optical Properties of CdTe Crystals
Authors: Poperenko Leonid V. , Gnatyuk Dmytro V. , Odarych Volodymyr A. , Yurgelevich Iryna V. , Levytskyi Sergiy N. , Aoki Toru
Published: April 2011

Optical properties and surface state of semiconductor CdTe crystals subjected to irradiation with nanosecond laser pulses were studied. Ellipsometric parameters Δ and Ψ were measured on two opposite surfaces of (111) oriented CdTe wafers before. The samples were subjected to polishing chemical etching and laser irradiation with energy densities lower and higher than the melting threshold of CdTe. The morphology and structure of CdTe crystals were monitored before and after treatments. Irradiation formed a thin modified surface layer on the both sides of CdTe crystals (Cd- and Te-terminated) with the similar optical constants n and k, respectively. However, the effective thicknesses of such modified layers differed and depended on the chemical and laser treatment conditions and also on the faces of CdTe(111) crystals.
Medical Image Region Extraction and 3D Modeling Based on Approximating Curves
Authors: Bolochko Katrina , Sisojevs Aleksandrs , Glazs Aleksandrs , Platkajis Ardis
Published: April 2011

This work describes several methods that intend to solve such medical image processing tasks as extraction and 3D visualization of the region of interest (ROI). The proposed methods were tested on the medical images of a brain acquired by computer tomography and proven to be applicable to different types of ROI, resulting in a possible visualization of several ROI at once, i.e. pathology and the head of a patient. The results can be used to provide practical improvements to the reliability of medical diagnostics.
Accurate and Fast Estimation of Optical Properties Using Optical Path Length and Spatially Resolved Reflectance Measurement
Authors: Yamashita Takayuki , Niwayama Masatsugu , Yamakawa Toshitaka
Published: April 2011

We developed a new practical method for determining the absorption coefficient and reduced scattering coefficient simultaneously by using the spatial light intensity profile and the optical path length based on the results of a Monte Carlo simulation. The proposed system is optically and electrically robust and practical because (1) light intensity detection of a continuous wave for the spatially resolved reflectance is stable, convenient, and fast, and (2) the optical path length calculated from the phase can be measured precisely using the digital phase detector of a laser rangefinder. The optical properties of the tissue-like medium were measured accurately and quickly.
Multi-Camera Shooting Support System for Novices in a Compact Studio
Authors: Nishio Norihiro , Deguchi Yuki , Sugiyama Takahiro , Takebayashi Yoichi
Published: April 2011

We developed a multi-camera shooting support system in a compact studio for novice cameramen. We analyzed the problems they faced when shooting video programs. We have suggested that our automated multi-camera controls and the adjustment of camera angles for face detection reduce the burden on novices. Our experiment shows that a novice cameraman alone can carry out the task of shooting a video program.
Sensory Device for Virtual Graffiti Creation
Authors: Jabłoński Ryszard , Borzym Agnieszka
Published: April 2011

The paper presents the synergic application of inertial, force, image and distance sensors for graffiti creation. The complete painting head and software generating picture were designed and realized. Painting head receives impulses and converts them into electric signal transmitted to the computer. Sensors deliver data information about distance, angles and a force applied on the tip of painting head and special algorithm converts this information into created blur shape. The information about angles distorts created blur and information about force increase-decrease, rarefy and thicken the graffiti blur. Painting head resembles spray can.
Nodal Numerical 2D Helmholtz Equation: Truncation Analysis
Authors: Morevs Patriks , Rimshans Janis S. , Guseynov Sharif E.
Published: April 2011

A functional nodal method for numerical solution of a two-dimensional Helmholtz equation is considered. The method uses a compact 7-point difference scheme and provides continuity of averaged fluxes and the numerical solution. Truncation analysis of the difference scheme is done and it is shown that the considered difference scheme is of the 2nd order of precision inside the domain.
A Method of Conversion of some Coefficient Inverse Parabolic Problems to a Unified Type of Integral-Differential Equation
Authors: Guseynov Sharif E. , Rimshans Janis S. , Kaupuzs Jevgenijs , Medvid' Artur , Zaime Daiga
Published: April 2011

Coefficient inverse problems are reformulated to a unified integral differential equation. The presented method of conversion of the considered inverse problems to a unified Volterra integral-differential equation gives an opportunity to distribute the acquired results also to analogous inverse problems for non-linear parabolic equations of different types.
Cog Framework - 3D Visualization for Mobile Robot Teleoperation
Authors: Sziebig Gábor , Zanaty Péter , Korondi Péter , Solvang Bjørn
Published: April 2011

A multi-layer mobile robot controller unit has been created and tested successfully to be able to work with different types of mobile robot agents. The paper presents a modular extensible system which is relying on top of modern open source libraries. The system handles a motion capturing suit and adapts it similarly as traditional peripheries. Robust posture recognition has been introduced on top of the motion suit adapter, which is used to instruct a mobile robot agent, while immerse stereographic feedback is provided to the human operator.
The Electrodynamic Human Motion Energy Converter with Planar Structure
Authors: Blums Juris , Terlecka G. , Vilumsone Ausma
Published: April 2011

The performance of the electrodynamic human motion energy converter with planar structure is under investigation. The electrodynamic converter consists of a flat, spiral-shaped coil and a rectangular magnet that during human motion moves in respect to one another. During the motion of the rectangular magnet with a remanence 0.1 T over a flat, formed up as an Archimedes spiral coil with 25 turns, an average power of about 10 W is generated. The generator elements can both be deployed on a variety of clothing items which move relative to one another during the human motion, and also realizing the forced oscillation of the magnet during walking.
Investigation of Textile Materials for Laser Light Beam Scanning
Authors: Dabolina Inga , Vilumsone Ausma , Blums Juris
Published: April 2011

The scanning of human body as a method for gaining human measurements has several preferences. The gathering of data is possible in a very short time. In comparison to manual measuring methods, scanning acquires a larger amount of measurements. There are several modes of gaining human body measurements using the scanning system: laser scanning, light beam scanning, etc. A research on the laser beam reflection capabilities on different textile materials has been performed. The description of laser reflections has been compared to the Lambert’s law’s characteristics. The matrix of material selection is made in the process of planning the experiment and all possible materials are presented in this matrix. Eight textile materials are chosen for the experimental work: six lingerie and two additional materials. A laser beam with an angle of incidence of 0º and 45º is used to make the experiment. The dependence of the results on the wavelength of laser beams has also been compared.
“Black Silicon” Formation by Nd:YAG Laser Radiation
Authors: Medvid' Artur , Onufrijevs Pavels , Dauksta Edvins , Kyslyi Volodymyr
Published: April 2011

The possibility to form “black silicon” on the surface of Si structure by Nd:YAG laser radiation has been shown. The shape and height of micro-cone structure strongly depends on Nd:YAG laser intensity and number of laser pulses. Light is repeatedly reflected between the cones in the way that most of it is absorbed. Si micro-cone structure spectral thermal radiation is close to black body spectral radiance, which makes this structure useful for solar cells application. The micro-chemical analysis performed by SEM has shown that the microstructures contain NiSi2. This was approved by presence of LO phonon line in Raman back scattering spectrum. The control of micro-cone shape and height was achieved by changing the laser intensity and number of pulses.
Band Bending of n-GaP(001) and p-InP(001) Surfaces with and without Sulfur Treatment Studied by Photoemission (PES) and Inverse Photoemission Spectroscopy (IPES)
Authors: Liu K.Z. , Shimomura Masaru , Fukuda Y.
Published: April 2011

Surface electronic structures of n-GaP(001) and p-InP(001) with and without sulfur treatment have been studied by X-ray photoelectron spectroscopy (XPS), synchrotron radiation photoemission spectroscopy (SRPES), and inverse photoemission spectroscopy (IPES). The Fermi level (EF) of a clean n-GaP(001)-(2x4) surface is found to be pinned at 0.2 eV above the valence band maximum (VBM), suggesting that the surface electronic bands are bent upward. XPS spectra reveal that the EF is moved to 2.3 eV above the VBM by the sulfur treatment, implying that the sulfur-treated surface has flat bands. The IPES result shows that empty dangling bond states on Ga atoms at the surface are located at the conduction band minimum (CBM) and they disappeared with the treatment. SRPES spectra of a clean p-InP(001)-(2x4) surface indicate that the EF is located at 0.3 eV above the VBM and surface states due to phosphorus atoms are at –0.9 eV below the EF. The result implies that the surface has almost flat bands. Empty dangling bond states on In atoms at the clean surface are found to be located at the conduction band edge. Surface states due to the In-S bonds are found at –3.5 eV below the EF for the sulfur-treated surface. The sulfur treatment of the clean surface leads to a little shift (0.1 –0.2 eV) of the EF and to considerable reduction of the empty states in the band gap. A type conversion of p- to n- is not observed in the present work. This is discussed in terms of the thickness of a sulfide layer.
A Novel Refrigerator Device Using Single-Electron Pump Applicable to SOI Wafers
Authors: Ikeda Hiroya , Salleh Faiz
Published: April 2011

We propose a novel single-electron refrigerator (SER) which can be fabricated in silicon-on-insulator wafers. The SER has a structure of single-electron box combined with single-electron pump (SEP). An equivalent circuit of the SEP-refrigerator is represented and its stability diagram (Coulomb diamond) is theoretically calculated. It is found that the stability diagram has a honeycomb structure. Moreover, the operation of the single-electron transfer and single-electron storage is numerically demonstrated using a Monte Carlo simulation based on the orthodox theory of the Coulomb blockade phenomenon.
Analysis of Electron Spin-Spin Interaction in Coupled Quantum Well
Authors: Ito Tetsu , Shichi Wataru , Ichida Masao , Gotoh Hideki , Kamada Hidehiko , Ando Hiroaki
Published: April 2011

Electron spin-spin interaction in asymmetric coupled GaAs/AlGaAs quantum well (QW) is investigated through electron spin precession measurements. In the experiment, the precession (Larmor) frequency of electrons localized in thin and thick QWs are measured by means of polarization- and time-resolved photoluminescence measurements under magnetic field. The Larmor frequency observed in thin well was transformed to that of thick well with increasing excitation power density. This dependence can be reproduced by theoretical calculations, which take into account electron spin-spin interactions in GaAs wells.
CZTS Monograin Powders and Thin Films
Authors: Mellikov E. , Meissner D. , Altosaar M. , Kauk M. , Krustok J. , Öpik A. , Volobujeva O. , Iljina J. , Timmo K. , Klavina I. , Raudoja J. , Grossberg M. , Varema T. , Muska K. , Ganchev M. , Bereznev S. , Danilson M.
Published: April 2011

This paper reviews results of studies on different materials and technologies for polycrystalline solar cells conducted at Tallinn University of Technology. Structural properties and defect structure of kesterite CZTS compounds (Cu2ZnSnSe4, Cu2ZnSn(SSe)4) were studied. Influence of selenization parameters of a Zn-Cu-Sn stacked layer on the CZTS layer growth and on the morphology, distribution of elements was analyzed. All the results obtained have been used to optimize the technology of producing solar cell structures in different designs. Cu2ZnSnSe4 and, Cu2ZnSn(SSe)4 based monograin layer solar cells were developed.
Magnetization Peculiarities of Defects in Silicon Produced by Ni+, Co+, Fe+ Ion Implantation
Authors: Karabko Aliaksandra , Dostanko Anatoly , Lapchuk Natalia , Onufrijevs Pavels
Published: April 2011

Silicon p-type (100) wafers implanted with Ni, Co, Fe ions to a dose range of 3∙1013–3∙1016 cm-2 have been investigated by means of EPR. The g-factor from dangling bonds of silicon modified by Ni, Co, Fe ion implantation is found to be different from the g-factor of amorphous silicon explained by the change of the local magnetic permeability r. Extreme character of the spin concentration on dose dependence is found, being not typical for silicon.
Optical Characterization of MBE-Grown ZnO Epilayers
Authors: Karaliunas Mindaugas , Serevicius Tomas , Kuokstis Edmundas , Juršėnas Saulius , Ting Shao Ying , Huang Jeng Jie , Yang Chih Chung
Published: April 2011

Optical characterization of molecular-beam-epitaxy-grown ZnO and MgZnO epitaxial layers on sapphire (0001) substrates is presented. The parameters such as carrier recombination time and optical gain coefficient are analyzed. Radiative recombination mechanisms of ZnO in dense quasiparticle system are discussed. The ZnO epilayers even with lower structural quality are tolerable for applications in optoelectronics as light emitters.
Color Calibration Method Based on Spectrally Reproduced Colors and its Application to XYZ-Type Digital Camera
Authors: Kretkowski M. , Jabłoński Ryszard , Shimodaira Y.
Published: April 2011

This paper presents the development of a color calibration method based on spectrally reproduced colors produced by multi-primary color narrow-band LED’s. The additive mixture of the primary colors can spectrally reproduce an object color. This approach has been used in our work to overcome the insufficient calibration results obtained by commonly used color targets such as the Macbeth Chart. The method has been tested using a developed prototype of digitally controlled light source calibrated to simulate object color under D65 Daylight standard illumination. The method allows for obtaining of the average color difference for the calibrated XYZ camera of ∆E=0.79 and shows significant improvement in comparison with calibration using standard Macbeth (∆E=1.47). Moreover, we explain the advantages of color calibration with usage of multi-primary light source with regard to the amount of the primary colors.
3D Modelling and Simulation of Gun Drilling
Authors: Klocke Fritz , Abouridouane Mustapha , Gerschwiler Klaus , Lung Dieter
Published: April 2011

The main objective of this paper is the development and validation of a three dimensional thermomechanically coupled finite element model for gun drilling AISI 4150 quenched and tempered steel. The Lagrangian formulation proposed in the FE code DEFORM 3DTM and the constitutive Johnson-Cook material model were utilized to simulate the chip formation and to predict the cutting reaction forces as well as the temperature in gun drilling process using carbide gun drills with two different diameters. During gun drilling simulation, modified gun drill cutting edge rounding and friction law are performed to investigate the effect of tool wear and lubrication on feed force and torque respectively. Experimental gun drilling tests were carried out in steel AISI 4150 for the validation of the developed 3D FE model. The developed and validated 3D FE model can be used for optimizing the cutting process in gun drilling (good surface finish and straightness) taking into account the complex gun drill geometry, cutting conditions, heat transfer and the thermo-mechanical behaviour of the workpiece material.
Validation of Finite Element Modeling of Drilling Processes with Solid Tooling in Metals
Authors: Ma Lin , Marusich Troy D. , Usui Shuji , Wadell Jon , Marusich Kerry , Zamorano Luis , Elangovan Hari
Published: April 2011

Drilling is the source of major cost and time elements in airframe assembly due to hole quality, burr formation, and tool life problems plaguing the industry. Aerospace applications focus on holes for rivets loaded in shear in aluminum, titanium and composite stack-ups. Optimal chip flow and tool life are often in competition with burr formation, general hole quality, and cycle time. Physics-based modeling of drilling processes can provide insight and information not readily available or easily obtained from experiments, and in a much faster time frame. A three-dimensional finite element-based model of drilling is presented which includes fully adaptive unstructured meshing, tight thermo-mechanical coupling, deformable tool-chip-workpiece contact, interfacial heat transfer across the tool-chip boundary, and constitutive models appropriate for high strain-rate, large strain and high temperature deformation.
Coating-Substrate-Simulation with an Advanced Adaptive Finite Element Code
Authors: Heller Katrin , Wohlgemuth Reiner , Meyer Arnd , Leopold Juergen
Published: April 2011

The stability of coating-substrate-systems in uences the chip formation and the surface integrity of the new generated workpiece surface, too. Using FE simulation, deformations, strains and stresses in coated tools, caused by external and internal loads, can be computed on a microscopic scale. Since both, the whole macroscopic tool (in mm-scale) and the microscopic coating layers (in m-scale up to nm-scale) must be included in the same geometrical simulation model, graded high-resolution FE meshes must be used. Nevertheless, the number of nodes in the 3-D computational FE grid reaches some millions, leading to large computational time and storage requirements. For this reason, an Advanced Adaptive Finite Element (AAFEM) software has been developed and used for the simulation.
Investigation of the Machining Behavior of Metal Matrix Composites (MMC) Using Chip Formation Simulation
Authors: Schulze Volker , Zanger Frederik , Michna Jürgen , Ambrosy Florian , Pabst Rüdiger
Published: April 2011

The machining of metal matrix composites (MMC) induces cyclic loadings on tools, which creates new challenges for machining. In particular the distributed reinforcement, consisting of silicon carbide (SiC) or aluminum oxide (Al2O3), evokes especially high mechanical loads. The development of metal matrix composites is pointing towards higher fractions of reinforcements, which affects the resulting forces and temperatures. In this regard the influence of varying particle filling degrees, particle diameters, cutting velocities and tool geometries in terms of rake angle and cutting edge radius have been investigated by means of cutting simulation. For the process a self-designed continuous remeshing routine was used for which a dual phase material behavior has been implemented. The developed simulation model enables investigations of the machining behavior of metal matrix composites to the extent that ideal process strategies and tool geometries can be identified by multiple simulations.
Virtual Reality Animation of Chip Formation during Turning
Authors: Yang Xiang , Marx Tobias , Zimmermann Marco , Hagen Hans , Aurich Jan C.
Published: April 2011

Virtual Reality (VR) technology allows the animation of machining operations. The kinematic of the machining operation and the geometry of the parts are allocated prevalently to VR using the Virtual Reality Modeling Language (VRML). In order to visualize the machining operation close to reality, the chip formation process needs to be animated as well. This paper presents the virtual reality animation of external cylindrical turning considering the chip formation and the results of the machining operation, such as the process forces. The chips are described numerically using JavaScript which is embedded into the VRML. The JavaScript accesses in addition to an experimentally generated database in order to display the results of the machining operation. The turning operation is visualized both in a non-immersive graphic user interface and an immersive Cave Automatic Virtual Environment (CAVE).
Numerical Prediction of the Interface Temperature Using Updated Finite Difference Approach
Authors: Bartoszuk Marian , Grzesik Wit
Published: April 2011

This investigation is devoted to the heat flow problem occurring in dry orthogonal machining of a C45 medium carbon steel performed with uncoated single-point carbide tools. Finite Difference Approach (FDA) is applied to predict the variations of temperature distribution, and both average and maximum temperatures at the tool-chip interface, resulting from differentiating the heat flux configuration, and additionally the changes of thermal resistance along the tool-chip contact length. Moreover, some realistic computing errors due to possible measuring variations of the tool-chip contact length and the density and dimension of heat source on the shear plane were assessed and considered as input data in simulations. Finally, the measured values of temperatures using natural tool-work thermocouples have confirmed that the models proposed predict acceptably the average interface temperatures and estimate their maximum values for carbide tools.
Analysis of Forces and Temperatures in Conventional and Ultrasonically-Assisted Cutting of Bone
Authors: Alam Khurshid , Ghafoor Abdul , Silberschmidt Vadim V.
Published: April 2011

Bone cutting is a frequently used procedure in orthopaedic and neuro surgeries. Current research on bone cutting is concerned with the efforts to decrease the forces generated during cutting the bone as well as temperature to avoid mechanical and thermal damage (bone necrosis) induced by surgical tools. The paper presents results of finite-element simulations of conventional cutting (CC) and ultrasonically-assisted cutting (UAC) of bone in order to understand thermomechanics of the process. The study was aimed at investigating the levels of tool-penetration force and temperatures induced in the bone when a hard cutting tool penetrates into it in both types of cutting. The models allow the quantitative analysis of forces and temperatures produced during the cutting process. The use of UAC reduces the tool penetration force and temperature in the cutting region
Finite-Element Simulations of Split Hopkinson Test of Ti-Based Alloy
Authors: Demiral Murat , Leemet Tõnu , Hokka Mikko , Kuokkala Veli Tapani , Roy Anish , Silberschmidt Vadim V.
Published: April 2011

Ti-based alloys are extensively used in aerospace and other advanced engineering fields due to their high strength and toughness, light weight, excellent corrosion resistance and ability to withstand extreme temperatures. Since these alloys are hard to machine, there is an obvious demand to develop simulation tools in order to analyse the material's behaviour during machining and thus optimise the entire machining process. The deformation processes in machining of Ti-alloys are typically characterized by high strains and temperatures. A Split Hopkinson Pressure Bar (SHPB) technique is a commonly used experimental method to characterize a material`s behaviour at high strain rates; a stress-strain relation of the material is derived from the obtained experimental data. A computational study on a three-dimensional finite element model of the SHPB experiment is performed to assess various features of the underlying mechanics of deformation processes at high-strain and -strain-rate regimes. In the numerical analysis, an inhomogeneous deformation behaviour is observed in the workpiece at the initial stages of compression contrary to a standard assumption of stress and strain homogeneity in the specimen.
A Lagrangian FEM Model to Produce Saw-Toothed Macro-Chip and to Study the Depth of Cut Influence on its Formation in Orthogonal Cutting of Ti6Al4V
Authors: Ducobu François , Rivière-Lorphèvre Edouard , Filippi Enrico
Published: April 2011

The foundations of micro-milling are similar to macro-milling but the phenomena it involves are not a simple scaling-down of macro-cutting. The importance of the minimum chip thickness is one of the significant differences between the two processes. The lagrangian FEM model presented in this paper aims to study the depth of cut influence on chip formation of Ti6Al4V in orthogonal cutting. It is firstly used to compare the modelled saw-toothed macro-chip morphology and cutting forces to experimental cutting results from literature. Then a minimum chip thickness prediction is performed by decreasing the depth of cut. Finally this study is the opportunity to highlight the specific features of micro-cutting reported in literature, such as the effective negative rake angle of the tool or the size effect. The model presented brings therefore a numerical contribution to the comprehension of these phenomena.
Computational Study of Ultrasonically-Assisted Turning of Ti Alloys
Authors: Muhammad Riaz , Ahmed Naseer , Demiral Murat , Roy Anish , Silberschmidt Vadim V.
Published: April 2011

Industrial applications of titanium alloys especially in aerospace, marine and offshore industries have grown significantly over the years primarily due to their high strength, light weight as well as good fatigue and corrosion-resistance properties. The machinability of these difficult-to-cut metallic materials with conventional turning (CT) techniques has seen a limited improvement over the years. Ultrasonically-assisted turnning (UAT) is an advanced machining process, which has shown to have specific advantages, especially in the machining of high-strength alloys. In this study a three-dimensional finite element model of ultrasonically-assisted oblique cutting of a Ti-based super-alloy is developed. The nonlinear temperature-sensitive material behaviour is incorporated in our numerical simulations based on results obtained with split-Hopkinson pressure bar tests. Various contact conditions are considered at the tool tip-workpiece interface to get an in-depth understanding of the mechanism influencing cutting parameters. The simulation results obtained are compared for both CT and UAT conditions to elucidate main deformation mechanisms responsible for the observed changes in the material’s responses to cutting techniques.
Modeling the Process-Induced Modifications of the Microstructure of Work Piece Surface Zones in Cutting Processes
Authors: Schulze Volker , Michna Jürgen , Zanger Frederik , Pabst Rüdiger
Published: April 2011

Cutting processes lead to mechanical and thermal loading of tool and work piece. This loading entails a direct influence of the cutting process on the surface layers of the manufactured work pieces. As a result, residual stresses and modifications of the micro-structure like white layers can occur in surface-near zones of the work piece. This paper presents the development of a FE-simulation model to predict phase transformations due to cutting processes. Therefore a 2D-FE-cutting simulation including a dynamic re-meshing is combined with a simulation routine to describe phase transformations that was primarily developed to simulate laser hardening. This paper illustrates the implemented mechanisms to determine phase transformations considering short time austenization and shows first experimental results revealing the influence of process parameters on the surfaces microstructure.
Analytical and Numerical Modeling of Strain Hardening in AISI 304 Steel Cutting
Authors: D'Urso Gianluca Danilo , Aldo Attanasio
Published: April 2011

The present paper reports the results obtained investigating surface work hardening in turning as a function of cutting speed, feed rate and tool wear. An experimental campaign was carried out using AISI 304 steel as workpiece material. Pipes 4 mm thick were machined under orthogonal cutting conditions. Tools with flat rake surface were adopted and dry cutting conditions were taken into account. Cutting speed and feed rate were varied and the tool wear was monitored using a CNC visiomeasuring machine. The tool wear was related to the workpiece strain hardening. Starting from micro Vickers test data, an analytical model representing the strain hardening behavior along a workpiece section was defined. In addition, a Fortran subroutine for the simulation of strain hardening by means of a 2D FEM code was implemented.
Analysis of Surface Integrity in Dry and Cryogenic Machining of AZ31B Mg Alloys
Authors: Pu Zheng Wen , Caruso Serafino , Umbrello Domenico , Dillon O.W. , Puleo D.A. , Jawahir I.S.
Published: April 2011

Surface integrity of machined products can have a critical impact on their performance, such as corrosion, wear and/or fatigue resistance. It has been reported that reducing the grain size of AZ31B Mg alloys could significantly enhance its corrosion resistance, which is often the limiting factor for its wide application. Severe plastic deformation (SPD) has proved to be an effective way to induce grain refinement. In this study, the potential of cryogenic machining as a novel SPD method to induce grain refinement on the surface of AZ31B Mg alloys was investigated. The microstructures of the workpiece surface/sub-surface and the machined chips after both dry and cryogenic machining were studied. A surface layer where nanocrystallized grains exist was found in the machined surface under cryogenic conditions. Increasing the edge radius of the cutting tool resulted in a thicker grain refinement layer. In addition to the experimental study, an FE model based on the Johnson-Cook constitutive equation was developed and validated using experimental data in terms of chip morphology and forces. The capability of this model to predict critical deformation parameters for dynamic recrystallization (DRX), such as strain, strain-rate and temperature, was demonstrated. With further development, the model can be used to predict the onset of DRX and the grain size on the machined surface.
Surface Integrity Functional Analysis in Hard Turning AISI 8620 Case Hardened Steel through 3D Topographical Measurement
Authors: Farias Adalto , Delijaicov Sergio , Stipkovic Filho Marco , Batalha Gilmar F.
Published: April 2011

The purpose is to contribute with information on the resulting surface condition from hard turning process of mechanical components manufactured from carburized steel. The surface was examined by parameters obtained from the three-dimensional surface topography obtained with an interferometric laser instrument. The selected roughness parameters analysis intends to have a functional characterization such as bearing capacity, fluid and lubricants retention ability and contact wear resistance. The results obtained from the surface roughness measurement show consistency with other authors’ results, and the technique of hardened material turning is capable of producing surfaces with functionality and quality.
Identification of Surface Generation Mechanisms Based on Process Feed-Back and Decomposition of Feed Marks
Authors: Grzesik Wit , Brol Sebastian
Published: April 2011

This paper proposes a novel integrated approach to the prediction of surface generation mechanisms which takes into account both cutting process outputs and distortions of the individual feed marks in comparison to an ideal kinematical model. For this task, the recorded surface roughness profile was decomposed using special algorithms. The mechanisms of real surface generation considered include the plastic side flow and spring back effects, the cutting edge sharpness and its wear, and dynamic interactions between the tool and the workpiece. The computation procedure was verified for different workpiece materials in conjunction with uncoated and coated, sharp and worn, tools.
Development of a Simulation Model to Investigate Tool Wear in Ti-6Al-4V Alloy Machining
Authors: Schulze Volker , Zanger Frederik
Published: April 2011

Titanium alloys like Ti‑6Al‑4V have a low density, a very high strength and are highly resistant to corrosion. However, the positive qualities in combination with the low heat conductivity have disadvantageous effects on mechanical machining and on cutting in particular. Ti‑6Al‑4V forms segmented chips for the whole range of cutting velocities which influences tool wear. Thus, optimization of the manufacturing process is difficult. To obtain this goal the chip segmentation process and the tool wear are studied numerically in this article. Therefore, a FEM model was developed which calculates the wear rates depending on state variables from the cutting simulation, using an empirical tool wear model. The segmentation leads to mechanical and thermal load variations, which are taken into consideration during the tool wear simulations. In order to evaluate the simulation results, they are compared with experimentally obtained results for different process parameters.
Predictive Modeling for Distortion in Large, Thin-Walled Machined Components
Authors: Rakshit Abhik , Usui Shuji , Marusich Troy D. , Marusich Kerry , Zamorano Luis , Elangovan Hari
Published: April 2011

Machining of large monolithic structures is standard practice in today’s aerospace world. Driven by cost and performance, it is becoming necessary for airframe manufacturers to machine parts better, faster, lighter, and cheaper than ever before. When machining these large monolithic structures, however, distortion becomes a significant problem. The typical solution to this problem is to machine with lower than optimum material removal rates, and perform additional fixture rotations – both of which add unnecessary time and cost to the manufacturing process. A finite element model has been developed specifically to predict and control these distortions. The model takes into consideration the machining-induced residual stresses, as well as the bulk stresses in the material from the manufacturer.
Analysis of Sintering Parameters by SPS on Cemented Carbide
Authors: Bertolete Marcelo , Machado Izabel Fernanda , Rodrigues Daniel
Published: April 2011

The aim is to analyze the influence of two sintering process parameters concerning the compact densification of WC-Co. The input variables studied were uniaxial pressure (40 and 60 MPa) and holding time (1 and 3 minutes). The output variables monitored were relative density, microstructural features, besides online monitoring of dynamics of sintering. The samples were sintered in a Dr. Sinter-Syntex machine of Spark Plasma Sintering (SPS), which allows heating rate greater than conventional sintering techniques, with the advantage of lower temperature, time and energy consumption. The powder used was a compaction residue of grade K (with content between 3 and 12%Co). The results showed significant influence of pressure on the density and percentage of the porous area; however, the process parameters did not affect the grain size.
Dynamic Study of Thin Wall Part Turning
Authors: Lorong Philippe , Larue Arnaud , Perez Duarte Alexis
Published: April 2011

The numerical simulation of machining process is a key factor in the control of parts machining process. Its development aims at improving the process reliability and reduces the time spent during the process planning stage. In this context, we use a specific time domain simulation allowing modeling the dynamics of a thin wall part turning operation. After having introduced the basics of the proposed approach we present a specific cutting test that has been designed to specifically measure and control the dynamics of the part and the cutting conditions of a finishing toolpath. The influences of the cutting speed and damping coefficient on the chatter occurrence are discussed. In order to better control the simulation uses, an analysis of the simulation parameters influences on the simulated results is proposed.
A Novel Approach to Thin-Wall Machining of Aerospace Structures - Stability Margin Prediction Using a New Damping Modelling Approach
Authors: Sim Wei Ming , Adetoro Oluwamayokun B. , Wen Pi Hua
Published: April 2011

The eco-friendly and economic challenges are driving more and more aerostructure components with thin wall and deep pocket features. These features are getting thinner and deeper and become impractical during part manufacturing. Therefore, there is a need to better understand the mechanics, kinematics and dynamics of thin wall machining (which is the focus in this paper). In this paper, the application of a newly discovered relationship between the workpiece geometry and its damping parameters in the machining of aerospace structures is presented. This relationship allows for the prediction of damping ratios, without the use of experimental results for any wall with a different thickness compared to a reference wall. A previously proposed ‘improved stability lobes model’ is used to validate the damping model, as this model considers the nonlinearity of the cutting force coefficients. While a finite element method (FEM) is used to obtain natural frequencies and modal stiffness’s at different locations along the workpiece or toolpath, required in the stability model. The advantage of this new damping model is that, it alleviates the burden of having to carry out modal experiments to obtain the damping parameters required for subsequent stability margin predictions, as the work-piece thickness changes during machining.
Modeling of Cutting Process with Cutter Axis Inclination
Authors: Matsumura Takashi
Published: April 2011

Multi-axis controlled machining has been increasing with the demand for high quality in mold manufacturing. The cutter axis inclination should be properly determined in the milling operations. The paper discusses the cutting process of ball end mill with the cutter axis inclination. Two mechanistic models are presented to show the effect of the cutter axis inclination on the tool wear and the surface finish. The actual cutting time during a rotation of the cutter reduces with increasing the cutter axis inclination. Then, the tool is cooled in the non-cutting time. The tool wear is suppressed with reducing the cutting temperature. The surface finish is also improved by increasing cutting velocities with the cutter axis inclination. When the cutter is inclined in the feed direction, the effect of the edge roughness on the surface finish is eliminated. The discussion based on the simulation is verified in the cutting tests for brittle materials.
Modeling and Analysis Effects of Material Removal on Machining Dynamics in Milling of Thin-Walled Workpiece
Authors: Luo Ming , Zhang Ding Hua , Wu Bao Hai , Tang Ming
Published: April 2011

In aerospace industry, thin-walled workpieces are widely used in order to reduce the weight and to fulfill the high demands of their later applications. These workpieces are usually highly sophisticated and difficult to machine according to their geometry and material choice. In this paper, influence of material removal within the thin-walled workpiece machining operation on the dynamic properties of the workpiece and the machining process system is discussed. Aiming at learning about dynamic properties evolution during the machining operation, different milling processes of thin-walled plate are studied. Numerical simulation methods are employed in the study to investigate the dynamic properties evolution and machining stability with the material removal process in the milling process of thin-walled workpiece. The investigation results are expected to be used for designing optimized material removal sequence, which will guarantee highly material removal rate as well as highly machining accuracy of thin-walled workpiece.
A New Experimental Setup and Method to Analyze Cutting Forces in Non-Stationary Conditions
Authors: Yaqub Sajid , Larue Arnaud , Coffignal Gerard
Published: April 2011

The numerical simulation of machining, when dealing with flexible workpieces, still needs to be improved by the introduction of more accurate cutting force models. The aim of this paper is to propose a general method which is designed to generate transient cutting forces and severe cutting conditions including process damping to be able to set up cutting laws in these cases. In this first approach, the method is limited to orthogonal cutting. The method is based on a special design of a very simple "flexible workpiece" where slots have been introduced in the machined area to get an intermittent cutting. The exibility of the workpiece induces axial vibrations like it is done in vibration drilling and the presence of slots leads to cutting conditions similar to those of milling. The proposed testing device has been designed to be flexible along one degree of freedom, while the cutting tool is considered as rigid. This allows to generate cutting conditions where the axial depth of cut fluctuates as well as the contact between the cutting tool and the workpiece. The experimental setup allows the measurement of cutting forces and the simultaneous measurement of the relative tool/workpiece displacements. The measured signals and numerical interpretations of the machining operation allow to compare a proposed cutting law with the experimental results. The cutting law parameters can then be optimized, even when process damping occurs. The paper introduces a first application of the proposed method.
FEM-Based Simulation of Temperature in Speed Stroke Grinding with 3D Transient Moving Heat Sources
Authors: Linke Barbara , Duscha Michael , Vu Anh Tuan , Klocke Fritz
Published: April 2011

The grinding process is one of the most important finishing processes to obtain high surface quality. Nowadays, grinding is also considered as a high performance process with high material removal rates. Nevertheless, to avoid thermally-induced structural changes poses a major challenge for this manufacturing technology. Until now, the Finite Element Method (FEM) has been widely applied as a proper numerical technique to predict workpiece properties in machining processes. However, actual models in grinding are limited to conventional grinding processes with simple workpiece profiles and low table speeds. In this paper, finite element simulations are expanded to 3-dimensional (3D) models with temperature-dependent material properties and heat source profiles derived from experimental results, i.e. tangential forces. Both temperature simulation and measurement were conducted for deep grinding, pendulum grinding and speed stroke grinding in the table speed range of vw = 12 m/min to 180 m/min and specific material removal rates of Q’w = 40 mm³/mms. Overall, the simulation results show a good agreement with the measured temperature and surface integrity after grinding. This research indicates that a 3D FE model with temperature dependent material properties can predict realistic temperature fields in speed stroke grinding. Therefore, the experiment and measurement costs and time can be reduced by FEM simulation.
Cutting Forces Modeling in Finish Turning of Inconel 718 Alloy with Round Inserts
Authors: Campocasso Sebastien , Costes Jean Philippe , Poulachon Gérard , Perez Duarte Alexis
Published: April 2011

In turning, the applied forces have to be known as accurately as possible, especially in the case of difficult-to-cut materials for aircraft workpieces finishing operations. Traditionally, edge discretisation methodology based on local cutting laws is used to determine the cutting forces and results are usually considered suitable. Nevertheless, only the rake face is considered in most of studies and the cutting relations are determined by direct identification with a straight edge. This study deals with finishing operations of Inconel 718 alloy with one type of round insert. The main objective is to formulate a novel cutting forces model, taking into account the clearance face. First, a generic model based on a geometrical description using homogeneous matrix transformation is presented. Then, cutting coefficients are identified by inverse identification from experimental measurements distributed with an orthogonal design experiment including tool wear. Finally, modeling and experimental values of the cutting forces are compared and the identified model is analysed.
Theoretical and Experimental Determination of Geometry Deviation in Continuous Path Controlled OD Grinding Processes
Authors: Denkena Berend , Fischer Ruben
Published: April 2011

A simulation method for the continuous path controlled grinding process is described in this paper. The process model allows a virtual analysis of the process parameters, different input conditions and their influence concerning workpiece geometry. The machine structure is represented by a structural dynamic system. The dynamic influence of the machine axes is considered by its control system parameters. In this machine model, the positioning error of the axes can be calculated in relation to the reference position. This is used to compute the local engagement numerically. The process force is estimated by means of an empirical grinding force model. Hence, the overall process force can be calculated and fed back into the dynamic model. Closed-loop modeling allows to rate the influence of different parameters with respect to process errors. Finally, a parameter study and the model verification under real conditions are presented on the basis of the wheel head oscillating pin grinding process of crankshafts.
Machinability Evaluation in the Ultrasonic Drilling (USD) Process of Aluminum Oxide-based Ceramics
Authors: Jadoun R. S.
Published: April 2011

The ultrasonic drilling (USD) has been used in the manufacture of the hard, fragile, difficult to cut, nonconductive ceramic materials. In this study, the mathematical models of material removal rate (MRR) and surface roughness (SR) have been obtained for the machinability evaluation in the USD process of aluminum oxide-based ceramic material. The experimental plan adopts the face centered central composite design (CCD). The mathematical models using the response surface methodology (RSM) are developed so as to investigate the influences of three machining parameters, including the power rating, grit size and slurry concentration on the performance characteristics of MRR and SR. It has been proved that the proposed mathematical models in this study would fit and predict values of the performance characteristics, which would be close to the readings recorded in experiment with a 95% confidence level. The significant parameters that critically affect the performance characteristics are examined.