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Judith Shackleton - One of the best experts on this subject based on the ideXlab platform.

  • a comparative study of laser direct metal Deposition characteristics using gas and plasma atomized ti 6al 4v powders
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2011
    Co-Authors: Naveed M Ahsan, Andrew J. Pinkerton, R J Moat, Judith Shackleton
    Abstract:

    This research presents a comparative study of the characteristics of laser direct metal Deposition (LDMD) using two types of Ti-6Al-4V powder. Ti-6Al-4V powders prepared using the gas-atomization (GA) and the plasma rotating electrode (PREP) processes were first analyzed using laser diffraction, scanning electron microscopy and micro computed tomography. A 1.5 kW diode laser with a coaxial Deposition Head was then used to deposit a number of thin-wall structures at a range of processing parameters from each of the powders. The deposited structures were characterized using optical microscopy, scanning electron microscopy. X-ray diffraction and micro computed tomography (MicroCT). The results show some potential benefits of using PREP powder in laser direct metal Deposition. PREP powder has a higher Deposition rate and deposits show lower intralayer porosity and lower surface roughness. In both cases, deposits of Ti-6Al-4V exhibit a unique epitaxial prior beta grains microstructure that transforms to alpha lathes and retained beta during cooling. X-ray diffraction results show that the overall microstructure is alpha + beta and not martensitic. The lamellar alpha + beta phase spacing (S alpha+beta) increases with laser power but seems unaffected by variation in the mass flow rate of the powder. Micro hardness of the laser deposited Ti-6Al-4V is dependent on the lamellar alpha + beta phase spacing (S alpha+beta) and PREP powder deposits show lower micro hardness than GA powder deposits. (C) 2011 Elsevier B.V. All rights reserved.

  • A comparative study of laser direct metal Deposition characteristics using gas and plasma-atomized Ti–6Al–4V powders
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2011
    Co-Authors: M. Naveed Ahsan, Andrew J. Pinkerton, R J Moat, Judith Shackleton
    Abstract:

    This research presents a comparative study of the characteristics of laser direct metal Deposition (LDMD) using two types of Ti-6Al-4V powder. Ti-6Al-4V powders prepared using the gas-atomization (GA) and the plasma rotating electrode (PREP) processes were first analyzed using laser diffraction, scanning electron microscopy and micro computed tomography. A 1.5 kW diode laser with a coaxial Deposition Head was then used to deposit a number of thin-wall structures at a range of processing parameters from each of the powders. The deposited structures were characterized using optical microscopy, scanning electron microscopy. X-ray diffraction and micro computed tomography (MicroCT). The results show some potential benefits of using PREP powder in laser direct metal Deposition. PREP powder has a higher Deposition rate and deposits show lower intralayer porosity and lower surface roughness. In both cases, deposits of Ti-6Al-4V exhibit a unique epitaxial prior beta grains microstructure that transforms to alpha lathes and retained beta during cooling. X-ray diffraction results show that the overall microstructure is alpha + beta and not martensitic. The lamellar alpha + beta phase spacing (S alpha+beta) increases with laser power but seems unaffected by variation in the mass flow rate of the powder. Micro hardness of the laser deposited Ti-6Al-4V is dependent on the lamellar alpha + beta phase spacing (S alpha+beta) and PREP powder deposits show lower micro hardness than GA powder deposits. (C) 2011 Elsevier B.V. All rights reserved.

Andrew J. Pinkerton - One of the best experts on this subject based on the ideXlab platform.

  • 2 World Congress on Integrated Computational Materials Engineering - A Coupled Approach to Weld Pool, Phase and Residual Stress Modelling of Laser Direct Metal Deposition (LDMD) Processes
    Proceedings of the 2nd World Congress on Integrated Computational Materials Engineering (ICME), 2013
    Co-Authors: Michael Vogel, Andrew J. Pinkerton, Mushtaq Khan, Juansethi Ibara-medina, Narcisse N’dri, Mustafa Megahed
    Abstract:

    This paper describes a complete CFD model of the laser metal Deposition process. The model covers the complete process, starting from the simulation of powder particles in the Deposition Head and finishing with the final part. Individual phenomena that are considered in the gas-phase stage of the model include the ricocheting of particles within the Head, the flow of powder particles, their interaction with the laser and powder catchment/bouncing. Phenomena considered in the liquid phase (melt pool) stage of the model include particle enthalpy effects, buoyancy, temperature-dependent material properties and Marangoni forces. The CFD model is coupled with a metallurgical database to predict the phase and material properties of the solidified deposit and heat affected area and residual stresses in the part. Modelled and experimental characteristics of multi-track deposits of M2 steel show good agreement.

  • A comparison of laser additive manufacturing using gas and plasma-atomized Ti-6A1-4V powders
    2012
    Co-Authors: M. Naveed Ahsan, Andrew J. Pinkerton, Laiq Ali
    Abstract:

    This research presents a comparative study of the characteristics of laser additive manufacturing (LAM) using two types of Ti-6A1-4V powder. Ti-6A1-4V powders prepared using the gas-atomization (GA) and the plasma rotating electrode (PREP) processes were first analyzed using laser diffraction, scanning electron microscopy and microcomputed tomography. A 1.5 kW diode laser with a coaxial Deposition Head was then used to deposit a number of thin-wall structures at a range of processing parameters from each of the powders. The deposited structures were characterized using optical microscopy, scanning electron microscopy, x-ray diffraction and microcomputed tomography (MicroCT). In both cases, deposits of Ti-6A1-4V exhibit a unique epitaxial prior beta grains microstructure that transforms to alpha lathes and retained beta during cooling. X-ray diffraction results show that the overall microstructure is alpha + beta. The lamellar alpha + beta phase spacing (S alpha+beta) increases with laser power but seems unaffected by variation in the powder mass flow rate. Micro hardness of the laser deposited Ti-6A1-4V is dependent on the lamellar a 0 phase spacing (S alpha+beta). The results show some potential benefits of using PREP powder in laser additive manufacturing. PREP powder has a higher Deposition rate and deposits show lower intralayer porosity and lower surface roughness. However, PREP powder deposits show lower micro hardness than GA powder deposits.

  • a comparative study of laser direct metal Deposition characteristics using gas and plasma atomized ti 6al 4v powders
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2011
    Co-Authors: Naveed M Ahsan, Andrew J. Pinkerton, R J Moat, Judith Shackleton
    Abstract:

    This research presents a comparative study of the characteristics of laser direct metal Deposition (LDMD) using two types of Ti-6Al-4V powder. Ti-6Al-4V powders prepared using the gas-atomization (GA) and the plasma rotating electrode (PREP) processes were first analyzed using laser diffraction, scanning electron microscopy and micro computed tomography. A 1.5 kW diode laser with a coaxial Deposition Head was then used to deposit a number of thin-wall structures at a range of processing parameters from each of the powders. The deposited structures were characterized using optical microscopy, scanning electron microscopy. X-ray diffraction and micro computed tomography (MicroCT). The results show some potential benefits of using PREP powder in laser direct metal Deposition. PREP powder has a higher Deposition rate and deposits show lower intralayer porosity and lower surface roughness. In both cases, deposits of Ti-6Al-4V exhibit a unique epitaxial prior beta grains microstructure that transforms to alpha lathes and retained beta during cooling. X-ray diffraction results show that the overall microstructure is alpha + beta and not martensitic. The lamellar alpha + beta phase spacing (S alpha+beta) increases with laser power but seems unaffected by variation in the mass flow rate of the powder. Micro hardness of the laser deposited Ti-6Al-4V is dependent on the lamellar alpha + beta phase spacing (S alpha+beta) and PREP powder deposits show lower micro hardness than GA powder deposits. (C) 2011 Elsevier B.V. All rights reserved.

  • A comparative study of laser direct metal Deposition characteristics using gas and plasma-atomized Ti–6Al–4V powders
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2011
    Co-Authors: M. Naveed Ahsan, Andrew J. Pinkerton, R J Moat, Judith Shackleton
    Abstract:

    This research presents a comparative study of the characteristics of laser direct metal Deposition (LDMD) using two types of Ti-6Al-4V powder. Ti-6Al-4V powders prepared using the gas-atomization (GA) and the plasma rotating electrode (PREP) processes were first analyzed using laser diffraction, scanning electron microscopy and micro computed tomography. A 1.5 kW diode laser with a coaxial Deposition Head was then used to deposit a number of thin-wall structures at a range of processing parameters from each of the powders. The deposited structures were characterized using optical microscopy, scanning electron microscopy. X-ray diffraction and micro computed tomography (MicroCT). The results show some potential benefits of using PREP powder in laser direct metal Deposition. PREP powder has a higher Deposition rate and deposits show lower intralayer porosity and lower surface roughness. In both cases, deposits of Ti-6Al-4V exhibit a unique epitaxial prior beta grains microstructure that transforms to alpha lathes and retained beta during cooling. X-ray diffraction results show that the overall microstructure is alpha + beta and not martensitic. The lamellar alpha + beta phase spacing (S alpha+beta) increases with laser power but seems unaffected by variation in the mass flow rate of the powder. Micro hardness of the laser deposited Ti-6Al-4V is dependent on the lamellar alpha + beta phase spacing (S alpha+beta) and PREP powder deposits show lower micro hardness than GA powder deposits. (C) 2011 Elsevier B.V. All rights reserved.

  • A CFD model of laser cladding: From Deposition Head to melt pool dynamics
    International Congress on Applications of Lasers & Electro-Optics, 2011
    Co-Authors: Juansethi Ibarra-medina, Michael Vogel, Andrew J. Pinkerton
    Abstract:

    The laser metal Deposition process continues to receive attention from researchers and industry due to its unique capabilities in applications such as surface coating or rapid manufacture. The development of numerical models has proven useful for improving the process. However, most models have focused on analyzing individual stages of the Deposition process and have required the introduction of a number of assumptions at their limits. This paper describes a complete CFD model that, starting from particles in the Deposition Head, simulates all interactions that govern the dynamics of a Deposition melt pool. Individual phenomena that are included in the gasphase stage of the model include the ricocheting of particles within the Head, the flow of powder particles, their interaction with the laser and powder catchment/bouncing. Phenomena in the liquid phase (melt pool) stage of the model include particle enthalpy effects, buoyancy, temperature-dependant material properties and Marangoni forces. The model is demonstrated using the actual geometry and gas flows found in a typical coaxial nozzle. The method, using a single technique to capture all phenomena, allows simulation of the melt pool dynamics from input parameters in a single model.

Luca Sorrentino - One of the best experts on this subject based on the ideXlab platform.

  • Manufacture of high performance isogrid structure by Robotic Filament Winding
    Composite Structures, 2017
    Co-Authors: Luca Sorrentino, Mario Marchetti, Costanzo Bellini, A. Delfini, F. Del Sette
    Abstract:

    Abstract Aeronautical and aerospace industries require light and robust structures. This target can be achieved designing isogrid structures made of composite material. In fact, such structures present both lightness and structural resistance. However, some problems can arise during the manufacturing process of these structures. In the present work the RFW (Robotic Filament Winding) technology is used for manufacturing an isogrid cylinder, made of composite material. The work was carried out in different steps. In the first, a suitable Deposition Head for fibres stratification was designed, then it was utilized to manufacture isogrid structures. Finally, both geometrical and structural tests were carried out on these structures and their results were compared with those one obtained from handmade structures. The comparison highlighted a better quality of the RFW structures. In fact, these structures complied with the geometrical tolerances, presented a lower void content and exhibited a higher resistance to axial compression load.

  • Robotized Filament Winding of Full Section Parts: Comparison Between Two Winding Trajectory Planning Rules
    Advanced Composite Materials, 2008
    Co-Authors: Luca Sorrentino, Luigi Carrino, Wilma Polini, E. Anamateros, G. Paris
    Abstract:

    Robotized filament winding technology involves a robot that winds a roving impregnated by resin on a die along the directions of stresses to which the work-piece is submitted in applications. The robot moves a Deposition Head along a winding trajectory in order to deposit roving. The trajectory planning is a very critical aspect of robotized filament winding technology, since it is responsible for both the tension constancy and the winding time. The present work shows two original rules to plan the winding trajectory of structural parts, whose shape is obtained by sweeping a full section around a 3D curve that must be closed and not crossing in order to assure a continuous winding. The first rule plans the winding trajectory by approximating the part 3D shape with straight lines; it is called the discretized rule. The second rule defines the winding trajectory simply by offsetting a 3D curve that reproduces the part 3D shape, of a defined distance; it is called the offset rule. The two rules have been com...

  • Requirement of Compactness Pressure Constancy During the Manufacturing of Not Axialsymmetric Components by Robotized Filament Winding
    Volume 4b: 11th Design for Manufacturing and the Lifecycle Conference, 2006
    Co-Authors: Luca Sorrentino, Wilma Polini
    Abstract:

    Robotized filament winding is a technology that involves an industrial robot placing fibres impregnated by resin along the directions of stresses the work-piece is subjected in exercise. It moves a Deposition Head along a winding trajectory in order to wind a tape impregnated by resin on a die. The winding tension is a very critical aspect of robotized filament winding, since it influences the compactness and the alignment of the fibres inside the composite material. The present paper underlines the problems connected to the lack of constancy of the compactness pressure during the winding of a tape on a die characterized by many different bending radii due to the complex geometry of the part to manufacture. This paper shows a study to set constant the value of the compactness pressure of the tape on the whole die. This means to assure in each point of the composite part the same value of density, percentages in volume of fibres and resin. By this study it has been possible to determine a model that is able to control in real time the tension to apply to the tape during winding or to design auxiliary devices to pre-compacting the tape on die, once deposited.Copyright © 2006 by ASME

  • Winding Time Reduction in Robotized Filament Winding: Winding Trajectory Planning by Die Boundary Offsetting
    Volume 4b: Design for Manufacturing and the Life Cycle Conference, 2005
    Co-Authors: Luca Sorrentino, Wilma Polini, Luigi Carrino
    Abstract:

    Robotized filament winding technology involves a robot that winds a roving impregnated by resin on a die along the directions of stresses the work-piece is submitted to in exercise. The robot moves a Deposition Head along a winding trajectory in order to deposit roving. The trajectory planning is a very critical aspect of robotized filament winding technology, since it is responsible for both the tension constancy and the winding time. The present work shows an original method to plan the winding trajectory of structural parts whose shape is obtained by sweeping a full section around a 3D closed not auto-intersecting curve. The trajectory is defined by offsetting this 3D curve of the distance needed to keep the tension on roving near to the value chosen to assure good mechanical performances of the manufactured composite parts. This trajectory allows to satisfy the constraints on the geometrical parameters of the winding trajectory (i.e. safety distance and winding angle) that assure to keep the value of tension near to the nominal one during winding. This means to assure an acceptable quality of the manufactured composite parts. Moreover, the planned trajectory allows to decrease strongly the winding time, when compared to the alternative methods of the trajectory planning.Copyright © 2005 by ASME

  • Design of Deposition Head Trajectory for Robotized Filament Winding of Complex Shape Parts
    Volume 3d: 8th Design for Manufacturing Conference, 2004
    Co-Authors: Wilma Polini, Luca Sorrentino
    Abstract:

    When the roving is winding on the die, the tension value may move away the nominal one that has been optimized by considering the quality and the mechanical properties of the wound composite parts. The variance of the tension value during winding from the nominal one strongly depends on the Deposition Head trajectory. The present work focuses on the planning of the winding trajectory for winding complex shape parts in composite material by a robotized cell. The planning of the winding trajectory should be based on the structural constraints of the robotized cell and on the technological requirements of the process. In particular, this work aims to study the conditions by which the value of the roving tension verges on the nominal one during winding. The developed planning logics and implemented by a CAD/CAM software have been validated by experimental tests. This work represents the first step towards the optimization of the winding trajectory.© 2004 ASME

Diane Carol Freeman - One of the best experts on this subject based on the ideXlab platform.

  • Oxide Electronics by Spatial Atomic Layer Deposition
    IEEE\ OSA Journal of Display Technology, 2009
    Co-Authors: David H Levy, Shelby Forrester Nelson, Diane Carol Freeman
    Abstract:

    We report on zinc oxide (ZnO)-based devices produced by a fast, open-air atomic layer Deposition (ALD) process relying upon the spatial isolation of reactive gases. At Deposition rates of greater than 100 Aring per minute, ZnO-based thin-film transistors by spatial atomic layer Deposition (S-ALD) show mobility above 15 cm2/Vs and excellent stability. Measurement and modeling of the gas isolation in the Deposition Head is discussed. Saturation curves obtained for aluminum oxide (Al2O3) growth using trimethylaluminum and water are shown to be consistent with chamber ALD systems. Finally, the ability of this new ALD process to leverage patterning by using poly(methyl methacrylate) (PMMA) as a growth inhibitor for selective area Deposition is discussed. Relatively thin films of PMMA (~ 40 Aring) are shown to be capable of inhibiting the growth of ZnO for at least 1200 ALD cycles.

David H Levy - One of the best experts on this subject based on the ideXlab platform.

  • Cycle time effects on growth and transistor characteristics of spatial atomic layer Deposition of zinc oxide
    Journal of Vacuum Science & Technology A: Vacuum Surfaces and Films, 2012
    Co-Authors: Shelby Forrester Nelson, David H Levy, Lee W. Tutt, Mitchell Stewart Burberry
    Abstract:

    The authors have investigated the effects on growth and on electrical characteristics of varying the cycle time for atomic layer deposited zinc oxide films. The samples are grown at atmospheric pressure. By using a spatial atomic layer Deposition Head, we can access both pulse and purge times as short as 0.025 s, which appears to be a regime that yields useful material properties. Shorter purge times allow higher growth rates at 200 °C and are correlated with both higher resistivity, better transistor gating, and higher thin-film-transistor mobility. The authors clarify that when comparing results, the purge time must be taken into account.

  • Oxide Electronics by Spatial Atomic Layer Deposition
    IEEE\ OSA Journal of Display Technology, 2009
    Co-Authors: David H Levy, Shelby Forrester Nelson, Diane Carol Freeman
    Abstract:

    We report on zinc oxide (ZnO)-based devices produced by a fast, open-air atomic layer Deposition (ALD) process relying upon the spatial isolation of reactive gases. At Deposition rates of greater than 100 Aring per minute, ZnO-based thin-film transistors by spatial atomic layer Deposition (S-ALD) show mobility above 15 cm2/Vs and excellent stability. Measurement and modeling of the gas isolation in the Deposition Head is discussed. Saturation curves obtained for aluminum oxide (Al2O3) growth using trimethylaluminum and water are shown to be consistent with chamber ALD systems. Finally, the ability of this new ALD process to leverage patterning by using poly(methyl methacrylate) (PMMA) as a growth inhibitor for selective area Deposition is discussed. Relatively thin films of PMMA (~ 40 Aring) are shown to be capable of inhibiting the growth of ZnO for at least 1200 ALD cycles.