63 research outputs found
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Investigation of the Oven Process in Indirect Metal Laser Sintering
This paper deals with the optimization of Indirect Metal Laser Sintering. Different experimental
analyses have proven that the oven process is highly responsible for the part distortion. By means
of polished micrograph sections and thermogravimetric and dilatometric investigations, the oven
process has been divided into four main steps: polymer removal, solid-state sintering, infiltration
and liquid-phase sintering.
Further experiments were carried out at higher temperature phases of the oven process, using
modified process parameters.
The aim of this research is to improve the knowledge about the oven process. In another step, this
process will be simulated by means of finite element analysis in order to minimize the part
distortion.Mechanical Engineerin
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Simulation of the Process Step Polymer Removal in Indirect Metal Laser Sintering
With the Indirect Metal Laser Sintering and by means of a heat treatment in an oven process
metal components can be produced. In the first step the polymer is transformed from the solid
state into the gas phase. This takes place all over the component at different velocities depending
on the local temperatures and temperature gradients. The creation of the gas phase develops a
pressure inside of the component because the diffusion of the polymer within the part has a finite
velocity. The pressure may contribute to a damage of the component. This essay deals with the
procedure to simulate the gas pressure on the basis of the implementation of kinetic models in the
Finite-Element-Analysis.Mechanical Engineerin
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Layer Formations in Electron Beam Sintering
Among direct metal processing manufacturing technologies (Rapid Manufacturing), Electron
Beam Sintering (EBS) exhibits a high application potential. Especially, the fast beam deflection
provided by electromagnetic lenses allows the realization of considerable building speeds and
minor residual stresses. Therefore, this paper aims to examine and utilize the given potential for
additive layer manufacturing. In this context, the deployed scanning strategy is a very important
aspect. By means of an increasing computer power, innovative and flexible patterns for the
solidification of the powder can be implemented. Thus, different patterns are being examined and
evaluated. Finally, occurring effects in the exposed zone are introduced.Mechanical Engineerin
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Transient Physical Effects in Electron Beam Sintering
The extensive use of the electron beam in manufacturing processes like welding or perforating
revealed the high potentials for also using it for solid freeform fabrication. First approaches like
feeding wire into a melt pool have successfully shown the technical feasibility. Among other
features, the electron beam exhibits high scanning speed, high power output, and beam density.
While in laser-based machines the fabrication is working in a stable way, transient physical
effects in the electron beam process can be observed, which still restrict process stability. For
instance, a high power input of the electron beam can result in sudden scattering of the metal
powder. The authors have developed an electron beam freeform fabrication system and examined
the above mentioned effects. Thus, the paper provides methods in order to identify, isolate and
avoid these effects, and to finally realize a reproducible process.Mechanical Engineerin
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Process Chain for Numerical Simulation of IMLS
Additive layer manufacturing methods imply, among other advantages, extensive flexibility
concerning their ability to realize mass customization. Despite various efforts towards process
enhancement, numerous deficiencies concerning part distortion or residual stresses are still
observable. The present work deals with the definition of an efficient process chain for
numerical simulation of indirect metal laser sintering (IMLS), in order to improve
dimensional accuracy. The underlying method is based on investigations of dilatometric behavior of iron based powder, which is integrated into reaction kinetic models and coupled
with a finite element analysis (FEA). Thus, singular process steps, e. g. solid phase sintering,
phase transformations or infiltration, are numerically modelled with adequate accuracy.
Referring to thermomechanical simulation, possibilities for pre-scaling of part geometries are
presented.Mechanical Engineerin
Towards Additively Manufactured Metamaterials with Powder Inclusions for Controllable Dissipation: The Critical Influence of Packing Density
Particle dampers represent a simple yet effective means to reduce unwanted
oscillations when attached to structural components. Powder bed fusion additive
manufacturing of metals allows to integrate particle inclusions of arbitrary
shape, size and spatial distribution directly into bulk material, giving rise
to novel metamaterials with controllable dissipation without the need for
additional external damping devices. At present, however, it is not well
understood how the degree of dissipation is influenced by the properties of the
enclosed powder packing. In the present work, a two-way coupled discrete
element - finite element model is proposed allowing for the first time to
consistently describe the interaction between oscillating deformable structures
and enclosed powder packings. As fundamental test case, the free oscillations
of a hollow cantilever beam filled with various powder packings differing in
packing density, particle size, and surface properties are considered to
systematically study these factors of influence. Critically, it is found that
the damping characteristics strongly depend on the packing density of the
enclosed powder and that an optimal packing density exists at which the
dissipation is maximized. Moreover, it is found that the influence of
(absolute) particle size on dissipation is rather small. First-order analytical
models for different deformation modes of such powder cavities are derived to
shed light on this observation
Processing Parameter Effects on Residual Stress and Mechanical Properties of Selective Laser Melted Ti6Al4V
Selective laser melting (SLM) process is characterized by large temperature gradients resulting in high levels of residual stress within the additively manufactured metallic structure. SLM-processed Ti6Al4V yields a martensitic microstructure due to the rapid solidification and results in a ductility generally lower than a hot working equivalent. Post-process heat treatments can be applied to SLM components to remove in-built residual stress and improve ductility. Residual stress buildup and the mechanical properties of SLM parts can be controlled by varying the SLM process parameters. This investigation studies the effect of layer thickness on residual stress and mechanical properties of SLM Ti6Al4V parts. This is the first-of-its kind study on the effect of varying power and exposure in conjunction with keeping the energy density constant on residual stress and mechanical properties of SLM Ti6Al4V components. It was found that decreasing power and increasing exposure for the same energy density lowered the residual stress and improved the % elongation of SLM Ti6Al4V parts. Increasing layer thickness resulted in lowering the residual stress at the detriment of mechanical properties. The study is based on detailed experimental analysis along with finite element simulation of the process using ABAQUS to understand the underlying physics of the process
The effect of additive geometry on the integration of secondary elements during Friction Stir Processing
Formation of a diffusion-based intermetallic interface layer in friction stir welded dissimilar Al-Cu lap joints
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