scholarly journals Study on the origins of residual stresses in Ti-6Al-4V processed by additive manufacturing

2020 ◽  
Vol 321 ◽  
pp. 03001
Author(s):  
Nathan Dumontet ◽  
Benoit Malard ◽  
Bernard Viguier
Keyword(s):  
Additive Manufacturing ◽  
Energy Density ◽  
Residual Stresses ◽  
Dwell Time ◽  
Scanning Speed ◽  
Manufacturing Processes ◽  
Thermal Gradients ◽  
Laser Beam Melting ◽  
Reliable Parameter ◽  
Stress States

In additive manufacturing processes using laser beam melting high thermal gradients are generated, inducing residual stresses within the parts that may lead to deformations and, in worst cases, cracks. One of the materials that is the most sensitive to residual stresses is the Ti-6Al-4V alloy. In the present study, we focus on the various parameters that may control the genesis and build-up of the residual stress states. Dwell time and thermal conductivity, both influencing the heat evacuation, were studied. Higher thermal evacuation was find to rises residual stresses within the part. Then, the reliability of the energy density as a comparison parameter was investigated. Samples with the same energy densities but different power and scanning speed were elaborated. Energy density was shown as a non-reliable parameter to compare different processed parts.

scholarly journals Residual Stresses Control in Additive Manufacturing

2021 ◽  
Vol 5 (4) ◽  
pp. 138
Author(s):  
Xufei Lu ◽  
Miguel Cervera ◽  
Michele Chiumenti ◽  
Xin Lin
Keyword(s):  
Additive Manufacturing ◽  
Residual Stresses ◽  
Thermal Deformation ◽  
Element Model ◽  
Thermal Gradients ◽  
Part Geometry ◽  
The Core ◽  
Optimal Processing ◽  
Scan Pattern ◽  
Metal Additive

Residual stresses are one of the primary causes for the failure of parts or systems in metal additive manufacturing (AM), since they easily induce crack propagation and structural distortion. Although the formation of residual stresses has been extensively studied, the core factors steering their development in AM have not been completely uncovered. To date, several strategies based on reducing the thermal gradients have been developed to mitigate the manifestation of residual stresses in AM; however, how to choose the optimal processing plan is still unclear for AM designers. In this regard, the concept of the yield temperature, related to the thermal deformation and the mechanical constraint, plays a crucial role for controlling the residual stresses, but it has not been duly investigated, and the corresponding approach to control stresses is also yet lacking. To undertake such study, a three-bar model is firstly used to illustrate the formation mechanism of the residual stress and its key causes. Next, an experimentally calibrated thermomechanical finite element model is used to analyze the sensitivity of the residual stresses to the scan pattern, preheating, energy density, and the part geometry and size, as well as the substrate constraints. Based on the numerical results obtained from this analysis, recommendations on how to minimize the residual stresses during the AM process are provided.

scholarly journals Effect of Process Parameters on Residual Stresses, Distortions, and Porosity in Selective Laser Melting of Maraging Steel 300

Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1042 ◽  
Author(s):  
Mugwagwa ◽  
Yadroitsev ◽  
Matope
Keyword(s):  
Residual Stress ◽  
Additive Manufacturing ◽  
Residual Stresses ◽  
Maraging Steel ◽  
Selective Laser Melting ◽  
Input Parameter ◽  
Scanning Speed ◽  
Metal Powders ◽  
Laser Melting ◽  
Widespread Application

Selective laser melting (SLM) is one of the most well-known additive manufacturing methods available for the fabrication of functional parts from metal powders. Although SLM is now an established metal additive manufacturing technique, its widespread application in industry is still hindered by inherent phenomena, one of which is high residual stresses. Some of the effects of residual stresses – such as warping and thermal stress-related cracking – cannot be corrected by post processing. Therefore, establishing input process parameter combinations that result in the least residual stress magnitudes and related distortions and/or cracking is critical. This paper presents the influence of laser power, scanning speed, and layer thickness on residual stresses, distortions and achievable density for maraging steel 300 steel parts in order to establish the most optimum input parameter combinations. An analysis of the interdependence between process outcomes shows that high residual stress magnitudes lead to high dimensional distortions in the finished parts, whilst porous parts suffer relatively lower residual stresses and associated distortions.

Fräsbearbeitung von Additivbauteilen*/Milling of additively manufactured parts – post-processing potential for automation of additively manufactured serial parts

2019 ◽  
Vol 109 (06) ◽  
pp. 423-428
Author(s):  
C. Häußinger ◽  
M.F. Zäh
Keyword(s):  
Additive Manufacturing ◽  
Manufacturing Processes ◽  
Process Chain ◽  
Post Processing ◽  
High Quality ◽  
Additive Fertigung ◽  
Lightweight Structures ◽  
Laser Beam Melting ◽  
Functional Components ◽  
Efficient Realization

Die Additive Fertigung mittels Laser-Strahlschmelzen eröffnet in Bezug auf Leichtbaukonstruktionen viele Möglichkeiten. Um qualitativ hochwertige Funktionsbauteile zu fertigen, ist jedoch in den meisten Fällen eine spanende Nachbearbeitung erforderlich. Zu deren produktiver Umsetzung wurde im Rahmen des vorliegenden Beitrags eine Prozesskette am Beispiel des Fräsens definiert. Sie wurde zudem auf ihr Automatisierungspotenzial hin analysiert und an ausgewählten Prozessbausteinen wurden Automatisierungsmaßnahmen umgesetzt.   Additive manufacturing processes like laser beam melting enable many possibilities due to lightweight structures. However, a post-processing is necessary in most cases to produce high quality functional components. A process chain was developed for an efficient realization of the post-processing by milling. This process chain was analyzed for automation potentials and selected process modules were automated.

scholarly journals Additive Manufacturing Under Lunar Gravity and Microgravity

2021 ◽  
Vol 33 (2) ◽  
Author(s):  
B. Reitz ◽  
C. Lotz ◽  
N. Gerdes ◽  
S. Linke ◽  
E. Olsen ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Spare Parts ◽  
Manufacturing Processes ◽  
Complex Structures ◽  
Lunar Gravity ◽  
Limited Extent ◽  
Test Environment ◽  
Manufacturing Tests ◽  
Laser Experiments ◽  
Materials Used

AbstractMankind is setting to colonize space, for which the manufacturing of habitats, tools, spare parts and other infrastructure is required. Commercial manufacturing processes are already well engineered under standard conditions on Earth, which means under Earth’s gravity and atmosphere. Based on the literature review, additive manufacturing under lunar and other space gravitational conditions have only been researched to a very limited extent. Especially, additive manufacturing offers many advantages, as it can produce complex structures while saving resources. The materials used do not have to be taken along on the mission, they can even be mined and processed on-site. The Einstein-Elevator offers a unique test environment for experiments under different gravitational conditions. Laser experiments on selectively melting regolith simulant are successfully conducted under lunar gravity and microgravity. The created samples are characterized in terms of their geometry, mass and porosity. These experiments are the first additive manufacturing tests under lunar gravity worldwide.

scholarly journals An Additively Manufactured Titanium Alloy in the Focus of Metallography

2021 ◽  
Vol 58 (1) ◽  
pp. 4-31
Author(s):  
C. Fleißner-Rieger ◽  
T. Pogrielz ◽  
D. Obersteiner ◽  
T. Pfeifer ◽  
H. Clemens ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Microstructural Analysis ◽  
Microstructural Characterization ◽  
Melting Process ◽  
Manufacturing Processes ◽  
Ingot Metallurgy ◽  
Lightweight Structures ◽  
Metallographic Preparation ◽  
Fine Structures ◽  
Specific Material

Abstract Additive manufacturing processes allow the production of geometrically complex lightweight structures with specific material properties. However, by contrast with ingot metallurgy methods, the manufacture of components using this process also brings about some challenges. In the field of microstructural characterization, where mostly very fine structures are analyzed, it is thus indispensable to optimize the classic sample preparation process and to furthermore implement additional preparation steps. This work focuses on the metallography of additively manufactured Ti‑6Al‑4V components produced in a selective laser melting process. It offers a guideline for the metallographic preparation along the process chain of additive manufacturing from the metal powder characterization to the macro- and microstructural analysis of the laser melted sample. Apart from developing preparation parameters, selected etching methods were examined with regard to their practicality.

The Compliance Method for Measurement of Near Surface Residual Stresses—Analytical Background

1994 ◽  
Vol 116 (4) ◽  
pp. 550-555 ◽  
Author(s):  
M. Gremaud ◽  
W. Cheng ◽  
I. Finnie ◽  
M. B. Prime
Keyword(s):  
Numerical Simulation ◽  
Residual Stresses ◽  
Random Errors ◽  
Residual Stress Field ◽  
Near Surface ◽  
Surface Residual Stresses ◽  
Zero Shift ◽  
Stress States ◽  
The Stability ◽  
Piecewise Functions

Introducing a thin cut from the surface of a part containing residual stresses produces a change in strain on the surface. When the strains are measured as a function of the depth of the cut, residual stresses near the surface can be estimated using the compliance method. In previous work, the unknown residual stress field was represented by a series of continuous polynomials. The present paper shows that for stress states with steep gradients, superior predictions are obtained by using “overlapping piecewise functions” to represent the stresses. The stability of the method under the influence of random errors and a zero shift is demonstrated by numerical simulation.

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