Investigation of Residual Stresses in Selective Laser Melting

2014 ◽  
Vol 627 ◽  
pp. 129-132 ◽  
Author(s):  
L. Parry ◽  
I. Ashcroft ◽  
D. Bracket ◽  
R.D. Wildman
Keyword(s):  
Residual Stress ◽  
Selective Laser Melting ◽  
Processing Method ◽  
Laser Melting ◽  
Manufacturing Method ◽  
Part Geometry ◽  
Part Distortion ◽  
Manufacturing Methods ◽  
Traditional Manufacturing ◽  
Metallic Parts

Selective Laser Melting (SLM) is an Additive Manufacturing method that enables greater design freedoms than traditional manufacturing methods in the production of high value, low volume metallic parts. Despite this now being a well-established processing method, there are a number of issues impeding industrial uptake, including the generation of residual stress and part distortion during manufacture. Prediction of residual stress is invaluable for tuning process parameters, and optimising the part geometry and support structures to limit residual stress based distortion during manufacture. This paper establishes a thermal modelling strategy to predict temperature distribution within a 3D SLM part that is a precursor towards a residual stress analysis.

A Short Glance on Metal 3D AM

2018 ◽  
Vol 786 ◽  
pp. 348-355
Author(s):  
Terho Iso-Junno ◽  
Kimmo Mäkelä ◽  
Kari Mäntyjärvi ◽  
Tero Jokelainen
Keyword(s):  
Additive Manufacturing ◽  
Selective Laser Melting ◽  
Future Development ◽  
Cost Efficiency ◽  
Holistic Approach ◽  
Production Method ◽  
Digital Manufacturing ◽  
Laser Melting ◽  
Manufacturing Method ◽  
Manufacturing Methods

Metal 3D AM (Additive Manufacturing) has been becoming a more common production method for larger variety of parts. In this review the current situation and future development trends of the 3D metal AM are presented, concentrating on the SLM (Selective Laser Melting) technology. A holistic approach to the AM as a digital manufacturing method is presented and different manufacturing aspects of the AM production are identified. The most promising aspects for the future development are the automatization of the AM design tasks and automatization of the production. With the development of these aspects the production and cost efficiency of the metal AM can be increased to a more competitive level compared with other manufacturing methods.

Experimental Investigation of Selective Laser Melting of Lunar Regolith for In-Situ Applications

2013 ◽  
Author(s):  
Miranda Fateri ◽  
Andreas Gebhardt ◽  
Maziar Khosravi
Keyword(s):  
Selective Laser Melting ◽  
Laser Power ◽  
Lunar Regolith ◽  
Laser Melting ◽  
Manufacturing Method ◽  
3D Objects ◽  
Scan Speed ◽  
Manufacturing Methods ◽  
Object Layer

Selective Laser Melting (SLM) is a powder based Additive manufacturing (AM) technology which builds an object layer wise using a laser beam to melt the powder on an elevated platform. Thus far numerous studies have investigated lunar manufacturing methods and construction but little is known about applicability of SLM of lunar regolith. As most lunar construction proposals require transportation of essential materials from Earth, using an in-situ manufacturing method with indigenous material would be considerably more economical. Fabrication of parts with SLM using various metals and ceramics has already been presented. As such, the feasibility of using lunar regolith mixture to create functional parts with SLM process is investigated. Variation of process parameters such as laser power, scan speed, and scan strategies is investigated and multiple 3D objects are successfully created and presented.

On the Simulation Scalability of Predicting Residual Stress and Distortion in Selective Laser Melting

2018 ◽  
Vol 140 (4) ◽  
Author(s):  
C. Li ◽  
Z. Y. Liu ◽  
X. Y. Fang ◽  
Y. B. Guo
Keyword(s):  
Residual Stress ◽  
Layer Thickness ◽  
Selective Laser Melting ◽  
Laser Scanning ◽  
Rapid Heating ◽  
Stress Gradient ◽  
Computational Cost ◽  
Critical Issue ◽  
Laser Melting ◽  
Part Distortion

Rapid heating and cooling thermal cycle of metals in selective laser melting (SLM) generates high tensile residual stress which leads to part distortion. However, how to fast and accurately predict residual stress and the resulted part distortion remains a critical issue. It is not practical to simulate every single laser scan to build up a functional part due to the exceedingly high computational cost. Therefore, scaling up the material deposition rate via increasing heat source dimension and layer thickness would dramatically reduce the computational cost. In this study, a multiscale scalable modeling approach has been developed to enable fast prediction of part distortion and residual stress. Case studies on residual stress and distortion of the L-shaped bar and the bridge structure were presented via the deposition scalability and validation with the experimental data. High residual stress gradient in the building direction was found from high tensile on the surface to high compressive in the core. The part distortion can be predicted with reasonable accuracy when the block thickness is scaled up by 50 times the layer thickness from 30 μm to 1500 μm. The influence of laser scanning strategy on residual stress distribution and distortion magnitude of the bridges has shown that orthogonal scanning pattern between two neighboring block layers is beneficial for reducing part distortion.

scholarly journals Additive Manufactured 316L Stainless-Steel Samples: Microstructure, Residual Stress and Corrosion Characteristics after Post-Processing

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 182
Author(s):  
Suvi Santa-aho ◽  
Mika Kiviluoma ◽  
Tuomas Jokiaho ◽  
Tejas Gundgire ◽  
Mari Honkanen ◽  
...  
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Sample Surface ◽  
Post Processing ◽  
Magnesium Chloride Solution ◽  
Manufacturing Method ◽  
Four Point Bending ◽  
Traditional Manufacturing ◽  
Processing Steps ◽  
Compressive Residual Stresses

Additive manufacturing (AM) is a relatively new manufacturing method that can produce complex geometries and optimized shapes with less process steps. In addition to distinct microstructural features, residual stresses and their formation are also inherent to AM components. AM components require several post-processing steps before they are ready for use. To change the traditional manufacturing method to AM, comprehensive characterization is needed to verify the suitability of AM components. On very demanding corrosion atmospheres, the question is does AM lower or eliminate the risk of stress corrosion cracking (SCC) compared to welded 316L components? This work concentrates on post-processing and its influence on the microstructure and surface and subsurface residual stresses. The shot peening (SP) post-processing levelled out the residual stress differences, producing compressive residual stresses of more than −400 MPa in the AM samples and the effect exceeded an over 100 µm layer below the surface. Post-processing caused grain refinement and low-angle boundary formation on the sample surface layer and silicon carbide (SiC) residue adhesion, which should be taken into account when using the components. Immersion tests with four-point-bending in the heated 80 °C magnesium chloride solution for SCC showed no difference between AM and reference samples even after a 674 h immersion.

Deformations and stresses prediction of cantilever structures fabricated by selective laser melting process

2021 ◽  
Vol 27 (3) ◽  
pp. 453-464
Author(s):  
Lan Li ◽  
Tan Pan ◽  
Xinchang Zhang ◽  
Yitao Chen ◽  
Wenyuan Cui ◽  
...  
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Selective Laser Melting ◽  
Thermal Distortion ◽  
Cantilever Beams ◽  
Support Structures ◽  
Laser Melting ◽  
Content Type ◽  
Two Samples ◽  
Validation Experiments

Purpose During the powder bed fusion process, thermal distortion is one big problem owing to the thermal stress caused by the high cooling rate and temperature gradient. For the purpose of avoiding distortion caused by internal residual stresses, support structures are used in most selective laser melting (SLM) process especially for cantilever beams because they can assist the heat dissipation. Support structures can also help to hold the work piece in its place and reduce volume of the printing materials. The mitigation of high thermal gradients during the manufacturing process helps to reduce thermal distortion and thus alleviate cracking, curling, delamination and shrinkage. Therefore, this paper aims to study the displacement and residual stress evolution of SLMed parts. Design/methodology/approach The objective of this study was to examine and compare the distortion and residual stress properties of two cantilever structures, using both numerical and experimental methods. The part-scale finite element analysis modeling technique was applied to numerically analyze the overhang distortions, using the layer-by-layer model for predicting a part scale model. The validation experiments of these two samples were built in a SLM platform. Then average displacement of the four tip corners and residual stress on top surface of cantilever beams were tested to validate the model. Findings The validation experiments results of average displacement of the four tip corners and residual stress on top surface of cantilever beams were tested to validate the model. It was found that they matched well with each other. From displacement and residual stress standpoint, by introducing two different support structure, two samples with the same cantilever beam can be successfully printed. In terms of reducing wasted support materials, print time and high surface quality, sample with less support will need less post-processing and waste energy. Originality/value Numerical modeling in this work can be a very useful tool to parametrically study the feasibility of support structures of SLM parts in terms of residual stresses and deformations. It has the capability for fast prediction in the SLMed parts.

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