scholarly journals From the fatigue properties of Ti6Al4V produced by ALM selective laser melting process to the mechanical design of an aeronautical part

2020 ◽  
Vol 321 ◽  
pp. 03032
Author(s):  
François Edy ◽  
Viet-Duc LE ◽  
Claudia BIERE ◽  
Monica Perez ◽  
Etienne Pessard ◽  
...  
Keyword(s):  
Selective Laser Melting ◽  
Mechanical Design ◽  
Fatigue Behavior ◽  
Melting Process ◽  
Fatigue Behaviour ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Laser Melting ◽  
Fatigue Design ◽  
Process Strategy

Selective laser melting SLM is investigated through a study of redesign and characterization of an aeronautic part made of titanium Ti6Al4V. The part must ensure an excellent static and fatigue behaviour. The methodology developed hereby follows 3 main steps: First, the influence of laser power, laser speed and hatch distance on the amount/rate of porosity is performed to define optimized process parameters. Then, the influence of building process strategy, i.e. building direction or as-built surface roughness on the static and fatigue behaviour are studied and understood by following a vast experimental campaign. Obtained properties are finally used in a topology optimization study to find the best compromise between part weight and fatigue behavior . 3 prototypes of simulated part are produced and then characterized. Fatigue tests are conducted on the component and confirm the fatigue design proposed. Obtained results are encouraging and illustrate the fatigue design optimization of a complex Additive Manufacturing component.

Effects of Building Orientation on Fatigue Behavior of Ti-6Al-4V Alloy Produced by Selective Laser Melting

2019 ◽  
Vol 795 ◽  
pp. 208-214 ◽  
Author(s):  
Rui Da Xu ◽  
Hui Chen Yu
Keyword(s):  
Selective Laser Melting ◽  
Surface Defects ◽  
Fatigue Behavior ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Layer By Layer ◽  
Laser Melting ◽  
Material Deposition ◽  
Stress Ratios ◽  
The Impact

Addictive manufacturing (AM) allows for the layer-by-layer fabrication of components via sequential material deposition and it is of immediate interest in many applications, in particularly aviation field. This work is tackling the issue that the influence of the inner-defects and building orientations on the fatigue behavior of Ti-6Al-4V Alloys produced by Selective Laser Melting (SLM). Specimens were built in two orientations (horizontal and vertical to the substrate) in order to evaluate the impact of the induced anisotropy of fatigue properties. A series of fatigue tests at five stress ratios ranged from-1 to 0.8 are conducted at 400°C. Scanning Electron Microscopy (SEM) is used to examine the fracture surfaces of fatigue specimens to qualify the failure mechanism and crack initiation sites, which are most likely attached to the surface defects. The fracture surface analysis of HCF specimen tested at two temperatures reveals that near 85% of the crack initiates from the defect under subsurface. The results of this study imply that the fatigue properties at 400°C are highly dependent on the specimen orientations relative to build directions, as the defects close to surface are the mainly cause of the crack initiations.

The Effect of Manufacturing Defects on the Fatigue Behaviour of Ti-6Al-4V Specimens Fabricated Using Selective Laser Melting

2014 ◽  
Vol 891-892 ◽  
pp. 1519-1524 ◽  
Author(s):  
Qian Chu Liu ◽  
Joe Elambasseril ◽  
Shou Jin Sun ◽  
Martin Leary ◽  
Milan Brandt ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fatigue Life ◽  
Selective Laser Melting ◽  
Fatigue Crack Initiation ◽  
Fatigue Behaviour ◽  
Fatigue Tests ◽  
Metallic Materials ◽  
Laser Melting ◽  
Manufacturing Defects ◽  
Materials Properties

Additive Manufacturing (AM) technologies are considered revolutionary because they could fundamentally change the way products are designed. Selective Laser Melting (SLM) is a metal based AM process with significant and growing potential for the manufacture of aerospace components. Traditionally a material needs to be listed in the Metallic Materials Properties Development and Standardization (MMPDS) handbook if it is to be considered certified. However, this requires a considerable amount of test data to be generated on the materials mechanical properties. Therefore, the MMPDS certification process does not lend itself easily to the certification of AM components as the final component can have similar mechanical properties to wrought alloys combined with the defects associated with traditional casting and welding technologies. These defects can substantially decrease the fatigue life of a fabricated component. The primary purpose of this investigation was to study the fatigue behaviour of as-built Ti-6Al-4V (Ti64) samples. Fatigue tests were performed on the Ti-6Al-4V specimens built using SLM with a variety of layer thicknesses and build (vertical or horizontal) directions. Fractography revealed the presence of a range of manufacturing defects located at or near the surface of the specimens. The experimental results indicated that Lack-of-Fusion (LOF) defects were primarily responsible for fatigue crack initiation. The reduction in fatigue life appeared to be affected by the location, size and shape of the LOF defect.

Low-Cycle-Fatigue Properties of a 17-4 PH Stainless Steel Manufactured via Selective Laser Melting

2021 ◽  
Vol 877 ◽  
pp. 55-60
Author(s):  
Lorenzo Maccioni ◽  
Eleonora Rampazzo ◽  
Filippo Nalli ◽  
Yuri Borgianni ◽  
Franco Concli
Keyword(s):  
Stainless Steel ◽  
Selective Laser Melting ◽  
Low Cycle Fatigue ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Cycle Fatigue ◽  
Laser Melting ◽  
Softening Behavior ◽  
The One ◽  
Cylindrical Samples

In this paper, the static and low-cycle-fatigue (LCF) behavior of wrought samples of 17-4 PH stainless steel (SS) manufactured via Selective Laser Melting (SLM) are presented. On the one hand, several scholars have studied SLM materials and literature reports a huge amount of data as for the high-cycle-fatigue (HCF) behavior. On the other hand, few are the data available on the LCF behavior of those materials. The aim of the present research is to provide reliable data for an as-build 17-4 PH steel manufactured via SLM techniques. Only with quantitative data, indeed, it is possible to exploit all the advantages that this technology can offer. In this regard, both quasi-static (QS) and low-cycle-fatigue tests were performed on Additive Manufacturing (AM) cylindrical samples. Through QS tests, the constitutive low has been defined. Strain-controlled fatigue tests on an electromechanical machine were performed on 12 samples designed according to the ASTM standard. Tests were continued also after the stabilization was reached (needed for the cyclic curve described with the Ramberg-Osgood equation) to obtain also the fatigue (ε-N) curve. Results show that the material has a softening behavior. The Basquin-Coffin-Manson (BCM) parameters were tuned on the basis of the ε-N combinations after rupture.

scholarly journals Influences of Horizontal and Vertical Build Orientations and Post-Fabrication Processes on the Fatigue Behavior of Stainless Steel 316L Produced by Selective Laser Melting

Materials ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4203 ◽  
Author(s):  
Paul Wood ◽  
Tomasz Libura ◽  
Zbigniew L. Kowalewski ◽  
Gavin Williams ◽  
Ahmad Serjouei
Keyword(s):  
Stainless Steel ◽  
Selective Laser Melting ◽  
Shot Peening ◽  
Fatigue Behavior ◽  
Fracture Pattern ◽  
Fatigue Properties ◽  
Stainless Steel 316L ◽  
Laser Melting ◽  
Test Pieces ◽  
Laser Systems

In this paper, the influences of build orientation and post-fabrication processes, including stress-relief, machining, and shot-peening, on the fatigue behavior of stainless steel (SS) 316L manufactured using selective laser melting (SLM) are studied. It was found that horizontally-built (XY) and machined (M) test pieces, which had not been previously studied in the literature, in both stress-relieved (SR) or non-stress-relieved (NSR) conditions show superior fatigue behavior compared to vertically-built (ZX) and conventionally-manufactured SS 316L. The XY, M, and SR (XY-M-SR) test pieces displayed fatigue behavior similar to the XY-M-NSR test pieces, implying that SR does not have a considerable effect on the fatigue behavior of XY and M test pieces. ZX-M-SR test pieces, due to their considerably lower ductility, exhibited significantly larger scatter and a lower fatigue strength compared to ZX-M-NSR samples. Shot-peening (SP) displayed a positive effect on improving the fatigue behavior of the ZX-NSR test pieces due to a compressive stress of 58 MPa induced on the surface of the test pieces. Fractography of the tensile and fatigue test pieces revealed a deeper understanding of the relationships between the process parameters, microstructure, and mechanical properties for SS 316L produced by laser systems. For example, fish-eye fracture pattern or spherical stair features were not previously observed or explained for cyclically-loaded SLM-printed parts in the literature. This study provides comprehensive insight into the anisotropy of the static and fatigue properties of SLM-printed parts, as well as the pre- and post-fabrication parameters that can be employed to improve the fatigue behavior of steel alloys manufactured using laser systems.

Correlation of Fatigue Limit and Crack Growth Threshold Value to the Nanobainitic Microstructure

2016 ◽  
Vol 258 ◽  
pp. 314-317 ◽  
Author(s):  
Inga Müller ◽  
Rosalia Rementeria ◽  
Francisca G. Caballero ◽  
Matthias Kuntz ◽  
Eberhard Kerscher
Keyword(s):  
Crack Growth ◽  
Fatigue Limit ◽  
Fatigue Behavior ◽  
Bainitic Ferrite ◽  
Block Size ◽  
Threshold Value ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Microstructural Parameters ◽  
Fatigue Design

The recently developed nanobainitic steels show high ultimate tensile strength (UTS) as well as high ductility. Although this combination seems to be desirable for fatigue design, fatigue limit of nanostructured bainite is often disappointingly low. To improve fatigue properties we tried to earn a fundamental understanding of the microstructural parameters governing fatigue behavior.Therefore our hypothesis to improve the fatigue behavior was not necessarily avoiding the initiation of a fatigue crack – which could lead to failure of the material – but to improve the ability of the present microstructure to slow down or stop growing cracks. Thus, the key to understand the fatigue behavior of nanostructured bainite is to understand the role of the microstructural features which could act as barriers for growing cracks.We tried to correlate our results of fatigue tests and analysis of fracture surfaces to the size of microstructural features like bainitic ferrite plates, crystallographic bainite blocks and packets or prior austenite grains, as well as cracks induced at nonmetallic inclusions. Thereby we found that the crystallographic bainite block size governs fatigue behavior. Additionally, threshold values were determined from crack growth experiments and related to the characteristic microstructural features.

Toward Structural Fatigue Analysis of Horizontally-Fabricated NiTi via Selective Laser Melting

2020 ◽  
Author(s):  
Parisa Bayati ◽  
Ahmadreza Jahadakbar ◽  
Keyvan Safaie ◽  
Mohammadreza Nematollahi ◽  
Hediyeh Dabbaghi ◽  
...  
Keyword(s):  
Shape Memory ◽  
Selective Laser Melting ◽  
Initial Step ◽  
Fatigue Behaviour ◽  
Fatigue Tests ◽  
Laser Melting ◽  
Practical Applications ◽  
Structural Fatigue ◽  
Dog Bone ◽  
Potential Applications

Abstract NiTi (Nitinol) is a shape memory alloy with distinctive properties, such as shape memory, superelasticity, biocompatibility, and low density. All these unique properties make NiTi a great candidate in different applications. However, the conventional fabrication of NiTi encounters many challenges that significantly limits the practical applications of the alloy. As a solution, the Selective Laser Melting (SLM) which is an Additive Manufacturing (AM) technique has been recently used for the fabrication of NiTi parts. Although complex geometries can be fabricated directly from CAD files via SLM, different process parameters significantly affect the parts’ quality and must be optimized for each application. In most of the potential applications, NiTi components undergo cyclic loads and therefore its structural fatigue must be fully studied and considered in the design process. However, due to the nature of the SLM process, the fatigue behaviour of SLM fabricated NiTi is different from the conventional ones. In this work, as an initial step, the fatigue behaviour of the SLM fabricated NiTi in the horizontal direction is studied and the reasons for failure have been discussed. To this end, strain-controlled fatigue tests were performed on NiTi dog-bone samples, and fractography was used to analyze the different defects which could cause the failure or scatter in the results.

scholarly journals Improving surface quality in selective laser melting based tool making

2021 ◽  
Author(s):  
Filippo Simoni ◽  
Andrea Huxol ◽  
Franz-Josef Villmer
Keyword(s):  
Surface Roughness ◽  
Additive Manufacturing ◽  
Surface Quality ◽  
Selective Laser Melting ◽  
Melting Process ◽  
Laser Remelting ◽  
Laser Melting ◽  
Great Cost ◽  
Starting Point ◽  
Processing Techniques

AbstractIn the last years, Additive Manufacturing, thanks to its capability of continuous improvements in performance and cost-efficiency, was able to partly replace and redefine well-established manufacturing processes. This research is based on the idea to achieve great cost and operational benefits especially in the field of tool making for injection molding by combining traditional and additive manufacturing in one process chain. Special attention is given to the surface quality in terms of surface roughness and its optimization directly in the Selective Laser Melting process. This article presents the possibility for a remelting process of the SLM parts as a way to optimize the surfaces of the produced parts. The influence of laser remelting on the surface roughness of the parts is analyzed while varying machine parameters like laser power and scan settings. Laser remelting with optimized parameter settings considerably improves the surface quality of SLM parts and is a great starting point for further post-processing techniques, which require a low initial value of surface roughness.

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