Anisotropy of Mechanical Properties and Residual Stress in Additively Manufactured 316L Specimens

Fedorenko, Alexey; Fedulov, Boris; Kuzminova, Yulia O.; Evlashin, Stanislav A.; Staroverov, Oleg; Tretyakov, M. P.; Ломакин, Е. В.; Akhatov, Iskander

doi:10.3390/ma14237176

Cited by 25 publications

(9 citation statements)

References 47 publications

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“…Various materials undergo postcritical deformation: metals [ 15 , 16 , 17 ], rocks [ 18 , 19 ], concretes [ 20 , 21 , 22 ], polymer composites [ 23 , 24 , 25 ], etc. In addition, the softening effect is observed in the in-plane shear response of polymer composites [ 26 , 27 , 28 , 29 ].…”

Section: Introductionmentioning

confidence: 99%

Stability of Postcritical Deformation of CFRP under Static ±45° Tension with Vibrations

et al. 2022

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The paper presents an experimental study on regularities of postcritical deformation of carbon-fiber-reinforced plastic (CFRP) under static ±45° tension. The employed test method is based on ASTM D3518. Displacement and strain fields were identified by a digital image correlation method (DIC) using a VIC-3D contactless optical video system. Acoustic emission signals were obtained using an AMSY-6 system. The surface analysis of samples was carried out using a CarlZeiss SteREO Discovery. V12 optical stereomicroscope and a DinoLite microscope. Three experimental test types were considered: active loading, deformation with unloadings, and tension under additional torsion vibrations with various amplitudes. Loading diagrams were constructed; they showed a number of stages in the damage accumulation process. It was analyzed how heterogeneous strain fields develop; a neck development during softening process was observed. It was noted that the loading system rigidity influences the failure moment. The research considered various shear strain calculation methods using a “virtual extensometer” instrument. Composite mechanical properties were obtained. A shear modulus reduction during a plastic strain increase was revealed. The acoustic emission signals were analyzed; three characteristic frequency bands were observed. Most of the contribution to cumulative energy was made by matrix cracking. A reduction of the number of AE signals associated with the violation of adhesion between the fibers and the matrix during postcritical deformation was observed. The research identified basic surface defects. An appearance of the defects corresponds with their identification by the AE system. It was revealed that the presence of additional torsion vibration leads to an increase in the softening stage length. It was concluded that due regard for the postcritical deformation stage and the loading system rigidity is reasonable during the structure strength analysis.

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Section: Introductionmentioning

confidence: 99%

Stability of Postcritical Deformation of CFRP under Static ±45° Tension with Vibrations

et al. 2022

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“…3 a) that the microstructure and grains of specimens fabricated in 0° orientation are stretched in the build direction and perpendicular to the compression direction, respectively. This results in anisotropy, with specimens fabricated in 0° orientation having lower tensile strength than those fabricated in 90° orientation [29]. Relative to the same specimen cross-section, the specimens printed in 90° orientation exhibit a more spherical grain structure regarding the x-y-plane.…”

Section: Resultsmentioning

confidence: 99%

Application of the plane-strain-compression-test to determine the local mechanical properties of LPBF-manufactured 316l components

Jensch

2023

Materials Research Proceedings

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Abstract. In the Laser Powder Bed Fusion (LPBF) process for metal components, a CAD file is sliced into layers with a thickness of 20-80 micrometers and the component is built up layer by layer. For this purpose, a metal powder layer is applied in each case and melted locally. This process is repeated until the geometry is completely established. The mechanical properties of the manufactured part are controlled by the cooling rate. It is currently not considered in the design of LPBF components, that the printed part has a varying heat flow into the surrounding powder and into the support plate depending on its slenderness. As a result of the different temperature histories, different microstructures with correspondingly different mechanical properties are formed in the untreated state (as-built). These differences must be considered in the component design. In this work, walls of various thicknesses were produced from 316L stainless-steel alloy using the LPBF process. The walls could be used to create plane-strain-compression-test specimens of various heights and orientations. The tests were performed according to Graf et al. [1] and the flow curve was calculated from the force-displacement curve while taking friction into account. Following that, tensile strength, Young’s modulus, yield strength, and yield stress were determined inversely. A clear dependence of the mechanical parameters on the degree of slimness was discovered, which was confirmed by microscopic examinations. To summarize, the plane-strain-compression-test is a quick and reliable method for determining the local variation of mechanical properties.

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“…High RS is one common feature of LPBF parts. [38,39] Such RS is mostly caused by large thermal gradients, which occur during repeated melting and solidification. [40] It is often reported that a large compressive residual stress (RS) is present in the bulk of AM specimens.…”

Section: Discussionmentioning

confidence: 99%

Artificial Defects in 316L Stainless Steel Produced by Laser Powder Bed Fusion: Printability, Microstructure, and Effects on the Very‐High‐Cycle Fatigue Behavior

et al. 2022

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The printability of artificial defects inside the additively manufactured laser powder bed fusion (LPBF) 316L stainless steel is investigated. The printing parameters of the LPBF process are optimized to produce artificial defects with reproducible sizes at desired positions while minimizing redundant porosity. The smallest obtained artificial defect is 90 μm in diameter. The accuracy of the geometry of the printed defect depends on both the height and the diameter in the input model. The effect of artificial defects on the very‐high‐cycle fatigue (VHCF) behavior of LPBF 316L stainless steel is also studied. The specimens printed with artificial defects in the center are tested under VHCF using an ultrasonic machine. Crack initiation is accompanied by the formation of a fine granular area (FGA), typical of VHCF. Despite the presence of relatively large artificial defects, FGA formation is observed around accidental natural printing defects closer to the surface, which can still be considered as internal. The causes for this occurrence are discussed.

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Anisotropy of Mechanical Properties and Residual Stress in Additively Manufactured 316L Specimens

Cited by 25 publications

References 47 publications

Stability of Postcritical Deformation of CFRP under Static ±45° Tension with Vibrations

Stability of Postcritical Deformation of CFRP under Static ±45° Tension with Vibrations

Application of the plane-strain-compression-test to determine the local mechanical properties of LPBF-manufactured 316l components

Artificial Defects in 316L Stainless Steel Produced by Laser Powder Bed Fusion: Printability, Microstructure, and Effects on the Very‐High‐Cycle Fatigue Behavior

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