Fatigue strength of blunt V-notched specimens produced by selective laser melting of Ti-6Al-4V

Razavi, Seyed Mohammad Javad; Ferro, Paolo; Berto, Filippo; Torgersen, Jan

doi:10.1016/j.tafmec.2017.06.021

Cited by 109 publications

(49 citation statements)

References 33 publications

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“…Considering the aforementioned outcomes and the statistical evidence of not significant differences among the fatigue responses of the nine sets (also including those tested in Croccolo et al 15 ), a global fatigue curve was determined. The equations of the aforementioned lower (10% failure probability) and upper (90% failure probability) bounds are respectively reported in Equations (7) and (8) and Equations (9) and (10). This model is likely to have many applications in the field of machine design, as it simultaneously accounts for the manufacturing factors of build orientation and machining and related allowance.…”

Section: Discussionmentioning

confidence: 99%

Sensitivity of direct metal laser sintering Maraging steel fatigue strength to build orientation and allowance for machining

Croccolo

Agostinis

Fini

et al. 2018

Fatigue Fract Eng Mat Struct

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This work deals with the effect of build orientation and of allowance for machining on DMLS‐produced Maraging Steel MS1. The experimental results, arranged by tools of Design of Experiment, have been statistically processed and compared. The outcomes were that, probably due to effect of the thermal treatment, machining, and material properties, the aforementioned factors do not have a significant impact on the fatigue response. This made it possible to work out a global curve that accounts for all the results, consisting in a high amount of data points. This can be regarded as one of the most complete and reliable fatigue models in the current literature. Fractographic and micrographic studies have been performed as well, to individuate the crack initiation points, usually located at subsurface porosities, and to investigate the location of internal inclusions and the actual martensitic microstructure along the stacking direction and on the build plane.

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Section: Discussionmentioning

confidence: 99%

Sensitivity of direct metal laser sintering Maraging steel fatigue strength to build orientation and allowance for machining

Croccolo

Agostinis

Fini

et al. 2018

Fatigue Fract Eng Mat Struct

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“…1.00E+01 Regarding components having complex geometries, no specific design criteria have been presented so far to consider stress concentration phenomena arising from geometrical discontinuities [14,15]. Hence, the same methodology can be examined in future for the notched specimens produced by additive manufacturing.…”

Section: Energy-life Relationshipmentioning

confidence: 99%

Low-Cycle Fatigue Behaviour of AISI 18Ni300 Maraging Steel Produced by Selective Laser Melting

Branco

Costa

Berto

et al. 2018

Metals

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Selective laser melting has received a great deal of attention in recent years. Nevertheless, research has been mainly focused on the technical issues and their relationship with the final microstructure and monotonic properties. Fatigue behaviour has rarely been addressed, and the emphasis has been placed on high-cycle regimes. The aim of this paper is, therefore, to study, in a systematic manner, the cyclic plastic behaviour of AISI 18Ni300 maraging steel manufactured by selective laser melting. For this purpose, low-cycle fatigue tests, under fully-reversed strain-controlled conditions, with strain amplitudes ranging from 0.3% to 1.0%, were performed. After testing, fracture surfaces were examined by scanning electron microscopy to identify the main fatigue damage mechanisms. The analysis of results showed a non-Masing material, with a slight strain-softening behaviour, and non-linear response in both the elastic and plastic regimes. In addition, this steel exhibited a very low transition life of about 35 reversals, far below the values of conventional materials with equivalent monotonic mechanical properties, which can be attributed to the combination of high strength and low ductility. The total strain energy density, irrespective of strain amplitude, revealed itself to be a quite stable parameter throughout the lifetime. Finally, the SEM analysis showed for almost all the tested samples cracks initiated from the surface and inner defects which propagated through the rest of the cross section. A ductile/brittle fracture, with a predominance of brittle fracture, was observed in the samples, owing to the presence of defects which make it easier to spread the microcracks.

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“…In fact, it is meaningful to discuss failure mechanisms from the view of macroscopic fracture morphology. In recent work published in [35,36], even in a smooth forming surface, roughness might lead to the origination of fatigue crack which would further evolve into a crack initiation point. a number of small holes present at the fracture.…”

Section: Mechanical Evolution Mechanismmentioning

confidence: 99%

Research on Selective Laser Melting of Ti6Al4V: Surface Morphologies, Optimized Processing Zone, and Ductility Improvement Mechanism

Wang

Dou

Yang

2018

Metals

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Abstract:The quality and mechanical properties of titanium alloy fabricated using selective laser melting (SLM) are critical to the adoption of the process which has long been impeded by the lack of uniformity in SLM-fabrication parameter optimization. In order to address this problem, laser power and scanning speed were combined into linear energy density as an independent variable, while surface morphology was defined as a metric. Based on full-factor experiments, the surface quality of SLM-fabricated titanium alloy was classified into five zones: severe over-melting zone, high-energy density nodulizing zone, smooth forming zone, low-energy density nodulizing zone, and sintering zone. The mechanism resulting in the creation of each zone was analyzed. Parameter uniformity was achieved by establishing a parameter window for each zone, and it also revealed that under smooth forming conditions, the relationship of linear energy density to the quality of the formed surface is not linear. It was also found that fabrication efficiency could be improved in the condition of the formation of a smooth surface by increasing laser power and scanning speed. In addition, maximum elongation of the SLM-fabricated titanium alloy increased when the densified parts were processed using an appropriate heat treatment, from a low value of 5.79% to 10.28%. The mechanisms of change in ductility of the alloy were thoroughly analyzed from the perspectives of surface microstructure and fracture morphology. Results indicate that after heat treatment, the microcosmic structure of the alloy was converted from acicular martensite α' phase to a layered α+β double-phase structure, the fracture type also changed from quasi-cleavage to ductile fracture.

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Fatigue strength of blunt V-notched specimens produced by selective laser melting of Ti-6Al-4V

Cited by 109 publications

References 33 publications

Sensitivity of direct metal laser sintering Maraging steel fatigue strength to build orientation and allowance for machining

Sensitivity of direct metal laser sintering Maraging steel fatigue strength to build orientation and allowance for machining

Low-Cycle Fatigue Behaviour of AISI 18Ni300 Maraging Steel Produced by Selective Laser Melting

Research on Selective Laser Melting of Ti6Al4V: Surface Morphologies, Optimized Processing Zone, and Ductility Improvement Mechanism

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