Effects of stress ratio on high-cycle and very-high-cycle fatigue behavior of a Ti–6Al–4V alloy

Liu, Xiaolong; Sun, Chengqi; Hong, Youshi

doi:10.1016/j.msea.2014.09.115

Cited by 133 publications

(123 citation statements)

References 39 publications

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“…On the contrast, cracks initiate at the surface to nearly all the un-UNSMed specimens, it is in accordance with which reported in Ref. [31]. Comparing with IS, the 1 × 10 8 cycles fatigue strength of UNSM is increased by 7.9%.…”

Section: Fatigue Propertiessupporting

confidence: 90%

“…Though the high cycle fatigue (HCF) and the very high cycle fatigue behaviors of TC4 were investigated in previous papers [29,30], the reason for crack initiation from the surface or from both the surface and the interior at a stress ratio r = −1 is not clear. Liu et al studied the effects of stress ratio (from −1 to 0.5) on fatigue crack initiation and propagation [31], all the specimens at r = −1 failed from the surface. The fatigue behavior of TC4 in 0.9% physiological saline solution [32] showed that the slope of S-N curve decreases as the dipping time increases.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Ultrasonic Surface Impact on the Fatigue Behavior of Ti-6Al-4V Subject to Simulated Body Fluid

Cao

Wang

et al. 2017

Metals

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Abstract:The effect of ultrasonic nanocrystal surface modification (UNSM) on the fatigue behavior of Ti6Al4V (TC4) in simulated body fluid (SBF) was investigated. UNSM with the condition of a static load of 25 N, vibration amplitude of 30 µm and 36,000 strikes per unit produced about 35 µm surface severe plastic deformation (SPD) layers on the TC4 specimens. One group was treated with a hybrid surface treatment (UNSM + TiN film). UNSM technique improves the micro hardness and the compressive residual stress. The surface roughness is increased slightly, but it can be remarkably improved by the TiN film. The fatigue strength of TC4 is improved by about 7.9% after UNSM. Though the current density of corrosion is increased and the pitting corrosion is accelerated, UNSM still improved the fatigue strength of TC4 after pre-soaking in SBF by 10.8%. Interior cracks initiate at the deformed carbide and oxide inclusions due to the ultrasonic impacts of UNSM. Corrosion products are always observed at the edge of fracture surface to both interior cracks and surface cracks. Coating a TiN film on the UNSMed surface helps to improve the whole properties of TC4 further.

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Section: Fatigue Propertiessupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Effect of Ultrasonic Surface Impact on the Fatigue Behavior of Ti-6Al-4V Subject to Simulated Body Fluid

Cao

Wang

et al. 2017

Metals

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“…The fractured specimens were analysed in a scanning electron microscope (SEM); all showed features similar to those shown in the schematic in Figure 3, which is typical of metal, and in particular of Ti6Al4V fatigue fracture surfaces [14,15,16]. All the fractographs showed areas of crack initiation, slow crack propagation, fast crack propagation, and final fracture.…”

Section: Resultsmentioning

confidence: 87%

High Cycle Fatigue Properties of as-Built Ti6al4v (Eli) Produced by Direct Metal Laser Sintering

Malefane

Preez

Maringa

2017

SAJIE

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The high cycle fatigue (HCF) properties of direct metal laser sintering (DMLS) of Ti6Al4V (ELI) in three mutually orthogonal build directions were investigated by cycling specimens under load control, in a tension-tension fatigue testing machine. Semi-log graphs of maximum stress (S) against life (N) of the specimens produced along the respective three build directions were plotted, and the displayed endurance limits compared. Optical and scanning electron microscopy were used to compare and analyse the crack initiation and propagation characteristics of the specimens. The influence of the build direction on the fatigue properties of the tested specimens is discussed here. OPSOMMINGDie hoësiklus vermoeidheidseienskappe van direkte metaallaser sintering van Ti6Al4V in drie onderlinge ortogonale bourigtings is ondersoek deur monsters te onderwerp aan beheerde sikliese ladings met behulp van ŉ trek-trek vermoeidheidstoetsmasjien. Semi-log grafieke van maksimum spanning teen leeftyd (S-N grafieke) is vir die monsters saamgestel, saam met die onderskeie bou rigtings. Sodoende kon die vermoeidheidslewe vergelyk word. Optiese-en skandeer elektronmikroskopie is gebruik om die kraakvorming en -voortplanting te vergelyk en te analiseer. Die invloed van die bourigting op die vermoeidheidseienskappe van die monsters is bespreek. INTRODUCTIONWork done by the Centre for Rapid Prototyping and Manufacturing (CRPM) of the Central University of Technology Free State on the manufacture of parts using direct metal laser sintering (DMLS) of Ti6Al4V (ELI) powder has thus far been based on the static mechanical properties of such DMLS parts that have been stress-relieved. These static mechanical properties were found to conform to the properties of standard wrought Ti6Al4V (ELI) [1,2]. However, for DMLS Ti6Al4V (ELI) parts that are expected to experience cyclic loading, there is uncertainty that they will last their full operational life. This is due to limited available fatigue life data for the DMLS-produced alloy.This study presents baseline data and analyses on as-built DMLS Ti6Al4V (ELI), as a precursor to studies of DMLS Ti6Al4V (ELI) that is heat treated in order to tailor its microstructure to give the best high cycle fatigue (HCF) properties possible.

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“…Surface facets were tilted 30 • , whilst subsurface facets were 30 • − 60 • towards the loading direction [6]. The point of fracture origin is susceptible to the loading conditions and can also occur subsurface [7]. 20 Individual cycles can leave single growth features on the fracture surface which are termed striations.…”

Section: Introductionmentioning

confidence: 99%

Influence of complex LCF and dwell load regimes on fatigue of Ti–6Al–4V

et al. 2016

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Real components are usually subjected to variable amplitude fatigue, and yet the deformation micromechanisms that occur due to such load changes have barely been the subject of study. Here, unidirectionally rolled equiaxed Ti6Al-4V plate was subjected to mixed dwell and variable amplitude low cycle fatigue (LCF), with the finding that overloads near the yield stress were found to retard subsequent fatigue crack growth, whilst elastic underloads were found to accelerate subsequent growth. Dwell intervals were found to be especially damaging, to a far greater extent than either dwell or LCF alone. Dwell facets were found to initiate subsurface and to be smoother than LCF facets, but were otherwise similar in orientation (∼ 30 • to the loading axis) and crystallographic plane, 2-13 • from (0002). However, no alteration of the slip bands underlying striations was observed at the point of load changes using TEM. In failure investigation, striation counting is an important tool; the loading changes used were not found to affect the number of striations formed. Dislocation networks were found between similarly oriented grains in the as-received material, which disintegrated under dwell loading and at high stresses.

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Effects of stress ratio on high-cycle and very-high-cycle fatigue behavior of a Ti–6Al–4V alloy

Cited by 133 publications

References 39 publications

Effect of Ultrasonic Surface Impact on the Fatigue Behavior of Ti-6Al-4V Subject to Simulated Body Fluid

Effect of Ultrasonic Surface Impact on the Fatigue Behavior of Ti-6Al-4V Subject to Simulated Body Fluid

High Cycle Fatigue Properties of as-Built Ti6al4v (Eli) Produced by Direct Metal Laser Sintering

Influence of complex LCF and dwell load regimes on fatigue of Ti–6Al–4V

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