Effects of Stress Ratio on Initiation and Initial Propagation of Interior-originating Crack in Ti-6Al-4V Alloy

博幸, 小熊; 孝, 中村; 秀治, 横山; 徹, 野口

doi:10.1299/kikaia.70.1116

Cited by 8 publications

(3 citation statements)

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“…Oguma et al also produced a fatigue limit diagram at N = 10 8 cycles of a Ti6Al4V alloy. 17) Although the sample differed from that in the present alloy, the trend, i.e., fatigue limit at R ³ 0, decreased remarkably, as depicted in Fig. 6.…”

Section: Discussionmentioning

confidence: 54%

Lock-in Infrared Thermography for Fatigue Limit Estimation in Ti–6Al–4V Alloy

2021

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Lock-in infrared thermography was used to estimate the fatigue limit for Ti6Al4V alloy at room temperature. The method detected infrared emitted from specimen during cyclic loading, i.e., temperature change related to frequency ( f ) of the loading. The temperature change contained reversible component and irreversible component, which related to thermos-elastic effect and plastic deformation, respectively. The latter component was divided from the former one by lock-in analysis to estimate fatigue limit. Estimated fatigue limits corresponded to those obtained from conventional fatigue tests at several stress ratios. A new assessment line was identified as, where • a represents the stress amplitude, • w signifies the fatigue limit, • m denotes mean stress, • B expresses tensile strength, and the n exponent for the alloy is about 2.3. The non-failure region of the new diagram was smaller than that of the modified Goodman diagram because of a reduced fatigue limit at near-zero stress ratios in the titanium alloy.

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Section: Discussionmentioning

confidence: 54%

Lock-in Infrared Thermography for Fatigue Limit Estimation in Ti–6Al–4V Alloy

2021

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“…important findings are that the nano-crystalline structure forms beneath the crack surface (Oguma, N. et al, 2003) and that a large number of compressive force applications during fatigue loading plays a crucial role in forming the structure (Hong et al, 2016) and the convex-concave fracture surface (Shiina et al, 2002, Shiina et al, 2004. This unique fracture surface has been observed not only in high-strength steel, but also in titanium , Oguma, H. et al, 2004, aluminum (Yamada and Miyakawa, 2009) and magnesium alloys (Shiozawa and Miyazaki, 2013). As a reason for the appearance of the fracture surface and the nanocrystallization beneath it, the authors have hypothesized that a huge number of repeated contacts of the crack surfaces has a similar mechanical effect as SPD (Nakamura et al, 2007, Nakamura et al, 2010, Nakamura and Oguma, 2011.…”

Section: Introductionmentioning

confidence: 97%

Nano-structural refinement of metallic surfaces by using low-compression cyclical loading

Fujimura

Nakamura

Ueno

2018

Mechanical Engineering Letters

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Recent studies on very high cycle fatigue (VHCF) have observed a unique fracture surface with a fine granular area around the crack origin that arises from long-term repeated contacts of fracture surfaces (over 10 7 cycles). A fine microstructure including nanocrystalline is known to form in the matrix just beneath the fracture surface. Focusing on these phenomena, this study devised a new surface modification technique, called Cyclic Press (CP), that creates a nanocrystalline layer using cyclic compressive loading. Repeated low-compression loadings were applied to the surfaces of SNCM439 high-strength steel and ADC12 die-cast aluminum alloy with an indenter for 5 × 10 7 cycles. Then, the surfaces and cross sections were analyzed by using a laser microscope, a scanning electron microscope, a scanning ion microscope, and energy dispersive X-ray spectrometry (EDS). As a result, a nanocrystalline structure very similar to that of the cross section beneath the fracture surface in the VHCF regime clearly formed in the surface layer of both materials. Additionally, an oxygen-rich layer formed at the surface of the CP-treated ADC12. This result was considered to be caused by diffusion of elemental oxygen in the atmosphere by a huge number of repeated contacts between the indenter and specimen. Overall, the results indicate that CP is a useful technique for forming nanocrystalline layers in metal surfaces and can also be expected as a new method for diffusing surrounding gaseous elements into surfaces at room temperature.

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“…A modified Goodman diagram is generally used to evaluate this effect because it is simple to use and produces a safe-side evaluation in many materials. However, it has been reported that the modified Goodman line for Ti-6Al-4V alloy enters the dangerous side near R = 0 at ambient temperature [1][2][3][4]. Judging from these reports on Ti-6Al-4V alloy, it seems necessary to confirm the validity of the modified Goodman diagram for this forging, especially at low temperatures.…”

Section: Introductionmentioning

confidence: 99%

Effect of stress ratio on high-cycle fatigue properties of Ti-6Al-4V ELI alloy forging at low temperature

Ono¹,

Yuri²,

Ogata³

et al. 2014

AIP Conference Proceedings

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Abstract. The effect of the stress ratio R (the ratio of minimum stress to maximum stress) on the high-cycle fatigue properties of Ti-6Al-4V extra-low interstitial (ELI) alloy forging was investigated at 293 and 77 K. At 293 K, the fatigue strength at 10 7 cycles exhibited deviations below the modified Goodman line in the R=0.01 and 0.5 tests. Moreover, at 77 K, larger deviations of the fatigue strength at 10 7 cycles below the modified Goodman line were confirmed in the same stress ratio conditions. The high-cycle fatigue strength of the present alloy forging exhibit an anomalous mean stress dependency at both temperatures and this dependency becomes remarkable at low temperature.

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Effects of Stress Ratio on Initiation and Initial Propagation of Interior-originating Crack in Ti-6Al-4V Alloy

Cited by 8 publications

References 0 publications

Lock-in Infrared Thermography for Fatigue Limit Estimation in Ti–6Al–4V Alloy

Lock-in Infrared Thermography for Fatigue Limit Estimation in Ti–6Al–4V Alloy

Nano-structural refinement of metallic surfaces by using low-compression cyclical loading

Effect of stress ratio on high-cycle fatigue properties of Ti-6Al-4V ELI alloy forging at low temperature

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