Study on the Overload and Dwell-Fatigue Property of Titanium Alloy in Manned Deep Submersible

Frequency is an important factor influencing the fatigue behavior. Regarding to the dwell fatigue, it corresponds to the effect of rise and fall time, which is also an important issue especially for the safety evaluation of structure parts under dwell fatigue loading, such as the engines of aircrafts and the pressure hulls of deep-sea submersibles. In this paper, the effect of rise and fall time (2 s, 20 s, 110 s, and 200 s) on the dwell fatigue behavior is investigated for a high strength titanium alloy Ti-6Al-2Sn-2Zr-3Mo-X with basket-weave microstructure. It is shown that the dwell fatigue life decreases with increasing the rise and fall time, which could be correlated by a linear relation in log–log scale for both the specimen with circular cross section and the specimen with square cross section. The rise and fall time has no influence on the crack initiation mechanism by the scanning electron microscope observation. The cracks initiate from the specimen surface and all the fracture surfaces present multiple crack initiation sites. Moreover, the facet characteristic is observed at some crack initiation sites for both the conventional fatigue and dwell fatigue tests. The paper also indicates that the dwell period of the peak stress reduces the fatigue life and the dwell fatigue life seems to be longer for the specimen with circular cross section than that of the specimen with square cross section.

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Experimental Study on Fatigue Crack Growth in a Titanium Alloy

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.297-300.2489 ◽

2005 ◽

Vol 297-300 ◽

pp. 2489-2494

Author(s):

Qing Fen Li ◽

Peng Wang ◽

Dong Liu ◽

Jun Wang ◽

Hong Juan Liu ◽

...

Keyword(s):

Growth Rate ◽

Titanium Alloy ◽

Fatigue Crack ◽

Crack Growth Rate ◽

Fatigue Crack Growth ◽

Crack Growth ◽

Welded Joint ◽

Fatigue Property ◽

Rolled Ring ◽

Titanium Material

A series of test for the fatigue crack growth rate da/dN and the threshold ΔKth values were performed with CT specimens on a ship-condenser material titanium alloy plate and rolled ring. Base metal, welded joint and HAZ (heat affected zone) materials were used to make different test specimens. Specimens made from the titanium plate were cut along L-T direction, those made from rolled ring were obtained along C-R and L-R direction respectively. Results show that the fatigue crack growth rate value of welded joint is much higher than those of base metal and HAZ material. The da/dN values of C-R direction specimens are much higher than those of L-R direction specimens, whereas the ΔKth values are lower. It means that welding process may lead to a great reduction in the fatigue property for titanium alloy and the effect of crack orientation on fatigue property is not negligible for titanium alloy. To select a proper orientation of titanium material is therefore very important in engineering practice. Results also indicate that a simplified method can be used to calculate the ΔKth values for titanium material, that is, ΔKth values may be calculated directly from the da/dN expression in a zone near the threshold and the laborious measurements of ΔKth may therefore be saved.

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Crystal plasticity analysis of temperature-sensitive dwell fatigue in Ti-6Al-4V titanium alloy for an aero-engine fan disc

International Journal of Fatigue ◽

10.1016/j.ijfatigue.2021.106688 ◽

2021 ◽

pp. 106688

Author(s):

Liangwei Yin ◽

Osamu Umezawa

Keyword(s):

Titanium Alloy ◽

Crystal Plasticity ◽

Temperature Sensitive ◽

Dwell Fatigue ◽

Aero Engine

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Study on Rotating Bending Fatigue Property of Ti65 Titanium Alloy

Materials Science Forum ◽

10.4028/www.scientific.net/msf.849.347 ◽

2016 ◽

Vol 849 ◽

pp. 347-352

Author(s):

Xu Wang ◽

Si Qing Li ◽

Jing Nan Liu

Keyword(s):

Titanium Alloy ◽

Fatigue Strength ◽

Room Temperature ◽

Fatigue Property ◽

Fatigue Properties ◽

Bending Fatigue ◽

Notched Specimens ◽

Different Temperatures ◽

Rotating Bending Fatigue ◽

Rotating Bending

The rotating bending fatigue properties of Ti65 titanium alloy blisk forging was studied in the present investigation. The smooth and notched specimens were prepared to test the fatigue properties at room temperature and 650°C. Meanwhile, the influences on rotating bending fatigue of temperature and type were analyzed. Furthermore, the fractural morphology was observed through scanning electron microscopy. The results showed that the medium fatigue strength of Ti65 titanium alloy decreased at 650°C compared with that at room temperature, and the fatigue strength of notched specimens indicated the same significant declination at different temperatures compared with smooth specimens. At room temperature the medium fatigue strength of smooth and notched are 473MPa and 173MPa, respectively, and the fatigue notch sensitive coefficient was 0.87. At 650°C the medium fatigue strength of smooth and notched specimens are 427MPa and 168MPa, where the fatigue notch sensitive coefficient was 0.78.

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Titanium Alloy Developments For Future Fan Disc Applications – The Fatigue Response of “Alloy 104”

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.891-892.569 ◽

2014 ◽

Vol 891-892 ◽

pp. 569-574 ◽

Cited By ~ 3

Author(s):

Jon S. Hewitt ◽

Matthew J. Thomas ◽

Paul Garratt ◽

Martin R. Bache

Keyword(s):

Titanium Alloy ◽

Room Temperature ◽

High Cycle Fatigue ◽

High Strength ◽

Fatigue Behaviour ◽

Hold Period ◽

Peak Loads ◽

Dwell Fatigue ◽

Load Regime ◽

Aero Engine

Alloy 104 is a novel high strength, α+β titanium alloy primarily aimed at aero-engine fan disc applications. Two microstructural variants of Alloy 104 have been assessed. Room temperature tensile strength and elongation have been investigated alongside a more detailed study of low and high cycle fatigue behaviour. The alloy clearly demonstrated an improved fatigue resistance in both microstructural conditions, whilst maintaining forgeability and a comparable density to Ti-6Al-4V. Furthermore, the alloy has been subjected to a load regime with a hold period at peak loads and proven to be insensitive to dwell fatigue.

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Surface Integrity and Fatigue Property of a High Speed Milled Titanium Alloy

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.53-54.305 ◽

2008 ◽

Vol 53-54 ◽

pp. 305-310 ◽

Cited By ~ 9

Author(s):

Guo Sheng Geng ◽

Jiu Hua Xu

Keyword(s):

Residual Stress ◽

Surface Roughness ◽

Titanium Alloy ◽

Surface Integrity ◽

Work Hardening ◽

High Speed ◽

Cutting Speed ◽

Fatigue Property ◽

Machined Surface ◽

Metallurgical Structure

Surface integrity has a great effect on the fatigue property of titanium alloy. The surface integrity and fatigue property of a high speed milled Ti-6.5Al-2Zr-1Mo-1V (TA15) titanium alloy were investigated in this research. The main objective of this paper is to study the influence of milling speed on the surface integraty and fatigue property of the machined part. The surface roughness, work hardening, metallurgical structure and residual stress of the machined surface were studied in a cutting speed range of from 50m/min to 300m/min. To verify the relationship between cutting speed and the surface integrity of machined surface, the fatigue property of titanium alloy specimens milled at four different cutting speeds ranging from 50 to 200m/min were compared at two stress levels. This research shows that the cutting speed has little effect on the work hardening, metallurgical structure and residual stress, but the surface roughness decreases with the increasing cutting speed. Therefore, increasing milling speed has a positive effect on the surface integrity and fatigue property of the machined surface.

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