scholarly journals Microstructural Control of Fatigue Behaviour in a Novel  Titanium Alloy

Metals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 1200
Author(s):  
Bache ◽  
Davies ◽  
Davey ◽  
Thomas ◽  
Berment-Parr
Keyword(s):  
Titanium Alloy ◽  
Fatigue Crack ◽  
Mechanical Performance ◽  
Fatigue Crack Initiation ◽  
Fatigue Loading ◽  
Fatigue Behaviour ◽  
Fracture Mechanisms ◽  
Mechanical Processing ◽  
Detailed Assessment ◽  
Propagation Properties

The novel titanium alloy TIMETAL® 407 (Ti-407) has been developed as an alternative to Ti-6Al-4V (Ti-6-4), for applications that demand relatively high ductility and energy absorption. Demonstrating a combination of lower strength and greater ductility, the alloy introduces a variety of cost reduction opportunities, including improved machinability. Thermo-mechanical processing and its effects on microstructure and subsequent mechanical performance are characterised, including a detailed assessment of the fatigue and crack propagation properties. Demonstrating relatively strong behaviour under high-cycle fatigue loading, Ti-407 is nevertheless susceptible to time-dependent fatigue effects. Its sensitivity to dwell loading is quantified, and the associated deformation and fracture mechanisms responsible for controlling fatigue life are explored. The intimate relationship between thermo-mechanical processing, micro-texture and fatigue crack initiation through the generation of quasi-cleavage facets is highlighted. Consistent fatigue crack growth kinetics are demonstrated, independent of local microstructure.

Stress-sensitive fatigue crack initiation mechanisms of coated titanium alloy

2021 ◽  
pp. 117179
Author(s):  
Yanyun Bai ◽  
Tao Guo ◽  
Jiawei Wang ◽  
Jin Gao ◽  
Kewei Gao ◽  
...  
Keyword(s):  
Titanium Alloy ◽  
Fatigue Crack ◽  
Crack Initiation ◽  
Fatigue Crack Initiation

Corrosion fatigue crack initiation in ultrafine-grained near-α titanium alloy PT7M prepared by Rotary Swaging

2019 ◽  
Vol 790 ◽  
pp. 347-362 ◽  
Author(s):  
V.N. Chuvil'deev ◽  
V.I. Kopylov ◽  
N.N. Berendeev ◽  
A.A. Murashov ◽  
A.V. Nokhrin ◽  
...  
Keyword(s):  
Titanium Alloy ◽  
Fatigue Crack ◽  
Crack Initiation ◽  
Corrosion Fatigue ◽  
Fatigue Crack Initiation ◽  
Corrosion Fatigue Crack ◽  
Rotary Swaging ◽  
Ultrafine Grained

scholarly journals Effect of Residual Stresses on the Fatigue Behaviour of Torsion Bars

Metals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 1056 ◽  
Author(s):  
Vinko Močilnik ◽  
Nenad Gubeljak ◽  
Jožef Predan
Keyword(s):  
Fatigue Crack ◽  
Residual Stresses ◽  
Stress Amplitude ◽  
Plastic Region ◽  
Fatigue Crack Initiation ◽  
Fatigue Behaviour ◽  
Technological Processes ◽  
Compressive Stresses ◽  
Stress Zone ◽  
Loading Ratio

This article deals with the effect of residual stresses on the fatigue behaviour of torsion bars exposed to cyclic torsional loading with different effective loading ratios, R. The residual compressive stresses on the surface were induced during technological processes by cold surface rolling and torsional overloading (presetting) into the plastic region due to the increase in the elastic linear range for torque. In the paper, we consider two different technological processes for introducing compressive residual stress on the surface of same material. We analysed the stress states affected by different residual and applied stress using the Drucker-Prager criterion in order to determine the actual stress state. Results show that the fatigue limit can be achieved if the maximum principal stresses (combined from residual and applied stresses) do not overcome the safe stress zone. As soon as the maximum principal stress reaches the edge of the safe zone, the number of cycles to failure rapidly reduces. Experimental results show that the effective loading ratio Reff, and consequently the stress amplitude, varies through the cross section of the bar. This initiates the fatigue crack under the surface, in the highest amplitude stress zone, independent of the effective loading ratio Reff. Consequently, increasing the compressive residual stresses on the surface by a second technological process has no significant effect on fatigue crack initiation in situ far from the surface. Increasing the plastic torsional prestress can shift the maximum stress amplitude far from the surface, but a significant volume of material should remain elastically loaded in order to ensure balance with compressive stresses from the surface of the solid bar section.

scholarly journals Energy Dissipation Measurement in Improved Spatial Resolution Under Fatigue Loading

2019 ◽  
Vol 60 (2) ◽  
pp. 181-189
Author(s):  
A. Akai ◽  
D. Shiozawa ◽  
T. Yamada ◽  
T. Sakagami
Keyword(s):  
Fatigue Crack ◽  
Energy Dissipation ◽  
Crack Initiation ◽  
Fatigue Limit ◽  
Spatial Resolution ◽  
Fatigue Crack Initiation ◽  
Fatigue Loading ◽  
Dissipated Energy ◽  
Damage Initiation ◽  
Slip Bands

Abstract Recently, a technique for rapidly determining a material’s fatigue limit by measuring energy dissipation using infrared thermography has received increasing interest. Measuring the energy dissipation of a material under fatigue loading allows the rapid determination of a stress level that empirically coincides with its fatigue limit. To clarify the physical implications of the rapid fatigue limit determination, the relationship between energy dissipation and fatigue damage initiation process was investigated. To discuss the fatigue damage initiation process at grain size scale, we performed high-spatial-resolution dissipated energy measurements on type 316L austenitic stainless steel, and observed the slip bands on the same side of the specimen. The preprocessing of dissipated energy measurement such as motion compensation and a smoothing filter was applied. It was found that the distribution of dissipated energy obtained by improved spatial resolution measurement pinpointed the location of fatigue crack initiation. Owing to the positive correlation between the magnitude of dissipated energy and number of slip bands, it was suggested that the dissipated energy was associated with the behavior of slip bands, with regions of high dissipated energy predicting the location of fatigue crack initiation.

Fatigue crack initiation and propagation properties of Ti-22V-4Al

2017 ◽  
Vol 2017 (0) ◽  
pp. PS29
Author(s):  
Kei TAKANASHI ◽  
Shota KASHIMA ◽  
Fumiyoshi YOSHINAKA ◽  
Takashi NAKAMURA ◽  
Nao FUJIMURA ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Crack Initiation ◽  
Fatigue Crack Initiation ◽  
Crack Initiation And Propagation ◽  
Initiation And Propagation ◽  
Propagation Properties

The Mechanism of Internal Fatigue-Crack Initiation in a Titanium Alloy with Lamellar and Equiaxed Microstructure

2019 ◽  
Author(s):  
Xiangnan Pan ◽  
Shouwen Xu ◽  
Guian Qian ◽  
Alexander Nikitin ◽  
Andrey Shanyavskiy ◽  
...  
Keyword(s):  
Titanium Alloy ◽  
Fatigue Crack ◽  
Crack Initiation ◽  
Fatigue Crack Initiation ◽  
Equiaxed Microstructure

High Cycle Fatigue of Ti-6Al-4V Alloy in Simulated Steam Environment

2015 ◽  
Author(s):  
Yu-Jia Li ◽  
Lin-Bo Mei ◽  
Fu-Zhen Xuan
Keyword(s):  
Fatigue Crack ◽  
Fatigue Strength ◽  
Stress Ratio ◽  
Fatigue Crack Initiation ◽  
Saturated Steam ◽  
Fracture Mechanisms ◽  
Low Oxygen ◽  
Critical Problems ◽  
Stress Ratios ◽  
Corrosion Pits

Fatigue life and reliability are the critical problems for long blades design due to complicated stress state, wet steam and aggressive environment. In this report, the effects of stress ratio, surface properties, steam, and sodium-chloride (NaCl) aqueous environments on the fatigue strength and fracture mechanisms of Ti-6Al-4V alloy have been investigated. Results indicate that residual compressive stress decreases and vanishes finally with increasing stress ratio. Compared to fatigue crack originating from surface for annealed specimens, the fatigue crack initiation sites are located in the interior of the specimen due to the effect of residual stress when low stress ratios are present. Fatigue experiments have been performed in saturated steam with low oxygen content at 100°C and NaCl aqueous at 80 °C. Results indicate that, for 0.1 stress ratio loading conditions, steam environment demonstrates the most serious effect on the endurance limit with 12.3% reduction of fatigue strength. NaCl aqueous leads to the 9.6% drop in fatigue strength corresponding to 107 cycles of design life. For all corrosion environments, cracks originated from the surface and no corrosion pits were observed.

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