Faceted crack induced failure behavior and micro-crack growth based strength evaluation of titanium alloys under very high cycle fatigue

2020 ◽  
Vol 131 ◽  
pp. 105369 ◽  
Author(s):  
Wei Li ◽  
Meng Li ◽  
Rui Sun ◽  
Xinxin Xing ◽  
Ping Wang ◽  
...  
Keyword(s):  
Titanium Alloys ◽  
Crack Growth ◽  
High Cycle Fatigue ◽  
Failure Behavior ◽  
Cycle Fatigue ◽  
Strength Evaluation ◽  
Very High Cycle Fatigue ◽  
Very High

scholarly journals Properties of the Fine Granular Area and Postulated Models for Its Formation during Very High Cycle Fatigue—A Review

2020 ◽  
Vol 10 (23) ◽  
pp. 8475
Author(s):  
Jan Patrick Sippel ◽  
Eberhard Kerscher
Keyword(s):  
Fatigue Strength ◽  
Crack Initiation ◽  
Crack Growth ◽  
High Performance ◽  
High Cycle Fatigue ◽  
The Other ◽  
Cycle Fatigue ◽  
Very High Cycle Fatigue ◽  
Open Questions ◽  
Very High

Understanding the mechanisms leading to very high cycle fatigue is necessary to make predictions about the behavior under various conditions and to ensure safe design over the whole lifetime of high-performance components. It is further vital for the development of possible measures to increase the very high cycle fatigue strength. This review therefore intends to give an overview of the properties of the fine granular area that have been observed so far. Furthermore, the existing models to describe the early crack initiation and crack growth within the very high cycle fatigue regime are outlined and the models are evaluated on the basis of the identified fine granular area properties. The aim is to provide an overview of the models that can already be considered refuted and to specify the respective open questions regarding the other individual models.

scholarly journals The influence of hydrogen on the very high cycle fatigue property and crack growth characteristics of bearing steels

2018 ◽  
Vol 4 (0) ◽  
pp. 18-00134-18-00134
Author(s):  
Takeshi OGAWA ◽  
Shota HASUNUMA ◽  
Yosuke INATOMI ◽  
Natsumi YASUKOCHI ◽  
Shohei SHIGETA
Keyword(s):  
Crack Growth ◽  
High Cycle Fatigue ◽  
Fatigue Property ◽  
Growth Characteristics ◽  
Cycle Fatigue ◽  
Bearing Steels ◽  
Very High Cycle Fatigue ◽  
Very High

scholarly journals Nonlinear dynamics and stages of damage of Ti6Al4V and Ti45Nb titanium alloys in very high cycle fatigue

2020 ◽  
pp. 145-153
Author(s):  
M. V Bannikov ◽  
V. A Oborin ◽  
D. A Bilalov ◽  
O. B Naimark
Keyword(s):  
Titanium Alloys ◽  
High Cycle Fatigue ◽  
Three Dimensional ◽  
Fatigue Properties ◽  
Experimental Program ◽  
Cycle Fatigue ◽  
Very High Cycle Fatigue ◽  
Number Of Cycles ◽  
Radial Shear Rolling ◽  
Very High

The paper presents an experimental methodology aimed at evaluating a very-high cycle resource for aviation titanium alloys Vt-6 (Ti6Al4V) and Ti45Nb for medical applications with different microstructures (large-crystal and submicrocrystalline ones). The submicrocrystalline (SMC) state was obtained by an intensive plastic deformation realized in two ways: the three-dimensional forging for Ti45Nb and radial-shear rolling for Ti6Al4V. The experimental program tests high-cycle and very-high-cycle loading (number of cycles 107-109) realized using the in situ determination method of the accumulation of the irreversible fatigue damage by analyzing nonlinear forms of feedback in a closed system ultrasonic fatigue setup. This makes it possible to establish the connection of the microscopic fatigue mechanisms with the model views and consider the stages of the damage development based on the nonlinear kinetics of the defect accumulation under cyclic loading in high- and gigacycle fatigue modes. We established various relations between changes in the amplitude of the second harmonic of vibrations of the free end of the samples with different internal structures, which are associated with the mechanisms of stress relaxation and damage accumulation. The grain size reduction in Ti45Nb alloy by the three-dimensional forging improved the fatigue properties by 1.3-1.5 times, whereas for VT-6 alloy, the radial-shear rolling method could not increase the fatigue properties in the very high cycle fatigue range, which may be caused by the presence of large residual internal stresses. Based on the scale parameters obtained earlier from the fracture surface morphology and the relations established in this work, the kinetic equations for the origin and growth of fatigue cracks in the gigacycle loading range will be constructed. This equation, based on the empirical power parameters related to the structure of the material, will allow us to determine the number of cycles for the origin of an internal crack and its growth to the surface.

Experimental Characterization of Competition of Surface and Internal Damage in Very High Cycle Fatigue Regime

2017 ◽  
Vol 754 ◽  
pp. 79-82
Author(s):  
Wei Chang Zhang ◽  
Ming Liang Zhu ◽  
Fu Zhen Xuan
Keyword(s):  
Crack Growth ◽  
Slip Band ◽  
High Cycle Fatigue ◽  
Surface Measurement ◽  
Ultrasonic Frequency ◽  
Rotor Steel ◽  
Cycle Fatigue ◽  
Internal Damage ◽  
Very High Cycle Fatigue ◽  
Very High

Axially push-pull cyclic tests of a low strength rotor steel were performed up to the very high cycle fatigue regime at ambient environment under ultrasonic frequency. Fatigue tests were interrupted at selected number of cycles for surface morphology observation and roughness measurement with the help of a 3D surface measurement system (Alicona InfiniteFocusSL). The fatigue extrusions and slip band developed on the specimen surface were recorded. The influence of stress level on the number and morphology of slip band was discussed. The surface roughness of fatigue specimens was found to be increased with the increasing of fatigue cycles. The fatigued specimens were finally cracked from surface or interior micro-defects after observation of fracture surface by scanning electron microscopy. The internal damage behavior consists of crack initiation and early propagation from micro-defect, crack growth within the fish eye, and fast crack growth. It is observed that there exists a competition between surface and internal fatigue damage in the very high cycle fatigue regime, i.e., surface damage is gradually developed with the increasing of fatigue cycles, while the critical interior micro-defect can be dominant for fatigue cracking.

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