Microstructural Characterization of Fatigue Damage of CFRP in the Very High Cycle Fatigue Regime

As being used for structural applications, where a high corrosion resistance is required, the fatigue behavior of duplex stainless steels (DSS) is governed by the partition of cyclic plasticity to the two phases, ferrite and austenite, respectively. Under very high cycle fatigue (VHCF) loading conditions, the heterogeneous distribution of crystallographic misorientations between neighboring grains and phases yields to a pronounced scatter in fatigue life, ranging from 1 million to 1 billion cycles for nearly the same stress amplitude. In addition, the relevant damage mechanisms depend strongly on the atmosphere. Stress corrosion cracking in NaCl-containing atmosphere causes a pronounced decrease in the VHCF life. By means of ultrasonic fatigue testing at 20kHz in combination with high resolution scanning electron microscopy, electron back-scattered diffraction (EBSD), focused ion beam milling (FIB) and synchrotron tomography, the microstructure heterogeneities were quantified and correlated with local fatigue damage. It has been shown that the fatigue process is rather complex, involving redistribution of residual stresses and three-dimensional barrier effects of the various interfaces. The application of a 2D/3D finite element model allows a qualitative prediction of the fatigue-damage process in DSS that is controlled by stochastic local microstructure arrangements.

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In situ nonlinear ultrasonic for very high cycle fatigue damage characterization of a cast aluminum alloy

Materials Science and Engineering A ◽

10.1016/j.msea.2015.08.029 ◽

2015 ◽

Vol 645 ◽

pp. 248-254 ◽

Cited By ~ 8

Author(s):

Wenkai Li ◽

Haitao Cui ◽

Weidong Wen ◽

Xuming Su ◽

C.C. Engler-Pinto

Keyword(s):

High Cycle Fatigue ◽

Cast Aluminum Alloy ◽

Cycle Fatigue ◽

Cast Aluminum ◽

Damage Characterization ◽

Very High Cycle Fatigue ◽

Nonlinear Ultrasonic ◽

Very High

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Fatigue damage and fatigue limits of a GFRP angle-ply laminate tested under very high cycle fatigue loading

International Journal of Fatigue ◽

10.1016/j.ijfatigue.2017.01.045 ◽

2017 ◽

Vol 99 ◽

pp. 202-214 ◽

Cited By ~ 16

Author(s):

T.J. Adam ◽

P. Horst

Keyword(s):

Fatigue Damage ◽

High Cycle Fatigue ◽

Fatigue Loading ◽

Cycle Fatigue ◽

Very High Cycle Fatigue ◽

Very High

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On Fatigue Crack Initiation in the Matrix in Very High Cycle Fatigue Regime

Materials Science Forum ◽

10.4028/www.scientific.net/msf.783-786.2266 ◽

2014 ◽

Vol 783-786 ◽

pp. 2266-2271 ◽

Cited By ~ 1

Author(s):

Guo Cai Chai

Keyword(s):

Fatigue Crack ◽

Crack Initiation ◽

Fatigue Damage ◽

Strain Localization ◽

High Cycle Fatigue ◽

High Strain ◽

Fatigue Crack Initiation ◽

Cycle Fatigue ◽

Very High Cycle Fatigue ◽

Very High

In very high cycle fatigue, VHCF, regime, fatigue crack initiation can occur at subsurface defects such as inclusion or subsurface non-defect (matrix) origin. This paper provides a study on the fatigue crack initiation mechanisms at subsurface non-defect (matrix) origin in two metallic materials using electron backscatter diffraction and electron channeling contrast imaging. The results show that the strains in the material in the VHCF regime were highly localized, where the local maximum strain is greatly higher than the average strain value. This high strain localization can lead to the formation of fine grain zone and also fatigue damage or fatigue crack initiation at grain boundaries or twin boundaries by impingement cracking. High strain localization is caused by strain accumulation of each very small loading, and also increases the local hardness of the material. This may start quasi-cleavage crack origin, and consequently the formation of subsurface fatigue crack initiations. The results also show that fatigue damage and crack initiation mechanisms in the VHCF regime can be different in different metals due to the mechanisms for local plasticity exhaustion.

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Micro Mechanical Behaviors and Damage in Nickel Base Alloy and Steels during Very High Cycle Fatigue

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.258.506 ◽

2016 ◽

Vol 258 ◽

pp. 506-513

Author(s):

Guo Cai Chai

Keyword(s):

Fatigue Damage ◽

High Cycle Fatigue ◽

Base Alloy ◽

Fatigue Crack Initiation ◽

Cycle Fatigue ◽

Nickel Base Alloy ◽

Very High Cycle Fatigue ◽

Nickel Base ◽

Cyclic Plastic Deformation ◽

Very High

Fatigue damage in a metallic material during very high cycle fatigue can strongly be correlated to the microstructure. This paper provides a review and a discussion on the micro damage behaviors in a nickel base alloy and three steels during very high cycle fatigue using micro plasticity and material mechanics. The results show that cyclic plastic deformation in these materials can occur very locally even with an applied stress that is much lower than the yield strength. The fatigue damage occurs mainly at grain or twin boundaries due to local impingement and interaction of slip bands and these boundaries. The crystallographic properties, Schmid factors and orientations of grain and boundaries have very important roles to the fatigue damage. Subsurface fatigue crack initiation in the matrix is one of the mechanisms for very high cycle fatigue. In the fine granular area, high plastic strain localization and cyclic plastic deformation can lead to dislocation annihilation and consequently formation of vacancies, or eventually nanopores at the subcell boundary that leads to fatigue crack initiation and propagation.

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