scholarly journals Control of fatigue failure mechanisms in multilayer coatings by varying the architectural parameters of an intermetallic interlayer

2021 ◽  
Author(s):  
Songsong Lu ◽  
Richard Cook ◽  
Yi Zhang ◽  
Philippa Reed
Keyword(s):  
Crack Initiation ◽  
Surface Crack ◽  
Intermetallic Layer ◽  
Failure Mechanisms ◽  
Multilayer Coatings ◽  
Coating System ◽  
Fatigue Improvement ◽  
Initiation Mechanism ◽  
Experimental Characterisation ◽  
Surface Crack Initiation

A multilayer overlay coating system containing an intermediate intermetallic layer (designated 2IML) is an architecture expected to show good fatigue resistance. Experimental characterisation and modelling simulations were carried out to classify the different crack initiation mechanisms occurring during fatigue of this coating system and to reveal how changes in the layer architecture lead to fatigue improvement. Fatigue improvement is achieved by decreasing the IML-Top layer thickness due to the increased surface crack initiation resistance. However subsurface initiation mechanisms inhibit the improvement (dominated by surface initiation mechanism) achieved by locating the IML-Top layer closer to the top surface.

Micromechanics Modeling of Crack Initiation Under Contact Fatigue

1994 ◽  
Vol 116 (1) ◽  
pp. 2-8 ◽  
Author(s):  
W. Cheng ◽  
H. S. Cheng ◽  
T. Mura ◽  
L. M. Keer
Keyword(s):  
Crack Initiation ◽  
Surface Crack ◽  
Contact Fatigue ◽  
Contact Boundary ◽  
Dislocation Pileup ◽  
Near Surface ◽  
New Model ◽  
Crack Initiation Life ◽  
Micromechanics Modeling ◽  
Surface Crack Initiation

Using dislocation pileup theory, a model is given for the prediction of crack initiation life under contact fatigue. Near surface crack initiation is investigated by introducing the sliding contact boundary condition. Crack initiation originated at the surface and substrate are treated as extreme cases. The new model physically explains how a surface crack can be initiated and shows that the surface crack initiation life should be shorter than the subsurface crack initiation life under the same stress amplitude conditions. A discussion is given about the influence of residual stress, hardness, temperature, irreversibility of the plastic deformation, as well as other parameters that affect the crack initiation life. Preliminary comparisons show that the new model agrees well with the experimental observations of surface and near surface crack initiation.

Surface Crack Initiation Under Contact Fatigue: Experimental Observation and Contact Analysis

1993 ◽  
Vol 115 (4) ◽  
pp. 658-665 ◽  
Author(s):  
W. Cheng ◽  
H. S. Cheng ◽  
L. M. Keer ◽  
X. Ai
Keyword(s):  
Crack Initiation ◽  
Plastic Zone ◽  
Stress Analysis ◽  
Surface Crack ◽  
Contact Fatigue ◽  
Surface Profile ◽  
Elastohydrodynamic Lubrication ◽  
Contact Analysis ◽  
Hertzian Contact ◽  
Surface Crack Initiation

An experimental study of surface crack initiation was performed by means of a transverse furrow manufactured by the electric discharge machining (EDM) method. Since there is no built-up edge and plastic zone associated with an EDM furrow, the associated stress analysis is relatively simple and provides a reliable means of comparison with experiment. The test results showed that the crack initiation life was not sensitive to the size of the furrow. This phenomenon was explained by means of a micro-elastohydrodynamic lubrication (MEHL) analysis. The calculated results indicated that the pressure peak, Pmax, near the furrow was not sensitive to the depth and width of the furrow, and Pmax could be estimated from the Hertzian contact pressure P0. The more heavily loaded tests showed a newly deformed plastic zone (bump) near the furrow. Two methods were used for the contact simulation. The elastic-plastic contact analysis was selected for the case when a bump was present; otherwise, the MEHL analysis was used. The stress analysis illustrates that the value and the location of the maximum Mises stress was influenced by the friction coefficient and the geometry of the deformed surface profile.

Factors Affecting the Low Cycle Fatigue Behavior around the Weak Axis of Welded I-Section Bracing Members

2006 ◽  
Vol 324-325 ◽  
pp. 959-962
Author(s):  
Yao Chun Zhang ◽  
Wei An Lian ◽  
Wen Yuan Zhang
Keyword(s):  
Fatigue Life ◽  
Energy Dissipation ◽  
Crack Initiation ◽  
Surface Crack ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Cycle Fatigue ◽  
Loading History ◽  
Energy Dissipation Capacity ◽  
Surface Crack Initiation

The low cycle fatigue behavior and energy dissipation capacity around the weak axis of the welded I-section bracing members are investigated by 35 pinned-pinned bracing specimen tests under the axial cyclic loading with different characteristics. Particular attention is paid to the effects of loading amplitude, loading history and geometry properties of these members. It is found that the fatigue damage propagating to fracture in the flanges of the bracing members can be divided into 3 stages involving the macroscopic surface crack initiation, the penetrated crack formation and the penetrated crack propagation. Some empirical formulas to estimate the fatigue life and cyclic energy dissipation capacity of the bracing members are also presented based on the experimental data. The statistical analysis indicates that the fatigue life to surface crack initiation significantly depends on the inelastic local buckling and will increase with decreasing width-thickness ratio of the flanges and increasing slenderness ratios of the bracing members. Besides, it is found that the low cycle fatigue and energy dissipation of these members also depends on loading amplitude and loading history, and the effects of overloads and mean compression amplitude can improve the fatigue performance of bracing members. The test results show that the bracing members with better low-cycle fatigue resistance have the better energy dissipation capacities.

Simulation of Surface Crack Initiation Induced by Slip Localization and Point Defect Kinetics

2014 ◽  
Vol 891-892 ◽  
pp. 542-548 ◽  
Author(s):  
Maxime Sauzay ◽  
Jia Liu
Keyword(s):  
Experimental Data ◽  
Crack Initiation ◽  
Surface Crack ◽  
Strong Relationship ◽  
Recent Experimental Data ◽  
Slip Bands ◽  
Persistent Slip Bands ◽  
Microcrack Initiation ◽  
Physically Based ◽  
Surface Crack Initiation

Crack initiation along surface persistent slip bands (PSBs) has been widely observed and modelled. Nevertheless, from our knowledge, no physically-based fracture modelling has been proposed and validated with respect to the numerous recent experimental data showing the strong relationship between extrusion and microcrack initiation.

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