Roles of deformation twinning and dislocation slip in the fatigue failure mechanism of AZ31 Mg alloys

2010 ◽  
Vol 63 (7) ◽  
pp. 747-750 ◽  
Author(s):  
J. Koike ◽  
N. Fujiyama ◽  
D. Ando ◽  
Y. Sutou
Keyword(s):  
Failure Mechanism ◽  
Fatigue Failure ◽  
Deformation Twinning ◽  
Mg Alloys ◽  
Dislocation Slip

scholarly journals Characterization of Deformation Mechanisms in Mg Alloys by Advanced Acoustic Emission Methods

Metals ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 644 ◽  
Author(s):  
Jan Čapek ◽  
Michal Knapek ◽  
Peter Minárik ◽  
Jan Dittrich ◽  
Kristián Máthis
Keyword(s):  
Acoustic Emission ◽  
Microstructural Analysis ◽  
Deformation Twinning ◽  
Mg Alloys ◽  
Deformation Mechanisms ◽  
Dislocation Slip ◽  
Initial Texture

Adaptive sequential k-means (ASK) analysis of acoustic emission (AE) data was used to analyze the sources of AE during compression of three AZ31 magnesium samples with different initial texture. The results were compared to the classical hit-based approach. Observation of the deformed microstructure shows that the ASK analysis can distinguish very well between the signal originating in deformation twinning and dislocation slip. Moreover, together with microstructural analysis, the ASK algorithm revealed another source of AE for one of the samples, which was shown to be the double twinning.

The Fatigue and Degradation Mechanisms of Wire Ropes Bending-over-Sheaves

2011 ◽  
Vol 127 ◽  
pp. 344-349
Author(s):  
Zhi Hui Hu ◽  
Ji Quan Hu
Keyword(s):  
Failure Mechanism ◽  
Fatigue Failure ◽  
Mechanical Damage ◽  
Wire Rope ◽  
Stress Conditions ◽  
Degradation Mechanisms ◽  
Bending Fatigue ◽  
Wire Ropes ◽  
Combined Action

Fatigue failure behaviors caused by wire ropes bending-over-sheaves are discussed in the paper. Stress conditions of wire ropes bending-over-sheaves and the mechanism of damage to wire rope caused by fleet angel and angle of wrap is analyzed, the fatigue failure mechanism of wire ropes is investigated in the paper. The investigation indicates that the load and the mechanical damage of ropes bending-over-sheaves is very complex, and the fatigue failure of ropes bending-over-sheaves is the result of combined action of bending fatigue and various kinds of damage. The research will have implications to design and use of wire rope.

scholarly journals Crossover from Deformation Twinning to Lattice Dislocation Slip in Metal–Graphene Composites with Bimodal Structures

Crystals ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 47
Author(s):  
Nikolai V. Skiba
Keyword(s):  
Plastic Deformation ◽  
Metal Matrix ◽  
Deformation Twinning ◽  
Lattice Dislocation ◽  
Dislocation Slip ◽  
Dislocation Emission ◽  
Bimodal Structure ◽  
Graphene Nanocomposite ◽  
Relaxation Channel ◽  
Micrometer Size

Theoretical model is suggested, which describes of a new micromechanism of crossover from deformation twinning to lattice dislocation slip in metal–graphene nanocomposite with a bimodal structure. In the framework of the model, the lattice dislocation slip occurs through emission of lattice dislocations from the disclinated grain boundary fragments between a nanocrystalline metal–matrix and large (micrometer-size) grains providing the plastic deformation of bimodal metal–graphene nanocomposite. It is shown that the lattice dislocation emission serves as an effective stress relaxation channel being in competition with nanocrack generation.

Quantitative Relationship between Strain and Acoustic Emission Response in Monitoring Fatigue Damage

2013 ◽  
Vol 66 (1) ◽  
Author(s):  
M. Mohammad ◽  
S. Abdullah ◽  
N. Jamaludin ◽  
O. Innayatullah
Keyword(s):  
Acoustic Emission ◽  
Failure Mechanism ◽  
Fatigue Failure ◽  
Quantitative Relationship ◽  
Steel Specimen ◽  
Cyclic Fatigue ◽  
Steel Component ◽  
Specific Data ◽  
The Relationship ◽  
Ae Signals

This study was carried out to investigate the relationship between the strain and acoustic emission (AE) signals, thus, to confirm the capability of AE technique to monitor the fatigue failure mechanism of a steel component. To achieve this goal, strain and AE signals were captured on the steel specimen during the cyclic fatigue test.  Both signals were collected using specific data acquisition system by attaching the strain gauge and AE piezoelectric transducer simultaneously at the specimen during the test. The stress loading used for the test was set at 600 MPa, and the specimens were fabricated using the SAE 1045 carbon steel.  The related parameters for both signals were determined at every 2000 seconds until the specimen failed.  It was found that a meaningful correlation of all parameters, i.e. amplitude, kurtosis and energy, was established. Finally, all AE parameters are correlated with the damage values, which have been estimated using the Coffin-Manson model.  Hence, it was suggested that the AE technique can be used as a monitoring tool for fatigue failure mechanism in a steel component.

Microstructure Evolution of Near Gamma TiAl Intermetallic under Tensile Impact Loadings at High Temperatures

2010 ◽  
Vol 146-147 ◽  
pp. 1553-1556
Author(s):  
Yu Wang ◽  
Xiang Zan ◽  
Yue Hui He ◽  
Yang Wang
Keyword(s):  
Strain Rate ◽  
Microstructure Evolution ◽  
Deformation Mode ◽  
Deformation Twinning ◽  
Stacking Fault ◽  
Effect Of Temperature ◽  
Dislocation Slip ◽  
Tem Analysis ◽  
Dynamic Loadings ◽  
Deformation Modes

The effect of temperature and strain rate on the mechanical behavior and microstructure evolution of Near Gamma Ti-46.5Al-2Nb-2Cr (NG TiAl) was investigated at temperatures ranging from room temperatures to 840 under strain rates of 0.001, 320, 800 and 1350s-1. The TEM analysis indicated that deformation twinning and stacking fault are the main deformation modes under dynamic loadings and dislocation slip is another important deformation mode under quasi-static loadings. The density of deformation twinning and/or stacking fault increases with the increased temperature and strain rate.

Experimental and Numerical Investigation of Torsion Fatigue of Bearing Steel

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
John A. R. Bomidi ◽  
Nick Weinzapfel ◽  
Trevor Slack ◽  
Sina Mobasher Moghaddam ◽  
Farshid Sadeghi ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Crack Initiation ◽  
Normal Stress ◽  
Failure Mechanism ◽  
Fatigue Damage ◽  
Fatigue Failure ◽  
Damage Mechanics ◽  
Damage Model ◽  
Bearing Steel ◽  
Fatigue Damage Accumulation

This paper presents the results of torsion fatigue of widely used bearing steels (through hardening with bainite, martensite heat treatments, and case hardened). An MTS torsion fatigue test rig (TFTR) was modified with custom mechanical grips and used to evaluate torsional fatigue life and failure mechanism of bearing steel specimen. Tests were conducted on the TFTR to determine the ultimate strength in shear (Sus) and stress cycle (S-N) results. Evaluation of the fatigue specimens in the high cycle regime indicates shear driven crack initiation followed by normal stress driven propagation, resulting in a helical crack pattern. A 3D finite element model was then developed to investigate fatigue damage in torsion specimen and replicate the observed fatigue failure mechanism for crack initiation and propagation. In the numerical model, continuum damage mechanics (CDM) were employed in a randomly generated 3D Voronoi tessellated mesh of the specimen to provide unstructured, nonplanar, interelement, and inter/transgranular paths for fatigue damage accumulation and crack evolution as observed in micrographs of specimen. Additionally, a new damage evolution procedure was implemented to capture the change in fatigue failure mechanism from shear to normal stress assisted crack growth. The progression of fatigue failure and the stress-life results obtained from the fatigue damage model are in good agreement with the experimental results. The fatigue damage model was also used to assess the influence of topological microstructure randomness accompanied by material inhomogeneity and defects on fatigue life dispersion.

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