Influence of Frequency on Fretting Fatigue Damage Behavior of Al-Zn-Mg Alloy

nfluence of frequency on fretting fatigue damage behavior of Al-Zn-Mg alloy was studied in this paper. Fretting fatigue lives and damage characteristics of Al-Zn-Mg alloy were researched under different frequencies. Macroscopic tests and microscopic analysis were used to study on influence of frequency on fretting fatigue damage behavior of Al-Zn-Mg alloy. Fatigue lives would be greatly reduced by fretting under the experimental conditions in this paper. With frequency increasing, fretting fatigue lives were firstly decreased and then increased (f=9Hz). Fretting scar, which was the important reason for fretting fatigue crack initiation, was caused by embedding debris; eventually, crack initiated at the edge of the fretting scar. Fretting fatigue fracture is a whole process of crack initiation, propagation and final fracture. And final fracture increased with frequency reducing, which was generally occurred near the center of the fracture.

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Fatigue Damage Behavior Depending on the Bonding Interface Layer in Copper Film Bonded to Base Metals

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.452-453.253 ◽

2010 ◽

Vol 452-453 ◽

pp. 253-256 ◽

Cited By ~ 1

Author(s):

Tashiyuki Torii ◽

Koki Ishida ◽

Mohamed K Hassan ◽

Kenichi Shimizu

Keyword(s):

Crack Initiation ◽

Base Metal ◽

Fatigue Damage ◽

Fatigue Crack Initiation ◽

Interface Layer ◽

Elastic Displacement ◽

Base Metals ◽

Damage Behavior ◽

Significant Difference ◽

Base Steel

Laminated copper films of the epoxy-bonded or diffusion-bonded to the base metal were used in order to investigate and analyze film fatigue behavior depending on the inevitable bonding interfaces for electric/functional parts used in MEMS. Fatigue damage was observed using SEM and crack initiation lives were evaluated at the notch root where the bonding interfaces could be observed directly through the thickness. These observations showed that the resin interface layer caused cracks without slips in a zig-zig pattern and also decreased fatigue crack initiation lives. On the other hand, fatigue damage was observed using an optical microscope on surface of the film with resin bonding or with diffusion bonded interfaces. In this case, many cracks were caused and propagated towards the width direction on the film bonded to the base steel with resin, while slip and cracks were caused along slip lines during fatigue on the film bonded to the base steel by diffusion. There was a significant difference in crack initiation behavior of the films between resin and diffusion bonded to base metals. This finding was not only for crack initiation site but also for roughness near the crack on the film. Using Eulerian equation of motion in continuum, this difference was discussed in terms of elastic displacement field with a wave caused from the base plate subjected to cyclic deformation. Such a wave motion enables us to understand the geometric effects of bonding interfaces on the fatigue damage behavior of the bonded film to base metal.

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Plastic Slip and Early Stage of Fatigue Damage in Polycrystals: Comparison between Experiments and Crystal Plasticity Finite Elements Simulations

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.891-892.1711 ◽

2014 ◽

Vol 891-892 ◽

pp. 1711-1716 ◽

Cited By ~ 1

Author(s):

Loic Signor ◽

Emmanuel Lacoste ◽

Patrick Villechaise ◽

Thomas Ghidossi ◽

Stephan Courtin

Keyword(s):

Fatigue Crack ◽

Finite Elements ◽

Crack Initiation ◽

Fatigue Damage ◽

Crystal Plasticity ◽

Early Stage ◽

Low Cycle Fatigue ◽

Fatigue Cracks ◽

Fatigue Crack Initiation ◽

Plastic Slip

For conventional materials with solid solution, fatigue damage is often related to microplasticity and is largely sensitive to microstructure at different scales concerning dislocations, grains and textures. The present study focuses on slip bands activity and fatigue crack initiation with special attention on the influence of the size, the morphology and the crystal orientation of grains and their neighbours. The local configurations which favour - or prevent - crack initiation are not completely identified. In this work, the identification and the analysis of several crack initiation sites are performed using Scanning Electron Microscopy and Electron Back-Scattered Diffraction. Crystal plasticity finite elements simulation is employed to evaluate local microplasticity at the scale of the grains. One of the originality of this work is the creation of 3D meshes of polycrystalline aggregates corresponding to zones where fatigue cracks have been observed. 3D data obtained by serial-sectioning are used to reconstruct actual microstructure. The role of the plastic slip activity as a driving force for fatigue crack initiation is discussed according to the comparison between experimental observations and simulations. The approach is applied to 316L type austenitic stainless steels under low-cycle fatigue loading.

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Modeling of Fatigue Crack Propagation

Journal of Engineering Materials and Technology ◽

10.1115/1.1631026 ◽

2004 ◽

Vol 126 (1) ◽

pp. 77-86 ◽

Cited By ~ 53

Author(s):

Yanyao Jiang ◽

Miaolin Feng

Keyword(s):

Fatigue Crack ◽

Fatigue Crack Growth ◽

Crack Initiation ◽

Crack Propagation ◽

Crack Growth ◽

Fatigue Damage ◽

Fatigue Crack Propagation ◽

Fatigue Crack Initiation ◽

Cyclic Plasticity ◽

R Ratio

Fatigue crack propagation was modeled by using the cyclic plasticity material properties and fatigue constants for crack initiation. The cyclic elastic-plastic stress-strain field near the crack tip was analyzed using the finite element method with the implementation of a robust cyclic plasticity theory. An incremental multiaxial fatigue criterion was employed to determine the fatigue damage. A straightforward method was developed to determine the fatigue crack growth rate. Crack propagation behavior of a material was obtained without any additional assumptions or fitting. Benchmark Mode I fatigue crack growth experiments were conducted using 1070 steel at room temperature. The approach developed was able to quantitatively capture all the important fatigue crack propagation behaviors including the overload and the R-ratio effects on crack propagation and threshold. The models provide a new perspective for the R-ratio effects. The results support the notion that the fatigue crack initiation and propagation behaviors are governed by the same fatigue damage mechanisms. Crack growth can be treated as a process of continuous crack nucleation.

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