Finite weakest-link model of lifetime distribution of quasibrittle structures under fatigue loading

2013 ◽  
Vol 19 (1) ◽  
pp. 56-70 ◽  
Author(s):  
Jia-Liang Le ◽  
Zdeněk P. Bažant
Keyword(s):  
Fatigue Loading ◽  
Lifetime Distribution ◽  
Weakest Link ◽  
Link Model

A Mathematical Model for Competing Failure Modes in Strain Cycle Fatigue

2006 ◽  
Vol 129 (2) ◽  
pp. 293-303 ◽  
Author(s):  
Gerald T. Cashman
Keyword(s):  
Failure Modes ◽  
High Stress ◽  
Local Strain ◽  
Initiation Site ◽  
Weakest Link ◽  
Strain Relationship ◽  
Powder Metallurgy Alloy ◽  
Link Model ◽  
Cyclic Plastic Strain ◽  
Selection Of

Elevated temperature data for powder metallurgy alloy René 95 generated in vacuum are presented to demonstrate that the life differences observed between surface and internally initiated failures are due to an environmental effect. The transition in behavior from a mode at low stress dominated by internal initiations to a surface dominated mode at high stress is quantitatively described in terms of both a weakest-link model and a local strain relationship. A fatigue failure mechanism is provided that explains that the natural selection of initiation site is based upon the concept that the site displaying the highest local cyclic plastic strain is the location where fatigue initiates.

Lifetime Prediction of Components Including Initiation Phase

2006 ◽  
Author(s):  
Michael Besel ◽  
Angelika Brueckner-Foit
Keyword(s):  
Input Data ◽  
Local Stress ◽  
Fatigue Loading ◽  
Computer Code ◽  
Lifetime Distribution ◽  
Element Analysis ◽  
Initiation Phase ◽  
Mechanics Model ◽  
Critical Regions ◽  
Local Stress Field

The lifetime distribution of a component subjected to fatigue loading is calculated using a micro-mechanics model for crack initiation and a fracture mechanics model for crack growth. These models are implemented in a computer code which uses the local stress field obtained in a Finite Element analysis as input data. Elemental failure probabilities are defined which allow to identify critical regions and are independent of mesh refinement. An example is given to illustrate the capabilities of the code. Special emphasis is put on the effect of the initiation phase on the lifetime distribution.

Reliability of Welded Structures Containing Cracks in Heat-Affected Zones

2000 ◽  
Vol 122 (4) ◽  
pp. 225-232 ◽  
Author(s):  
David B. Lanning ◽  
M.-H. Herman Shen
Keyword(s):  
Fracture Toughness ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Crack Front ◽  
Surface Crack ◽  
Material Properties ◽  
Coarse Grained ◽  
Welded Structures ◽  
Weakest Link ◽  
Link Model

This study investigates the reliability of a plate containing a semi-elliptical surface crack intersecting regions of dissimilar material properties. A weakest-link model is developed to express fracture toughness distributions in terms of effective crack lengths that account for the varying stress intensity factor along the crack front. The model is intended to aid in the development of fracture toughness distributions for cracks encountering local brittle zones (LBZ) in the heat-affected zones (HAZ) of welded joints, where lower-bound fracture toughness values have been measured in the laboratory when a significant portion of the crack front is intersecting the coarse-grained LBZs. An example reliability analysis is presented for a surface crack in a material containing alternating bands of two Weibull-distributed toughnesses. [S0892-7219(00)01203-6]

A Weakest-Link Model for the Prediction of Fatigue Crack Growth Rate

1978 ◽  
Vol 100 (2) ◽  
pp. 170-174 ◽  
Author(s):  
Kong Ping Oh
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Average Rate ◽  
Joint Probability ◽  
Random Variable ◽  
Weakest Link ◽  
Link Theory ◽  
Link Model ◽  
Joint Probability Density

A weakest-link theory is proposed for analyzing the rate of fatigue crack growth. The joint probability density of a fatigue crack growing an amount X between x and x+dx, and in time η between N and N+dN cycles is derived from an initial probability function. The rate of crack growth is then obtained as the expectation of the random variable (X/η). It is shown that the average rate of crack growth obeys the power law for small ΔK, and that the power is a function of the shape parameter in the Weibull distribution.

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