Determination of Material Constants for Crack Size-Dependence Crack Growth Model

A crack size-dependence crack growth model was used to characterise the fatigue crack growth in AL 7075-T6 and AL 2024-T351 alloys. It is shown that the crack growth parameters %K and a can be used to linearise the crack growth in regions I (elastic) and II (plastic) by plotting fatigue data linear-linear da/dN×√a versus %K3, where cubic stress dependency is assumed. A theoretical attempt was made to relate this crack size-dependence fatigue crack growth parameters to the strain-life relationship constants. A reasonably good agreement was achieved when comparing between the theoretical predicted and experimental determined material constants.

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On the concept of Multiregion Crack Growth

MRS Proceedings ◽

10.1557/proc-531-243 ◽

1998 ◽

Vol 531 ◽

Cited By ~ 3

Author(s):

S. L. Semjonov ◽

M. M. Bubnov

Keyword(s):

Crack Growth ◽

Growth Model ◽

Correct Determination ◽

Crack Growth Model ◽

Dynamic Fatigue

AbstractThe effect of the two-region crack growth model on the static and dynamic fatigue curves for strong and abraded fibers is studied. The additional requirements to static and dynamic fatigue experiments necessary for the correct determination of the fatigue parameters are discussed.

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An Equivalent Creep Crack Growth Model for Probabilistic Life Prediction of Plastic Pipe Materials

Journal of Pressure Vessel Technology ◽

10.1115/1.4045792 ◽

2020 ◽

Vol 142 (3) ◽

Author(s):

Yuhao Wang ◽

Tishun Peng ◽

Ernest Lever ◽

Yongming Liu

Keyword(s):

Experimental Data ◽

Crack Growth ◽

Growth Model ◽

Life Prediction ◽

Creep Crack Growth ◽

Creep Damage ◽

Crack Size ◽

Initial Crack ◽

Local Geometry ◽

Crack Growth Model

Abstract Life prediction in energy infrastructure such as gas pipelines is important to maintain the integrity of such systems. This paper explores a life prediction model for polyethylene materials in natural gas distribution pipelines under creep damage. The model uses a power law equation to describe the crack growth rate and an asymptotic solution for the stress intensity factor (SIF) calculation considering local geometry variations. The SIF solution considers the effect of stress concentration introduced by common damages in pipes such as rock impingement and slit. An effective initial crack size model is proposed for the life prediction of plastic pipes considering the intrinsic initial defect. Large loading-induced plastic deformation is included by a correction factor in the crack growth model. The model is calibrated and validated using experimental data on Aldyl-A pipes with different types of damage. Due to the stochastic nature of the crack growth process, uncertainty quantification is performed, and Monte Carlo (MC) simulation is used to estimate the failure probability. The predicted probabilistic life distributions under different loading conditions are compared with the experimental data. Some conclusions and future work are drawn based on the proposed study and experimental validation.

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The Fatigue Life Prediction Methodology Based on the Unigrow Model

Volume 14: Emerging Technologies; Safety Engineering and Risk Analysis; Materials: Genetics to Structures ◽

10.1115/imece2015-53693 ◽

2015 ◽

Cited By ~ 1

Author(s):

Sergey Bogdanov ◽

Semyon Mikheevskiy ◽

Grzegorz Glinka

Keyword(s):

Fatigue Crack ◽

Fatigue Crack Growth ◽

Crack Growth ◽

Growth Model ◽

Crack Problem ◽

Crack Size ◽

Engineering Structure ◽

Time Required ◽

Crack Growth Model ◽

Total Life

This paper is concerned with the problem of prediction of the total life of an engineering structure based on the fatigue crack growth model. The life of an engineering component is generally modeled as a combination of the time required for a crack to initiate and then the time required for crack to propagate till the final fracture. Unfortunately the crack initiation size is a vaguely defined parameter. In order to overcome this ambiguity it is proposed to model the total life of an engineering structure by using the UniGrow fatigue crack growth model with assumption of the intrinsic material parameter ρ* as an initial crack size. The method to overcome the small crack problem in fatigue crack modeling is presented as well. The proposed model was successfully used to predict fatigue lives of misaligned cruciform welded joints under a constant amplitude loading. Results from the analysis and experiment are in a good agreement.

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Formulation of a Polynomial Stochastic Fatigue Crack Growth Model

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.909.467 ◽

2014 ◽

Vol 909 ◽

pp. 467-471 ◽

Cited By ~ 6

Author(s):

C.C. Ni

Keyword(s):

Distribution Function ◽

Fatigue Crack ◽

Fatigue Crack Growth ◽

Crack Growth ◽

Growth Model ◽

Analytical Solutions ◽

Growth Function ◽

Crack Size ◽

Model Parameters ◽

Crack Growth Model

The study is focused on the formulation of a proposed polynomial stochastic fatigue crack growth model. Assuming the fatigue crack growth rate equal to a deterministic polynomial function in terms of fatigue crack size multiplied by a stationary lognormal random factor accounting for the statistical scatter of the fatigue crack growth, the analytical solutions of fatigue crack growth function and median crack growth function in term of model parameters were derived. Two extreme cases, lognormal random variable and lognormal white noise, of the proposed model were also investigated, and the analytical solutions of the distribution function of the random crack size at any service time and distribution function of random time to reach a specified crack size were obtained.

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