scholarly journals Elastic-plastic fatigue crack growth under load control (The limit of validity of linear fracture mechanics parameters and the effect of plasticity)

1985 ◽  
Vol 34 (380) ◽  
pp. 561-567
Author(s):  
Masahiro JONO ◽  
Jiho SONG ◽  
Naoki EGUCHI
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Fracture Mechanics ◽  
Crack Growth ◽  
Load Control ◽  
Elastic Plastic ◽  
Linear Fracture Mechanics ◽  
Linear Fracture

Effective Modeling of Fatigue Crack Growth in Pipelines

2012 ◽  
Author(s):  
Steven J. Polasik ◽  
Carl E. Jaske
Keyword(s):  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Fracture Mechanics ◽  
Crack Growth ◽  
Growth Models ◽  
Critical Parameters ◽  
Operating Pressure ◽  
Mechanics Model ◽  
Key Variables

Pipeline operators must rely on fatigue crack growth models to evaluate the effects of operating pressure acting on flaws within the longitudinal seam to set re-assessment intervals. In most cases, many of the critical parameters in these models are unknown and must be assumed. As such, estimated remaining lives can be overly conservative, potentially leading to unrealistic and short reassessment intervals. This paper describes the fatigue crack growth methodology utilized by Det Norske Veritas (USA), Inc. (DNV), which is based on established fracture mechanics principles. DNV uses the fracture mechanics model in CorLAS™ to calculate stress intensity factors using the elastic portion of the J-integral for either an elliptically or rectangularly shaped surface crack profile. Various correction factors are used to account for key variables, such as strain hardening rate and bulging. The validity of the stress intensity factor calculations utilized and the effect of modifying some key parameters are discussed and demonstrated against available data from the published literature.

Fatigue Life Prediction Based on Probabilistic Fracture Mechanics: Case Study of Automotive Parts

2015 ◽  
Vol 2 (1) ◽  
Author(s):  
Mahboubeh Yazdanipour ◽  
Mohammad Pourgol-Mohammad ◽  
Naghd-Ali Choupani ◽  
Mojtaba Yazdani
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Fracture Mechanics ◽  
Crack Growth ◽  
Probabilistic Models ◽  
Fatigue Loading ◽  
Critical Fields ◽  
Propagation Of Uncertainty ◽  
Automotive Parts ◽  
Crack Growth Model

This paper studies the stochastic behavior of fatigue crack growth analytically and empirically by employing basic models in fracture mechanics. The research estimates the crack growth rate probabilistically, quantifies the uncertainty of probabilistic models under fatigue loading in automotive parts, and applies the simulations on W319 aluminum alloy, which has vast applications in automotive components’ products. Walker and Forman correlations are used in the paper. The deterministic simulations of these models are verified with afgrow code and validated experimentally with fatigue data of W319 aluminum. Then, the models are treated probabilistically by considering the models’ parameters stochastic. Monte Carlo (MC) simulation is employed to investigate the models under stochastic conditions. The paper is quantifies the propagation of uncertainty with calculating the standard deviations of crack lengths via cycles. The proposed procedure is useful for selecting a proper probabilistic fatigue crack growth model in specific applications and can be used in future fatigue studies not only in the automotive industry but also in other critical fields, to obtain more reliable conclusions.

Assessment of Pipeline Fatigue Crack-Growth Life

2006 ◽  
Author(s):  
Carl E. Jaske
Keyword(s):  
Fatigue Crack ◽  
Cyclic Loading ◽  
Fatigue Crack Growth ◽  
Fracture Mechanics ◽  
Crack Growth ◽  
Flaw Size ◽  
Stress Intensity Factor Range ◽  
Loading History ◽  
Fatigue Crack Growth Life ◽  
Number Of Cycles

This paper describes an accepted approach for predicting fatigue crack-growth life in pipelines. Fatigue life is computed as the number of cycles for a crack-like flaw to grow from an initial size to a final critical size. This computation is performed by integrating a fracture-mechanics model for fatigue crack growth. The initial flaw size is estimated either from inspection results or by using fracture mechanics to predict the largest flaw that would have survived a hydrostatic pressure test. The final flaw size is estimated using fracture mechanics. Fracture-mechanics models for computing fatigue crack growth and predicting flaw size are reviewed. The anticipated cyclic loading must be characterized to perform the crack-growth calculations. Typically, cyclic loading histories, such as pressure cycle data, are analyzed and used to estimate future loadings. To utilize the crack-growth models, the cycles in the loading history must be counted. The rainflow cycle counting procedure is used to characterize the loading history and develop a histogram of load range versus number of cycles. This histogram is then used in the fatigue crack-growth analysis. Results of example calculations are discussed to illustrate the procedure and show the effects of periodic hydrostatic testing, threshold stress intensity factor range, and pressure ratio on predicted fatigue crack-growth life.

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