scholarly journals Multiple Failure Modes Reliability Modeling and Analysis in Crack Growth Life Based on JC Method

2017 ◽  
Vol 2017 ◽  
pp. 1-5 ◽  
Author(s):  
YuanTao Sun ◽  
Chao Liu ◽  
Qing Zhang ◽  
XianRong Qin
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Normal Distribution ◽  
Crack Growth ◽  
Failure Probability ◽  
Failure Modes ◽  
Limit State ◽  
State Equations ◽  
Multiple Failure Modes ◽  
Joint Failure

The fatigue crack growth (FCG) phenomenon generally exists in large mechanical structures. Due to the influences of varied kinds of random factors, the safety evaluation of structure in FCG is under great uncertainty. In this paper, based on the reliability theory, the limit state equations of fracture failure and static strength failure were derived firstly, and the parameters in those equations were regarded as random variables that follow the normal distribution or log-normal distribution. According to the limit state equations, the JC method (equivalent normalizing method) was used to calculate the reliability indexes under the different failure modes of structure in every stress cycle. Based on the reliability indexes and correlation of the two failure modes, the joint failure probability was obtained. In the end, a specific computation example was given, and the curve of joint failure probability in multiple failure modes was used for comparison with the result of single failure mode. The results indicated that the reliability analysis based on multiple failure modes was more reasonable, and the evaluation of reliability could be obtained in fatigue crack growth process.

Reliability Analysis of Fatigue Crack Growth with JC Method Based on Scientific Materials

2011 ◽  
Vol 63-64 ◽  
pp. 882-885 ◽  
Author(s):  
Xiao Li Zou
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Normal Distribution ◽  
Crack Growth ◽  
Reliability Index ◽  
Limit State ◽  
State Equation ◽  
Fatigue Reliability ◽  
Crack Propagation Process ◽  
Log Normal

Since the fatigue crack propagation process from initial size till final fracture is affected by lots of random factors, it is difficult to evaluate the fatigue reliability. Based on reliability theory, the first order second moment method ( JC method) is adopted to analyze and compute the fatigue reliability. To account for the uncertainties of material resistance, the parameters in the deterministic fatigue crack growth rate equation and material fracture toughness are taken as random variables with Normal distribution or Log-Normal distribution. Consequently, the limit state equation of fatigue crack growth is derived. The fatigue reliability index at any moment is calculated iteratively through JC method. As a computation example, the curve of fatigue crack growth reliability index with time is presented.

Fatigue Reliability Assessment of Marine Risers in Deep Offshore Fields in Indian Ocean

2010 ◽  
Author(s):  
Rizwan A. Khan ◽  
Suhail Ahmad
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Deep Sea ◽  
Failure Modes ◽  
New Ventures ◽  
Limit State ◽  
Published Data ◽  
Unstable Fracture ◽  
Fatigue Reliability

Depleting oil reserves in shallow water are opening the avenues of new ventures in deep sea conditions. India is no exception; deep sea explorations are highly recommended and exercised. As part of the design process, there are requirements of structural strength based on criteria referring to failure modes, such as rupture by over loading, fatigue failures, buckling or an unstable fracture. 3D Nonlinear dynamic analysis of riser is obtained in the time domain using finite element solver ABAQUS/Aqua. The response histories so obtained are employed for the study of fatigue reliability analysis of riser. It is based on a bi-linear relationship to model fatigue crack growth and incorporates a failure criterion to describe the interaction between fracture and plastic collapse. Uncertainty modeling, especially on fatigue crack growth parameters, is undertaken with the aid of recently published data in support of the bi-linear crack growth relationship. Results pertaining to fatigue reliability and fatigue crack size evolution are presented using Monte Carlo Simulation. The bi-linear S-N curve and crack growth models are found to lead to higher fatigue life estimation. Sensitivity behavior pertinent to limit state adopted has been thoroughly investigated. These findings implicate inspection schemes for components of the marine structures to ensure minimization of the surprises due to wide scatter of the fatigue phenomenon in marine environment.

Bi-Linear Fatigue and Fracture Approach for Safety Analysis of an Offshore Structure

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
Rizwan A. Khan ◽  
Suhail Ahmad
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Fracture Mechanics ◽  
Crack Growth ◽  
Growth Parameters ◽  
Limit State ◽  
Steel Structures ◽  
Published Data ◽  
Offshore Structure ◽  
Structure Degradation

The design of welded structures for the fatigue limit state is normally carried out by means of either linear or bilinear S-N curves, which have been found adequate to predict crack initiation only. To properly assess the effects of the design, fabrication, inspection, and repair strategy for structure degradation due to crack growth, fracture mechanics (FM) models need to be applied. In this paper, alternative S-N and FM formulations of fatigue are investigated. The probabilistic fracture mechanics approach predicts the fatigue life of welded steel structures in the presence of cracks under random spectrum loading. It is based on a recently proposed bi-linear relationship to model fatigue crack growth. Uncertainty modeling, especially on fatigue crack growth parameters, is undertaken with the aid of recently published data in support of the bilinear crack growth relationship. Results pertaining to the fatigue reliability and fatigue crack size evolution are presented using the Monte Carlo simulation technique and the emphasis is placed on a comparison between the linear and bilinear crack growth models. Variations in the system configuration, service life, and coefficients of crack growth laws have been studied on the parametric basis

Probabilistic Fatigue Safety Analysis of Oil and Gas Risers Under Random Loads

2010 ◽  
Author(s):  
Rizwan A. Khan ◽  
Suhail Ahmad
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Oil And Gas ◽  
Growth Parameters ◽  
Limit State ◽  
Nonlinear Dynamic Analysis ◽  
Fatigue Reliability ◽  
Gas Drilling ◽  
Finite Element Software

Marine riser is an important component of oil and gas drilling and production system. It is essentially a slender pipe conveying fluid between well-head and floating production unit. They are formed out of three basic types of configuration namely, free hanging, “lazy-wave (SWLR)” riser. Risers are subjected to varied static, quasi-static and dynamic forces. For the safety of design, the behavior of the riser under these forces is thoroughly investigated. 3D Nonlinear dynamic analysis of riser is obtained in the time domain using finite element software package ABAQUS/Aqua. The response histories so obtained are employed for the study of fatigue reliability analyses of riser. It is based on a bi-linear relationship to model fatigue crack growth and incorporates a failure criterion to describe the interaction between fracture and plastic collapse. Uncertainty modeling, especially of fatigue crack growth parameters, is undertaken using bi-linear crack growth relationship. Results pertaining to fatigue reliability and fatigue crack size evolution are presented using Monte Carlo Simulation. The bi-linear crack growth models are found to lead to higher fatigue life estimation. Sensitivity behavior pertinent to limit state adopted has been thoroughly investigated. These findings implicate inspection schemes for components of the marine structures to ensure minimization of the surprises due to wide scatter of the fatigue phenomenon in marine environment.

Nonlinear Dynamic and Bilinear Fatigue Performance of Composite Marine Risers in Deep Offshore Fields

2020 ◽  
Author(s):  
Rizwan A. Khan ◽  
Suhail Ahmad
Keyword(s):  
Fatigue Crack ◽  
Crack Growth ◽  
Failure Modes ◽  
Thermal Protection ◽  
Growth Models ◽  
Limit State ◽  
Design Procedure ◽  
Crack Size ◽  
Unstable Fracture ◽  
Fatigue Reliability

Abstract Composite materials have drawn considerable consideration from the offshore business, basically because of their high explicit quality. Notwithstanding weight decrease, composites offer extra advantages, for example, fatigue resistance, damping, and thermal (protection) properties, and high erosion resistance. As a part of design procedure there are requirements of mechanical strength based on criteria referring to failure modes, such as rupture by over loading, fatigue failures, buckling or an unstable fracture. Three dimensional nonlinear assessment of riser is carried out in time domain using ABAQUS/Aqua. The response time histories so obtained are used for the study of fatigue safety assessment of riser. It is based on a bi-linear approach to model fatigue crack growth and incorporates a failure limit to describe the interaction between rupture and plastic failure. Using Monte Carlo Simulation, tests of fatigue reliability and fatigue crack size evolution are obtained. It is observed that bilinear S-N curve and crack growth models leads to higher estimate of fatigue life. Sensitivity behavior pertinent to limit state adopted has been thoroughly examined. These outcomes implicate assessment of components of the marine structures to ensure minimization of the surprises due to wide scatter of the fatigue phenomenon in marine environment.

Scaling of Static Fracture of Quasi-Brittle Structures: Strength, Lifetime, and Fracture Kinetics

2012 ◽  
Vol 79 (3) ◽  
Author(s):  
Jia-Liang Le ◽  
Zdeněk P. Bažant
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Size Effect ◽  
Crack Growth ◽  
Failure Probability ◽  
Structural Strength ◽  
Chain Model ◽  
Weakest Link

The paper reviews a recently developed finite chain model for the weakest-link statistics of strength, lifetime, and size effect of quasi-brittle structures, which are the structures in which the fracture process zone size is not negligible compared to the cross section size. The theory is based on the recognition that the failure probability is simple and clear only on the nanoscale since the probability and frequency of interatomic bond failures must be equal. The paper outlines how a small set of relatively plausible hypotheses about the failure probability tail at nanoscale and its transition from nano- to macroscale makes it possible to derive the distribution of structural strength, the static crack growth rate, and the lifetime distribution, including the size and geometry effects [while an extension to fatigue crack growth rate and lifetime, published elsewhere (Le and Bažant, 2011, “Unified Nano-Mechanics Based Probabilistic Theory of Quasibrittle and Brittle Structures: II. Fatigue Crack Growth, Lifetime and Scaling,” J. Mech. Phys. Solids, 1322–1337), is left aside]. A salient practical aspect of the theory is that for quasi-brittle structures the chain model underlying the weakest-link statistics must be considered to have a finite number of links, which implies a major deviation from the Weibull distribution. Several new extensions of the theory are presented: (1) A derivation of the dependence of static crack growth rate on the structure size and geometry, (2) an approximate closed-form solution of the structural strength distribution, and (3) an effective method to determine the cumulative distribution functions (cdf’s) of structural strength and lifetime based on the mean size effect curve. Finally, as an example, a probabilistic reassessment of the 1959 Malpasset Dam failure is demonstrated.

Effect of Bi-Linear S-N Curve and Crack Growth Law on the Safety Analyses of Welded Joints of an Offshore Structure

2008 ◽  
Author(s):  
Rizwan A. Khan ◽  
Suhail Ahmad
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Fatigue Crack Growth ◽  
Fracture Mechanics ◽  
Crack Growth ◽  
Limit State ◽  
Published Data ◽  
Offshore Structure ◽  
Structure Degradation ◽  
Crack Growth Model

Design of welded structures for fatigue limit state is normally carried out by means of either linear or bilinear S-N curves which have been found adequate to predict crack initiation only. To properly assess the effects of design, fabrication, inspection and repair strategy for structure degradation due to crack growth, Fracture mechanics (FM) models need to be applied. In this paper, alternative S-N and FM formulations of fatigue are investigated. Probabilistic fracture mechanics approach predicts the fatigue life of welded steel structure in the presence of cracks under random spectrum loading. It is based on a recently proposed bi-linear relationship to model fatigue crack growth and incorporates a failure criterion to describe the interaction between fracture and plastic collapse. Uncertainty modeling, especially on fatigue crack growth parameters, is undertaken with the aid of recently published data in support of the bilinear crack growth relationship. Results pertaining to fatigue reliability and fatigue crack size evolution are presented using the Monte Carlo Simulation Technique, and emphasis is placed on a comparison between linear and bi-linear crack growth models. The bi-linear S-N curve and crack growth model are found to lead to higher fatigue life estimates and shows sensitivity to many other parameters in addition to the stress state of the component. These findings implicate inspection schemes for components of the marine structures to ensure minimization of the surprises due to wide scatter of the fatigue phenomenon in marine environment. Variations in system configuration, service life and coefficients of crack growth laws have been studied on the parametric basis.

Probabilistic Fracture Mechanics Assessment of Welded Joints of Offshore Structure Using a Bilinear Crack Growth Law

2008 ◽  
Author(s):  
Rizwan A. Khan ◽  
Suhail Ahmad
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Fatigue Crack Growth ◽  
Fracture Mechanics ◽  
Crack Growth ◽  
Limit State ◽  
Published Data ◽  
Offshore Structure ◽  
Probabilistic Fracture Mechanics ◽  
Crack Growth Model

Design of welded structures for fatigue limit state is normally carried out by means of either linear or bilinear S-N curves approaches. To properly assess the effects of design, fabrication, inspection and repair strategy for structures degradation due to crack growth, Fracture mechanics (FM) models need to be applied. This paper deals with the application of a probabilistic fracture mechanics approach to predict the fatigue life of welded steel structure in the presence of cracks under random spectral loading. It is based on a BS7910 [1] proposed bi-linear relationship to model fatigue crack growth and incorporates a failure criterion to describe the interaction between fracture and plastic collapse. Uncertainty modeling, especially of fatigue crack growth parameters, is undertaken with the aid of recently published data in support of the bi-linear crack growth relationship. Results pertaining to fatigue reliability and fatigue crack size evolution are presented using the Monte Carlo Simulation technique, and emphasis is placed on a comparison between linear and bi-linear crack growth models. The bi-linear crack growth model is found to lead to higher fatigue life estimates and shows sensitivity to many other parameters in addition to the state of stress of the component. This leads to implications on inspection schemes for components of the marine structures and to ensure minimization of the surprises due to wide scatter of the fatigue phenomenon in marine environment. Variations in the system configuration, service life and coefficients of crack growth laws have been studied on the parametric basis.

A discrete dislocation analysis of fatigue crack growth

2001 ◽  
Vol 11 (PR5) ◽  
pp. Pr5-69-Pr5-75
Author(s):  
V. S. Deshpande ◽  
H. H.M. Cleveringa ◽  
E. Van der Giessen ◽  
A. Needleman
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Discrete Dislocation
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