scholarly journals Different Bayesian Methods for Updating the Fatigue Crack Size Distribution in a Tubular Joint

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
H. Khalili ◽  
S. Oterkus ◽  
N. Barltrop ◽  
U. Bharadwaj
Keyword(s):  
Numerical Methods ◽  
Probability Distribution ◽  
Size Distribution ◽  
Fatigue Damage ◽  
Crack Size ◽  
Offshore Platforms ◽  
Additional Information ◽  
Joint Reliability ◽  
Service Lifetime ◽  
Tubular Joint

Abstract Offshore platforms are prone to fatigue damage. To evaluate the fatigue damage, these platforms are periodically inspected during the in-service lifetime. Inspection activities provide additional information, which includes detection and measurement of crack size. A Bayesian framework can be used to update the probability distribution of the uncertain parameters such as crack size. After updating the distribution of the crack size, it is possible to improve the estimation of joint reliability. The main purpose of this study is to present different methods of Bayesian inference to update the probability distribution of the crack size using the inspection results and to demonstrate how the results are different. Two different methods are presented: analytical (conjugate) and numerical methods. The advantages and shortcomings of each method are discussed. To compare the results of the analytical and numerical methods, two different situations are considered; updating the crack size distribution for a particular joint and updating the crack size distribution for several joints that have almost the same conditions. Although the proposed methodology can be applied to different kinds of structures, an example of tubular joints in a specific jacket platform is presented to demonstrate the proposed approach and to compare the results of two methods.

scholarly journals Updating the Distributions of Uncertain Parameters Involved in Fatigue Analysis

2020 ◽  
Vol 8 (10) ◽  
pp. 778
Author(s):  
Hadi Khalili ◽  
Selda Oterkus ◽  
Nigel Barltrop ◽  
Ujjwal Bharadwaj
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Probability Distribution ◽  
Fatigue Damage ◽  
Growth Analysis ◽  
Probability Distributions ◽  
Crack Size ◽  
Probability Of Failure ◽  
Uncertain Parameters ◽  
Tubular Joint

Fatigue is an important failure mode in offshore jacket platforms. To evaluate the fatigue damage, these platforms are periodically inspected during their lifetime. Regarding fatigue damage, the information from inspection consists of crack measurement. A Bayesian framework can be used to update the probability distribution of the crack size. The main purpose of this study is to develop a framework to update the probability distributions of all uncertain parameters involved in the fatigue crack growth analysis. This methodology maximizes the benefit of the inspection results by updating several uncertain parameters involved in the fracture mechanics approach. Two sets of cracks are used to obtain the updated distributions for uncertain parameters; prior cracks and simulated reality cracks. By comparing these cracks, the updated distributions for uncertain parameters are obtained. The updated crack size distribution can be used to update the estimation of the probability of failure. To demonstrate the developed framework, a tubular joint in a specific jacket platform is considered and the framework is applied for that joint. The results of the developed methodology indicate that the updated distributions of uncertain parameters shift towards the simulated reality distributions.

Multidetectors for Analysis of the Composition of Copolymers as a Function of Molecular Size Distribution by Steric Exclusion Chromatography

1973 ◽  
Vol 46 (2) ◽  
pp. 449-463 ◽  
Author(s):  
D. J. Harmon ◽  
V. L. Folt
Keyword(s):  
Liquid Chromatography ◽  
Size Distribution ◽  
Oil Content ◽  
Molecular Size ◽  
The Other ◽  
Additional Information ◽  
Steric Exclusion ◽  
Gel Permeation ◽  
Exclusion Chromatography ◽  
Molecular Size Distribution

Abstract Analysis of molecular size distribution of polymers by steric exclusion liquid chromatography (GPC) is well known. Problems exist, however. These problems involve copolymers and polymer blends. The objectives of the research were to develop methods of analyzing comonomer distribution in copolymers, to study the breakdown of one polymer independent of another in a polymer blend, and to obtain any additional information as might be available. The separations were performed on a Waters Model 200 Gel Permeation Chromatograph. Detectors employed were a Waters R-4 differential refractometer, a Wilks Miran-1 infrared analyzer, and a Beckman Model 144 UV photometer. Examples are given of analysis of average styrene, styrene distribution, and oil content of oil extended SBR. The data is compared with that obtained by other methods. In general the agreement is good. The ability to examine one polymer of a blend independent of the other is also demonstrated. Since elastomers are frequently used as blends, this becomes very important to such studies as milling and extrusion behavior.

RISK-BASED MANAGEMENT OF STRUCTURAL INTEGRITY FOR BASS STRAIT PLATFORMS

2001 ◽  
Vol 41 (1) ◽  
pp. 727
Author(s):  
A.D. Barton
Keyword(s):  
Structural Integrity ◽  
Risk Model ◽  
Offshore Platforms ◽  
Integrity Assessment ◽  
Inspection And Maintenance ◽  
Tubular Joint ◽  
Maintenance Activities ◽  
Consistent Basis ◽  
Inspection Data ◽  
Inspection Techniques

Esso Australia Pty Ltd (Esso) has embraced the framework of risk management to improve the focus and priorities of its inspection and maintenance activities. Structural integrity is one of the disciplines that has adopted a risk-based approach to inspection and integrity assessment and this has been applied to Esso/BHP’s 18 offshore platforms located in Bass Strait.The paper provides a discussion of the issues faced in the management of structural integrity of offshore platforms which lead to the development of a risk-based inspection (RBI) strategy. RBI is applied to improve the prediction of the structures’ condition and provides a consistent basis for continued improvement in the future. The RBI model generates targeted inspection workscopes for each platform that, coupled with the implementation of appropriate inspection techniques, ensure that the integrity of the platforms can be managed with greater confidence and at lower cost.The RBI approach has resulted in reduced focus on traditional areas of uncertainty such as fatigue of tubular joints, and increased focus on secondary structures, for example service caissons. This shift in focus is made possible by building into the risk model a calibration process that considers previous inspection data. A key component of this calibration is a new method developed to calibrate tubular joint fatigue lives.

Sensitivity Analysis of Major Parameters on Piping Failure Probabilities

2004 ◽  
Vol 261-263 ◽  
pp. 821-826
Author(s):  
Sung Gyu Jung ◽  
Chang Soon Lee ◽  
In Gyu Park ◽  
Se Hwan Lee ◽  
Tae Eun Jin
Keyword(s):  
Sensitivity Analysis ◽  
Size Distribution ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Crack Size ◽  
Deterministic Approach ◽  
Inspection Interval ◽  
Different Types ◽  
Failure Probabilities

In-service inspections (ISI) of pipes in the nuclear power plants are currently performed based on mandated requirements in the ASME Section XI, which is based on deterministic approach of the critical welds. The 20 years of ISI experience in U.S.A. has revealed less correlation between the critical welds and actual failures, and much conservatism in current ISI requirements. To reduce those problems, risk-informed ISI technology has been developed and proved to be useful. This paper presented a method for predicting piping failure probabilities in an application of risk-informed ISI, and analyzed the effect of input parameters on piping failure probabilities. Results generated using this approach revealed that the calculated failure probabilities can be sensitive to the different types of stressors, crack size distribution, inspection interval, etc..

NUMERICAL METHODS RESEARCH AND FRACTURE FAILURE ANALYSIS FOR CRITICAL CRACK SIZE

2019 ◽  
Vol 2019.27 (0) ◽  
pp. 1542
Author(s):  
Kaikai SHI ◽  
Xiaoming BAI ◽  
Yanli YUAN ◽  
Liangang ZHENG ◽  
Jianguo CHEN ◽  
...  
Keyword(s):  
Numerical Methods ◽  
Failure Analysis ◽  
Crack Size ◽  
Critical Crack ◽  
Fracture Failure ◽  
Critical Crack Size

Fatigue reliability assessment of tubular joints of existing offshore structures

2001 ◽  
Vol 28 (4) ◽  
pp. 691-698 ◽  
Author(s):  
A A Aghakouchak ◽  
S F Stiemer
Keyword(s):  
Decision Making ◽  
Reliability Assessment ◽  
Offshore Structures ◽  
Fatigue Reliability ◽  
Inspection Planning ◽  
Additional Information ◽  
Linear Elastic ◽  
Tubular Joints ◽  
Elastic Fracture ◽  
Tubular Joint

Tubular joints of offshore structures are prone to fatigue damage. Because of uncertainties involved in quantifying the fatigue process in this type of structure, a reliability approach may be adopted to assess the risks of failure. In-service inspections of structures produce additional information, which may be taken into consideration in order to update the reliability. The paper reviews the methods for carrying out such reliability analyses based on principles of linear elastic fracture mechanics and applies them to a sample tubular joint. The results of this type of analyses may be used for inspection, planning, and (or) decision making regarding repairs or modification of the service life of a structure.Key words: fatigue, reliability, tubular joints, offshore structures, condition assessment.

Numerical evaluation of the transient acoustic waveform due to a point source in a fluid‐filled borehole

Geophysics ◽  
1979 ◽  
Vol 44 (10) ◽  
pp. 1706-1720 ◽  
Author(s):  
Leung Tsang ◽  
Dennis Rader
Keyword(s):  
Numerical Methods ◽  
Point Source ◽  
Numerical Evaluation ◽  
Close Agreement ◽  
Time Windows ◽  
Computation Time ◽  
Head Wave ◽  
Oil Well ◽  
Additional Information ◽  
Frequency Domains

A key measurement employed in oil well wireline logging is the acoustic wave traveltime over a specified formation interval, typically 1 ft. In the traditional measurement, only the compressional head wave is monitored, but for some time it has been obvious that there is significant additional information, such as the shear head wave arrival, in the received waveform. We describe two numerical methods for computing the profile and parameter dependence of the transient waveform based on a model of the acoustic logging problem consisting of a point source on the axis of a fluid‐filled cylindrical borehole. The response to this excitation is determined at a distance from the source, generally on the borehole axis. In the first of the two numerical methods, called “real axis integration”, the complete acoustic waveform is obtained. The second method, called “branch‐cut integration”, evaluates the first compressional and shear‐pseudo‐Rayleigh arrivals individually with much less computation time than the first method. The validity and accuracy of the two methods are demonstrated by their close agreement within appropriate time windows. It is also shown that the results from the ordinary asymptotic method that exist in the literature predict different behavior. The dependence of the transient arrivals on formation parameters is illustrated by various numerical results in both time and frequency domains.

scholarly journals A Multiaxial Notch Fatigue Methodology to Estimate In-Service Lifetime of Corroded Cast Iron Water Pipes

2013 ◽  
Vol 577-578 ◽  
pp. 125-128
Author(s):  
W. Brevis ◽  
Luca Susmel ◽  
J.B. Boxall
Keyword(s):  
Cast Iron ◽  
Fatigue Damage ◽  
Fatigue Loading ◽  
Multiaxial Fatigue ◽  
Variable Amplitude ◽  
Water Pipes ◽  
Service Lifetime ◽  
Curve Method ◽  
Over Time

The present paper summarises an attempt of using the so-called Modified Wöhler Curve Method (MWCM) to estimate fatigue damage in pitted cast iron water pipes subjected to in-service variable amplitude multiaxial fatigue loading. In this setting, pits are treated as hemispherical/hyperbolic notches whose depth increases over time due to conventional corrosion processes taking places in buried cast-iron pipes. The validity of such an approach is proven by showing, through a case study, that, under particular circumstances, the combined effect of corrosion and fatigue can remarkably shorten the in-service lifetime of cast-iron pipes as observed in the case study.

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