Applications of a Probabilistic Fracture Mechanics Model to the Influence of In-Service Inspection on Structural Reliability

2009 ◽  
pp. 19-19-23 ◽  
Author(s):  
DO Harris ◽  
EY Lim
Keyword(s):  
Fracture Mechanics ◽  
Structural Reliability ◽  
Probabilistic Fracture Mechanics ◽  
Mechanics Model ◽  
Service Inspection

Probabilistic Fracture Mechanics Structural Reliability Analysis of Reeled Pipes

2006 ◽  
Author(s):  
Hugo A. Ernst ◽  
Ricardo Schifini ◽  
Richard E. Bravo ◽  
Diego N. Passarella ◽  
Federico Daguerre ◽  
...  
Keyword(s):  
Fracture Mechanics ◽  
Reliability Analysis ◽  
Structural Reliability ◽  
Crack Size ◽  
Probability Of Failure ◽  
Statistical Distribution ◽  
Assessment Procedure ◽  
Statistical Distributions ◽  
Probabilistic Fracture Mechanics ◽  
Structural Reliability Analysis

Structural integrity analyses are used to guarantee the reliability of critical engineering components under certain conditions of interest. In general, the involved parameters have statistical distributions. Choosing a single set of values for the parameters of interest does not show the real statistical distribution of the output parameters. In particular, offshore pipes installation by reeling is a matter of concern due to the severe conditions of the process. Since it is necessary to guarantee the integrity of the pipes, a probabilistic fracture mechanics reliability analysis seems to be the most adequate approach. In this work, a probabilistic fracture mechanics assessment approach to perform the structural reliability analysis of tubes subjected to a reeling process was developed. This procedure takes into account the statistical distributions of the material properties and pipe geometry, using a fracture mechanics approach and the Monte Carlo method. Two-parameter Weibull distributions were used to model the variability of the input parameters. The assessment procedure was implemented as a self-contained executable program. The program outputs are: the statistical distribution of critical crack size, amount of crack extension, final crack size and the cumulative probability of failure for a given crack size. A particular case of interest was studied; a seamless tube - OD 323.9 × wt 14.3 mm, was analyzed. Tolerable defect size limits (defect depth vs. defect length curves) for different probability of failure levels were obtained. A sensitivity analysis was performed; the effect of material fracture toughness and misalignment was studied.

scholarly journals Random Outcome and Stochastic Analysis of Some Fatigue Crack Growth Data

2001 ◽  
Vol 17 (2) ◽  
pp. 61-68
Author(s):  
W. F. Wu ◽  
C. C. Ni ◽  
H. Y. Liou
Keyword(s):  
Fatigue Crack ◽  
Fracture Mechanics ◽  
Crack Size ◽  
Experimental Result ◽  
Exceedance Probability ◽  
Growth Data ◽  
Probabilistic Fracture Mechanics ◽  
Mechanics Model ◽  
Proposed Model ◽  
Analytical Result

ABSTRACTFatigue crack propagation data of a batch of AISI 4340 steel specimens are released in the present paper. The statistical nature of the data is specially emphasized, and a probabilistic fracture mechanics model is introduced to analyze the data. The stochastic differential equation associated with the model is then solved. The solution gives us the crack exceedance probability as well as the probability distribution of the random time to reach a specified crack size. These quantities are useful in the reliability assessment of structures made of the tested material. Comparing the analytical result with the experimental result, it is found that the proposed probabilistic fracture mechanics model can reasonably explain the experimental data. For those data that cannot be fitted well by the proposed model, methods of improvement are proposed in the present paper as well.

Probabilistic Prediction of Crack Depth Distributions Observed in Structures Subjected to Thermal Fatigue

2006 ◽  
Author(s):  
Tai Asayama ◽  
Hideki Takasho ◽  
Takehiko Kato
Keyword(s):  
Fracture Mechanics ◽  
Thermal Fatigue ◽  
Structural Reliability ◽  
Evaluation Method ◽  
Crack Depth ◽  
Inspection Planning ◽  
Probabilistic Fracture Mechanics ◽  
Nuclear Plants ◽  
Depth Distributions ◽  
Failure Probabilities

The application of risk-based technologies not only to inservice inspections but also to the design of components and systems, encompassing a plant life-cycle, is the way to be pursued for the improvement of design of new reactors such as fast breeder reactors. When doing so it is necessary to develop an analytical method that is capable of estimating failure probabilities without a failure database that can only be established on the long-time accumulation of operational experiences. The prediction method should estimate failure probabilities based on actual mechanisms that cause failure. For this purpose, this study developed a probabilistic structural reliability evaluation method for fatigue which is a representative failure mode to be prevented in components of nuclear plants. This method is an extension of probabilistic fracture mechanics approach but is capable of modeling crack initiation, crack propagation, as well as crack depth density distribution at a given cycle. To verify the methodology, crack depth distribution observed in thermal fatigue test specimens were evaluated, and it was shown that the method could reproduce the observed crack depth distributions fairly well. This is considered to explore the possibility that probabilistic fracture mechanics approach can be verified by experiments, which was deemed impossible so far. Further improvement such as explicit implementation of interaction mechanisms between adjacent cracks will allow this methodology to be applied to the procedure of optimization of inservice inspection planning, as well as to the optimization of safety factors in component design of nuclear plants.

Probabilistic Fracture Mechanics Methodology Applied to Pipes Subjected to Multiple Reeling Cycles

2007 ◽  
Author(s):  
Hugo A. Ernst ◽  
Richard E. Bravo ◽  
Ricardo Schifini ◽  
Diego N. Passarella
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Fracture Mechanics ◽  
Reliability Analysis ◽  
Crack Growth ◽  
Structural Reliability ◽  
Probabilistic Fracture Mechanics ◽  
Assessment Approach ◽  
Pipe Geometry ◽  
Cyclic Plastic Deformation

Reeling process is one of the more used methods for installations of linepipes in recent years. Pipes are welded onshore and subsequently reeled onto a drum. During installation, the line is unreeled, straightened, and then laid into the sea. The pipe is subjected to severe cyclic plastic deformation. Due to the characteristics of the process, it is necessary to guarantee the integrity of the components during and after the process. For this reason, structural reliability analyses are essential requirements. In a previous work [1], a fracture mechanics based methodology was developed to obtain a method to assess the structural reliability of reeled pipes. The problem of several reeling cycles was considered. In addition to a fracture mechanics methodology, a formulation considering fatigue crack growth (FCG) controlled by ΔJ parameter was developed. This formulation accounts for the crack growth produced during subsequent reeling cycles. In another work [2], a probabilistic fracture mechanics assessment approach to perform the structural reliability analysis of tubes subjected to a reeling process was developed. This procedure takes into account the statistical distributions of the material properties and pipe geometry, using a fracture mechanics approach and the Monte Carlo method. In this work, the probabilistic fracture mechanics approach was applied for the case of multiple reeling cycles that includes ΔJ-based fatigue crack growth and reliability analysis. A particular case of interest was studied and tolerable defect sizes were determined for different number of reeling cycles taking into account the parameters variability.

Structural Integrity Evaluation of Reactor Pressure Vessels During PTS Events Using Deterministic and Probabilistic Fracture Mechanics Analysis

2013 ◽  
Author(s):  
Kazuya Osakabe ◽  
Hiroyuki Nishikawa ◽  
Koichi Masaki ◽  
Jinya Katsuyama ◽  
Kunio Onizawa
Keyword(s):  
Fracture Mechanics ◽  
Structural Reliability ◽  
Structural Integrity ◽  
Probabilistic Approach ◽  
Crack Size ◽  
Initial Crack ◽  
Pressure Vessels ◽  
Probabilistic Fracture Mechanics ◽  
Main Steam Line ◽  
Main Steam

To assess the structural integrity of reactor vessels (RVs) during pressurized thermal shock (PTS) events, a deterministic fracture mechanics (DFM) approach has been widely used such as the procedure in JEAC4206-2007. On the other hand, the application of a probabilistic fracture mechanics (PFM) analysis method for the structural reliability assessment of RV has become attractive recently because uncertainties related to input parameters can be incorporated rationally. The probabilistic approach has already been adopted as the regulation on fracture toughness requirements against PTS events in the U.S. In this paper, in order to verify the applicability of a PFM method to JEAC4206-2007, deterministic and probabilistic analyses have been performed, and the effects of initial crack size defined in JEAC4206-2007 on the temperature margin obtained from DFM and the probability of crack initiation obtained from PFM have been evaluated. With regard to the PTS event variation, a stuck open valve scenario (SO) has been considered in addition to large- and small-break loss of coolant accident (LBLOCA, SBLOCA) and main steam line break (MSLB).

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