A Study on the Degradation of Coating and Corrosion of Ship’s Hull Based on the Probabilistic Approach

1998 ◽  
Vol 120 (3) ◽  
pp. 121-128 ◽  
Author(s):  
N. Yamamoto ◽  
K. Ikegami
Keyword(s):  
Probabilistic Models ◽  
Plate Thickness ◽  
Probabilistic Approach ◽  
Actual Data ◽  
General Corrosion ◽  
Corrosion Model ◽  
Sequential Processes ◽  
Paint Coatings ◽  
Thickness Measurements ◽  
Existing Data

In this paper, phenomena of general corrosion are assumed to be the results of three sequential processes: degradation of paint coatings, generation of pitting point, and progress of pitting point. A consistent corrosion model is proposed which can evaluate the generation and progress of corrosion quantitatively by introducing appropriate simple probabilistic models for each process. This probabilistic corrosion model can be identified by analyzing existing data collected from plate thickness measurements. Applicability of this model is verified by comparing the estimated behavior of corrosion progress and dispersion with those from actual data.

CORRECTION OF PREDICTION MODEL OUTPUT–APPLICATION TO GENERAL CORROSION MODEL

2021 ◽  
Vol 156 (A4) ◽  
Author(s):  
N Hifi ◽  
N Barltrop
Keyword(s):  
Prediction Model ◽  
Reliability Analysis ◽  
Model Calibration ◽  
Structural Reliability ◽  
Prediction Models ◽  
General Corrosion ◽  
Model Output ◽  
Reliability Models ◽  
Corrosion Model ◽  
Recorded Data

This paper applies a newly developed methodology to calibrate the corrosion model within a structural reliability analysis. The methodology combines data from experience (measurements and expert judgment) and prediction models to adjust the structural reliability models. Two corrosion models published in the literature have been used to demonstrate the technique used for the model calibration. One model is used as a prediction for a future degradation and a second one to represent the inspection recorded data. The results of the calibration process are presented and discussed.

Non Parametric Probabilistic Approach of Ice Load Peaks on Ship Hulls

2012 ◽  
Author(s):  
Abdillah Suyuthi ◽  
Bernt J. Leira ◽  
Kaj Riska
Keyword(s):  
Probabilistic Models ◽  
Extreme Values ◽  
Probabilistic Approach ◽  
Initial Distribution ◽  
Complex Phenomenon ◽  
Short Term ◽  
Ship Hulls ◽  
Ice Load ◽  
Non Parametric

Due to its complex phenomenon, ice-induced load process could not be physically possible to be modeled by a specific well established probabilistic model. Therefore, a non parametric approximate probabilistic approach should be performed based on the available data. This paper describes the procedure and also the extrapolation to get the short term and long term extreme values. Comparison with the classical approach, where the initial distribution of ice-induced load is assumed to be one of the well established probabilistic models, was made. The comparisons discussed in this paper were explored by using the same available data of full scale measurement on board a coastal guard vessel KV Svalbard during the winter 2007. There was a tendency that the non parametric approach produces more conservative results.

Probabilistic Models of Reliability of Cast Austenitic Stainless Steel Piping

2011 ◽  
Author(s):  
Haiyang Qian ◽  
David Harris ◽  
Timothy J. Griesbach
Keyword(s):  
Fracture Toughness ◽  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Tensile Properties ◽  
Nuclear Power ◽  
Power Plants ◽  
Probabilistic Models ◽  
Probabilistic Approach ◽  
Delta Ferrite ◽  
Steel Piping

Thermal embrittlement of cast austenitic stainless steel piping is of growing concern as nuclear power plants age. The difficulty of inspecting these components adds to the concerns regarding their reliability, and an added concern is the presence of known defects introduced during the casting fabrication process. The possible presence of defects and difficulty of inspection complicate the development of programs to manage the risk contributed by these embrittled components. Much work has been done in the past to characterize changes in tensile properties and fracture toughness as functions of time, temperature, composition, and delta ferrite content, but this work has shown a great deal of scatter in relationships between the important variables. The scatter in material correlations, difficulty of inspection and presence of initial defects calls for a probabilistic approach to the problem. The purpose of this study is to describe a probabilistic fracture mechanics analysis of the maximum allowable flaw sizes in cast austenitic stainless steel piping in commercial power reactors. Attention is focused on fully embrittled CF8M material, and the probability of failure for a given crack size, load and composition is predicted considering scatter in tensile properties and fracture toughness (fracture toughness is expressed as a crack growth resistance relation in terms of J-Δa). Random loads can also be included in the analysis, with results generated by Monte Carlo simulation. This paper presents preliminary results for CF8M to demonstrate the sensitivity of key input variables. The outcome of this study is the flaw sizes (length and depth) that will fail with a given probability when a given load is applied.

Updating of Probabilistic Corrosion Model Based on Bayesian Procedure

2015 ◽  
Author(s):  
Norio Yamamoto
Keyword(s):  
Bayesian Procedure ◽  
Corrosion Condition ◽  
Frequency Distributions ◽  
Degree Of Belief ◽  
Corrosion Phenomenon ◽  
Corrosion Model ◽  
The Subject ◽  
Thickness Measurements ◽  
Good Agreement ◽  
Corrosion Data

Corrosion condition is predicted based on the corrosion model. The corrosion model is necessary to be identified according to the corrosion data collected from the various vessels because corrosion phenomenon is stochastic. However, in order to predict corrosion condition of one specific vessel, such corrosion model is necessary to be modified to reflect the effect of specific corrosion environment of the subject vessel. In the study, procedure of updating corrosion model was investigated based on Bayesian inference on the parameters in the probabilistic corrosion model which utilizes the thickness measurements data. The developed procedure was demonstrated by the application of actual thickness measurements data of the vessel. Even though the amount of corrosion data was limited, the corrosion prediction model was well updated which could be verified by the concentration of posterior distribution which shows the degree of belief on the parameters in the probabilistic corrosion model. The estimated distributions of coating life and corrosion wastage were compared with the frequency distributions obtained by the corrosion data. The estimated distributions of coating life and corrosion wastage showed good agreement with the frequency distributions obtained by the corrosion data.

Tool-Life Distributions—Part 1: Single-Injury Tool-Life Model

1977 ◽  
Vol 99 (3) ◽  
pp. 519-522 ◽  
Author(s):  
S. Ramalingam ◽  
J. D. Watson
Keyword(s):  
Tool Life ◽  
Manufacturing Systems ◽  
Rational Design ◽  
Probabilistic Models ◽  
Probabilistic Approach ◽  
Distribution Functions ◽  
Automated Manufacturing Systems ◽  
Tool Failure ◽  
Life Model ◽  
Life Distributions

The statistical variability of tool life in production machining must be accounted for in any rational design of large-volume or automated manufacturing systems. The probabilistic approach needed for such a design is presently limited by lack of data on tool-life distributions and by lack of knowledge of the underlying causes giving rise to tool-life scatter. Given these circumstances, on the basis of relevant physical arguments one may construct probabilistic models that produce distribution functions germane to the problem of tool-life scatter. This paper is concerned with such a study. This first part presents the results obtained on the assumption that the useful life of a tool is terminated by a single, catastrophic injury. Cases where resistance to tool failure is time-independent and time-dependent are examined. The case of tool failure caused by multiple injuries will be presented in Part 2.

Simulation of Inspections on Ship Plates With Random Corrosion Patterns

2008 ◽  
Vol 24 (03) ◽  
pp. 168-175
Author(s):  
A. P. Teixeira ◽  
C. Guedes Soares
Keyword(s):  
Random Fields ◽  
Plate Thickness ◽  
Estimation Method ◽  
Thickness Measurement ◽  
Nonlinear Finite Element ◽  
Element Analysis ◽  
Collapse Strength ◽  
Optimal Linear ◽  
Correct Representation ◽  
Thickness Measurements

This paper investigates how the number of thickness measurements and the location of each measurement influence both the correct representation of the level of corrosion and indirectly the correct assessment of the collapse strength of the corroded plates. For this purpose, the corrosion patterns are represented by random fields, which are then discretized using the Expansion Optimal Linear Estimation method. This approach is used to simulate the present practice on thickness measurement patterns and to identify what would be the effect of other strategies of measurement patterns for representing the corrosion in terms of prediction of the average reduction of plate thickness. Finally, the collapse strength of the plates with nonuniform corrosion is calculated by nonlinear finite element analysis and its correlation with the average reduction of plate thickness obtained from the different measurement patterns is assessed.

Probabilistic Models of Reliability of Cast Austenitic Stainless Steel Piping

2012 ◽  
Author(s):  
Haiyang Qian ◽  
David Harris ◽  
Timothy J. Griesbach
Keyword(s):  
Fracture Toughness ◽  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Tensile Properties ◽  
Power Plants ◽  
Probabilistic Models ◽  
Probabilistic Approach ◽  
Ultrasonic Inspection ◽  
Delta Ferrite ◽  
Thermal Embrittlement

The concern of toughness reduction due to thermal embrittlement of cast austenitic stainless steel (CASS) piping is increasing as nuclear power plants age. Because of the large and variable grain size of the CASS materials, the ultrasonic inspection (UT) difficulties of the CASS components increases concerns regarding their reliability. Another added concern is the presence of potential defects introduced during the casting fabrication process. The possible presence of defects and difficulty of inspection complicate the development of programs to manage the risk contributed by these potentially degraded components. Experiments have been performed in the past to evaluate the effect of thermal embrittlement on tensile properties and fracture toughness as functions of time, temperature, composition, and delta ferrite content, but considerable scatter has been shown in the results among the important variables. A probabilistic approach is proposed for the evaluation of the aging effect based on the scatter in material correlations, difficulty of inspection and presence of initial defects. The purpose of this study is to describe a probabilistic fracture mechanics analysis approach for the determination of the maximum allowable flaw sizes in CASS piping components in commercial power reactors, using Monte Carlo simulation. Attention is focused on fully embrittled CF8M material, and the probability of failure for a given crack size, load and composition is predicted considering scatter in tensile properties and fracture toughness (fracture toughness is expressed as a crack growth resistance relation in terms of J-Δa). The correlation between the reduced toughness and increased tensile properties due to thermal embrittlement is also included in the analysis. This paper presents results for CF8M to demonstrate the sensitivity of key input variables on the most severely embrittled material. The output of this study is the flaw size (length and depth) that will fail with a given probability as a function of load and geometry.

A Non-Contact Ultrasonic Sensor for General Corrosion Inspection of Thin Plates

2018 ◽  
Author(s):  
Akinori Tamura ◽  
Masahiro Miki ◽  
Naoyuki Kono ◽  
Hiroshi Okazawa ◽  
Shinobu Okido ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Thin Plate ◽  
Power Plants ◽  
Guided Waves ◽  
Plate Thickness ◽  
Ultrasonic Sensor ◽  
Thin Plates ◽  
Inspection Time ◽  
General Corrosion ◽  
Feasibility Test

In power plants, there are structures made up of thin plates, such as air-conditioning ducts or thin-walled pipes, where corrosion can occur. In this study, we provide a solution to reduce inspection time of the thin plate corrosion measurement and enable monitoring, using a non-contact ultrasonic sensor. The sensor can measure the reduction in thickness of thin plates due to general corrosion without the need to remove or reinstall insulating material that is on the outside of the plate. The proposed sensor is based on the non-contact ultrasonic measurement technique which was originally proposed by Greve et al, further developed and patented by Zhong et al. at the University of Bristol, and commercialized by Inductosense Ltd. In order to ultrasonically measure the thin plate thickness, we use a method based on the group velocity of the guided waves. The proposed method was tested theoretically with numerical simulations and experimentally against our target conditions. The results of the numerical simulations and experiments confirm that the proposed method can be applied to thickness measurements of thin-plates in our target condition. Based on the feasibility test results, we developed a prototype sensor and measurement software. From the results of the performance evaluation tests, we have confirmed that the prototype sensor has sufficient capability to measure the thickness of the thin plates without the removal of the insulator. Even if the offset between the plate and the inspection probe is 100 mm, the prototype sensor still works well.

Updatable Spatio-Temporal Probabilistic Corrosion Modeling for Offshore Structures

2018 ◽  
Author(s):  
Karoline M. Neumann ◽  
Ole Tom Vårdal ◽  
Sören Ehlers
Keyword(s):  
Probabilistic Models ◽  
Offshore Structures ◽  
Current State ◽  
Time Space ◽  
Temporal Models ◽  
Corrosion Model ◽  
Practical Engineering ◽  
Industry Practice ◽  
Spatio Temporal ◽  
Corrosive Environments

Corrosion models are important to assess how the corrosion influences current and future structural strength. For this purpose it is desirable to describe the uneven corrosion diminution of the irregular surface (i.e. space) and progression (i.e. time) in various corrosive environments. Thickness measurements give an indication of the current state, and should be considered in the corrosion model. The inherit uncertainty in corrosion argues for a probabilistic type of corrosion model. Probabilistic models to describe corrosion in time and space, and that can be updated with observations exist, but are typically too complicated for practical engineering use for in-service corrosion assessment. Simpler models exist, that do not describe all of the mentioned aspects (probabilistic, updatable, describe corrosion in time, space and various environments). Here, a simple model covering these aspects is described in two parts. First bayes updating is used to estimate the parameters of the corrosion distribution for each unique environment. The second part uses this resulting distribution and describes how this distribution develops with time. The model is demonstrated with an example and compared to similar spatio-temporal models. The model is promising for improvement from simplistic uniform description of surface and linear progression used in current industry practice.

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