A cumulative failure probability model for cleavage fracture in ferritic steels

2016 ◽  
Vol 93 ◽  
pp. 184-198 ◽  
Author(s):  
Wei-Sheng Lei
Keyword(s):  
Cleavage Fracture ◽  
Failure Probability ◽  
Probability Model ◽  
Ferritic Steels

scholarly journals A Statistical Model of Cleavage Fracture Toughness of Ferritic Steel DIN 22NiMoCr37 at Different Temperatures

Materials ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 982 ◽  
Author(s):  
Guian Qian ◽  
Wei-Sheng Lei ◽  
Zhenfeng Tong ◽  
Zhishui Yu
Keyword(s):  
Fracture Toughness ◽  
Yield Strength ◽  
Statistical Model ◽  
Cleavage Fracture ◽  
Failure Probability ◽  
Ferritic Steel ◽  
Ferritic Steels ◽  
Local Approach ◽  
Weibull Statistics ◽  
Different Temperatures

It is a conventional practice to adopt Weibull statistics with a modulus of 4 for characterizing the statistical distribution of cleavage fracture toughness of ferritic steels, albeit based on a rather weak physical justification. In this study, a statistical model for cleavage fracture toughness of ferritic steels is proposed according to a new local approach model. The model suggests that there exists a unique correlation of the cumulative failure probability, fracture toughness and yield strength. This correlation is validated by the Euro fracture toughness dataset for 1CT specimens at four different temperatures, which deviates from the Weibull statistical model with a modulus of four.

Analytical failure probability model for generic gravity dam classes

2017 ◽  
Vol 231 (5) ◽  
pp. 546-557 ◽  
Author(s):  
Mohammad Amin Hariri-Ardebili
Keyword(s):  
Failure Probability ◽  
Safety Assessment ◽  
Statistical Approach ◽  
Probability Model ◽  
Gravity Dam ◽  
Preliminary Design ◽  
Failure Model ◽  
Proposed Model ◽  
Dimensional Gravity ◽  
Demand And Capacity

Risk analysis of concrete dams and quantification of the failure probability are important tasks in dam safety assessment. The conditional probability of demand and capacity is usually estimated by numerical simulation and Monte Carlo technique. However, the estimated failure probability (or the reliability index) is dam-dependent which makes its application limited to some case studies. This article proposes an analytical failure model for generic gravity dam classes which is optimized based on large number of nonlinear finite element analyses. A hybrid parametric–probabilistic–statistical approach is used to estimate the failure probability as a function of dam size, material distributional models and external hydrological hazard. The proposed model can be used for preliminary design and evaluation of two-dimensional gravity dam models.

The Weibull Stress Model for Predicting Cleavage Fracture in the Ductile-to-Brittle Transition Region

2008 ◽  
Author(s):  
Xiaosheng Gao ◽  
Jason P. Petti ◽  
Robert H. Dodds
Keyword(s):  
Fracture Toughness ◽  
Transition Region ◽  
Cleavage Fracture ◽  
Model Parameters ◽  
Ferritic Steels ◽  
Stress Model ◽  
Brittle Transition ◽  
Ductile To Brittle Transition ◽  
Constraint Effects ◽  
Weibull Stress

Transgranular cleavage fracture in the ductile-to-brittle transition region of ferritic steels often leads to spectacular and catastrophic failures of engineering structures. Due to the strongly stochastic effects of metallurgical scale inhomogenieties together with the nonlinear mechanical response from plastic deformation, the measured fracture toughness data exhibit a large degree of scatter and a strong dependence on constraint. This has stimulated an increasing amount of research over the past two decades, among which the Weibull stress model originally proposed by the Beremin group has gained much popularity. This model is based on weakest link statistics and provides a framework to quantify the relationship between macro and microscale driving forces for cleavage fracture. It has been successfully applied to predict constraint effects on cleavage fracture and on the scatter of macroscopic fracture toughness values. This paper provides a brief review of the research conducted by the authors in recent years to extend the engineering applicability of the Weibull stress model to predict cleavage fracture in ferritic steels. These recent efforts have introduced a threshold value in the Weibull stress model, introduced more robust calibration methods for determination of model parameters, predicted experimentally observed constraint effects, demonstrated temperature and loading rate effects on the model parameters, and expanded the original Beremin model to include the effects of microcrack nucleation.

Application of FTRF in Cascading Failure Probability Model in Adverse Weather

2013 ◽  
Vol 336-338 ◽  
pp. 471-474
Author(s):  
Shi Guang ◽  
Hai Jing Yang ◽  
Qi Wei Wang ◽  
Yan Jin
Keyword(s):  
Failure Probability ◽  
Power Flow ◽  
Transition Probability ◽  
Probability Model ◽  
First Line ◽  
Line Load ◽  
State Transfer ◽  
Adverse Weather ◽  
Load Rate ◽  
Transition Probability Model

In allusion to the issues of system line state transfer that may arise in adverse weather, a new method of probability calculation is proposed. In a statistical analysis, this article firstly defines that failure probability of the first line subjects to Poisson distribution. Secondly, we figure out the power flow transferring distribution after first line fault, according to the method of Flow Transferring Relativity Factor (FTRF), and combine with the protective possibility so as to build the probability model between the load rate and protection action. Then, the method defines the severity of line load rate. Finally, the approach constructs the line state transition probability model considering direct and indirect factors in adverse weather. The effectiveness and correctness of the proposed method are verified by simulation based on IEEE 39-node system.

Recent Developments and Challenges of Cleavage Fracture Modelling in Steels: Aspects on Microstructural Mechanics and Local Approach Methods

2019 ◽  
Author(s):  
Quanxin Jiang ◽  
V. M. Bertolo ◽  
V. A. Popovich ◽  
Carey L. Walters
Keyword(s):  
Fracture Toughness ◽  
Cleavage Fracture ◽  
Structural Integrity ◽  
State Of The Art ◽  
Structural Steels ◽  
Ferritic Steels ◽  
Local Approach ◽  
Microstructural Parameters ◽  
Recent Developments ◽  
Size Scales

Abstract Offshore activity in low-temperature areas requires the use of analysis methods that are capable of reliably predicting cleavage (brittle) fracture of ferritic steels in order to guarantee the structural integrity during service. Cleavage fracture is controlled by physical events at different size scales and is influenced by the multiple microstructural parameters of the material. The prediction of fracture toughness of steels based on the microstructure has received great attention, and relevant techniques have been continuously developed. This paper is aimed at reviewing the recent development of cleavage fracture modelling in steels and identifying the existing challenges to inspire further research. The paper contains three parts aimed at explaining how methods are developed and utilized to predict fracture toughness of steel from its microstructures. (1) The complex multiparametric nature of the microstructures of ferritic steels and its influence on cleavage fracture is introduced. (2) A review is given on the main perspectives and models in micromechanisms of cleavage fracture in steels. (3) Discussion is contributed to the link between micromechanisms and the local approach in cleavage fracture modelling. As a result, the paper gives a state of the art on microstructural mechanics and local approach methods of cleavage fracture modelling in structural steels.

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