Safety factors in structural integrity assessment of components with defects

2013 ◽  
Vol 4 (4) ◽  
pp. 457-476 ◽  
Author(s):  
Yury Matvienko
Keyword(s):  
Fracture Mechanics ◽  
Safety Factor ◽  
Structural Integrity ◽  
Plastic Collapse ◽  
Safety Factors ◽  
Content Type ◽  
Nonlinear Fracture Mechanics ◽  
Integrity Assessment ◽  
Nonlinear Fracture ◽  
Linear And Nonlinear

Purpose – The purpose of this paper is to develop basic principles of deterministic structural integrity assessment of a component with a crack- or notch-like defect by including safety factors against fracture and plastic collapse in criteria equations of linear and nonlinear fracture mechanics. Design/methodology/approach – The safety factors against fracture are calculated by demanding that the applied critical stress should not be less than the yield stress of the material for a component with a crack or a notch of the acceptable size. Structural integrity assessment of the engineering components damaged by crack- or notch-like defects is discussed from view point of the failure assessment diagram (FAD). The methodology of the FAD has been employed for the structural integrity analysis and assessment of acceptable sizes of throw-thickness notch in a plate under tension and surface longitudinal notch-like defects in a pressure vessel. Findings – Basic equations have been presented to calculate the safety factor against fracture for critical values of the stress intensity factor, crack tip opening displacement (CTOD), the J-integral and the FAD as well as to estimate an acceptable (safe) region for an engineering component with a crack- or notch-like defect of the acceptable size. It was shown that safety factors against fracture depend on both the safety factor against plastic collapse and employed fracture mechanics criterion. The effect of crack/notch tip constraint is incorporated into criteria equations for the calculation of safety factors against fracture. Originality/value – The deterministic method of fracture mechanics is recommended for structural integrity assessment of a component with a crack- or notch-like defect by including safety factors against fracture and plastic collapse in criteria equations of linear and nonlinear fracture mechanics.

Reliability-Based Derivation of Partial Safety Factor for Structural Integrity Assessment

2008 ◽  
Author(s):  
Shuo Pan ◽  
Jianping Zhao
Keyword(s):  
Safety Factor ◽  
Fracture Mode ◽  
Structural Integrity ◽  
Research Work ◽  
Random Variables ◽  
Assessment Procedure ◽  
Safety Factors ◽  
Integrity Assessment ◽  
Partial Safety Factor ◽  
Partial Safety Factors

When there are uncertainties in the input random variables, or scatter in the material properties, probabilistic assessment is a useful tool for decision making in the field of safety analysis. The partial safety factor (PSF) method was aimed on ensuring that the failure probability did not exceed a target value. In order to be conservative the input value for each random variable during the assessment procedure should be multiplied by the partial safety factors. So it is essentially a deterministic assessment using conservative values of the input random variables and a relatively simple and independent method of assessing failure probabilities using R6 failure assessment diagram. The application of partial safety factors is an important breakthrough of assessment in structures containing defects. In recent years, sets of PSFs for load, defect size, fracture toughness and yield stress had been given in two standards, BS7910 and API579. However, the recommended PSFs in both standards were larger than the original PSFs in PD6493 which was replaced by BS7910. It is therefore a new method of calculating PSFs should be found to prove which is more appropriate and convenient for engineering application. In the case of the partial safety factor method target reliabilities in the range from 0.001 to 0.00001 were considered and new series of PSFs were derived from the results of reliability analysis for the linear elastic fracture mode and elastic-plastic fracture mode. After comparing with the PSFs in BS7910 and API 579, it is concluded that the partial safety factors were generally conservative compared to our research work.

Use of linear and nonlinear fracture mechanics for assessing resistance to crack propagation in 15Kh2NMFA structural steel

1978 ◽  
Vol 10 (1) ◽  
pp. 38-42
Author(s):  
A. Ya. Krasovskii ◽  
V. A. Vainshtok ◽  
Yu. A. Kashtalyan ◽  
V. A. Stepanenko ◽  
A. N. Vashchenko ◽  
...  
Keyword(s):  
Fracture Mechanics ◽  
Crack Propagation ◽  
Structural Steel ◽  
Nonlinear Fracture Mechanics ◽  
Nonlinear Fracture ◽  
Linear And Nonlinear

Program complex for solving problems of linear and nonlinear fracture mechanics. I

1987 ◽  
Vol 19 (4) ◽  
pp. 553-559 ◽  
Author(s):  
E. M. Morozov ◽  
G. P. Nikishkov ◽  
B. R. Beizerman ◽  
Yu. I. Smirnov ◽  
T. A. Chernysh ◽  
...  
Keyword(s):  
Fracture Mechanics ◽  
Program Complex ◽  
Nonlinear Fracture Mechanics ◽  
Nonlinear Fracture ◽  
Linear And Nonlinear

Complex study of the fracture processes in materials and structures

2018 ◽  
Vol 84 (11) ◽  
pp. 46-51 ◽  
Author(s):  
N. A. Makhutov
Keyword(s):  
Fracture Mechanics ◽  
Crack Resistance ◽  
Scientific Basis ◽  
Intensity Factors ◽  
Nonlinear Fracture Mechanics ◽  
Nonlinear Fracture ◽  
Linear Fracture ◽  
Science Technology ◽  
Fracture Processes

The results of comprehensive studies of multifactor processes, mechanisms and criteria for fracture at a variation of the crack-like defect state, loading conditions and mechanical properties of structural materials carried out in the 20th - 21st centuries are presented on the basis of monographic publications and articles published in the journal “Zavodskaya Laboratoriya. Diagnostika Materialov.” Crack resistance of materials and structures has become a key problem of the material science, technology, design, manufacture and service of structures. Fracture mechanics including estimation of the stress-strain and limiting states in a cracks tip formed a scientific basis of the crack resistance analysis Stress intensity factors (linear fracture mechanics) and strain intensity factors (nonlinear fracture mechanics) are accepted as the basic criteria of those states. The basic computational relations for construction of the fracture diagrammes which link the cracks growth with conditions of a static, cyclic, long-term, dynamic loading are presented. Parameters of computational relations are put into correspondence with the features of fracture processes on nano-, micro-, meso- and macrolevels. Prospects of the research and guidelines of further studing crack resistance are discussed.

Nonlinear Fracture Mechanics Analysis Considering Material Inhomogeneity of Welded Joints

Impact ◽  
2019 ◽  
Vol 2019 (10) ◽  
pp. 105-107
Author(s):  
Hiroshi Okada
Keyword(s):  
Fracture Mechanics ◽  
Solid Mechanics ◽  
Crack Nucleation ◽  
Intensity Factors ◽  
Nonlinear Fracture Mechanics ◽  
Material Inhomogeneity ◽  
Computational Fracture Mechanics ◽  
New Methods ◽  
Nonlinear Fracture ◽  
Mechanics Analysis

Professor Hiroshi Okada and his team from the Department of Mechanical Engineering, Faculty of Science and Technology, Tokyo University of Science, Japan, are engaged in the field of computational fracture mechanics. This is an area of computational engineering that refers to the creation of numerical methods to approximate the crack evolutions predicted by new classes of fracture mechanics models. For many years, it has been used to determine stress intensity factors and, more recently, has expanded into the simulation of crack nucleation and propagation. In their work, the researchers are proposing new methods for fracture mechanics analysis and solid mechanics analysis.

Structural Integrity for Nuclear Power Plant Against Excessive Load on Design Extension Condition

2013 ◽  
Author(s):  
Daigo Watanabe ◽  
Kiminobu Hojo
Keyword(s):  
Nuclear Power ◽  
Structural Integrity ◽  
Safety Factors ◽  
Design Code ◽  
Acceptance Criteria ◽  
Integrity Assessment ◽  
Current Design ◽  
Factor Design ◽  
Excessive Load ◽  
Load And Resistance Factor

This paper introduces an example of structural integrity evaluation for Light Water Reactor (LWR) against excessive loads on the Design Extension Condition (DEC). In order to assess the design acceptance level of DEC, three acceptance criteria which are the stress basis limit of the current design code, the strain basis limit of the current design code and the strain basis limit by using Load and Resistance Factor Design (LRFD) method were applied. As a result the allowable stress was increased by changing the acceptance criteria from the stress basis limit to the strain basis limit. It is shown that the practical margin of the LWR’s components still keeps even on DEC by introducing an appropriate criterion for integrity assessment and safety factors.

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