An application of s-version FEM to fracture mechanics problems : elastic-plastic analysis

2003 ◽  
Vol 2003.16 (0) ◽  
pp. 599-600 ◽  
Author(s):  
Hiroshi OKADA ◽  
Sayaka ENDOH ◽  
Masanori KIKUCHI
Keyword(s):  
Fracture Mechanics ◽  
Elastic Plastic ◽  
Plastic Analysis

Computational Aspect of Nonlinear Fracture Mechanics Application

2015 ◽  
Author(s):  
Igor Orynyak ◽  
Andrii Oryniak
Keyword(s):  
Residual Stress ◽  
Fracture Mechanics ◽  
Thermal Stresses ◽  
Crack Tip ◽  
Pressure Vessels ◽  
Point Of View ◽  
Computational Aspect ◽  
J Integral ◽  
Elastic Plastic ◽  
Plastic Analysis

The development of powerful commercial computer programs made the concept of J-integral as computational parameter of fracture mechanics to be a very attractive one. It is equivalent to SIF in linear case, it converges in numerical calculation and the same results are obtained by different codes (programs). Besides, it is widely thought that elastic-plastic analysis gives bigger values than elastic SIF ones what is good from regulatory point of view. Such stand was reflected in the recommended by IAEA TECDOC 1627 (February 2010) devoted to pressurized thermal shock analysis of reactor pressure vessels, where the embedded crack in FEM mesh, elastic-plastic analysis with simultaneous determination of J-integral was stated as the best option of analysis. But at that time all the most widely used software were not able to treat the residual stresses, the thermal stresses in case of two different materials. Such a contradiction between requirements and the possibilities made a lot of problems for honest contractors especially in countries where the regulator had no own experience in calculation and completely relied on the authority of international documents. This means that at that time the said recommendations were harmful. The main reason of such a situation was the absence of the carefully elaborated examples. Now the capabilities and accuracy of such software are increasing. Nevertheless, some principal ambiguities and divergences of computations results in various J-integral contours around the crack tip still exist. They are exhibited when the large plastic zone emerges at the crack tip. Other problem is influence of the history of loading and the specification of the time of crack insertion in the mesh including the time of emergence of residual stress. This paper is invitation for discussion of the accuracy and restriction of computational J-integral. With this aim the detailed analysis of some simplified 2D examples of calculation of elastic -plastic J-integral for surface crack with accounting for residual stress, thermal stress and inner pressure are performed and commented. The attainment of consensus among the engineering society for treating the outcome results is the prerequisite for practical application of computational elastic plastic J-integral.

Comparison of Evolution Fatigue With Simplified Elastic Plastic Analysis, Plastic Analysis and a Fracture Mechanics Approach

2020 ◽  
Author(s):  
Joakim Cedergren
Keyword(s):  
Fatigue Life ◽  
Fracture Mechanics ◽  
Strain Range ◽  
Axial Direction ◽  
Total Strain ◽  
Slow Heating ◽  
Total Strain Range ◽  
Elastic Plastic ◽  
Plastic Analysis ◽  
Pipe Geometry

Abstract Fatigue analyzes are performed to ensure that no damage leading to failure will occur in a component. In ASME III NB-3222.4(e), a method is provided for analyzing a component’s resistance against cyclic loads. In ASME NB-3228.5 or alternatively NB-3653.6 (c) a simplified elastic-plastic method is given to take plasticity into account. According to NB-3228.4 (c), fatigue evaluation is allowed with plastic analysis where the stress amplitude is determined from the numerically maximum principal total strain range. This report examines the fatigue life, using a continuum mechanics approach, of a pipe penetration that is subjected to a rapid cooling down followed by a slow heating up. Simplified elastic-plastic analysis and plastic analysis are performed. The analysis also takes into account the FEN-factor according to the method given NUREG/CR6909. The fatigue life is also determined by a fracture mechanics approach using a R6 based fracture assessment and crack growth analysis. The results show a large difference in fatigue life depending on the method used. For the plastic analyzes it is of great importance to the result in which direction the evaluation is made. For the present case the maximum principal total strain range is obtained in the radial direction. The stresses in this direction are small. A crack tangentially to this direction lacks physical significance to a pipe geometry and cannot lead to failure. In this case it is recommended that evaluation is made for the strain range in the axial direction for pipe geometries instead of the maximum principal total strain range.

scholarly journals In-situ elastic-plastic fracture mechanics on the microscale by means of continuous dynamical testing

2018 ◽  
Vol 148 ◽  
pp. 177-187 ◽  
Author(s):  
Markus Alfreider ◽  
Darjan Kozic ◽  
Otmar Kolednik ◽  
Daniel Kiener
Keyword(s):  
Fracture Mechanics ◽  
Elastic Plastic

Reactor Pressure Vessel Integrity Assessment: French Simplified Analysis Method Applied to Underclad Postulated Defect in Nozzle

2016 ◽  
Author(s):  
Adolfo Arrieta-Ruiz ◽  
Eric Meister ◽  
Stéphane Vidard
Keyword(s):  
Fracture Mechanics ◽  
Fracture Risk ◽  
Pressure Vessel ◽  
Reactor Pressure Vessel ◽  
Core Area ◽  
Integrity Assessment ◽  
Elastic Plastic ◽  
The Core ◽  
Simplified Method ◽  
Reactor Pressure

Structural integrity of the Reactor Pressure Vessel (RPV) is one of the main concerns regarding safety and lifetime of Nuclear Power Plants (NPP) since this component is considered as not reasonably replaceable. Fast fracture risk is the main potential damage considered in the integrity assessment of RPV. In France, deterministic integrity assessment for RPV vis-à-vis the brittle fracture risk is based on the crack initiation stage. As regards the core area in particular, the stability of an under-clad postulated flaw is currently evaluated under a Pressurized Thermal Shock (PTS) through a dedicated fracture mechanics simplified method called “beta method”. However, flaw stability analyses are also carried-out in several other areas of the RPV. Thence-forward performing uniform simplified inservice analyses of flaw stability is a major concern for EDF. In this context, 3D finite element elastic-plastic calculations with flaw modelling in the nozzle have been carried out recently and the corresponding results have been compared to those provided by the beta method, codified in the French RSE-M code for under-clad defects in the core area, in the most severe events. The purpose of this work is to validate the employment of the core area fracture mechanics simplified method as a conservative approach for the under-clad postulated flaw stability assessment in the complex geometry of the nozzle. This paper presents both simplified and 3D modelling flaw stability evaluation methods and the corresponding results obtained by running a PTS event. It shows that the employment of the “beta method” provides conservative results in comparison to those produced by elastic-plastic calculations for the cases here studied.

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