Technical Bases for Alternative Stress Evaluation Criteria in Japan Based on Partial Inelastic Analyses

2004 ◽  
Author(s):  
Seiji Asada ◽  
Asao Okamoto ◽  
Isoharu Nishiguchi ◽  
Mitsuru Aoki ◽  
Yasuhide Asada
Keyword(s):  
Finite Element Analysis ◽  
Evaluation Criteria ◽  
Cyclic Loads ◽  
Collapse Load ◽  
Element Analysis ◽  
Stress Evaluation ◽  
Inelastic Analysis ◽  
Plastic Analysis ◽  
Load Analysis ◽  
Fatigue Evaluation

An Alternative Stress Evaluation Criteria suitable for Finite Element Analysis using inelastic analysis has been developed. The Alternative Criteria prescribes evaluations for Primary Loads, Cyclic Loads and Fatigue. Collapse load analysis is used for the evaluation of Primary Loads. The evaluation for Cyclic Loads consists of Shakedown Evaluation and Thermal Ratchet Evaluation. The 2xY method is applied to Simplified Elastic-Plastic Analysis in Fatigue Evaluation. In this paper, the major technical bases of these evaluations are described.

scholarly journals Collapse load analysis for circumferentially cracked cylinder subjected to combined torsion and bending moments

2018 ◽  
Vol 192 ◽  
pp. 02024
Author(s):  
Sutham Arun ◽  
Thongchai Fongsamootr
Keyword(s):  
Finite Element Analysis ◽  
Limit Load ◽  
Failure Strength ◽  
Bending Moments ◽  
Collapse Load ◽  
Welding Zone ◽  
Element Analysis ◽  
Strength Assessment ◽  
Load Analysis ◽  
Cracked Cylinder

Cylinder is one of the most commonly used components which has a risk of having circumferential cracks, especially in the welding zone. When cracks are discovered, it is necessary to perform the failure strength assessment of cracked cylinder and the limit load play an important part as the input of the assessment. At present, the limit load solution for circumferential cracked cylinder under combined bending and torsion can be estimated by using the methods of equivalent moment or biaxial failure parameter. However, these methods still have some limitations. The main aim of this paper is to propose the alternative method for predicting the failure moment of circumferential cracked cylinder under combined bending and torsion. The method used in this paper is based on the modification of biaxial failure parameter and the data from finite element analysis. Details of this method is presented in this paper.

Alternative Approaches for ASME Code Simplified Elastic-Plastic Analysis

2017 ◽  
Author(s):  
Sampath Ranganath ◽  
Nathan A. Palm
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Correction Factor ◽  
Element Analysis ◽  
Elastic Plastic ◽  
Plastic Analysis ◽  
Asme Code ◽  
Alternative Approaches ◽  
Fatigue Evaluation ◽  
Technical Basis

Subsection NB, Section III of the ASME Code provides rules for the fatigue evaluation of nuclear pressure vessel and piping components. The stress analysis in ASME code evaluation is generally based on linear elastic analysis. Simplified rules using an elastic-plastic strain correction factor, Ke, are provided in Section III to account for plastic yielding when the primary plus secondary stress intensity range exceeds the 3Sm limit. While the simplified elastic-plastic analysis rules are easy to apply and do not require nonlinear analysis, the application of the Ke correction factor can produce extremely conservative results. This paper investigates different analytical methods that are available for simplified elastic-plastic analysis and proposes an alternative method that is not overly conservative (compared to the Code Ke) and offers a more realistic approach to simplified elastic-plastic analysis. The proposed methodology is applicable for both vessel (NB-3200), core support structures (NG-3200) and piping components (NB-3600) and does not require new finite element analysis. Information in existing ASME Code stress reports should be sufficient to determine the new Ke factor. The proposed methodology is applicable to structural materials including austenitic stainless steel and nickel based alloys, carbon steel and low alloy steel. Comparison of the proposed methodology with detailed elastic-plastic finite element analysis shows that the new Ke factors are conservative but offer relief from the excessive conservatism in the Code Ke values. This paper provides the technical basis for an ASME draft Code Case for Alternative Approaches for ASME Code Simplified Elastic-plastic Analysis being pursued through the Section III ASME Code Committees.

Finite Element Analysis of Local Inelastic Strain Based on Stress Redistribution Locus

2008 ◽  
Author(s):  
Shunji Kataoka ◽  
Takuya Sato
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Thermal Loading ◽  
Failure Modes ◽  
Elevated Temperatures ◽  
Pressure Vessels ◽  
Stress Redistribution ◽  
Strain Diagram ◽  
Element Analysis ◽  
Inelastic Analysis

Creep-fatigue damage is one of the dominant failure modes for pressure vessels and piping used at elevated temperatures. In the design of these components the inelastic behavior should be estimated accurately. An inelastic finite element analysis is sometimes employed to predict the creep behavior. However, this analysis needs complicated procedures and many data that depend on the material. Therefore the design is often based on a simplified inelastic analysis based on the elastic analysis result, as described in current design codes. A new, simplified method, named, Stress Redistribution Locus (SRL) method, was proposed in order to simplify the analysis procedure and obtain reasonable results. This method utilizes a unique estimation curve in a normalized stress-strain diagram which can be drawn regardless of the magnitude of thermal loading and constitutive equations of the materials. However, the mechanism of SRL has not been fully investigated. This paper presents results of the parametric inelastic finite element analyses performed in order to investigate the mechanism of SRL around a structural discontinuity, like a shell-skirt intersection, subjected to combined secondary bending stress and peak stress. This investigation showed that SRL comprises a redistribution of the peak and secondary stress components and that although these two components exhibit independent redistribution behavior, they are related to each other.

User’s Design Specification Preparation for 2¼Cr-1Mo-¼V Reactors in Accordance With ASME Section VIII, Division 2 Code and Code Case 2605

2013 ◽  
Author(s):  
Radoslav Stefanovic ◽  
Alicia Avery ◽  
Kanhaiya Bardia ◽  
Reza Kabganian ◽  
Vasile Oprea ◽  
...  
Keyword(s):  
Operating Temperature ◽  
Design Specification ◽  
Element Analysis ◽  
Analysis And Evaluation ◽  
Reheat Cracking ◽  
Inelastic Analysis ◽  
Allowable Stresses ◽  
Section Viii ◽  
Fatigue Evaluation ◽  
Division 2

Today’s hydroprocessing reactor manufacturers use 2¼Cr–1Mo–¼V steel to build lighter reactors than conventional Cr-Mo reactors. Manufacturing even lighter hydroprocessing reactors has been enabled with the introduction of the new ASME Section VIII Division 2 Code, initially released in 2007. The higher allowable stresses in the new Division 2 for these Vanadium-modified steels permits even lighter reactors to be built while maintaining suitable design margins. The new Division 2 Code requires additional engineering to ensure safe design. One of the challenges the engineer is faced with, is preparation of the User’s Design Specification (UDS) including new and more stringent requirements for fatigue evaluation. As the operating temperature of the rector is higher than 371°C, engineers have to evaluate the fatigue life of the reactor in accordance with Code Case 2605 (CC2605). CC2605 requires inelastic analysis and evaluation effects of creep. Vanadium-modified reactors require additional care during fabrication to prevent higher hardness around weld areas, reheat cracking, and reduced toughness at lower temperatures in the “as welded” condition. This paper provide guidance for the preparation of an ASME Section VIII Division 2 User’s Design Specification including process descriptions of all the cycles expected for the life of the rector and analysis requested by CC2605. An example of such an analysis, including finite element analysis results, is provided in this paper. Requirements to provide the material specification is also discussed with an emphasis on prevention of reheat cracking, hardenability, and temper and hydrogen embitterment.

Review of FE-Based Fatigue Evaluation Methods for the Rib to Floorbeam Welds in Orthotropic Bridge Decks

2014 ◽  
Vol 627 ◽  
pp. 337-340
Author(s):  
Wouter de Corte ◽  
Arne Jansseune
Keyword(s):  
Evaluation Method ◽  
Hot Spot ◽  
Bridge Decks ◽  
High Stress ◽  
International Institute ◽  
Element Analysis ◽  
Stress Evaluation ◽  
Linear Elastic ◽  
Mesh Density ◽  
Fatigue Evaluation

Complex welded structures such as bridges are very often designed with the help of FE analysis. However, one should remain cautious when using such an analysis, since the results are mesh sensitive, with especially the mesh density and the element type influencing the results. In addition, these results are in most cases retrieved in hot spot areas with high stress gradients, where the maximum stress even cannot be correctly determined with linear elastic finite element analysis. For that reason, a stress evaluation method is required to obtain relevant stress levels that can be directly related to fatigue detailing. The most complete set of stress evaluation recommendations is given in the Recommendations for Fatigue Design of Welded Joints and Components from the International Institute of Welding. Nevertheless, several authors have recently commented on the difficulties regarding the application of these methods for the rib to floorbeam welds in orthotropic bridge decks. This paper provides findings for this type of connections based on both shell and solid model analysis and relates these findings to work from other authors.

Probing the Instability of a Cluster of Slip Bonds Upon Cyclic Loads With a Coupled Finite Element Analysis and Monte Carlo Method

2014 ◽  
Vol 81 (11) ◽  
Author(s):  
Xiaofeng Chen ◽  
Bin Chen
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Monte Carlo ◽  
Monte Carlo Method ◽  
Failure Modes ◽  
Underlying Mechanism ◽  
Cyclic Stretch ◽  
Cyclic Loads ◽  
Element Analysis ◽  
The Stability

Cells are subjected to cyclic loads under physiological conditions, which regulate cellular structures and functions. Recently, it was demonstrated that cells on substrates reoriented nearly perpendicular to the stretch direction in response to uni-axial cyclic stretches. Though various theories were proposed to explain this observation, the underlying mechanism, especially at the molecular level, is still elusive. To provide insights into this intriguing observation, we employ a coupled finite element analysis (FEA) and Monte Carlo method to investigate the stability of a cluster of slip bonds upon cyclic loads. Our simulation results indicate that the cluster can become unstable upon cyclic loads and there exist two characteristic failure modes: gradual sliding with a relatively long lifetime versus catastrophic failure with a relatively short lifetime. We also find that the lifetime of the bond cluster, in many cases, decreases with increasing stretch amplitude and also decreases with increasing cyclic frequency, which appears to saturate at high cyclic frequencies. These results are consistent with the experimental reports. This work suggests the possible role of slip bonds in cellular reorientation upon cyclic stretch.

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