A Simplified Fatigue Assessment Method for ASME VIII-2

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Jun Shen ◽  
Mingwan Lu ◽  
Heng Peng ◽  
Yinghua Liu ◽  
Zhiwei Chen
Keyword(s):  
Evaluation Method ◽  
Failure Modes ◽  
Economic Cost ◽  
Material Design ◽  
Assessment Method ◽  
Element Analysis ◽  
Design Factor ◽  
Screening Criteria ◽  
Detailed Assessment ◽  
Fatigue Evaluation

Abstract Fatigue is one of the most common and important failure modes in pressure vessel. ASME VIII-2 provides three screening criterion and three detailed assessment method for fatigue failure. With the decrease of material design factor and the extension of fatigue curve to high cycle, the applicable scope of the three screening criteria become relatively smaller and the economic efficiency is also reduced. Meanwhile, the three fatigue evaluation methods given in ASME VIII-2 Code are all based on detailed numerical calculations (such as finite element analysis (FEA)). Both economic cost and requirements of technical personnel of engineers are higher. In this paper, a simplified fatigue evaluation method is proposed, which gives simple implementation procedures and relatively conservative fatigue evaluation results. Compared with the screening criteria method A, the main advantage is that the scope of its application is wider, that is: (1) the number of significant load cycle can be considered is extended from 1000 to 105; (2) there is no upper limit to the range of pressure fluctuation, which is 20% in method A. Compared with the screening criteria method B, the main advantage is that this method is much simpler and for most materials, design fatigue curves are not required during calculation and evaluation. Compared with the three detailed assessment methods given in ASME VIII-2, this method is very convenient and does not require detailed FEA. The method proposed in this paper can simplify the evaluation process of fatigue analysis in a certain range and provide a more cost-effective engineering assessment method.

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.

Development of Creep-Fatigue Evaluation Method for Modified 9Cr-1Mo Steel

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Shigeru Takaya ◽  
Yuji Nagae ◽  
Tai Asayama
Keyword(s):  
Evaluation Method ◽  
Time To Failure ◽  
Test Results ◽  
Design Factor ◽  
Design Procedures ◽  
Material Test ◽  
Creep Fatigue ◽  
Summation Rule ◽  
Fatigue Evaluation ◽  
Failure Life

This paper describes a creep–fatigue evaluation method for modified 9Cr-1Mo steel, which has been newly included in the 2012 edition of the Japan Society of Mechanical Engineers code for design and construction of fast reactors (JSME FRs code). In this method, creep and fatigue damages are evaluated on the basis of Miner's rule and the time fraction rule, respectively, and the linear summation rule is employed as the failure criterion. The conservativeness of this method without design factors was investigated using material test results, and it was shown that the time fraction approach can conservatively predict failure life if margins on the initial stress of relaxation and the stress relaxation rate are embedded. In addition, the conservatism of prediction tends to increase with time to failure. Comparison with the modified ductility exhaustion method, which is known to have good failure life predictability in material test results, shows that the time fraction approach predicts failure lives to be shorter in long-term strain hold conditions, where material test data are hardly obtained. These results confirm that the creep–fatigue evaluation method in the JSME FRs code has implicit conservatism in addition to explicit margins in the design procedures such as design factor.

Development of Fatigue Assessment Method Based on Flaw Tolerance Concept

2013 ◽  
Author(s):  
Seiji Asada ◽  
Takeda Shuhei ◽  
Taiji Hirasawa ◽  
Toshiyuki Saito ◽  
Itaru Saito ◽  
...  
Keyword(s):  
Power Generation ◽  
Nuclear Power ◽  
Evaluation Method ◽  
Assessment Method ◽  
Fatigue Assessment ◽  
Nondestructive Examination ◽  
Flaw Tolerance ◽  
Fatigue Evaluation ◽  
Tolerance Method ◽  
Operating Plant

The Japan Society of Mechanical Engineers (JSME) Committee on Power Generation Facility Codes recognizes the importance of fatigue evaluation methods based on the latest knowledge and is developing a fatigue evaluation method by flaw tolerance. The ASME B&PV Code Section XI has Non-mandatory Appendix L, “Operating Plant Fatigue Assessment” (hereinafter “App. L”), which provides a flaw tolerance method for fatigue evaluation when a cumulative usage factor (CUF) of a component is greater than 1.0. In order to develop a flaw tolerance method for the JSME Codes for nuclear power generation facilities, postulated initial flaws, capability of nondestructive examination, compatibility to rules and flaw tolerance codes are discussed.

Risk-Based Operations Assessment of a Multilayered Vessel Under Cyclic Loading Conditions

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
Mingxin Zhao ◽  
Richard Parkinson
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Cyclic Loading ◽  
Failure Modes ◽  
Loading Conditions ◽  
Element Analysis ◽  
Field Inspection ◽  
Operational Risks ◽  
Partial Probability ◽  
Fatigue Evaluation

Operational risks have been evaluated for a multilayered vessel through the fitness-for-service (FFS) assessment. The vessel has been in service for more than four decades and is subjected to cyclic mechanical and thermal loads during normal operations. Leakage has been found over the years by inspections, which led to safety concerns for continued operation. FFS assessment was used to evaluate the condition of the vessel to determine if the vessel was fit for continued operation and the associated risks for a catastrophic type failure or burst of all layers of the vessel. Finite element analysis and fatigue evaluation, with associated partial probability, were conducted for the assessment. The operational risks were evaluated on the combined basis of FFS assessment results, failure modes, and field inspection findings. It was concluded that, despite of the problems found during inspections, risks for the catastrophic type failure of the multilayered vessel are very low and continued operation with appropriate monitoring and maintenance is recommended.

Experimental Demonstration of Failure Modes on Bellows Structures Subject to Internal Pressure

2017 ◽  
Author(s):  
Masanori Ando ◽  
Hiroki Yada ◽  
Kazuyuki Tsukimori ◽  
Masakazu Ichimiya ◽  
Yoshinari Anoda
Keyword(s):  
Internal Pressure ◽  
Evaluation Method ◽  
Failure Modes ◽  
Difficult Problem ◽  
Maximum Pressure ◽  
Test Results ◽  
Element Analysis ◽  
Complex Deformation ◽  
Explicit Analysis ◽  
Pressure Failure

In this study, in order to develop the evaluation method of the pressure toughness of bellows structures under the beyond design base event, the pressure failure tests and finite element analysis (FEA) of the bellows structures subjected to internal pressure were performed. Since the several tests and FEA results were reported previously by current authors, the additional tests were performed by the specimen simulating the real setting situation in the actual plant and for demonstrating the plain failure modes. Test specimens consist of the single and double ply bellows made of SUS304 were used. Total five specimens were tested, and one specimen was attached the guard pipe around the bellows to simulate the actual situation in the plant to confirm the effect of the neighbor structures to the ultimate toughness. The maximum pressure obtained in all tests were over 10 times larger than the estimated results of limiting design pressure based on in-plain instability by the EJMA standards; although the test specimens were pressurized exceed the pressure of buckling deformation. Because it is very difficult problem to simulate the inversion of the convolution accompanied convolutions contact for FEA with implicit method, FEA with simplified technique and explicit analysis were performed to simulating the complex deformation of the test specimen, and then these results were estimated in some procedures to compare with the test results. Three failure modes identified in the tests, however, the complex deformation behavior make it difficult to simulate by ordinary FEA procedure and to estimate the ultimate toughness of the bellows structures under the internal pressure. Therefore several kinds of idea for evaluating the ultimate toughness of the bellows structures were execute and suggested.

Risk-Based Operations Assessment of a Multilayered Vessel Under Cyclic Loading Conditions

2012 ◽  
Author(s):  
Mingxin Zhao ◽  
Richard Parkinson
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Cyclic Loading ◽  
Failure Modes ◽  
Loading Conditions ◽  
Element Analysis ◽  
Field Inspection ◽  
Operational Risks ◽  
Partial Probability ◽  
Fatigue Evaluation

Operational risks have been evaluated for a multilayered vessel through the fitness-for-service (FFS) assessment. The vessel has been in service for more than four decades and is subjected to cyclic mechanical and thermal loads during normal operations. Leakage has been found over the years by inspections, which led to safety concerns for continued operation. FFS assessment was used to evaluate the condition of the vessel to determine if the vessel was fit for continued operation and the associated risks for a catastrophic type failure or burst of all layers of the vessel. Finite element analysis and fatigue evaluation, with associated partial probability, were conducted for the assessment per API 579. The operational risks were evaluated on the combined basis of FFS assessment results, failure modes, and field inspection findings. It was concluded that, despite of the problems found during inspections, risks for the catastrophic type failure of the multilayered vessel are very low and continued operation with appropriate monitoring and maintenance is recommended.

Experimental Study on the Deformation and Failure of the Bellows Structure Beyond the Designed Internal Pressure

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
Masanori Ando ◽  
Hiroki Yada ◽  
Kazuyuki Tsukimori ◽  
Masakazu Ichimiya ◽  
Yoshinari Anoda
Keyword(s):  
Internal Pressure ◽  
Evaluation Method ◽  
Failure Modes ◽  
Ductile Failure ◽  
The Other ◽  
Element Analysis ◽  
Complex Deformation ◽  
Pressurized Water ◽  
Deformation And Failure ◽  
Other Hand

Bellows structure is used to absorb the thermal expansion maintaining the boundary of the inside to outside, and it is applied to constitute the containment vessel (CV) boundary of the nuclear power plant. In this study, in order to develop the evaluation method of the ultimate strength of the bellows structure subject to internal pressure beyond the specified limit, the failure test and finite element analysis (FEA) of the bellows structure were performed. Several types of the bellows structure made of SUS304 were tested using pressurized water. The failure modes were demonstrated through the test of five and six specimens with six and five convolutions, respectively. Water leakage was caused by contact of the expanded convolution and the neighbor structure in the specimens with the shipping rod mounts. On the other hand, local failure as leakage in the deformation concentrated location and ductile failure as burst in the expanded convolution were observed in the specimen without shipping rod mounts. The maximum pressures in the test observed local and ductile failure were over ten times larger than the estimated values of the limited design pressure for in-plane instability by the EJMA standard. To simulate the buckling and deformation behavior during the test, the implicit and explicit FEA were performed. Because the inversion of the convolution accompanied by convolution contact observed in the test was too difficult a problem for implicit analysis, the maximum pressures in the step of solution converged were compared to the maximum pressures in the tests. On the other hand, explicit analysis enabled to simulate the complex deformation during the test, and the results were evaluated considering ductile failure to compare the test results.

Research on Oil Depot Safety Evaluation Based on Dow Chemical Fire and Explosion Index Assessment Method

2013 ◽  
Vol 748 ◽  
pp. 1256-1261
Author(s):  
Shou Hui He ◽  
Han Hua Zhu ◽  
Shi Dong Fan ◽  
Quan Wen
Keyword(s):  
Production Management ◽  
Evaluation Method ◽  
Risk Index ◽  
Safety Evaluation ◽  
Assessment Method ◽  
Theoretical Ground ◽  
Potential Hazard ◽  
Process Unit ◽  
Safety Production ◽  
Fire And Explosion

At the present time, the Dow Chemical Fire and Explosion Index (F&EI) is a kind of risk index evaluation method that is comprehensively used in evaluating potential hazard, area of exposure, expected losses in case of fire and explosion, etc. As the research object to oil depot storage tank area, this article ultimately confirms establishing appropriate pattern of process unit as well as reasonable safety precautions compensating method, in order to insure the reasonableness of evaluating result, by means of selecting process unit, confirming material factor and compensating safety precautions, using F&EI method. This can provide the basis for theoretical ground in aspect of oil depot development and safety production management.

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