The two criteria diagram for creep crack initiation and its application to an ip-turbine

Ewald, J.; Sheng, Shilun

doi:10.1080/09603409.1998.11689618

Cited by 12 publications

(9 citation statements)

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“…This method [7,8] is only relevant to creep initiation and does not consider fatigue. Initiation is given if the point lies in the specific two criteria diagram, which depends on material or at least material group properties.…”

Section: Methods 3: Two Criteria Approachmentioning

confidence: 99%

“…It is usual for the codes to discount initiation when fatigue is present. The methods proposed have been successfully employed in different European assessment codes [1][2][3][4][5][6][7][8][9]. Since little universal validation exist to justify the choice of one method over another it is proposed to implement four models for crack initiation at this stage.…”

Section: Modelling Initiation -Stagementioning

confidence: 99%

“…More recent methods make life assessments based on the presence of defects in the component. For example the German flat bottom hole approach (FBH) considers crack detection and characterisation and the German two criteria method [7,8] regards initiation as the important factor in life assessment and does not deal with the crack growth regime. The more advanced codes dealing with defects over the range of creep and creep/fatigue interaction in initiation and growth of defects are the British Energy R5 [3], the French A16 [4,5] and BS-7910 [6] which have clear similarities in terms of methodology.…”

Section: Comparison Of the Present Codesmentioning

confidence: 99%

“…A number of defect assessment procedures (e.g. the British Energy R5 and the French A16, BS-7910 [1][2][3][4][5][6] and the German FBH and two-criteria method) [7][8] based on experimental and analytical models are available to assess crack initiation and growth and to determine the remaining useful life of such components.…”

Section: Introductionmentioning

confidence: 99%

“…It is clear that Europe is a leader in this developing field. Comparison of the existing European high temperature life assessment codes [1][2][3][4][5][6][7][8][9] lead to the conclusion that crack initiation is dealt with in different ways by the codes whereas creep and creep/fatigue crack growth are considered using the same models for analysis. At the same time whilst increasing sophistication is implemented in the analysis at the deterministic level insufficient emphasis is placed on the effects of the sensitivity and applicable bounds of the various parameters and material properties.…”

mentioning

confidence: 99%

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A unified European approach to high temperature defect assessment code and its incorporation in a knowledge base system

Nikbin¹

2001

International Journal of Pressure Vessels and Piping

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The background to high temperature defect assessment methodologies is investigated and similarities and differences are highlighted. It is clear that Europe is a leader in this developing field. Comparison of the existing European high temperature life assessment codes [1][2][3][4][5][6][7][8][9] lead to the conclusion that crack initiation is dealt with in different ways by the codes whereas creep and creep/fatigue crack growth are considered using the same models for analysis. At the same time whilst increasing sophistication is implemented in the analysis at the deterministic level insufficient emphasis is placed on the effects of the sensitivity and applicable bounds of the various parameters and material properties. The survey showed that for the same methods of analysis, widely different results can be derived depending on the choice of material properties, method for calculating K, reference stress σ ref and C*. The reason for the differences and the sensitivity to them is highlighted in this paper. The resulting conclusions suggest a methodology based on an expert system using both deterministic and probabilistic techniques would be beneficial. An outline of a defect assessment code structure, taking account of the major European codes, is presented which allows flexibility in terms of input of material data as well as the models used. The structure and the further development of the HIDA Knowledge Based System (KBS) is based on the concepts presented.Keyword: life assessment, creep, fatigue, power generation, knowledge based system Introduction Components in the power generation and petro-chemical industry operating at high temperatures are almost invariably submitted to static and/or combined loading. They may fail by crack growth, net section rupture or a combination of both. The present paper considers the defect assessment regime of failure. Figure 1 shows a schematic diagram of the range of crack initiation and growth bahaviour that a cracked component might show. A number of defect assessment procedures (e.g. the British Energy R5 and the French A16, BS-7910 [1-6] and the German FBH and two-criteria method) [7][8] based on experimental and analytical models are available to assess crack initiation and growth and to determine the remaining useful life of such components.

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Section: Methods 3: Two Criteria Approachmentioning

confidence: 99%