Fatigue aspects of an evaluation of the operational safety of components working in creep conditions

• Autorzy: Okrajni J.
• Języki publikacji: EN

Abstrakty

EN

Purpose: The main purpose is the method of the description of the thermo-mechanical fatigue process of power plant components working under mechanical and thermal loading. The work focuses on the chosen component strain-stress characteristics and their strength. The paper discusses the issue of modelling the heating and cooling processes of components in a power plants in the start-up and shut-down conditions of a boiler. Design/methodology/approach: The FEM modelling has been used to describe the local stress-strain behaviour of the chosen component. Findings: The calculations of stress distribution on the chosen component surface show that the internal pressure induces considerably smaller values of stresses and strains in comparison with the same stresses specified for thermal loads. However, it should be noted that the impact of temperature gradients and thermal stresses is usually short-lived, therefore, its influence on creep processes is less significant in comparison to pressure load. Material fatigue is mainly the effect of thermal stresses. Thus, thermal impacts are responsible for cracks initiation and growth in areas of the greatest intensity of damage accumulation. Research limitations/implications: The presented analysis is the part of the complex investigation method which main purpose is increasing the accuracy of the TMF process description and thermo-mechanical life assessment. The possibility of applying the fatigue durability criteria currently assumed in standards still requires justification and confirmation in laboratory and industrial conditions to be closer to the real components behaviour. In such situation the industrial investigations curried out in the work give the model approach and data for the comparison the real behaviour with the predictions. Practical implications: The method of stress-strain behaviour analysis used in the paper could be useful in the practical cases when the real components mechanical behaviour would be analysed. Originality/value: The main value of this paper is the own method of the mechanical behaviour analysis of the power plant component. This method includes the temperature fields analysis taking into account the boundary conditions based on the operation parameter data and the thermoplastic material model. The material stress-strain behaviour has been treated as the local phenomenon, that could be modelled by FEM.

Słowa kluczowe

EN

applied mechanics; numerical techniques; fatigue; computational mechanics

• Wydawca: International OCSCO World Press
• Czasopismo: Journal of Achievements in Materials and Manufacturing Engineering
• Rocznik: 2011
• Tom: Vol. 45, nr 1
• Strony: 51--58
• Opis fizyczny: Bibliogr. 27 poz., rys.

Twórcy

autor

Okrajni J.

• Department of Materials Technology, Silesian University of Technology, ul. Krasińskiego 8, 41-403 Katowice, Poland

Bibliografia

• [1] P. Fontaine, J-F. Golopin, HRSG Optimization for cycling duty based on Euro Norm EN 12952-3, ETD Conference on Cyclic Operation of Power Plant, London, 2007.
• [2] Standards EN 12952, EN 12952-3:2001 (E), EN 129524:2000.
• [3] J. Okrajni, W. Essler, Computer models of steam pipeline components in the evaluation of their local strength, Journal of Achievements in Materials and Manufacturing Engineering 39/1 (2010) 71-78.
• [4] BS 7910, Guide on methods for assessing the acceptability of flows in structures (replacing PD 6493 and PD 6539), British Standards Institution, London, 1994.
• [5] Design and construction rules for mechanical components of FBR nuclear islands, RCC-MR, Appendix A16, AFCEN, Paris, 1995.
• [6] S. Webster, A. Bannister, Structural Integrity Assessment Procedure for Europe - of the SINTAP programme overview, Engineering Fracture Mechanics 67/6 (2000) 481-514.
• [7] Project European Thematic Network FITNET FFS-GIRT-CT-2001-05071.
• [8] A. Neimitz, I. Dzioba, M. Graba, J. Okrajni, The assessment of the strength and safety of the operation high temperature components containing crack. Kielce University of Technology Publishing House, Kielce, 2008.
• [9] A. Neimitz, Procedures of the strength assessment of structural components containing cracks, Kielce University of Technology Publishing House, Kielce, 2004 .
• [10] Nuclear Electric Ltd, Assessment Procedure for the High Temperature Response of Structure. Proc, R5/2, UK, 1997.
• [11] G.A. Webster, R.A. Ainsworth, High Temperature Component Life Assessment, Chapman & Hall, London 1994.
• [12] Z. Orłoś, Thermal stresses, PWN, Warsaw, 1991 (in Polish).
• [13] K. Mutwil, M. Cieśla, Factors determining the durability of steam superheater chambers, Power Engineering 14 (2007) 81-84 (in Polish).
• [14] A. Hernas, J. Dobrzański, Durability and damage of steam boilers and turbines, Silesian University of Technology Publishing House, Gliwice, 2003.
• [15] J. Bressers. L. Remy (eds.), Fatigue under thermal and mechanical loading, Kluwer Academic Publishers, Netherlands, 1996.
• [16] P. Hähner et al., Research and development into a European code-of-practice for strain-controlled thermo-mechanical fatigue testing, International Journal of Fatigue 30/2 (2008) 372-381.
• [17] H. Sehitoglu, Thermal and thermo-mechanical fatigue of structural alloys, Fatigue and Fracture, ASM Handbook 19 (1996) 527-556.
• [18] J. Okrajni, Thermo-mechanical conditions of power plant components, Journal of Achievements in Materials and Manufacturing Engineering 33/1 (2009) 53-61.
• [19] J. Okrajni, G. Junak. A. Marek, Modelling of the deformation process under thermo-mechanical fatigue conditions, International Journal of Fatigue 30/2 (2008) 324-329.
• [20] J. Okrajni, A. Marek, G. Junak, Description of the deformation process under thermo-mechanical fatigue, Journal of Achievements in Materials and Manufacturing Engineering 21/2 (2007) 15-24.
• [21] J. Okrajni, K. Mutwil, M. Cieśla, Steam pipelines’ effort and durability, Journal of Achievements in Materials and Manufacturing Engineering 22/ 2 (2007) 63-66.
• [22] D. Renowicz, A. Hernas, M. Cieśla, K. Mutwil, Degradation of the cast steel parts working in power plant pipelines, Proceeding of the 15th Scientific International Conference „Achievements in Mechanical and Materials Engineering” AMME’2006, Gliwice-Wisła, 2006, 219-222.
• [23] J. Okrajni, The durability of power plant pressure vessels from the point of view of obligatory standards, Power Engineering 18 (2008) 93-100 (in Polish).
• [24] D. Renowicz, M. Cieśla, Crack initiation in steels parts working in boilers and steam pipelines, Journal of Achievements in Materials and Manufacturing Engineering 21/2 (2007) 49-52.
• [25] J. Dobrzański, The classification method and the technical condition evaluation of the critical elements’ material of power boilers in creep service made from the 12Cr-1Mo-V, Journal of Materials Processing Technology 164-165 (2005) 785-794.
• [26] A. Neimitz, I. Dzioba, M. Graba, J. Okrajni, The assessment of the strength and safety of the operation high temperature components containing crack, Kielce University of Technology Publishing House, Kielce, 2008.
• [27] Project European Thematic Network FITNET FFS-GIRT-CT-2001-05071.