Wyniki wyszukiwania - BazTech

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Numerical analysis of stress intensity factor and T-stress in pipeline of steel P264GH submitted to loading conditions

Moustabchir H., Arbaoui J., Zitouni A., Hariri S., Dmytrakh I.

Journal of Theoretical and Applied Mechanics

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2015

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Vol. 53 nr 3

665--672

EN

Stress singularities occur at crack tips, corners and material interfaces. The stress intensity factors and T-stresses are coefficients of structural components where the active stress singular and first regular stress terms, respectively, are denoted by William’s eigen function expansion series. A finite element analysis by CASTEM 2000 have been undertaken in order to determine the evolution of the T-stress and stress intensity factor terms in mode I for an arc of pipeline specimens with an external surface crack. A stress difference method described by Moustabchir et al. (2012) are adapted and, in the following step, the volumetric method is then embedded to compute the SIFs and T-stress near the crack tip. Different crack geometries combined with different length-to-thickness ratios are examined for the T-stress and stress-intensity factor. The revisited stress difference method employed here shows to be an accurate and robust scheme for evaluating the T-stress/SIFs in an arc of the pipeline.

2

Influence of corrosion environments on materials and strength of structures:new approaches and practical applications.

Dmytrakh I.

Prace Naukowe Instytutu Materiałoznawstwa i Mechaniki Technicznej Politechniki Wrocławskiej. Konferencje

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2007

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Vol. 65, nr 11

13-35

EN

The presented lecture highlights the mechanical, physical and corrosion aspects of the environmentally assisted fracture of structural metallic materials. The methods and testing equipment for corrosion crack growth studies and electrochemical measurements within cracks are described. The relationship between electrochemical state and stress-strain state of pre-fracture zone was derived on the base of received experimental data for the number systems "material-environment". The new method for determining of corrosion fatigue crack growth rate diagrams is presented with taken into account an electrochemical situation in the crack tip. It has been proven that such diagrams reflect the extreme influence of the environment factor on material corrosion fatigue fracture processes and may be recommended as the base for a remaining lifetime calculation of the structure elements that are exploited under environmental conditions. The engineering applications of presented approaches and methods for expert assessment of technical state of heat-and-power engineering pipelines are considered and the examples of calculations of residual life of some structural elements are given with taken into account of the actual data of metal properties and operating conditions of equipment.

3

Corrosion Fracture Mechanics of Metallic Materials: Basic Conceptions, Achievement and Prospective

Panasyuk V., Dmytrakh I.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2005

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z. 79

223-242

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Corrosion fatigue crack growth emanating from notches: electrochemistry and mechanical aspects

Panasyuk V., Dmytrakh I.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2001

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z. 67

261-276

EN

Corrosion fatigue emanating from semicircular notches is considered. The studies are focused on the relationship between stress field and electrochemistry in notches with the aim of understanding and prediction of the corrosion fatigue crack nucleation and growth behaviour from notch surface. It has been done for typical corrosive active system "low strength carbon steel - 3% NaCl solution", where the electrochemical metal dissolution plays a dominant role. The semicircular notch is considered both as stress concentrator and as local corrosion minicell. The early stages of corrosion fatigue at the notch bottom were determined and the existence of some critical crack density g* that causes an intensive crack coalescence and macrocrack creation has been shown. An expression predicting the formation on notch surface the characteristic density of corrosion fatigue cracks is derived as function of the synergistic action of cyclic stress and the corrosion process.