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Your search keyword '"Cocks, Alan"' showing total 153 results
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153 results on '"Cocks, Alan"'

48. Multi-scale modelling of creep cavity nucleation and growth in polycrystalline Type 316 stainless steel.

Author

Petkov, Markian P., Elmukashfi, Elsiddig, and Cocks, Alan C.F.

Subjects
DISCONTINUOUS precipitation, MULTISCALE modeling, STAINLESS steel, STRAIN rate, CAVITATION erosion, CAVITATION, NUCLEATION
Abstract

A common creep damage mode in Type 316 stainless steel under high-temperature power plant conditions is intergranular cavitation. A review of the literature has confirmed that cavitation in Type 316 is controlled by nucleation, which is not fully understood. In order to provide further insights into the physics of this process, existing strain-based empirical and stress-based (classical nucleation theory) nucleation models are modified in this study by considering experimentally-observed features of cavity nucleation in Type 316. The models are employed locally within a newly-developed crystal plasticity finite element (CPFE)-interface element framework. Modelling results suggest that the strain-based model as a function of local inelastic strain rate does not explain the physical nature of the nucleation process as observed experimentally. By contrast, the modified classical nucleation theory is able to capture features of the observed macroscopic failure response and the distribution of cavities in the microstructure. A number of missing features are identified in the mechanistic model, which need to be incorporated in future unified cavity nucleation theories. These findings highlight key aspects of the nucleation process, which need to be examined experimentally. [ABSTRACT FROM AUTHOR]

Published
2022
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50. Type IV creep crack initiation and propagation in mod.9Cr-1Mo steel welds.

Author

Honda, Takashi, Fukahori, Takuya, Tokiyoshi, Takumi, Igari, Toshihide, Tominaga, Kimihiko, and Cocks, Alan C. F.

Subjects
STEEL welding, CRACK propagation (Fracture mechanics), AXIAL loads, WELDED joints, CREEP (Materials), WELDING
Abstract

The ratio of crack initiation and crack propagation life is important from the viewpoint of residual life prediction of mod. 9Cr-1Mo steel welds under Type IV creep damage. Both the creep void density distribution and the failure process with crack initiation/propagation/final failure are predicted for three types of welds in pipes and nozzles, which are compared with experimental results at 650°C. The ratio of crack initiation and final failure life depends on weld type and loading conditions; the ratio is about 0.95 in the cases where redistribution of stress occurs only in the thickness; the ratio is 0.59 ~ 0.65 in the cases where redistribution of stress occurs in both the thickness and circumferential directions of the pipe. Influence of stress ratio (axial vs. circumferential stress) is also predicted for circumferential welds subject to internal pressure/axial load and is compared with experimental results at 650°C. [ABSTRACT FROM AUTHOR]

Published
2022
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