Dataset Information

Evolution of Welding Residual Stresses within Cladding and Substrate during Electroslag Strip Cladding.

ABSTRACT: Hydrogenation reactors are important oil-refining equipment that operate in high-temperature and high-pressure hydrogen environments and are commonly composed of 2.25Cr-1Mo-0.25V steel. For a hydrogenation reactor with a plate-welding structure, the processes and effects of welding residual stress (WRS) are very complicated due to the complexity of the welding structure. These complex welding residual stress distributions affect the service life of the equipment. This study investigates the evolution of welding residual stress during weld-overlay cladding for hydrogenation reactors using the finite element method (FEM). A blind hole method is applied to verify the proposed model. Unlike the classical model, WRS distribution in a cladding/substrate system in this study was found to be divided into three regions: the cladding layer, the stress-affected layer (SAL), and the substrate in this study. The SAL is defined as region coupling affected by the stresses of the cladding layer and substrate at the same time. The evolution of residual stress in these three regions was thoroughly analyzed in three steps with respect to the plastic-strain state of the SAL. Residual stress was rapidly generated in Stage 1, reaching about -440 MPa compression stress in the SAL region at the end of this stage after 2.5 s. After cooling for 154 s, at the end of Stage 2, the WRS distribution was fundamentally shaped except for in the cladding layer. The interface between the cladding layer and substrate is the most heavily damaged region due to the severe stress gradient and drastic change in WRS during the welding process. The effects of substrate thickness and preheat temperature were evaluated. The final WRS in the cladding layer first increased with the increase in substrate thickness, and then started to decline when substrate thickness reached a large-enough value. WRS magnitudes in the substrate and SAL decreased with the increase in preheat temperature and substrate thickness. Compressive WRS in the cladding layer, on the other hand, increased with the increase in preheat temperature.

SUBMITTER: Qin M

PROVIDER: S-EPMC7560439 | biostudies-literature | 2020 Sep

REPOSITORIES: biostudies-literature

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Evolution of Welding Residual Stresses within Cladding and Substrate during Electroslag Strip Cladding.

Qin Mu M Cheng Guangxu G Li Qing Q Zhang Jianxiao J

Materials (Basel, Switzerland) 20200917 18

Hydrogenation reactors are important oil-refining equipment that operate in high-temperature and high-pressure hydrogen environments and are commonly composed of 2.25Cr-1Mo-0.25V steel. For a hydrogenation reactor with a plate-welding structure, the processes and effects of welding residual stress (WRS) are very complicated due to the complexity of the welding structure. These complex welding residual stress distributions affect the service life of the equipment. This study investigates the evol ...[more]

PMID: 32957447

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Project description:BackgroundStaphylococcus aureus is a major cause of healthcare associated mortality, but like many important bacterial pathogens, it is a common constituent of the normal human body flora. Around a third of healthy adults are carriers. Recent evidence suggests that evolution of S. aureus during nasal carriage may be associated with progression to invasive disease. However, a more detailed understanding of within-host evolution under natural conditions is required to appreciate the evolutionary and mechanistic reasons why commensal bacteria such as S. aureus cause disease. Therefore we examined in detail the evolutionary dynamics of normal, asymptomatic carriage. Sequencing a total of 131 genomes across 13 singly colonized hosts using the Illumina platform, we investigated diversity, selection, population dynamics and transmission during the short-term evolution of S. aureus.Principal findingsWe characterized the processes by which the raw material for evolution is generated: micro-mutation (point mutation and small insertions/deletions), macro-mutation (large insertions/deletions) and the loss or acquisition of mobile elements (plasmids and bacteriophages). Through an analysis of synonymous, non-synonymous and intergenic mutations we discovered a fitness landscape dominated by purifying selection, with rare examples of adaptive change in genes encoding surface-anchored proteins and an enterotoxin. We found evidence for dramatic, hundred-fold fluctuations in the size of the within-host population over time, which we related to the cycle of colonization and clearance. Using a newly-developed population genetics approach to detect recent transmission among hosts, we revealed evidence for recent transmission between some of our subjects, including a husband and wife both carrying populations of methicillin-resistant S. aureus (MRSA).SignificanceThis investigation begins to paint a picture of the within-host evolution of an important bacterial pathogen during its prevailing natural state, asymptomatic carriage. These results also have wider significance as a benchmark for future systematic studies of evolution during invasive S. aureus disease.

Dataset Information

Evolution of Welding Residual Stresses within Cladding and Substrate during Electroslag Strip Cladding.

Publications

Evolution of Welding Residual Stresses within Cladding and Substrate during Electroslag Strip Cladding.

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