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696 results on '"Yan, Wentao"'

9. Defining urban network resilience: a review

Author

Ren Jie, Yan Wentao, Huang Yuting, and Li Zihao

Subjects
Urban Network Resilience, Conceptual Connotation, Research Methodologies, Structural Measurement Indicators, Optimization Strategies, Urbanization. City and country, HT361-384, Regional planning, HT390-395, Social Sciences
Abstract

Abstract As concerns over the security of intercity connections intensify, the concept of urban network resilience has increasingly captured the attention of researchers in related fields. This study aimed to clarify the varying interpretations of urban network resilience among scholars and to identify the advancements and potential gaps in existing literature. The results indicated that differences in perceptions of urban networks have led scholars to define urban network resilience from two distinct perspectives. This divergence influenced the focal points of research, as well as the methodologies, structural measurement indicators, and optimization strategies employed in these studies. We argued for the need to further explore the concept of urban network resilience by considering the nuances of different urban networks, refining methodologies for the identification, description, and measurement of resilience, and recognizing the interconnections among various types and scales of urban networks. This review can provide scholars and policymakers with comprehensive insights into urban resilience, thereby assisting them in making more informed and effective decisions.

Published
2024
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20. Mechanism of keyhole pore formation in metal additive manufacturing

Author

Wang, Lu, Zhang, Yanming, Chia, Hou Yi, and Yan, Wentao

Subjects
Condensed Matter - Materials Science
Abstract

Metal additive manufacturing has gained extensive attention from research institutes and companies to fabricate intricate parts and functionally graded materials. However, the porosity of the as-built part deteriorates the mechanical property and even hinders the further application of metal additive manufacturing. Particularly, the mechanisms of keyhole pores associated with the keyhole fluctuation are not fully understood. To reveal the mechanisms of the keyhole pores formation, we adopt a multiphysics thermal-fluid flow model incorporating heat transfer, liquid flow, metal evaporation, Marangoni effect, and Darcy's law to simulate the keyhole pore formation process, and the results are validated with the in-situ X-ray images. The simulation results present the instant bubble formation due to the keyhole instability and motion of the instant bubble when it pins on the solidification front. Moreover, the unevenly distributed recoil pressure on the keyhole surface is an important factor for keyhole collapse and penetration. Furthermore, comparing the keyhole pore formation under different laser scanning speeds shows that the keyhole pore is sensitive to the manufacturing parameters. The keyhole fluctuation features and energy absorptivity variation on the rear keyhole wall could be metrics to evaluate the likelihood of the keyhole pore formation. Additionally, the simulation under a low ambient pressure shows the feasibility of improving the keyhole stability to reduce and even avoid the formation of keyhole pores.

Published
2021

36. Crystal plasticity model of residual stress in additive manufacturing

Author

Grilli, Nicolò, Hu, Daijun, Yushu, Dewen, Chen, Fan, and Yan, Wentao

Subjects
Condensed Matter - Materials Science, 37M05, I.6.3
Abstract

Selective laser melting is receiving increasing interest as an additive manufacturing technique. Residual stresses induced by the large temperature gradients and inhomogeneous cooling process can favour the generation of cracks. In this work, a crystal plasticity finite element model is developed to simulate the formation of residual stresses and to understand the correlation between plastic deformation, grain orientation and residual stresses in the additive manufacturing process. The temperature profile and grain structure from thermal-fluid flow and grain growth simulations are implemented into the crystal plasticity model. An element elimination and reactivation method is proposed to model the melting and solidification and to reinitialise state variables, such as the plastic deformation, in the reactivated elements. The accuracy of this method is judged against previous method based on the stiffness degradation of liquid regions by comparing the plastic deformation as a function of time induced by thermal stresses. The method is used to investigate residual stresses parallel and perpendicular to the laser scan direction, and the correlation with the maximum Schmid factor of the grains along those directions. The magnitude of the residual stress can be predicted as a function of the depth, grain orientation and position with respect to the molten pool.

Published
2021

37. A multi-grid Cellular Automaton model for simulating dendrite growth and its application in additive manufacturing

Author

Yu, Yefeng, Li, Yang, Yan, Wentao, and Lin, Feng

Subjects
Condensed Matter - Materials Science
Abstract

The dendrite growth in casting and additive manufacturing is rather important and related to the formation of some defects. However, quantitatively simulating the growth of dendrites with arbitrary crystallographic orientations in 3-dimension(3D) is still very challenging. In the present work, we develop a multi-grid Cellular Automaton (CA) model for the dendrite growth. In this model, the interfacial area is further discretized into a child grid, on which the decentered octahedron growth algorithm is performed. The model is comprehensively and quantitatively verified by comparing with the prediction of analytical models and a published x-ray imaging observation result, proving that the model is quantitatively and morphologically accurate. After that, with the temperature gradient and cooling rate extracted from a finite-volume-method(FVM)-based thermal-fluid model, the model was applied in reproducing the dendrite growth process of nickel-based superalloy during a single-track electron beam melting process. The simulation results agree fairly well with the experimental observation, demonstrating the feasibility and effectiveness of using the model in additive manufacturing.

Published
2021

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