Imperial College London

DrYilunXu

Faculty of EngineeringDepartment of Materials

Research Associate
 
 
 
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Contact

 

yilun.xu Website CV

 
 
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Location

 

B301Bessemer BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
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5 results found

Prastiti NG, Xu Y, Balint DS, Dunne FPEet al., 2019, Discrete dislocation, crystal plasticity and experimental studies of fatigue crack nucleation in single-crystal nickel, International Journal of Plasticity, Pages: 102615-102615, ISSN: 0749-6419

Dislocation configurational energy and stored energy densities are determined in discrete dislocation and crystal plasticity modelling respectively and assessed with respect to experiments on single crystal nickel fatigue crack nucleation. Direct comparisons between the three techniques are provided for two crystal orientation fatigue tests. These provide confirmation that both quantities correctly identify the sites of fatigue crack nucleation and that stored energy density is a reasonable approximation to the more rigorous dislocation configurational energy. GND density is shown to be important in locating crack nucleation sites because of its role in the local configurational energy density.

Journal article

Xu Y, Balint D, Dini D, 2019, A new hardness formula incorporating the effect of source density on indentation response: a discrete dislocation plasticity analysis, Surface and Coatings Technology, Vol: 374, Pages: 763-773, ISSN: 0257-8972

Planar discrete dislocation plasticity (DDP) calculations that simulate thin single crystal films bonded to a rigid substrate indented by a rigid wedge are performed for different values of film thickness and dislocation source density. As in prior studies, an indentation size effect (ISE) is observed when indentation depth is sufficiently small relative to the film thickness. Thedependence of the ISE on dislocation source density is quantified in this study, and a modified form of the scaling law for the dependence of hardness on indentation depth, first derived by Nix and Gao, is proposed, which is valid over the entire range of indentation depths and correlates the length scale parameter with the average dislocation source spacing. Nanoindentation experimental data from the literature are fitted using this formula, which further verifies the proposed scaling of indentation pressure on dislocation source density.

Journal article

Xu Y, Balint DB, Dini DD, 2016, A method of coupling discrete dislocation plasticity to the crystal plasticity finite element method, Modelling and Simulation in Materials Science and Engineering, Vol: 24, ISSN: 1361-651X

A method of concurrent coupling of planar discrete dislocation plasticity (DDP) and a crystal plasticityfinite element (CPFE) method was devised for simulating plastic deformation in large polycrystals withdiscrete dislocation resolution in a single grain or cluster of grains for computational efficiency;computation time using the coupling method can be reduced by an order of magnitude compared toDDP. The method is based on an iterative scheme initiated by a sub-model calculation, which ensuresdisplacement and traction compatibility at all nodes at the interface between the DDP and CPFEdomains. The proposed coupling approach is demonstrated using two plane strain problems: (i)uniaxial tension of a bi-crystal film and (ii) indentation of a thin film on a substrate. The latter was alsoused to demonstrate that the rigid substrate assumption used in earlier discrete dislocation plasticitystudies is inadequate for indentation depths that are large compared to the film thickness, i.e. theeffect of the plastic substrate modelled using CPFE becomes important. The coupling method can beused to study a wider range of indentation depths than previously possible using DDP alone, withoutsacrificing the indentation size effect regime captured by DDP. The method is general and can beapplied to any problem where finer resolution of dislocation mediated plasticity is required to studythe mechanical response of polycrystalline materials, e.g. to capture size effects locally within a largerelastic/plastic boundary value problem.

Journal article

Xu Y, Balint DS, Dini D, 2013, Multi-scale modeling of indentation and contact fatigue: A coupled CPFE/DD approach, Pages: 3416-3419

Conference paper

Wang CE, Cui DL, Yan ZY, Xu YLet al., 2011, Finite element triangle mesh generation in planar area, Jisuanji Jicheng Zhizao Xitong/Computer Integrated Manufacturing Systems, CIMS, Vol: 17, Pages: 256-260, ISSN: 1006-5911

To improve efficiency and quality of finite element method in complicated assembly design, based on studies of several current Computer Aided Engineering (CAE) platforms, a triangle mesh generation system was established. In this system, isomeric mesh data from heterogeneous Ansys and Patran platform could be imported. Size control methods of mesh element were implemented from several aspects to generate size field information. Hybrid application of Advancing Front Technique (AFT) /Delauany/mapping algorithms for multi-area problem was realized. This system was applied in coupled thermo-solid analysis on axisymmetric components of aero-engine. Application results showed that the proposed method was effective.

Journal article

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