IMT Institutional Repository: No conditions. Results ordered -Date Deposited. 2024-05-18T03:24:00ZEPrintshttp://eprints.imtlucca.it/images/logowhite.pnghttp://eprints.imtlucca.it/2016-12-27T09:06:58Z2016-12-27T09:06:58Zhttp://eprints.imtlucca.it/id/eprint/3617This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/36172016-12-27T09:06:58ZMechanical properties of Graphene: Molecular dynamics simulations correlated to continuum based scaling lawsIn this paper, the combined effect of domain size, lattice orientation and crack length on the mechanical properties of Graphene, namely the yield strength and strain, are studied extensively based on molecular dynamics simulations. Numerical predictions are compared with the continuum-based laws of size effect and multifractal scaling. The yield strength is found to vary with the specimen size as ≈L^{−1/3}, which is in agreement with the multifractal scaling law, and with the inverse square of the initial crack length as ≈a^{-1/2}, according to the Griffith’s energy criterion for fracture.Brahmanandam JavvajiPattabhi R. Budarapupattabhi.budarapu@imtlucca.itV. K. SutrakarD. Roy MahapatraMarco Paggimarco.paggi@imtlucca.itGoangseup ZiTimon Rabczuk2016-01-20T15:45:46Z2016-04-06T09:41:29Zhttp://eprints.imtlucca.it/id/eprint/3027This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/30272016-01-20T15:45:46ZCrack propagation in grapheneThe crack initiation and growth mechanisms in an 2D graphene lattice structure are studied based on molecular dynamics simulations. Crack growth in an initial edge crack model in the arm-chair and the zig-zag lattice configurations of graphene are considered. Influence of the time steps on the post yielding behaviour of graphene is studied. Based on the results, a time step of 0.1 fs is recommended for consistent and accurate simulation of crack propagation. Effect of temperature on the crack propagation in graphene is also studied, considering adiabatic and isothermal conditions. Total energy and stress fields are analyzed. A systematic study of the bond stretching and bond reorientation phenomena is performed, which shows that the crack propagates after significant bond elongation and rotation in graphene. Variation of the crack speed with the change in crack length is estimated.Pattabhi R. Budarapupattabhi.budarapu@imtlucca.itBrahmanandam JavvajiV. K. SutrakarD. Roy MahapatraGoangseup ZiTimon Rabczuk2015-03-27T10:54:35Z2016-03-18T10:43:50Zhttp://eprints.imtlucca.it/id/eprint/2650This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/26502015-03-27T10:54:35ZAn adaptive multiscale method for quasi-static crack growthThis paper proposes an adaptive atomistic- continuum numerical method for quasi-static crack growth. The phantom node method is used to model the crack in the continuum region and a molecular statics model is used near the crack tip. To ensure self-consistency in the bulk, a virtual atom cluster is used to model the material of the coarse scale. The coupling between the coarse scale and fine scale is realized through ghost atoms. The ghost atom positions are interpolated from the coarse scale solution and enforced as boundary conditions on the fine scale. The fine scale region is adaptively enlarged as the crack propagates and the region behind the crack tip is adaptively coarsened. An energy criterion is used to detect the crack tip location. The triangular lattice in the fine scale region corresponds to the lattice structure of the (111) plane of an FCC crystal. The Lennard-Jones potential is used to model the atom–atom interactions. The method is implemented in two dimensions. The results are compared to pure atomistic simulations; they show excellent agreement.Pattabhi R. Budarapupattabhi.budarapu@imtlucca.itRobert GracieStéphane P.A. BordasTimon Rabczuk2015-03-27T10:51:27Z2015-03-27T12:54:14Zhttp://eprints.imtlucca.it/id/eprint/2649This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/26492015-03-27T10:51:27ZEfficient coarse graining in multiscale modeling of fracture Abstract We propose a coarse-graining technique to reduce a given atomistic model into an equivalent coarse grained continuum model. The developed technique is tailored for problems involving complex crack patterns in 2D and 3D including crack branching and coalescence. Atoms on the crack surface are separated from the atoms not on the crack surface by employing the centro symmetry parameter. A rectangular grid is superimposed on the atomistic model. Atoms on the crack surface in each cell are used to estimate the equivalent coarse-scale crack surface of that particular cell. The crack path in the coarse model is produced by joining the approximated crack paths in each cell. The developed technique serves as a sound basis to study the crack propagation in multiscale methods for fracture. Pattabhi R. Budarapupattabhi.budarapu@imtlucca.itRobert GracieShih-Wei YangXiaoying ZhuangTimon Rabczuk2015-03-27T10:40:25Z2015-03-27T12:54:13Zhttp://eprints.imtlucca.it/id/eprint/2648This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/26482015-03-27T10:40:25ZA meshless adaptive multiscale method for fracture Abstract The paper presents a multiscale method for crack propagation. The coarse region is modelled by the differential reproducing kernel particle method. Fracture in the coarse scale region is modelled with the Phantom node method. A molecular statics approach is employed in the fine scale where crack propagation is modelled naturally by breaking of bonds. The triangular lattice corresponds to the lattice structure of the (111)plane of an {FCC} crystal in the fine scale region. The Lennard–Jones potential is used to model the atom–atom interactions. The coupling between the coarse scale and fine scale is realized through ghost atoms. The ghost atom positions are interpolated from the coarse scale solution and enforced as boundary conditions on the fine scale. The fine scale region is adaptively refined and coarsened as the crack propagates. The centro symmetry parameter is used to detect the crack tip location. The method is implemented in two dimensions. The results are compared to pure atomistic simulations and show excellent agreement. Shih-Wei YangPattabhi R. Budarapupattabhi.budarapu@imtlucca.itD. Roy MahapatraStéphane P.A. BordasGoangseup ZiTimon Rabczuk2015-03-27T10:18:27Z2015-03-27T12:54:13Zhttp://eprints.imtlucca.it/id/eprint/2643This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/26432015-03-27T10:18:27ZDirectionality of sound radiation from rectangular panels Abstract In this paper, the directionality of sound radiated from a rectangular panel, attached with masses/springs, set in a baffle, is studied. The attachment of masses/springs is done based on the receptance method. The receptance method is used to generate new mode shapes and natural frequencies of the coupled system, in terms of the old mode shapes and natural frequencies. The Rayleigh integral is then used to compute the sound field. The point mass/spring locations are arbitrary, but chosen with the objective of attaining a unique directionality. The excitation frequency to a large degree decides the sound field variations. However, the size of the masses and the locations of the masses/springs do influence the new mode shapes and hence the sound field. The problem is more complex when the number of masses/springs are increased and/or their values are made different. The technique of receptance method is demonstrated through a steel plate with attached point masses in the first example. In the second and third examples, the present method is applied to estimate the sound field from a composite panel with attached springs and masses, respectively. The layup sequence of the composite panel considered in the examples corresponds to the multifunctional structure battery material system, used in the micro air vehicle (MAV) (Thomas and Qidwai, 2005). The demonstrated receptance method does give a reasonable estimate of the new modes. Pattabhi R. Budarapupattabhi.budarapu@imtlucca.itT.S.S. NarayanaB. RammohanTimon Rabczuk