List of Journal Publications
2004
11.
Simone, A.
Partition of unity-based discontinuous elements for interface phenomena: Computational issues Journal Article
In: COMMUNICATIONS IN NUMERICAL METHODS IN ENGINEERING, vol. 20, no. 6, pp. 465–478, 2004.
Abstract | BibTeX | Tags: Displacement discontinuity, Interface elements, Partition of unity | Links:
@article{Simone2004,
title = {Partition of unity-based discontinuous elements for interface phenomena: Computational issues},
author = {A. Simone},
doi = {10.1002/cnm.688},
year = {2004},
date = {2004-01-01},
journal = {COMMUNICATIONS IN NUMERICAL METHODS IN ENGINEERING},
volume = {20},
number = {6},
pages = {465–478},
abstract = {The performance of partition of unity‐based discontinuous elements was studied by means of a numerical study. In particular, it was shown that conventional interface elements and partition of unity‐based discontinuous elements share the same structure of the stiffness matrix governing interface behaviour and, under specific circumstances, the same shortcomings (i.e. oscillations in the traction profile). The effect of various integration schemes on the interface contribution was studied through the analysis of a linear‐elastic notched beam. Further, an eigenvalue analysis of the partition of unity‐based discontinuous element was conducted to gain more insight into its mechanical behaviour.},
keywords = {Displacement discontinuity, Interface elements, Partition of unity},
pubstate = {published},
tppubtype = {article}
}
The performance of partition of unity‐based discontinuous elements was studied by means of a numerical study. In particular, it was shown that conventional interface elements and partition of unity‐based discontinuous elements share the same structure of the stiffness matrix governing interface behaviour and, under specific circumstances, the same shortcomings (i.e. oscillations in the traction profile). The effect of various integration schemes on the interface contribution was studied through the analysis of a linear‐elastic notched beam. Further, an eigenvalue analysis of the partition of unity‐based discontinuous element was conducted to gain more insight into its mechanical behaviour.
10.
Simone, A., Askes, H., Peerlings, R. H. J., Sluys, L. J.
Interpolation requirements for implicit gradient-enhanced continuum damage models' Journal Article
In: COMMUNICATIONS IN NUMERICAL METHODS IN ENGINEERING, vol. 20, no. 2, pp. 163–165, 2004.
Abstract | BibTeX | Tags: Engineering (miscellaneous); Applied Mathematics; Computational Mechanics | Links:
@article{Simone2004a,
title = {Interpolation requirements for implicit gradient-enhanced continuum damage models'},
author = {A. Simone and H. Askes and R. H. J. Peerlings and L. J. Sluys},
doi = {10.1002/cnm.663},
year = {2004},
date = {2004-01-01},
journal = {COMMUNICATIONS IN NUMERICAL METHODS IN ENGINEERING},
volume = {20},
number = {2},
pages = {163–165},
abstract = {Corrigenda},
keywords = {Engineering (miscellaneous); Applied Mathematics; Computational Mechanics},
pubstate = {published},
tppubtype = {article}
}
Corrigenda
9.
Simone, A., Sluys, L. J.
The use of displacement discontinuities in a rate-dependent medium Journal Article
In: COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING, vol. 193, no. 27-29, pp. 3015–3033, 2004.
Abstract | BibTeX | Tags: Damage, Displacement discontinuities, Partition of unity, Plasticity, Rate dependence, Regularised continuum | Links:
@article{Simone2004b,
title = {The use of displacement discontinuities in a rate-dependent medium},
author = {A. Simone and L. J. Sluys},
doi = {10.1016/j.cma.2003.08.006},
year = {2004},
date = {2004-01-01},
journal = {COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING},
volume = {193},
number = {27-29},
pages = {3015–3033},
abstract = {This paper illustrates the use of displacement discontinuities in a rate-dependent elastoplastic-damage model. Rate-dependency is considered in the framework of Perzyna viscoplasticity. Displacement discontinuities are incorporated using the partition of unity property of finite-element shape functions. A combined continuous–discontinuous approach is proposed in which a discontinuity is only inserted after a certain amount of damage. Various examples illustrate the applicability of the combined approach to granular and quasi-brittle materials with and without fibre-reinforcement.},
keywords = {Damage, Displacement discontinuities, Partition of unity, Plasticity, Rate dependence, Regularised continuum},
pubstate = {published},
tppubtype = {article}
}
This paper illustrates the use of displacement discontinuities in a rate-dependent elastoplastic-damage model. Rate-dependency is considered in the framework of Perzyna viscoplasticity. Displacement discontinuities are incorporated using the partition of unity property of finite-element shape functions. A combined continuous–discontinuous approach is proposed in which a discontinuity is only inserted after a certain amount of damage. Various examples illustrate the applicability of the combined approach to granular and quasi-brittle materials with and without fibre-reinforcement.
8.
A., Simone, H., Askes, J., Sluys L.
Incorrect initiation and propagation of failure in non-local and gradient-enhanced media Journal Article
In: INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES, vol. 41, no. 2, pp. 351–363, 2004.
Abstract | BibTeX | Tags: Damage initiation, Damage propagation, Regularised media, Shear band | Links:
@article{Simone2004c,
title = {Incorrect initiation and propagation of failure in non-local and gradient-enhanced media},
author = {Simone A. and Askes H. and Sluys L. J.},
doi = {10.1016/j.ijsolstr.2003.09.020},
year = {2004},
date = {2004-01-01},
journal = {INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES},
volume = {41},
number = {2},
pages = {351–363},
publisher = {Elsevier Ltd},
abstract = {Damage initiation and propagation in a class of non-local and gradient-enhanced media is investigated. In this contribution it is shown how the use of a non-local dissipation-driving state variable leads to an incorrect failure characterisation in terms of damage initiation and propagation. Damage initiation is analysed in detail for a class of non-local damage models–formulated in an integral and a differential format–by means of analytical considerations and numerical investigations in a mode-I problem. A numerical study on damage propagation is also presented for a shear band formation problem.},
keywords = {Damage initiation, Damage propagation, Regularised media, Shear band},
pubstate = {published},
tppubtype = {article}
}
Damage initiation and propagation in a class of non-local and gradient-enhanced media is investigated. In this contribution it is shown how the use of a non-local dissipation-driving state variable leads to an incorrect failure characterisation in terms of damage initiation and propagation. Damage initiation is analysed in detail for a class of non-local damage models–formulated in an integral and a differential format–by means of analytical considerations and numerical investigations in a mode-I problem. A numerical study on damage propagation is also presented for a shear band formation problem.
7.
Nicola, L., der Giessen, Erik Van, Needleman, Alan
Relaxation of thermal stress by dislocation motion in passivated metal interconnects Journal Article
In: JOURNAL OF MATERIALS RESEARCH, vol. 19, no. 4, pp. 1216–1226, 2004.
Abstract | BibTeX | Tags: discrete dislocation plasticity, metal interconnects, Thin films | Links:
@article{Nicola2004,
title = {Relaxation of thermal stress by dislocation motion in passivated metal interconnects},
author = {L. Nicola and Erik Van der Giessen and Alan Needleman},
doi = {10.1557/JMR.2004.0158},
year = {2004},
date = {2004-01-01},
journal = {JOURNAL OF MATERIALS RESEARCH},
volume = {19},
number = {4},
pages = {1216–1226},
publisher = {Materials Research Society},
abstract = {The development and relaxation of stress in metal interconnects strained by their surroundings (substrate and passivation layers) is predicted by a discrete dislocation analysis. The model is based on a two-dimensional plane strain formulation, with deformation fully constrained in the line direction. Plastic deformation occurs by glide of edge dislocations on three slip systems in the single-crystal line. The substrate and passivation layers are treated as elastic materials and therefore impenetrable for the dislocations. Results of the simulations show the dependence of the stress evolution and of the effectiveness of plastic relaxation on the geometry of the line. The dependence of stress development on line aspect ratio, line size, slip plane orientation, pitch length, and passivation layer thickness are explored.},
keywords = {discrete dislocation plasticity, metal interconnects, Thin films},
pubstate = {published},
tppubtype = {article}
}
The development and relaxation of stress in metal interconnects strained by their surroundings (substrate and passivation layers) is predicted by a discrete dislocation analysis. The model is based on a two-dimensional plane strain formulation, with deformation fully constrained in the line direction. Plastic deformation occurs by glide of edge dislocations on three slip systems in the single-crystal line. The substrate and passivation layers are treated as elastic materials and therefore impenetrable for the dislocations. Results of the simulations show the dependence of the stress evolution and of the effectiveness of plastic relaxation on the geometry of the line. The dependence of stress development on line aspect ratio, line size, slip plane orientation, pitch length, and passivation layer thickness are explored.
2003
6.
J., Alfaiate, A., Simone, J., Sluys L.
Non-homogeneous displacement jumps in strong embedded discontinuities Journal Article
In: INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES, vol. 40, no. 21, pp. 5799–5817, 2003.
Abstract | BibTeX | Tags: Discrete cracking, Strong embedded discontinuity | Links:
@article{Alfaiate2003,
title = {Non-homogeneous displacement jumps in strong embedded discontinuities},
author = {Alfaiate J. and Simone A. and Sluys L. J.},
doi = {10.1016/S0020-7683(03)00372-X},
year = {2003},
date = {2003-01-01},
journal = {INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES},
volume = {40},
number = {21},
pages = {5799–5817},
publisher = {Elsevier Ltd},
abstract = {In this paper, strong discontinuities are embedded in finite elements to describe fracture in quasi-brittle materials. A new numerical formulation is introduced in which the displacement jumps do not need to be homogeneous within each finite element. Both the crack path and the displacement jumps are continuous across element boundaries. This formulation is compared with the discrete approach, in which interface elements are inserted to model the discontinuities, as well as with other embedded discontinuity approaches and with the partition of unity method. Numerical results have been obtained with relatively coarse meshes, which compare well with experimental results and with the results obtained from analyzes with interface elements.},
keywords = {Discrete cracking, Strong embedded discontinuity},
pubstate = {published},
tppubtype = {article}
}
In this paper, strong discontinuities are embedded in finite elements to describe fracture in quasi-brittle materials. A new numerical formulation is introduced in which the displacement jumps do not need to be homogeneous within each finite element. Both the crack path and the displacement jumps are continuous across element boundaries. This formulation is compared with the discrete approach, in which interface elements are inserted to model the discontinuities, as well as with other embedded discontinuity approaches and with the partition of unity method. Numerical results have been obtained with relatively coarse meshes, which compare well with experimental results and with the results obtained from analyzes with interface elements.
5.
Simone, A., Askes, H., Peerlings, R. H. J., Sluys, L. J.
Interpolation requirements for implicit gradient-enhanced continuum damage models Journal Article
In: COMMUNICATIONS IN NUMERICAL METHODS IN ENGINEERING, vol. 19, no. 7, pp. 563–572, 2003.
Abstract | BibTeX | Tags: Babuška-Brezzi condition, Coupled problems, Gradient-enhanced continuum models, Interpolation functions, Mixed methods, Stress oscillations | Links:
@article{Simone2003,
title = {Interpolation requirements for implicit gradient-enhanced continuum damage models},
author = {A. Simone and H. Askes and R. H. J. Peerlings and L. J. Sluys},
doi = {10.1002/cnm.597},
year = {2003},
date = {2003-01-01},
journal = {COMMUNICATIONS IN NUMERICAL METHODS IN ENGINEERING},
volume = {19},
number = {7},
pages = {563–572},
abstract = {Some properties of a gradient‐enhanced continuum damage model were discussed by means of a numerical and theoretical study. In particular, it is demonstrated that the discretization of this model does not belong to the class of mixed finite element formulations (although the model has the format of a general coupled problem). Hence, the Babuška–Brezzi condition does not apply to this type of models. Consequently, the use of linear interpolation functions for displacements as well for non‐local equivalent strains yields excellent performance in terms of rate of convergence and of convergence of the numerical procedure.},
keywords = {Babuška-Brezzi condition, Coupled problems, Gradient-enhanced continuum models, Interpolation functions, Mixed methods, Stress oscillations},
pubstate = {published},
tppubtype = {article}
}
Some properties of a gradient‐enhanced continuum damage model were discussed by means of a numerical and theoretical study. In particular, it is demonstrated that the discretization of this model does not belong to the class of mixed finite element formulations (although the model has the format of a general coupled problem). Hence, the Babuška–Brezzi condition does not apply to this type of models. Consequently, the use of linear interpolation functions for displacements as well for non‐local equivalent strains yields excellent performance in terms of rate of convergence and of convergence of the numerical procedure.
4.
Simone, A., Wells, G. N., Sluys, L. J.
From continuous to discontinuous failure in a gradient-enhanced continuum damage model Journal Article
In: COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING, vol. 192, no. 41-42, pp. 4581–4607, 2003.
Abstract | BibTeX | Tags: Damage, Discontinuities, Enriched finite-elements, Fracture, Gradient-enhanced continuum, Non-local continuum, Partition of unity | Links:
@article{Simone2003a,
title = {From continuous to discontinuous failure in a gradient-enhanced continuum damage model},
author = {A. Simone and G. N. Wells and L. J. Sluys},
doi = {10.1016/S0045-7825(03)00428-6},
year = {2003},
date = {2003-01-01},
journal = {COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING},
volume = {192},
number = {41-42},
pages = {4581–4607},
publisher = {Elsevier},
abstract = {A computational framework for the description of the combined continuous–discontinuous failure in a regularised strain-softening continuum is proposed. The continuum is regularised through the introduction of gradient terms into the constitutive equations. At the transition to discrete failure, the problem fields are enhanced through a discontinuous interpolation based on the partition of unity paradigm of finite-element shape functions. The inclusion of internal discontinuity surfaces, where boundary conditions are applied without modifications of the original finite-element mesh, avoids the unrealistic damage growth typical of this class of regularised continuum models. Combined models allow for the analysis of the entire failure process, from diffuse microcracking to localised macrocracks. The discretisation procedure is described in detail and numerical examples illustrate the performance of the combined continuous–discontinuous approach.},
keywords = {Damage, Discontinuities, Enriched finite-elements, Fracture, Gradient-enhanced continuum, Non-local continuum, Partition of unity},
pubstate = {published},
tppubtype = {article}
}
A computational framework for the description of the combined continuous–discontinuous failure in a regularised strain-softening continuum is proposed. The continuum is regularised through the introduction of gradient terms into the constitutive equations. At the transition to discrete failure, the problem fields are enhanced through a discontinuous interpolation based on the partition of unity paradigm of finite-element shape functions. The inclusion of internal discontinuity surfaces, where boundary conditions are applied without modifications of the original finite-element mesh, avoids the unrealistic damage growth typical of this class of regularised continuum models. Combined models allow for the analysis of the entire failure process, from diffuse microcracking to localised macrocracks. The discretisation procedure is described in detail and numerical examples illustrate the performance of the combined continuous–discontinuous approach.
3.
Nicola, L., der, Giessen Van, Needleman, E.
Discrete dislocation analysis of size effects in thin films Journal Article
In: JOURNAL OF APPLIED PHYSICS, vol. 93, no. 10, pp. 5920–5928, 2003.
Abstract | BibTeX | Tags: discrete dislocation plasticity, size effects, Thin films | Links:
@article{Nicola2003,
title = {Discrete dislocation analysis of size effects in thin films},
author = {L. Nicola and Giessen Van der and E. Needleman},
doi = {10.1063/1.1566471},
year = {2003},
date = {2003-01-01},
journal = {JOURNAL OF APPLIED PHYSICS},
volume = {93},
number = {10},
pages = {5920–5928},
abstract = {A discrete dislocation plasticity analysis of plastic deformation in metal thin films caused by thermal stress is carried out. The calculations use a two-dimensional plane-strain formulation with only edge dislocations. Single crystal films with a specified set of slip systems are considered. The film-substrate system is subjected to a prescribed temperature history and a boundary value problem is formulated and solved for the evolution of the stress field and for the evolution of the dislocations structure in the film. A hard boundary layer forms at the interface between the film and the substrate, which does not scale with the film thickness and thus gives rise to a size effect. It is found that a reduction in the rate of dislocation nucleation can occur abruptly, which gives rise to a two-stage hardening behavior.},
keywords = {discrete dislocation plasticity, size effects, Thin films},
pubstate = {published},
tppubtype = {article}
}
A discrete dislocation plasticity analysis of plastic deformation in metal thin films caused by thermal stress is carried out. The calculations use a two-dimensional plane-strain formulation with only edge dislocations. Single crystal films with a specified set of slip systems are considered. The film-substrate system is subjected to a prescribed temperature history and a boundary value problem is formulated and solved for the evolution of the stress field and for the evolution of the dislocations structure in the film. A hard boundary layer forms at the interface between the film and the substrate, which does not scale with the film thickness and thus gives rise to a size effect. It is found that a reduction in the rate of dislocation nucleation can occur abruptly, which gives rise to a two-stage hardening behavior.
2001
2.
Nicola, L., der, Giessen Van, And, Needleman
2D dislocation dynamics in thin metal layers Journal Article
In: MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, vol. 309-310, pp. 274–277, 2001.
Abstract | BibTeX | Tags: 2D dislocation dynamics, plastic deformation, Thin metal layers | Links:
@article{Nicola2001,
title = {2D dislocation dynamics in thin metal layers},
author = {L. Nicola and Giessen Van der and Needleman And},
doi = {10.1016/S0921-5093(00)01690-7},
year = {2001},
date = {2001-01-01},
journal = {MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING},
volume = {309-310},
pages = {274–277},
abstract = {The paper deals with a discrete dislocation dynamics study of plastic deformation in a thin film caused by thermal mismatch with its substrate. A unit cell analysis is carried out, with dislocations in the film being represented by line singularities in an isotropic linear elastic medium. Their mutual interactions as well as the interactions with the interface and the free surface are accounted for by means of a coupled dislocation dynamics-finite element technique. The formulation includes a set of constitutive rules to model generation, glide, annihilation and pinning of dislocations at point obstacles. The simulation tracks the evolution of the dislocation structure as thermal stress builds up as well as during relaxation under constant temperature, leading to dense dislocation distributions near the interface and a dislocation-free zone along the stress-free surface of the film.},
keywords = {2D dislocation dynamics, plastic deformation, Thin metal layers},
pubstate = {published},
tppubtype = {article}
}
The paper deals with a discrete dislocation dynamics study of plastic deformation in a thin film caused by thermal mismatch with its substrate. A unit cell analysis is carried out, with dislocations in the film being represented by line singularities in an isotropic linear elastic medium. Their mutual interactions as well as the interactions with the interface and the free surface are accounted for by means of a coupled dislocation dynamics-finite element technique. The formulation includes a set of constitutive rules to model generation, glide, annihilation and pinning of dislocations at point obstacles. The simulation tracks the evolution of the dislocation structure as thermal stress builds up as well as during relaxation under constant temperature, leading to dense dislocation distributions near the interface and a dislocation-free zone along the stress-free surface of the film.
2000
1.
Berthold, A., Nicola, L., Sarro, P. M., And, Vellekoop, M., J.
Glass-to-glass anodic bonding with standard IC technology thin films as intermediate layers Journal Article
In: SENSORS AND ACTUATORS. A, PHYSICAL, vol. 82, no. 1, pp. 224–228, 2000.
Abstract | BibTeX | Tags: Anodic bonding, Glass bonding, Low temperature | Links:
@article{Berthold2000,
title = {Glass-to-glass anodic bonding with standard IC technology thin films as intermediate layers},
author = {A. Berthold and L. Nicola and P. M. Sarro and Vellekoop And and J. M.},
doi = {10.1016/S0924-4247(99)00376-3},
year = {2000},
date = {2000-01-01},
journal = {SENSORS AND ACTUATORS. A, PHYSICAL},
volume = {82},
number = {1},
pages = {224–228},
publisher = {Elsevier Sequoia SA},
abstract = {Glass-to-glass wafer bonding has recently attracted considerable interest. Especially for liquid manipulation applications and on-chip chemical analysis systems, all-glass sealed channels with integrated metal electrodes are very attractive. In this paper, we present a novel anodic bonding process in which the temperature does not exceed 400°C. This is a crucial requirement if metal patterns are present on the wafers. A number of thin film materials available in most conventional IC processes deposited on the glass wafers have been tested as intermediate bonding layers. Successful bonding is obtained for various layer combinations and an explanation of the bonding mechanism is given.},
keywords = {Anodic bonding, Glass bonding, Low temperature},
pubstate = {published},
tppubtype = {article}
}
Glass-to-glass wafer bonding has recently attracted considerable interest. Especially for liquid manipulation applications and on-chip chemical analysis systems, all-glass sealed channels with integrated metal electrodes are very attractive. In this paper, we present a novel anodic bonding process in which the temperature does not exceed 400°C. This is a crucial requirement if metal patterns are present on the wafers. A number of thin film materials available in most conventional IC processes deposited on the glass wafers have been tested as intermediate bonding layers. Successful bonding is obtained for various layer combinations and an explanation of the bonding mechanism is given.
