DSpace Collection:
http://hdl.handle.net/2117/6471
Mon, 01 Sep 2014 15:43:27 GMT2014-09-01T15:43:27Zwebmaster.bupc@upc.eduUniversitat Politècnica de Catalunya. Servei de Biblioteques i DocumentaciónoDeim-based PGD for parametric nonlinear model order reduction
http://hdl.handle.net/2117/22099
Title: Deim-based PGD for parametric nonlinear model order reduction
Authors: Aguado, José V.; Chinesta, Francisco; Leygue, Adrien; Cueto Prendes, Elias; Huerta, Antonio
Abstract: Anewtechniqueforefficientlysolvingparametricnonlinearreducedorder
modelsintheProperGeneralizedDecomposition(PGD)frameworkispresentedhere.
ThistechniqueisbasedontheDiscreteEmpiricalInterpolationMethod(DEIM)[1],and
thusthenonlineartermisinterpolatedusingthereducedbasisinsteadofbeingfully
evaluated.TheDEIMhasalreadybeendemonstratedtoprovidesatisfactoryresultsin
termsofcomputationalcomplexitydecreasewhencombinedwiththeProperOrthogonal
Decomposition(POD).However,inthePODcasethereducedbasisis
aposteriori
known
asitcomesfromseveralpre-computedsnapshots.Onthecontrary,thePGDisan
apriori
modelreductionmethod.ThismakestheDEIM-PGDcouplingratherdelicate,because
differentchoicesarepossibleasitisanalyzedinthisworkMon, 17 Mar 2014 12:13:01 GMThttp://hdl.handle.net/2117/220992014-03-17T12:13:01ZAguado, José V.; Chinesta, Francisco; Leygue, Adrien; Cueto Prendes, Elias; Huerta, AntonionoAnewtechniqueforefficientlysolvingparametricnonlinearreducedorder
modelsintheProperGeneralizedDecomposition(PGD)frameworkispresentedhere.
ThistechniqueisbasedontheDiscreteEmpiricalInterpolationMethod(DEIM)[1],and
thusthenonlineartermisinterpolatedusingthereducedbasisinsteadofbeingfully
evaluated.TheDEIMhasalreadybeendemonstratedtoprovidesatisfactoryresultsin
termsofcomputationalcomplexitydecreasewhencombinedwiththeProperOrthogonal
Decomposition(POD).However,inthePODcasethereducedbasisis
aposteriori
known
asitcomesfromseveralpre-computedsnapshots.Onthecontrary,thePGDisan
apriori
modelreductionmethod.ThismakestheDEIM-PGDcouplingratherdelicate,because
differentchoicesarepossibleasitisanalyzedinthisworkAdvanced harmonic techniques for solving the transient heat equation
http://hdl.handle.net/2117/22098
Title: Advanced harmonic techniques for solving the transient heat equation
Authors: Aguado, José Vicente; Huerta, Antonio; Chinesta, Francisco; Cueto Prendes, Elias; Leygue, Adrien
Abstract: Simulation-based management of processes has always been a
big challenge
because of the difficulty to merge two apparently opposed idea
s: the real time handling
demanded by the process, and the traditionally strong time c
onsumption linked to the sim-
ulation. However, very often processes are monitored or con
trolled by performing relatively
few measures on some specific points of the domain. Then, one s
trategy for accelerating
the simulation might be based on trying to compute the respon
se only where it is needed.
For this reason this work revisits a classical technique, th
e harmonic analysis, which is
combined with recent model reduction techniques giving pla
ce to an advanced harmonic
technique for solving linear parabolic equations and, in pa
rticular, the transient heat equa-
tion. Thanks to fact that Reciprocity principle applies in t
he frequency domain, the solu-
tion can be computed where it is of interest by performing an i
nexpensive postprocessing
of a pre-computed transfer function. This transfer functio
n, that must be valid for a suffi-
ciently large range of frequencies, is efficiently computed b
y using the Proper Generalized
Decomposition method.Mon, 17 Mar 2014 12:04:32 GMThttp://hdl.handle.net/2117/220982014-03-17T12:04:32ZAguado, José Vicente; Huerta, Antonio; Chinesta, Francisco; Cueto Prendes, Elias; Leygue, AdriennoSimulation-based management of processes has always been a
big challenge
because of the difficulty to merge two apparently opposed idea
s: the real time handling
demanded by the process, and the traditionally strong time c
onsumption linked to the sim-
ulation. However, very often processes are monitored or con
trolled by performing relatively
few measures on some specific points of the domain. Then, one s
trategy for accelerating
the simulation might be based on trying to compute the respon
se only where it is needed.
For this reason this work revisits a classical technique, th
e harmonic analysis, which is
combined with recent model reduction techniques giving pla
ce to an advanced harmonic
technique for solving linear parabolic equations and, in pa
rticular, the transient heat equa-
tion. Thanks to fact that Reciprocity principle applies in t
he frequency domain, the solu-
tion can be computed where it is of interest by performing an i
nexpensive postprocessing
of a pre-computed transfer function. This transfer functio
n, that must be valid for a suffi-
ciently large range of frequencies, is efficiently computed b
y using the Proper Generalized
Decomposition method.Error assessment for timeline-dependent quantities of interest in transient elastodynamics
http://hdl.handle.net/2117/22096
Title: Error assessment for timeline-dependent quantities of interest in transient elastodynamics
Authors: Verdugo, Francesc; Parés Mariné, Núria; Díez, Pedro
Abstract: This work presents a new approach to assess the error in speci c quantities
of interest in the framework of linear elastodynamics. In particular, a new type of quantities
of interest (referred as timeline-dependent quantities) is proposed. These quantities
are scalar time-dependent outputs of the transient solution which are better suited to
time-dependent problems than the standard scalar ones available in the literature. The
proposed methodology furnishes error estimates for both the standard scalar and the new
timeline-dependent quantities of interest. The key ingredient is the modal-based approximation
of the associated adjoint problems which allows e ciently computing and storing
the adjoint solution.Mon, 17 Mar 2014 11:45:00 GMThttp://hdl.handle.net/2117/220962014-03-17T11:45:00ZVerdugo, Francesc; Parés Mariné, Núria; Díez, PedronoThis work presents a new approach to assess the error in speci c quantities
of interest in the framework of linear elastodynamics. In particular, a new type of quantities
of interest (referred as timeline-dependent quantities) is proposed. These quantities
are scalar time-dependent outputs of the transient solution which are better suited to
time-dependent problems than the standard scalar ones available in the literature. The
proposed methodology furnishes error estimates for both the standard scalar and the new
timeline-dependent quantities of interest. The key ingredient is the modal-based approximation
of the associated adjoint problems which allows e ciently computing and storing
the adjoint solution.Numerical simulation of soil-water jet interaction with smoothed particle hydrodynamics
http://hdl.handle.net/2117/22095
Title: Numerical simulation of soil-water jet interaction with smoothed particle hydrodynamics
Authors: GUO, ZHIMING; Shao, Jiaru; Shen, Yongxing; Liu, Moubin
Abstract: Smoothed particle hydrodynamics (SPH) is a meshfree, Lagrangian particle method, which has been applied to different areas in sciences and industrial applications. In this work, SPH is used to simulate the soil-water jet interaction and erosion. In the simulation, water is modelled as a viscous fluid with weak compressibility and the soil is assumed to be an elastic-perfectly plastic material. The stress states of soil in the plastic flow regime follow the Drucker-Prager failure criterion. Both the shear and tensile criterions are used for the yield of soil particles if the yield point is reached and the total stress of the particle is scaled. Instead of computing particle pressure from an equation of state, the spherical stress is computed by dividing total stress into spherical stress and deviatoric stress. The interaction of coupling interfaces is strengthened by a penalty function to avoid unphysical penetration between particles from different materials. The obtained numerical results have shown that SPH could be a valuable method for the simulation of complex soil water interaction.Mon, 17 Mar 2014 11:38:12 GMThttp://hdl.handle.net/2117/220952014-03-17T11:38:12ZGUO, ZHIMING; Shao, Jiaru; Shen, Yongxing; Liu, MoubinnoElastic- perfectly plastic flow, Meshfree method, Smoothed particle hydrodynamics (SPH), Soil-water interaction, Water jetSmoothed particle hydrodynamics (SPH) is a meshfree, Lagrangian particle method, which has been applied to different areas in sciences and industrial applications. In this work, SPH is used to simulate the soil-water jet interaction and erosion. In the simulation, water is modelled as a viscous fluid with weak compressibility and the soil is assumed to be an elastic-perfectly plastic material. The stress states of soil in the plastic flow regime follow the Drucker-Prager failure criterion. Both the shear and tensile criterions are used for the yield of soil particles if the yield point is reached and the total stress of the particle is scaled. Instead of computing particle pressure from an equation of state, the spherical stress is computed by dividing total stress into spherical stress and deviatoric stress. The interaction of coupling interfaces is strengthened by a penalty function to avoid unphysical penetration between particles from different materials. The obtained numerical results have shown that SPH could be a valuable method for the simulation of complex soil water interaction.A finite element strategy coupling a gradient-enhanced damage model and cohesive cracks for quasi-brittle materials
http://hdl.handle.net/2117/22094
Title: A finite element strategy coupling a gradient-enhanced damage model and cohesive cracks for quasi-brittle materials
Authors: Tamayo Mas, Elena; Rodríguez Ferran, Antonio
Abstract: A new combined strategy to describe failure of quasi-brittle materials is presented thus allowing the complete description of the process, from initiation of damage to crack propagation. For the early stages of the process, and in order to overcome the well-known problems characterising local descriptions of damage (e.g. mesh-dependence), a gradient-enhanced model based on smoothed displacements is employed. In order to deal with material separation, this continuous description is coupled to a cohesive crack when damage parameter exceeds a critical value. Some difficulties may arise when dealing with the transition from regularised damage models to evolving cracks: crack initiation, crack-path direction, energetic equivalence... In this work, a discrete cohesive crack is introduced when the damage parameter exceeds a critical value. On the one hand, and to determine the crack-path direction, the medial axis of the already damaged profile is computed. That is, a geometric tool widely used in the computer graphics field is used here to track the crack surface. Since this technique is exclusively based on the shape of the regularised damage profile, no mesh sensitivity is observed when determining the crack direction. On the other hand, and to define the cohesive law, an energy balance is imposed thus ensuring that the fracture energy not yet dissipated in the damage zone is transferred to the crack.Mon, 17 Mar 2014 11:30:17 GMThttp://hdl.handle.net/2117/220942014-03-17T11:30:17ZTamayo Mas, Elena; Rodríguez Ferran, AntonionoCohesive cracks, Continuous-discontinuous strategy, Extended finite element method, Medial surface, Regularisation, Smoothed displacementsA new combined strategy to describe failure of quasi-brittle materials is presented thus allowing the complete description of the process, from initiation of damage to crack propagation. For the early stages of the process, and in order to overcome the well-known problems characterising local descriptions of damage (e.g. mesh-dependence), a gradient-enhanced model based on smoothed displacements is employed. In order to deal with material separation, this continuous description is coupled to a cohesive crack when damage parameter exceeds a critical value. Some difficulties may arise when dealing with the transition from regularised damage models to evolving cracks: crack initiation, crack-path direction, energetic equivalence... In this work, a discrete cohesive crack is introduced when the damage parameter exceeds a critical value. On the one hand, and to determine the crack-path direction, the medial axis of the already damaged profile is computed. That is, a geometric tool widely used in the computer graphics field is used here to track the crack surface. Since this technique is exclusively based on the shape of the regularised damage profile, no mesh sensitivity is observed when determining the crack direction. On the other hand, and to define the cohesive law, an energy balance is imposed thus ensuring that the fracture energy not yet dissipated in the damage zone is transferred to the crack.High-order mesh generation on CAD geometries
http://hdl.handle.net/2117/21005
Title: High-order mesh generation on CAD geometries
Authors: Gargallo Peiró, Abel; Roca Navarro, Xevi; Peraire Guitart, Jaume; Sarrate Ramos, Josep
Abstract: We present a technique to extend Jacobian-based distortion (quality) measures
for planar triangles to high-order isoparametric elements of any interpolation degree on CAD parameterized surfaces. The resulting distortion (quality) measures are expressed in terms of the parametric coordinates of the nodes. These extended distortion (quality) measures can be used to check the quality and validity of a high-order surface mesh. We also apply them to simultaneously smooth and untangle high-order surface meshes by minimizing
the extended distortion measure. The minimization is performed in terms of the
parametric coordinates of the nodes. Thus, the nodes always lie on the surface. Finally,
we include several examples to illustrate the application of the proposed technique.Mon, 16 Dec 2013 13:23:38 GMThttp://hdl.handle.net/2117/210052013-12-16T13:23:38ZGargallo Peiró, Abel; Roca Navarro, Xevi; Peraire Guitart, Jaume; Sarrate Ramos, Josepnohigh-order quality, high-order mesh generation, mesh optimization, curved elements, parameterized surfacesWe present a technique to extend Jacobian-based distortion (quality) measures
for planar triangles to high-order isoparametric elements of any interpolation degree on CAD parameterized surfaces. The resulting distortion (quality) measures are expressed in terms of the parametric coordinates of the nodes. These extended distortion (quality) measures can be used to check the quality and validity of a high-order surface mesh. We also apply them to simultaneously smooth and untangle high-order surface meshes by minimizing
the extended distortion measure. The minimization is performed in terms of the
parametric coordinates of the nodes. Thus, the nodes always lie on the surface. Finally,
we include several examples to illustrate the application of the proposed technique.Uso del vídeo (pencast) para el aprendizaje de matemáticas: La experiencia en la UPC
http://hdl.handle.net/2117/20225
Title: Uso del vídeo (pencast) para el aprendizaje de matemáticas: La experiencia en la UPC
Authors: Pozo Montero, Francesc; Parés Mariné, Núria; Vidal Seguí, YolandaFri, 27 Sep 2013 15:52:17 GMThttp://hdl.handle.net/2117/202252013-09-27T15:52:17ZPozo Montero, Francesc; Parés Mariné, Núria; Vidal Seguí, Yolandanomatemàtiques, vídeo, pencast, verbalitzacióPushing SEA beyond its limits: a model for real building structures
http://hdl.handle.net/2117/20190
Title: Pushing SEA beyond its limits: a model for real building structures
Authors: Díaz Cereceda, Cristina; Poblet-Puig, Jordi; Rodríguez Ferran, Antonio
Abstract: The main challenge for models of building acoustics is being able to consider all the geometrical and physical details of real structures with a reasonable computational cost for high frequencies. The SEA (Statistical Energy Analysis) framework is suitable for these frequencies, but presents some difficulties for dealing with complex structural configurations. For instance, modelling absorbing materials with SEA is an open issue, since they are neither reverberant subsystems nor conservative couplings. In this work, a model to account for absorbing materials with a SEA-like approach is performed. It is obtained by analogy with an electrical circuit. This approach is combined with numerical simulations in order to solve vibroacoustic problems in real structural configurations (including complex geometries or dissipative connections) throughout the entire frequency range required by regulations. The proposed technique is applied to modelling the sound insulation of double walls. These walls consist of two leaves of plasterboard connected through metallic studs and filled with a layer of absorbing material. The combination of numerical simulations and SEA arises as a good technique for modelling the acoustic behaviour of real life structures with an affordable computational cost.Wed, 25 Sep 2013 10:07:26 GMThttp://hdl.handle.net/2117/201902013-09-25T10:07:26ZDíaz Cereceda, Cristina; Poblet-Puig, Jordi; Rodríguez Ferran, AntonionoStatistical Energy Analysis, vibroacoustics, absorbing materialsThe main challenge for models of building acoustics is being able to consider all the geometrical and physical details of real structures with a reasonable computational cost for high frequencies. The SEA (Statistical Energy Analysis) framework is suitable for these frequencies, but presents some difficulties for dealing with complex structural configurations. For instance, modelling absorbing materials with SEA is an open issue, since they are neither reverberant subsystems nor conservative couplings. In this work, a model to account for absorbing materials with a SEA-like approach is performed. It is obtained by analogy with an electrical circuit. This approach is combined with numerical simulations in order to solve vibroacoustic problems in real structural configurations (including complex geometries or dissipative connections) throughout the entire frequency range required by regulations. The proposed technique is applied to modelling the sound insulation of double walls. These walls consist of two leaves of plasterboard connected through metallic studs and filled with a layer of absorbing material. The combination of numerical simulations and SEA arises as a good technique for modelling the acoustic behaviour of real life structures with an affordable computational cost.An energy model for the acoustic insulation of absorbing materials
http://hdl.handle.net/2117/20173
Title: An energy model for the acoustic insulation of absorbing materials
Authors: Díaz Cereceda, Cristina; Poblet-Puig, Jordi; Rodríguez Ferran, Antonio
Abstract: In this work an energy model for the acoustic insulation of absorbing ma-
terials is shown. This model is an extension of Statistical Energy Analysis (SEA) [1] in
order to account for the effect of non-conservative connections [2, 3].
The energy-based approach allows to solve sound insulation problems in large domains
(such as those in building acoustics) in an efficient way for the whole frequency range
required by regulations (50-5000 Hz). In particular, this approach is applied here for the
study of the insulating behaviour of an absorbing layer (mineral wool) filling the cavity of
a double wall. The absorbing layer is considered as a non-conservative connection between
the two leaves of the wall.
This model is combined with detailed numerical computations to obtain the loss factors
associated to the connection. With these parameters, a combined system including the
transmission between rooms and double walls can be stated.
Obtained results show that absorbing layers can be modelled as non-conservative cou-
plings and incorporated in an SEA-like system to compute the sound insulation in buildings
successfully.Fri, 20 Sep 2013 11:14:45 GMThttp://hdl.handle.net/2117/201732013-09-20T11:14:45ZDíaz Cereceda, Cristina; Poblet-Puig, Jordi; Rodríguez Ferran, AntonionoStatistical energy analysis, non-conservative couplings, absorbing materialsIn this work an energy model for the acoustic insulation of absorbing ma-
terials is shown. This model is an extension of Statistical Energy Analysis (SEA) [1] in
order to account for the effect of non-conservative connections [2, 3].
The energy-based approach allows to solve sound insulation problems in large domains
(such as those in building acoustics) in an efficient way for the whole frequency range
required by regulations (50-5000 Hz). In particular, this approach is applied here for the
study of the insulating behaviour of an absorbing layer (mineral wool) filling the cavity of
a double wall. The absorbing layer is considered as a non-conservative connection between
the two leaves of the wall.
This model is combined with detailed numerical computations to obtain the loss factors
associated to the connection. With these parameters, a combined system including the
transmission between rooms and double walls can be stated.
Obtained results show that absorbing layers can be modelled as non-conservative cou-
plings and incorporated in an SEA-like system to compute the sound insulation in buildings
successfully.Experimental and numerical characterization of metallic studs
http://hdl.handle.net/2117/20171
Title: Experimental and numerical characterization of metallic studs
Authors: Poblet-Puig, Jordi; Guigou-Carter, C; Villot, M; Rodríguez Ferran, Antonio
Abstract: In this paper, the characterization of metallic studs used to mount lightweight double wall systems is studied both experimentally and numerically. The metallic studs are usually considered by introducing translational and rotational springs to couple the plasterboards composing the double wall. Therefore, the characterization involves determining these spring characteristics. The performance of this type of lightweight double wall in terms of sound transmission is presented in a companion paper. Different experimental setups have been investigated to determine the equivalent translational and rotational spring values. These experimental setups are described and involve the measurement of an input mobility. A finite element model of the laboratory tests has been developed. Shell and massive finite elements are employed in order to reproduce the experimental setups. A comparison of the measured and numerical results is shown. The FEM modelling is intended to help in developing new type of studs for double walls in order to obtain better sound transmission performance.Fri, 20 Sep 2013 10:52:53 GMThttp://hdl.handle.net/2117/201712013-09-20T10:52:53ZPoblet-Puig, Jordi; Guigou-Carter, C; Villot, M; Rodríguez Ferran, AntonionoIn this paper, the characterization of metallic studs used to mount lightweight double wall systems is studied both experimentally and numerically. The metallic studs are usually considered by introducing translational and rotational springs to couple the plasterboards composing the double wall. Therefore, the characterization involves determining these spring characteristics. The performance of this type of lightweight double wall in terms of sound transmission is presented in a companion paper. Different experimental setups have been investigated to determine the equivalent translational and rotational spring values. These experimental setups are described and involve the measurement of an input mobility. A finite element model of the laboratory tests has been developed. Shell and massive finite elements are employed in order to reproduce the experimental setups. A comparison of the measured and numerical results is shown. The FEM modelling is intended to help in developing new type of studs for double walls in order to obtain better sound transmission performance.Numerical modeling of sound transmission in double walls
http://hdl.handle.net/2117/20169
Title: Numerical modeling of sound transmission in double walls
Authors: Poblet-Puig, Jordi; Vilaseca Cabo, Roger; Rodríguez Ferran, Antonio
Abstract: Numerical models for the calculation of sound transmission in double walls are presented. The finite element method (FEM) or analytical solutions (for rectangular domains) are used for the acoustic part of the problem while the wall vibration is solved by means of structural finite elements. The vibroacoustic problem is formulated in the frequency range: the acoustic domains (rooms) are described by the Helmholtz equation, the absorbent materials as an equivalent fluid and the structures by means of dynamic linear elasticity. The acoustic and structural parts of the problem are coupled. The influence of the stiffness and spacing of the studs on the performance of lightweight walls is studied. The studs have been modelled with beam finite elements or by means of mechanical constraints. The effect of the boundary conditions of the walls and its dimensions are also analyzed.Fri, 20 Sep 2013 10:37:47 GMThttp://hdl.handle.net/2117/201692013-09-20T10:37:47ZPoblet-Puig, Jordi; Vilaseca Cabo, Roger; Rodríguez Ferran, AntonionoNumerical models for the calculation of sound transmission in double walls are presented. The finite element method (FEM) or analytical solutions (for rectangular domains) are used for the acoustic part of the problem while the wall vibration is solved by means of structural finite elements. The vibroacoustic problem is formulated in the frequency range: the acoustic domains (rooms) are described by the Helmholtz equation, the absorbent materials as an equivalent fluid and the structures by means of dynamic linear elasticity. The acoustic and structural parts of the problem are coupled. The influence of the stiffness and spacing of the studs on the performance of lightweight walls is studied. The studs have been modelled with beam finite elements or by means of mechanical constraints. The effect of the boundary conditions of the walls and its dimensions are also analyzed.A phase-field fracture model of ferroelectric materials under electro-mechanical loading
http://hdl.handle.net/2117/19298
Title: A phase-field fracture model of ferroelectric materials under electro-mechanical loading
Authors: Abdollahi Hosnijeh, Amir; Arias Vicente, Irene
Abstract: A phase-field model is proposed for the coupled simulation of microstructure and fracture evolution in ferroelectric materials. The model is based on energetic phase-field approaches for brittle fracture and ferroelectric domain formation and evolution.
The variational nature of these approaches makes their coupling very natural. However the main challenge is to encode the
electro-mechanical conditions of the sharp crack faces into the phase-field framework since the crack in this model is smeared
and represented by an internal layer. We develope the model for different crack face boundary conditions. Simulations show the
microstructure induced by the presence of the crack. Interactions between the microstructure and the crack are investigated under different electro-mechanical loadings.Thu, 16 May 2013 12:58:07 GMThttp://hdl.handle.net/2117/192982013-05-16T12:58:07ZAbdollahi Hosnijeh, Amir; Arias Vicente, IrenenoCoupled simulation, Crack faces, Electro-mechanical, Ferroelectric domains, Fracture model, Internal layers, Phase fields, Phase-field approaches, Phase-field models, Sharp crackA phase-field model is proposed for the coupled simulation of microstructure and fracture evolution in ferroelectric materials. The model is based on energetic phase-field approaches for brittle fracture and ferroelectric domain formation and evolution.
The variational nature of these approaches makes their coupling very natural. However the main challenge is to encode the
electro-mechanical conditions of the sharp crack faces into the phase-field framework since the crack in this model is smeared
and represented by an internal layer. We develope the model for different crack face boundary conditions. Simulations show the
microstructure induced by the presence of the crack. Interactions between the microstructure and the crack are investigated under different electro-mechanical loadings.Numerical tool for modeling steel fiber reinforced concrete
http://hdl.handle.net/2117/17689
Title: Numerical tool for modeling steel fiber reinforced concrete
Authors: Molins i Borrell, Climent; Pros Parés, Alba; Díez, Pedro
Abstract: Steel Fiber Reinforced Concrete (SFRC) allows overcoming brittleness and weakness in tension, the main drawbacks of plain concrete. The goal of the present presentation is to present an ad-hoc numerical strategy to account for the contribution of the fibers in the simulation of the mechanical response of SFRC. In the model presented, the individual fibers immersed in the concrete bulk are accounted for in their actual location and orientation. The selected approach is based on the ideas introduced in the Immersed Boundary (IB) methods. These methods were developed to account for 1D (or 2D) solids immersed in 2D (or 3D) fluids. Here, the concrete bulk is playing the role of the fluid and the cloud of steel fibers is acting as the immerse boundary (that is a 1D structure in a 2D or 3D continuous). Thus, the philosophy of the IB methodology is used to couple the behavior of the two systems, the concrete bulk and the fiber cloud, precluding the need of matching finite element meshes. In the proposed approach, the meshes of the concrete bulk and fiber cloud are independent and the models are coupled imposing displacement compatibility and equilibrium of the two systems. The concrete bulk is modeled using any nonlinear model. The constitutive model for the fibers is designed to account for the complex interaction between fibers and concrete. The fiber models are based on previous investigations describing the concrete-fiber interaction and its dependence on the factors identified to be relevant: shape of the fiber (straight or hooked) and angle between the fiber and the crack plane. 3D examples with fibers distributed and oriented randomly are reproduced using the proposed approach.Tue, 12 Feb 2013 18:16:39 GMThttp://hdl.handle.net/2117/176892013-02-12T18:16:39ZMolins i Borrell, Climent; Pros Parés, Alba; Díez, PedronoPlain concrete, Steel Fiber Reinforced Concrete, Numerical Model, Immersed Boundary methods, Pullout test, Model Validation, Direct Tension Test, Three Point Bending TestSteel Fiber Reinforced Concrete (SFRC) allows overcoming brittleness and weakness in tension, the main drawbacks of plain concrete. The goal of the present presentation is to present an ad-hoc numerical strategy to account for the contribution of the fibers in the simulation of the mechanical response of SFRC. In the model presented, the individual fibers immersed in the concrete bulk are accounted for in their actual location and orientation. The selected approach is based on the ideas introduced in the Immersed Boundary (IB) methods. These methods were developed to account for 1D (or 2D) solids immersed in 2D (or 3D) fluids. Here, the concrete bulk is playing the role of the fluid and the cloud of steel fibers is acting as the immerse boundary (that is a 1D structure in a 2D or 3D continuous). Thus, the philosophy of the IB methodology is used to couple the behavior of the two systems, the concrete bulk and the fiber cloud, precluding the need of matching finite element meshes. In the proposed approach, the meshes of the concrete bulk and fiber cloud are independent and the models are coupled imposing displacement compatibility and equilibrium of the two systems. The concrete bulk is modeled using any nonlinear model. The constitutive model for the fibers is designed to account for the complex interaction between fibers and concrete. The fiber models are based on previous investigations describing the concrete-fiber interaction and its dependence on the factors identified to be relevant: shape of the fiber (straight or hooked) and angle between the fiber and the crack plane. 3D examples with fibers distributed and oriented randomly are reproduced using the proposed approach.A new procedure to smooth and untangle meshes on parameterized surfaces
http://hdl.handle.net/2117/17479
Title: A new procedure to smooth and untangle meshes on parameterized surfaces
Authors: Gargallo Peiró, Abel; Roca Navarro, Xevi; Sarrate Ramos, Josep
Abstract: We present a technique to extend any distortion (quality) measure for planar meshes to meshes on parameterized surfaces. The resulting distortion (quality) measure is expressed in terms of the parametric coordinates of the nodes. This extended distortion (quality) measure can be used to check the quality and validity of both triangle and quadrilateral surface meshes. We
also apply it to simultaneously smooth and untangle surface meshes by minimizing the extended distortion measure. The minimization is performed in terms of the parametric coordinates of the nodes and therefore, the nodes always lie on the surface. Finally, we include several examples to illustrate the applicability of the proposed technique. Specifically, we extend several Jacobian-based measures, and we us them to smooth and untangle triangle and quadrilateral meshes on CAD surfaces.Tue, 22 Jan 2013 13:20:16 GMThttp://hdl.handle.net/2117/174792013-01-22T13:20:16ZGargallo Peiró, Abel; Roca Navarro, Xevi; Sarrate Ramos, JosepnoWe present a technique to extend any distortion (quality) measure for planar meshes to meshes on parameterized surfaces. The resulting distortion (quality) measure is expressed in terms of the parametric coordinates of the nodes. This extended distortion (quality) measure can be used to check the quality and validity of both triangle and quadrilateral surface meshes. We
also apply it to simultaneously smooth and untangle surface meshes by minimizing the extended distortion measure. The minimization is performed in terms of the parametric coordinates of the nodes and therefore, the nodes always lie on the surface. Finally, we include several examples to illustrate the applicability of the proposed technique. Specifically, we extend several Jacobian-based measures, and we us them to smooth and untangle triangle and quadrilateral meshes on CAD surfaces.A geometric bridge between regularised damage and energetically equivalent cracks
http://hdl.handle.net/2117/17033
Title: A geometric bridge between regularised damage and energetically equivalent cracks
Authors: Tamayo Mas, Elena; Rodríguez Ferran, Antonio
Abstract: In order to achieve a better characterisation of a whole failure process, models which
combine damage and fracture mechanics have recently been proposed. Here, a new combined
methodology is presented: in order to describe damage inception and its diffuse propagation,
a gradient-enhanced continuum model based on smoothed displacements is used, which is coupled
to a discontinuous one to describe the final stages of the process.
Special emphasis should be placed on the difficulties concerning the transition between continuous
damage growth and fracture. On the one hand, and in order to conserve the energy
dissipation through the change of models, an appropriate cohesive law must be defined. In this
paper, the proposed technique to define this law is explained. On the other hand, the direction
of the crack path should be determined. Here, a new strategy is proposed: the discontinuity is
propagated following the direction dictated by the medial axis of the damaged domain. That is,
a geometric tool, widely used in the computer graphics field, is used here to locate cracks.Tue, 27 Nov 2012 13:23:46 GMThttp://hdl.handle.net/2117/170332012-11-27T13:23:46ZTamayo Mas, Elena; Rodríguez Ferran, AntonionoIn order to achieve a better characterisation of a whole failure process, models which
combine damage and fracture mechanics have recently been proposed. Here, a new combined
methodology is presented: in order to describe damage inception and its diffuse propagation,
a gradient-enhanced continuum model based on smoothed displacements is used, which is coupled
to a discontinuous one to describe the final stages of the process.
Special emphasis should be placed on the difficulties concerning the transition between continuous
damage growth and fracture. On the one hand, and in order to conserve the energy
dissipation through the change of models, an appropriate cohesive law must be defined. In this
paper, the proposed technique to define this law is explained. On the other hand, the direction
of the crack path should be determined. Here, a new strategy is proposed: the discontinuity is
propagated following the direction dictated by the medial axis of the damaged domain. That is,
a geometric tool, widely used in the computer graphics field, is used here to locate cracks.