Imperial College London

Pedro M. Baiz V.

Faculty of EngineeringDepartment of Computing

 
 
 
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Contact

 

+44 (0)7916 253 021p.m.baiz

 
 
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Location

 

ACE ExtensionSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
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53 results found

Toolabi M, Fallah AS, Louca L, 2018, Enhanced mixed interpolation XFEM formulations for discontinuousTimoshenko beam and Mindlin-Reissner plate, International Journal for Numerical Methods in Engineering, Vol: 115, Pages: 714-737, ISSN: 0029-5981

Shear locking is a major issue emerging in the computational formulation of beam and plate finite elements of minimal number of degrees of freedom as it leads to artificial overstiffening. In this paper, discontinuous Timoshenko beam and Mindlin‐Reissner plate elements are developed by adopting the Hellinger‐Reissner functional with the displacements and through‐thickness shear strains as degrees of freedom. Heterogeneous beams and plates with weak discontinuity are considered, and the mixed formulation has been combined with the extended finite element method (FEM); thus, mixed enrichment functions are used. Both the displacement and the shear strain fields are enriched as opposed to the traditional extended FEM where only the displacement functions are enriched. The enrichment type is restricted to extrinsic mesh‐based topological local enrichment. The results from the proposed formulation correlate well with analytical solution in the case of the beam and in the case of the Mindlin‐Reissner plate with those of a finite element package (ABAQUS) and classical FEM and show higher rates of convergence. In all cases, the proposed method captures strain discontinuity accurately. Thus, the proposed method provides an accurate and a computationally more efficient way for the formulation of beam and plate finite elements of minimal number of degrees of freedom.

Journal article

Tagarielli V, Matos MAS, Pinho S, Baiz Villafranca PMet al., 2018, Predictions of the electro-mechanical response of conductive CNT-polymer composites, Journal of the Mechanics and Physics of Solids, Vol: 114, Pages: 84-96, ISSN: 0022-5096

We present finite element simulations to predict the conductivity, elastic response and strain-sensing capability of conductive composites comprising a polymeric matrix and carbon nanotubes. Realistic representative volume elements (RVE) of the microstructure are generated and both constituents are modelled as linear elastic solids, with resistivity independent of strain; the electrical contact between nanotubes is represented by a new element which accounts for quantum tunnelling effects and captures the sensitivity of conductivity to separation. Monte Carlo simulations are conducted and the sensitivity of the predictions to RVE size is explored. Predictions of modulus and conductivity are found in good agreement with published results. The strain-sensing capability of the material is explored for multiaxial strain states.

Journal article

Houston C, Gooberman-Hill S, Mathie R, Kennedy A, Li Y, Baiz Pet al., 2017, Case study for the return on investment of Internet of Things using agent-based modelling and data science, Systems, Vol: 5, ISSN: 2079-8954

As technology advances towards new paradigms such as the Internet of Things, there is a desire among business leaders for a reliable method to determine the value of supporting these ventures. Traditional simulation and analysis techniques cannot model the complex systems inherent in fields such as infrastructure asset management, or suffer from a lack of data on which to build a prediction. Agent-based modelling, through an integration with data science, presents an attractive simulation method to capture these underlying complexities and provide a solution. The aim of this work is to investigate this integration as a refined process for answering practical business questions. A specific case study is addressed to assess the return on investment of installing condition monitoring sensors on lift assets in a London Underground station. An agent-based model is developed for this purpose, supported by analysis from historical data. The simulation results demonstrate how returns can be achieved and highlight features induced as a result of stochasticity in the model. Suggestions of future research paths are additionally outlined.

Journal article

Pathan MV, Tagarielli VL, Patsias S, Baiz-Villafranca PMet al., 2016, A new algorithm to generate representative volume elements of composites with cylindrical or spherical fillers, Composites Part B - Engineering, Vol: 110, Pages: 267-278, ISSN: 1359-8368

A new algorithm to generate random spatial distributions of cylindrical fibres and spheres is developed based on a constrained optimization formulation. All filler particles are generated simultaneously within the specimen domain; subsequently their position is iteratively perturbed to remove particle overlapping. The algorithm is able to achieve volume fractions of up to 0.8 in the case of circular cylindrical fibres of equal diameter; the method can be applied to any statistical distribution of fibre diameters. The spatial distribution of fibres and spheres is analysed by plotting spatial statistical metrics; it is shown that the microstructures generated are spatially random and similar to those observed in real fibre composites. The algorithm is employed to effectively predict the transversely isotropic elastic, damping and plastic properties of a unidirectional fibre composite by analysis of an RVE of smaller size than previously reported.

Journal article

De Carvalho NV, Chen BY, Pinho ST, Ratcliffe JG, Baiz PM, Tay TEet al., 2015, Modeling delamination migration in cross-ply tape laminates, COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING, Vol: 71, Pages: 192-203, ISSN: 1359-835X

Journal article

Phunpeng V, Baiz PM, 2015, Mixed finite element formulations for strain-gradient elasticity problems using the FEniCS environment, FINITE ELEMENTS IN ANALYSIS AND DESIGN, Vol: 96, Pages: 23-40, ISSN: 0168-874X

Journal article

Chen BY, Pinho ST, De Carvalho NV, Baiz PM, Tay TEet al., 2014, A floating node method for the modelling of discontinuities in composites, Engineering Fracture Mechanics, Vol: 127, Pages: 104-134, ISSN: 0013-7944

This paper presents a new method suitable for modelling multiple discontinuities within a finite element. The architecture of the proposed method is similar to that of the phantom node method (which is equivalent to XFEM with Heaviside enrichment), and the solution of it is equivalent to local remeshing within the cracked element. The new method shows several advantages over the phantom node method, such as avoiding errors in the mapping of the crack geometry from the physical to the natural space and avoiding performing integrations over only part of an element. Compared to remeshing, the proposed method enables the representation of discontinuities through relatively closed FE codes (such as user-defined elements) without modifying the initial mesh and geometry, thus making it computationally more efficient. Additionally, the proposed method is particularly suited for modelling weak and cohesive discontinuities and for the representation of complex crack networks; it can model multiple plies and interfaces of a composite laminate, and both matrix crack and delamination, within a user-defined element; the information is shared between the plies and interfaces within such an element, allowing the direct implementation of interactive mechanisms. Verification examples show that the floating node method can predict stress intensity factors and crack propagation accurately. An application example shows that the proposed method can predict well the transition from matrix cracking to delamination and the subsequent saturation of matrix crack density in a cross-ply laminate.

Journal article

De Carvalho NV, Ratcliffe JG, Chen BY, Pinho ST, Baiz PM, Tay TEet al., 2014, Modeling Quasi-static and fatigue-driven delamination migration

An approach was proposed and assessed for the high-fidelity modeling of progressive damage and failure in composite materials. It combines the Floating Node Method (FNM) and the Virtual Crack Closure Technique (VCCT) to represent multiple interacting failure mechanisms in a mesh-independent fashion. Delamination, matrix cracking, and migration were captured using failure and migration criteria based on fracture mechanics. Quasi-static and fatigue loading were modeled within the same overall framework. The methodology proposed was illustrated by simulating the delamination migration test, showing good agreement with the available experimental data.

Conference paper

Pinho ST, Chen BY, De Carvalho NV, Baiz PM, Tay TEet al., 2014, Accurate numerical simulation of kinking cracks in composites

This paper presents a new method suitable for modelling kinking discontinuities within a finite element framework. The proposed method effectively implements local remeshing in terms of solution, but is computationally more efficient than remeshing; it can be readily implemented in relatively closed FE codes; and it allows (sub-)elements near a crack tip to readily share information. The finite element architecture of the new method is similar to that of the phantom node method. Validation examples show that the proposed method can predict stress intensity factors and crack propagation accurately. An application example shows that the proposed method can predict the transition from matrix cracking to delamination in cross-ply composite laminates by accurately representing T-shaped cracks inside an element.

Conference paper

De Carvalho NV, Ratcliffe JG, Chen BY, Pinho ST, Baiz PM, Tay TEet al., 2014, Modeling Quasi-static and fatigue-driven delamination migration, Publisher: DEStech Publications

An approach was proposed and assessed for the high-fidelity modeling of progressive damage and failure in composite materials. It combines the Floating Node Method (FNM) and the Virtual Crack Closure Technique (VCCT) to represent multiple interacting failure mechanisms in a mesh-independent fashion. Delamination, matrix cracking, and migration were captured using failure and migration criteria based on fracture mechanics. Quasi-static and fatigue loading were modeled within the same overall framework. The methodology proposed was illustrated by simulating the delamination migration test, showing good agreement with the available experimental data.

Conference paper

Toolabi M, Fallah AS, Baiz PM, Louca LAet al., 2013, Dynamic analysis of a viscoelastic orthotropic cracked body using the extended finite element method, Engineering Fracture Mechanics, Vol: 109, Pages: 17-32, ISSN: 0013-7944

The extended finite element method (XFEM) is found promising in approximating solutions to locally non-smooth features such as jumps, kinks, high gradients, inclusions, voids, shocks, boundary layers or cracks in solid or fluid mechanics problems. The XFEM uses the properties of the partition of unity finite element method (PUFEM) to represent the discontinuities without the corresponding finite element mesh requirements. In the present study numerical simulations of a dynamically loaded orthotropic viscoelastic cracked body are performed using XFEM and the J-integral and stress intensity factors (SIF’s) are calculated. This is achieved by fully (reproducing elements) or partially (blending elements) enriching the elements in the vicinity of the crack tip or body. The enrichment type is restricted to extrinsic mesh-based topological local enrichment in the current work. Thus two types of enrichment functions are adopted viz. the Heaviside step function replicating a jump across the crack and the asymptotic crack tip function particular to the element containing the crack tip or its immediately adjacent ones. A constitutive model for strain-rate dependent moduli and Poisson ratios (viscoelasticity) is formulated. A symmetric double cantilever beam (DCB) of a generic orthotropic material (mixed mode fracture) is studied using the developed XFEM code. The same problem is studied using the viscoelastic constitutive material model implemented in ABAQUS through an implicit user defined material subroutine (UMAT). The results from XFEM correlate well with those of the finite element method (FEM). Three cases viz. static, dynamic and viscoelastic dynamic are studied. It is shown that there is an increase in the value of maximum J-integral when the material exhibits strain rate sensitivity.

Journal article

Wong LLC, Villafranca PMB, Menner A, Bismarck Aet al., 2013, Hierarchical Polymerized High Internal Phase Emulsions Synthesized from Surfactant-Stabilized Emulsion Templates, LANGMUIR, Vol: 29, Pages: 5952-5961, ISSN: 0743-7463

Journal article

De Carvalho NV, Chen BY, Pinho ST, Baiz PM, Ratcliffe JG, Tay TEet al., 2013, Floating node method and virtual crack closure technique for modeling matrix cracking-delamination migration, Pages: 4344-4355

Conference paper

Pinho ST, Chen BY, De Carvalho NV, Baiz PM, Tay TEet al., 2013, A floating node method for the modelling of discontinuities within a finite element, Pages: 516-527

Conference paper

Chen BY, Tay TE, Baiz PM, Pinho STet al., 2013, Numerical analysis of size effects on open-hole tensile composite laminates, Composites Part A: Applied Science and Manufacturing, Vol: 47, Pages: 52-62

The tensile strength of open-hole fibre reinforced composite laminates depends on in-plane, thickness and ply lay-up scaling. Translaminar (fibre direction) mode I fracture toughness has recently been experimentally determined to be thickness dependent. This paper presents a computational study of the tensile strength prediction of open-hole laminates using a cohesive zone model. To the authors’ knowledge, it is for the first time in the literature that the thickness-dependence of translaminar fracture toughness is accounted for in the numerical modelling of composites. The thickness size effect in the strength of open-hole composite laminates failed by pull-out is accurately predicted for the first time by a deterministic model. It is found that neglecting delamination in the numerical models will lead to mesh-dependency and over-estimation on the predicted strength. Smeared crack model with cohesive elements to model delamination is able to predict the correct failure mode; but it is found not suitable for accurate strength predictions for laminates failed by delamination.

Journal article

Baiz PM, Chen BY, Pinho ST, Tay TEet al., 2013, Modelling Multiple Discontinuities within an Element for Applications in Composite Fracture, UK National Conference on Computational Mechanics in Engineering

Conference paper

Baiz PM, Hale J, 2012, A Meshless Method for the Reissner-Mindlin Plate Model based on a Stabilised Mixed Weak Form, 13th International Conference on Boundary Elements Techniques

Conference paper

Leung H, Baiz PM, 2012, Partition of Unity and Drilling Rotations in the Boundary Element Method (BEM), International Journal of Solids and Structures

Journal article

Chen B, Baiz PM, Pinho ST, Tay TEet al., 2012, An Extended Phantom Node Method for Crack Interactions in Composites, ECCOMAS 2012

Conference paper

Hale JS, Baiz PM, 2012, A locking-free meshfree method for the simulation of shear-deformable plates based on a mixed variational formulation, Computer Methods in Applied Mechanics and Engineering

The problem of shear-locking in the thin-plate limit is a well known issue that must be overcome when discretising the Reissner-Mindlin plate equations. In this paper we present ashear-locking-freemethod utilising meshfree maximum-entropy basis functions and rotated Raviart-Thomas-Nédélec elements within amixedvariationalformulation. The formulation draws upon well known techniques in the finite element literature. Due to the inherent properties of the maximum-entropy basis functions our method allows for the direct imposition of Dirichlet (essential) boundary conditions, in contrast to methodsbased on moving least squares basis functions. We present benchmark problems that demonstrate the accuracy and performance of the proposed method.

Journal article

Chen B, Tay TE, Baiz PM, Pinho STet al., 2011, Size effects in progressive damage of notched and holed composites

Conference paper

Natarajan S, Baiz PM, Bordas S, Rabczuk T, Kerfriden Pet al., 2011, Natural frequencies of cracked functionally graded material plates by the extended finite element method, COMPOSITE STRUCTURES, Vol: 93, Pages: 3082-3092, ISSN: 0263-8223

Journal article

Natarajan S, Baiz PM, Ganapathi M, Kerfriden P, Bordas Set al., 2011, Linear free flexural vibration of cracked functionally graded plates in thermal environment, COMPUTERS & STRUCTURES, Vol: 89, Pages: 1535-1546, ISSN: 0045-7949

Journal article

Baiz PM, 2011, Application of Partition of Unity concepts in the Boundary Element Method (Keynote), XFEM 2011 (The eXtended Finite Element Method, Partition of Unity Enrichment: Recent Developments and Applications)

Conference paper

Tavares SMO, Häusler SM, Baiz PM, de Castro PMST, Horst P, Aliabadi MHet al., 2011, Crack Growth Simulation in Integrally Stiffened Structures Including Residual Stress Effects from Manufacturing. Part II: Modelling and Experiments Comparison, SDHM: Structural Durability & Health Monitoring, Vol: 7, Pages: 191-210

This article is the second part of a two parts paper which presents, compares and discusses the different crack growth simulation models which were introduced for fatigue crack growth assessment during the DaToN project. In the first part, different simulation approaches were applied to determine a calibration of the stress intensity factors as a function of the crack length for a two stiffeners panel with a central crack. Due to the residual stress field promoted by the different manufacturing processes, its influence was included in the numerical models to determine the stress intensity factors. In this second part, the stress intensity factors calibrations are applied in different crack growth models in order to determine the fatigue life under cyclic loads. Paris, Walker, Forman and NASGRO were used for this purpose. The incorporation of the load ratio variation and of the effect of the residual stresses is in general possible in all of them allowing to determine the influence of the residual stress field in the fatigue crack growth. The results were tested and compared with experimental results with the purpose of validation of the models. These numerical models demonstrate that (i) it is possible to predict the fatigue life in stiffened welded panels and (ii) the residual stress field originated by welding processes can be detrimental or beneficial depending on the location where the crack starts.

Journal article

Häusler SM, Baiz PM, Tavares SMO, Brot A, Horst P, Aliabadi MH, de Castro PMST, Peleg-Wolfin Yet al., 2011, Crack Growth Simulation in Integrally Stiffened Structures Including Residual Stress Effects from Manufacturing. Part I: Model Overview, SDHM: Structural Durability & Health Monitoring, Vol: 7, Pages: 163-190

This article represents the first part of a two-part article which presents, compares and discusses the different crack growth simulation models which were introduced for fatigue crack growth assessment during the DaToN project. The project was funded by the EC within the 6th framework program and was specifically devoted to investigate innovative manufacturing techniques for metallic structures with special focus on the effects of residual stresses on the fatigue crack growth and residual strength behaviour. Within this first part the different simulation approaches, including the residual stress modelling approaches will be introduced and stress intensity factor results will be presented and compared. Within this context it could be observed that residual stress effects do have a significant influence on the resulting stress intensity factor solution whose magnitude strongly depends on the input parameters (residual stress field input) but also, to certain extent, on the simulation approaches for stress intensity factor determination as well as residual stress modelling. The residual stress effect also plays an important role for the fatigue crack growth simulations which will be presented in detail in the second part including a comparison with fatigue crack growth results from experiments.

Journal article

Baiz PM, Natarajan S, Bordas SPA, Kerfriden P, Rabczuk Tet al., 2011, Linear buckling analysis of cracked plates by SFEM and XFEM, Journal of Mechanics of Materials and Structures, Vol: 6, Pages: 1213-1238

In this paper, the linear buckling problem for isotropic plates is studied using a quadrilateral element with smoothed curvatures and the extended finite element method. First, the curvature at each point is obtained by a nonlocal approximation via a smoothing function. This element is later coupled with partition of unity enrichment to simplify the simulation of cracks. The proposed formulation suppresses locking and yields elements which behave very well, even in the thin plate limit. The buckling coefficient and mode shapes of square and rectangular plates are computed as functions of crack length, crack location, and plate thickness. The effects of different boundary conditions are also studied.

Journal article

Baiz PM, Albuquerque EL, Sollero P, 2011, Drilling Rotations and Partition of Unity in Composite Plates by the Boundary Element Method, 12th International Conference on Boundary Elements Techniques

Conference paper

Wen PH, Dirgantara T, Aliabadi MH, Baiz PMet al., 2010, The Boundary Element Method for Geometrically Nonlinear Analyses of Plates and Shells, Boundary Element Methods in Engineering and Sciences, Editors: Aliabadi, Wen, Publisher: Imperial College Pr, ISBN: 9781848165793

Book chapter

Baiz PM, 2010, Drilling Rotations in BEM, 11th International Conference on Boundary Elements Techniques.

Conference paper

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