2,005 research outputs found
Isogeometric FEM-BEM coupled structural-acoustic analysis of shells using subdivision surfaces
We introduce a coupled finite and boundary element formulation for acoustic
scattering analysis over thin shell structures. A triangular Loop subdivision
surface discretisation is used for both geometry and analysis fields. The
Kirchhoff-Love shell equation is discretised with the finite element method and
the Helmholtz equation for the acoustic field with the boundary element method.
The use of the boundary element formulation allows the elegant handling of
infinite domains and precludes the need for volumetric meshing. In the present
work the subdivision control meshes for the shell displacements and the
acoustic pressures have the same resolution. The corresponding smooth
subdivision basis functions have the continuity property required for the
Kirchhoff-Love formulation and are highly efficient for the acoustic field
computations. We validate the proposed isogeometric formulation through a
closed-form solution of acoustic scattering over a thin shell sphere.
Furthermore, we demonstrate the ability of the proposed approach to handle
complex geometries with arbitrary topology that provides an integrated
isogeometric design and analysis workflow for coupled structural-acoustic
analysis of shells
Active nonrigid ICP algorithm
© 2015 IEEE.The problem of fitting a 3D facial model to a 3D mesh has received a lot of attention the past 15-20 years. The majority of the techniques fit a general model consisting of a simple parameterisable surface or a mean 3D facial shape. The drawback of this approach is that is rather difficult to describe the non-rigid aspect of the face using just a single facial model. One way to capture the 3D facial deformations is by means of a statistical 3D model of the face or its parts. This is particularly evident when we want to capture the deformations of the mouth region. Even though statistical models of face are generally applied for modelling facial intensity, there are few approaches that fit a statistical model of 3D faces. In this paper, in order to capture and describe the non-rigid nature of facial surfaces we build a part-based statistical model of the 3D facial surface and we combine it with non-rigid iterative closest point algorithms. We show that the proposed algorithm largely outperforms state-of-the-art algorithms for 3D face fitting and alignment especially when it comes to the description of the mouth region
Isogeometric FEM-BEM coupled structural-acoustic analysis of shells using subdivision surfaces
We introduce a coupled finite and boundary element formulation for acoustic
scattering analysis over thin shell structures. A triangular Loop subdivision
surface discretisation is used for both geometry and analysis fields. The
Kirchhoff-Love shell equation is discretised with the finite element method and
the Helmholtz equation for the acoustic field with the boundary element method.
The use of the boundary element formulation allows the elegant handling of
infinite domains and precludes the need for volumetric meshing. In the present
work the subdivision control meshes for the shell displacements and the
acoustic pressures have the same resolution. The corresponding smooth
subdivision basis functions have the continuity property required for the
Kirchhoff-Love formulation and are highly efficient for the acoustic field
computations. We validate the proposed isogeometric formulation through a
closed-form solution of acoustic scattering over a thin shell sphere.
Furthermore, we demonstrate the ability of the proposed approach to handle
complex geometries with arbitrary topology that provides an integrated
isogeometric design and analysis workflow for coupled structural-acoustic
analysis of shells
On the modelling of ultrasonic testing using boundary integral equation methods
Ultrasonic nondestructive testing has important applications in, for example, the nuclear
power and aerospace industries, where it is used to inspect safety-critical parts for flaws.
For safe and reliable testing, mathematical models of the ultrasonic measurement systems
are invaluable tools. In this thesis such measurement models are developed for the ultrasonic
testing for defects located near non-planar surfaces. The applications in mind are
the testing of nuclear power plant components such as thick-walled pipes with diameter
transitions, pipe connections, etc. The models use solution methods based on frequency
domain boundary integral equation methods, with a focus on analytical approaches for the
defects and regularized boundary element methods for the non-planar surfaces. A major
benefit of the solution methods is the ability to provide accurate results both for low, intermediate
and high frequencies. The solution methods are incorporated into a framework
of transmitting probe models based on prescribing the traction underneath the probe and
receiving probe models based on electromechanical reciprocity. Time traces are obtained
by applying inverse temporal Fourier transforms, and it is also shown how calibration and
effects of material damping can be included in the models
An integrated design-analysis framework for three dimensional composite panels
We present an integrated design-analysis framework for three dimensional composite panels. The main components of the proposed framework consist of (1) a new curve/surface offset algorithm and (2) the isogeometric concept recently emerged in the computational mechanics community. Using the presented approach, finite element analysis of composite panels can be performed with the only input is the geometry representation of the composite surface. In this paper, non-uniform rational B-splines (NURBS) are used to represent the panel surfaces. A stress analysis of curved composite panel with stiffeners is provided to demonstrate the proposed framework
Finite Element Modeling of Episodic Edifices
Episodic edifices have a diversity of significant solicitations in contemporary machineries and engineering owing to their exclusive electromagnetic properties. Frequently used episodic edifices comprise; occurrence selective surfaces, visual grilles, phased collection projections, photonic bandgap supplies, and numerous metamaterials. The scrutiny of episodic edifices has all the time been a significant area in computational electromagnetics. This episode, describes a precise and effectual arithmetical study, grounded on a higher-order finite element method (FEM), for depicting the electromagnetic properties of an episodic edifices. Grounded on the Floquet theory, episodic frontier conditions and radioactivity conditions are foremost resultant for the unit cell of an episodic edifice. The FEM is formerly applied to unravel Maxwell’s reckonings in the unit cell. To augment the precision and effectiveness of the FEM, rounded elements are employed to discretize the unit cell and higherorder course basis functions are used to enlarge the electrical arena. The asymptotic waveform evaluation (AWE) is applied to implement wild frequency and rawboned curves. To prove the proficiency of the projected FEM, we apply it to the scrutiny of episodic absorbers, incidence selective edifices, and phased collection aerial. For the aerial analysis, a severe waveguide port condition is industrialized to precisely model the aerial feed edifices. In all the occurrences premeditated, acceptable outcomes are obtained. Key words: Episodic, edifice, absorbers, waveguide, electromagnetic. DOI: 10.7176/CEIS/10-1-0
Drape simulation using solid-shell elements and adaptive mesh subdivision
In this paper, 4-node quadrilateral and 3-node triangular solid-shell elements are applied to drape simulations. With locking issues alleviated by the assumed natural strain method and plane-stress enforcement, static and dynamic drape problems are attempted by the quadrilateral element. If the drape is deep and the mesh density is inadequate, non-realistic sharp folds are predicted due to the non-physical interpenetration of top and bottom element surfaces. To avoid the interpenetration, a reversible adaptive subdivision based on the 1–4 splitting method is developed. To ensure displacement compatibility among elements at different subdivision levels, macro-transition elements are formed by quadrilateral and triangular solid-shell elements. To reduce the dynamic oscillation induced by newly inserted nodes, the discrete Kirchhoff condition is employed to determine the related nodal variables. Dynamic drape examples using adaptive meshing are presented. It can be seen that the predictions look realistic and deep drapes can be predicted with the interpenetration avoided yet the required number of nodes can be kept relatively small.postprin
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