Investigating CURVIC Coupling BehaviorBy Utilizing The Two- And Three-dimensionalBoundary And Finite Element Methods

A finite element–boundary element method for advection–diffusion problems with variable advective fields and infinite domains

To get individualized facial three-dimensional finite element (FE) model from transformation of a generic one to assist orthodontic analysis and prediction of treatment-related morphological change of facial soft tissue. A generic three-dimensional FE model of craniofacial soft and hard tissue was constructed based on a volunteer's spiral CT data. Seven pairs of main peri-oral muscles were constructed based on a combination of CT image and anatomical method. Individualized model could be obtained through transformation of the generic model based on selection of corresponding anatomical landmarks and radial basis functions (RBF) method. Validation was analyzed through superimposition of the transformed model and cone-beam CT (CBCT) reconstruction data. Pre- and post-treatment CBCT data of two patients were collected, which were superimposed to gain the amount of anterior teeth retraction and anterior alveolar surface remodeling that could be used as boundary condition. Different values of Poisson ratio ν and Young's modulus E were tested during simulation. Average deviation was 0.47 mm and 0.75 mm in the soft and hard tissue respectively. It could be decreased to a range of +0.29 mm and -0.21 mm after a second transformation at the lip-mouth region. The best correspondence between simulation and post-treatment result was found with elastic properties of soft tissues defined as follows. Poisson ratio ν for skin, muscle and fat being set as 0.45 while Young's modulus being set as 90.0 kPa, 6.2 kPa and 2.0 kPa respectively. Individualized three-dimensional facial FE model could be obtained through mathematical model transformation. With boundary condition defined according to treatment plan such FE model could be used to analyze the effect of orthodontic treatment on facial soft tissue.

Composite honeycomb sandwich structure is widely used in aircraft wing leading edge, rudder surface, engine fairing, etc. It is susceptible to strong aerodynamic noise and impact loads from birds, hails, and stones. Therefore, it is essential to evaluate the life of structure with sound and collision load. In this paper, an acoustic fatigue life evaluation method based on vibro-acoustic coupling with impact damage is proposed. A representative composite honeycomb sandwich structure is built up to implement the proposed method. Firstly, the low-velocity impact process is simulated by the finite element (FE) method. This analysis case is used to get the structure with damage and material degradation. Secondly, the FE model is linked with the acoustic indirect boundary element (BE) model. A white Gaussian noise load is applied to the coupled FE/indirect BE model, and the power spectral density (PSD) curve of the structural dangerous point is obtained by modal-based vibro-acoustic coupling response case and random post-processing analysis case. At last, the fatigue life of the honeycomb structure is computed by the PSD theory. The result shows that with the increase of the impact energy, the structural life under the same acoustic load decreases. This method reveals high computational efficiency and excellent feasibility. The analytical result has reference value for the acoustic and mechanical properties design of composite honeycomb sandwich structure.

A combined experimental and numerical study of the acoustic noise from a small form factor hard disk drive (HDD) is made to investigate the relative contribution of structure-borne idle noise to the total generated noise. Initially, the idle noise of a 1.8″ HDD was measured in an anechoic chamber, and a clear high-frequency peak is found in its total idle noise frequency spectrum. Then the modeling and simulation (M&S) of the top cover vibration and the associated sound radiation are performed to identify the dominant source and transmission path causing this noise peak. The M&S process consists of a 3D structural finite element (FE) modeling of the HDD to calculate the frequency-domain vibration response of the top cover, and a boundary element (BE) modeling of the HDD for calculating the radiated sound pressure. The loading specified in the FE model is motor torque ripple: the dominant electromagnetic excitation of fluid dynamic bearing spindle motor for HDDs. Finally, the obtained acoustic BE results of the sound pressure levels at a selected field point are compared to those measured physically in the chamber. It is shown that for the HDD considered, the coincidence of a high-frequency resonant mode with the fifth harmonic frequency of motor torque ripple is responsible for the high-frequency peak noise in the idle noise spectrum.

Analysis of problems in elasto-plasticity via an adaptive FEM–BEM coupling method

A coupled system of finite elements and boundary elements is presented for the modelling of sound propagation in a nonuniform mean flow. Finite elements are used to discretize the acoustic pressure in a bounded computational domain including the nonuniform flow field. The radiation of acoustic waves in the exterior uniform flow field is modelled by a boundary integral representation formula. The interface condition on the shared boundary yields an integral equation which is solved using boundary elements. The coupling of finite elements and boundary elements is described in detail for sound propagation in a stationary fluid where the acoustic pressure is governed by the Helmholtz equation. The coupled computational system is applied to estimate scattering and refractive effects on the acoustic pressure waves through a boundary layer surrounding an aircraft’s fuselage. The coupled mathematical formulation for three dimensional sound radiation around an engine in subsonic flow is discussed.

Tunnels buried deep within the earth constitute an important class geomechanics problems. Two numerical techniques used for the analysis of geomechanics problems, the finite element method and the boundary element method, have complementary characteristics for applications to problems of this type. The usefulness of combining these two methods for use as a geomechanics analysis tool has been recognized for some time, and a number of coupling techniques have been proposed. However, not all of them lend themselves to efficient computational implementations for large-scale problems. This report examines a coupling technique that can form the basis for an efficient analysis tool for large scale geomechanics problems through the use of an iterative equation solver.

The Biomechanics of a Validated Finite Element Model of Stress Shielding in a Novel Hybrid Total Knee Replacement

This paper reports on the development of a finite element — boundary element coupling procedure for the analysis of arbitrary shaped elastic bodies subjected to dynamic loads. The coupling is accomplished through equilibrium and compatibility considerations along the boundary element — finite element interface.

Finite element analysis of the lumbar spine in adolescent idiopathic scoliosis subjected to different loads

Purpose – A three-dimensional finite element (FE) model is developed to design a vibrating bimorph piezoelectric cantilever beam with lead zirconate titanate (PZT-5H) for energy harvesting. The paper aims to discuss these issues. Design/methodology/approach – A parametric study of electric power generated as a function of the dielectric constant, transverse piezoelectric strain constant, length and thickness of the piezoelectric material, is conducted for a time-harmonic surface pressure load. Transversely isotropic elastic and piezoelectric properties are assigned to the bimorph layers with brass chosen as the substrate material in the three-dimensional FE model. Using design of experiments, a study was conducted to determine the sensitivity of power with respect to the geometric and material variables. Findings – The numerical analysis shows that a uniform decrease in thickness and length coverage of the piezoelectric layers results in a nonlinear reduction in power amplitude, which suggests optimal values. The piezoelectric strain coefficient, d31 and the thickness of PZT-5H, tp, are the most important design parameters to generate high electric energy for bimorph vibration harvesting device. Originality/value – The work demonstrates that, through a sensitivity analysis, the electro-mechanical piezoelectric coupling coefficient (d31) and the thickness of the piezoelectric strips (tp) are the most important parameters which have a significant effect on power harvested.

The driving force and mode mixity for cracks near interfaces was examined via experimental measurements of the crack tip displacement field with moire interferometry, verified using boundary element modeling, and further explored with finite element modeling. The stress intensity factor was obtained by a collocation method in which the Westergaard crack tip expansions are used for displacements [1]. The method of fundamental solutions was employed so that displacements across the material interface could be used [2]. Boundary element simulations provide verification of the method and allow a comparison with experiment. Systematic finite element simulations enable a study of how residual stresses may affect crack trajectories and driving forces.

BEM and penalty FEM models for viscous incompressible fluids

This study investigates the feasibility of an alternative structural health monitoring (SHM) technique for an existing, post-tensioned, prestressed concrete bridge in Niigata, Japan. Currently, a static SHM system is in place to detect the progress of damages within the bridge. However, the existing system cannot properly monitor the structural health of the bridge including the periodic vibration, which is one of the damage-sensitive features of interest. Therefore, to effectively detect the real-time performances of the bridge, a three-dimensional (3D) Finite Element (FE) model was developed as a reference and verified using on-site load-deflection test results. After validating the reference FE model, different damage scenarios, such as degradation of concrete, corrosion & rupture of steel tendons and missing tendons, were incorporated in the FE models. Based on non-linear structural and Eigenvalue analyses, natural frequencies and mode shapes of the bridge remain constant even after careful consideration of all types of damages in the FE model. However, vertical displacements are observed to increase for the damage scenarios. Although the effect of tendon rupture and corrosion showed negligible influences on the vertical displacement, the deterioration of the concrete largely influenced the vertical displacement. Additionally, crack widths were found to vary with damage types. Brifely, this study recommends some effective indicators to monitor the structural conditions of the bridge using FE analysis (FEA).

Dynamic interaction analysis of an end bearing pile and soil has been analyzed using Boundary Element Method coupled with the Finite Element Method. The system considered is an end bearing single pile embedded in soil laying on a bed rock. The bedrock is considered as a rigid material. The system is subjected to upward propagating harmonic shear wave. The displacement of the pile has to be found. The pile is modelled using finite elements and the soil is modelled with boundary element. In this analysis, the domain of integration assumes that the pile surface is a plane. A computer program using FORTRAN is developed for the purpose of this study. A parametric study is made in this study . The parameter is nondimensional frequency, slenderness ratio and ratio modulus of elasticity. Conclusions of this study is the ratio of pile length to wave length determined the responds of the pile.