Search results for "Finite element"

Numerical experimental analysis of hybrid double lap aluminum-CFRP joints

2015

Abstract Due to their reliability and ease of assembly, both the adhesively bonded and the mechanical joints are commonly used in different fields of modern industrial design and manufacturing, to joint composite materials or composites with metals. As it is well known, adhesively bonded joints are characterized by high stiffness and good fatigue life, although delamination phenomena localized near the free edges may limit their use, especially for applications where corrosive environments and/or moisture can lead to premature failure of the bonding. In these cases, a possible alternative is given by the well-known mechanical joints. On the contrary, these last joints (bolted, riveted) requ…

Ritz Solution for Transient Analysis of Variable-Stiffness Shell Structures

2020

The dynamic response of thin-walled structures is driven by mass and stiffness distribution. As such, variable-stiffness (VS) composites offer opportunities to tune structural dynamic responses. To this extent, efficient analysis tools become increasingly important for structural analysis and design purposes. In this work, an efficient and versatile Ritz method for free vibrations and linear transient analysis of VS doubly curved shell structures is presented. VS shell structures are modeled as an assembly of shell-like domains. The shell kinematics is based on the first-order shear deformation theory, and no further assumption is made on the shallowness or on the thinness of the structure.…

STUDIO DELLE PROPRIETÀ MECCANICHE ED ELETTROMECCANICHE DI NANOCOMPOSITI E NANOFIBRE MEDIANTE APPROCCI NUMERICI

Technical and economical comparison between NdFeB and hard ferrites linear electrical generators from sea waves

2015

In this paper the authors perform a technical-economic comparison of two different Tubular Permanent Magnet Linear Machines for sea waves generation by using finite elements analysis. The first configuration includes ferrite rings while the second configuration includes neodymium-iron-boron rings. In order to compare the two types in economic and technical terms, a detailed analysis of the main figures of merit of the two configurations has been carried out. In particular, significant data such as flux distribution, rated voltage and current, axial force, electric power, realization cost and maintenance cost have been compared.

Modelling the Electromechanical Impedance Method for the Prediction of the Biomechanical Behavior of Dental Implant Stability

2015

Abstract We propose the electromechanical impedance (EMI) technique to assess the stability of dental implants. The technique consists of bonding a piezoelectric transducer to the element to be monitored. Conventionally, electromechanical admittance is used to diagnose structural damage. In this study, we created a 3D finite element model to mimic a transducer bonded to the abutment of a dental implant placed in a host bone site. We simulated the healing after surgery by changing the Young's modulus of the bone-implant interface. The results show that as the Young's modulus of the interface increases, the electromechanical characteristic of the transducer changes.

Functional a posteriori error estimates for boundary element methods

2019

Functional error estimates are well-established tools for a posteriori error estimation and related adaptive mesh-refinement for the finite element method (FEM). The present work proposes a first functional error estimate for the boundary element method (BEM). One key feature is that the derived error estimates are independent of the BEM discretization and provide guaranteed lower and upper bounds for the unknown error. In particular, our analysis covers Galerkin BEM and the collocation method, what makes the approach of particular interest for scientific computations and engineering applications. Numerical experiments for the Laplace problem confirm the theoretical results.

Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEM) of a Customized Stent-Graft for Endovascular (EVAR) Treatment of Abdominal Aorti…

2023

Background: The treatment of abdominal aortic aneurysm (AAA) is today commonly treated by inserting a stent-graft by the endovascular route, without resorting to open surgery. However, some clinical cases do not allow this less invasive approach, meaning that the stent-graft cannot be inserted and open surgery is used. Methods: In the study, we propose a fluid–structure interaction (FSI) analysis of an aneurysmatic aorta that could not be treated with Endovascular Aneurysm Repair (EVAR). The vessel is reconstructed through segmentation from CT scans and subsequently modeled on CAD software to create the surface and thickness of the vessel itself. Subsequently, we proceeded to carry out Comp…

Efficiency Improvement of Permanent-magnet Synchronous Motor Drives for Household Appliances

2011

This paper deals with some aspects of efficiency improvement of PMSMD (Permanent Magnet Synchronous Motor Drives). Particularly two aspects are focused: the control algorithm for the PMSMD, which allows to reduce the power losses of the electric drive without penalty on its dynamic performances and the optimization of an IPMSM (Interior Permanent Magnet Synchronous Motor) rotor configuration capable to increase the performances in terms of shaft torque production, limiting at the same time the rotor leakage flux. The loss minimization algorithm is here briefly analysed, a test bed for experimental validation is presented and the data are analysed. Experimental tests have been performed aimi…

Partial Discharges in HVDC Cables - The Effect of the Temperature Gradient During Load Transients

2021

The paper investigates the role of the space charge accumulation phenomena in the inception of Partial Discharges (PD) in a defect within the bulk of the dielectrics of a High Voltage Direct Current (HVDC) cable. It is widespread accepted that the number of PD occurring in an HVDC cable during its lifetime is largely less than that under AC voltage stress. This is essentially due to higher values of the voltage between the conductor and the screen needed to trigger PD under a steady DC voltage than the same value under AC stress. Nevertheless, due to the dependency of the electrical conductivity of the insulation on the electric field and temperature, PD in HVDC cables is strongly influence…

Generalized wave propagation problems and discrete exterior calculus

2018

We introduce a general class of second-order boundary value problems unifying application areas such as acoustics, electromagnetism, elastodynamics, quantum mechanics, and so on, into a single framework. This also enables us to solve wave propagation problems very efficiently with a single software system. The solution method precisely follows the conservation laws in finite-dimensional systems, whereas the constitutive relations are imposed approximately. We employ discrete exterior calculus for the spatial discretization, use natural crystal structures for three-dimensional meshing, and derive a “discrete Hodge” adapted to harmonic wave. The numerical experiments indicate that the cumulat…