1,721,144 research outputs found
Numerical Solution of Plane Elasticity Problems with the Cell Method
No full textAbstract The aim of this paper is to present a methodology for solving the plane elasticity problem using the Cell Method. It is shown that with the use of a parabolic interpolation in a vectorial problem, a convergence rate of 3.5 is obtained. Such a convergence rate compares with, or is even better than, the one obtained with FEM with the same interpolation – depending on the integration technique used by the FEM application. The accuracy of the solution is also comparable or better
Elastodynamics with the Cell Metod
No full textThe Cell Method is a recently developed numerical method that is giving interesting results in several fields of physics and engineering. In this paper, first a brief description of the method for elasticity problems is given and successively the elastodynamics formulation is derived. The method leads to an explicit solution system, combining the advantages of a diagonal mass matrix and the possibility of using unstructured meshes.
The convergence rate has been tested in reference to the problem of free harmonic vibrations in a system with one degree of freedom, showing that the Cell Method has the same convergence rate of II order Runge Kutta method, but its accuracy is better. The Cell Method results in 2D and 3D have been compared with those obtained with the commercial codes ANSYS and ABAQUS in the problem of the longitudinal vibration of a bar with free ends, for which the exact analytic solution is found in literature. The Cell Method results are comparable with or better than those obtained with FEM, and they are particularly interesting from the point of view of computation time and memory requirements for very large meshes
Morphology-based prediction of elastic properties of trabecular bone samples
No full textMorphological characteristics of the trabecular structure, identified by micro-tomography, can be quantified by volume fraction and
second-order fabric tensors. These parameters have been proved to be related to bone structural properties but the formulations so far
developed between volume fraction, fabric and elastic properties are bone specific and the coefficients found for one bone are not directly
applicable to other bones. In this work, a general relationship was determined that links volume fraction and Mean Intercept
Length (MIL) to the trabecular structure stiffness as computed by means of numerical models on which compression tests are simulated.
Preliminary results obtained for three pig and two rat bone structures show that, for the pooled data set, the model could predict approximately
99% of the variation of the numerically computed elastic moduli
Method to identify the mechanical properties of a material/ Procedimento per identificare le proprietà meccaniche di un materiale
No full textThe present invention concerns a method to identify the mechanical properties of a material, such as
for example a bone material, starting from at least a digitalized image of a sample of said material.
The image of the sample to be analyzed is processed to achieve a numerical model comprising a
determinate number of elementary geometric elements, hereafter called cells, to each of which a
parameter to identify the type of material is assigned, in order to obtain information on the
distribution of the mechanical characteristics in the individual units of the sample, from which it is possible to trace both the elastic characteristics and hence the resistance, and also the distribution of
stresses and strain in relation to the application of the loads.
The method according to the present invention can easily be implemented in any processor, whether
it be an electronic processor or the processor inside a machine, for example a machine for digital
radiography. The processor can be used directly by a medical operator for the accurate diagnosis of
the bone properties, or to evaluate the validity of a prosthesis implanted in a patient, for example, by
means of determining the flow lines of a load or quantifying the state of stress and/or strain
Dispense del corso di Costruzione di Macchine e Affidabilità
No full textDispense del corso di Costruzione di Macchine e Affidabilita
Dynamics analysis of mechanical components: a discrete model for damping
No full textThe Cell Method is a recent numerical method that can be applied in several fields of physics and engineering. In this paper, the elastodynamics formulation is extended to include system internal damping, highlighting some interesting characteristics of the method. The developed formulation leads to an explicit solving system. The mass matrix is diagonal (without lumping) and in the most general case a time-dependent damping coefficient can be defined for each node.
Accuracy and convergence rate have been tested with reference to the classical problem of a particle free vibration with viscous damping.
An application to mechanical components analysis has been included in order to illustrate the potentialities of the method for fatigue behaviour assessment of mechanical parts
Elasto-Plasticità col metodo delle celle
No full textScopo di questo lavoro è presentare delle applicazioni del Metodo delle Celle nel campo della
meccanica dei solidi.
Dopo aver introdotto il CM, viene dapprima presentata un’applicazione del Metodo delle Celle per
la modellazione delle caratteristiche meccaniche in campo lineare di materiali porosi, quali i sinterizzati.
Successivamente viene adottato il criterio di von Mises e vengono sviluppate le relazioni per la
soluzione di problemi elastici non lineari. I risultati ottenuti con il CM vengono confrontati con quelli
teorici. Viene discusso l’ordine di convergenza della soluzione in problemi non lineari
Elastodynamics wih the Cell Method
No full textAbstract The Cell Method is a recently developed numerical method that is giving interesting results in several fields of physics and engineering. In this paper, first a brief description of the method for elasticity problems is given and successively the elastodynamics formulation is derived. The method leads to an explicit solution system, combining the advantages of a diagonal mass matrix and the possibility of using unstructured meshes.
The convergence rate has been tested in reference to the problem of free harmonic vibrations in a system with one degree of freedom, showing that the Cell Method has the same convergence rate of II order Runge Kutta method, but its accuracy is better. The Cell Method results in 2D and 3D have been compared with those obtained with the commercial codes ANSYS and ABAQUS in the problem of the longitudinal vibration of a bar with free ends, for which the exact analytic solution is found in literature. The Cell Method results are comparable with or better than those obtained with FEM, and they are particularly interesting from the point of view of computation time and memory requirements for very large meshes
Morphological and numerical characterization of a PA6-GF 30 sample
No full textMorphological and numerical characterization of a PA6-GF 30 sampl
Stima delle proprietà meccaniche effettive di un solido 2D con il Metodo delle Celle
No full textNel lavoro viene presentato un modello discreto che consente la stima dell’effetto che
una distribuzione random di micro-cricche, modellate mediante celle vuote triangolari
all’interno di una matrice di celle del materiale costituente, ha sulle proprietà strutturali.
Sul solido bidimensionale così modellato è possibile simulare una prova meccanica,
assumendo in ingresso le proprietà meccaniche del materiale costituente, note, ed
ottenendo in uscita la risposta del materiale danneggiato. Il modello proposto può essere
risolto mediante il Metodo delle Celle, metodo numerico di recente sviluppo che
consente una formulazione diretta discreta delle equazioni di equilibrio e risulta quindi
particolarmente adatto nella trattazione di problemi in cui sono presenti eterogeneità o
comunque discontinuità. Vengono prese in considerazione sia le eterogeneità della
struttura sia le concentrazioni di sforzo. Nel lavoro vengono richiamati alcuni aspetti del
Metodo delle Celle, dapprima in campo elastico, e successivamente assumendo per il
costituente un comportamento elastico-perfettamente plastico. Vengono presentati i
risultati di diverse simulazioni, che indicano come il modello proposto possa essere
vantaggiosamente impiegato per la determinazione del comportamento strutturale di un
solido in cui sia presente una distribuzione casuale di micro-cricche
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