Study of an ankle prosthesis for children: adaptation of ISO 10328 and experimental tests

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Design of an ankle prosthesis for swimming and walking

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The inverse problem of determining the filtration function and permeability reduction in flow of water with particles in porous media

The original publication can be found at www.springerlink.comDeep bed filtration of particle suspensions in porous media occurs during water injection into oil reservoirs, drilling fluid invasion of reservoir production zones, fines migration in oil fields, industrial filtering, bacteria, viruses or contaminants transport in groundwater etc. The basic features of the process are particle capture by the porous medium and consequent permeability reduction. Models for deep bed filtration contain two quantities that represent rock and fluid properties: the filtration function, which is the fraction of particles captured per unit particle path length, and formation damage function, which is the ratio between reduced and initial permeabilities. These quantities cannot be measured directly in the laboratory or in the field; therefore, they must be calculated indirectly by solving inverse problems. The practical petroleum and environmental engineering purpose is to predict injectivity loss and particle penetration depth around wells. Reliable prediction requires precise knowledge of these two coefficients. In this work we determine these quantities from pressure drop and effluent concentration histories measured in one-dimensional laboratory experiments. The recovery method consists of optimizing deviation functionals in appropriate subdomains; if necessary, a Tikhonov regularization term is added to the functional. The filtration function is recovered by optimizing a non-linear functional with box constraints; this functional involves the effluent concentration history. The permeability reduction is recovered likewise, taking into account the filtration function already found, and the functional involves the pressure drop history. In both cases, the functionals are derived from least square formulations of the deviation between experimental data and quantities predicted by the model.Alvarez, A. C., Hime, G., Marchesin, D., Bedrikovetski, P

STUDIO DI UNA PROTESI TRANSTIBIALE PER BAMBINI

In questo lavoro viene presentato uno studio sperimentale e numerico di una protesi di caviglia per amputati transtibiali, per bambini di età fino a 12 anni. In letteratura, le norme disponibili per la conformità delle protesi sono tutte relative ad amputati adulti, mentre solo pochi studi sono presenti riguardanti i bambini. Nel lavoro si introduce, quindi, il problema della modifica della norma in termini di carichi e posizionamento dei punti di applicazione delle forze, e si discute la possibilità di adeguare i dati disponibili al caso in oggetto, un ragazzo di 12 anni e 45 kg. Le prove sperimentali sono eseguite attraverso una schematizzazione dei carichi in gioco durante la camminata e con una attrezzatura progettata appositamente. Le prove sono di tre tipi: statiche (secondo i livelli proof e ultimate), di fatica e di torsione statica. Ogni prova è stata ripetuta su due differenti campioni: i risultati sono positivi e la caviglia prostetica ha potuto essere dichiarata conforme per l’applicazione sui pazienti. Infine, per poter procedere in futuro ad un’ottimizzazione della geometria e dei materiali della caviglia e dei suoi sottocomponenti, si propone un modello numerico che simula il comportamento del piede protesico e della caviglia stessa. Il modello viene validato in base ai dati sperimentali delle prov

STUDIO SPERIMENTALE E NUMERICO DI PROTESI TRANSTIBIALI PER BAMBINI

Oggetto del lavoro è una protesi meccanica di caviglia per amputati transtibiali di età fino a 12 anni. Lo studio si divide in due parti: una legata all’affidabilità delle protesi verificata con prove sperimentali sul dispositivo, ed una numerica di sviluppo del progetto e confronto in diversi assetti. Le prove sperimentali sono eseguite attraverso una schematizzazione dei carichi in gioco durante la camminata e con una attrezzatura progettata appositamente. Le prove sono di quattro tipi: statiche, cicliche, statiche a rottura e statiche di torsione. Ogni prova è stata ripetuta su due differenti campioni: i risultati sono positivi e la caviglia prostetica ha potuto essere dichiarata conforme per l’applicazione sui pazienti. In parallelo si è sviluppato e validato in termini di spostamenti e deformazioni un modello numerico, utilizzato per l’analisi delle zone più sollecitate e per analizzare soluzioni alternative progettuali e costruttive

Optimization Studies of Trans-tibial Prostheses: Numerical Models and Experimental Tests

This paper describes the work done at the Department of Mechanics in collaboration with INAIL, on a particular type of transtibial prosthesis. The discussed topics are different: firstly, an adaptable test bench was designed, in accordance with the standard, to run static strength and fatigue tests on the transtibial prostheses. By means this equipment, it is possible to perform tests on the prosthesis and on its individual components. After the description of some static tests, the prosthesis is also analysed by numerical finite element (FE) simulations, performing structural analyses and simulating the experimental tests carried out using the bench. The numerical results of strains and displacements are compared with the corresponding experimental values measured on the prosthesis. The comparison allows validating the numerical models, which become a reliable and secure tool to perform optimizations varying the geometry and materials of the prosthesis

A method for the verification of structural integrity of lower limbs prostheses

In this study an experimental device for testing the structural integrity of lower limb (transtibial and transfemoral) prostheses is proposed and studied, in accordance with the ISO 10328 Standard. Aim of the development of this device is to mechanically test these kinds of prostheses, for claiming the compliance with the standard. In the first part of the paper, experimental setup of the laboratory is described for the different kinds of prescribed tests. In the second part, the test case of a transtibial prosthesis for children is proposed. After verifying the compliance with the standard of the studied prosthesis, values recorded during the test (i.e. strains or displacements) are used to validate a FE model of the component. The FE model represents a powerful tool to customize the prosthesis to fit the patient's requirements from the design phase and/or to check the possibility of optimizing it in terms of costs