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1.
Computer modelling of the residual limb for the development of prosthetic sockets and liners with the cellular structure : doctoral disertation
Vasja Plesec, 2023, doktorska disertacija

Opis: The production of lower limb prostheses continues to rely primarily on manual methods, which are outdated and characterized by labour-intensive processes, lengthy time requirements, high costs, and a heavy reliance on the expertise of prosthetists. Achieving a satisfactory fit between the residual limb and socket remains a challenge, often leading to discomfort, pain, and potential wearer tissue damage. However, advancements in computer technology and numerical simulation offer an opportunity to predict stresses and strains experienced by the residual limb during prosthesis usage. This, in turn, aids in the development process by enhancing the design of the prosthetic socket and liner through virtual environments. In this dissertation we developed a generic numerical transtibial model to bridge the gap between clinical practice and numerical simulations. Biomechanically validated, this model generates outcomes applicable to a broader amputee population, facilitating comparative analysis of socket and liner designs and materials under different loading conditions. Furthermore, the dissertation explores the utilization of a 3D-printed socket manufactured through the cost-effective fused filament fabrication process, using polylactic acid filament, aiming to reduce the costs and establish a streamlined production process. The 3D-printed socket was evaluated within the virtual environment using the developed transtibial model. The numerical findings indicate that the 3D-printed socket can effectively withstand the loads encountered during the stages of prosthesis donning, single-leg stance, heel strike, and push-off, thereby presenting a viable alternative to the prevalent composite socket. Additionally, a cellular structure composed of a flexible thermoplastic elastomeric material is proposed as a prosthetic liner to enhance comfort by reducing contact pressure while maintaining the required stability. Numerical results indicate that by manipulating cellular parameters such as unit cell type and relative density of the structure, a customized response can be achieved. This customized response effectively reduces contact pressure for a given scenario without increasing displacement, thereby improving comfort while maintaining stability.
Ključne besede: lower-limb prosthesis, generic numerical transtibial model, 3D-printed socket, cellular structure liner, finite element method
Objavljeno v DKUM: 14.11.2023; Ogledov: 387; Prenosov: 17
.pdf Celotno besedilo (3,64 MB)

2.
Development, fabrication and mechanical characterisation of auxetic bicycle handlebar grip
Nejc Novak, Vasja Plesec, Gregor Harih, Andrej Cupar, Jasmin Kaljun, Matej Vesenjak, 2023, izvirni znanstveni članek

Opis: The auxetic cellular structures are one of the most promising metamaterials for vibration damping and crash absorption applications. Therefore, their use in the bicycle handlebar grip was studied in this work. A preliminary computational design study was performed using various auxetic and non-auxetic geometries under four load cases, which can typically appear. The most representative geometries were then selected and fabricated using additive manufacturing. These geometries were then experimentally tested to validate the discrete and homogenised computational models. The homogenised computational model was then used to analyse the biomechanical behaviour of the handlebar grip. It was observed that handle grip made from auxetic cellular metamaterials reduce the high contact pressures, provide similar stability and hereby improve the handlebar ergonomics.
Ključne besede: auxetic cellular structures, computational simulations, experimental testing
Objavljeno v DKUM: 23.05.2023; Ogledov: 229; Prenosov: 33
.pdf Celotno besedilo (2,63 MB)

3.
Numerična simulacija trka pri pristanku letala z možnostjo navpičnega vzletanja in pristajanja : magistrsko delo
Vasja Plesec, 2019, magistrsko delo

Opis: V magistrski nalogi so predstavljena priporočila za snovanje varnega letala odpornega na vertikalni trk. Sestavo letala smo razdelili na tri glavne komponente namenjene absorpciji energije v primeru vertikalnega trka: sedež, struktura trupa in podvozje. Za vsak del posebej je bila izvedena eksplicitna časovno odvisna numerična simulacija v programskem paketu Abaqus/Explicit. Iz dobljenih rezultatov smo med seboj primerjali pospeške, ki delujejo na telo potnika ter sile in pomike strukturnih delov, iz katerih se vidi količina absorbirane energije. Na koncu smo izvedli še računalniško simulacijo sestave generičnega letala, ki je vsebovalo vse zgoraj naštete komponente.
Ključne besede: vertikalni trk letala, eksplicitne numerične simulacije, absorpcija energije, metoda končnih elementov, deformacijska struktura
Objavljeno v DKUM: 06.05.2019; Ogledov: 1274; Prenosov: 142
.pdf Celotno besedilo (5,98 MB)

4.
Dimenzioniranje robotskega prijemala za zlaganje baterijskih celic
Vasja Plesec, 2015, diplomsko delo

Opis: Dandanes si le s težavo predstavljamo industrijo brez robotov. Uporabljajo se za skoraj vsa opravila. Najkompleksnejši element robota je po navadi prav prijemalo, ki je zadolženo za opravljanje specifične naloge. V diplomski nalogi sem na dejanskem primeru opisal razvoj in nastajanje prijemala za industrijsko robotsko roko. V prvem delu je na kratko predstavljeno nekaj o industrijskih robotih ter robotskih prijemalih. V drugem delu pa sem se posvetil razvoju prijemala, od načrtovanja pa vse do razdelave. Opravil sem tudi trdnostne preračune za potrebne dele. Celotni postopek razvoja sem poskušal jasno prikazati tudi s pomočjo slik.
Ključne besede: robotska celica, robotska roka, robotsko prijemalo, vakuumski prijem, linearni mehanski prijem in baterijska celica.
Objavljeno v DKUM: 27.10.2015; Ogledov: 1231; Prenosov: 132
.pdf Celotno besedilo (5,17 MB)

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