Additive Manufacturing enables the production of components with higher geometrical freedom in comparison to conventional technologies and could potentially be exploited to produce cardiovascular stents with new shapes. A new stent mesh for Cobalt Chromium balloon-expandable stents had been specifically designed for Selective Laser Melting production, following the rules suggested to obtain a well-built component. Both unexpanded and expanded stent configurations were designed and produced. In particular, the unexpanded configuration mesh was used to build stents with different combinations of thickness and process parameters, in order to analyse their effect on mechanical properties and internal defects. Tensile specimens with the same thickness values of the stents were produced using the two peak power levels, to perform tensile tests and characterise the mechanical behaviour. Stents and tensile specimens were analysed with scanning electron microscope and micro x-ray computed tomography to evaluate the presence of defects and the geometrical deviation. The stents were expanded by means of a balloon catheter to assess the validity of the design and the trend of the stent diameter with the pressure variation was evaluated.
I processi additivi permettono di produrre componenti con una complessità geometrica superiore rispetto alle tecnologie tradizionali e il loro utilizzo potrebbe essere sfruttato per produrre stent cardiovascolari con nuove geometrie rispetto a quelle attualmente disponibili in commercio. Una nuova mesh per stent in lega cobalto-cromo espandibili con palloncino è stata progettata appositamente per la produzione tramite Selective Laser Melting (fusione laser selettiva), rispettando le regole di progettazione necessarie per produrre componenti di buona qualità. Sono stati progettati e realizzati stent sia in configurazione inespansa che espansa. In particolare, stent in configurazione inespansa sono stati prodotti con diversi valori di spessore e parametri di processo, con l'obiettivo di valutarne l'effetto su proprietà meccaniche e difetti. Sono stati inoltre prodotti provini di trazione con le stesse combinazioni di spessore e parametri degli stent, in modo da poter effettuare prove di trazione per caratterizzare il comportamento meccanico. Gli stent e i provini di trazione sono stati analizzati mediante microscopio a scansione elettronica e micro tomografia computerizzata, per valutare la presenza di difetti e la geometria ottenuta. Infine gli stent sono stati espansi per verificare la validità della mesh ed è stato valutato l'andamento del diametro dello stent al variare della pressione durante l'espansione.
Design and testing of a novel CoCr stent for additive manufacturing by selective laser melting
FINAZZI, VALENTINA
2017/2018
Abstract
Additive Manufacturing enables the production of components with higher geometrical freedom in comparison to conventional technologies and could potentially be exploited to produce cardiovascular stents with new shapes. A new stent mesh for Cobalt Chromium balloon-expandable stents had been specifically designed for Selective Laser Melting production, following the rules suggested to obtain a well-built component. Both unexpanded and expanded stent configurations were designed and produced. In particular, the unexpanded configuration mesh was used to build stents with different combinations of thickness and process parameters, in order to analyse their effect on mechanical properties and internal defects. Tensile specimens with the same thickness values of the stents were produced using the two peak power levels, to perform tensile tests and characterise the mechanical behaviour. Stents and tensile specimens were analysed with scanning electron microscope and micro x-ray computed tomography to evaluate the presence of defects and the geometrical deviation. The stents were expanded by means of a balloon catheter to assess the validity of the design and the trend of the stent diameter with the pressure variation was evaluated.File | Dimensione | Formato | |
---|---|---|---|
Finazzi_Valentina_Final_Thesis.pdf
non accessibile
Descrizione: Testo della tesi
Dimensione
24.14 MB
Formato
Adobe PDF
|
24.14 MB | Adobe PDF | Visualizza/Apri |
I documenti in POLITesi sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
https://hdl.handle.net/10589/142909