| Τύπος: |
Παρουσίαση |
| Ημ/νία Έναρξης: |
18/2/2016 |
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| Ώρα Έναρξης: |
13:00 |
| Ώρα Λήξης: |
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| Ομιλητής: |
Νικόλας Πολυχρονόπουλος |
| Τίτλος: |
Δημόσια υποστήριξη της διδακτορικής διατριβής του Νικόλα Πολυχρονόπουλου, (ΜΔΕ Παν/μιο Θεσσαλίας) |
| Περιγραφή: |
Προσκαλούμε τα μέλη ΔΕΠ, τους μεταπτυχιακούς και τους προπτυχιακούς φοιτητές και κάθε ενδιαφερόμενο, στη δημόσια υποστήριξη της Διδακτορικής Διατριβής του κ. Νικόλα Πολυχρονόπουλου με τίτλο:
Variable Cross-Section Flows in Polymer and Composites Processing
Πέμπτη 18 Φεβρουαρίου 2016, ώρα 13.00
Αίθουσα Τηλεδιάσκεψης Τμήματος Χωροταξίας (2ος Όροφος), Πεδίον Άρεως, Βόλος
Περίληψη
The present thesis is aimed at elucidating a number of problems encountered in the production of sheet, film and tape made from polymers and their composites. These problems share the common feature of flow in a variable cross-section. Fully 3D numerical simulation of calendering revealed that the spreading of the sheet, passing through two counter rotating rolls is influenced by the entrance width and thickness of the sheet at the feed section as well as the sheet feeding speed. The lateral spreading of the sheet is accomplished via a spiral motion of the fluid towards the sides. Examination of this flow field reveals a remarkable material rearrangement from the feeding section to the exit. For the film casting process a numerical solution of the conservation of mass and momentum equations using the linear Phan Thien-Tanner (PTT) constitutive equation was performed. It was determined that the maximum swelling at the die exit due to viscoelasticity, rapidly decreases as the drawing speed increases. For understanding the pin-assisted pultrusion process, the fluid penetration dynamics of a porous substrate was analysed computationally. It was determined that the fluid penetration depth of a permeable composite tape/web pulled over a single non-rotating pin (cylinder) is pressure induced and influenced by a large number of material and process parameters (e.g. pin radius, pulling speed, fluid viscosity and tape/web permeability). A simple scaling analysis based on the fluid flow through the permeable tape and through the gap, indicates that all the important parameters of the process may be expressed in a single dimensionless number which exhibits a power-law type dependence on the penetration depth. Using this dependence for studying a sequential cylinder arrangement, results were obtained, which are in good agreement when compared with the limited number of earlier experimental studies. Motivated by the fluid penetration results for the pin-assisted pultrusion process, a generalized study was carried out, for the description of the fluid penetration depth to a permeable and deformable web moving past a rigid stationary cylinder. The results indicate that the web has the tendency to move away from the cylinder as it approaches it and comes closer as it leaves. This behavior leads to a maximum penetration depth under specific deformability and permeability conditions. These results are useful for engineering design and optimization purposes for tape or web production and for other related processes such as coating, rolling and printing.
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| Χώρος: |
Αίθουσα Τηλεδιάσκεψης Τμήματος Χωροταξίας |
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