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Mechanical Engineering Seminar by Mohammed Shonar and Ali Nosrati

When: Tuesday, December 5, 2023
2:00 PM - 3:00 PM
Where: > See description for location
Description: Mechanical Engineering (MNE) SEMINAR

DATE:
December 5, 2023

TIME:
2pm-3pm

LOCATION:
Science and Engineering (SENG), Room 110
and on Zoom
https://umassd.zoom.us/j/91640406955?pwd=eklBZWVDOXVDa2VwUFMra1kwNWhjdz09
(Contact hling1@umassd.edu or scunha@umassd.edu for the Passcode)
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SPEAKER #1:
Mohammed Shonar, MS in Mechanical Engineering
(Advisor: Dr. Vijaya Chalivendra)

TOPIC:
Mode-I Fracture Characterization of Polyacrylamide-Amylopectin Single Network Hydrogel with Chitosan Interfacial Reinforcement

ABSTRACT:
Hydrogels are soft and water-rich polymer networks with tunable adhesive properties, that are extensively utilized in the biomedical field. Due to their bonding characteristics, certain hydrogel networks can adhere to a variety of surfaces, including skin tissue. In this study, single network hydrogels composed of Polyacrylamide and Amylopectin were photocured into adherents of T-shaped cross-sections and then bonded together to form 50mm long specimens. The interface of the adherents is reinforced with 200 µL chitosan solution consisting of average molecular weights of 1.5 kDa, 15 kDa, 250 kDa, 343 kDa, and a control group with no chitosan solution. The study investigates the effect of different chitosan molecular weights and pH levels (ranging from 2.5 to 4.5) on the mode-I fracture toughness. The mode-I fracture initiation toughness is evaluated using nonlinear J-integral fracture mechanics. It was observed that the chitosan with the highest molecular weight and pH level resulted in a 200% increase in fracture toughness compared to no chitosan reinforcement, which is attributed to crack tip blunting phenomena. These results are supplemented with analysis by Digital Image Correlation (DIC), which is utilized to compare the strain distribution at fracture initiation.

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SPEAKER #2:
Ali Nosrati, MS in Mechanical Engineering
(Advisors: Dr. Hangjian Ling, Dr. Mehdi Raessi)

TOPIC:
Impact of Undersaturation Level on the Longevity of Super-Hydrophobic Surfaces in Stationary Liquids

ABSTRACT:
Although the longevity of super-hydrophobic surface (SHS) induced by diffusive gas transfer has been extensively studied, the scaling relation between SHS longevity and undersaturation level of the liquid is still an open question. In this study, we address this question by performing experiments where the plastron decay is visualized by a non-intrusive optical technique based on light reflection, the gas diffusion is introduced by using liquid with low dissolved gas concentrations, and the SHS longevity is measured based on the status of gas on the entire surface. We find that the SHS longevity (tf) follows a scaling relation: tf ~ (1−s)−2, where s is the ratio of gas concentration in liquid to that in the plastron. This scaling relation implies that as the gas is dissolving into the liquid, mass flux J reduces with time as: J~t−0.5. Furthermore, we find that the diffusion length LD reduces as the undersaturation level increases, following the scaling relation of LD ~ (1−s)−1. Lastly, we show that a SHS with a greater texture depth has a longer longevity and a larger LD. Our results provide a better understanding of SHS longevity in undersaturated liquid.

For more information please contact Dr. Hangjian Ling, MNE Seminar Coordinator (hling1@umassd.edu).

All are welcome.

Students taking MNE-500 are ENCOURAGED to attend!

All other MNE students are invited to attend.

EAS students are invited to attend.
Topical Areas: Faculty, General Public, Staff and Administrators, Students, Students, Graduate, Students, Undergraduate, University Community, College of Engineering, Mechanical Engineering, Lectures and Seminars