Archives—November 2011

A Walk down the Memory Lane with Magneto Rheological Technology for Vehicle Applications

Thursday November 17, 2011 4:00-5:00 p.m.
ME-EM building, Room 112

Mehdi Ahmadian
Professor and Director, Center for Vehicle Systems & Safety, Virginia Tech Dept. of Mechanical Engineering

Magneto rheological (MR) fluids consist of a carrier fluid and micron-sized ferrous particles that when subjected to a magnetic field enables the fluid to have a varying yield stress, dependant on the magnetic flux density. This presentation will provide a historical review of MR fluids for vehicle suspensions. It also provides the current state of MR devices as well as a perspective on the future direction of MR technology for vehicle applications. Some of the successes of the MR devices are discussed along with some of their challenges. It is noted that although our understanding of the MR fluids in valve and shear mode is reasonably advanced, their behavior in squeeze mode remains relatively unknown. The results of a preliminary study show that in squeeze mode MR fluids can provide a large range of forces that can be controlled with a relatively low amount of electrical power, making them suitable for compact force actuators that can be used in aerospace, automotive, robotics, and biomedical devices.


Product Assembly: Quality, Productivity and Customization

Thursday November 10, 2011 4:00-5:00 p.m.
ME-EM building, Room 112

S. Jack Hu, Ph.D.
Associate Dean – Academic Affairs, College of Engineering, G Lawton and Louise G Johnson Professor, Engineering, University of Michigan

Assembly is the capstone process for product realization where component parts and subassemblies are integrated together to form the final products. As product variety increases due to the shift from mass production to mass customization, assembly systems must be designed and operated to handle such high variety while maintaining performance in quality and productivity. In this presentation we will first review the state of the art research in the areas of assembly system design, planning and operations in the presence of product variety. Methods for assembly sequence generation, system configuration design and assembly line balancing are presented and summarized. Operational complexity in assembly systems are then discussed in the context of product variety. Finally we conjecture a future manufacturing paradigm of personalized products and production and discuss the assembly challenge for such a paradigm.



Dynamics of Hydrophobically Modified Hydrogels

Thursday November 3, 2011 4:00-5:00 p.m.
ME-EM building, Room 112

Professor Robert A. Weiss
Department Chair and Hezzleton E. Simmons Professor of Polymer Engineering, University of Akron’s College of Polymer Science and Polymer Engineering

Physical gels can be formed by interchain associations involving electrostatic interactions, hydrophobic interactions, hydrogen bonding or crystallizing segments. Because of the reversibility of these intermolecular interactions and the ability to rapidly respond to external stimuli such as temperature, pH or salt concentration, physical hydrogels can have much different properties than crosslinked gels. We are studying the viscoelastic and mechanical behavior of physically crosslinked copolymer hydrogels synthesized from N, N-dimethylacrylamide (DMA) and 2-(N-ethylperfluorooctane sulfonamido) ethyl acrylate (FOSA), with varying FOSA concentration. The strong hydrophobic association of the FOSA moieties in an aqueous environment produced microphase separation of core-shell FOSA nanodomains (diameter ~2-6 nm) that provided physical crosslinks.

This talk will discuss the rheological behavior of the PDMA-FOSA hydrogels. The swollen gels exhibited excellent mechanical properties: modulus was 80-130 kPa, elongation at break was 1000-1600 % and the tensile strength was ~500 kPa, depending on the FOSA concentration. The physical PDMA-FOSA hydrogels were much more efficient at dissipating stress than the chemical hydrogels, which resulted in much higher strength and toughness, 4-6 MPa. That result was attributed to the extra energy dissipation mechanism provided by the reversible, hydrophobic crosslinks.