Cemre Ablay 030060150 6th Week

Viscoelastic Behavior: (18.03.2011-13:10)

Viscoelastic materials are those which exhibit both viscous and elastic characteristics. Viscoelasticity is also known as anelasticity, which is present in systems when undergoing deformation. Viscous materials, like honey, polymer melt etc, resist shear flow (shear flow is in a solid body, the gradient of a shear stress force through the body) and strain, i.e. the deformation of materials caused by stress, is linearly with time a stress is applied.

(Gargallo L., Radić D., Physicochemical Behavior and Supramolecular Organization of Polymers, p.43)



Slotting method: (18.03.2011-13:29)

A slotter is mainly used for internal machining of blind holes or vertical machining of complicated shapes which are difficult to be produced on horizontal shaper. Jobs such as keyway cutting, machining of square holes, cutting of internal or external teeth on bigger gears and machining of dies, straight or curved slots are taken up on this machine.
Main parts of a slotter are base (or bed), column, saddle, cross slide, table and ram and tool --head.

(Kaushish J.P., Manufacturing Processes, Second Edition, p.487-488)


Semi-crystalline Polymers: (18.03.2011-13:44)

Unlike amorphous polymers, semicrystalline polymers have some regions where the polymer chains are arranged in specific spatial patterns relative to the other polymer chains within their polymer matrix. Segments of polymer backbones, from either adjacent polymer molecules or within the same polymer molecule (polymer chain folded back on itself) are aligned in an orderly manner with the exact same spatial arrangement and inter-or intramolecular distance from one set group of atoms to the next. Semicrystalline polymers contain both amorphous and crystalline regions within the same polymer matrix.

(Giles H.F. et al, Extrusion: The Definitive Processing Guide and Handbook, p.181)


Kelvin Model: (18.03.2011-15:01)

A purely viscous damper and a purely elastic spring connected in parallel form the basic unit of the Kelvin model. Several Kelvin models connected in series or parallel result in the generalized Kelvin model. The strain contribution of the i th element of the generalized Kelvin model resulting in a series combination of several Kelvin models is
ε_i=1/(Dη_i+k_i )

where D is the differential operator with respect to time, k_i and η_i are the spring constant and dashpot constant respectively.
(Das B.M., Geotechnical Engineering Handbook, p.4-9)