Fatih GÜNDÜZ 030060144 (11th week)

Notch Sensitivity:

The presence of stress-concentrating notches in a polymer sample has a significant effect on the polymer's impact strength. The sharper the notch, the greater the reduction in impact strength. For an infinitely sharp crack, the theorical stress at the notch tip i,s infinite, and, as a result, failure can occur even under the smallest loading.
It is well known that different polymers have varying degrees of notch sensitivity. The classic example, of course, is that polycarbonate. The impact strength of this high-impact-strength polymer essentially drops to zero as the sharpness of the notch increases.

(Compositional and failure analysis of polymers: a practical approach, J. Scheirs, p.327)


Mechanical Thermoforming:

The mechanical thermoforming uses matching positive and negative molds that are brought together against the heated plastic sheet, forcing it to assume their shape. In pure mechanical forming, air pressure is not used at all. The process is illustrated in Figure13.39, Its advantages are better dimensional control and the opportunity for surface detailing on both sides of the part. The disadvantages is that two mold halves are required; therefore, the molds for the other two methods are less costly.

(Fundamentals of Modern Manufacturing: Materials, Process, and Systems, M.P. Groover, p.305)


Devitrification:

Once the glass is formed, the discussion turns to its devitrification upon a heat treatment. In fact, there have been measurements to determine the rate of growth of crystalline phases in an annealed glass. Once the temperature increases crystal growth may happen whenever the relative nucleation and growth curves overlap or whenever impurities serve as nuclei. Growth rate increase steeply to a maximum and than decrease to zero at liquids temperature. Such as curve is shown for a silicosoda-lime glass when the growth of crystal of composition Na2O-3
CaO-6SiO2 called devitrite is observed. This phenomen is to be avoided when a glass article is heat treated unless a glass ceramic material is to be form a parent glass as detailed in the next section. Additional of a few percent of oxides like MgO or Al2O3 allows for reducing devitrification risks in ordinary oxide glasses (window glass). Also, care must be taken regarding preferential sites for nucleation like surfaces, dust, bubbles or inhomogeneities.

(Glass: mechanics and technology, E.L. Bourhis, p.76)


Material Handling and storage:

There has been impressive progress in automated material handling and storage systems. Material handling systems are used to increase the speed of material movement, weight carried, distance travelled, and ability to deal with a harsh enviroment. This section discusses the major trends in material handling and storage technology.
-Material handling technology: The future developments in material handling aim at better control inventory, improved production felexibility, and fully integrated manufacturing systems.
-Automated Storage Systems: The development in material storage technology are strongly affected by the need to reduce the amount of material to be stored.
-Control systems: The progress in material handling control systems includes refinement of sensors, motor starters, communication links, and other methods for direct machine control as well as advance in hardware and software.

(Computational intelligence in design and manufacturing, A. Kusiak, p.7)