A simulation study of multiple-load-carrying automated guided vehicles in a flexible manufacturing system

Although the technology exists for more advanced applications of automated guided vehicles in flexible manufacturing systems, the current employment of these vehicles in material handling generally subscribes to a simple mode of operation : single-load-carrying capacity for each vehicle and unidirectional traffic on each route of the system. Through a simulation programme, this study investigates the effect of several key factors related to the automated guided vehicles on the overall performance of a flexible manufacturing system. These are the number of pallets allowed in the system, the number of vehicles used and the carrying capacity of each and the input and output queue capacities of the machining stations; finally bidirectional traffic is allowed in some routes. The results show that there is a strong interaction among these factors and reveal their combined effects on the throughput from a small flexible manufacturing system. Upon the user's request, the simulation program also provides the animated colour graphics of the system to view developments concurrently under the selected decision values through time.     

Sintering of Monosized, Spherical Yttria Powders

Monosized, spherical Y₂O₃ was processed from raw commercial Y₂O₃ by homogeneous precipitation in aqueous solution via urea decomposition. Dry-pressed pellets of the synthesized and raw powders were sintered to 1500°, 1600°, and 1700°C for 7 to 720 min. Microstructural development was followed with scanning electron microscopy. The differences between sintering behavior of the two powders are discussed.     

Effect of Forming and Aging Atmospheres on E-Glass Strength

E-glass fibers were drawn in various atmospheres. The specific surface area measured by water vapor adsorption was larger than the geometric area. Specific surface increases with the square root of drawing gas pressure. Exposure of glass fibers to ambient atmosphere decreases the strength and increases the area of macropores (r_p> 100 Å). The reciprocal strength of E-glass filaments aged at ambient humidity for various times is proportional to the square root of macro pore area. This relation is independent of the drawing atmosphere, at least for water and tetrafluoromethane.