A FINITE ELEMENT ANALYSIS OF BURR FORMATION IN FACE MILLING OF A CAST ALUMINUM ALLOY

The research discussed in this article focuses on the effects of tool geometry (i.e., rake angle and cutting edge radius) and flank wear upon burr formation in face milling of a cast aluminum alloy. As to tool edge preparation, the use of a tool with variable cutting edge radius was investigated using FEM, and compared for its cutting performance (i.e., burr reduction and tool life) with a conventional tool with uniform cutting edge radius. In order to evaluate 3D face milling through 2D orthogonal cutting simulations, the cross-sections that consist in the cutting speed direction and chip flow direction were selected at different locations along the tool rounded corner. At these cross-sections, the local value of cutting edge radius and their associated tool rake angles as well as the effective uncut chip thickness were determined for 2D cutting simulations. In addition, 3D face milling simulations were conducted to investigate more realistic chip flow and burr generation. Comparisons were made for burrs produced from 3D simulations with a sharp tool, 3D simulations with a worn tool and face milling experiments. Finally, recommendations for cutting tool design are made to reduce burr formation in face milling.     

SEISMIC EVENTS IN THE UPPER MIOCENE – PLIOCENE SEDIMENTARY SUCCESSION IN THE GULF OF İZMİR (WESTERN ANATOLIA): IMPLICATIONS FOR HYDROCARBON PROSPECTIVITY

An analysis of multi-channel seismic reflection data integrating reflection tomography, pre-stack depth migration, AVO analysis, seismic modelling and seismic attribute analysis was used to investigate the Miocene – Quaternary stratigraphy of the Gulf of İzmir, western Anatolia. In this area, the east-west oriented Gediz graben intersects with the NE-SW oriented Bakırçay Graben. A velocity-depth model together with pre-stack depth migration allowed two seismic stratigraphic units (SSU1 and SSU2) to be distinguished. These units can be correlated with the stratigraphic succession at the offshore Foça-1 well and correspond to the Upper Miocene to Recent Bozköy, Ularca and Bayramiç Formations with a combined thickness of 1.75 km. The units rest on acoustic basement (SSU3) which has a basin-and-ridge morphology, and which corresponds to the Lower-Middle Miocene Yuntdağ Volcanics. A number of lateral velocity variations were identified. In particular, a ~90 m wide and ~500 m long lenticular-shaped low-velocity zone with an interval velocity of 1.68 km/s was identified in the Quaternary Bayramiç Formation. The structure is bounded by negative reflections whose amplitude increases with offset at the top and by strong positive reflections whose amplitude increases with offset at the base, interpreted as possible bright and flat spots respectively. These amplitude events point to the presence of gas-saturated sediments within the study area. The lenticular structure is bounded by strike-slip faults on either side, and by a Miocene – Pliocene unconformity surface below and by shales of the Bayramiç Formations above. It is therefore interpreted as a possible structural – stratigraphic trap. The strike-slip faults may allow the migration of hydrocarbons from source rocks located at greater depths. The presence of a low-velocity zone above the lenticular structure reaching up to seafloor may indicate the upward leakage of hydrocarbons from the trap. These observations will contribute to future hydrocarbon exploration activities in the study area.     

Mechanical and Antibacterial Properties of Injection Molded Polypropylene/TiO2 Nano-Composites:Effects of Surface Modification

Polypropylene (PP)/titanium dioxide (TiO2) nano-composites were prepared by melt compounding with a twin screw extruder. Nanoparticles were modified prior to melt mixing with maleic anhydride grafted styrene-ethylene-butylene-styrene (SEBS-g-MA) and silane. The composites were injection molded and mechanical tests were applied to obtain tensile strength, elastic modulus and impact strength. Antibacterial efficiency test was applied on the injection molded composite plaques by viable cell counting technique. The results showed that the composites including SEBS-g-MA and silane coated TiO2 gave better mechanical properties than the composites without SEBS-g-MA. Antibacterial efficiency of the composites varied according to the dispersion and the concentration of the particles and it was observed that composites at low content of TiO2 showed higher antibacterial property due to the better photocatalytic activity of the particles during UV exposure.     

Three-dimensional analysis and computer simulation of shape rolling by the finite and slab element method

In this study a new simplified 3-D numerical method and the associated computer program have been developed to simulate the shape rolling process. The 2-D rigid-plastic finite element method (FEM), used for the generalized plane-strain condition, is combined with the slab method. This method, called FSEM (finite and slab element method), reduces the computational effort without losing much accuracy obtained in the 3-D computer simulation of the shape rolling process. The FSEM has been used to develop a computer program, called TASKS for three-dimensional analysis of shape-rolling as a kinematically steady-state process. The program TASKS has been used to simulate the metal flow and the bulge profile in flat rolling of slabs, the shape rolling of a simple H section, and the rolling of a practical H-beam section. In flat rolling, predicted spreads agreed well with experimental results, given in the literature. The metal flow in rolling of a simple H section was compared with results of a full 3-D simulation, obtained by other investigators. The comparison indicated that the present predictions give quite good results. Finally, the predictions made for a practical pass, used in rolling H sections, also compared well with experimental data.     

Characterization of composite tiles fabricated from poly(ethylene terephthalate) and micromarble particles reinforced by glass fiber mats

Polyester composite tiles (PCT) are synthesized from PET and fabricated by compression molding using micromarble clusters as filler. Three batches of marble clusters with different size distributions are used to assess the effect of particle size on mechanical properties. In addition, tiles are cured at 40, 60, 80, 100, and 120°C to characterize the dependence of mechanical properties on cure temperature. Tiles prepared using finer marble grades yield consistently higher flexural strength and stiffness values regardless of the cure temperature. The cure temperature does not seem to have an appreciable effect on mechanical properties except for 120°C cure. Samples cured at 120°C registered a sharp drop in mechanical properties. Dynamic mechanical analysis indicates improved material damping when coarse grade marble dust is used. Prospects of improving mechanical properties are explored by reinforcing PC tiles with randomly oriented, discontinuous glass fibers. This is achieved by placing a single layer of glass fiber mat on the top and bottom tile surface. Presence of fiber mats leads to the formation of a graded particle size distribution across the mat thickness when the coarse grade marble dust is used. This distribution resulted in significant improvements in flexural strength, stiffness, and overall toughness of the tiles by enhancing the interfacial region between the glass mats and the PC tile. The mechanism of improvement is elaborated by studying the crack propagation and fracture morphology. POLYM. COMPOS., 33:1921–1932, 2012. © 2012 Society of Plastics Engineers     

Energy efficiency interventions in UK higher education institutions

This paper provides an insight into energy efficiency interventions studies, focusing on issues arising in UK higher education institutions (HEIs) in particular. Based on a review of the context for energy efficiency and carbon reduction programmes in the UK and the trends in higher education sector, existing external and internal policies and initiatives and their relevant issues are extensively discussed. To explore the efficacy of some internal intervention strategies, such as technical, non-technical and management interventions, a survey was conducted among UK higher education institutions between February and April 2008. Consultation responses show that there are a relatively high percentage of institutions (83%) that have embarked on both technical and non-technical initiatives, which is a demonstration to the joined-up approach in such area. Major barriers for intervention studies are also identified, including lack of methodology, non-clarity of energy demand and consumption issues, difficulty in establishing assessment boundaries, problems with regards to indices and their effectiveness and so on. Besides establishing clear targets for carbon reductions within the sector, it is concluded that it is important to develop systems for effectively measuring and evaluating the impact of different policies, regulations and schemes in the future as the first step to explore.     

Optimization of insulation thickness for external walls using different energy-sources

In countries that import most of their energy, like Turkey, energy saving and the effective usage of energy become much more important. Energy consumption for heating is too high in Turkey because buildings have almost no insulation. Also the high prices of heating energy in Turkey, emphasize the need for energy saving. Therefore, the optimum insulation-thickness of the external wall for the five different energy-sources (coal, natural gas, LPG, fuel oil and electricity) and two different insulation materials (expanded polystyrene, rock wool) are calculated for Denizli. The optimization is based on a life-cycle cost analysis. According to the results, the optimum has been obtained by using coal as the energy source and expanded polystyrene as the insulating material. When the optimum insulation-thickness is used the life cycle saving and payback period are 14.09 $/m² and 1.43 years, respectively.     

The effect of the sulfonylurea glyburide on nitric oxide in streptozotocin-induced diabetic rat

1. The interaction between nitric oxide (NO) and superoxide anions has received a great deal of attention. Because NO is rapidly inactivated by superoxide anions, it has been suggested that an enhanced formation of this radical may be involved in the accelerated breakdown of NO. 2. In the present study, we administrated glyburide (glibenclamide) to Streptozotocin-induced diabetic rats and determined the effect of such treatment on serum nitrite+nitrate levels. Serum nitrite+nitrate levels were reduced in diabetic animals (P<0.001). Administration of glyburide to diabetic rats reversed the diabetes-induced changes, suggesting that glyburide may directly increase serum nitrite+nitrate levels.