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.     

On determining cluster size of randomly deployed heterogeneous WSNs

Clustering is an efficient method to solve scalability problems and energy consumption challenges. For this reason it is widely exploited in Wireless Sensor Network (WSN) applications. It is very critical to determine the number of required clusterheads and thus the overall cost of WSNs while satisfying the desired level of coverage. Our objective is to study cluster size, i.e., how much a clusterhead together with sensors can cover a region when all the devices in a WSN are deployed randomly. Therefore, it is possible to compute the required number of nodes of each type for given network parameters.     

An optimal and a heuristic algorithm for the single-item retrieval problem in puzzle-based storage systems with multiple escorts

Puzzle-based storage systems consist of densely stored unit loads on a square grid. The problem addressed in this paper is to retrieve a stored unit load from a puzzle-based storage using the minimum number of item moves. While previous research contributed optimal algorithms for only up to two empty locations (escorts), our approach solves configurations where multiple empty locations are arbitrarily positioned in the grid. The problem is formulated as a state space problem and solved to optimality using an exact search algorithm. To reduce the search space, we derive bounds on the number of eligible empty locations and develop several search-guiding estimate functions. Furthermore, we present a heuristic variant of the search algorithm to solve larger problem instances. We evaluate both solution algorithms on a large set of problem instances. Our computational results show that the algorithms clearly outperform existing approaches where they are applicate and solve more general configurations, which could not be solved to optimality before. The heuristic variant efficiently yields high-quality solutions for significantly larger instances of practically relevant size.     

Application of CAD/CAM in precision forming

Computer-aided techniques are being applied increasingly in designing the tools for metal forming operations. In precision forming these applications are becoming even more useful since. In these cases, dies are more stressed than in conventional forming operations. The practical and proven use of computers in forming technology include: CAD/CAM for die making; transfer of geometric data from the customer's CAD/CAM system to that of the supplier, and vice versa; application of artificial intelligence and expert systems for part and process design; simulation of metal flow, prediction and optimization of process variables as well as analysis of stress in dies and prevention of premature die failure.     

The modification of the characteristics of ZnO nanofibers by TCNQ doping content

In this study, the electrical properties of an Al/p-Si metal/semiconductor photodiodes with Tetracyanoquinodimethane–Polyvinyl chloride (TCNQ–PVC) and PVC–TCNQ:ZnO interfacial layers were investigated. Growing of the interfacial layers on p-Si were fulfilled using electrospinning method as a fiber form. Al metallic and ohmic contacts were deposited via physical vapor deposition method. Scanning electron microscopy (SEM) pictures of the devices were captured to examine the morphology of the structure. Within the scope of electrical characterization, I–V measurements of the Al/PVC–TCNQ/p-Si and Al/PVC–TCNQ:ZnO/p-Si devices were accomplished both in the dark and under illumination conditions. Various device parameters, such as ideality factor and barrier height values were determined from I–V characteristics. Although the ideality factor values were obtained as 8.47 and 6.85 for undoped and ZnO-doped Al/PVC–TCNQ/p-Si diodes, the barrier height values were calculated as 0.84 for both devices. When a comparison was made between ZnO doped and undoped Al/PVC–TCNQ/p-Si diodes, it was evaluated that the rectification and photoresponse properties of the heterojunction diode was improved with ZnO dopant.

     

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.     

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.     

A New Hysteretic Behavior in the Electrical Resistivity of Flexinol Shape Memory Alloys Versus Temperature

The electrical resistivity (ER) of Flexinol nickel-titanium shape memory alloys (SMA) has been measured in the range from −15 to 105°C. The investigated Flexinol wires have two diameters, 150 and 375 μm. The experimental results show new temperatures of phase transformation (TTR) evidencing the unexpected presence of the R-phase. The transformations from austenite to martensite, from austenite to R-phase, and vice versa are simultaneous. In the range [20 to 110°C] the hysteresis is almost negligible, whereas in the range [−15 to 105°C] the accommodation process of the hysteresis is observed.     

Simultaneous Determination of Flow Stress and Interface Friction by Finite Element Based Inverse Analysis Technique

A finite element based Inverse analysis technique has been developed to determine the flow stress and friction at the tool/workplace interface simultaneously from one set of material tests. The Inverse problem is aimed at minimizing the error between experimental data and predictions made by rigid-plastic finite element simulations. The ring compression test and the modified limiting dome height test (sheet blank with a hole at center stretched with a hemispherical punch) were selected for evaluating the method for bulk forming and for sheet forming, respectively. The determined flow stress data were compared with corresponding data obtained Independently using the well-lubricated cylinder compression test and hydraulic bulge test. Results show that the method discussed In the study is efficient and accurate.