Applied Engineering Letters

121-124

Authors: H.B. Kaybal, H. Ulus, O. Demir, A.C. Tatar, A. Avcı

In this study, dispersion of nano SiO2 and its effect on mechanical properties were studied by preparing epoxy nanocomposites. Ultrasonic and mechanical mixes were used to disperse the SiO2 nanoparticles in to the epoxy resin. Having been produced with five different weight percentage ratios of SiO2, nanocomposites fracture surfaces were characterized by Scanning Electron Microscopy, optical microscope on tensile tests and bending tests. The results of experimental tests showed that the optimum values of strength for both test were acquired for (2 wt. %) of nano SiO2 epoxy nanocomposites. Scanning Electron Microscopy and optical microscopy analysis techniques were used to understand the toughening mechanisms of the nanocomposites.

130-138

Authors: D. Lukić, M. Milošević, J. Vukman, M. Đurđev, A. Antić

Optimization of process planning belongs to the group of combinatorial optimization problems which at the macro and micro level consists of the selection of machining operations, definition of sequences of machining operations and their grouping into processes, selection of manufacturing resources, machining parameters and strategies. The objective function used for evaluating process plans is mostly defined by manufacturing cost, manufacturing time, surface quality and surface accuracy. The main goal of this research refers to the process planning and optimization of manufacturing time by applying precedence relationships among machining operations, as well as the simulation technique within the CAD/CAM system. The precedence relationships are defined on the basis of dimensional, geometric, technological and economical precedence constraints. Based on these rules, precedence matrices for determining operation sequence for the given shaft part are formed, and afterwards, machining operations are grouped into appropriate processes. For the given rational variants of process plans, a simulation of machining process is performed within the Catia software system. The obtained output is the best variant of process plan for the shaft part on the basis of manufacturing time as the adopted objective function.

144-148

Authors: M. Miletić, I Miletić

With lean methodology usage being the only way to stay competitive on nowadays market, it is important to implement it and spread it through the organization. In this paper, purpose of lean is explained, the most important definition and tools are given and differences between problem solving approaches are explained. It can be concluded that problem solving approaches are in first look different, having also different number of steps, but they are adapted to the company in which they are used and that they depend on the size, complexity and expected closing time of project.