In this paper we investigate the natural convection which exists under the Boussinesq approximation and completely passive boundary conditions. This phenomenon is applicable to the cooling of a heated body and heating and cooling of rooms and buildings and etc. The model equations of momentum and energy are solved by using improved differential transform method. This method is an iterative way for obtaining Taylor series coefficients. The convergence of the Taylor series is obtained by combining the method with the Least Square method for the problem first time here. The combination of these two powerful methods yields semi analytical solutions in the form of a polynomial through a straightforward manner. The efficiency and applicability of the algorithm are assessed and tested and error calculations have been presented.

In this paper we investigate the natural convection which exists under the Boussinesq approximation and completely passive boundary conditions. This phenomenon is applicable to the cooling of a heated body and heating and cooling of rooms and buildings and etc. The model equations of momentum and energy are solved by using improved differential transform method. This method is an iterative way for obtaining Taylor series coefficients. The convergence of the Taylor series is obtained by combining the method with the Least Square method for the problem first time here. The combination of these two powerful methods yields semi analytical solutions in the form of a polynomial through a straightforward manner. The efficiency and applicability of the algorithm are assessed and tested and error calculations have been presented.

In this study elastic stresses and displacements of a rotating variable-thickness disk made of a radially functionally graded (FG) material are calculated numerically in an accurate manner based on the Complementary Functions Method (CFM). The general parabolic function which determines the variation of the thickness of the disk includes concave, convex and linear disk profiles. It is assumed that the inner surface is to be all-metal and the outer surface is to be all-ceramic. Young’s modulus and density vary between inner and outer surface by obeying the volume-fraction material grading rule. The disk is fixed to a shaft at the inner surface and free expansion exists at the outer surface. For the Ti-6Al-4V - Si3N4 metal-ceramic pair, the effect of the inhomogeneity constants on the stress and displacement is investigated. Results are presented in both tabular and graphical forms. Those presented in tables may form benchmark data for purely numerical calculations.

Multiscale functionally graded materials are characterized by possessing a continuous varying distribution of the micro and nano inclusion reinforcement particles through the matrix material. This continuity guarantees a smooth transition of material properties through the spatial domain of the composite and provides a great suitability to achieve specified structural responses. From the manufacturing point of view as well as from the computational perspective, these materials can be thought as effectively having a continuous variation of their properties, or as being constituted by a stacking of different layers, each having constant properties although following the continuous trend variation profile. Due to this ability to tailor the material to be used, and thus to obtain different structural responses, it is important to characterize the relative influence of material and geometrical parameters. These influences are investigated through a detailed parametric study.

Multifunctional materials with different functions can be performed simultaneously or sequentially and developed so as to improve system performance. The best means of producing multifunctional materials are composite materials with the desired properties. Composite materials can be obtained with a combination of multi-phase materials with different characteristics. Each of these phases has the ability to demonstrate a significant portion of the unique features and does not preclude other of a phase function. In this study, an epoxy resin was converted into a multi-functional material as a coating material in military aircrafts. It has the ability to perform multiple functions intended to have radar absorbing and flame retardant properties. Epoxy resin was the matrix of the composite, and huntite/hydromagnesite mineral is added to the composite matrix to achieve flame retardancy. Barium hexaferrite particles were used for radar absorbing property. The powders were produced by sol-gel method. The additive material is determined whether amount-dependent properties of varying the amount. The resulting samples were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Also the flame retardant and radar absorbing properties were investigated. As a result, both materials contribute to fulfill their primary function. Besides, it was concluded that the materials generate beneficial effects together as synergistically.

The disposal of industrial wastes comprises one of the major worldwide environmental problems as these wastes render the environment unfriendly. The growing demand for waste utilization has made solid wastes- like materials from granite processing industry, and sand to be absorbed into the ceramic composition of bricks. The possibility of reduction in production costs provides a strong logic for use of these wastes. In this work, attempt was made to develop acid resistant bricks from quarry fine waste residues (stone dust, kaolin and sand). In order to investigate the possibility of producing acid resistant bricks, nine suggested batches, namely, A1, A2, A3, A4, A5, B1, B2, B3 and B4, were composed for this present study. These mixtures were composed of 40 wt% of Kaolin fine residue with 10-50 wt% of stone dust and silica sand; and 50 wt% of Kaolin fine residue with 10-40 wt% of stone dust and silica sand respectively. The bodies made with the variation of raw materials were sintered at 9700C and their behaviors with respect to apparent porosity, water absorption, bulk density, firing volume changes, compressive strength and acid resistance as a function of temperature, stone dust and sand was studied. It was observed that most of the developed brick samples showed excellent results in both HCl and H2SO4 media in accordance with IS: 4860-1968 and ESS:41-1986.

Tool life affects the cost of the production significantly and it highly depends on shrink fitting conditions of die components in cold forging operations. The tensile strength of stress ring and shrink fitting rate of die insert are the most effective parameters on tool life. In this study, tool life of dies consisting of H13 steel stress ring were compared to dies with carbon fiber composite reinforced stress rings. Initially, two different composite dies were produced using Tenax-E IMS65 E23 24K 830tex and Tenax-J UMS40 F23 24K 800tex S carbon fibers by filament winding method. In order to determine the proper fiber orientation, numerical analysis of cold forging process was carried out on ABAQUS and SIMUFACT finite element softwares. According to numerical results, [90/±45/±15/90]n fiber orientation was chosen for industrial application. It was found that the die made of Tenax-J UMS40 F23 24K 800tex S carbon fiber composite reinforced stress ring has the highest tool life and showed 25% higher tool life compared to conventional steel dies.

In this study, randomly oriented discontinuous chopped glass fiber (E-glass) reinforced cast polyamide (PA6G or castamide) composites were produced by pressure molding method. Two different sample groups were produced with different method. First group was produced under constant pressure at different molding temperature, second one was produced under constant temperature with different pressure. Produced samples friction tests were performed by using a pin-on-disc type friction test machine under dry sliding condition. The performance of the friction tests was carried out different distances and loads. Wear loss of the samples were detected and worn surfaces were investigated with scanning electron microscope (SEM) for determination of the wear mechanism. It was concluded that maximum wear loss was observed at the 300 oC molding temperature in the first group. On the other hand, total wear in second group was decreased with increasing molding pressure according to first group.