Muzaffer Topcu

Stress Analysis of Curvilinearly Orthotropic Rotating Discs under Mechanical and Thermal Loading

This study deals with the thermal stress analysis of a curvilinearly orthotropic rotating annular disc under internal and external pressures. The temperature distribution is chosen to vary parabolically from the inner surface to the outer surface along the radial section. With an increasing temperature, the tangential stress component decreases at the inner surface whereas it increases at the outer surface, and the radial stress component goes down gradually. The magnitude of the tangential stress component is higher than that of the radial stress component. The radial displacement is calculated analytically and has higher values at the inner surface than that of the outer surface, for all the temperature distributions. The stresses and the radial displacement obtained are also compared with the stresses and displacement in a rectilinearly hollow rotating disc of [Çallioğlu, H., Stress Analysis of an Orthotropic Rotating Disc under Thermal Loading, J. Reinforced Plastics and Composites, (in press)].

Free Vibration Analysis of the Laminated Composite Beams by Using DQM

In this study, the effects of stacking sequences of composite laminated beams on natural frequencies are investigated using the differential quadrature method (DQM). DQM is an efficient discretization technique for obtaining accurate numerical solutions to initial and/or boundary value problems using a considerably small number of grid points. In this way, a theoretical DQM model for the laminated composite beam has been developed. Some of the results obtained from DQM are compared with the results obtained experimentally. Then, these results are compared with the numerical and experimental results available in the literature. It has been seen that all of the results considered are very close to each other. It has also been concluded that the effective stiffness of the laminated composite beam can be altered through a change in the stacking sequence. This allows tailoring of the material to achieve desired natural frequencies and respective mode shapes without changing its geometry drastically or without increasing its weight.

Vibration Analysis of Multiple Delaminated Composite Beams

Abstract In this study, the effects of location, size and number of delaminations, boundary conditions, orientation angles and stacking sequences on the natural frequency of laminated composite beams are investigated experimentally, analytically and numerically. Two-dimensional finite element models of the delaminated beams are obtained using ANSYS (Finite ElementMethod Code). The analytical method is developed using Euler–Bernoulli beam theory. Then, analytical results are compared with the results available in the literature and the numerical and experimental results in the present study. It has been seen that all results obtained are very close to each other. It is shown that the natural frequencies decrease when sizes and numbers of edge and middle delaminations in the beam increase, and the location of the delamination is also very important.The first natural frequency value of beam of [0°/90°]8 is found to be the highest as compared to the beamswith angles [30°]16 and [60°]16. However, the natural frequency values in the beams that have the angle-ply of [θ]16 are lower than those of [θ/−θ]8, [(θ/−θ)4]s and [(θ/−θ)s]4.

Thermo-elastic stress of a metal-matrix composite disc under linearly-increasing temperature loading by analytical and FEM analysis

In this study, the elastic stress analysis of a composite disc with aluminium matrix subjected to a linearly-increasing temperature distribution has been carried out. The values of tangential and radial stress components that have occurred under the effect of the temperature from the inner surface of the disc towards the outer surface have been obtained by two different methods, numerical and analytical. In the analytical analysis, a computer program has been developed to get the values of thermal stresses. But in the numerical study carried out with the finite-element method, Abaqus 6.8 package program has been used. As a result of these analyses, it has been observed that the stress values obtained from both methods support each other. It has been determined under this temperature distribution that tangential stress components are always on the condition of compression in the inner surface of the disc and of tensile in the outer surface. It has also been found out that radial stress components are always in the state of tensile along the whole profile of the disc. Finally, the stress analysis of the same composite disc subjected to this temperature distribution, but with a reduced mass, has also been examined numerically.

Elastic-Plastic and Residual Stress Analysis of an Aluminum Metal-Matrix Composite Disk under Internal Pressures:

This paper deals with the elastic-plastic stress analysis of a thin aluminum metal-matrix composite disk under internal pressure. An analytical solution is performed for satisfying the elastic-plastic stress-strain relations and boundary conditions for small plastic deformations. The Tsai-Hill Criterion is used as a yield criterion, and an elastic-perfectly-plastic material is assumed. Elastic-plastic and residual stress distributions are obtained from inner radius to outer radius, and they are presented in the tables and figures. All radial stresses, σr, are compressive, and they are highest where the plastic deformation begins. All tangential stresses, σ θ , are tensile, and they are highest at the inner radius. Magnitude of the tangential residual stresses is higher than that of the radial residual stresses, and it is changing from negative sign to positive.

Thermal Elastic–Plastic Stress Analysis of Aluminum Metal–Matrix Composite Laminated Plates Under a Parabollically Temperature Distribution:

In this study, a thermal elastic–plastic stress analysis is carried out on steel-fiberreinforced aluminum metal–matrix composite laminated plates fixed at all edges. Temperature is chosen to vary parabollically. It is zero and T0 on the middle axis and at the upper–lower surfaces, respectively. The solution is executed for symmetric cross-ply (0° /90°)2 and angle-ply (30° / -30°)2, (45° / -45°)2, (60° / -60°)2 laminated plates. The elastic–plastic solution is carried out for small plastic deformations. The Tsai–Hill Theory is used as a yield criterion. Residual stress distributions along the thickness of the plates are obtained. All the residual stress components are in static balance with respect to middle plane of the laminates since they are symmetric in opposite signs.

An Elastic-Plastic Stress Analysis of Symmetric Aluminum Metal-Matrix Composite Laminated Plates Under Thermal Loads

In this study, a thermal elastic-plastic stress analysis is carried out on symmetric cross-ply (0°/90°)2 and angle-ply (30°/30°)2, (45°/45°)2, (60°/60°)2 aluminum metal-matrix composite laminated plates. Temperature changes parabolically from T0 up to T0 along the thickness. It is zero on the middle axis. The composite material is assumed to be linear strain hardening. The Tsai-Hill Theory is used as a yield criterion. The elastic-plastic solution is carried out for small plastic deformations. The distributions residual stress components of σ x and σ y are illustrated along the thickness of the laminated plates. All the residual stress moments are in static balance with respect to middle plane of the laminates since they are symmetric in opposite signs.

Formation of tangential pre-stress as a residual stress and its influence on the tribological performance of nodular cast irons

Abstract Since any state of residual stress influences the service behavior of a material, it is of particular interest for engineers and designers to know its benefits to machine parts, and where it can be utilized successfully. From this point of view, mechanical tangential pre-stress as circumferential compressive residual stress has been investigated for wear performance. For this purpose, a thick walled cylinder specimen model was established as a tribo-element, and the force, which will form the desired tangential pre-stress representing residual stress, has been calculated by the rules of elasticity theory. In order to compare the effect of residual stress on the wear performance under dry and lubricated conditions, 0.8 R e (R e : unidirectional yield strength) were applied to the nodular cast iron (DDK-40, DDK-60) specimens. Wear test results have been evaluated in terms of two different stress levels, 0 R e and 0.8 R e , formed on the specimen.

Experimental investigation of aluminum matrix functionally graded material: Microstructural and hardness analyses, fretting, fatigue, and mechanical properties:

This study investigated the mechanical properties of aluminum matrix functionally graded material (FGM) reinforced by integration of aluminum 2014 alloy (AlCu4SiMg) and 15 vol% SiC. The specimens were obtained by centrifugal casting technique, followed by aging treatment. The variations that occurred in microstructure, hardness, Young’s modulus, tensile strength, yield strength, elongation, fatigue, and fretting fatigue behaviors were analyzed. In both cast and aged conditions, it was observed that hardness values and mechanical properties changed between SiC-rich and aluminum-rich regions. Fatigue and fretting fatigue data were similar. It was determined that greater wear was occurring on the pad surfaces compared to that occurring on the sample surfaces.

Alüminyum Hidroksit ve Magnezyum Hidroksit Katkısının Termoplastik Poliüretan Malzemelerin Mekanik Özelliklerine Etkisi

Thermoplastic polyurethane materials are widely used in automotive, clothing, electrical and electronics, medical, construction, machine industry due to excellent physical and chemical properties. Thermoplastic polyurethane materials combustion and resistance to high temperature characteristics are poor. Additives and fillers are added into the polyurethane matrix to improve those properties. Particularly adding these agents as a flame retardant are affect mechanical properties of polyurethane materials. Therefore, it is important to determinate the mechanical properties of these materials. In this study, 5% by weight of the thermoplastic polyurethane material, aluminium tri hydroxide (ATH, (Al2O3 3H2O)) and magnesium hydroxide (MgOH, (Mg(OH)2)) were added. Ammonium polyphosphate (APP) as an intumescent flame retardant with inorganic flame retardants were added to increase the flame resistance of produced composite structure. Tensile test, tear test, hardness and Izod impact tests were made and compared of those produced composites. As a result of experiments the addition of ATH has lowered the tensile strength and tear strength contrast to this the addition of MgOH has improved those properties. Hardness and Izod impact test results were showed that both of the additives have no negative effect.