Hasan Çallioğlu

An elastic-plastic stress analysis of thermoplastic composite beams loaded by bending moments

Abstract In this study, an elastic–plastic stress analysis is carried out on a high-density thermoplastic-based composite cantilever beam loaded by a bending moment at the free end. The composite beam is reinforced unidirectionally by steel fibers, at 0°, 30°, 45°, 60° and 90° orientation angles. An analytical solution is performed for satisfying both the governing differential equation in the plane stress case and boundary conditions for small plastic deformations. The solution is carried out under the assumption of the Bernoulli–Navier hypotheses. It is found that the intensity of the residual stress component of σx is maximum at the upper and lower surfaces or at the boundary of the elastic and plastic regions. The composite material is assumed to be strain-hardening. The Tsai–Hill theory is used as a yield criterion. The displacement components are found in the elastic region.

Stress Analysis of an Orthotropic Rotating Disc under Thermal Loading

In this study, a thermal stress analysis on a glass-fiber/epoxy orthotropic rotating hollow discs is investigated. A closed form solution is performed using polynomials under some considerations. The temperature distribution is chosen to vary parabolically from inner surface to outer surface along the radial sections. The distributions of the tangential and radial stress components are given in figures. When the temperature is increased further, the tangential stress component decreases at the inner surface, whereas increases at the outer surface, and radial stress component are reduced. The radial displacement is calculated analytically and has a higher value at the outer surface than at the inner surface.

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.

Thermal Stress Analysis of Curvilinearly Orthotropic Rotating Discs

This study deals with stress analysis on orthotropic rotating annular discs subjected to various temperature distributions, such as uniform, linearly increasing and decreasing with radius temperatures. Tangential and radial stresses in a rotating disc under the three different temperature profiles are plotted in figures. With the increasing temperature, the tangential stress component decreases at the inner surface whereas it increases at the outer surface, and the radial stress component reduces gradually for all the temperature distributions. The magnitude of the tangential stress component is higher than that of the radial stress component for all the discs under the lower temperatures of the temperature distributions. But, when the temperature is further increased, the tangential stress component decreases more at the inner surface. The radial displacement is also calculated analytically and has higher value at the outer surface than that of the inner surface for all the temperature distributions, except for radial displacement in the reference temperature.

Material nonlinear behavior of laminated metal–matrix composite plates supported at edges under uniform traverse loading

Abstract This paper deals with material non-linear behavior of steel fiber reinforced aluminum metal–matrix composite plates prepared by the squeeze casting process. By such an analysis it is intended to form an opinion about elastic–plastic behavior of laminated plates used in engineering problems associated with structural designs. Therefore, loads that begin plastic flow at any point of laminate for various stacking sequences are obtained. Afterwards, how further increase in loads gradually causes spreading of plastic zone is examined. Elastic/plastic and residual stress variations correspond to diverse stacking sequences of laminated plates are illustrated in figures. Plastic zone expansions are displayed in simply supported symmetric and antisymmetric laminated composite plates by contour plots. The finite element method is applied for analyses based on small deformation effects including shear deformation. For nonlinear solution of the problem a combined incremental/iterative procedure (modified Newton–Raphson) is followed and load increments are chosen to be sufficiently small to obtain a rapid-converged equilibrium state. Mechanical properties of an orthotropic layer are obtained experimentally.

Vibration behavior of a radially functionally graded annular disc with variable geometry

Abstract In this study, the free vibration behavior of an annular disc made of functionally graded material (FGM) with variable geometry is investigated. The elasticity modulus, density, and thickness of the disc are assumed to vary through the radial direction according to the power law so that the effects of their indexes on the natural frequency of the disc are investigated. The Poisson’s ratio is assumed as a constant. The natural frequencies of the disc are calculated for various boundary conditions by using classical plate theory, and the various types of mode shapes, which are described by the number of nodal diameters and nodal circles, are also discussed. Moreover, the effects of the ratio of the inner radius to the outer radius on the natural frequency are also considered. It is found that in order to increase the natural frequency, the elasticity modulus and thickness should be increased at the inner surface, whereas density should be increased at the outer surface. The natural frequency can also be increased by increasing the ratio of inner radius to outer radius. The results obtained are compared with the results of a finite-element-based commercial program, ANSYS®, and found to be consistent with each other.

Elasto-plastic Thermal Stress Analysis in Symmetric Thermoplastic Laminates

In this study, a thermal elastic–plastic stress analysis is carried out in steel fiber-reinforced symmetric thermoplastic laminated plates. The material is assumed to be strain-hardening. The orientation angles are chosen as, (0°/90°)s, (30°/30°)s, (45°/45°)s, (60°/60°)s, (15°/0°)s, (30°/0°)s, (45°/0°)s, (60°/0°)s, (75°/0°)s. The Tsai–Hill theory is used as a yield criterion in the solution. Temperature distribution is chosen as þT0 and T0 at the upper and lower surfaces, respectively. It is found that plastic yielding occurs at the same temperature; all the orientation angles and the plastic region expands the same at the same temperature.

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.

Nonlinear Stress Analysis of Unidirectionally Reinforced Symmetric Aluminum Metal-Matrix Laminated Beams under a Bending Moment

This study deals with elastic-plastic behavior of aluminum metal-matrix laminated cantilever beam subjected to a bending moment at the f ree end. The Bernoull i-Euler theory is utilized in the solution and small plastic de format ions are considered. The beam consists of four layers and its material is assumed to be linearly hardening. A few ply arrangements such as [9070° ] s , [ 3 0 7 3 0 ° ] s , [ 4 5 7 4 5 ° ] s and [607 -60° ] s are taken into considerat ion for such an analysis. The moment values that initiate plastic f low at any point of the beam are carried out for diverse stacking sequences. The variation of the elastic, elastic-plastic and residual stress components versus increasing plastic zone spread are given in tables and figures.