Binnur Goren Kiral

Dynamic Analysis of A Symmetric Laminated Composite Beam Subjected to a Moving Load with Constant Velocity

This study deals with the dynamic behavior of a symmetric laminated composite beam subjected to a concentrated force traveling at a constant velocity. The dynamic analyses for a fixed-fixed composite beam under the action of a moving load are carried out by the finite element method. A three-dimensional finite element model based on the classical lamination theory is used. The Newmark integration method is employed in order to calculate the dynamic response. A computer code is developed using MATLAB to perform the finite element vibration analysis. The dynamic magnification, which is defined as the ratio between the dynamic and static displacements is obtained for different load velocities and ply orientations. The results reported in this paper show that load velocity and ply orientation have significant effect on the dynamic response, especially for those with [90]2s lay-up. For a fixed-fixed beam, the maximum mid-point deflection is observed when the total traveling time is equal to the first natural period of the beam.

Effect of Elastic Foundation on the Dynamic Response of Laminated Composite Beams to Moving Loads

The aim of this study is to present the dynamic behavior of a symmetric laminated composite beam with localized elastic supports. The dynamic response of a clamped—clamped composite beam to a moving point load with constant velocity is calculated by using the finite element method. A three-dimensional finite element model based on the classical lamination theory is used in order to define the structural stiffness. The Newmark integration method that is widely used in structural dynamics is employed in order to calculate the dynamic response of the beam. The finite element vibration analyses are performed by a computer program written in MATLAB. The dynamic magnification, which is defined as the ratio between the dynamic and the static displacements, is obtained for different load velocities, ply orientations, and spring locations. The effect of the spring number in the elastic foundation on the dynamic magnification is also investigated. The results reported in this article show that load velocity, ply orientation, and the location of the elastic support have significant effect on the dynamic response, especially for [45/-45] s and [90]2s lay-ups.

Experimental Investigation of the Dynamic Response of a Symmetric Laminated Composite Beam Via Laser Vibrometry

This article reports the experimental analysis of free and forced vibrations of a cantilever symmetric laminated composite beam with different lay-up sequences. The free vibrations generated due to initial displacements are recorded by two laser displacement sensors. The damping ratios for different ply orientations are determined by using the ratios between the successive peaks in the free vibration responses and the corresponding envelope curves. The dynamic response of the beam to a moving load with constant velocity is also investigated. The pressured air is blown out onto the beam to create the load and the movement of the load is achieved by an industrial robot manipulator. The moving load mechanism is peculiar to this study. The free and moving load responses are also examined by the finite element method. A commercial finite element package ANSYS® is used for numerical analyses. The results reported in this study show that the lay-up sequence has an important role on the dynamic response of the laminated composites and the velocity of the moving load affects the dynamic response considerably, especially for [90]2s lay-up.

DYNAMIC ANALYSIS OF ELASTICALLY SUPPORTED CRACKED BEAM SUBJECTED TO A CONCENTRATED MOVING LOAD

This study deals with the dynamic behavior of a cracked beam subjected to a concentrated force traveling at a constant velocity. Dynamic analyses for a hinged-hinged cracked beam resting on elastic supports under the action of a moving load are carried out by the finite element method. For the beam having rectangular cross-section, element formulation for crack element is developed by using the principles of fracture mechanics. In the numerical analysis, Newmark integration method is employed in order to calculate the dynamic response of the beam. The effects of crack depth, crack location, elastic support and load velocity on the dynamic displacements calculated for different locations on the beam are investigated. The results related to the dynamic response of the beam are presented in 3D graphs.

Performance of Steel Beam-to-Column Connections with Weld Defects under Inelastic Cyclic Loading

This study concerns the development of steel structures so that the connections can deform plastically without brittle fracture during an earthquake. Under earthquake loads, welded beam-to-column connections containing crack-like defects in the weld region have been studied using 3-D nonlinear finite element analyses. The effect of the connection type used for a welded steel structure and of the dynamic loading nature on the stress-strain distribution has been examined, as well as the fracture behaviour of the whole structure. Nonlinear finite element analyses were repeated for various frequency values for the different loading cases in order to study the effect of the strain rate.

FRICTION STIR WELDING OF AZ31 MAGNESIUM ALLOYS - A NUMERICAL AND EXPERIMENTAL STUDY

IN THIS PAPER, WELDABILITY OF MAGNESIUM ALLOYS BY FRICTION STIR WELD-ING (FSW) METHOD WHICH IS DIFFICULT TO JOIN BY THE FUSION WELDING HAVE BEEN INVESTIGATED EXPERIMENTALLY AND NUMERICALLY. TO THIS END, THE CONNECTION OF MAGNESIUM ALLOYS WAS PERFORMED USING DIFFERENT WELDING PARAMETERS. AZ31 MG-ALLOY PLATES WERE FRICTION STIR WELDED AT ROTATION SPEED OF 1200 REV/MIN AND TRANSLATIONAL SPEEDS OF 80,100,120,140 MM/MIN. TEMPERATURE EVOLUTION IN THE WELD ZONE DURING WELDING WAS MEASURED BY USING EMBEDDED K-TYPE THERMOCOUPLES. THE TEMPERATURE MEASUREMENTS ON BOTH AD-VANCING AND RETREADING SIDES WERE PERFORMED BY TEN THERMOCOU-PLES. TENSILE AND VICKERS HARDNESS TESTS WERE CONDUCTED TO EVALUATE THE MECHANICAL PROPERTIES AND THE HARDNESS DISTRIBUTION ON THE WELD, RESPECTIVELY. DURING FSW, HEAT IS GENERATED BY THE FRICTION AND PLASTIC DEFORMATION. KNOWLEDGE OF THE TEMPERATURE DISTRIBUTION IS REQUISITE SINCE MECHANICAL PROPERTIES AND MICROSTRUCTURE ARE SUBSTANTIALLY AFFECTED BY THE HEAT GENERATION. IT WAS OBSERVED THAT THE HEAT GENERATED DURING THE FSW PROCESS WAS INCREASING AND THE GRAIN STRUCTURE WAS REFINED AS THE TRANSLATIONAL SPEED WAS DECREAS-ING. IN THE FINITE ELEMENT ANALYSES, MODELING OF THE FSW PROCESS WERE CARRIED OUT BY ANSYS SOFTWARE TO DETERMINE THE TEMPERATURE AND STRESS DISTRIBUTIONS IN THE WELDED JOINT DURING FSW. AN APDL (ANSYS PARAMETRIC DESIGN LANGUAGE) CODE WAS DEVELOPED TO SIMU-LATE FSW PROCESS. TRANSIENT NONLINEAR FINITE ELEMENT ANALYSES WERE PERFORMED AT TWO STAGES WHICH THE FIRST STEP IS THERMAL ANALYSIS WHICH HEAT TRANSFER FROM THE PIN AND SHOULDER TO THE PLATES WAS MODELED AND THE SECOND IS THE STRUCTURAL ANALYSIS WHICH THE TEM-PERATURE DATA OBTAINED FROM THE THERMAL ANALYSIS IN THE FIRST STAGE IS USED.

Finite Element Analysis of Friction Stir Welded Aluminum Alloy AA6061-T6 Joints

Abstract The aim of this study was to develop a finite element model for predicting the transient temperature and stress fields during friction stir welding. For this purpose, a three-dimensional model based on the nonlinear finite element analysis (FEA) has been generated. The experimentally measured temperatures by using an infrared thermometer during experiments were compared to the results obtained by FEA. In the numerical simulations, mechanical and physical properties were considered depending on temperature. The effect of the rotational and transverse speeds on the distribution of temperature and stresses in the welded AA6061-T6 plates were examined. It was observed that the maximum temperature near the weld region increases with increasing rotational speed. The normal stresses, σx and σy also increase as the rotational speed increases. The temperature decreases as the tool transverse speed increases.

Effects of post-weld heat treatment on the microstructural evolution and mechanical properties of dissimilar friction stir welded AA6061+SiCp/AA6061-O joint

A research on the microstructure and mechanical properties of the dissimilar joint was carried out so as to understand the effects of post-weld heat treatment (PWHT) on microstructural evolution, microhardness, tensile and flexural properties of the dissimilar friction stir welded (FSWed) joint. The results showed that there is a sufficient and rather complicated material mixing in the nugget zone (NZ). After PWHT, the grains in the joint area except for the NZ demonstrated a grain refinement with more homogeneous and equiaxed grains. Fine and clustered SiC particles in the NZ are confirmed by scanning electron microscope (SEM). In addition, the microhardness values of nugget zones both in as-welded and PWHT condition exhibited a higher Vickers compared to that of AA6061-O. Furthermore, a mean tensile strength of 183.30 MPa that demonstrates a 52.22% increase in tensile strength is also observed in the transverse tensile tests subsequent to PWHT. Considering the three-point bending test results, it is explicit that an increase of 121.96% in the bending extension is obtained as there is no significant increase in maximum bending force after the PWHT.