Mustafa Yaman

Bio: Mustafa Yaman is an academic researcher from Atatürk University. The author has contributed to research in topics: Vibration & Cantilever. The author has an hindex of 7, co-authored 16 publications receiving 138 citations.

Vibration control of a cantilever beam of varying orientation

Abstract: We investigate the problem of suppressing the vibrations of a non-linear system with a cantilever beam of varying orientation subject to parametric and direct excitation. It is known that the growth of the response is limited by non-linearity. Therefore, vibration control and high-amplitude response suppressions of the first mode of a cantilever beam can be performed using a simple non-linear feedback law. This control law is based on cubic velocity feedback. The method of multiples scales is used to construct first-order non-linear ordinary differential equations governing the modulation of the amplitudes and phases. The stability and effects of different system parameters are studied numerically.

Direct and parametric excitation of a nonlinear cantilever beam of varying orientation with time-delay state feedback

Abstract: The primary and parametric resonances of a directly and parametrically excited nonlinear cantilever beam of varying orientation with time-delay in the linear state feedback are investigated. The time-delay is presented in the proportional feedback and the derivative feedback, respectively. The method of multiple scales is used to obtain the first-order approximation of response. The effect of the feedback gains and time-delay on the steady state responses of two type resonances is investigated. It is found that a proper selection of the feedback gains and time-delay can enhance the control performance.

Finite element vibration analysis of a partially covered cantilever beam with concentrated tip mass

Abstract: The work presented in this paper is the theoretical investigation of the dynamical behavior of a cantilever beam, partially covered by damping and constraining layers, with concentrated mass at the free end. A finite element method is used in order to obtain the resonant frequencies and loss factors. The resonant frequencies and loss factors for different physical and geometrical parameters are determined. The variations of these two parameters are found to be strongly dependent on the geometrical and physical properties of the constraining layers and the mass ratio.

The analysis of the orientation effect of non-linear flexible systems on performance of the pendulum absorber

Abstract: In practical applications, many vibration absorbers are used to absorb oscillation of a structure, one of which is pendulum-type vibration absorbers. They are widely used in engineering applications where oscillations of a structure are constrained within a prescribed envelope. In this study, the primary structure consists of a flexible beam which has a single degree of freedom, and is subjected to a vertical sinusoidal base excitation. Non-linearity in the primary structure is due to large deflections. The rotation point of the pendulum-type absorber is attached to the tip of the primary structure. The primary structure and absorber together constitute a couple systems with two degrees of freedom. The primary objective of this study is to determine the effectiveness of pendulum-type passive vibration absorber attached to a primary structure whose orientation varies. In this study, the orientation at which the absorber is effective is established, and the factors that affect performance of the absorber are determined. The results are in good agreement with the experimental ones given in the literature.

Adomian Decomposition Method for Solving a Cantilever Beam of Varying Orientation with Tip Mass

Abstract: A uniform cantilever beam of varying orientation with a tip mass at the free end can be used as a basic model of many practical structures such as flexible robot arm or antenna mast. The aim of the study described here is to investigate the influence of the orientation effect on the natural frequency of the cantilever beam carrying a tip mass. An analytic solution is obtained by using the Adomian decomposition method. The accuracy of the Adomian decomposition method with a varying number of terms in the series is investigated by comparing its results with those generated by the finite element method.

Parametric noise squeezing and parametric resonance of microcantilevers in air and liquid environments.

Abstract: In this work, parametric noise squeezing and parametric resonance are realized through the use of an electronic feedback circuit to excite a microcantilever with a signal proportional to the product of the microcantilever's displacement and a harmonic signal. The cantilever's displacement is monitored using an optical lever technique. By adjusting the gain of an amplifier in the feedback circuit, regimes of parametric noise squeezing/amplification and the principal and secondary parametric resonances of fundamental and higher order eigenmodes can be easily accessed. The exceptionally symmetric amplitude response of the microcantilever in the narrow frequency bandwidth is traced to a nonlinear parametric excitation term that arises due to the cubic nonlinearity in the output of the position-sensitive photodiode. The feedback circuit, working in both the regimes of parametric resonance and noise squeezing, allows an enhancement of the microcantilever's effective quality-factor (Q-factor) by two orders of magnitude under ambient conditions, extending the mass sensing capabilities of a conventional microcantilever into the sub-picogram regime. Likewise, experiments designed to parametrically oscillate a microcantilever in water using electronic feedback also show an increase in the microcantilever's effective Q-factor by two orders of magnitude, opening the field to high-sensitivity mass sensing in liquid environments.

Tuning dynamic vibration absorbers by using ant colony optimization

Abstract: The present contribution deals with the optimal tuning of two different types of dynamic vibration absorbers (DVA) by using ant colony optimization, namely the vibrating blade DVA and the multi-mode DVA. Dynamic vibration absorbers are mechanical appendages constituted by mass, spring and damping elements, which are coupled to a mechanical system to provide vibration attenuation. The tuning of the dynamic vibration absorber is the procedure that sets the anti-resonance frequency to a given value by adjusting the parameters of the dynamic vibration absorber. Based on this methodology, the optimization problem is defined as the minimization of the objective function that describes the vibration amplitude of the primary structure. To solve the optimization problem, ant colony optimization was used. In the early nineties, when the Ant Colony algorithm was first proposed, it was used as an alternative approach for the solution of combinatorial optimization problems, such as the traveling salesman problem. However, the extension for operating with continuous variables is recent and this feature is still under development. In the present formulation, the optimization technique was extended to handle continuous design variables. Numerical results are reported, aiming at illustrating the success of using the proposed methodology, as applied to mechanical system design.

Influence of carbon nanotubes on thermal expansion coefficient and thermal buckling of polymer composite plates: experimental and numerical investigations

Abstract: The first aim of this article is to experimentally explore the effect of multi-walled carbon nanotubes (MWCNTs) on the coefficient of thermal expansion (CTE) of epoxy-based composites. Focusing on ...

Design of damping properties of hybrid laminates through a global optimisation strategy

Abstract: In this paper a global optimisation technique for the design of damping properties of hybrid elastomer/composite laminates is presented. The goal of the procedure is to maximise the first N modal loss factors of the laminate subject to constraints on the in-plane and out-of-plane stiffness along with a constraint on the weight of the plate. The problem is considered in the most general case: no simplifying hypotheses are made on the behaviour of the hybrid laminate, thus allowing us to consider as design variables the number of layers (both of the elastic and viscoelastic layers), their thickness and orientations as well as the position of the viscoelastic plies within the stacking sequence. The proposed approach relies on one hand, upon the dynamic response of the structure in terms of natural undamped frequencies and modal loss factors which are evaluated using the well-known Iterative Modal Strain Energy (IMSE) method, and on the other hand on the use of genetic algorithms as optimisation tool to perform the solution’s search. As an example, the method is applied to a rectangular plate and the results demonstrate the effectiveness of the proposed strategy.

Dynamical analysis of multilayered cantilevers

Abstract: A three-layered clamped-free (cantilevered) beam is considered and the nonlinear vibrations is investigated for the first time; internal resonances and complex vibrations are also investigated. Based on constitutive relations and Hamilton's principle, the kinetic and potential energies are constructed and balanced leading to nonlinear coupled equations for transverse and axial motions. Using inextensibility condition, a model of the cantilevered beam with inertial and stiffness nonlinearities is obtained. This is discretised using Galerkin's method and solved using a continuation method in the framework of pseudo-arclength. The nonlinear oscillation behaviour is analysed with special attention to the nonlinearities due to large-amplitude deflections. Different layer thickness and composition effects on the nonlinear oscillation are discussed. It is shown that when the system key parameters are selected carefully, a complex oscillation behaviour with internal resonance is displayed.