توجه: محتویات این صفحه به صورت خودکار پردازش شده و مقاله‌های نویسندگانی با تشابه اسمی، همگی در بخش یکسان نمایش داده می‌شوند.
۱CHAOTIC RESPONSE AND BIFURCATION ANALYSIS OF A TIMOSHENKO BEAM WITH BACKLASH SUPPORT SUBJECTED TO MOVING MASSES
نویسنده(ها): ،
اطلاعات انتشار: کنفرانس ملی مهندسی مکانیک ایران، سال
تعداد صفحات: ۱۹
. A simply supported Timoshenko beam with an intermediate backlash is considered. The beam equations of motion are obtained based on the Timoshenko beam theory by including the dynamic effect of a moving mass travelling along the vibrating path. The equations of motion are discretized by using the assumed modes technique and solved using the Runge–Kutta method. The analysis methods employed in this study are the dynamic trajectories of the beam midpoint, power spectra, Poincare´ maps, bifurcation diagrams and Lyapunov exponents. The dimensionless backlash gap coefficient and the moving mass speed are used as control parameters. The numerical results reveal that the system exhibits a diverse range of periodic, sub–harmonic, and chaotic behaviors. The onset of chaotic motion is identified from the phase diagrams, power spectra, Poincaré maps, and Lyapunov exponents of the system. Therefore, the main aim of this study is to provide a better understanding of the characteristics and dynamic behaviors of the beams subjected to moving masses<\div>

۲CONTROL OF A MULTI–CRACKED TIMOSHENKO BEAM SUBJECT TO A MOVING MASS USING PIEZOELECTRIC ACTUATORS
نویسنده(ها):
اطلاعات انتشار: کنفرانس ملی مهندسی مکانیک ایران، سال
تعداد صفحات: ۱۹
In this paper, the dynamic modeling and control of a multi cracked beam subject to a moving mass is presented. The beam equations of motion are obtained based on the Timoshenko beam theory by including the dynamic effect of a moving mass traveling along a vibrating path. The equations of motion are first discretized by using the assumed modes method. The cracked beam is modeled as numbers of segments connected by two massless springs at the crack locations (one extensional and another one rotational). Considering the compatibility requirements on the crack section, the relationships between any two spans can be obtained. One piezoelectric actuator is then attached along the bottom of the beam. In order to reduce the vibration of the beam under a moving mass, a controller with full state feedback is designed based on linearized equations of motion. Finally, numerical simulations are performed with respect to different conditions such as crack size, type of the beam, and velocities. The controller with a piezoelectric actuator shows excellent performance under a moving mass<\div>

۳DIRECT AND INVERSE METHODS ON FREE VIBRATION ANALYSIS OF TIMOSHENKO BEAMS WITH AN ARBITRARY NUMBER OF CRACKS
نویسنده(ها):
اطلاعات انتشار: کنفرانس ملی مهندسی مکانیک ایران، سال
تعداد صفحات: ۱۳
An analytical transfer matrix method is used to solve the direct and inverse problems of Timoshenko beams with an arbitrary number of cracks. The cracked beam is modeled as numbers of segments connected by two massless springs (one extensional and another one rotational). Considering the compatibility requirements on the crack section, the relationships between any two spans can be obtained. By using the analytical transfer matrix method, eigensolutions of the cracked system can be calculated explicitly. In an inverse problem, multi–crack detection for beams by natural frequencies has been formulated in the form of a non–linear optimization problem, and then solved by using the MATLAB functions. The equation is the basic instrument in solving the multi–crack detection of the beam. The set of crack parameters to be detected includes not only the crack position and depth, but also the quantity of possible cracks. The theoretical results are also validated by a comparison with experimental measurements.<\div>

۴VIBRATION RESPONSE OF A SIMPLY SUPPORTED BEAM SUBJECTED TO A MOVING MASS
نویسنده(ها):
اطلاعات انتشار: کنفرانس ملی مهندسی مکانیک ایران، سال
تعداد صفحات: ۱۱
An analytical method is presented to determine the dynamic response of a simply supported Euler–Bernoulli beam subjected to a moving mass. The moving mass causes convective acceleration terms in the equation of motion which are not presented when the problem is solved by assuming moving load. These terms change the characteristic of dynamic response of the beam in compared with one subjected to a moving load. First, the equation of motion is achieved by using the assumed modal shape of vibration. The obtained equation consists of perturbed terms. Then, an approximate analytical solution of the problem is found using the method of multiple scales, a perturbation technique. It is seen that the convective terms reduce the frequency of the beam–mass system. Also, a numerical method is presented to solve the moving mass problem to validate the results from perturbation technique. Numerical simulations show a fine agreement between the results from analytical and numerical methods<\div>

۵AN INVESTIGATION ON THE DYNAMIC RESPONSE OF CRACKED TIMOSHENKO BEAMS WITH MOVING MASS
نویسنده(ها):
اطلاعات انتشار: کنفرانس ملی مهندسی مکانیک ایران، سال
تعداد صفحات: ۱۶
An analytical method is presented to determine the effect of open and breathing cracks on the dynamic behavior of the undamped Timoshenko beams subject to a moving mass. In equations of motion, considering the moving mass causes convective acceleration terms; the same terms are not presented when the moving load is assumed. The cracked beam is modeled as numbers of segments connected by two massless springs (one extensional and another one rotational). Considering the compatibility requirements on the cracked section, the relationships between any two spans can be obtained. By using the analytical transfer matrix method, eigensolutions of the cracked system can be calculated explicitly. By considering a breathing crack that opens and closes continuously during oscillation, the instantaneous frequencies are used to determine instantaneous mode shapes (IM) for dynamic response calculation of the beam subjected to a moving mass. Several numerical examples are also designed to evaluate the crack effects by considering the external acceleration terms consisting of four separate terms<\div>

۶Vibration Control of an Optical Device
نویسنده(ها): ، ، ،
اطلاعات انتشار: کنفرانس دو سالانه بین المللی مکانیک جامدات تجربی، سال
تعداد صفحات: ۸
The goal of this research is vibration damping of an optical device. This study considers the modeling and identification of a nonlinear hysteretic system, wire–rope isolator. A shock and vibration absorber commonly used in naval vessel and airplanes is the wire–rope spring. Wire rope springs show a good damping performance due to rubbing and sliding friction between the wire rope strands. Cyclic loading quasi static tests are carried out on a wire–rope isolator in order to experimentally obtain its hysteretic behavior using simple tensile\compression equipments. The wire–rope isolator exhibits asymmetric hysteresis loop, which posses a hardening loading overlap in the loading curves. The Bouc–Wen model is a nonlinear hysteresis model on a phenomenological base that is one of the most accepted smoothly varying differential models in the engineering field. Because of overlapping and time–history–dependent of the hysteresis force a modified version of the original Bouc–Wen model is presented. An optimization problem is formulated in order to identify the model parameters from the experimental data of the quasi static tests using Genetic Algorithm. Finally, the dynamic response behavior of a wire–rope isolation system is evaluated. In order to reduce the vibration amplitude, type and number of wire–rope isolator can be changed.<\div>
نمایش نتایج ۱ تا ۶ از میان ۶ نتیجه