This paper presents a novel method to nonlinearly investigate the dynamics of the coupled axial and torsional vibrations in the circular cross section beam of the steam turbine generator using the FFT analysis. Firstly, the coupled axial and torsional vibrations of a beam are proved by equivalent law of shearing stress and different boundary conditions. Then, a nonlinear mathematical model of t...

ABSTRACT. This paper is concerned with the torsional vibrations of a nonhomogeneous magnetostrictive elastic cylinder. The cylinder is subjected to the action of a circumferential magnetic field produced by an axial current of constant density and the deformation of a magnetostrictive cylinder is produced by a constant longitudinal magnetic field. The frequency equation is determined, and the d...

A hybrid longitudinal-torsional ultrasonic transducer is designed and fabricated in this research. The design of the transducer was performed using the FE method with ABAQUS software, with the aim of combining the longitudinal and torsional vibration modes. The transducer horn is then fabricated using a 4-axis milling machine. The PZT stacks are employed in order to excite the transducer. The t...

A novel method, which was called a slope method, has been proposed to measure fluid density by the micro-cantilever sensing chip. The theoretical formulas of the slope method were discussed and established when the micro-cantilever sensing chip was under flexural and torsional vibrations. The slope was calculated based on the fitted curve between the excitation and output voltages of sensing ch...

Torsional vibrations and resonance problems with synchronous machines are most frequently encountered in rotor systems with long shafts and large inertias constituting a weakly damped mechanical resonator which exhibits a low resonance frequency. It is impossible to obtain a effective mechanical damping for these torsional vibrations, but by using a power electronics device and an inductive or ...

A hybrid longitudinal-torsional ultrasonic transducer is designed and fabricated in this research. The design of the transducer was performed using the FE method with ABAQUS software, with the aim of combining the longitudinal and torsional vibration modes. The transducer horn is then fabricated using a 4-axis milling machine. The PZT stacks are employed in order to excite the transducer. The t...

Size-dependent longitudinal and torsional vibrations of nano-beams are examined by two-phase mixture integral elasticity. A new and efficient elastodynamic model is conceived by convexly combining the local phase with strain- and stress-driven purely nonlocal phases. The proposed stress-driven nonlocal integral mixture leads to well-posed structural problems for any value of the scale parameter...

Abstract: The governing equations of motion for a drill string considering coupling between axial, lateral and torsional vibrations are obtained using a Lagrangian approach. The result leads to a set of non-linear equations with time varying coefficients. A fully coupled model for axial, lateral, and torsional vibrations of drill strings is presented. The bit/formation interactions are assumed ...

Cyclic vibratory torque requirement of a Reciprocating Compressor sets in torsional vibrations in compressor motor system. Explanation of development of pulsating currents, due to vibratory motion of motor rotor is given. The pulsating currents are superimposed on steady state currents. Mathematical mod~ls for analysing torsional vibrations of the system and nett motor current due to combinatio...

The aim of this paper is to design a robust output-feedback controller to eliminate torsional stick-slip vibrations. A multi-modal model of the torsional dynamics with a nonlinear bit-rock interaction model is used. The controller design is based on skewed-μ DK-iteration and the stability of the closed-loop nonlinear system is analyzed. The proposed controller design strategy offers significant...