IMPROVED ANALYSIS OF A PROPPED CANTILEVER UNDER LATERAL VIBRATION

Continuous systems are sometimes analysed as lumped masses connected by massless elements. This reduces the structure’s degree of freedom and therefore simplifies the analysis. However this over simplification introduces an error in the analysis and the results are therefore approximate. In this work sections of the vibrating beam were isolated and the equations of the forces causing vibration obtained using the Hamilton’s principle. These forces were applied to the nodes of an equivalent lumped mass beam and the stiffness modification needed for it to behave as a continuous beam obtained. The beam’s stiffness was modified using a set of stiffness modification factors to . It was observed that by applying these factors in the dynamic analysis of the beam using the Lagrange’s equation, we obtain the exact values of the fundamental frequency irrespective of the way the mass of the beam was lumped. From this work we observed that in order to obtain an accurate dynamic response from a lumped mass beam there is need to modify the stiffness composition of the system and no linear modification of the stiffness distribution of lumped mass beams can cause them to be dynamically equivalent to the continuous beams. This is so because the values of the modification factors obtained for each beam segment were not equal. The stiffness modification factors were obtained for elements at different sections of the beam

Design of a Maglev Inertial Actuator with High Mass Power Ratio for Lateral Vibration Control of Propulsion Shafting

The maglev inertial actuators with high power and mass maybe effective for lateral vibration control of a propulsion shafting. But the mass power ratio of the actuators currently in use is too small to meet the requirements. In the paper, a maglev inertial actuator was innovatively designed with high mass power ratio. The structure of the magnetic circuit assembly and the suspending assembly were designed and optimized. To verify the property of the proposed maglev inertial actuator, a prototype with mass less than 8 kg was developed and tests were carried out. The minimum effective output force can reach 200 N within the frequency band of 20–300 Hz. A lateral vibration of a propulsion shafting system was constructed and the active control effect was tested. The experimental results show that the proposed maglev inertial actuator has a good effect on lateral vibration control of shafting.

Rotating blade faults classification of a rotor-disk-blade system using artificial neural network

<span lang="EN-US">In this paper, the artificial neural network (ANN) has been utilized for rotating machinery faults detection and classification. First, experiments were performed to measure the lateral vibration signals of laboratory test rigs for rotor-disk-blade when the blades are defective. A rotor-disk-blade system with 6 regular blades and 5 blades with various defects was constructed. Second, the ANN was applied to classify the different </span><em><span lang="EN-US">x</span></em><span lang="EN-US">- and </span><em><span lang="EN-US">y</span></em><span lang="EN-US">-axis lateral vibrations due to different blade faults. The results based on training and testing with different data samples of the fault types indicate that the ANN is robust and can effectively identify and distinguish different blade faults caused by lateral vibrations in a rotor. As compared to the literature, the present paper presents a novel work of identifying and classifying various rotating blade faults commonly encountered in rotating machines using ANN. Experimental data of lateral vibrations of the rotor-disk-blade system in both </span><em><span lang="EN-US">x</span></em><span lang="EN-US">- and </span><em><span lang="EN-US">y</span></em><span lang="EN-US">-directions are used for the training and testing of the network.</span>

A semi-active tuned liquid column damper for lateral vibration control of high-rise structures: Theory and experimental verification

This paper presents a new type of semi-active tuned liquid column damper (S-TLCD) for the lateral vibration control of high-rise civil engineering structures. Analogous to the passive tuned liquid column damper (TLCD), the S-TLCD comprises a U-shaped tank consisting of two vertical columns, which are arranged at a distance from each other and communicating through a horizontal passage. The tank is partially filled with a Newtonian fluid until the liquid reaches a certain level in the columns. In contrast to the passive TLCD, the S-TLCD provides also mechanisms for a continuous adaptation of both its natural frequency and damping behaviour in real-time. In the first part of the paper, the governing equations of the S-TLCD are derived based on the Bernoulli equation of a non-stationary incompressible liquid flow. The natural frequency of the S-TLCD is revealed to depend on the scaled length of the liquid. The scaling amount of the liquid length is formulated in dependence of the cross-sectional area ratios of the tank segments. The mathematical description of the S-TLCD is concluded by providing the state-space representation of a multi-degree-of-freedom structure with several S-TLCDs. In the second part of the paper, the derived natural frequency equation is verified and the proof of concept of the S-TLCD is shown by experimental investigations, which are performed on an S-TLCD model utilizing a test structure and shaking table tests.