Multipoint Wave Measurement in Tuned Liquid Damper Using Laser Doppler Vibrometer and Stepwise Rotating Galvanometer Scanner

Liquid dampers, such as tuned liquid dampers (TLDs), are employed to improve serviceability by reducing wind-affected building vibrations. In order to maximize the vibration suppression efficiency of the liquid damper, the tuning frequency of the liquid damper should match the natural frequency of the building. Experimental evaluation of the tuning frequency of a liquid damper performed in a factory prior to installation in a building is a critical task to ensure correct performance, and for this, multipoint measurement of the TLD is required. In this study, a novel liquid level measurement system combining Laser Doppler Vibrometer (LDV) and a stepwise rotating galvanometer scanner was developed to observe liquid sloshing in TLD. The proposed system can measure the liquid level at multiple points simultaneously with a single laser point. In the experimental phase, the liquid damper’s natural frequency and mode shape are experimentally evaluated utilizing the developed system. The performance of the proposed system was verified by comparison with the video sensing system.

Use of Tuned Liquid Damper to Control Structural Vibration Structural.

The aim of this paper is to study the tuned liquid damper and it’s effectivness. The tunned liquid dampers are simply tuned mass damper where the liquid (usually water) replaces the mass.Tuned liquid dampers is a water tank placed over the structure which is able to reduce the dynamic structural response subjected to stimulation through sloshing effect. The effectiveness of tuned liquid damper depends upon various parameters. Tuned liquid damper are suitable for high rise building rather than short building. The tuned liquid damper decreases effect of harmonic excitation by Dissipating the energy of excitation through sloshing phenomenon.

Experimental study on annular cylindrical tuned liquid dampers for vibration control under different excitation angles

This work aims to experimentally show the effectiveness of annular cylindrical tuned liquid dampers (ACTLDs) on the classical tuned liquid column dampers (TLCDs) under the effect of inclined ground motion. For experimental measurements, a single-story model structure constituted by two plates at the top and bottom connected by four columns was constructed. Since the water length within the tuned liquid dampers (TLDs) is a very important parameter that affects the performance of the absorber, ACTLD and TLCD devices were designed such that their total water lengths be equal for comparison purposes. The modal characteristics of the model structure were determined by ambient vibration tests. The resonant frequency, head-loss coefficient, damping ratio, and water height-frequency diagram of ACTLD and TLCD devices were obtained experimentally through the shaking table tests. Then, the shaking table tests on the model structure with and without the absorbers under consideration were performed to obtain the acceleration and displacement time-histories and the damping ratio for the coupled system. In experimental tests, different excitation directions from 0 to 90 deg were considered. Results of the study show that ACTLDs are better than TLCDs at suppressing vibrations caused by ground motions acting on the structure at oblique angles.

The Surface Hardening of Parts of Liquid Dampers Made of High-Strength Steels

Variants of air-plasma sputtering (APS) and supersonic gas-flame sputtering in the HVOF modification of wear-resistant coatings on 30HGSN2A steel, used for the manufacture of rods of liquid dampers, have been worked out. Powder mixture designated as mixture A with chemical composition (wt%): 85 % chromium carbide (Cr3C2) powder and 15 % steel powder consisting of 20 % chromium and 80 % nickel were used for spraying. During the quality control of the applied coatings were evaluated: appearance, thickness, adhesion strength, microhardness and porosity. The phase composition of the coatings was also determined. The deposition modes are determined for varying the size and shape of powder mixture particles, as well as the deposition distances, which allow obtaining coatings with the required values of microhardness, adhesion strength and porosity. Such coatings can be obtained by using each of the three powder mixtures studied. The highest microhardness of the coating (11500-12100 MPa) was achieved using the powder mixture C (86%WC + 10%Co + 4%Cr) – and the HVOF method. The phase composition of this coating is represented by WC (base) and W2C carbides. The maximum shear strength (114 MPa) was achieved using a powder mixture A (85% Cr3 C2 + 15%X20H80) and the APS method. In the first variant, the porosity of the coating is 1.8-2.0 %, in the second - 5-8 %.

Design of elastic and dissipation joints in bearing structures of electronic packages

Mathematical modeling and experimental research represented in this paper is aimed at dynamic force analysis of circuit cards in order to eliminate or reduce dynamic stress and deflection to an acceptable level and to provide strength and reliability in design of circuit card assemblies subjected to vibration. In conditions when viscous friction forces are negligible and viscous friction dampers, such as liquid dampers, cannot be used reduction of oscillation amplitude in critical frequencies was proposed by creating dry friction damper. On the base of mathematical model, the method for reducing dynamic stress and deflection in critical section of circuit cards in resonance conditions has been developed by inserting additional elastic and dissipation joint introduced by dry friction damper. The dry friction damper device is introduced in three variants of design. The effectiveness of dry friction damper is characterized by its elastic and damping characteristics and especially by the stiffness.