Mass loaded resonance of a single unit impact damper caused by impacts and the resulting kinetic energy influx

Towards novel energy shunt inspired vibration suppression techniques: Principles, designs and applications

IN THIS PAPER WE PRESENT AN EXPERIMENTAL STUDY OF A THREE DIMENSIONAL PHYSICAL MODEL OF A THREE-FLOOR STRUCTURE SUBJECTED TO FORCED VIBRATIONS BY IMPOSING DISPLACEMENTS IN ITS SUPPORT. THE AIM OF THIS WORK IS TO ANALYZE THE BEHAVIOR OF THE BUILDING WHEN A DYNAMIC VIBRATION ABSORBER (DVA) IS ACTING. AN ANALYTIC SIMPLIFIED ANALYSIS AND A NUMERICAL STUDY ARE DEVELOPED TO OBTAIN THE NATURAL FREQUENCIES OF THE STRUCTURE. EXPERIMENTS ARE CARRIED OUT IN A VIBRATING TABLE. THE FREQUENCY RANGE TO BE EXPERIMENTALLY ANALYZED IS DETERMINED BY THE FIRST NATURAL FREQUENCY OF THE STRUCTURE FOR WHICH THE DVA DAMPING EFFECTS ARE VERIFIED. THE EQUIPMENT CAPABILITIES, I.E. THE FREQUENCIES, AMPLITUDES AND ADMISSIBLE LOAD, LIMIT THE ANALYSES. NEVERTHELESS, SATISFACTORY RESULTS ARE OBTAINED FOR THE STUDY OF THE FIRST MODE OF VIBRATION. THE EFFECT OF DIFFERENT AMPLITUDES OF THE IMPOSED SUPPORT MOTION IS ALSO ANALYZED. IN ADDITION, THE DAMPING EFFECT OF THE DVA DEVICE IS EVALUATED UPON VARYING ITS MASS AND ITS LOCATION IN THE STRUCTURE. THE CHARACTERISTIC CURVES IN THE FREQUENCY DOMAIN ARE OBTAINED COMPUTING THE FFT OF THE ACCELERATION HISTORY REGISTERED WITH PIEZOELECTRIC ACCELEROMETERS AT DIFFERENT CHECKPOINTS FOR THE CASES ANALYZED.

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Experimental vibration analysis for a 3d scaled model of a three-floor steel structure

This paper deals with passive vibration control using a bi-unit impact damper, also referred to as bi-unit impact vibration absorber. The main contribution of this work is to experimentally analyze the performance of a bi-unit impact vibration absorber using digital image processing. With the use of this technique, two or three bodies will be tracked simultaneously, namely, the primary system, and either the response of one or two impacting steel balls. The absorption pattern of the bi-unit is studied under free vibrations, constant frequency excitation, and sweep excitations. These results reveal that the use of digital image processing can eliminate the use of existing limitations which can sometimes change the dynamics of the system. The optical technique used captures reliably the detailed vibroimpact dynamics of the bodies. The detailed dynamic patterns of the particles during varying levels of energy absorption from the primary system are discussed in context of published theoretical results.

Performance of a Bi-unit Damper Using Digital Image Processing

Damping of the loose spring skirt (LSS) of a vibrating pipe under operating conditions was studied experimentally and numerically. Motion images made using a high speed charge-coupled device (CCD) camera as well as acceleration signals were analyzed in order to correlate the physical states of the LSS pipe system with the vibration transmissibility (TM) through the pipe. Experiments on the pipe undergoing harmonic excitation demonstrate that the damping of the LSS is caused by the same mechanism as with a conventional impact damper. Measurements of the acceleration TM as a function of excitation amplitude verified that the momentum exchange between the pipe and the auxiliary spring is the cause of the damping produced by the LSS pipe. Another finding of this research is that the experimental representation of the resonance shift phenomenon is related to two main operating conditions, namely: 1) the driving frequency and 2) the excitation amplitude. This research demonstrated the occurrence of the resonance shift phenomenon through experimental mapping of the system response at increasing excitation amplitudes using frequency sweep tests. Simulations of the LSS pipe system based on principal coordinate and impact damping analysis were performed in order to investigate and provide better explanations for LSS pipe system damping mechanisms. As a result of this research study, a new damping mechanism is proposed which is different from previous damping models. This research study has also addressed more practical boundary and excitation conditions for LSS pipe systems.

Study of the Damping Mechanisms of Loose Spring Skirts on Vibrating Pipes

This experimental research deals with passive vibration control of a primary mass using an impact vibration absorber (IVA). This paper is on two types of IVAs, namely, a simple IVA and a compound IVA, which have different attachment configurations for the impacting mass. The main contribution of this work was to experimentally analyze the effect of attachment configuration on IVAs. Thus, the primary objective of this research was to compare the absorption characteristics of simple and compound IVAs in case of transient and forced vibration. The secondary objective was to determine the effect of system parameters on the absorption efficiency of a compound IVA for both transient and forced vibration. It was shown that, for forced vibrations, the simple IVA (compared to the compound IVA) has more pronounced inefficient absorption region. On the other hand, the compound IVA hardly has a clear inefficient absorption region. In the respective absorption region, it is noted that the simple IVA has a more prominent vibration absorption level. Practical applications of the results are also discussed.

Caglar Ozerdim

Papers

Effect of Attachment Configuration on Impact Vibration Absorbers

Effect of attachment configuration on impact vibration absorbers