Vibration analysis of structures

Abstract

The present focuses on dynamic nature of various structures present in an environment where they are bound to undergo vibrations. In such vibrating conditions when they are subjected to a resonance they experience high amplitudes, leading to the failure of the structure. Hence, the study of operating frequencies of
1) Machine Foundations
i) Los Angels Abrasion Machine
ii) Jaw Crushing Machine
2) Fiber Reinforced Glass Composites – varying the number of layers
i) 16 layers
ii) 12 layers
3) Steel Flats
In this study we have used a non computational technique for analysis of dynamic nature of structures. Brüel&Kjær PULSE™, Multi-analyzer System Type 3560 was used in the
analysis. The operating frequency ranges in case of Los Angels Abrasion Machine is found to be 48 Hz – first frequency and 73 Hz – second frequency. In case of Jaw Crushing Machine is 42.2 Hz – first frequency and 71.8 Hz – second frequency. Where as, in case of steel flat the operating frequency is found to be 41.50 Hz. The fiber reinforced glass composites were decreased in area in a regular pattern and the pattern of frequency variation was observed. In case of 16 layers the first frequency decreased from 284 Hz – 236 Hz and the second frequency also depicted similar pattern. In case of 12 layers the first frequency decreased from 190 Hz – 160 Hz and the second frequency varied from 588 Hz – 390 Hz. The observed trend is justified as the value of K decreases as we decrease the area of the sample. We have also studied the determination of Buckling load from frequency study incase of a steel flat. When steel flat is subjected to increasing axial load the operating frequency is observed to decrease. When this operating frequency tends to zero the axial load nears the buckling load of that structure. 30cm steel flat is tested in a UTM under increasing axial load. The initial frequency under no load condition is 260 Hz. Under a load of 0.4 ton the first frequency decreases to 168 Hz. Extrapolating the decreasing trend we get the buckling load as 1.1739 ton. A similar trend was observed in case of second frequencies. The vibration analysis of the foundations of various machines will help us in designing them such that their serviceability is increased. Similarly, fiber reinforced composites are being used in various structural members. These demands require a deeper understanding of fiber composite behavior. Composites offer great promise as light weight and strong structural materials. The study of dynamic behavior of a structure holds atmost importance in evaluating its engineering performance and serviceability.