Attenuation Of Grass Trimmer Handle Vibration Using Imposing Node Technique
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Date
2012-06
Authors
Ko, Ying Hao
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
Prolonged use of grass trimmer exposes the user to the risk of hand-arm vibration
syndrome. Imposing node technique was investigated in order to achieve low
vibration (node) at the grass trimmer handle location. It is established that, for the
grass trimmer system which can be modelled as a beam, the vibration at the handle
location can be minimized. The mathematical model of grass trimmer system is
presented, and a criterion for implementing the vibration attenuation by imposing
node technique is developed. The optimum tuning frequencies of tuned vibration
absorbers (TVAs) attached at the points of 0.74L and 0.85L along the shaft of grass
trimmer were determined using this approach. Transverse deflection, experimental
modal analysis, and operating deflection shape analysis of the grass trimmer were
carried out and TVAs were designed and fabricated to validate the proposed theory
and display its practicality. The results indicated that node was induced in the
vicinity of the loop handle location (0.79L). Moreover, the vibration along the
segment of the shaft (0.70L-0.94L) was also found to have relatively small amplitude.
The TVAs were found to have best performance with 71% reduction on the
frequency-weighted rms acceleration at loop handle and 72% for rear handle. The
results from modal analysis and operating deflection shape revealed that the presence
of TVAs has successfully reduced the large deformations of the loop and rear handle
where the node was shifted nearer to the handle location. The effect of TVAs was
also evaluated during the field test involving grass trimming operation and subjective
rating. The results indicated that average reduction of frequency-weighted rms
acceleration was by 25%, 69%, 17%, 58% in Xh-, Yh-, Zh-axes and hv a respectively
during the cutting operation. From the field test, subjective rating of vibration perception consistently rate better for controlled grass trimmer.
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Keywords
Attenuation of grass trimmer handle vibration , using imposing node technique