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Measuring the Internal Friction of Butadiene Acrylonitrile Rubber (NBR) Doped Nanocarbon Using the Laser Shadowgraphy Pulse Excitation Technique
D. I. Moubarak, H. H. Hassan, H. S. Ayoub, T. Y. El-Rasasi, Sh. A. Khairy, Y. H. Elbashar and A. S. Abdel-Rahaman

Internal friction is a very important mechanical property of matter which can be determined by many techniques, such as the pulse excitation technique and the torsional pendulum. In this paper we used the pulse excitation technique as it is non-contact, easy used and not affecting the sample, reliable, low cost, and accurate and suiting a wide variety of rubbery materials and elastomers. The samples chosen for this work is made of butadiene acrylonitrile rubber (NBR), which are loaded by different phr of N774 nanocarbon. The measured sample is prepared in form of 200 mm long string, having a homogenous circular cross-section of 3 mm diameter. A mechanical pulse is produced and delivered to the fixed end sample by mean of a punch from a small solenoid motor plunger. To generate a shadowgraph for the vibrating sample on a silicone photodiode, a laser beam is used. A storage oscilloscope is used to capture the natural resonance amplitude decay profile of the test sample from the obtained electric signal. The internal friction is obtained by mathematical analysis of the acquired data.

Keywords: Laser diode, butadiene acrylonitrile rubber (NBR), dynamic elasticity, internal friction, pulse excitation technique, laser shadowgraphy, low cost, non-Doppler laser vibrometry

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