Investigation on the effect of strain rate on standard involute and asymmetric polymer gears using the newly design fixture for single tooth testing method

Abstract

Effect of strain rate on the single tooth strength of nylon-based gear has been investigated using a newly designed testing fixture. An adjustable single tooth testing fixture has been designed and developed for the purposed of single tooth loading test which is able to accommodate the gear with varying thickness. Injection molded nylon-6 and SLS (selective laser sintering) printed glass filled nylon-6 standard involute and asymmetric gear tooth have been investigated for their single tooth loading test at three different strain rates of 0.0003, 0.003, and 0.01 per sec. Single tooth strength for both injection and printed gear is found to increase with the increase in strain rate. Injection molded single gear tooth undergone bending failure whereas SLS printed gear tooth shows fracture failure. Resistance to single tooth deflection at higher strain rate has drastically increased for injection molded standard involute (IS) gear tooth by 23% whereas, asymmetric gear tooth IA20 followed by IA34 shows slight increment. SLS printed asymmetric gear tooth PAG20/34 exhibits maximum single tooth strength among all three types of printed gears at all the three strain rates. At higher strain rate of 0.01 per sec, single tooth strength dominates by tooth profile geometry whereas, at lower strain rate of 0.0003 per sec, it dominates by tooth profile geometry and microstructure.