Study on the gear performance of polymer-clay nanocomposites by applying step and constant loading schemes and image analysis

Abstract

The efficiency of polymer nanocomposites for gear applications is evaluated in this paper. Poly(butylene terephthalate) (PBT) and montmorillonite (MMT) were employed as the polymer matrix and nanoreinforcement, respectively. Gear tests were conducted under 6 and 11 Nm constant torques, determined via step-loading approach. Image processing was employed to calculate gear tooth wear, identify wear patterns, and explore failure mechanisms. The inclusions of MMT reduced tooth surface temperature and wear, at identical durations, relative to neat PBT. The average gear lifespan increased up to 107% and 79% at 6 and 11 Nm loads, respectively, with clay addition. Tooth profile deviation was suppressed for PBT/MMT gears, in contrast to neat PBT, at both applied loads. At 6 Nm, fatigue-induced pitch cracking was predominant for both pristine and nanocomposite gears, while the failure mode at 11 Nm was altered from thermal bending for pure PBT to crack-induced fracture for PBT/MMT gears. The microstructural evaluation of worn teeth indicated the transition of wear mechanism from adhesive for pure PBT to abrasive with smoother worn surface for PBT/MMT gears. Digital image correlation (DIC) was applied to obtain the strain distribution of deformed gear teeth and study its correlation with the applied torque and material composition.