An experimental characterization of the load carrying capacity of oil lubricated gears made of torlon PAI grade 4203

Abstract Modern developments in high strength polymers and thermoplastics have driven interest in the gearing industry as feasible material choices for lightweight E‑Mobility (wheelchairs, scooters, bicycles), accessory drives such as engine balancers and actuators, and other lower power density power transmission needs. Polymer gears offer some very desirable engineering and economic benefits over metals gears such as being lightweight (leading to cost savings in transportation of materials and product) and having higher internal damping, leading to reduced noise. However, the material properties of polymers are more complex (viscoelastic and temperature sensitive) and diverse (amorphous to semi-crystalline to fiber-reinforced). In addition, the lower elastic modulus can lead to higher deformations in both the tooth and gear body complicating the gear loaded tooth contact analysis. As such, there is a significant gap in the open literature on gear load-carrying capacity with different polymers. In addition, to maximize contact durability and improve efficiency (lower heat generation) these gear sets are lubricated using oils as is commonly done with metal gears but many of the already few studies on polymer gears have been done under grease, dry lubricants or no lubricant. In this study a back-to-back test methodology is utilized for experimentally evaluating the load carrying capacity and failure mode of oil lubricated gears made from Torlon® Polyamide-Imide (PAI) Grade 4203. The experiments are performed under multiple temperatures and a range of applied torques. An analysis of the temperature and torque dependent load carrying capacity is performed to benchmark the material and performance. Fractography is performed and analyzed to identify the critical failure modes.