Experimental and finite element analysis on the performance of polyacetal/ carbon black nanocomposite gears

Gear specimens based on polyacetal (POM) containing nano-sized carbon black (CB) particles were produced using injection molding process. By employing a gear test rig, the wear and heat behavior of gears against meshing cycles and for different torques were investigated. Finite element method was employed to determine the gear tooth contact stress distribution against the meshing steps for pure POM and POM/CB nanocomposite gears. The morphology of worn gear tooth was studied by scanning electron microscopy. Differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) assessments were performed to evaluate the crystallinity and viscoelastic responses. Different types of gear tooth wear, severe material flowing and cracking at the tooth surface were observed for neat POM gears. Carbon black reinforced POM gears exhibited improved wear and heat resistance as compared to the unreinforced gears. The presence of CB switched the wear mechanism from material flowing to abrasion particularly in the flank region of driven gear. A number of strengthening mechanisms including crack pinning and crack deflection were detected for nanocomposite gear samples. The DMTA results revealed that the POM/CB has higher storage modulus and lower loss factor as compared to pure POM. A correlation between DMTA result and gear performance was observed.