Master of Science, The Ohio State University, 2016, Mechanical Engineering

An experimental investigation of spur gear efficiency is conducted under various jet-lubricated and dip-lubricated conditions. A test methodology is developed to measure load-independent (spin) and load-dependent (mechanical) losses to a gearbox containing a single spur gear pair. An experimental test matrix is defined to study the influence that the lubrication method has on these losses. The test matrix includes two dip-lubricated conditions that vary in submersion level of the gear pair, and four jet-lubricated conditions that vary in the gear mesh target location and velocity of the oil. Results indicate that the spin power losses are impacted by the lubrication method significantly while the mechanical losses are not influenced. An investigation of spur gear contact fatigue is conducted under several lubrication schemes from the efficiency study. A test methodology is developed to evaluate variations in tooth geometry due to surface wear, roughness, and pitting life. Pitting lives under each lubrication method are analyzed statistically to quantify any meaningful differences in gear pitting life. Results indicate that contact fatigue lives from jet-lubricated tests are as high as dip-lubricated ones as long as jet velocities are sufficient.

Committee: Ahmet Kahraman Dr. (Advisor); Brian Harper Dr. (Committee Member) Subjects: Mechanical Engineering

Master of Science, The Ohio State University, 2011, Mechanical Engineering

In this study, the influence of different gear steels on the contact fatigue life of ground spur gear pairs was investigated. The three gear steels considered in the study were (i) AISI 8620, (ii) AISI 4620M, and (iii) AISI 5120M. Batches of gears made out of these three materials using the same finishing process at about the same roughness and hardness levels were used in these tests. Each specimen was qualified for its dimensional accuracy, hardness and surface roughness amplitudes before being tested on standard, FZG type, four-square test machines according to well-defined procedures and failure criteria. Interim inspections throughout each test were used to describe the mechanisms leading to pitting failures. The pitting data obtained for each gear material were tabulated and analyzed statistically whenever possible. The pitting fatigue life results of ground gears made of these materials were compared to each other as well as to baseline shaved gear and super-finished gear data obtained in previous related studies. The results indicated that hard grinding gears increases the pitting life of spur gears substantially in comparison to a baseline of shaved gears. Ground gears were also shown to provide improvements in the same order as super-finished gears.

Committee: Ahmet Kahraman PhD (Advisor); Donald Houser PhD (Committee Member) Subjects: Mechanical Engineering

Master of Science, The Ohio State University, 2009, Mechanical Engineering

This study consists of experimental studies involving two modes of gear contact fatigue failure: gear pitting (spalling) and gear scuffing. For pitting studies, several materials and surface treatments were investigated at various stress levels. These surface treatments included (i) hobbed and shaved (baseline), (ii) chemically polished, (iii) shot peened and plastic honed, and (iv) ground gears. Pitting fatigue lives of chemically polished gears were greater than those of baseline specimens. Both shot peened and plastic honed gears and ground gears were shown to have greater pitting fatigue lives than baseline gears. The improved pitting fatigue life of ground gears over baseline gears appears related to the improved involute profile shapes of the specimens.For gear scuffing experiments, the standard ISO 14635-1 FZG Scuffing Test was performed on AISI 8620 type A spur gears. These experiments included four uncoated gear pairs and one gear pair coated with an experimental PVD coating. Uncoated gears encountered scuffing during Stages 11 and 12. A high correlation between temperature and scuffing results was detected for both coated and uncoated specimens.

Committee: Ahmet Kahraman PhD (Advisor); Donald Houser PhD (Committee Member) Subjects: Mechanical Engineering