Gear contact fatigue failure effects evaluation under process uncertainty influence.

• Autor(a) principal: Franco, Renato Ribeiro
• Data de Publicação: 2019
• Tipo de documento: Tese
• Idioma: eng
• Título da fonte: Biblioteca Digital de Teses e Dissertações da USP
• Texto Completo: http://www.teses.usp.br/teses/disponiveis/3/3151/tde-06012020-101923/
• topic: Análise de tensão; Confiabilidade; Engrenagens; Fadiga dos materiais; Falha por fadiga; Fatigue failure; Reliability; Stress analysis; Tensão dos materiais

Stress analysis has special importance on engineering activity due to its inherent intention of dimensioning components. Stress analysis has also a special importance on this research due to the intention of reproducing in a gear bench test, the amount of stress similar to the real stress distribution existing in a first gear present in a real gear box available in the market. In this research, ISO 6336 and AGMA standards were the guidelines for gear design, stress analysis and fatigue evaluation. According to those standards, gear geometry and material properties are key factors for fatigue failure evaluation, allowing the definition of the amount of cycles that the gear would face till fatigue failure. In this scenario, the main objective of this research is to evaluate gear fatigue failure experimental results based on ISO 6336 methodology, revealing the amount of damaged area after fatigue cycle. The thesis also discusses the manufacturing process uncertainty influence on such results. Based on reliability modeling analysis, which aims to point out differences induced by process errors. Thus, this research is based on analysis of five pinion gears experimental fatigue test output, according to ISO 6336 procedure aiming at defining gear fatigue damage. The experimental results show thirteen teeth damaged area for each one of the five gears. This represents an important contribution of this research once it defines the amount of damage resulted by fatigue cycle predicted at ISO 6336 within the boundaries defined on this research represented by gear geometry and test parameters including load, sliding speed, oil viscosity and temperature. Another important contribution of this research to gear designers is the evaluation of pitting gear damage area taking into account uncertainties associated with gear manufacturing process. This effort of evaluating process uncertainties aims to indicate process manufacturing control procedures that could contribute to reduce the amount of pitting damaged area during gear operational life. Finally, coating influence on final fatigue damaged area and its impact on reliability analysis were also researched, based on the same methodology used for fatigue testing of uncoated gears (ISO 6336). The output results point to a very promising new coating application to delay pitting occurrence during gear operational life.