Análise de falha em redutores de rosca sem-fim: estudo de caso em uma coroa de bronze

Abstract

Failures in machinery and equipment can cause serious disruptions to work schedules, impacting company outcomes, reducing product quality delivered to the market, and increasing risks to operator safety. Proper maintenance and evaluation of speed reducers can reduce operation interruptions and the consequent cost of gear repair or replacement. Bronze gears are commonly used for internal gear applications in reducers and variable speed devices due to their lower coefficient of friction and good wear and fatigue properties. This study aimed to assess the failure of a bronze gear used in the speed reducer of an electric hoist. The analysis revealed that 100% of the teeth on the bronze gear were broken during operation, resulting in catastrophic equipment failure. To investigate the possible causes of the failure, visual analysis techniques, chemical composition analysis using X ray spectrometry, Brinell hardness measurements, metallography, and fractography were employed. The analyses showed that the material had lead quantities outside the allowable range for manufacturing the part, as well as casting voids and lead globule along grain boundaries. It was found that the lead globule exhibited significantly lower hardness compared to the matrix, and precipitation along inter dendritic boundaries made the alloy susceptible to intergranular fracture. It was concluded that all these factors synergistically contributed to the gear failure. To prevent failures like the one addressed in this study, it is recommended to ensure proper processing of the gear to obtain uniformity in microstructure, geometry, and bronze composition, and to implement an effective maintenance plan with periodic inspections to detect abnormalities in advance and prevent material losses, equipment downtime, productivity losses, and potential hazards.