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A fracture study of a connecting rod from a refrigeration compressor
Análisis de la fractura de una biela de compresor de refrigeración
DOI:
https://doi.org/10.15446/ing.investig.v30n1.15221Keywords:
connecting rod, compressor, lubrication, wear, friction coefficient (en)biela, compresor, lubricación, desgaste, coeficiente de fricción (es)
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This paper analysed the fracture of a connecting rod from a food product refrigeration compressor. According to the connecting rod-crank mechanisms operating characteristics, the element being studied was subjected to variable load cycles. Connecting rod loads are compressive in normal operating conditions; however, an increased friction coefficient induces flexion load. Based on the connecting rods microstructures, fracture surface characterisation and stress state estimation, it was concluded that the failure originated in a breakdown of connecting rod-crankshaft lubrication causing scuffing, severe wear and a high friction coefficient. Likewise, the results showed that when the friction coefficient increased to 0.4, then stress reached levels above those acceptable for the connecting rod material (molten aluminium-silicon alloy) being considered. Manufacture defects, pores and cracks increased stress concentration, thereby contributing to the mechanical elements failure.
En este artículo se analiza la fractura de una biela de compresor de refrigeración usado en la industria de productos alimenticios. De acuerdo con las características de funcionamiento del mecanismo biela-manivela, la pieza estudiada se encuentra sometida a ciclos de carga variable; en funcionamiento normal las cargas sobre la biela son compresivas pero el aumento del coeficiente de fricción induce cargas de flexión. Con base en análisis metalográfico y fractográfico, y la estimación del estado de esfuerzos de la biela, se concluyó que la causa de la falla fue la perdida de lubricación en el par biela-cigüeñal, que produjo: scuffing, desgaste severo y aumento del coeficiente de fricción. De la misma forma, los resultados mostraron que cuando el coeficiente de fricción se incrementa a valores límites como 0,4 los esfuerzos alcanzan valores muy por encima de los aceptables para el material de la biela (aleación aluminio-silicio fundida) en estudio. Los defectos de manufactura, poros y fisuras, aumentaron la concentración de esfuerzos, contribuyendo a la falla del elemento mecánico.
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Copyright (c) 2010 Ernesto Germán Porras, Sara Rodríguez Pulecio, John Jairo Coronado Marín
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