A fracture study of a connecting rod from a refrigeration compressor

Abstract

This paper analysed the fracture of a connecting rod from a food product refrigeration compressor. According to the connecting rod-crank mechanism’s 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 rod’s 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 coe- fficient. 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 element’s failure.

Keywords

• connecting rod
• compressor
• lubrication
• wear
• friction coefficient