Comparing bending fatigue and fretting fatigue properties in aluminum-silicon alloy under working conditions of engine piston-ring system

The fretting fatigue phenomenon in engine piston and ring parts, leads to the damage and the failure. In this study, fretting fatigue and bending fatigue behaviors in the piston aluminum-silicon alloy were compared. Then, the effect of the lubrication and the contact force was investigated on the fretting fatigue lifetime of the material. For this objective, fatigue tests were conducted in a fully-reversed loading condition at room temperature. For a better working condition, piston rings were used as fretting pads. The material fracture behavior was studied by the field emission scanning electron microscopy. Obtained results indicated that the fracture surface of the piston aluminum alloy was brittle; however, in some areas, semi-brittle fracture behavior was observed. Moreover, the fretting fatigue lifetime of the material decreased as 84 to 95%, compared to the bending fatigue lifetime. Applying the lubricant led to a significant increase of 43 to 75% of the fatigue lifetime. Using the oil and reducing the contact force from 20 to 10 N caused the 16-time improvement in the fretting fatigue lifetime of the quenched piston aluminum-silicon alloy, under 150 MPa of the stress level.