Abstract
The advent of direct injection turbocharged engines has increased the need for higher performance connecting rods, able to withstand higher compressive loads in operation. In this respect, the compressive yield strength of the materials used to manufacture connecting rods is of paramount significance as it becomes the most important design factor. Connecting rods are currently designed using mechanical properties obtained at room temperature; however, the operating environment in an engine can have negative effects on their performance, as the strength of most materials declines at higher temperatures. Nevertheless, tests conducted at engine operating temperatures have shown an improvement in mechanical properties of the materials used to manufacture powder-forged connecting rods as a result of copper precipitation strengthening. Scanning and transmission electron microscopy were employed to investigate nano precipitates of copper in the specimens tested at higher temperatures as well as in connecting rods that have been running in engines for appreciable amounts of time. In light of these results, there is an opportunity to reduce the cross section in the I-beam of powder-forged connecting rods by using in design the higher compressive yield strength values obtained at engine operating temperatures, thus resulting in mass savings.
