Riblet Rolling on Ti6Al4V Compressor Blades

Riblet structures on surfaces can reduce friction drag in turbulent flow. The optimal riblet geometry depends on the fluidic application. Fluid dynamic analyses have revealed that the application of riblets on compressor blades of jet engines promises to reduce fuel consumption and, thus, CO2 as well as nitrogen oxide emissions. Due to high operating temperatures the application of riblet films on compressor blades is not feasible. Alternatively, riblet structures can be manufactured directly on a metallic blade. Incremental riblet rolling is among possible manufacturing processes. This forming process has been designed at the Laboratory for Machine Tools and Production Engineering (WZL) of RWTH Aachen University. It goes along with a major advantage compared to riblet manufacturing by machining or laser structuring: Riblet rolling induces strain hardening and compressive residual stresses. These properties can almost fully compensate the reduced load capacity resulting from the notch effect which accompanies riblet structures.