GOALI: Fundamental Investigation of Constrained Cutting for High Performance Machining of Difficult-to-Cut Materials

Oregon State University, Corvallis OR

Investigators

Abstract

This Grant Opportunity for Academic Liaison with Industry (GOALI) award supports fundamental research on a novel metal cutting method for enhancing the efficiency of machining difficult-to-cut materials. Difficult-to-cut materials have poor machinability in typical machining conditions requiring higher cutting forces, and resulting in higher temperatures, shorter tool life, and poor surface finish. These cutting difficulties are fundamentally attributed to the difficult chip formation characteristics of difficult-to-cut materials and the lack of conventional cutting’s ability to control chip formation. The new cutting method uses a constraining tool in addition to a cutting tool to enable direct control of chip formation during the cutting process. This allows the chip formation characteristics to be optimized, which leads to efficient material removal with lower cutting forces, resulting in longer tool-life, improved surface integrity, and higher material removal rates. The constrained cutting method significantly benefits U.S. manufacturing industries, such as automotive, aerospace and energy, where difficult-to-cut materials are heavily used. Close collaboration with a partner from the U.S. cutting tool industry ensures technology transfer to develop next generation cutting tools and machining strategies. The project generates a well-trained workforce for advanced manufacturing and engineering through the involvement of graduate and under-graduate students, particularly, women and under-represented minorities, in research and education. The research focus of this project is to investigate how geometrically constraining the shear deformation zone affects the mechanics, dynamics, and generated surface integrity of machining processes. Conventional metal cutting processes lack direct control of chip formation. Controlling the shear deformation zone by an additional constraining tool can lead to reduced cutting effort, dramatically improved surface integrity and machining stability. Chip deformation during constrained cutting is analyzed experimentally through in-situ digital imaging and by analytical and computational modelling to understand the fundamental relationship between constraining parameters (location and geometry) and cutting effort (force, energy, and temperature). Constraining the shear deformation zone reduces plastic deformation and thermomechanical loads. This improves surface finish, enhances microstructure, and reduces residual stress. Experimental characterization and correlation with deformation and temperature analysis generate the new knowledge to enable better control of the integrity of the generated surfaces. The effect of constraining tool on the coupled dynamics of the process and the machining equipment is also investigated, which leads to new designs of constraining tool geometries to control and suppress high-frequency self-excited chatter instabilities during machining. This allows machining of precision parts at significantly higher depth, feed and speed leading to greater material removal rates and superior surface finish. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.