Investigation of cutting mechanisms in the ultrasonic-assisted cutting of fibre-reinforced non-oxide ceramics (CMCs) with geometrically defined cutting edge

 

Due to ever stricter environmental regulations and strongly increasing intra-industry competition, the current development program of engine manufacturers focuses primarily on the demand for increased efficiency. One solution is ceramic composite materials that increase the maximum permissible material temperature and thus increase the engine efficiency. However, CMCs regarding their high hardness and strong anisotropy are difficult to cut with conventional machining (unfavourable material removal, high tool wear, poor surface quality, etc.).

One possible innovative approach to improve the machinability of CMCs is the ultrasonic-assisted cutting. A high-frequency oscillating movement with frequencies above 16 kHz is superimposed on the actual tool movement. The advantages of this technology, when machining difficult-to-cut materials, are the reduction of process forces and changes in the sub surface zone of the workpiece as well as the improvement of the component quality. In addition, the temperature load is reduced by the periodically recurring tool-workpiece contact interruption, which extends the tool life. Furthermore, the influence of the cooling lubricant flushing effect is increased by the interruption of contact. However, there is currently no basic knowledge about the influence of tool vibration on the machining of CMCs with geometrically defined cutting edge.

The main goal of this DFG research project is the development of a design model for the ultrasonic-assisted cutting of CMCs. For this purpose, an ultrasonic unit should be integrated into a basic test bench for the orthogonal cutting in order to determine the influence of different cutting, vibration and tool geometry parameters on the chip formation, the process state variables force and temperature and the resulting workpiece surface properties (cause-effect relationships).