Developing a novel radial ultrasonic vibration-assisted grinding device and evaluating its performance in machining PTMCs

Abstract

Particle-reinforcing titanium matrix composites (PTMCs) exhibit the sharp raising applications in modern industries owing to its extraordinary physical and mechanical properties. However, the poor grindability and unstable grinding processes due to the existence of TiC particles and TiB short fibres inside PTMCs, leading to the sudden grinding burn and low material removal rate. In this work, a novel radial ultrasonic vibration-assisted grinding (RUVAG) device with a special cross structure was developed to improve machining efficiency and avoid grinding burns. Meanwhile, the resonant modal and transient dynamic characteristics of radial ultrasonic vibration system were discussed. Comparative grinding performance experiments were then conducted under the conventional grinding (CG) and RUVAG using mono-layer cubic boron nitride abrasive wheels, in views of the grinding forces and force ratio, grinding temperature, and ground surface morphology. Results show that the ultrasonic vibration direction can be transformed effectively using the special cross structure of vibration converter, and better vibration homogeneity can be obtained. RUVAG has a smaller tangential grinding force by 5.0%–17.2% than that of CG, but a higher normal grinding force of 6.5%–14.9%, owing to the periodic impact of grinding wheels. In addition, RUVAG possesses a remarkable lower grinding temperature in range of 24.2%–51.8% and a higher material removal rate by 2.8 times compared with CG, resulting from the intermittent cutting behavior between the grinding wheel and workpiece. In this case, the sudden burn can be avoided during high-speed grinding processes. Moreover, the proportion of micro-fracture defects on machined surface is slightly increased once the ultrasonic vibration mode is employed because of the periodic impact on reinforced particles, whereas the pull-out defects of reinforced particles are reduced significantly.