The effects of high-frequency vibration on the grinding process

Advanced ceramics are increasingly used in various engineering applications due to their superior performance. But ceramics are difficult to machine to a precise size and shape. This dissertation aims at developing a new machining process---vibration assisted grinding that is capable of achieving a high material removal rate while minimizing surface/subsurface damage to the machined ceramic parts. The various effects of high frequency vibration on grinding are investigated.; One effect of high frequency modulation parallel to the cutting direction is the softening effect. Modulation can result in a significant decrease in the static force necessary for plastic deformation of a material. The effect depends on the ratio of the modulation speed (product of the amplitude and frequency of the modulation) to the cutting speed.; Modulation can reduce the friction force between two sliding surfaces. The modulation may be applied in three axial directions in a Cartesian coordinate system. The direction in which the modulation is applied has an effect on the amount of friction reduction. In addition to direction, the amplitude and frequency of the modulation are important factors.; The effect of modulation on sub-surface damage was also investigated. Modulation perpendicular to the work surface or parallel to the cutting direction causes intermittent unloading. Intermittent unloading on a brittle material can produce a lateral crack before the median crack fully develops. Upon reloading, the lateral crack shields against further median crack penetration.; Experiments showed that modulation perpendicular to the work surface has an effect on the temperature and energy partition in the grinding process. Surface grinding experiments were carried out with 0 to 3 kHz vibrations on 4140 steel. Based on the observed temperature and force and a moving triangular heat source model, the strength of the heat source (entering the workpiece) and the energy partition (percentage of total energy that enters workpiece) are estimated. The experiments indicate that maximum temperature rise as well as energy partition to the workpiece decrease with increasing vibration frequency.; Finally, the effect of modulation on wheel self-dressing is investigated. The experimental results of single nib scratch tests give an indirect proof for this effect. Scratch tests with and without modulation are carried out. The tool wear rate with modulation is much higher than that without modulation. Microscope observation shows that the higher wear rate with modulation is due to chipping. The chipping comes from the impact between the nib and the workpiece due to modulation. (Abstract shortened by UMI.)...