Fractal Analysis of Grain Cutting Edge Wear in Superabrasive Grinding
This paper deals with a fractal analysis of the wear behavior of the grain cutting edges in superabrasive grinding. Fundamental overcut fly grinding experiments for producing individual straight grooves using a grinding tool with multiple grits are carried out to clarify the wear characteristics of the grain cutting edges in the grinding process and then the change in three-dimensional profile of the cutting edge measured with a multiprobe SEM is evaluated on the basis of fractal analysis. The main results are summarized as follows: (1) Fractal dimension for the contour line of the fine cutting edge formed by micro fracture shows a higher value than that of cutting edge formed by attritious wear or large fracture. (2) Fractal dimension for cBN grain cutting edge mainly formed by micro fracture tends to take a higher value than that for diamond grain cutting edge mainly formed by attritious wear. (3) The complex change in shape of the cutting edge with the progress of grinding process can be quantitatively evaluated by means of fractal analysis.
The Development of Nanocrystalline CBN for Enhanced Superalloy Grinding Performance
CBN grinding wheels are increasingly used on a wide range of engineering materials. This paper compares the grinding performance of monocrystalline (M-CBN) and polycrystalline (P-CBN) abrasives with a newly developed nanocrystalline (N-CBN) abrasive, when grinding nickel-based superalloys. The N-CBN grits possess average crystal grain diameters less than 1 μm compared to average primary grain diameters of 2.3 Aim for P-CBN. It was found that the nanocrystalline CBN grits possess higher fracture strength which give reduced wear rates and yield an order of magnitude increase in grinding wheel life. Analysis of the cutting edge distribution shows that the reduced wear rate of N-CBN is due to the predominance of a micro-fracturing mode of abrasive wear. The size of this micro-fracturing is considerably smaller in N-CBN than in P-CBN.
The Effect of Grinding Wheel Flexibility on Chatter
Summary In previous papers the benefits of a flexible grinding wheel have been demonstrated with respect to chatter suppression. A theoretical model of the process was developed and a digital simulation was used to show that the process either underwent an exponential growth or decay of vibration. The use of a digital simulation resulted in time constraints on investigating all the relevant parameters. In this paper a mathematical solution is presented with allows a more substantial investigation of all the parameters. The results confirm that the model adequately predicts the very slow growth rates often encountered in practice. Also it has been possible to show that the very slow precession rates of wheel waves around the circumference of the wheel may be predicted theoretically.