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.
Fracture mechanism of polycrystalline cubic boron nitride abrasive grains during single-grain grinding of Ti-6Al-4V titanium alloy
In this article, high-speed grinding experiments were carried out on Ti-6Al-4V titanium alloy material to investigate the fracture mechanism of polycrystalline cubic boron nitride abrasive grains. The experiments were based on single-grain grinding operation to compare the fracture behavior of polycrystalline cubic boron nitride abrasive grains and monocrystalline counterparts. Considering that the fracture behavior of abrasive grains was influenced by load; moreover, the load was related to grinding depth, and more experiments were conducted to study the effects of grinding depth on the fracture behavior of abrasive grains. In order to observe the fracture behavior, photographs were grasped with 3D optical video microscope and the 3D profile of grain topography was reconstructed. The results obtained indicate that polycrystalline cubic boron nitride abrasive grains are generally more suitable to manufacture the brazed grinding wheels. Due to the particular microstructure, polycrystalline cubic boron nitride abrasive grains are more prone to micro fracture and attritious wear instead of large fracture. Furthermore, the polycrystalline cubic boron nitride abrasive grains usually get worn more seriously with a larger grinding depth.
Lupin alkaloids from teratogenic and nonteratogenic lupins. II. Identification of the major alkaloids by tandem gas chromatography-mass spectrometry in plants producing crooked calf disease.
The major alkaloids of lupin plants producing crooked calf disease were identified by tandem gas chromatography-mass spectrometry and infrared analysis. The gas chromatography peak invariably present in teratogenic plants proved to be anagyrine. A minor but irregular contaminant of the peak was α-isolupanine. Other alkaloids present but apparently not associated with crooked calf disease were lupanine and two others that were probably epimethoxylupanine and 5,6-dehydrolupanine.