Experimental studies on gear-honing-tool with laser brazing film CBN
During the process of brazing cubic boron nitride (CBN) gear-honing-tool by Laser, cleaning of the gear-honing-tool and film plating CBN abrasive, and the thickness of brazing coating directly affect the quality and life of gear-honing-tool. In the paper, based on experiment the process of laser brazing CBN is summed up, the thickness interrelationship of brazing filler metal from beginning to end is obtained, the rule of laser facula's moving speed is studied on solder layer thickness and the radial change of gear tooth thickness. It is shown that the bonding among CBN, gear-honing-tool and solder can be realized by laser brazing. In order to improve quality of brazing, the moving speed of laser facula must be reduced along radial direction of gear honing tool. As to different size of CBN abrasive, the thickness of solder layer should be varied so that the bare rates of cutting edge can be ensured. The solder layer thickness should be controlled between 1.25 and 1.5 times of average size of abrasive grains. The thickness of solder layer depends on laser energy and soldering time that can be controlled by the moving speed of laser facula.
Brazed CBN Grinding Wheel with Ag-Base Filler Alloy
In this paper, the disadvantages of the current CBN (Cubic Boron Nitride) grinding wheels were firstly introduced briefly, for indicating that it was very urgent and important to develop new kinds of grinding wheels with excellent performance to replace the conventional wheels. Then high temperature brazing experiments of monolayer CBN wheels with Ag-Cu-Ti filler alloy were carried out. The result shows that the filler alloy has good wetting capability towards CBN grits. The results of scanning electron microscope (SEM) and energy dispersion spectrometer (EDS), as well X-ray diffraction (XRD) analysis show that, just because during brazing titanium atoms in filler alloys segregated preferentially to the surface of the CBN to form Ti-nitride or Ti-boride layer by reaction between titanium atoms and nitride and boron atoms at elevated temperature, strong chemical joining was formed in the interface between CBN grits and filler alloys. Finally, the contrastive grinding experiments were performed between the monolayer brazed CBN grinding wheels and the electroplated ones. The results show that the brazed wheels have more excellent performance than the latter.
Prediction of Muscular Endurance (Work Performance) From Individual Differences in Initial and Post Training Increments in Static Strength
Forty college men were given tests for static strength and strength endurance prior to an isotonic strength training program. Experimental results indicate that individual differences in static strength are a poor criterion in the prediction of muscular endurance. Following an increase in static strength resulting from isotonic strength training pre-training static strength and post-training strength increments are not indicative of an individual's performance in a hand grip endurance activity.