An analytic method for predicting the spectral character of vibrations generated by an important class of defects in ball bearings is described. This family of bearing problems comprises those operating modes in which the magnitude of the ball-race contact force varies continuously and periodically as the bearing rotates. Defects of this type include race misalignment and off-sized rolling elements. The analytic technique is based on solving Lagrangian equations for the time-varying displacement of the bearing race in response to the rotating system of ball forces.

This paper describes an electronic-mechanical system which utilizes sonic signals to detect the degree of cutting edge wear in metalworking tools and automatically trigger a cutting edge change. A packaged electronic unit reads out sonic vibrations from an instrumented machine-tool workpiece cutting-tool system to determine degree of cutting edge wear during a turning cut. At a predetermined comparative sonic ratio, the electronic unit commands stoppage of the machine tool feed, retraction of the tool and automatic index of the cemented carbide insert to the next good cutting edge. The latter function is performed by a prototype mechanical device. The paper describes the system and cites data generated during use of the sonic detection system with five grades of cemented carbide cutting AISI 1045 steel. Results under varying cutting conditions are reported. The authors speculate on the possibility of combining such a wear detection and cutting edge indexing arrangement with a computer to provide a complete system for optimum productivity and economy in a completely automatic operation.

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Three test chambers with volumes between 175 and 32 000 ft3 have been acoustically calibrated for air pressures from 760 down to 25 Torr. Such calibration presents special problems, since the normally used standard noise sources have an acoustic power output with a pressure dependence that is difficult to calculate. Therefore a special sound source was developed, using a stiff and heavy piston as radiator. This sound source, with known pressure characteristics, was used during all calibrations. Reverberation time was also measured in the chambers for all pressures. In the paper, results from the two independent calibration methods are compared to each other. The measured acoustic characteristics are also compared to theories for air damping, including effects from the humidity-dependent molecular damping. It is concluded that the chamber damping increases with decreasing chamber pressure for all tested frequencies (100–40 000 cps). At high frequencies, the measured chamber damping agrees well with the theoretically predicted air damping, thus showing that the wall damping is negligible. A general calibration curve—valid for various frequencies, air pressures, and chamber volumes—is presented.