ABSTRACT
As large-scale rotating machines develop toward high rotating speed and high power-weight ratio, skidding damage has become one of the major initial failure modes of cylindrical roller bearings. Therefore, understanding the skidding damage law is an effective way to ensure the safety of machines supported by cylindrical roller bearings. To realize the skidding damage, a high-speed rolling bearing test rig that can simulate the actual operating conditions of aviation bearings was used in this paper, and the skidding damage dynamic behaviors of cylindrical roller bearings were investigated. In addition, to ensure the accuracy of the obtained skidding damage mechanism, the cylindrical roller bearing was carefully inspected by microscopic analysis when the skidding damage occurred. Out results show that instantaneous increases in friction torque, vibration acceleration, and temperature are clearly observed when the skidding damage occurs in the cylindrical roller bearing. Furthermore, under the conditions of inadequate lubrication and light load, the critical speed of skidding damage is rather low. The major wear mechanisms of skidding damage include oxidation wear, abrasive wear, and delamination wear. The white layers are found locally in the inner ring and rollers under the actions of friction heat and shear force.
ABSTRACT
A compact continuous-wave blue laser has been demonstrated by direct frequency doubling of a laser diode with a periodically poled lithium niobate (PPLN) waveguide crystal. The optimum PPLN temperature is near 28 degrees C, and the dependence of waveguide crystals on crystal temperature is less sensitive than that of bulk crystals. A total of 14.8 mW of 488-nm laser power has been achieved.
ABSTRACT
Charge-coupled device (CCD) has been widely used in spectral detection and spectral imaging fields, which has a number of benefits: broad spectral range response, low detection limit, wide dynamic range, minimal dark current and readout noise as well as the abilities of signal integration, simultaneous multichannel detection, and real-time detection. The combination of a traditional one meter grating spectrograph and a science charge-coupled device (CCD) led to a real-time grating spectrograph for laser spectrum detection developed in this paper. Based on the new grating spectrograph, the spectral characteristic of frequency-doubling of a broad band double-cladding fiber laser in polarized lithium niobate (PPLN) has been investigated. Dynamic spectrum of the second harmonic with varying temperature of PPLN has been observed and analyzed in detail.
