It is the major failure mode of high-cycle fatigue for rotating mirror. Test methods for fatigue are commonly used
in researching the fatigue life of rotating mirror, but not practically. In this paper, numerical analysis and experimental
were used for researching the fatigue life of rotating mirror. With the finite element analysis software ANSYS, a static
strength about the rotating mirror was calculated at first and the results of stress from computing were imported into the
nSoft as the cyclic stress load spectrum for analyzing the fatigue life of rotating mirror. According to the S-N curve of
rotating mirror which defined by the material properties, the Miner linear cumulative damage law and the Goodman
Mean Stress Correction Model, the fatigue life of rotating mirror was calculated by nSoft. It shows that the fatigue
failure of rotating mirror does not occur under the speed of 3x104 rpm, because no node is damaged within the threshold
of infinite numerical cycles in that speed. Then a fatigue life experiment was done. 10 specimens of rotating mirrors
worked for 360 minutes respectively in the speed of 3x104 rpm on the bench of the rotating mirror test system. The
cycle index of stress was more than one million times, and no fatigue failure was occurred for every last sample. The
results from the numerical are in accord with that from experimental analysis. It is high accurate to analyze the fatigue
life of the rotating mirror by the method of numerical analysis.
KEYWORDS: Mirrors, Numerical analysis, Cameras, Statistical analysis, Lithium, Analytical research, Monte Carlo methods, Modal analysis, Data modeling, Sun
The numerical analysis and experiment about dynamic sensitivity of rotating mirror were done to verify the
influence of the structural dimensions of rotating mirror on the natural frequency. Firstly, the model of dynamic
sensitivity of rotating mirror was established by the ANSYS Parameter Design Language, then the dynamic sensitivity
analysis of rotating mirror was done based on the Monte Carlo method and the Latin Hypercube Sampling Technique.
The result shows that the spearman rank correlation coefficient of basic variables is different from each other, which
reveals that the variables impact the natural frequency in different ways. The radius of rotating mirror body R5 and the
radius of shaft segment R2affect mostly the natural frequency among these variables, and the length of the shaft
segment L1 affects hardly the natural frequency of rotating mirror. R5 and R2 influence the same natural frequency in
opposite way. With the single variable principle, the experiments for dynamic sensitivity were done to examine the
results of numerical simulation. The results show that the R5 of rotating mirror increase by 4% which cause the first
natural frequency value decreasing from 466.3 to 426.6 Hz. However, when the length of L1 of rotating mirror reduces
about 10% the amplitude-frequency response curve of rotating mirror is almost unchanged. The results of experiment
are good agree with the numerical analysis show that the numerical analysis is a high accurate method to optimize the
structural size of rotating mirror for avoiding the influence of resonance.
A novel measuring implementation based on second-harmonic generation frequency-resolved optical gating (SHG-FROG) has been presented. Both the intensity and phase of arbitrary-shaped ultra-short laser pulses can be got. According to SHG-FROG, the femtosecond pulse produced by a laser resource is split into two beams which variable time delay one another is controlled by a stepped electromotor. The second-harmonic signal field is generated by focusing these two beams to a 100um BBO crystal. Changing the delay from 0 to N (N is the samples number of time domain or frequency domain) delay units, the two-dimensional spectrum data of the second-harmonic signal field are acquired by PC2000-ISA card spectrometer and OOIwinIP of Ocean Optics. These data are provided to a pulse amplitude and phase retrieval algorithm to retrieve the parameters of the pulse. An experimental system is erected and the all software modules, including spectrum data acquiring, pulse retrieving and displaying, are based on Labwindows/CVI of National Instrument Corp. The stepped electromotor is driven by the commands coming from RS-232 interface. The results show that after 50 times iterations or so, the iterative error of the algorithm can be reduced to an enough small value and then the pulse amplitude, phase and other parameters are the desired parameters. The whole measuring process can be finished in 2~3 seconds while the spectrum data is a 64x64 matrix and the iterative times are set to 50.
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