Design Method of Power Spectrum Density Profile for Random Vibration Test Based upon S-N Curve

摘要

The susceptibility of the product against the vibration was studied at an actual transport condition to develop a random vibration test method. The validity of obtaining power spectrum density (PSD) and its design method were investigated by using a low cost three dimensional vibration data logger (interval recording type). The logger was subjected to the sinusoidal vibration in vertical direction. PSD data obtained by the data logger (equipped with software) gave a lesser level of power in the low frequency range provably due to the limitation of the resolution of frequency. Therefore, attention should be paid not only on the upper limit of the frequency based upon sampling theory but also on the lower limit to evaluate PSD by digital Fast FourierTransformation. A simple average of the PSD data will give a too little power level, whereas selection of the highest level PSD give an over power level to obtain PSD for the simulated transport test. However, it is possible to obtain a PSD data considering the damage susceptibility of the product by using the S-N curve. Moreover, an accelerated test, shortening of time for the vibration test than the actual transport is possible by using the S-N curve.