Phenomenal Understanding on Drop Impact in Accidental Conditions

In drop tests, analyses and evaluations focused on deceleration. The measured deceleration data has so large noises that they have to be appropriate filtered. The simplified method is developed to dynamically estimate for decelerate at drop tests. This method uses easily measurable numerical information such as height of rebound of drop test or velocity gained by dynamic analysis. This method could reproduce drop impact behavior by only two parameters of “spring” and “damper”. In Other words, the spring and damper parameter are determined in order to reproduce the velocity gained by dynamic analyses or drop tests. This method has two advantages when two parameters of spring and damper are gained by several dynamic calculations or drop tests. Firstly, this method could support to determine filtering process parameter such as cut-off frequency. The deceleration after filtering process are dependent on cut-off frequency. According to advisory material for the IAEA regulations, the cut-off frequency of 100~200 Hz for a package with a mass of 100 tonnes is recommended as filtering process. However, it is determined by experience depending on packaging characteristics. Since the velocity after drop impact are integral result of deceleration, deceleration integrated by velocity in this method could be index of the appropriate cut-off frequency in order to obtain appropriate deceleration of dynamic analyses or drop tests. Secondly, this method could apply to oblique drop such as slap down and estimate to the most severe oblique drop angle at slap down. In order to estimate the most severe oblique drop angle, the conventional slap down study needs many cases of dynamic calculations using LS-DYNA with different oblique drop angles. However this method could estimate the velocity after first impact and the second impact velocity with wide range of angle condition using two parameters of “spring” and “damper” which are determined by several dynamic calculations. Since drop impact could be depends on the impact velocity, the most severe oblique drop angle could be estimated based on several dynamic calculations.