Evaluation of Cumulative Damage in a Series of Sequential Load Events

Abstract

During the safety assessments of transport packages, cumulative damages are naturally accumulated for assessments performed using physical tests specimens. However, such cumulative damages are not as easily accounted for when assessments are made through numerical simulations. While analysts are comfortable with simulating packages for single events, it is not yet common practice to incorporate the effect handed over from a former event to the next, in a series of sequential load events. Thus, many numerical simulations in a safety analysis report (SAR) represent just a single event in a series of sequential events comprising the required accident conditions. These single event numerical simulations are then based on the initial conditions that differ from the analogous physical test specimen, which could contribute to a growing disparity in the results between assessments through physical testing compared to a numerical simulation. The reason why analyses do not consider the cumulative damage is difficulties in delivering the final results of the previous analysis to the current analysis. The hypothetical accident conditions described in the International Atomic Energy Agency (IAEA) regulations include drop, puncture, fire, and water immersion conditions, which should be sequentially simulated. There can be cumulative damage between two accident conditions, such as drop and puncture, puncture and fire, and so forth. In this study, as the first step to consider cumulative damage, an analysis technology to perform a puncture analysis incorporating the final response field from a prior drop analysis is proposed. The necessity and validity of the proposed analysis technology are evaluated through a comparison with the results obtained by performing each analysis independently.