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Statistical Analysis of Mechanical‐Shock Fragility Test Results

The mechanical‐shock fragility testing methods applied to packaging and product designs according to Japan Industrial Standards Z 0119:2002 incur some problems related to statistical analysis. One such problem is that the applied shock levels are increased in steps. We cannot determine the true fragility values for each sample. This is called interval‐censored data. If the maximum level of non‐damaging shock is selected for each sample, the calculated average will be too small. Another problem is that the number of shocks is limited to a maximum of 5 or 6, so as to minimize the effect of the accumulated fatigue. Therefore, if we determine the considerably high first shock level, initial‐censored data are obtained by the failure of the product when subjected to the planned first shock. If we determine the considerably low final shock level, final‐censored data are obtained when the product has not been damaged by the application of the planned final shock. These problems make statistical analysis difficult. We therefore propose an improved analysis method for data including interval‐censored, initial‐censored, and final‐censored data, and provide examples in which the method is applied to the results of a drop test. The results of the examples show that the proposed method is practical and that the censored data yields errors and loss of accuracy for the statistics. Finally, by means of a comparison between the staircase method of ISO 7765‐1:1988 and the method of JIS Z 0119:2002, we analyse the advantages and disadvantages of the respective methods. Copyright © 2017 John Wiley & Sons, Ltd.